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Home My WebLink About20212338.tiffUSE BY SPECIAL REVIEW (USR) APPLICATION FOR PLANNING DEPARTMENT USE: AMOUNT $ APPLICATION RECEIVED BY DATE RECEIVED: CASE # ASSIGNED: PLANNER ASSIGNED: PROPERTY INFORMATION ■ r Is the property currently in violation? No / Yes Violation Case Number: Parcel Number: 1 2 0 9 Site Address: 9290 County Road 34 1 5- 2 - 0 0 _ 0 3 6 Legal Description: PT NW4 15-3-67 LOT C REC EXEMPT RE -3621 EXC UPRR RES (4.01R) Section: 15 , Township 3 N, Range 67 W Zoning District: AG Within subdivision or townsite? ai No I Yes Name: Acreage: 152.607 Water (well permit # or water district tap #): Sewer (On -site wastewater treatment system permit # or sewer account #): Floodplain D No / Yes Geological Hazard r No I Yes Airport Overlay n No /nYes PROJ ECT USR Use being applied for: Name of proposed business: St gain USR Amendment PROPERTY OWNER(S) (Attach additional sheets if necessary.) N ame: Anadarko E & P Company LP Company: Anadarko E & P Company Phone #: Email: Street Address: 1099 18th St City/State/Zip Code: Denver/CO/80202 APPLICANT/AUTHORIZED AGENT (Authorization Form must be included if there is an Authorized Agent) N ame: David Van der Vieren Company: Kerr-McGee Gathering LLC / Western Midstream P hone #: 720-929-3812 Email: david.vandervieren@westernmidstream.com Street Address: 1099 18th St City/State/Zip Code: Denver/CO/80202 I (We) hereby depose and state under penalties of perjury that all statements, proposals, and/or plans submitted with or contained within the application are true and correct to the best of my (our) knowledge. All fee owners of the property must sign this application. If an Authorized Agent signs, an Authorization Form signed by all fee owners must be included with the application. If the fee owner is a corporation, evidence must be included indicating the signatory has the legal authority to sign f the corpojtion. 5/6/21 Signature Date David Van der Vieren Signature Date Print Print DEPARTMENT OF PLANNING AND BUILDING DEPARTMENT OF PUBLIC HEALTH AND ENVIRONNMENT 1555 NORTH 17TH AVENUE G RE E LE Y, CO 80631 AUTHORIZATION FORM I, Lauren Anderson, Land Director, give permission to Sam Samet, Tracy Coiling, Shayelyn Coppinger, Samantha Petite, Jayson VanShura, Callie Lewis, David Van der Vieren, and Aileen Yeung to apply for any Planning, Building or Septic permits on behalf of, and relating to, properties owned or operated by Anadarko E&P Onshore LLC, Kerr McGee Gathering LLC, Anadarko Wattenberg Oil Complex LLC, Kerr McGee Oil & Gas Oil Onshore LP, Property Owners Information: Phone: Lauren Anderson (720) 929-6701 Authorized Agent Contact Information: Phone: Sam Samet - (720) 929-3317 Phone: Tracy Coiling - (720) 929-6160 Phone: Shayelyn Coppinger - (720) 929-6907 Phone: Samantha Petite - (720) 929-3167 Phone: Jayson VanShura - (720) 929-6814 Phone: Callie Lewis - (970) 515-1527 Phone: David Van der Vieren - (720) 929-3812 Phone: Aileen Yeung - (720) 929-3496 E-mail: Lauren anderson@oxy.com E -Mail: samsamet@oxy.com E -Mail: tracy tolling@oxy.com E -Mail: shayelyn coppingeroxy.com E -Mail: samantha petite@oxy.com E -Mail: jaysonvanshura@oxy.com E -Mail: callielewis@oxy.com E -Mail: david vandervieren@oxy.com E -Mail: aileen yeung@oxy.com Correspondence to be sent to: Owner Authorized Agent Additional Info: Owner Signature: Both l by Mail Email Date: l‘ 1.'hs hat Date: ANADARKO OGC COMPANY POWER OF ATTORNEY Effective Date: August 8, 2019 The undersigned, Anadarko OGC Company, a Delaware corporation ("Company"), hereby constitutes and appoints each of Robbie Abraham, Lauren E. Anderson, Michael Avery. Peter J. Bennett, Barbara M. Bergersen, Babatunde Cole, Matt C. Cotter, Austin H. Danford, Devin Dansby, Bradley S. Dusek, Gerald T. Herrington, Jean Hinton, William C. Irons, Richard A. Jackson, Lindsay N. Jaffee, Thomas A. Janiszewski, Joseph D. Johnson, Sally McElroy, Tiffany L. McGuire, Kelly A. Montgomery, Rebecca L. Morris, Wesley Robertson, John V. Schneider, Michael P. Ike and David J. Woest, acting individually, as a true and lawful Attorney -in -Fact of the Company (collectively, the "Attorneys -in -Fact"), for it and in its name, place and stead, to take the actions described below, on behalf and for the exclusive benefit of the Company. (1) Execute, acknowledge and deliver any agreements pooling royalty on any or all minerals of this Company under oil, gas and/or other mineral leases with royalty on any or all minerals under oil, gas and/or other mineral leases of third parties; (2) Execute, acknowledge and deliver any agreements pooling oil, gas and/or other mineral leases and the rights thereunder of this Company with oil, gas and/or other mineral leases or minerals and rights thereunder of third parties; (3) Execute, acknowledge and deliver any agreements providing for the joint or unit development of oil, gas and/or other mineral leases or minerals of this Company with oil, gas and/or other mineral leases or minerals of third parties; (4) Execute, acknowledge and deliver any agreements pooling unleased interests in minerals of this Company with unleased mineral rights and/or rights in oil, gas and/or other mineral leases of third parties; (5) Execute, acknowledge and deliver any agreements pledging contributions to third parties in connection with the drilling of wells; (6) Execute, acknowledge and deliver any agreements subordinating oil, gas and/or other mineral leases or minerals and the rights thereunder of this Company to the rights of third parties; (7) Execute, acknowledge and deliver any agreements for the purchase, or exchange, of minerals or oil, gas and/or other mineral leases or interests in minerals or oil, gas and/or other mineral leases and assignments, leases or deeds pursuant thereto; (8) Execute, acknowledge and deliver any agreements for the sale, lease or assignment of minerals and/or oil, gas and/or other mineral leases and the necessary instruments pursuant thereto; (9) Execute, acknowledge and deliver any agreements for the renting, leasing, licensing, permitting, purchase and/or sale of real property and/or personal property and the necessary instruments pursuant thereto; (10) Execute, acknowledge and deliver any division orders and transfer orders covering sale of oil, gas and/or other minerals; (11) Execute, acknowledge and deliver any agreements for geological and geophysical explorationwork and any other agreements for test well drilling, and any and all other agreements of a functional nature pertaining to the acquisition, exploration, testing, development, and operation of oil, gas and/or other mineral properties; (12) Execute, acknowledge and deliver any easements, rights -of -way, servitudes, licenses and permits on lands owned by this Company; (13) Execute, acknowledge and deliver any oil, gas and/or other mineral leases on fee lands and on mineral rights in lands of this Company wherever situated; (14) Execute, acknowledge and deliver any oil, gas and/or other mineral leases on lands of members of any Tribe of Indians and/or lands of Natives, on mineral interests of any Indian Tribe and/or Native corporation, company, or organization, on public lands and other lands of the United States of America wherever situated, on public lands and other lands of any State and of any subdivision of any State wherever situated, in which this Company is lessee; (15) Execute, acknowledge and deliver any oil, gas and/or other mineral leases on any land or mineral interest regardless of ownership wherever situated, in which this Company is lessee; (16) Execute, acknowledge and deliver any agreements for the sale of mineral producing properties, oil, gas and/or other mineral leases, and other mineral interests owned by this Company; (17) Execute, acknowledge and deliver any assignments, transfers, conveyances, deeds, oil, gas and/or other mineral leases, bills of sale and other instruments in connection with sales of leases, wells and related facilities and/or installations, together with personal property in, on and/or sewing the properties sold; (18) Execute, acknowledge and deliver any bids, applications and filings for oil, gas and/or other mineral leases on lands of the United States of America and any State owned lands, including such lands embraced within the area called "the Outer Continental Shelf', on lands of any Indian Tribe, on Sands of any Native corporation, company or organization; (19) Execute, acknowledge and deliver any leases of the surface of lands wherever situated of this Company for agricultural grazing and other purposes; (20) Execute, acknowledge and deliver any subleases of rights under surface leases and under oil, gas and/or other mineral leases of this Company; (21) Execute, acknowledge and deliver any releases and surrenders of leases, oil, gas and/or other mineral leases and easements in real estate wherever situated; (22) Execute, acknowledge and deliver any agreements for consulting services and/or other personal services; (23) Execute, acknowledge and deliver any saltwater disposal agreements and right-of-way agreements and agreements for construction of facilities necessary for the functional operation thereof; (24) Execute, acknowledge and deliver any development contracts, unit agreements and other agreements relating thereto with the federal, state and local governments and the various departments, agencies and branches thereof; (25) Execute, acknowledge and deliver any assignments and/or partial assignments of oil, gas and/or other mineral leases covering federal, state or other lands; (26) Execute, acknowledge and deliver any assignments of operating rights and designations of operator under oil, gas and/or other mineral leases covering federal, state or other lands; (27) Execute, acknowledge and deliver any indemnity agreements; settlement agreements; bonds and security agreements; farmout and farmin agreements; dry and/or bottom hole contribution agreements; drilling contracts; alliance agreements; pipeline/plant/facility construction, installation, operation and/or service agreements; participation agreements; exploration agreements; broker agreements; surface, mineral and royalty deeds; instruments pertaining to overriding royalty interests; wellbore assignments; term assignments; labor and employment contracts; affidavits; unitization agreements; joint operating agreements; area of mutual interest agreements; (28) Execute, acknowledge and deliver any and all other agreements and instruments related or pertaining to the oil, gas and mineral exploration and production business of this Company; and (29) Execute, acknowledge and deliver any amendments, modifications, supplements, releases, renewals, extensions, cancellations, assignments and transfers of and pertaining to any of the instruments herein set forth. 3 Said Attorneys -in -Fact are hereby granted full and complete power and authority to execute, acknowledge and deliver such other documents and instruments and to do such things and perform such acts as may be necessary or convenient in connection with the foregoing. The Company hereby declares that each and every act, matter and thing which shall be given, made and done by the said Attorneys -in -Fact in connection with the exercise of any or all of the aforesaid powers shall be as good, valid and effectual for all intents and purposes as if the same has been given, made and done by the Company, in its corporate presence, and the Company hereby approves, ratifies and confirms whatsoever said Attorneys -in -Fact, or any of them, shall lawfully do or cause to be done within the authority conferred by the foregoing powers as the authorized acts and deeds of the Company. This Power of Attorney, shall be effective as of the Effective Date provided above and shall remain in full force and effect until duly revoked, in whole or in part, by the Company. [signature page follows] 4 IN WITNESS WHEREOF, the Company has executed this Power of Attorney as of the date first written above. ANADARKO OGC 0MPANY B. Name: Nicole E. Clark Title: Vice President USE BY SPECIAL REVIEW MAJOR AMENDMENT QUESTIONNAIRE ROPOSED CHANGE TO THE ST. VRAIN COMPRESSOR STATION Western Midstream Page 12 VICINITY MAP ..,....,4.*.,40P..4 „ 04*4040*4444 QUESTIONNAIRE ,0404,44♦ Western Midstream.com TABLE OF CONTENTS 44444044 4.444,44 1. Proposed use and business name, 2. Need for the proposed use 3. Use of the land.. *ii$040*4444 4. Proximity to residences.,....,. D..4.0 5. Surrounding land uses 44.444444444 44444,4* - *44404** 04*444,*4 ►444+4+44 04*444,*4 ►444+4+ *0044400*444,*►444+4+ - •4*444440 04440444404* - •**404 F*444 M4M ••.. *44440*,44, ••.. *44440*4444 4,404,444 *44,4,44 44444444 *4.4444.4444 4.444,4* - *4*4444* - O 4*404444 O 4,4444* 5 .....5 *44444.4►444 F. 5 •4*444 4* 6 • !nil 446 ■4..444.64444644446.44,4646 ,44464 i 4464. 444... 444444 444444 ,*4... 444444 848446 ,44464 i 4464.44444.4444.*4,...4,4...444...*446.44,4646 ,44464 i 4464. 444... 444... 44 6. Hours and days of operation 44444 444444 444664 404644 004464 44644 444444 444446 7. Number of employees 44.4444..4444644446664444444.4646.4444444464444444.4444.6444466 S 414641 4104446 004464 SO4644 444444 444444 444664 404644 004464 444644 444444 444446 44 S SIO 644 4104446 004464 SO464 SOO 644 444444 444444 404444 44446S 444444 SSSS 44 004464 SOO 644 SOO 444 444446 44 8. Maximum number of users .............4.4...4.4..........44.44444.4.444...444...44....444...444...444..444...444.4444444.444...444...444...444...4.4.46.44...444.44444.4.444...44 9. Animals 4444... ..i 444644 044444 4444.4 4414444 404446 004464 SOO 644 044444 44444 444444 44466444444644446444464444444.4444.4 4414444 404446 004464 444644 044444 444444 OS 10. !Equipment. 4 4...004 ..' 11. Structures 8 12. Size of stockpile, storage or waste areas. 8 13. Method and time schedule of removal or disposal of debris, junk, wastes. 14. Construction. 4000 *,.,44... ... g 15. Lot surface type 444044 O 444044 O 10 16. Parking spaces 444644WOO 444,644 4.,6 10 1_7. Fencing44ISIS 444.6444,64.444644WOO 44.4444 44 4.,6 10 18. Landscaping. .4.44404.4.4444..44444.4446.644446444464444..!444...44444..*4.4.4444..444444444..4444.44444,44444.4.4404.4.04.4.4444..44444.444..6444464 19. ReclamationWell 444.6444,6.444444 4.4446.4444,66444.44 0Well 444444 10 20. Fire protection measures. ,,,, 11 21. Consistency with Weld County Comprehensive Plan per Chapter 22 11 22. Consistency with the intent of the zone district,., 23 Compatibility with uture development .4,++.,,, *+.,,12 24. Impacts., 12 25. Irrigation features B1,5 OO 12 13 404444 044449 26. Compliance with Article V and Article XI of Chapter 23. *.4.4.46 27. State or Federal permits required. SS 4.4,....44.6 4.4...4.4.64.4464.4..... 13 Environmental Health Questions:...14 1. Drinking water source. 14 2. Sewage disposal system.....-.*.044***444*0444, ***444***444...04...044***444*0+444 - - - - *40444.0*444.*4444+4*444+0+444 -444 - **F.,, 14 4444 t 4446.4 1 44444 _.._ _. _ **444, 1.2 3. Storage . .*4*.+444...4 - *..444..4.44.**444**0444*++4440*+ .i4*40,0, -:.04...4,4.4044,..+444 4. Storage and/or stockpile of wastes, chemicals, and/or petroleum *+444*.44,4 - - - - 1201 Lake Robbins Drive *+0444.0*4440**444**0444*0+4440++ -404+00404 4+0444+004440..44.**444*40444*0+44404+ The Woodlands, Texas 77380 444,40444 14 14 Western Midstream Page 13 Western Midstream.com 5. Fuel storage ,....,., .,., 15 6. Washing of vehicles,,,..,,, 15 7. Floor drains.•,....,,..r,,,•r,,,r,,,,,,,,,,,,,,,, s,,,•..,,,...,,,...,,,....,,...,,,,.,,,,.,,„,,,s,,,.s.,,, 15 8. Air emissions,,,,,,,,,,,,, 15 9. Design and operations plan 15 10. Nuisance management play 1 Public Works Questions. ,.,.,.¢,17 1. Traffic narrative. , 17 a. Number of vehicle trips,....., 17 b. Rou n dt ri ps/dad ,,18 c. Expected travel routes for site traffic. 18 d. Travel distribution along the routes 19 e. Highest traffic volumes to and from the site. ,...,,,19 2. Site Access 19 3. Drainage !Design:19 Appendix: • Affidavit of Interested Land Owners Surface Estate • Chain of Title Guarantee and Deeds • Signed Statement of Taxes from Weld County • Site Plan/Drawings • Drainage Report • Notices of Inquiry 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 15 Western M idstrea m.com QUESTIONNAIRE 1. Explain the proposed use and business name. Kerr-McGee Gathering LLC (KMGG), a wholly owned subsidiary of Western Midstream Partners, LP, is proposing a Major Amendment to the existing St. Vrain Compressor Station (1 USRI 7-14-0013) in order to add a soil stockpile used to support oil and gas development activity in the Denver-Julesburg Basin of Colorado. The intent of the stockpile is to centralize materials near planned operations in order and reduce traffic impacts to neighboring municipalities and road infrastructure. In addition, KMGG is proposing adding a ten -acre storage area to the parcel in order to store equipment used to support water needs associated with exploration and production activities in the Di Basin. The equipment is used to support water delivery infrastructure that allows water to be piped, as opposed to trucked, to drilling and completions locations. 2. Explain the need for the proposed use. Soil stockpile: A soil stockpile provides temporary storage for building materials used in the oil and gas development process that can be reused and recycled. The material stored at the stockpile supports several development phases of oil and gas development, including well and facility pad construction, drilling, completions, environmental remediation, access road construction, road or location maintenance, stormwater repairs, vertical well support and abandonment activities, and final facility or location reclamation. The materials for later use include structural fill, reclaimed road base, gravel, rock used for vehicle tracking control, and recycled concrete (for use as rip rap or stabilizing material for well pads). The location of the St. Vrain Compressor Station is strategic from an operational and safety standpoint: The location is near planned oil and gas activity, which minimizes the amount of trucking on County and municipal roads and limits the overall trucking impact to other communities. Additionally, with a majority of oil and gas development planned for west of Highway 85, the location is ideal in terms of safety as it limits the need for trucks to cross the highway if the destination is on the opposite side, especially as only a select few county roads have traffic signals to facilitate safe crossing. Furthermore, it is located on a parcel with existing oil and gas operations, which is in a relatively remote area with few stakeholders. Storage: The location of the St. brain Compressor Station is strategic from an operational and safety standpoint as it is close to current and proposed activities while allowing safe access into and out of the parcel on paved roads. The proposed storage area is located in the middle of the parcel, which adds a security buffer to the equipment stored on location. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 16 Western Midstream.com The intent of the stockpile is to centralize materials near planned operations in order and reduce traffic impacts to neighboring municipalities and road infrastructure. The storage area will be used to store equipment used to support water needs associated with exploration and production activities in the Di Basin. The equipment is used to support water delivery infrastructure that allows water to be piped, as opposed to trucked, to drilling and completions locations. The soil stockpile and storage area are consistent with Weld County's natural resource goals and objectives outlined in Sec. 22-2-60, specifically, requiring that energy and mineral resource development conserve the land minimize the impact on surrounding land and the surrounding land uses (Sec. 22-2-6-.8.4). 3. Describe the current and previous use of the land. The parcel of land is currently used for natural gas compression operations as part of the existing St. Vrafn Compressor Station (1MU5R17-14-(70I3), which facilitates the transportation of naturql gas from field locations to processing plants. 4. Describe the proximity of the proposed use to residences. Soil stockpile: The closest residential structure is located approximately 1,489 ft. southwest of the proposed stockpile. Concerns regarding truck traffic will be addressed by avoiding WCR 19 and utilizing WCR 17, WRCR 19 X, or WCR 21 instead. Storage area: The closest residential structure is located approximately 1,019' northeast of the proposed storage area. The existing compressor station is located between the proposed storage area and the residential structure. 5. Describe the surrounding land uses of the site and how the proposed use is compatible with them. The parcel on which the St. Vrain Compressor Station is located is currently zoned for Agriculture and surrounded by parcels that are also zoned for Agriculture and are in crop production with limited residential development The proposed change does not change the use of the site or the compatibility of the site with the surrounding uses. 6. Describe the hours and days of operation (e.g. Monday thru Friday 8:00 a.m. to 5:00 p.m.). Soil stockpile: Depending on time of year, the hours of sunlight per day, and the level of operations in the field, the stockpile is typically accessed from 6:00 a.m. to 6:00 p.m., Monday through Friday, with occasional weekend use. If activity is limited, it is possible that the stockpile may not be accessed for months at a time. Storage area: 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page I7 Western Midstream.com Depending on time of year, the hours of sunlight per day, and the level of operations in the field, the storage yard will be typically accessed from 6:00 a.m. to 6:00 p.m., Monday through Friday, with occasional weekend use on Saturday and Sunday from 6:00 a. m to 6:00 p.m. Only in an emergency would the storage area be accessed at night. 7. Describe the number of employees, including full-time, part-time and contractors. If shift work is proposed, detail number of employees, schedule and duration of shifts. Soil stockpile: There are no permanent employees or scheduled shifts proposed as part of this operation. The site will be accessed on an as -needed basis, with soil brought to or removed from the stockpile based on activity in the field. For every loading or unloading operation of the stockpile, a maximum of 20 employees are on site at a time, which account for one blade, dozer, or excavator operator, one loader, and 18 trucks, and one driver of each vehicle. Storage area: There will be one to 1.5 shifts per day, with a maximum of six employees or contractors accessing the location sporadically during the shift. Normal operations will take place from 6 a.m. to 6 p.m. 8. Describe the maximum number of users, patrons, members, buyers or other visitors that the site will accommodate at any one time. Soil stockpile: There are no permanent employees proposed to be on location as part of this operation. For ever loading or unloading operation of the stockpile, a maximum of 20 employees are on site at a time, which account for one blade, dozer, or excavator operator, one loader, and 18 trucks, and one driver of each vehicle. Storage area: There will be a maximum of six employees or contractors on location. 9. List the types and maximum numbers of animals to be on the site at any one time (for dairies, livestock confinement operations, kennels, etc.). There are no animals on site at any time. 10. List the types and numbers of operating and processing equipment to be utilized. For the soil stockpi{e, the equipment utilized on site includes: • Cat 966/980 Loader (one at a time) • Cat 140/160 Motor Grader (one at a time) • Cat D6/D8 Dozer (one at a time) • Cat 320/345 Excavator (one at a time) 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 18 Western Midstrea m.com • Belly Dump Semi -Truck (typically four to five on site loading or dumping at a time but can have upwards of 18 at a time if operations are sta{{ed) • Tandem Dump Truck (typically four to five on site loading or dumping at a time but can have upwards of 18 at a time if operations are stalled) • A mobile screen to be used to clean or screen rock from fill (once a year on high end use or once every three to four years on low end use) For the storage area, the equipment to be stored on site includes: • 8.5 ft./24 ft. Conex boxes storing small fittings, pumps/motors • Lay flat ramps consisting of 18 inch and 10 inch ramps in length • 10 inch fittings. • 12 inch fittings • 10 inch gate valves • 12 inch 40 ft. poly pipe sections • 10 inch 40 ft. poly pipe sections • 20 inch/40 ft. poly pipe sections • 20 inch steel risers • 20 inch steel manifolds • 20 inch/120 ft. steel extensions • Cement pipe weights • Miscellaneous ARV and hydrant guarding. • 20 inch fittings • 10 inch hydrant sweeps • VAF filter skid • Automated meter skid ('x8') • 8 ft./l0 ft. enclosed metering trailers • 12' single axle bumper pull flat trailer • 16' gooseneck hydraulic dump trailer • VAF filter skid (8'x12'?) • Amiad automated filter buildings (8'x12') • Lockable cabinet for propane bottle storage (4'xS') • 40 lb. propane bottles • 15'x50' portable pumping skid units 11. List the types, number and uses of the existing and proposed structures. There will be no additional proposed structures to be erected. 12. Describe the size of stockpile, storage or waste areas. Soil stockpile: There are three sections of the stockpile at approximately 9, 263.4 cubic yards (0.807 acres), 27,114.7 cubic yards (2.113 acres), and 1,140.6 cubic yards (0.14 acres, or 6,115 square feet), respectively. The three sections allow for segregating specific to each of the three types of materials below: 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 19 Western Midstrea m.com 1. Reclaimed gravel: Reclaimed gravel consists of the top four inches of a well or facility pad and has higher gravel content than fill material. This material is used as a top layer on roads or pads to provide a working surface that is less impacted by moisture, which would otherwise cause mud, ruts, stuck vehicles, or slips, trips, and falls. 2. Fill material A general structural fill material that is used to build up roads or well or facility pod locations. its high clay content helps stabilize a road or pad surface over softer incompetent subgrades of soil. 3. Reclaimed concrete (or other larger aggregate material): This material would be re -used as a best management practice (such as rip rap or check dams) where applicable, or used to help construct a well pad or on access road where larger aggregate material is needed to stabilize soil subgrades. Storage area: The proposed storage area is 12.68 acres within the fenced boundary, which includes 8.21 groveled acres (comprised of the 7.67 -acre graded and graveled pad and 0.54 acres of graveled access road) and 4.47 undisturbed acres. The 12.68 -acre area accounts for the graveled pad as well as the access road and turnaround loops. 13. Describe the method and time schedule of removal or disposal of debris, junk and other wastes associated with the proposed use. Soil stockpile: Trucked or stored fill materials generally do not generate trash or debris. When necessary, a roustabout crew (general laborers) will provide cleanup. Storage area: waste will be removed from the location once every one to two months in a roll -away dumpster (non- hazardous). 14. Include a time table showing the periods of time required for the construction of the operation. Soil stockpile: There will be no additional construction needed as part of this amendment The use of the stockpile will depend on the level of oil and gas activity in the area. Depending on time of year, the hours of sunlight per day, and the level of operations in the field, the stockpile is typically accessed from 6:00 a.m. to 6:00 p.m., Monday through Friday, with occasional weekend use. It is possible that the stockpile may not be accessed for months at a time if there is limited activity. Storage area: The storage area may be stabilized using road base to provide a base for vehicles and equipment, but there will be no grading of the parcel. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 110 Western Midstream.com Construction of the storage yard will generally take 60-90 days depending on availability of contractors, materials, and potential weather delays. 15. Describe the proposed and existing lot surface type and the square footage of each type (e.g. asphalt, gravel, landscaping, dirt, grass, buildings). Soil stockpile: The soil stockpile area is approximately 6.67 acres of soil storage. Storage area: The laydown yard will be comprised of approximately 8.21 acres of gravel for the graded yard and access roads and approximately 4.47 acres of undisturbed/native storage area. The existing lot surface for the storage area is wheat field/agricultural tilled soil. 16. How many parking spaces are proposed? How many handicap -accessible parking spaces are proposed? There are no parking spaces associated with our planned activity. 17. Describe the existing and proposed fencing and screening for the site including all parking and outdoor storage areas. Soil stockpile: The stockpile sits outside the six-foot chain -link perimeter fence of the St. Vroin Compressor Station that has barbed wire on top. Due to the relatively remote area and the natural screening of the dirt, there is no additional screening proposed for this amendment. Storage area: There will be a chain link fence surrounding the proposed storage area. Due to the relatively remote area and the natural screening of the dirt, there is no additional screening proposed for this amendment. 18. Describe the existing and proposed landscaping for the site. Existing landscaping for the St. Vramn Compressor Station includes small trees around the perimeter fence. Due to the remote area, the natural screening of the dirt, and the absence of valuable equipment or material being stored, there is no additional screening proposed for this amendment. 19. Describe reclamation procedures to be employed as stages of the operation are phased out or upon cessation of the Use by Special Review activity. Upon cessation of activity, all remaining materials will be removed from site, and the site will be graded back to native contours and elevations. If deemed necessary through internal environmental reclamation procedures, compost may be spread at a rate of 20 cubic yards per acre. The location will be deep ripped to a depth of greater than or equal to 18 inches. Following ripping, seed bed will be prepared. The seed mixture to be utilized 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page X11 Western Midstrea m.com will be determined through internal environmental reclamation procedures. When disturbed footprint of reclaimed stockpile is straw crimped and stabilized, certified -weed free straw will be used for stabilization at approximately 1.5 tons per acre. All twine, location flags, and associated debris from reclamation and seeding practices will be removed. 20. Describe the proposed fire protection measures. All vehicles involved in the operation of the stockpile (La, excavators, trucks, dozers) and the storage area (pick- up trucks, pick-up trucks with a trailer, semi -trucks with flatbed trailer) are equipped with fire extinguishers. Soil stockpile: Due to the nature of the operation of the stockpile and the fact that hydrocarbon -impacted material will not be brought to site, the risk of fire associated with stockpile operations is low. Storage area: Although there will be up to 36 40 lb. propane bottles stored on location, the bottles will be stored in an explosion -proof locked cage. Other operations at the St. Vrain Compressor Station will continue to be subject to the existing emergency response plan approved as part of the original Use by Special Review permit. All roads leading to and within the site will continue to be maintained to support fire apparatus. KMGG has support personnel in the field and on call at all times to coordinate with first responders and provide emergency response and technical assistance in the event of a fire. 21. Explain how this proposal is consistent with the Weld County Comprehensive Plan per Chapter 22 of the Weld County Code. The Weld County Comprehensive Plan, per Chapter 22 of the Weld County Code, recognizes in Appendix 22-C under the Right to Extract Mineral Resources Statement that Weld County's abundant mineral resources are "vital resources" and "essential to the state's economy. " The Statement also states that mineral deposits "should be extracted according to a rational plan, calculated to avoid waste of such deposits and cause the least practicable disruption of the ecology and quality of life of the citizens of the populous counties of the state. "f The proposed addition of a stockpile and storage area to an existing compressor station location enables centralized access to materials needed for oil and gas operations and increases capacity for future oil and gas development The proposed addition of this use at this location conserves land by eliminating the need for another such site elsewhere in the same area of Weld County. The use of the land is consistent with Chapter 22: Section 22-2-60.8 outlines the goal of supporting responsible energy and mineral development. Section 22-2-60.8.3 requires that "energy and mineral resource development conserve the land and minimize the impact on surrounding land and the existing surrounding land uses." Section 22-2-60.8.5 advises that "irejnergy development facilities should preserve agricultural areas and enhance the rural landscape." The proposal of the stockpile and the storage area is consistent with the Weld County Comprehensive Plan. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page X12 Western Midstream.com 22. Explain how this proposal is consistent with the intent of the zone district in which it is located. (Intent statements can be found at the beginning of each zone district section in Article III of Chapter 23.) Section 23-3-10 of the Weld County Code states that the A `Agricultural) Zone District is intended to provide areas for natural resource extraction and energy development The proposed use is consistent with the A (Agricultural) Zone District. Section 23-3-40. W of the Weld County Code provide for Oil and Gas Support and Service. 23. Explain how this proposal will be compatible with future development of the surrounding area or adopted master plans of affected municipalities. The parcel of land is located in unincorporated Weld County but within the Town of Platteville's Master Plan area. In response to the Notices of Inquiry sent to Platteville regarding the soil stockpiling and the storage area (PRE20-0153 and PRE20-001S, respectively), Platteville Town Manager Troy Renken expressed no concerns and no intent to pursue annexation of the property. According to Platteville's Three Mile Area Plan, the parcel of property falls under the Agricultural/Holding land use classification, which is intended to encourage the sustainability of the regional agricultural and energy economy. Because the soil stockpile and storage area will be added to a parcel of land that has been used for oil and gas operations since 2014, this proposed use will not affect the compatibility with future development of the surrounding area or Platteville's growth plans. 24. Explain how this proposal impacts the protection of the health, safety and welfare of the inhabitants of the neighborhood and the County. Soil stockpile: The stockpile consists of structural fill, reclaimed road base, gravel, rock used for vehicle tracking control, and recycled concrete. There will be no hydrocarbon -impacted material brought to site. As such, the addition of the stockpile to the parcel does not interfere with the protection of the health, safety, and welfare of the inhabitants of the neighborhood and the County. Storage area: The storage area, and the minimal traffic associated with its operation, does not interfere with the protection of the health, safety, and welfare of the inhabitants of the neighborhood and the County. 25. Describe any irrigation features. If the proposed use is to be located in the A (Agricultural) Zone District, explain your efforts to conserve prime agricultural land in the locational decision for the proposed use. There will be no proposed irrigation features. The parcel on which the St. gain Compressor Station is located is currently zoned for Agriculture and surrounded by parcels that are also zoned for Agriculture and are in crop production with limited residential development. The proposed addition of the stockpile and the storage area does not change the use of the site or the compatibility of the site with the surrounding uses. Additionally, consolidating the soil at this location reduces the need for stockpiles at other locations, reducing overall impacts on agricultural operations in the County. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 113 Western Midstream. corn 26. Explain how this proposal complies with Article V and Article Xl of Chapter 23 if the proposal is located within any Overlay Zoning District (Airport, Geologic Hazard, or Historic Townsites Overlay Districts) or a Special Flood Hazard Area identified by maps officially adopted by the County. The parcel of land for which the stockpile and storage area are proposed is not located within any Overlay Zoning District '`Airport, Geologic Hazard, or Historic Townsites Overlay Districts) or a Special Flood Hazard Area identified by maps available on the County website. 27. Detail known State or Federal permits required for your propose use(s) and the status of each permit. Provide a copy of any application or permit. There are no State or Federal permits required for the proposed use. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page X17 Western Midstrea m.com Public Works Questions: 1. Include a traffic narrative with the information below. A traffic impact study may be required. Improvements to adjacent streets/roads may be necessary to provide adequate safe and efficient transportation to and from the site. An Improvements Agreement may be required. a. The projected number of vehicle trips (average per day, maximum per day, peak hour data) to and from the site and the type of vehicles (passenger, semi -truck, etc.). Soil stockpile: The use of the stockpile will depend on the level of activity in the basin, which has typically ranged from the construction of four to six new well/facility pads and the reclamation of two to four locations per year. When pads, locations, and roads are not actively built, reclaimed, or improved, the stockpile will not be utilized. It is possible that the stockpile may not be accessed for months at a time. Estimates of the truck trips needed to support a new well/facility pad are summarized below. The projected number of vehicle trips to and from the site are based on the maximum duration of well pad construction, which is 14 days, and consists of two scenarios: average (based on a 6,000 -cubic yard export) and maximum (based on a 12,000 -cubic yard export). Interim reclamation requires approximately 20 percent less traffic volume than a new well/facility pad. Projected traffic data for the average scenario (based on a 6,000 -cubic yard export) is summarized in this table: 14 -Day Period Trips/Day Pickups/Passenger Cars 84 6 Tandem Trucks 89 6 Semi and Trailer 375 27 Total Trips (Avg/Day) 39 39 Total 548 Projected traffic data for the maximum scenario (based on a 12,000 cubic -yard export) is summarized in this table: 14 -Day Period Trips/Day Pickups/Passenger Cars 84 6 Tandem Trucks 89 6 Semi and Trailer 875 63 Total Trips (Avg/Day) 75 75 Total 1,048 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 118 Western Midstrea m.com Storage area: Generally, the storage area will generally be accessed between the hours of 6 a.m. and 6 p.m., with equipment picked up in the mornings and dropped off in the evenings and occasional weekend use. Only in an emergency would the storage area be accessed at night. The vehicles accessing the storage area will include pick-up trucks, pick-up trucks with a trailer, and, on an infrequent basis, semi -trucks with a flatbed trailer. Typical daily truck trips will range from two to eight. b. Describe how many roundtrips/day are expected for each vehicle type: passenger Cars/Pickups, Tandem Trucks, Semi-Truck/Trailer/RV (Roundtrip = 1 trip in and 1 trip out of site) Soil stockpile: The projected number of vehicle trips to and from the site are based on the maximum duration of well pad construction, which is 14 days, and consists of two scenarios: average (based on a 6,000 - cubic yard export) and maximum (based on a 12,000 -cubic yard export). Projected traffic data for the average scenario (based on a 6,000 -cubic yard export) is summarized in this table: 14 -Day Period Trips/Day Pickups/Passenger Cars 84 6 Tandem Trucks 89 6 Semi and Trailer 375 27 Total Trips (Avg/Day) 39 39 Total 548 Projected traffic data for the maximum scenario (based on a 12,000 cubic -yard export) is summarized in this table: 14 -Day Period Trips/Day Pickups/Passenger Cars 84 6 Tandem Trucks 89 6 Semi and Trailer 875 63 Total Trips (Avg/Day) 75 75 Total 1/048 WOO: The vehicles accessing the storage area will include pick-up trucks, pick-up trucks with a trailer, and, on an infrequent basis, semi -trucks with a flatbed trailer. Typical daily truck trips will range from two to eight. c. Describe the expected travel routes for site traffic. • To travel east of the location: east on WCR 34 and then south on WCR 21. • To travel north of the location: north on WCR 19 %. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page X19 Western Midstream.com • To travel west of the location: west on WCR 34 and then either north or south on WCR 17 or continued travel west on WCR 34. • Where possible, traveling west on WCR 34 and then south on WCR 19 will be avoided. d. Describe the travel distribution along the routes (e.g. 50% of traffic will come from the north, 20% from the south/ 30% from the east, etc.) The travel distribution along the routes will depend on where the material is coming from or is needed throughout the Denver-Julesburg Basin. e.Describe the time of day that you expect the highest traffic volumes to and from the site. Soil stockpile: The highest traffic volumes to and from the site are expected to occur around 7:00 a.m., when trucks show up for first load. Storage area: The site will likely be accessed in the mornings, to pick up equipment, and in the evenings, to drop off equipment. 2. Describe where the access to the site is planned. The existing access to the St. Vrain Compressor Station (AP14-00090), located south of CR 34 near the intersection of CR 34 and CR 19 %, will be used for access onto the parcel. 3. Drainage Design: Design and construction of a detention pond as described in an approved Drainage Report is required unless the project falls under an exception to stormwater detention requirements per code. (See below.) Does your site qualify for an exception to stormwater detention? The site does not qualify for an exception to stormwater detention. If your site does not qualify for an exception, the following applies: a. A Drainage Report summarizing the detention pond design with construction drawings and maintenance plan shall be completed by a Colorado Licensed Professional Engineer and adhere to the drainage related sections of the Weld County Code. b. The Drainage Report must include a certification of compliance, which can be found on the Public Works website, stamped and signed by the PE. c. See the attached Drainage Report Review Checklist. A preliminary drainage report outlining design criteria and calculations for stormwater detention was prepared for the site following Weld County Code and the drainage report checklist. The report, construction drawings, and certification compliance will be stamped and signed by a Colorado Licensed Professional Engineer after preliminary comments are received and the final report is submitted. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 114 Western Midstrea m.com Environmental Health Questions: 1. What is the drinking water source on the property? If utilizing a drinking water well include either the well permit or well permit application that was submitted to the State Division of Water Resources. If utilizing a public water tap include a letter from the Water District, a tap or meter number, or a copy of the water bill. Only bottled water will be used on site in relation to this activity. 2. What type of sewage disposal system is on the property? If utilizing an existing septic system provide the septic permit number. If there is no septic permit due to the age of the existing septic system, apply for a septic permit through the Department of Public Health and Environment prior to submitting this application. If a new septic system will be installed please state "a new septic system is proposed." only propose portable toilets if the use is consistent with the Department of Public Health and Environment's portable toilet policy. There is no sewage disposal system proposed for the operation of the stockpile or the storage area. On -site portable toilets will be utilized if necessary. Similar to the existing on -site portable toilets at the compressor station, the proposed toilets will not be screened. 3. If storage or warehousing is proposed, what type of items will be stored? Soil stockpile: The materials stored at the stockpile support several development phases of oil and gas development, including well and facility pad construction, drilling, completions, contamination backfill, road or location maintenance, storm water repairs, vertical well support and abandonment activities, and final facility or location reclamation. The materials for later use include structural fill, reclaimed road base, gravel, rock used for vehicle tracking control, and recycled concrete (for use as rip rap or stabilizing material for well pads). The equipment necessary for the operation of the stockpile (i.e., excavators, trucks, dozers) will be on location only during active operations. Storage area: The equipment to be stored in the proposed storage area include Conex boxes, pipe fittings, pipe sections, steel risers, steel manifolds, pipe weights, enclosed metering trailers, Amiad automated filter buildings, propane bottles, and portable pumping skid units. 4. Describe where and how storage and/or stockpile of wastes, chemicals, and/or petroleum will occur on this site. Soil stockpile: The only materials stored at the stockpile as part of this amendment include structural fill, reclaimed road base, gravel, rock used for vehicle tracking control, and recycled concrete. There are no chemicals stored on location as part of the stockpile. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 115 Western Midstrea m.com Storage area: There will be up to 36 40 lb. propane bottles stored on location. The bottles will be stored in an explosion -proof locked cage. 5. If there will be fuel storage on site, indicate the gallons and the secondary containment. State the number of tanks and gallons per tank. Soil stockpile: There is no fuel storage on site associated with this amendment. Storage area: There will be up to 36 40 lb. propane bottles stored on location. The bottles will be stored in an explosion -proof locked cage. 6. If there will be washing of vehicles or equipment on site, indicate how the wash water will be contained. There will be no washing of vehicles or equipment on site as part of this amendment 7. If there will be floor drains, indicate how the fluids will be contained. There will be no floor drains on site as part of this amendment. 8. indicate if there will be any air emissions (e.g. painting, oil storage, etc,). Soil stockpile: Possible air emission sources include trucks, dirt work equipment, mobile screening equipment, and light passenger vehicles. As hydrocarbon -impacted material will not be brought to site, there will be no emissions directly related to hydrocarbons. Storage area: The only source of air emissions associated with the storage area will be from vehicles. 9. Provide a design and operations plan if applicable (e.g. composting, landfills, etc.). Soil stockpile: The operation of the stockpile consists of two main phases: receiving and exporting. During the receiving phase, material is hauled to the stockpile for later use. A belly dump truck, a side dump truck, or tandem dump trucks will bring material to the site. A piece of equipment, typically a motor grader or a bulldozer, will be on site to build and maintain the stockpile as the material is 1201 Lake Robbins Drive The Woodlands, Texas 77380 Western Midstream Page 116 Western Midstream.com transferred from the trucks to the stockpile, and will also ensure that the access roads are maintained so as to facilitate trucks to enter and exit safely and efficiently. During the exporting phase, material is hauled out of the stockpile. A belly dump, a side dump truck, or tandem trucks will be loaded with either a loader or an excavator. Trucks will travel from the stockpile to the destination, where the material is needed, and return to the stockpile for another load. Storage area: To prepare the storage area, road base may be brought in to provide a stable working surface for vehicles and equipment. During operations, the storage area will generally be accessed between the hours of 6 a.m. and 6 p.m., with equipment picked up in the mornings and dropped off in the evenings and occasional weekend use. Only in an emergency would the storage area be accessed at night. The vehicles accessing the storage area will include pick-up trucks, pick-up trucks with a trailer, and, on an infrequent basis, semi - trucks with a flatbed trailer. Typical daily truck trips will range from two to eight. 10. Provide a nuisance management plan if applicable (e.g. dairies, feedlots, etc.). As with all its operations, KMGG will be responsive to issues raised by the County and nearby residents. 1201 Lake Robbins Drive The Woodlands, Texas 77380 Diana Aungst From: Sent: To: Cc: Subject: Tyler French <tfrench@609consulting.com> Wednesday, June 30, 2021 12:05 PM Diana Aungst Melissa King RE: 2MJUSR21-14-0013 Drainage Report for St Vrain Compressor Caution: This email originated from outside of Weld County Government. Do not click links or open attachments unless you recognize the sender and know the content is safe. Hi Diana, There was some confusion on this per previous conversations with Western Midstream so I am not surprised things might not match up. I will do my best to explain. There are 12.68 acres within the fenced boundary of the proposed laydown yard. The graded/graveled portion of the laydown yard is 7.67 acres. In total, there is 8.23 acres of proposed graveled surface (7.67 acres from graded storage pad and 0.56 acres from access roads/turn arounds). I am unsure what is represented by the 10 acres found in the application. Please let me know if I can help explain any other inconsistencies. Thanks, Tyler Tyler P. French, P.E. 609 Consulting, LLC (307) 674-0609 1 r - _SINS OW EXISTING ROAD 'tam - 4. PROPOSED ACCESS ROAD PROPOSED FENCED rX BOUNDARY (12.68 ACRES ----16: ) 4795 _ PROPOSED GRADED LAYDOWN YARD (7.67 ACRES) .r 7 % " e SI r Sr X X--X-X--- 4 1 a EXISTING ST. VRMIN COMPRESSOR STATION SOIL \SIOCKPILF AREA (6.67 ACRES) \K From: Diana Aungst <daungst@weldgov.com> Sent: Tuesday, June 29, 2021 2:52 PM To: tfrench@609consulting.com Cc: Melissa King <mking@weldgov.com> Subject: RE: 2MJUSR21-14-0013 Drainage Report for St Vrain Compressor Hi - This brings up another question. How big is the laydown yard? It states 10 acres in the application questionnaire and shows 7+/- on the USR map. And in the email below Melissa calls out 12 +/-. Thanks, Diana Aungst Planner Weld County Department of Planning Services 1555 N. 17th Avenue - Greeley. Colorado 80631 D: 970-400-3524 O: 970-400-6100 Fax: 970-304-6498 daungst@weldgov.com www. weldgov. corn 0 D SI Confidentiality Notice: This electronic transmission and any attached documents or other writings are intended only for the person or entity to which it is addressed and may contain information that is privileged, confidential or otherwise protected from disclosure. If you have received this communication in error, please immediately notify sender by return e-mail and destroy the communication. Any disclosure, copying, distribution or the taking of any action concerning the contents of this communication or any attachments by anyone other than the named recipient is strictly prohibited. From: Melissa King <mking@weldgov.com> Sent: Tuesday, June 29, 2021 2:46 PM To: tfrench@609consulting.com Cc: Diana Aungst <daungst@weldgov.com> Subject: 2MJUSR21-14-0013 Drainage Report for St Vrain Compressor Good Afternoon, Thank you for the telephone conversation. Just a few items to address on the referenced submittal: 1. For the 12.68 acre laydown yard, will water quality be provided in the grass swale ? If yes, provide cross sections and calculations to prove maximum velocity does not exceed 1 ft/sec. It is noted that the diversion ditches have velocities greater than 1 foot/second — thus, no water quality treatment is occurring. 2. The current outlet design and emergency spillway design do not meet Weld County Code requirements. See Section 8-11-100. Revise or request a variance. Variance request specifics are attached. These specifics should accompany the Certif of Compliance in which a variance is requested. The Certif of Compl is also attached. 3. How does the proposed fencing affect the ditch overflow onto the Undisturbed (native) Storage Area? 4. Will laydown storage in the Undisturbed (native) Storage area affect detention volumes? 5. Table 4 in the narrative states that 2.651 acre feet is required for 100 yr 1 hr storm event. However, in Sec 3.1, only 1.773 acre feet is acknowledged as needed. Review and revise as appropriate. 6. Provide cross sections of the storage swales and the storage area of the Undisturbed (native) Storage Area . A grading permit will be required since an acre will be disturbed. During the review of the grading permit, the erosion and sediment control devices will be reviewed. Let me know if there are questions Melissa Melissa J King, PE Development Review Engineer Department of Public Works Weld County 1111 H Street, P.O. Box 758 Greeley, CO 80632 (970) 400-3762 Vat LEADING WITH RESPONSIVE, INNOVATIVE AND COST EFFECTIVE SERVICES 3 Subject: FW: [EXTERNAL]: Conex boxes in the storage area From: Van der Vieren, David <David.VanderVieren@westernmidstream.com> Sent: Thursday, June 24, 2021 10:41 AM To: Diana Aungst <daungst@weldgov.com> Subject: Re: [EXTERNAL]: Conex boxes in the storage area Caution: This email originated from outside of Weld County Government. Do not click links or open attachments unless you recognize the sender and know the content is safe. Hey Diana, The total number on Connex Boxes will be 30. Please let me know if you have any other questions. Thank you, David Van der Vieren DJ Basin Regulatory Group (720) 929-3812 1 WELD COUNTY ACCESS PERMIT Weld County Public Works Dept. 1111 H Street P.O. Box 758 Greeley, CO 80632 Phone: (970) 304-6496 After Hours: (970) 356-4000 Emergency Services: (970) 304-6500 x 2700 Inspection: (970) 304-6480 Permit Number: API4-00090 Issuance of this permit binds applicant and its contractors to all requirements, provisions, and ordinances of Weld County, Colorado. Project Name: St. Vrain Compressor Station Applicant Information: Name: Nathan Keiser Company: Kerr-McGee Oil & Gas Onshore LP Phone: 720-929-5896 Email: natha n . ke ise ra nada rko . co m Location: Access is on WCR: Nearest Intersection WCR: Distance From Intersection: Number of Existing Accesses: 34 34 1540 6 Planning Process: USR USR14- & WCR: 19 Road Surface Type & Construction Information: Road Surface: Asphalt Culvert Size & Type: 15" CMP/RCP min. Start Date: Finish Date: Materials to Construct Access: Class 6 Road Base Required Attached Documents Submitted: Traffic Control Plan: No Expiration date: 09/25/2014 Property Owner Information: Name: Company: same as applicant Phone: Email: Proposed Use: Temporary: Single Residential: Industrial: Small Commercial: Oil & Gas: IZI Large Commercial: Subdivision: Field (Agricultural 0 Only)/Exempt: Certificate of Insurance: No Access Pictures: Yes A copy of this permit must be on site at all times during construction hours Daily work hours are Monday through Friday DAYLIGHT to Y2 HOUR BEFORE DARK (applies to weekends if approved) Approved MUTCD traffic control/warning devices are required before work begins and must remain until completion of work Special Requirements or Comments Parcel 120915200036. Utilize NEW access point on CR 34 (1-O&G) located approx. 1540 ft. East of CR 19. Utilize NEW access point on CR 19 (1-O&G) located approx. 400 ft. South of CR 34. Utilize existing access points on CR 19 (1 -AG) located approx. 2015 ft. South of CR 34. Reclamation of all other existing access points shall be completed prior to 09/25/14. Note: CR 19 & 34 are Collector roadways each with a 60 ft. setback from centerline. Revised on 05107/14. Approved by: Weld County Public Works Date: 5/7/2014 Print Date -Time: 5/7/2014 1:25:03PM Report ID: PW00008v001 Page 1 of 1 Weld County Drainage Code Certificate of Compliance Weld County Case Number: Parcel Number: 120915200036 2MJlJSR21-14-0013 Legal Description, Section/Township/Range: NW4 S15/T3N/R67W Date: 7/14/2021 I Tyler French , Consultant Engineer for Western Midstream (Applicant), understand and acknowledge that the applicant is seeking land use approval of the case and parcel in the description above. I have designed or reviewed the design for the proposed land use set for in the application. I hereby certify, on behalf of the applicant, that the design will meet all applicable drainage requirements of the Weld County Code with the exception of the variance(s) described .... :;�;•xhibits, This certification is not a guarantee or warranty either expressed or implied. Engineer's Stamp: s � ••'''P.•17•. '< �I i . . • • • • sus.. ....I/1412021/10 .. A ••....• Engineer of Record Signature 1. 2. 3. Describe List Describe Demonstrate that result This the there variance of design the the the are project. hardship proposed that criteria no request adverse granting 0NAL Weld the the criterion variance from County with variance Variance Request (If Applicable) of health, -of Weld requested. the -way intent safety, County and/or of the and offsite Code. Weld general properties Two County welfare features Code. as and a of for of alternative A�� engineering stormwater found Code will is still being of in adequately which rationale runoff requested. Section a to variance the which protect 8-11-100 public supports is public being rights is the impacts which of for the proposed design deviate from this criterion. The proposed spillway is designed as a backwater, at - grade channel. A concrete cutoff wall extending below the spillway channel is not included in the proposed design since the at -grade spillway does not have risk of a blow-out or failure. The proposed outlet pipe is designed with HDPE anti -seep collars. Concrete anti -seep collars were not included in the proposed design since HDPE collars achieve the same results and are available and commonly used at other oil and gas sites for detention outlets. The proposed design variances will not lead to negative impacts on public safety or public infrastructure and are not contrary to the intent and general purpose of the criteria presented in Weld County Code. Public Works Director/Designee Review (If Applicablei 7 /i.J SceP-1 1( r r ci Public Works Director/Designee Namd 7f/G'/2_e / Date of Signature Comments: Signature } " Approved E Denied Department of Public Works I Development Review 1111 H Street, Greeley, CO 80631 I Ph: 970-304-6496 I www.weldgov.com/departments/public_works/development_review 08/02/2019 Final Drainage and Erosion Control Re rt for the St. Vrain Laydown Yard 2MJUSR21 14 0013 Prepared for: Western Midstream 1099 18th Street Denver, Colorado 80202 Submitted to: Weld County Public Works Department 1111 H Street Greeley, Colorado 80631 July 2021 609 Consulting, LLC Engineering, Surveying, Consulting & Design Sheridan Office 1095 Saberton Avenue Sheridan, Wyoming 82801 Ph: (307) 674-0609 Fax: (307) 674-0182 Loveland Office 6706 North Franklin Avenue Loveland, Colorado 80538 Ph: (970) 776-4331 Fax: (970) 776-3301 Letter of Transmittal To: cc: Weld County Public Works Department 1111 H Street Greeley, Colorado 80631 Ms. Melissa King, PE, Weld County Ms. Diana Aungst, Weld County Mr. Jayson VanShura, Western Midstream Mr. Brian Venn, PE, 609 Consulting From: Mr. Tyler French, PE 609 Consulting 1095 Saberton Avenue Sheridan, Wyoming 82801 Date: July 14, 2021 Subject: 2MJUSR21-14-0013 - St. Vrain Laydown Yard - Final Drainage and Erosion Control Report To Weld County Public Works Department: On behalf of Western Midstream, we are pleased to submit the Final Drainage and Erosion Control Report for the St. Vrain Laydown Yard as part of an amendment to 1MUSR17-14-001. The purpose of this report is to discuss and summarize the stormwater drainage analysis and design performed for the proposed St. Vrain Laydown Yard. The proposed project will be located in the northwest quarter of Section 15, Township 3 North, Range 67 West in Weld County, Colorado. The drainage analysis and design were prepared using the Weld County Use by Special Review (USR) Procedural Guide, Weld County Engineering and Construction Guidelines, and Weld County Municipal Code as well as the Mile High Flood District (MHFD) Urban Storm Drainage Criteria Manuals. Weld County provided comments and redlines for the Preliminary Drainage and Erosion Control Report for the St. Vrain Laydown Yard on June 29, 2021. These redlines were incorporated into the Final Drainage and Erosion Control Report for the St. Vrain Laydown Yard. We believe the analysis and design satisfy all Weld County drainage requirements. We greatly appreciate your time and consideration in reviewing this submittal. Please contact us with any questions you may have. Respectfully, ittarick, Tylerench Registered Professional Engineer State of Colorado No. 51566 TABLE OF CONTENTS PAGE 1.0 PROJECT DESCRIPTION AND LOCATION 1 1.1 Project Description 1 1.2 Project Location 1 1.3 Drainage Summary 3 2.0 HYDROLOGIC ANALYSIS 3 2.1 Historic and Proposed Runoff 3 2.2 Stormwater Volume 5 3.0 HYDRAULIC ANALYSIS AND DRAINAGE DESIGN 5 3.1 Stormwater Storage 5 3.2 Storage Swales 6 3.3 Diversion Ditch 6 4.0 STORMWATER QUALITY CONTROL 6 5.0 SITE MAINTENANCE AND UPKEEP 7 6.0 CONCLUSION 7 7.0 REFERENCES 8 APPENDICES 9 2MJUSR21-14-0013 - St. drain Laydown Yard - Final Drainage and Erosion Control Report Page I II LIST OF FIGURES PAGE Figure 1. Project Location 2 LIST OF TABLES PAGE Table 1. Point Rainfall Data (NOAA Atlas 14 Point Precipitation Frequency Estimates) 4 Table 2. Area and Weighted Imperviousness 4 Table 3. Peak Flow Estimates 4 Table 4. Calculated Storm Runoff Volumes 5 APPENDICES Appendix A: Drainage and Erosion Control Plan Appendix B: Weld County Drainage Code Certificate of Compliance Appendix C: NRCS Web Soil Survey - Soils Report Appendix I): FEMA Flood Insurance Rate Map FIRMette Appendix E: NOAA Atlas 14 Point Precipitation Frequency Estimates Appendix F: UD-Rational Spreadsheet Calculations Appendix G: MHFD-Detention Spreadsheet Calculations Appendix H: Pipe Buoyancy Calculations Appendix I: Conveyance Calculations for Swale and Ditch Design 2MJUSR21-14-0013 - St. vrain Laydown Yard - Final Drainage and Erosion Control Report Page III 1.0 PROJECT DESCRIPTION AND LOCATION Western Midstream is proposing the construction of the St. Vrain Laydown Yard as part of an amendment to the existing Use by Special Review (tJSR), 1MUSR17-14-001. This USR contains the previously permitted and existing St. Vrain Compressor Station which is located in the northwest quarter of Section 15, Township 3 North, Range 67 West in Weld County, Colorado. Per the requirements outlined in the Weld County USR Procedural Guide, Weld County Engineering and Construction Guidelines, Weld County Municipal Code, and through a direct request from Weld County, this report was prepared to discuss the analysis and design of stormwater drainage at the proposed project site. The Drainage and Erosion Control Plan, developed in conjunction with this report, can be found in Appendix A. The Weld County Drainage Code Certificate of Compliance can be found in Appendix B. 1,1 Project Description The proposed project consists of the construction and operation of the St. Vrain Laydown Yard. The laydown yard is nestled between several existing developed disturbances including the St. Frain Compressor Station to the east, Tomcat F14 Facility and Goose 3 9N-8 HZ well pad to the north, Maverick State 4C -16H Z well pad to the west, and Iceman State 32N-A16HZ well pad to the south. The laydown yard will have a total area of 12.68 acres within the fenced boundary. The southern portion of the fenced area will contain 7.67 acres of graded and graveled storage area and the northern portion of the fenced area will contain the main access road and entrance as well as two turn -around loops which will provide access to the undisturbed (native) portion of the storage yard. Stormwater storage swales, an outlet pipe, and an emergency spillway will be located outside the fenced area on the north and west sides of the laydown yard. Topsoil from stripping the graded portion of the laydown yard will be stored outside the fenced area on the south and west sides of the laydown yard. In addition to the laydown yard, an existing soil stockpile area located just south of the existing compressor station will be included in the USR amendment. The existing soil stockpile area is approximately 2.39 acres and is part of a larger area (6.67 acres) set aside for future soil stockpile storage. Operations and equipment at the existing compressor site have not changed since the last amendment; therefore, the proposed laydown yard and soil stockpile area will be treated separately. Grading and site layout for the St. Vrain Laydown Yard and soil stockpile area can be found in the Drainage and Erosion Control Plan found in Appendix A. 1,2 Project Location The St. Vrain Laydown Yard is located on property owned by Anadarko E&P Company LP (Parcel 120915200036). The project area is approximately 1.5 miles north of Highway 66 and 3.0 miles west of Highway 85. An existing road running south from County Road 34 will provide access to the laydown yard. The Town of Platteville, Colorado municipal boundary is located approximately 0.5 miles to the east of the proposed laydown yard. Because the proposed site is greater than a quarter of a mile from the nearest municipal boundary, the project is considered to be located in a non -urbanizing area. Figure 1 shows the location of the St. Vrain Laydown Yard. 2MJUSR21-14-0013 - St. vrain Laydown Yard - Final Drainage and Erosion Control Report Page 1 Legend Proposed St. Vrain Laydown Yard Existing St. Vrain Compressor Station Soil Stockpile Area Existing Access Road Platteville Municipal Boundary Anadarko E&P Company LP (Parcel 120915200036) 0 N miles 0.26 0.5 Western Midstream LOVELAND OFFICE 67(16 Nort'r Franklin Ave.iue Loveland, 1, Colo ratio 13C538 Phone 970-776-4331 SHERIDAN OFFICE 0}`:r.5 Silk-11O'iAve.'Lit! Slieiidarr, \\ yorrrin7g 82801 Phrwne 307-674-0609 CONSULTING, LLC • • Figure 1s Project Location 2MJUSR21-14-0013 - St. Vrain Laydown Yard - Final Drainage and Erosion Control Report Soils data for the project area were taken from NRCS Soil Data Viewer. The project area is comprised of Nunn clay loam (0 to 1 percent slopes) with a Hydrologic Soil Group (HSG) classification of Group C soils. The soils report for the project area can be found in Appendix C. The St. Vrain Laydown Yard will be constructed on reclaimed agricultural land. According to the 2016 National Land Cover Database, the project area is classified as cultivated cropland. According to the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (Panel 08123C1885E, Effective Date: 1/20/2016), the St. Vrain Laydown Yard is in an area of minimal flood hazard (Zone X) and is therefore determined to be outside the 500 -year floodplain. The corresponding FIRMette displaying the flood zone classification at the project site can be found in Appendix D. 1.3 Drainage Summary The project area lies within the Outlet Saint Vrain Creek basin, Hydrologic Unit Code Level 12 (HUC 12) : 101900050709. The HUC 12, approximately 20.5 square miles in area, consists predominately of agricultural land draining to Saint Vrain Creek. Currently, there has not been a master drainage plan developed for this area. Historically, stormwater at the project site would drain from southeast to northwest until joining Saint Vrain Creek. A network of roads and irrigation ditches has altered historic drainage conditions. Currently, stormwater generated at the proposed project site drains northwest along reclaimed agricultural fields, under County Road 34, and then into the Saint Vrain Creek floodplain. 2.0 HYDROLOGIC ANALYSIS The following sections outline the methods used and corresponding results for the hydrologic analysis of the project site and drainage design including historic runoff, design flow, and stormwater volume. 21 Historic and Proposed Runoff Per Weld County Municipal Code requirements, runoff from the 1 -hour, 100 -year storm falling on the developed site should be detained and released at the historic runoff rate of the 1 -hour, 10 -year storm falling on the undeveloped site for non -urbanizing areas. Historic is defined as an undeveloped site with an imperviousness of 2.0 percent. The rational method was chosen to estimate peak flows for the project area. As discussed in the Mile High Flood District (MHFD) manual Urban Storm Drainage Criteria Manual Volume / (USDCM VI), it is acceptable to use the rational method for design storm analysis of catchments that are not complex and are 90 acres or less in size. The MHFD spreadsheet model Peak Runoff Prediction by the Rational Method Version 2.00 (UD-Rational) was used to calculate peak flows using the rational method. One -hour point rainfall data were obtained from NOAA Atlas 14 Point Precipitation Frequency Estimates using coordinates for the project site. One -hour point rainfall data are summarized in Table 1 and a copy of the point precipitation frequency estimates obtained from NOAA can be found in Appendix E. Overland flow length,overland flow slope, channelized flow length, and channelized flow slope parameters were estimated using field survey, LiDAR data obtained from USGS's The National Map Download, imagery, and proposed grading design. 2MJUSR21-14-0013 - St. Vrain Laydown Yard - Final Drainage and Erosion Control Report Page 3 Per Weld County recommendation, 2007 MHFD C -Values were used to override the runoff coefficient, C. H SU was derived from an area -weighted average using NRCS S Soil Data Viewer. HSG and soils data for the project area can be found in Appendix C. USDCM VI was referenced for recommended conveyance factor (K]. Computed Time of Concentration (Tc) was used for areas with imperviousness of less than 20 percent. Calculations for area - weighted averages of percent imperviousness are found in Table 2. Peak flow estimates calculated using the rational method are summarized in Table 3. UD-Rational inputs and results can be found in Appendix F. Table 1. Point Rainfall Data (NOAA Atlas 14 Point Precipitation Frequency Estimates) Storm Event Frequency One -Hour Point Rainfall, in 2 -year 0.827 5 -year 1.10 10 -year 1.39 25 -year 1.85 50 -year 2.27 100 -year 2.74 500 -year 4.05 Table 2. Area and Weighted Imperviousness Basin Total Area, acre Open (2% Imperv), acre Gravel (40% Imperv, acre Weighted Imperviousness acre % Laydown Yard - Historic 16.11 16.11 0.00 0.32 2.0 Laydown Yard - Proposed 16.11 7.88 8.23 3.45 21.4 Soil Stockpile Area - Historic 6.67 6.67 0.00 0.13 2.0 Soil Stockpile Area - Proposed 6.67 6.67 0.00 0.13 2.0 Table 3. Peak Flow Estimates Basin Calculated Peak Flow, cfs 2 -year 5 -year 10 -year 25 -year 50 -year 100 -year Laydown Yard - Historic 0.7 2.5 5.1 9.9 14.4 19.7 Laydown Yard - Proposed 3.2 6.3 10.4 17.9 24.8 32.9 Soil Stockpile Area - Historic 0.4 1.3 2.7 5.3 7.6 10.4 Soil Stockpile Area - Proposed 0.4 1.3 2.7 5.3 7.7 10.5 Because the soil stockpile area has no change in imperviousness and negligible change in peak runoff (0.1 cfs during the 100 -year event), stormwater from this area will not be detained for release at lower rates. This area will, however, be part of Best Management Practice (BMPJ recommendations for sediment and erosion control. 2MJUSR21-14-0013 - St. drain Laydown Yard - Final Drainage and Erosion Control Report Page 4 2.2 Stormwater Volume In accordance with Weld County Municipal Code requirements, stormwater from the 1 -hour, 100 -year storm falling on the laydown yard will be detained and released at reduced flow rates. The MHFD spreadsheet model Detention Basin Design Workbook Version 4.03 (MHFD-Detention) was used to calculate storm runoff volumes. One -hour point rainfall data for the project area (Table 1) were used within MHFD-Detention. Watershed parameters including area, length, and slope as well as imperviousness and soil type were calculated based on the site design and site characteristics. Table 4 shows storm runoff volumes calculated for the laydown yard. MHFD-Detention inputs and results can be found in Appendix G. Table 4. Calculated Storm Runoff Volumes Basin Storm Runoff Volume, acre -ft 2 -year 5 -year 10 -year 25 -year 50 -year 100 -year 500 -year Laydown Yard - Proposed 0.180 0.359 0.674 1.359 1.924 2.651 4.530 3.0 HYDRAULIC ANALYSIS AND DRAINAGE DESIGN Criteria presented in the MHFD Urban Storm Drainage Criteria Manuals outline the capacity, velocity, and slope requirements involved with drainage design and stormwater conveyance. The following sections describe the design recommendations for storage and conveyance of stormwater at the St. Vrain Laydown Yard. The recommended drainage design is shown in the Drainage and Erosion Control Plan which can be found in Appendix A. 3.1 Stormwater Storage Stormwater from the laydown yard, access road, and native storage area will be stored using a combination of storage swales and berms. The laydown yard will drain west into a diversion ditch which will direct stormwater north into the storage swales. The storage swales, located on the west and north sides of the native storage area, will store and direct stormwater to an outlet near the northwest corner of the storage yard. During the S -year event, stormwater will pond to a maximum depth of 0.76 feet and be fully contained within the storage swales. During events larger than the 5 -year, detained stormwater will begin to back up out of the swales onto the fenced native storage area. Fencing will be standard chain link which will allow water to move between the areas by freely flowing through and under the fence. During the 100 -year event, stormwater will pond to a maximum depth of 1.85 feet with a peak storage volume of 1.773 acre-feet. During the 500 -year event, stormwater will pond to a maximum depth of 2.14 feet with a peak storage volume of 2.868 acre-feet. The outlet for the storage berm consists of a 12 -inch diameter high -density polyethelene (HDPE) pipe. With an orifice invert at the bottom of the storage Swale, a peak flow of 4.4 cfs will occur during the 100 -year event which is lower than the the allowable (10 -year historic peak) release rate of 5.1 cfs. It will take approximately 10 hours to drain 99 percent of the inflow volume during the 100 -year event. Buoyancy calculations were performed for the outlet pipe. Using a factor safety of 1.5, it was found that a minimum cover of 1.0 feet is needed to anchor the 12 -inch outlet pipe during fully saturated conditions. Buoyancy calculations can be found in Appendix H. Anti - seep collars should be used to prevent seepage through the berm and outlet slopes should be protected using geotextile fabric or rip rap in order to prevent erosion along the embankment. 2MJUSR21-14-0013 - St. drain Laydown Yard - Final Drainage and Erosion Control Report Page 5 The emergency spillway will be located on the west side of the laydown yard between the topsoil stockpile and the existing Maverick State 4C-16HZ well pad. The spillway will be built at grade (native ground) with a crest length of 20 feet, 4:1 side slopes, and a crest invert elevation at 4794.07 feet (1.9 feet above the outlet invert) allowing adequate storage for the 100 -year volume before stormwater reaches the spillway. Berms located on the north and west sides of the storage swales will be built to a minimum elevation of 4795.07 feet (2.9 feet above the outlet invert) in order to provide a freeboard of at least 1.0 feet above the spillway. The spillway was designed to convey the 100 -year peak flow at a depth of 0.50 feet. Stormwater storage and outlet sizing details for the storage swales, berms, and spillway can be found in Appendix A. Supporting calculations using MHFD-Detention can be found in Appendix G. 3.2 Storage swales The storage area is comprised of two swales that converge to collect, store, and direct on -site stromwater to the outlet. The western swale has a bottom width of 30.0 feet with 4:1 side slopes and 0.2 percent slope. The northern swale has a bottom width of 6.0 feet with 4:1 side slopes and 0.2 percent slope. Combined, the storage swales can store approximately 0.182 acre -ft before spilling out into the native storage area. The swales will be permanently seeded to prevent erosion and sedimentation issues. Altough the swales will mainly operate under backwater conditions during larger storm events, free -flow conveyence calculations were performed to assess both peak flow capacity and velocity. It was found that the western swale can convey 12.6 cfs at a depth of 0.4 feet with a velocity of 1.0 feet per second (fps) and the northern swale can convey 3.8 cfs at a depth of 0.48 feet with a velocity of 1.0 fps. Both swales can convey more than the 2 -year event peak flow calculated for the entire site (3.2 cfs) with velocities less than 1.0 fps; therefore, the swales are able to provide water quality treatment. Manning's calculations for swale conveyance can be found in Appendix I. 3,3 Diversion Ditch A diversion ditch will be used to collect and direct on -site stormwater to the storage swales and outlet. Manning's equation was used to calculate conveyance based on the diversion ditch design. The diversion ditch was found to convey 6.6 cfs at a depth of 1.0 feet, 19.6 cfs at a depth of 1.5 feet, and 42.2 cfs at a depth of 2.0 feet. The diversion ditch has more than adequate capacity to convey the 100 -year peak flow for the entire laydown yard (32.9 cfs) even though the ditch will only convey runoff from the southern portion of the laydown yard. Manning's calculations for ditch conveyance can be found in Appendix I. 4.0 STORMWATER QUALITY CONTROL In order to protect the project site, public road ROW and access, and future development plans while also meeting the requirements outlined in the Weld County Municipal Code, several stormwater quality control BMPs have been integrated into the site plans for the St. Vrain Laydown Yard. The following discussion outlines BMPs and procedures for stormwater quality control. 2MJUSR21-14-0013 - St. vrain Laydown Yard - Final Drainage and Erosion Control Report Page 6 As discussed in Section 3.1, the laydown yard will drain on -site stormwater to storage swales and an outlet. The swales and outlet have been properly sized to capture and control stormwater from the 100 -year event. Both swales can convey more than the 2 -year peak flow with a velocity less than 1.0 fps thus providing water quality treatment. Additionally, the topsoil stockpiles were positioned to direct off -site runoff away from the site which will prevent excess stormwater volumes from entering and overwhelming the storage swales and outlet. During construction, slope protection and compaction will be used along all cut/fill slopes and temporary disturbance areas. Permanent Seeding will be applied to all disturbed areas as well as final pad toes, swales, diversion ditches, and topsoil piles. Perennial vegetation increases soil infiltration rates and decreases sheet flow and movement of soil particles as compared to historic rates of the cultivated farmland and barren soil. This is due to increased surface cover, reduced soil compaction, and increased soil porosity. Seeding will be placed and crimped with straw for moisture retention which will aid in germination during the growing season. Outlet protection for the swale storage outlet pipe, including protection of the designated overflow spillway, will be installed as required. The Western Midstream access road and site monitoring program is used to ensure road and site conditions stay in compliance. Routine maintenance will ensure a safe and functioning project site. 5.0 SITE MAINTENANCE AND UPKEEP The Western Midstream site monitoring program ensures site conditions stay in compliance. Sedimentation, access road condition, vegetation health, and several other safety and maintenance items are routinely monitored and evaluated to ensure the site is in workable and drainable order. In addition to monitoring during regular operations, a formal monitoring plan has been developed for the project site. During the active construction period, the site will be inspected a minimum of every 14 calendar days as well as following any rain or snowmelt events that are able to cause surface erosion. After construction has finished, inspections will occur at a minimum of every 30 calendar days until the site is fully stabilized. Once the site is stabilized, inspections will occur annually. More frequent, informal inspections will continue to occur during routine operations and use of the site. Routine maintenance and required repairs of access roads, swales, ditches, berms, and the outlet will be handled by the operations team. Cleaning and removal of sediment and debris from the outlet, ditches, and swales as well as vegetation maintenance and specific manufacturer maintenance will also be handled by the operations team during regular operations and maintenance checks. 6.0 CONCLUSION The information and analysis presented in this report display the adequacy and effectiveness of the design and planning associated with the St. Vrain Laydown Yard Drainage and Erosion Control Plan. The design protects public health, safety, and general welfare and has no adverse impacts on public rights -of -way or off -site properties. Furthermore, the report demonstrates that the design adheres to Weld County Municipal Code as well as the Mile High Flood District (MHFD) Urban Storm Drainage Criteria Manuals. 2MJUSR21-14-0013 - St. vrain Laydown Yard - Final Drainage and Erosion Control Report Page 7 7.0 REFE • ENCES Detention Basin Design Workbook Version 4.03 (MHFD-Detentionj. May 2020. Mile High Flood District. https:,//mhfd.org/resources/soft are National Flood. Hazard Layer FIRMette. Federal Emergency Management Agency (FERIA). https : // msc.fema.gov/portal/home National Land Cover Database 2016. Multi -Resolution Land Characteristics Consortium (MRLC). https://www.mr1c.govidata NOAA Atlas 14 Point Precipitation Frequency Estimates: CO. National Oceanic and Atmospheric Administration. https://hdsc.nws.noaa.gov/hdse/pfds/pfds map cont.html?bkmrk=co Peak Runoff Prediction by the Rational Method Version 2.00 (UD-Rational). May 2017. Mile High Flood District ht •s://mhfd.org/resources/software The National Map Download Version 1.0. United States Geological Survey. https://apps.nationalmap.gov/download Urban Storm Drainage Criteria Manual: Volume 1 - Management, Hydrology, and Hydraulics. September 1969. Revised August 2018. Mile High Flood District. https://mhfd.org/resources/eriteria-manual Urban Storm Drainage Criteria Manual: Volume 2 - Structures, Storage, and Recreation. September 1969. Revised September 2017. Mile High Flood District. https://mhfd.org/resources/criteria-manual Urban Storm Drainage Criteria Manual: Volume 3 - Stormwater Quality. September 1992. Revised October 2019. Mile High Flood District. https://mhfd.org/resources/criteria-manual Web Soil Survey. Natural Resources Conservation Service. https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx Weld County Engineering and Construction Guidelines. April 2012. Revised July 2017. Weld County, Colorado. Weld County Municipal Code, Chapter 8, Article XI - Storm Drainage Criteria. July 2020.l Weld County, Colorado. Weld County Property Portal. Weld County, Colorado. https://www.co.weld.co.us/naps/propertyportal 2MJUSR21-14-0013 - St. drain Laydown Yard - Final Drainage and Erosion Control Report Page 18 APPENDICES 2MJUSR21-14-0013 - St. drain Laydown Yard - Final Drainage and Erosion Control Report Page 19 Ap endix A: Drainage and Erosion Contr 1 Plan UNION PACIFIC RAILROAD I 1 I I I 1 1 1 I 1 1 I 1 1 II PROPOSED ST. VRAIN LAYDOWN YARD COUNTY ROAD 19 COUNTY ROAD 19. mlier SURFACE OWNER: ANADARKO EFP COMPANY LP (PARCEL 120915200036) T03N _ SOIL STOCKPILE AREA R67W I COUNTY ROAD 34 EXISTING ST. VRAIN _ COMPRESSOR STATION 15 LOCATION MAP l00' COUNTY ROAD 21 COUNTY ROAD 32.5 ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN LOCATED IN SECTION 15, T3N, R67W, 6TH P.M. WELD COUNTY, COLORADO 2MJUSR27-14-0D73 I. 5 •"T US 85 US34 PROJECT SITE WELD] COUNTY ENGINEER'S CERTIFICATION "J HERESY CERTIFY THAT THIS FINAL PLAN FUR THE DRAINAGE DESIGN OF ST. VRAIN'LAYDOWN YARD WAS PREPARED FY ME OR UNDER MY DIRECT SUPER VISION) IN ACC `ORDA. F WITH THE PROVISIONS OF WELL) COUNTY MUNICIPAL CODE AND SUJ'PLLMEN'TAL REQUIREMENTS OF THE MILE HIGH FLOOD DISTRICT STORM DRAINAGE CRITERIA FOR THE OWNERS THEREOF." TYLER P. FRENCH REGISTERED PROFESSIONAL ENGINEER STATE OF COLORADO NO. 51566 VICINITY MAP PAGE INDEX 1 - COVER SHEET 2 - SITE OVERVIEW 3 - LAYDOWN YARD 4 - LAYDOWN YARD CROSS SECTIONS 5 - SOIL STOCKPILE 6 - STORAGE SCALE OUTLET 7 - SPILLWAY DETAILS 8 - OUTLET DETAILS 9 - BMP TYPICALS ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN CENERAL NOTES: 1. TI -US DRAIN ACE AND EROSION CONTROL PLAN WAS PREPARED FOLLOWING WELD COUNTY MUNICIPAL CODE AND DESIGN GUIDANCE PROVIDED BY MILE BiICN FLOOD DISTRICT. 2. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES. EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, PIPELINES, FLOW LINES, AND SETBACK REQUIREMENTS 3. ORIGINAL DOCUMENT SIZE: 71" X 17" LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80.538 Phone 970-776-4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming B280 Phone 307-6740609 Western Midstream COVER SHEET SCALE: VARIES JOB NUMBER: 20-66 DRAFTED BY: KIM PAGE: 1OF9 DATE: 7/14/21 REVISED: K:\A.NADARKat2.020\202.1._&6_TOP_GUM_T3N_kb7VJ SEC 15 -..DRAINAGE STUD4\CMG - DRAINAGE FL -VAST VRAIN_STORAGE_YARD_DP.rhvg, 7j151W21 4:56:31 Pk1, katy ST, VRAIN U CREEK y 4y `7 ira UNNAMED DITCH r I /--\ J \ /+, \ \ i 1 5' CONTOURS LEGEND EXISTING CONTOUR EXISTING IRRIGATION DITCH PROPOSED FENCE PROPOSED ACCESS ROAD STORMWATER DRAINAGE UNION PACIFIC FLOODPLAIN `m GONE A} GENERAL NOTES: 1. 2. SURFACE OWNER: ANADARKO E&P COMPANY LP (PARCEL 120915200036) EXISTING ROAD PROPOSED ACCESS ROAD DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, I'I !'ELI NES, FLOWLI NES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVDHH (GEOID12B). EXISTING ST. VRAIN COMPRESSOR STATION LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 COUNTY ROAD 34 UNNAMED DITCH l N •. "(2' COUNTY ROAD 32.5 Western Midstream BEEMAN DITCH ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN SITE OVERVIEW SCALE: 111 = 5001 JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: 20F9 DATE: 7/14/21 REVISED: ) L 1 ICEMAN STATE 32N-A16HZ WELL PAD (RECLAIMED) SW 10W 1' CONTOURS EEG END mew EXISTING CONTOUR EXISTING ROAD STORMWATER DRAINAGE PROPOSED CONTOUR PROPOSED ACCESS ROAD PROPOSED FENCE EXISTING WELL DIVERSION DITCH -EXISTING ROAD ]- 0.4% DITCH SLOPE PROPOSED DITCH CENTERLINE PROPOSED BERM PROPOSED CULVERT PROTECTION / RIPRAP 14 4 -YEAR STORMWATER STORAGE FOOTPRINT PROPOSED PERMANENT SEEDING EMERGENCY SPILLWAY GRADED AND GRAVELED LAYDOWN YARD (7.67 ACRES) GENERAL NOTES: 1. 2. 3. MAVERICK STATE 4G76HZ WELL PAD /(RECLAIMED) BERM l l (TO MAINTAIN V OF FREEBOARD) DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, PIPELINES. FLOW LINES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVDBB iGEOlD l2B). TOPSOIL STOCKPILE AND STORAGE SWALES WILL R1; SEEDED AND VEGETATED. ftURN-AROUND ACCESS ROAD LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80.538 Phone 970-776.4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming RZROI Phone 307-6740609 WESTERN _ , STORAGE SWALE UNDISTURBED //<i (NATIVE)-:i/r: STORAGE AREA Western Midstream 12" HOPE OUTLET PIPE GOOSE 39N -8H7 -- . WELL PAD (RECLAIMED) NORTHERN STORAGE SWALE TOMCAT [14 FACILITY ENTRANCE GATE PROPOSED ACCESS ROAD EXISTING ROAD ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN LAYDOWN YARD SCALE: 1" ' JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: 3OF9 DATE: 7/14/21 REVISED: K:\A.NADARK0,202U1t102E_&6_TOP_GUM_T3N_Rb7VJ SEC 15 -..DRAINAGE STUD4'DWG -DRAINAGE PL1M\ST VRA1N_,STORAGE_YARD_DP.dwg,7J15Pi 21 4:57:29 PM, katy 4800 4795 4790 C C C HORIZONTAL VERTICAL 0 ..--- 117.------ I EXISTING ROAD PROPOSED 100 -YEAR STORAGE ELEVATION 4794.02 TURN -AROUND ACCNS ROAD r TURN -AROUND ACCTS ROAD BERM —1\1/47/1\- --- A WESTERN STORAGE SWALE ACCESS ROAD -- ---1----L___ — V , , — _ „ -- -- ti e _ - S- \\ .\-1s. - - - - { -__ \ - - - , \ N , \ EXISTING GRADE 1/2\ 30' BOTTOM WIDTH 25' 50' - 1" = C0l 0 21-6" 5' 1"= J' 4800 4795 4790 C C C C C C C C C a C C CROSS SECTION Ain' C C FINISHED GRADE LAYDOWN YARD 100 -YEAR STORAGE ELEVATION 4794.02 TURN -AROUND ACCESS ROAD BERM (AT -GRADE) 3:1TRANSITION EXISTING GRADE 6' BOTTOM WIDTH ---- ------ NORTHERN STORAGESWALE C C N C C C C CROSS SECTION B -B' a C C C C 4800 4795 4790 C.sl C C 4800 4795 4790 4.4 C LEGEND EXISTING GRADE PROPOSED GRADE GENERAL NOTES: 1. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, I'I I'ELI NES, FLOWLI NES, AND SETBACK REQUIREMENTS. 2. ELEVATIONS ARE BASED ON NAVDMI (CEOID12B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN LAYDOWN YARD CROSS SECTIONS SCALE: VARIES JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: 4 OF 9 DATE: 7/14/21 REVISED: EXISTING ACCESS ROAD {r i 1' CONTOURS EEG END EXISTING CONTOUR EXISTING ROAD ter► STORMWATER DRAINAGE EXISTING FENCE EXISTING ST. VRAIN COMPRESSOR STATION X__ x x, x x X -X X 7S X EXISTING PHANTOM FACILITY EXISTING PHANTOM FACILITY GENERAL NOTES: 1. EXISTING SOIL STOCKPILE DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, PIPELINES. FLOWLINES, AND SETBACK REQUIREMENTS. 2. ELEVATIONS ARE BASED ON NAVDBB (GEOID I2B). RECLAIMED CONCRETE STORAGE AREA LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80.538 Phone 970-776.4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming RZR0I Phone 307-6740609 SOIL STOCKPILE AREA BOUNDARY RECLAIMED GRAVEL STORAGE AREA Western Midstream EXISTING POND ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN SOIL STOCKPILE SCALE: 1"=Ot' JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: SOF9 DATE: 7/14/21 REVISED: EDGE OF STORAGE SWALE ELEVATION 4793.05' ■ STORAGE SWALE / OUTLET PIPE INVERT ELEVATION 4792.17' 100 -YEAR STORAGE 5 -YEAR STORAGE TOP OF BERM ELEVATION 4795.07' b,)/\`' Ace\ ////\// / \ \j////\// /\ /P< /\\\ OUTLET PROFILE SCALE: NTS \\/< \ /\ 17jamj�°�',\ /</\\\>\\ \>;\); / /:/<�•.,�\/\.1j\/\i,. \//,k/\>>>>>>>/\\1\/\\\/ /\ //\„ \//\/\,�'/\//\//\/\ /7,/,*\\*/*/%/<\'\\\ \K*.< /\:\A\A\A\y<<\\ *\\ANx /// .\///1. \ \ \ \s /\\\.://\\\.\\\c:,, \ \/\/ \-1(:\\*.\\:\ N *1/4\ 7\NN >/// ///// N% \\\ \\sks \;\YC;\ %\s \\,/ EXISTING ROAD N. 10.5' \\\//ty A-\\//-\\///\///\/ \i/A//\//\\.////*\:/\\ ////\/\/\/\\\\. \\/\\ \\(//s\ <///a>\ -\\**//m/>7%>\ OUTLET ELEVATION 4791.92' K /A. /\\/\/�>\/ C/\jjjjjj\\% /,e//:\y\,\//c\\<< /&/\\ K.\\S\ //e\\//y\\\ \1/2\ /NW .*%/ 45' r Fa 30' BOLT -ON HDPE ANTI -SEEP COLLAR 12" HDPE PIPE GENERAL NOTES: 1. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINACE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON FXISTINC EASEMENTS, PIPELINES. FLOWLINES, AND SETBACK REQUIREMENTS. 2. ELEVATIONS ARE BASED ON NAVDBB (GEOID I2B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80.538 Phone 970-776-4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming B280 Phone 307-6740609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN STORAGE SWALE OUTLET SCALE: VARIES JOB NUMBER: 20-66 DRAFTED BY: KIM PAGE: 6OF9 DATE: 7/14/21 REVISED: PROPOSED TOPSOIL STOCKPILE / \/f /, Aty ��/\\/1, 100 -YEAR STORAGE ELEVATION 4794.02' 0.2% STORAGE SWALE SLOPE • *///\ \\/\/ ///\/,./.> KV\4/\.*NsN, s\> //NN, \/ //iv ////2 /\/// 100 -YEAR PEAK FLOW SPILLWAY SECTION SCALE: NTS \\*\//, ///\\\ //,s\ s\,/\ _ /_<\. \/*,-/./.\\/\,.\\. N/r /\/`♦///\//�\/\\/\♦ ♦ ♦ \ \ \ /♦\/♦/`\ \,/\/\\,/\/\/\, "4, //\/\\/�, /\/♦\\/\/,\/\/\f\ \/\/\/\/\/♦\/\\/\/\/♦' /`\/♦\/♦\/\,'`,`♦\/\\/\/♦\/\\/ \; //\\//♦//♦//\\//\//\,r♦//\/♦/,'`ff//\//,♦\/f\/♦/f♦//♦//\//♦,//♦//♦//\//\\//♦/♦f\/\//\/\,r\/\/♦,/s\,,/\/♦//,f \/,,♦/\♦/\\/♦f\♦/\♦/\♦/\♦/\\f\/\\/♦.4\4 f♦/\♦, .♦'\♦/\/♦/\♦/\♦/\♦/♦/\♦/\\/♦f\♦/♦/♦/\\/\♦f♦/\\/♦tx\s/♦f♦/N\ ti ♦/\/♦/♦/j♦//\/f\/,♦/, \//\,'\Y\//\//`' /,\//\//\//♦/r/\//\/,♦.,\//♦/\//♦//♦/j\/`.//,\7,�\/f\//\�f\//\/,♦,/j♦/.\/, >x//♦\ \ x// / � ♦�\♦�\♦1\\��\, �/� \� `\��\��.\�\ \\ \ \ \ / /&\ \: \\ ♦\ ♦\ \\ \� ti\ , \,/\\\ `♦\\ / /\ �\ /. /�. ///\//. "/\//\ /i\ / 28.00' SPILLWAY ELEVATION 4794.07' ,�, 0 0' MAVERICK STATE 4C-16HZ WELL PAD ELEVATION 4794.57' /\/\/\/\/\/X / / / !/ �'�, 1 !/ // / / / // >. \/\\\\.. / / \ / 414\\„ / f/ o---sw ,,,Ac4577- -c77: 4/<7% \x/Ncv \i/ \.,/ \y/s\5/1 \/,<\\*.\\... \/\\*Cs\><S5.s.,\/ /;',/\ A\ <\\> >2> K\KN \4\4\ \"/A4 \A‘i/\://c /•\\ \,/•\ ///////////////////////////////////////////////////////////// • SPILLWAY ELEVATION 4794.07' SPILLWAY PROFILE SCALE: NTS / // �/\//♦/♦\/♦\/\\/♦\//Xst\`//♦``//♦\/\\A\f✓\f/ ,i ./♦/\♦/\/\\/\♦/\\// %\ ' /\f\`./\'�/\\/\\/\♦f\♦; ///`›%/\\ // //\// //� // /'/ /\// /\,/ /\r\/\0/// �. , \ 1 \\\\ \\\\\\\ \ \/\ \ \\\ �/\\/ `\\ /\\/\\\\\\\;\\ /\\ \\�'\/ \ \\v/ v\, 1, f ..1, '/`/f\/ \////\///////'/'/\/♦//'\////'\'/♦f/\/f�'j//\//\//�///\////�// //♦ \\///N7\2:` . /\/\\/\\/\\/\\/\\/♦\/\`/\\j\\j\\j\\/\,/\/\\j\/\,♦/♦\/j\j\\/♦\/\\/\\j`�``/\\j` j\\/♦/♦/ \\ • \/\\/\/ /\//\//\/\/\//\/,/\//\//\//°�f/\f/\//\//\//\ff\/..\`/\// '/\f/\//\//\/\/\/\//\/�,/\/\f\�i ,/\. y/\\j/\,ff\\//\\\/\\,�\\////\\/\j/\�♦/f,\\//♦\/\//\/\\jf,\\//\\\//♦♦j/\\/�,\\/\\j/\♦//\\//\�\,/♦,�� \,, •%\/\\' \\\/\\' \\ NN//, \\\/\\/\/\\/\\\/♦` /\ \///\/♦//> /\`/\\/\/\\' \\ \?/, \\/,:\/\\/♦\:/ /\<\\/♦\/♦\/:11.\\/\\/\/\/\ ./ .//,,"</c\ /♦/♦//♦//♦/♦//\»/♦/♦//♦/\/f♦// /f\/\/j♦/♦//♦f.\//\sfic\y/;‘,& A. St\x/N 4, /2;;\ , \,f / \/./ \,//♦fj♦/♦/f♦/♦//♦//♦//♦/ , \/ //♦//\//\, f♦//`�/f♦/f\/j♦/f♦//♦/ • TOP OF BERM (TO MAINTAIN 1' OF FREEBOARD) EXISTING GRADE GENERAL NOTES: 1. 2. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINACE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, PIPELINES. FLOWLINES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVDBB (GEOID I2B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80.538 Phone 970-776.4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming BZROI Phone 307-6740609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN SPILLWAY DETAILS SCALE: VARIES JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: 70F9 DATE: 7/14/21 REVISED: LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970-776-4331 SHERIDAN OFFICE 1095 Saberton Avenue Sheridan, Wyoming RZROI Phone 307.674-0609 K�\E NADARKWD2D\2Q20 66 TOP_ GUN_T3N_R671V_SEC_15\DRAINAGE STUD YlDWG - DRAINAGE PLANSS7 VRAIN_STORAGE_YARD_DP dwg 7/15?2021 45338 PM katy Culvert TYPE A Nature grcutrd surface Roadbed Irislope 3-5% C Liven TYPE C Corn pouted Fill Culvert TYPE B --- Instep. a 2-5% f Du MS protection with rock llprap Roac bnd ;:7 — Ins:lope 3-5% Culvert NoT TO SCALE Culvert -— Arm In Wd ::: utticlalt Itargti ttiv�eel St N Mae, Maio rood sxoeprtg porfrencgottter Mta dralnega to tannin, aoc Yost and area ti datulbama hfet t a $$,ALE Intel peel at:lidn tel. needed Compacted Fill Anchor the slope drain pipe b the fill Sope with stakes, cable anchor blocks„ atle. Compacted Fil .odd riprao or ether slope protection Cutlet protection with rock riprsp tar,, Outlet protection with rock riprep ••�• -�. 4 V N- • .• .- • .......,5 Ei card arirprt 1 4. . bitted Mu 166 ,21 tho slope Fill 4 , C .Aaf prolach; Mr name. a. T biro ul fife r n%$Jnifs are alamwu Enerc cal Merl MOTTO Seal r Spacing II .CQ' t etweea ct vertu. Cu kart Fill wow - Place nutlet Inpe el nature ground Itt�.!al rIprap annoy Iha I'll malarial 010• - - Roads,ded.lch ti e Extend camel al I blast T• beyond the limit: ne a f to a roaraslos ditch Inlet pro-lectlm as needed Culvert rso Fel Diversion Ditch and Berm DD -1 Temporary Diversion Ditch and Berm NOTES: DIVERSION: S1 VALE SHALL SLOPE BETWEEN D-50% AND 8% TO A STAB-ILIZED OUTLET SUCH AS A SEDIMENT TRAP. ALL BERMS MUST BE FULLY COMPACTED SO THAT THERE IS NO LOOSE SOIL. Ih J . is \� f ' • F r. r•{ /// l �::{:= \..1. -s. . � F µ r• . r ••3n. • /7h.C/ 727 A /1/7?) - •F �r. a TENSIONING BAR � �'fiF., 1 - CHAIN LINK FENCE DETAIL SCALE: NTS 2 3/8" O.D. GALVANIZED POST CHAIN LINK FENCING EXISTING GRADE Temporary and Permanent Seeding (TS/PS) Table TS,{['S-I, Minimum Brill Seeding Rafts for Various Temporary ,Vnnuaal Grasses Species' Corntnon name) Growth Seasons Ponds of Putt Live Seed (PL acre Planting Depth finches) 1. Oats Cool 35 - 50 1 -2 2. Spring wheat Cool 25 - 35 I -.2 3. Spring barley COD' 25 - 35 1 -2 4 Annual ry cg ass Cool 10 - 15 l!°= 5. Millet Warm 3 - 15 % - 9.f4 6,. Sudangnss Warm 5-10 !A - % 7. Sorghum Warm 5—t0 .4 -314 8,. IA/inter wheat Cool 2045 1- 2 9. Winter barley Cool 20-35 1 -2 10. Winter rye Cool 20-35 1- 2 II. Triticate Coal 255--40 1 -2 ° Successful seeding of atuniul grass resulting in adequate plant growth will usually produce enough dead -plant residue to provide protection from wind and wales erosion for an additional year. This asstunes that the cover is notdisturbed or mowed closer than 8 inches. Hydraulic seeding may be substituted for drilling. only where slopes arc steeper than 3:1 or where access limitations exist. When hydraulic seeding is used, hydraulic mulching should be applied as a separate operation, when practical, to prevent the seeds from being encapsulated iii the mulch, s Irrigation, if consistently applied, may extend the use of cool season speoies during the minister inneaiFs. Seeding rates should be doubled if seed is. broadcast, or increased by 50 percent if dine using a Brillion Drill or by hydraulic see -ding. 1.3 DEED' DITCH (TYR) ST. VRAIN LAYDOWN YARD fRAINAGF ANl FRfSIfN C'fNTRfI PI AN GENERAL NOTES: LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 3071574.0609 Western Midstream BM P TYPICALS ICALS SCALE: VARIES JOB NUMBER: 20-66 DRAFTED BY: KMG PAGE: 9 OF 9 DATE: 7/14/21 REVISED: Ap endix B: Weld County Drainage Code Certificate of Compliance Weld County Drainage Code Certificate of Compliance Weld County Case Number: Parcel Number: 120915200036 Legal Description, Section/Township/Range: NW4 Si 5/T3N/RGIW _ Date: 7/14/2021 I Tyler French , Consultant Engineer for Western Midstream (Applicant), understand and acknowledge that the applicant is seeking land use approval of the case and parcel in the description above. I have designed or reviewed the design for the proposed land use set for in the application. I hereby certify, on behalf of the applicant, that the design will meet all applicable drainage requirements of the Weld County Code with the exception of the variance(s) described o ,exhibits. This certification is not a guarantee or warranty either expressed or implied. 01/4ID /..(cLF l�kr ri Engineer's Stamp: 7/14/2021 ' . f rge- le,e4yeir Engineer of Record Signature 1/4WONAL�rk Request q(IfApplicable) A liable) c I. 2. . Describe List Describe Demonstrate that result This the there variance design of the the the are project. hardship proposed that no criteria request adverse granting for of alternative the impacts is which of for Weld the the variance criterion County with from variance engineering stormwater found Code will is still being of in adequately which rationale runoff Section requested. a to variance which the protect 8-11-100 public supports is public being rights of the health, -of Weld requested. -way intent safety, County and/or of the and offsite Code. Weld general properties Two County welfare features Code. as and a of the proposed design deviate from this criterion. The proposed spillway is designed as a backwater, at - grade channel. A concrete cutoff wall extending below the spillway channel is not included in the proposed design since the at -grade spillway does not have risk of a blow-out or failure. The proposed outlet pipe is designed with HDPE anti -seep collars. Concrete anti -seep collars were not included in the proposed design since HDPE collars achieve the same results and are available and commonly used at other oil and gas sites for detention outlets. The proposed design variances will not lead to negative impacts on public safety or public infrastructure and are not contrary to the intent and general purpose of the criteria presented in Weld County Code. Public Works Director/Designee Review Of Applicable) Public Works Director/Designee Name Date of Signature Signature Approved ❑ Denied Comments: Department of Public Works Development Review 1111 H Street, Greeley, CO 80631 I Ph: 970-304-6496 www.weldgov.com/departments/public_works/development review 08/02/2019 Appendix C: NRCS Web Soil Survey - Soils Report 40° 14'6"N 40° 13' 24" N 104° 53' 13"W 8 A Hydrologic Soil Group —Weld County, Colorado, Southern Part (St. Vrain Laydown Yard) 510000 510000 Map Scale: 1:6,190 if printed on A portrait (831 x 11") sheet. Meters 0 50 100 20D 300 510100 510100 510200 510200 Feet 0 300 600 1200 1800 Map p --lion : Web Mercator Corner coordinates: WGSS4 Edge tics: UTM Zone 13N WG584 510300 510300 510400 510400 510500 104° 52' 33" W 1040 52' 33" W 40° 14'6"N 40° 13' 24" N USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 1/21/2021 Page 1 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part (St. drain Laydown Yard) MAP LEGEND Area of Interest (AOI) O C Area of Interest (AOl) 1:24,000. D CID Soi is Soil Rating Polygons n A I A/D B B/0 C C{0 0 Not rated or not available Soil Rating Lines fora oirco A/D prasso prisisso B BID C ,�• C!D D • Not rated or not available Soil Rating Points 0 0 ■ ■ A AID B B/0 m 0 0 Not rated or not available Water Features Streams and Canals Transportation . Rails sarao Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography MAP IN FORMATION The soil surveys that comprise your AOI were mapped at Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Southern Part Survey Area Data: Version 19, Jun 5, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 19, 2018 —Aug 10, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources a Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2021 Page 2 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part St. Vrain Laydown Yard Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Altman loam, percent slopes 0 to 1 B 33.6 22.0% 41 Nunn clay loam, percent slopes Oto 1 C 86.7 56.8% 46 Olney fine 0 to 1 sandy loam, percent slopes B 2.9 1.9% 69 Talent sand, percent slopes 0 to 3 A 29.3 19.2% Totals for Area of Interest 152.6 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID, BID, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas.Only the soils that in their natural condition are in group D are assigned to dual classes. USDA Natural Resources Web Soil Survey r Conservation Service National Cooperative Soil Survey 1/21/2021 Page 3 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part St. Vrairl Laydown Yard Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie -break Rule.- Higher USDA. Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 1/21/2021 Page 4 of 4 Appendix D: FEMA Flood Insurance Rate Map FIRMette National Flood Hazard Layer FIRMette FEMA Legend 104°53'15"W 40413'59"N 0 250 500 11000 1, 500 2,000 t6,00►0 104°52'38"W 40413'31"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) eA,tiA99 With BFE or Depth Zone AE, A{}, AR, yE, AR Regulatory Floodway OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Future Conditions 1% Annual Chance Flood Hazard Area with Reduced Flood Risk due to Levee. See Notes. zone X Area with Flood Risk due to Levee Zone D NO SCREEN Area of Minimal Flood Hazard zonex I I I I I I I 20.2 Effective LOMRs Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Base Flood Elevation Line (BFE) Limit of Study Jurisdiction Boundary Coastal Transect Baseline Profile Baseline Hydrographic Feature Digital Data Available No Digital Data Available Unmapped N The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FE MA. This map was exported on 12/4/2020 at 4:15 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. A pendx E: NOAH Atlas 14 Point Precipitation Frequency Estimates 1/12/2021 Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Platteville, Colorado, USA* Latitude: 40.229°, Longitude: -104.8823° Elevation: 4796.27 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF tabular PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) Duration ,JI 1 2 5 I 1 0 25 50 100 200 500 1000 5 -min 0.234 (0.183-0.301) 0.283 (0.221-0.365) 0.380 (0.295-0.491) 0.477 (0.368-0.61 ►) 0.633 (0.483-0.883) 0.772 (0.570-1.08) 0.927 (0.660-1.33) 1.10 (0.751-1.63)i 1 1.36 (0.889-2.06) 1.57 (0.992-2.38) . 10 -min 0.343 0.415 (0.323-0.534) 0.557 (0.433-4.719 f 0.698 (0.539-0.906 0.927 (0.708-1.29) 1.13 (0.835-1.59) 1.36 (0.967-1.95) 1.61 (1.10-2.38) 2.30 (1.45-3.49) 15 -min 0.418 (0.326-0.538) 0.506 (0.394-0.651) 0.679 (0.528-0.877) 0.852 (0.657-1.11) 1.13 (0.863-1.58j 1.66 I (1.18-2.38) 1.97 (1.34-2.91) 2.42 (1.59-3.68) 2.80 (1.77-4.26) 30 -rain 0.562 (0.439-0.723) 0.678 (0.528-0.873) 0.908 (0.705-1.17) 1.14 (0.878-1.48) 1.51 (1.15-2.11) 1.84 (1.36-2.59) 2.21 1 (1.58-3.19) 2.63 (1.80-3.89) 3.25 (2.13-4.93) 3.76 (2.38.5.72) 60 -ruin 0.692 (0.540-0.890) 0.827 (0.645-1.07) 1.10 (0.857-1.43) 1.39 (1.07-1.80) 1.85 (1.42-2.59) 2.27 (1.68-3.19) 2.74 (1.95-3.95) 3.27 (2.23-4.84) 4.05 (2.66-6.16) 4.71 (2.98-7.16) 2 -hr 0.822 (0.647-1.05) 0.977 (0.769-1.24) 1.30 (1.02-1.66) 1.63 (1.27-2.09) 2.19 (1.69-3.03) 2.69 (2.01-3.74) 3.26 (2.35-4.64) 3.90 (2.70-5.71) 4.86 (3.22-7.30) 5.66 (3.62-8.50) 3 -hr 0.897 (0.710-1.13) 1.06 (0.838-1.34) 1 1.40 (1.11-1.78) 1.76 (1.38-2.24) 2.36 (1.84-3.25) 2.90 (2.19-4.02) 3.52 (2.56.4.99) 4.23 (2.94-6.14) 5.27 (3.52-7.86) 6.15 (3.96-9.16) 6-hrI 1.06 (0.848-1.32) 1.247 (0.992-1.55) 2.01 (1.60-2.54) 2.67 ► (2.10-3.63) 3.27 (2.49-4.46) 4.71 (3.31-6.75) 5.85 (3.95-8.60) 6.81 (4.43-9.99) 1.26 (1.02-1.56) 1.50 (1.21-1.85) 2.37 _ (1.90-2.95) 3.07 (2.42-4.07) 3.67 (2.81-4.91) 4.35 (3.21-5.95) 5.10 (3.61-7.16) 6.1 (4.21-8.93) 7.10 (4.67-10.3) 24 -hr 1.51 (1.23-1.84) 1.79 (1.46-2.18) 2.30 (1.87-2.82) 2.78 (2.24-3.41) 3.51 (2.78-4.55) 4.13 (3.18-5.41) 4.81 (3.58-6.45) 5.55 (3.96-7.65) 6.61 (4.53-9.36) 7.47 (4.97-10.7) 2 -day 1.73 (1.43-2.09) 2.08 (172-2.51) 2.69 (2.21-3.25) 3.22 (2.63-3.91) 4.00 (3.18-5.08) 4.64 (3.60-5.96) 5.31 (3.98-6.99) 6.03 (4.33-8.15) 7.03 (4.86-9.77) 7.82 (5.26-11.0) 3 -day 1.89 (1.57-2.27) 2.25 (1.86-2.69) 2.86 (2.36-3.43) i 4.19 (3.35-5.27) 4.84 (3.77-6.16) 5.52 (4.16-7.20) 6.24 (4.51-8.37) 7.25 (5.05-9.99) 8.05 (5.45-11.2) 4 -day 2.02 (1.69-2.40) 2.38 (1.98-2.83) 2.99 (2.48-3.58) 3.54 (2.924.24) 4.33 I (3.48-5.42) I 4.99 i(3.91.6.31) 5.67 I (4.29-7.36) 6.40 (4.65-8.53) 7.42 (5.19-10.2) 8.23 (5.59-114) 1 117-day2.31 (1.94-2.72) 2.70 (2.27-3.19) 3.37 (2'.82-3.98) 3.95 (3.28-4.69) 4.77 l (3.86-5.88) 5.44 (4.29-6.79) 6.13 l (4.67-7.84) 6.85 (5.01-9.00) i 7.84 (5.52-10.6) 8.61 (5.91-11.8) ,14 -dad, 2.56 (2.16-2.99) 2.99 (2.52-3.50) 3.70 (3.11-4.35) 4.31 (3.60-5.08) w 5.16 (4.18-6.30) R 5.84 (4.62-7.22) t 6.53 (5.00-8.27) 7.24 (5.32-9.42) 8.21 (5.81-11.00 8.95 (6.18-12.2) 20 -day 3.27 (2.79-3.78) 4.58 (3.90-5.31) 5.26 (4.45-6.12) 6.19 (5.06-7.42) 6.91 (5.52-8.40) 7.62 (5.90-9.49) 8.35 (620-10.7) 1 9.31 (6.66-12.2') 10.0 7.00-13.4 30-day3.83 (3.29-4.39) 4.39 (3.77-5.05) 5.3'1 6.06 1 (5...16-7.00) 7.07 (5.81-8.39) 7.85 (6.31-9.45) 8.61 1 (6.70-10.6) 9.37 (7.00-11.9) i 10.4 (7.46-13.5) 11.1 (7.80-14.7) 45 -day 4.51 (3.90-5.13) 5.18 (4.47-5.90) 6.25 (5.38-7.14) i 7.11 (6.09-8.16) 8.27 (6.83-9.72) 9.14 (7.39-10.9) 9.98 (7.80-12.2) 10.8 (8.12-13.5) 11.9 (8.59-15.3) 12.6 (8.94-16.6) 5.05 (4.39-5.73) 5.83 (5.06-6.61) 7.07 (6.11-8.03)1; y 9.35 (7.75-10.9) 10.3 (8.37-12.2) 12.1 (9.15-15.1) 13 3 14.1 (9.99-18.3) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical https://hdscsnws.noaa.govlhdsclpfds/pfds_printpage.html?Iat=40.2290&Ian=-104.8823&data=depth&units=english&series=pds 1 k4 1/12/2021 Precipitation Frequency Data Server PDS-based depth -duration -frequency (DDF) curves Latitude: 40.2:290°, Longitude: -104.8823° cZ i 4J ra 0 a l C O 4J CL 16 14 12 10 8 6 16 14 .C E in C 5 10 25 50 100 200 NOAA Atlas 14, Volume 6, Version 2 C L. Duration csti A ni ' 6 H Average reLurrertce interval (years) i ra fa rti t 6 6 Ln 0- 61 f set ,c 500 1000 Created (GMT) : Tue Jan 12 15:58:25 2021 Back to Top Maps & aerials Small scale terrain varage recurrence interval years) 1 2 5' 10 25 50 100 200 5O0 1000 DJur"ationn. 5 -wan 10 -min 1 !--rein 3 -rain 6 0-rnon 2-mr 3 -hr 6-IIl r 12-h r 24 -hr -day. 3Aay 4 -day 7 -day 10 -day. 20 -day 30 -day 45 -day 60 -day, https://hdsc nws.noaa.govlhdsclpfds/pfds_printpage.html?lat=40.2290&Ian=-1 Q4.8823&data=depth&units=english&series=pds 2/4 1/12/2021 Precipitation Frequency Data Server unt.J Rd .. _ Platt f r 3km 2mi l (� Large scale terrain Large scale map it Ts'e •, 100km I gy�� y s C m •751 sr — Large scale aerial https://hdscsnws.nvaa.gov/hdsc/pfds/pfds_printpage.html?lat=4O.2290&Ian=-1 Q4.8823&data=depth&units=english&series=pds 3/4 1/12/2021 Precipitation Frequency Data Server Back to Top Fort Colt rnE= US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer https://hdsc.nws.noaa.gov/hdsclpfds/pfds_printpage.html?lat-4{x.2290&Ion=-104.8823&data-depth&units=english&series=pds 4/4 Appendix F: UD-Rational Spreadsheet Calculations Calculation of Peak Runoff using Rational Method Designer: Company: TPF 609 Consulting Date: 214/2021 Project Location: St. Wain Laydown Yard Version 2.00 released May 2017 Cells of this color are for required user -input Cells of this color are for optional override values Cells of this color are for calculated results based on over ti ` sia33 0.395(1.1 — Cs3� __ lit Lit 601C.,/ St 60Vt Computed tc = tr + tc Lit Regionaltc=(26-171)+ 60(141 + 9) titrinimain= 5 (urban) tminimun,= 10 (non -urban) Selected tc = max(tminimum , min(Computcd tc , Regional t,)) Select UDFCD location for NOAA Atlas 14 Rainfall Depths from the pulidown list OR enter your own depths obtained from the NOAA website (click this link) 1 -hour rainfall depth, P1 (in)= Rainfall intensity Equation Coefficients= 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 500-yr 0.827 I 1.10 1.39 1.85 I 227 2.74 a b C 28.50 I 10-00 0-7816 t(in/hr) = (b+tfc Q(c'f s) = CIA Subcatchment Name Area (ac) NRCS Hydrologic Soil Group Runoff Coefficient, C Overland (Initial) Flow Time Channelized (Travel) Flow Time Time of Concentration Rainfall Intensity, I (inthr) Peak Flow, 4 (cfs) Percent Imperviousness 2-yr 5-yr 10-yr 25-yr 59-yr 100-yr 500-yr Overland Flow Length L, (ft) U/S Elevation (ft) (Optional) DOS Elevation (ft) (Optional) Overland Flow Slope S; (ftlft) Overland Flow Time t; (min) Channelized Flow Length L. (ft) WS Elevation (ft) : r aal CIS Elevation (ft) lc r onal) Channelized Flow Shope S; (ftfft) NRCS Conveyance Factor K Channelized Flow Velocity V, (ft/sec) Channelized Flow Time t, (min) Computed tt[min) Regional I (min) Selected t (min) 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 500-yr 2-yr Syr 10-yr 25-yr 50-yr 100-yr 500-yr Laydown Yard Historic 16.11 C 2.0 0.01 0.05 0.15 0.33 0.40 0.49 0.59 500 0.002 72.01 3"C 0.003 10 0.55 9.43 81.44 35.82 35.82 1.17 1.55 1.96 2.61 3.20 3.86 0.2 1.3 4.6 13.9 20.8 30.6 0.06 0.16 0.26 0.38 0.45 0.51 64.55 73.98 73.98 0.72 0.96 1.22 1.62 1S9 2.40 0.7 2.5 5.1 9.9 14.4 19.7 0.15 0.21 0.29 0.44 D.50 0.57 0.66 47.37 66.75 38.52 38.52 1.11 1.48 1.87 2.49 3.06 3.69 2.7 5.0 8.7 17.6 24.6 34.0 0.18 0.27 0.35 0.45 0.50 0.55 44.38 63.76 3.2 6.3 10.4 17.9 24.8 32.9 0.01 0.05 0.15 0.33 0.40 0.49 0.59 Soil Stockpile Area - Historic 6.67 C 2.0 500 0.004 0 0.004 10 0.63 0.00 57.29 57.29 25.66 25.66 1.42 1.89 2.39 3.18 3.90 4.71 D.1 0.6 2.3 7.0 10.5 15.4 0.06 0.16 0.26 0.38 0.45 0.51 51.35 51.35 51.35 0.93 1.23 1.56 2.07 2.54 3.07 0.4 1.3 2.7 5.3 7.6 10.4 Soil Stockpile Area - Proposed 6.67 C 2.0 0.01 0.05 0.15 0.33 0.40 0.49 0.59 500 0.006 50.11 280 0 006 10 0.77 6-02 56.14 32-15 32.15 1.25 1.66 2.09 2.79 3.42 4.13 D.1 0.6 2.0 6.1 9.2 13.5 0.06 0.16 0.26 0.38 0.45 0.51 44.92 50 94 50.94 0.93 1.24 1.57 2.08 2.56 3.09 0.4 1.3 2.7 5.3 7.7 10.5 Appendix G: MHFD-Detention Spreadsheet Calculations DETENTION BASIN STAGE -STORAGE TABLE BUILDER MYFD-Detention, Version 4.03 (May 020) Project: St. grain Laydown Yard Basin II}: Laydown Yard - Proposed "'ONE 4 .ZONC2 IUF:YR 1 vouimi BaRi j WQCV - ,F f ION E At(D 2 r 01Slt4NCh1T Ca RC ES F'O3L I, fOMFw F ti Example Zone Configuration (Retention Pond) Watershed Information Flood Control Only Selected BMP Type = Watershed Area = Watershed Length = Watershed Length to Centroid = Watershed Sope = Watershed Imperviousness = Percentage Hydrologic Soil Group A = Percentage Hydrologic Soil Group B = Percentage Hydrologic Sal Groups C/D = Target WQCV Drain Time = Location for 1 -hr Rainfall Depths = User Input No BMP 16.11 930 500 0.002 21.40% 0.0% 0.0% 100.0°/0 40.0 acres ft ft ft/ft Flat Slope c 0.005 (tiff percent percent percent percent hours After providing required inputs above induding 1 -hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure. Water Quality Capture Volume (WQCV) = Excess Urban Runoff Volume (EURV) = 2-yr Runoff Volume (P1 = 0.83 in.) = 5-yr Runoff Volume (P1 = 1.1 in.) = 10-yr Runoff Volume (P1 = 1.39 in.) = 25-yr Runoff Volume (P1 = 1.85 in.) = 50-yr Runoff Volume (P1 = 2.27 in.) = 100-yr Runoff Volume (P1 = 2.74 in.) = 500-yr Runoff Volume (P1 = 4.05 in.) = Approximate 2-yr Detention Volume Approximate 5-yr Detention Volume Approximate 10-yr Detention Volume Approximate 25-yr Detention Volume Approximate 50-yr Detention Volume Approximate 100-yr Detention Volume Define Zones and Basin Geometry Zone 1 Volume (100 -year) Select Zone 2 Storage Volume (Optional) Select Zone 3 Storage Volume (Optional) Total Detention Basin Volume Initial Surcharge Volume (ISV) Initial Surcharge Depth (ISD) Total Available Detention Depth (Htotal) Depth of Trickle Channel (I-+rc) Sope of Trickle Ctannel (STc) Slopes of Main Basin Sides (Strain) Basin Length -to -Width Patio (R1,,,k,) Initial Surcharge Area (Ars;,) Surcharge Volume Length (L7s ) Surcharge Volume Wdth Depth of Basin Floor (HRooft) Length of Basin Floor (Lac, ) _ Width of Basin Floor (WRc,) Area of Basin Floor (Aaccn) = Volume of Basin Floor (VRcen) _ Depth of Main Basin (Hrt41N) _ Length of Main Basin (Lr.1 IN) _ Width of Main Basin (Wht=urr) _ Area of Main Basin (Artsura) _ Volume of Main Basin (Vr.1Arra) Calculated Total Basin Volume (Metal) _ 0.163 0.305 0.180 0.359 0.674 1.359 1.924 2.651 4.530 0.179 0.345 0.446 0.600 0.685 0.945 0.945 0.945 N/A N/A user user user user user user user user user user user user user user user user user user user acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet ft: R ft ft ft/ft H:V ft R ft ft ft ft ft ft ft ft ft ft` ft acre-feet Optional User Oerrides acre-feet acre-feet inches inches inches inches inches inches inches 0.827 1.10 1.39 1.85 2.27 2.74 4.05 Depth Increment = ft Stage - Storage Description Stage (ft) Optional Override Stage (It) Length (ft) 4lridth (ft) Area (ft `) Optional Override Area I ft `) Area (acre) Volume (ft) Volume (ac -It) Media Surface -- 0.00 -- -- -- 0 0.000 -- 0.05 -- -- -- 664 0.015 16 0.000 -- 0.10 -- -- -- 2,065 0.047 84 0.002 -- 0.15 -- -- -- 2,535 0.058 199 0.005 -- 0.20 -- -- -- 3,981 0.091 324 0.007 -- 0.25 -- -- -- 4,502 0.103 574 0.013 -- 0.30 -- -- -- 5,990 0.138 837 0.019 -- 0.35 -- -- -- 6,564 0.151 1,151 0.026 0.40 -- -- -- 8,094 0.186 1,517 0.035 -- 0.45 -- -- -- 8,715 0.200 1,851 0.042 -- 0.50 -- -- -- 10,291 0.236 2,412 0.055 0.55 -- -- -- 10,959 0.252 2,944 0.068 -- 0.60 -- -- -- 12,582 0.289 3,532 0.081 -- 0.65 -- -- -- 13,299 0.305 4,179 0.096 0.70 -- -- - 14,968 0.344 4,738 0.109 -- 0.75 -- -- -- 15,582 0.358 5,649 0.130 -- 0.80 -- -- -- 17,137 0.393 6,467 0.148 0.85 -- -- -- 17,782 0.408 7,340 0.169 -- 0.90 -- -- -- 19,724 0.453 8,278 0.190 -- 0.95 -- -- -- 20,989 0.482 9,087 0.209 1.00 -- -- -- 23,239 0.533 10,402 0.239 -- 1.05 -- -- -- 24,335 0.559 11,591 0.266 -- 1.10 -- -- -- 27,771 0.638 12,894 0.296 1.15 -- -- -- 32,921 0.756 14,411 0.331 -- 1.20 -- -- -- 37,135 0.852 15,795 0.363 -- 1.25 -- -- -- 43,131 0.990 18,169 0.417 1.30 -- -- -- 50,925 1.169 20,520 0.471 -- 1.35 -- -- -- 63,331 1.454 23,376 0.537 -- 1.40 -- -- -- 69,851 1.604 26,706 0.613 -- 1.45 -- - -- 80,341 1.844 30,460 0.699 -- 1.50 -- -- -- 85,992 1.974 34,619 0.795 -- 1.55 -- -- -- 98,938 2.271 39,242 0.901 1.60 -- -- -- 108,227 2A85 44,421 1.020 -- 1.65 -- -- -- 119,454 2.742 50,113 1.150 -- 1.70 -- -- -- 126,603 2.906 56,264 1.292 1.75 -- - - 135,920 3.120 62,827 1.442 -- 1.80 -- -- -- 142,532 3.272 69,788 1.602 -- 1.85 -- -- -- 154,379 3.544 77,211 1.773 1.90 -- -- - 157,520 3.616 85,009 1.952 -- 1.95 -- -- -- 167,681 3.849 93,138 2.138 -- 2.00 -- -- -- 170,249 3.908 101,587 2.332 2.05 -- -- -- 178,980 4.109 110,317 2.533 -- 2.10 -- -- -- 183,114 4.204 119,370 2.740 -- 2.15 -- -- -- 188,325 4.323 128,656 2.954 2.20 -- -- - 195,007 4.477 138,239 3.174 -- 2.25 -- -- -- 199,689 4.584 148,106 3.400 -- 2.30 -- -- -- 203,968 4.682 158,198 3.632 2.35 -- -- -- 209,569 4.811 168,536 3.869 -- 2.90 -- -- -- 299,456 6.875 308,518 7.083 MHFD-Deten ion_v4 03_ST VRAIN.xsrn, Bas n / 7:1 1_:03 P1/ DETENTION BASIN STAGE -STORAGE TABLE BUILDER MHFD-Detention, Version 413 (May 2020) 20 15 5 0 0.00 1.00 2.00 Stage (ft) — Length Ott) — Width {ft) Area (sq.ft.) 3.00 4.00 299600 224700 149800 - N 74900 0 6.880 5.160 In U a 3.440 sec L720 0-000 a /r ode X 0.00 1.00 2.00 Stage (ft.) Area (acres) — Volumeat- ft) 3.00 7.100 5.325 1375 0-000 4.00 MHFD-Deten"an_v4 03_ST VRAIN.xsm, Bas n 1/22/2021, 12:03 PM DETENTION BASIN OUTLET STRUCTURE DESIGN MHFD-Detention, Version 4,03 (May 2020) Project: St. Vrain Laydown Yard Basin ID: Laydown Yard - Proposed 1 AAY.VR VOLUME EURV WOcY T I PERMANENT— } POOL ZONE -ZONE 2 [L'JNL1 -- n - ZONE 1 AND 2'1 ORIFICES -1©0-YEAR ORIFICE Example Zone Configuration (Retention Pond) Zone 1 (100 -year) Zone 2 Zone 3 User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) ft (distance below the filtration media surface) inches Underdrain Orifice Invert Depth = Underdrain Orifice Diameter = N/A N/A Estimated Stage (ft) Estimated Volume (ac -ft) Outlet Type 1.57 0.945 Circular Orifice Total (all zones) 0.945 Underdrain Orifice Area = Underdrain Orifice Centroid = Calculated Parameters for Underdrain N/A N/A ft2 feet User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Invert of Lowest Orifice = Depth at top of Zone using Orifice Plate = Orifice Plate: Orifice Vertical Spacing = Orifice Plate: Orifice Area per Row = N/A N/A N/A N/A ft (relative to basin bottom at Stage = 0 ft) ft (relative to basin bottom at Stage = 0 ft) inches inches User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest' Stage of Orifice Centroid (ft) Orifice Area (sq. inches) Stage of Orifice Centroid (ft) Orifice Area (sq. inches) WQ Orifice Area per Row = Elliptical Half -Width = Elliptical Slot Centroid = Elliptical Slot Area = Calculated Parameters for Plate ft2 feet feet ft2 N/A N/A N/A N/A Row 1 (optional) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A Row 9 (optional, Row 10 (optional) Row 11 (optional, Row 12 (optional, Row 13 (optional) Row 14 (optional) Row 15 (optional; Row 16 (optional, N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A User Input: Vertical Orifice (Circular or Rectangular) Invert of Vertical Orifice = Depth at top of Zone using Vertical Orifice = Vertical Orifice Diameter = Zone 1 Circular Not Selected 0.00 4.00 12.00 ft (relative to basin bottom at Stage = 0 ft) ft (relative to basin bottom at Stage = 0 ft) inches Vertical Orifice Area = Vertical Orifice Centroid = Calculated Parameters for Vertical Orifice Zone 1 Circular Not Selected 0.79 0.50 ft2 feet User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir (and No Outlet Pipe) Overflow Weir Front Edge Height, Ho = Overflow Weir Front Edge Length Overflow Weir Grate Slope = Horiz. Length of Weir Sides = Overflow Grate Open Area % = Debris Clogging % = Not Selected Not Selected ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = feet Overflow Weir Slope Length = H:V Grate Open Area / 100-yr Orifice Area = feet Overflow Grate Open Area w/o Debris = %, grate open area/total area Overflow Grate Open Area w/ Debris = 0/ User Input: Outlet Pipe wif How Restriction Plate (Circular Orifice, Restrictor Plater or Rectangular Orifice) Depth to Invert of Outlet Pipe = Circular Orifice Diameter = Not Selected Not Selected User Input: Emergency Spillway (Rectangular or Trapezoidal) Spillway Invert Stage= Spillway Crest Length = Spillway End Slopes = Freeboard above Max Water Surface = 1.90 20.00 4.00 0.50 ft (distance below basin bottom at Stage = 0 ft) inches ft (relative to basin bottom at Stage = 0 ft) feet H:V feet Calculated Parameters for Overflow Weir Not Selected Not Selected feet feet ft2 ft2 Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate Outlet Orifice Area = Outlet Orifice Centroid = Half -Central Angle of Restrictor Plate on Pipe = Spillway Design Flow Depth= Stage at Top of Freeboard = Basin Area at Top of Freeboard = Basin Volume at Top of Freeboard = Not Selected Not Selected N/A N/A Calculated Parameters for Spillway 0.50 2.90 6.87 7.08 feet feet acres acre -ft ft2 feet radians Routed Hydrocraph Results Design Storm Return Period = One -Hour Rainfall Depth (in) = CUHP Runoff Volume (acre -ft) _ Inflow Hydrograph Volume (acre -ft) = CUHP Predevelopment Peak Q (cfs) = OPTIONAL Override Predevelopment Peak Q (cfs) _ Predevelopment Unit Peak Flow, q (cfs/acre) = Peak Inflow Q (cfs) = Peak Outflow Q (cfs) = Ratio Peak Outflow to Predevelopment Q = Structure Controlling Flow = Max Velocity through Grate 1 (fps) = Max Velocity through Grate 2 (fps) _ Tme to Drain 97% of Inflow Volume (hours) Tme to Drain 99% of Inflow Volume (hours) = Maximum Pending Depth (ft) = Area at Maximum Ponding Depth (acres) = Maximum Volume Stored (acre -ft) = The user can override the default CL/HP hvdrograohs and runoff volumes by entering new values in the Inflow Hvdrograohs table (Columns W through Al). WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year N/A N/A 0.83 1.10 1.39 1.85 2.27 2.74 4.05 0.163 0.305 0.180 0.359 0.674 1.359 1.924 2.651 4.530 N/A N/A 0.180 0.359 0.674 1.359 1.924 2.651 4.530 N/A N/A 0.1 1.1 3.6 9.8 14.3 20.0 34.2 N/A N/A 5.1 N/A N/A 0.01 0.07 0.23 0.61 0.89 0.32 2.13 N/A N/A 1.5 3.1 5.8 12.3 17.0 23.1 38.3 1.9 2.9 0.8 1.6 2.8 3.7 4.1 4.4 12.1 N/A N/A N/A 1.4 0.8 0.4 0.3 0.9 0.4 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Spillway N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 3 3 5 5 5 6 7 9 11 4 4 5 5 6 7 8 10 12 0.84 1.12 0.53 0.76 1.05 1.47 1.66 1.85 2.14 0.41 0.68 0.24 0.36 0.56 1.87 2.74 3.54 4.28 0.164 0.309 0.060 0.133 0.266 0.718 1.150 1.773 2.868 MHFD-Detention v4 03 ST VRAIN.xlsm, Outlet Structure -1/2212021, 12:03 PM DETENTION BASIN OUTLET STRUCTURE DESIGN MH'FD-Detention, Version 4.00 (December 2019 FLOW [cis] cn tin tin on s - - ® SOOYRIN - - - 500YR OUT - 100YR IN - - 100YR OUT - SOYR N - - - SOYA OUT - 25YR IN - 25YR OUT - e 10YR IV - _ - - 10YR OUT - SYR IN - - - 5YR OUT - ! 2YR IN - - ® 2YR OUT EURV IN - - 4. ELM OUT - WOO/ IN — — WOCV OUT vo oft ` - a—~ . i. ti a - - . — — . — —. — „ f - .f — — .r ti,, I 3 ^ yy _ =-' 4-=:. - - - _ 0 r�l 0.1 1 110 TIME [hr] 2.5 500YR 100YR 50YR 2SYR 2 — 10YR SYR 2YR — EURV WQCV t' i c PONDING DEPTH If i 11;111 ll'hh‘ A rioldi r ti fI , IOppip„ ki 0.1 1 10 100 DRAIN TIM (1w] - 80 304,000 User Area Interpolated [ftA2] Area [ftA2] -0z� 250,000 Summary Area [ftA2] Volume [ft^3] —+1P- Summary Outflow Vol u.me [ft^3] - 60 200,000 [cfs] _,_,•-- _ Summary Outflow [cfs] 1 - 5b' cn 10,000ti 'r r.' � 7' U - 40 Di 3 Or'� 000 104,000 J --a u_ 30 0 u W d 1 : -1 1 - 20 50,000 -) - 10 r• .-, 0 i.1. _ 0 0.00 0,50 1.00 1.50 2.00 2.50 3400 3,50 4,00 PON DING DEPTH (t] S -A -V -D Chart Axis Override minimum bound maximum bound X-axis Left V -Axis Right V -Axis MHFD-Detention v4 03_ST VRAIN.xlsm, Outlet Structure 1/22/2021, 12:03 PM Appendix H: Pipe Buoyancy Calculations Buoyancy Calculations for Outlet Pipes 12" HDPE Pipe Ww — eir÷4)*(BcA2)*y 1.17 Bc = outside pipe diameter (feet) 62.42 y = unit weight of fresh water (pounds per cubic foot) 67.11 Ww = weight of displaced water (pounds per linear foot) Wt = -p 8.26 Wp = weight of pipe (pounds per linear foot) 58.85 Wt = resultant buoyant force of the submerged pipe (pounds per linear foot) Hi = (FS*Wt+Wi*Bc)_(O.1073*Bc) 68.0 Wi = average unit weight of inundated backfill (pounds per cubic foot) 1.5 FS = factor of safety 0.98 Hi = minimum depth of inundated backfill required above top of pipe (feet) INPUT CALCULATED * Assumes all backfill is inundated * Does not account for added weight from anti -seep collars Appendix I: Conveyance Calculations for Swale and Ditch Design Grass Swale (Typical) T ele yn F B Estimated Conveyance Capacity of Grass Swale Design Western Swale Depth = Bottom Width = Top Width = Side Slope (H:V) = n= A= P= S- 0.40 ft 30.0 ft 33.2 ft 4 0.035 12.64 ftA2 33.30 ft 0.002 ft/ft 2 -year peak (entire site): i AR 2'3 1'2 Calculated C= Calculated V= Calculated Froude 4#_ 3.2 cfs 12.6 cfs 1.0 fps 0.29 Northern Swale Depth = Bottom Width = Top Width = Side Slope (H:V) = n= A= P S- 0.48 ft 6.0 ft 9.8 4 0.035 3.8016 ftA2 10.0 ft 0.002 ft/ft 2 -year peak (entire site): 1.49 AR - Calculated C= Calculated V= Calculated Froude 44_ 3.2 cfs 3.8 cfs 1.0 fps 0.28 Design F1w Maximum Maximum Maximum Fronde Number Veloci Flow Depth 2 -year event 0.5 1 ftis 1 ft Diversion Ditch Design (Typical) RESIDUAL IFOR LARGER FLOODS 12" ION. 2 YR WISE 5" MIN 4 -ft Wide (min) 1.5 -ft Tall (min) Low Estimated Capacity of Diversion Ditch Design (Typical) Depth of 1.oft* Bottom Width= 0.0 ft Side Slope (H:V)= 4 n= 0.035 A= 4.0 ftA2 P= 8.2 ft Minimum S= 0.004 ft/ft 1..49 AR213S"2 n Calculated Q= 6.6 cfs Calculated V= 1.7 fps Depth of 1.5ft* Bottom Width - Side Slope (H:V)= 0.0 ft 4 n= 0.035 A= 9.0 ft" 2 P= 12.4 ft Minimum S= 0.004 ft/ft 1.4' _,rig Calculated 0= 19.6 cfs Calculated V= 2.2 fps Depth of 2.oft* Bottom Width= 0.0 ft Side Slope (H:V)= 4 n= 0.035 A= 16.0 ft" 2 P= 16.5 ft Minimum 5= 0.004 ft/ft 1.49 , Calculated 0= 42.2 cfs Calculated V= 2.6 fps Preliminary Drainage and Erosion Control Report for the St. Vrain Laydown Yard Prepared for: Western Midstream 1099 18th Street Denver, Colorado 80202 Submitted to: Weld County Public Works Department 1111 H Street Greeley, Colorado 80631 February 2021 609 Consulting, LLC Engineering, Surveying, Consulting & Design Sheridan Office 1095 Saberton Avenue Sheridan, Wyoming 82801 Ph: (307) 674-0609 Fax: (307) 674-0182 Loveland Office 6706 North Franklin Avenue Loveland, Colorado 80538 Ph: (970) 776-4331 Fax: (970) 776-3301 Letter of Transmittal To: cc: Weld County Public Works Department 1111 H Street Greeley, Colorado 80631 Ms. Diana Aungst, Weld County Mr. Zackery Roberson, Weld County Ms. Aileen Yeung, Western Midstream Mr. Brian Venn, PE, 609 Consulting From: Mr. Tyler French, PE 609 Consulting 1095 Saberton Avenue Sheridan, Wyoming 82801 Date: February 4, 2021 Subject: St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report To Weld County Public Works Department: On behalf of Western Midstream, we are pleased to submit the Preliminary Drainage and Erosion Control Report for the St. Vrain Laydown Yard as part of an amendment to 1MUSR17-14-001. The purpose of this report is to discuss and summarize the stormwater drainage analysis and design performed for the proposed St. Vrain Laydown Yard. The proposed project will be located in the northwest quarter of Section 15, Township 3 North, Range 67 West in Weld County, Colorado. The drainage analysis and design were prepared using the Weld County Use by Special Review (USR) Procedural Guide, Weld County Engineering and Construction Guidelines, and Weld County Municipal Code as well as the Mile High Flood District (MHFD) Urban Storm Drainage Criteria Manuals. We believe the analysis and design satisfy all Weld County drainage requirements. We greatly appreciate your time and consideration in reviewing this submittal. We look forward to your review and comments. Please contact us with any questions you may have. Respectfully, TylerjFrench Registered Professional Engineer State of Colorado No. 51566 TABLE OF CONTENTS PAGE 1.0 PROJECT DESCRIPTION AND LOCATION 1 1.1 Project Description 1 1.2 Project Location 1 1.3 Drainage Summary 3 2.0 HYDROLOGIC ANALYSIS 3 2.1 Historic and Proposed Runoff 3 2.2 Stormwater Volume 5 3.0 HYDRAULIC ANALYSIS AND DRAINAGE DESIGN 5 3.1 Stormwater Storage 5 3.2 Storage Swales 6 3.3 Diversion Ditch 6 4.0 STORMWATER QUALITY CONTROL 6 5.0 SITE MAINTENANCE AND UPKEEP 7 6.0 CONCLUSION 7 7.0 REFERENCES 8 APPENDICES 9 St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page LIST OF FIGURES PAGE Figure 1. Project Location 2 LIST OF TABLES PAGE Table 1. Point Rainfall Data (NOAA Atlas 14 Point Precipitation Frequency Estimates) 4 Table 2. Area and Weighted Imperviousness 4 Table 3. Peak Flow Estimates 4 Table 4. Calculated Storm Runoff Volumes 5 APPENDICES Appendix A: Drainage and Erosion Control Plan Appendix B: Weld County Drainage Code Certificate of Compliance Appendix C: NRCS Web Soil Survey - Soils Report Appendix I): FEMA Flood Insurance Rate Map FIRMette Appendix E: NOAA Atlas 14 Point Precipitation Frequency Estimates Appendix F: UD-Rational Spreadsheet Calculations Appendix G: MHFD-Detention Spreadsheet Calculations Appendix H: Pipe Buoyancy Calculations Appendix I: Conveyance Calculations for Diversion Ditch Design St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page I II 1.0 PROJECT DESCRIPTION AND LOCATION Western Midstream is proposing the construction of the St. Frain Laydown Yard as part of an amendment to the existing Use by Special Review (tJSR), 1MUSR17-14-001. This USR contains the previously permitted and existing St. Vrain Compressor Station which is located in the northwest quarter of Section 15, Township 3 North, Range 67 West in Weld County, Colorado. Per the requirements outlined in the Weld County Use by Special Review (USR) Procedural Guide, Weld County Engineering and Construction Guidelines, Weld County Municipal Code, and through a direct request from Weld County, this report was prepared to discuss the analysis and design of stormwater drainage at the proposed project site. The Drainage and Erosion Control Plan, developed in conjunction with this report, can be found in Appendix A. The Weld County Drainage Code Certificate of Compliance can be found in Appendix B. 1,1 Project Description The proposed project consists of the construction and operation of the St. Vrain Laydown Yard. The laydown yard is nestled between several existing developed disturbances including the St. Frain Compressor Station to the east, Tomcat F14 Facility and Goose 3 9N-8 HZ well pad to the north, Maverick State 4C -16H Z well pad to the west, and Iceman State 32N-A16HZ well pad to the south. The laydown yard will have a total area of 12.68 acres within the fenced boundary. The southern portion of the fenced area will contain 7.67 acres of graded and graveled storage area and the northern portion of the fenced area will contain the main access road and entrance as well as two turn -around loops which will provide access to the undisturbed (native) portion of the storage yard. Stormwater storage swales, an outlet pipe, and an emergency spillway will be located outside the fenced area on the north and west sides of the laydown yard. Topsoil from stripping the graded portion of the laydown yard will be stored outside the fenced area on the south and west sides of the laydown yard. In addition to the laydown yard, an existing soil stockpile area located just south of the existing compressor station will be included in the USR amendment. The existing soil stockpile area is approximately 2.39 acres and is part of a larger area (6.67 acres) set aside for future soil stockpile storage. Operations and equipment at the existing compressor site have not changed since the last amendment; therefore, the proposed laydown yard and soil stockpile area will be treated separately. Grading and site layout for the St. Vrain Laydown Yard and soil stockpile area can be found in the Drainage and Erosion Control Plan found in Appendix A. 1,2 Project Location The St. Vrain Laydown Yard is located on property owned by Anadarko E&P Company LP (Parcel 120915200036). The project area is approximately 1.5 miles north of Highway 66 and 3.0 miles west of Highway 85. An existing road running south from County Road 34 will provide access to the laydown yard. The Town of Platteville, Colorado municipal boundary is located approximately 0.5 miles to the east of the proposed laydown yard. Because the proposed site is greater than a quarter of a mile from the nearest municipal boundary, the project is considered to be located in a non -urbanizing area. Figure 1 shows the location of the St. Vrain Laydown Yard. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 1 Anadarko E&P Company LP (Parcel 120915200036) South a Legend Proposed St. Vrain Laydown Yard Existing St. Vrain Compressor Station Soil Stockpile Area Existing Access Road Platteville Municipal Boundary Figure 1e Project Location Western Midstream LOVELAND OFFICE 6706 Nlortii Franklin Ave .i ue Loveland, Colorado 130538 Phone 970-776-4331 SHERIDAN OFFICE 09.9 lo' ve•lue Sher Wan, Wyoming 8?801 Phone 3V-674-0609 CONSULTING, LLC St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Soils data for the project area were taken from NRCS Soil Data Viewer. The project area is comprised of Nunn clay loam (0 to 1 percent slopes) with a Hydrologic Soil Group (HSG) classification of Group C soils. The soils report for the project area can be found in Appendix C. The St. Vrain Laydown Yard will be constructed on reclaimed agricultural land. According to the 2016 National Land Cover Database, the project area is classified as cultivated cropland. According to the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (Panel 08123C1885E, Effective Date: 1/20/2016), the St. Vrain Laydown Yard is in an area of minimal flood hazard (Zone X) and is therefore determined to be outside the 500 -year floodplain. The corresponding FIRMette displaying the flood zone classification at the project site can be found in Appendix D. 1.3 Drainage Summary The project area lies within the Outlet Saint Vrain Creek basin, Hydrologic Unit Code Level 12 (HUC 12): 101900050709. The HUC 12, approximately 20.5 square miles in area, consists predominately of agricultural land draining to St. Vrain Creek. There has not been a master drainage plan developed for this area. Historically, stormwater at the project site would drain from southeast to northwest until joining St. Vrain Creek. A network of roads and irrigation ditches has altered historic drainage conditions. Currently, stormwater generated at the proposed project site drains northwest along reclaimed agricultural fields, under County Road 34, and then into the St. Vrain Creek floodplain. 2.0 HYDROLOGIC ANALYSIS The following sections outline the methods used and corresponding results for the hydrologic analysis of the project site and drainage design including historic runoff, design flow, and stormwater volume. 21 Historic and Proposed Runoff Per Weld County Municipal Code requirements, runoff from the 1 -hour, 100 -year storm falling on the developed site should be detained and released at the historic runoff rate of the 1 -hour, 10 -year storm falling on the undeveloped site for non -urbanizing areas. Historic is defined as an undeveloped site with an imperviousness of 2.0 percent. The rational method was chosen to estimate peak flows for the project area. As discussed in the Mile High Flood District (MHFD) manual Urban Storm Drainage Criteria Manual Volume / (USDCM VI), it is acceptable to use the rational method for design storm analysis of catchments that are not complex and are 90 acres or less in size. The MHFD spreadsheet model Peak Runoff Prediction by the Rational Method Version 2.00 ((iD-Rational) was used to calculate peak flows using the rational method. One -hour point rainfall data were obtained from NOAA Atlas 14 Point Precipitation Frequency Estimates using coordinates for the project site. One -hour point rainfall data are summarized in Table 1 and a copy of the point precipitation frequency estimates obtained from NOAA can be found in Appendix E. Overland flow length,overland flow slope, channelized flow length, and channelized flow slope parameters were estimated using field survey, LiDAR data obtained from USGS's The National Map Download, imagery, and proposed grading design. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Pi-Thige 3 Per Weld County recommendation, 2007 MHFD C -Values were used to override the runoff coefficient, C. H SU was derived from an area -weighted average using NRCS S Soil Data Viewer. HSG and soils data for the project area can be found in Appendix C. USDCM VI was referenced for recommended conveyance factor (K]. Computed Time of Concentration (Tc) was used for areas with imperviousness of less than 20 percent. Calculations for area - weighted averages of percent imperviousness are found in Table 2. Peak flow estimates calculated using the rational method are summarized in Table 3. UD-Rational inputs and results can be found in Appendix F. Table 1. Point Rainfall Data (NOAA Atlas 14 Point Precipitation Frequency Estimates) Storm Event Frequency One -Hour Point Rainfall, in 2 -year 0.827 5 -year 1.10 10 -year 1.39 25 -year 1.85 50 -year 2.27 100 -year 2.74 500 -year 4.05 Table 2. Area and Weighted Imperviousness Basin Total Area, acre Open (2% Imperv), acre Gravel (40% Imperv, acre Weighted Imperviousness acre % Laydown Yard - Historic 16.11 16.11 0.00 0.32 2.0 Laydown Yard - Proposed 16.11 7.88 8.23 3.45 21.4 Soil Stockpile Area - Historic 6.67 6.67 0.00 0.13 2.0 Soil Stockpile Area - Proposed 6.67 6.67 0.00 0.13 2.0 Table 3. Peak Flow Estimates Basin Calculated Peak Flow, cfs 2 -year 5 -year 10 -year 25 -year 50 -year 100 -year Laydown Yard - Historic 0.7 2.5 5.1 9.9 14.4 19.7 Laydown Yard - Proposed 3.2 6.3 10.4 17.9 24.8 32.9 Soil Stockpile Area - Historic 0.4 1.3 2.7 5.3 7.6 10.4 Soil Stockpile Area - Proposed 0.4 1.3 2.7 5.3 7.7 10.5 Because the soil stockpile area has no change in imperviousness and negligible change in peak runoff (0.1 cfs during the 100 -year event), stormwater from this area will not be detained for release at lower rates. This area will, however, be part of Best Management Practice (BMPJ recommendations for sediment and erosion control. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 4 2.2 Stormwater Volume In accordance with Weld County Municipal Code requirements, stormwater from the 1 -hour, 100 -year storm falling on the laydown yard will be detained and released at reduced flow rates. The MHFD spreadsheet model Detention Basin Design Workbook Version 4.03 (MHFD-Detention) was used to calculate storm runoff volumes. One -hour point rainfall data for the project area (Table 1) were used within MHFD-Detention. Watershed parameters including area, length, and slope as well as imperviousness and soil type were calculated based on the site design and site characteristics. Table 4 shows storm runoff volumes calculated for the laydown yard. MHFD-Detention inputs and results can be found in Appendix G. Table 4. Calculated Storm Runoff Volumes Basin Storm Runoff Volume, acre -ft 2 -year 5 -year 10 -year 25 -year 50 -year 100 -year 500 -year Laydown Yard - Proposed 0.180 0.359 0.674 1.359 1.924 2.651 4.530 3.0 HYDRAULIC ANALYSIS AND DRAINAGE DESIGN Criteria presented in the MHFD Urban Storm Drainage Criteria Manuals outline the capacity, velocity, and slope requirements involved with drainage design and stormwater conveyance. The following sections describe the design recommendations for storage and conveyance of stormwater at the St. Vrain Laydown Yard. The recommended drainage design is shown in the Drainage and Erosion Control Plan which can be found in Appendix A. 3.1 Stormwater Storage Stormwater from the laydown yard, access road, and native storage area will be stored using a combination of storage swales and berms. The laydown yard will drain west into a diversion ditch which will direct stormwater north into the storage swales. The storage swales, located on the west and north sides of the native storage area, will store and direct stormwater to an outlet near the northwest corner of the storage yard. During the 5 -year event, stormwater will pond to a maximum depth of 0.76 feet and be fully contained within the storage swales. During events larger than the S -year, detained stormwater will begin to back up out of the swales onto the native storage area. During the 100 -year event, stormwater will pond to a maximum depth of 1.85 feet with a peak storage volume of 1.773 acre-feet. During the 500 -year event, stormwater will pond to a maximum depth of 2.14 feet with a peak storage volume of 2.868 acre-feet. The outlet for the storage berm consists of a 12 -inch diameter high -density polyethelene (HDPE) pipe. With an orifice invert at the bottom of the storage swale, a peak flow of 4.4 cfs will occur during the 100 -year event which is lower than the the allowable (10 -year historic peak) release rate of 5.1 cfs. It will take approximately 10 hours to drain 99 percent of the inflow volume during the 100 -year event. Buoyancy calculations were performed for the outlet pipe. Using a factor safety of 1.5, it was found that a minimum cover of 1.0 feet is needed to anchor the 12 -inch outlet pipe during fully saturated conditions. Buoyancy calculations can be found in Appendix H. Anti - seep collars should be used to prevent seepage through the berm and outlet slopes should be protected using geotextile fabric or riprap in order to prevent erosion along the embankment. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 5 The emergency spillway will be located on the west side of the laydown yard between the topsoil stockpile and the existing Maverick State 4C-16HZ well pad. The spillway will be built at grade (native ground) with a crest length of 20 feet, 4:1 side slopes, and a crest invert elevation at 4794.07 feet (1.9 feet above the outlet invert) allowing adequate storage for the 100 -year volume before stormwater reaches the spillway. Berms located on the north and west sides of the storage swales will be built to a minimum elevation of 4795.07 feet (2.9 feet above the outlet invert) in order to provide a freeboard of at least 1.0 feet above the spillway. The spillway was designed to convey the 100 -year peak flow at a depth of 0.50 feet. Stormwater storage and outlet sizing details for the storage swales, berms, and spillway can be found in Appendix A. Supporting calculations using MHFD-Detention can be found in Appendix G. 3.2 Storage Swales The storage area is comprised of two swales that converge to collect, store, and direct on -site stromwater to the outlet. The western swale has a bottom width of 30 feet with 4:1 side slopes and 0.2 percent slope. The northern swale has a bottom width of 6 feet with 4:1 side slopes and 0.2 percent slope. Combined, the storage swales can store approximately 0.182 acre -ft before spilling out into the native storage area. The swales will be permanently seeded to prevent erosion and sedimentation issues. 3.3 Diversion Ditch A diversion ditch will be used to collect and direct on -site stormwater to the storage swales and outlet. Manning's equation was used to calculate conveyance based on the diversion ditch design. The diversion ditch was found to convey 6.6 cfs at a depth of 1.0 feet, 19.6 cfs at a depth of 1.5 feet, and 42.2 cfs at a depth of 2.0 feet. The diversion ditch has more than adequate capacity to convey the 100 -year peak flow for the entire laydown yard (32.9 cfs) even though the ditch will only convey runoff from the southern portion of the laydown yard. Manning's calculations for ditch conveyance can be found in Appendix I. 4.0 STORMWATER QUALITY CONTROL In order to protect the project site, public road ROW and access, and future development plans while also meeting the requirements outlined in the Weld County Municipal Code, several stormwater quality control BMPs have been integrated into the site plans for the St. Vrain Laydown Yard. The following discussion outlines BMPs and procedures for stormwater quality control. As discussed in Section 3.1, the laydown yard will drain on -site stormwater to storage swales and an outlet. The swales and outlet have been properly sized to capture and control stormwater from the 100 -year event. Additionally, the topsoil stockpiles were positioned to direct off -site runoff away from the site which will prevent excess stormwater volumes from entering and overwhelming the storage swales and outlet. During construction, slope protection and compaction will be used along all cut/fill slopes and temporary disturbance areas. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 6 Permanent Seeding will be applied to all disturbed areas as well as final pad toes, swales, diversion ditches, and topsoil piles. Perennial vegetation increases soil infiltration rates and decreases sheet flow and movement of soil particles as compared to historic rates of the cultivated farmland and barren soil. This is due to increased surface cover, reduced soil compaction, and increased soil porosity. Seeding will be placed and crimped with straw for moisture retention which will aid in germination during the growing season. Outlet protection for the swale storage outlet pipe, including protection of the designated overflow spillway, will be installed as required. The Western Midstream access road and site monitoring program is used to ensure road and site conditions stay in compliance. Routine maintenance will ensure a safe and functioning project site. 5.0 SITE MAINTENANCE AND UPKEEP The Western Midstream site monitoring program ensures site conditions stay in compliance. Sedimentation, access road condition, vegetation health, and several other safety and maintenance items are routinely monitored and evaluated to ensure the site is in workable and drainable order. In addition to monitoring during regular operations, a formal monitoring plan has been developed for the project site. During the active construction period, the site will be inspected a minimum of every 14 calendar days as well as following any rain or snowmelt events that are able to cause surface erosion. After construction has finished, inspections will occur at a minimum of every 30 calendar days until the site is fully stabilized. Once the site is stabilized, inspections will occur annually. More frequent, informal inspections will continue to occur during routine operations and use of the site. Routine maintenance and required repairs of access roads, swales, ditches, berms, and the outlet will be handled by the operations team. Cleaning and removal of sediment and debris from the outlet, ditches, and swales as well as vegetation maintenance and specific manufacturer maintenance will also be handled by the operations team during regular operations and maintenance checks. 6.0 CONCLUSION The information and analysis presented in this report display the adequacy and effectiveness of the design and planning associated with the St. Vrain Laydown Yard Drainage and Erosion Control Plan. The design protects public health, safety, and general welfare and has no adverse impacts on public rights -of -way or off -site properties. Furthermore, the report demonstrates that the design adheres to Weld County Municipal Code as well as the Mile High Flood District (MHFD) Urban Storm Drainage Criteria Manuals. St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 1 7 7.0 REFE • ENCES Detention Basin Design Workbook Version 4.03 (MHFD-Detentionj. May 2020. Mile High Flood District. https:,//mhfd.org/resaurces/soft are National Flood Hazard Layer FIRMette. Federal Emergency Management Agency (FEMA). https : // msc.fema.gov/portal/ho nee National Land Cover Database 2016. Multi -Resolution Land Characteristics Consortium (MRLC). https://www.mr1c.govidata NOAA Atlas 14 Point Precipitation Frequency Estimates: CO. National Oceanic and Atmospheric Administration. https://hdsc.nws.noaa.gov/ hdsc/pfds/pfds map cont.htmlTkmrk=co Peak Runoff Prediction by the Rational Method Version 2.00 (DD -Rational). May 2017. Mile High Flood District ht •s://mhfd..org/resources/software The National Map Download Version 1.0. United States Geological Survey. https://apps.nationalmap.gov/download Urban Storm Drainage Criteria Manual: Volume 1 - Management, Hydrology, and Hydraulics. September 1969. Revised August 2018. Mile High Flood District. https://mhfd.org/resources/criteria-manual Urban Storm Drainage Criteria Manual: Volume 2 - Structures, Storage, and Recreation. September 1969. Revised September 2017. Mile High Flood District, https://nnhfd.org/resources/criteria-manual Urban Storm Drainage Criteria Manual: Volume 3 - Stormwater Quality. September 1992. Revised October 2019. Mile High Flood District. https://mhfd.org/resources/criteria-manual Web Soil Survey. Natural Resources Conservation Service. https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx Weld County Engineering and Construction Guidelines. April 2012. Revised July 2017. Weld County, Colorado. Weld County Municipal Code, Chapter 8, Article XI - Storm Drainage Criteria. July 2020.l Weld County, Colorado. Weld County Property Portal. Weld County, Colorado. https://www.co.weld.co.us/naps/propertyportal St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 1 APPENDICES St. Vrain Laydown Yard - Preliminary Drainage and Erosion Control Report Page 1 Ap endix A: Drainage and Erosion Contr 1 Plan K:\A.NALARKCk.2.020\202.1•_Gb_TOP_GUM_T3N_kb7'N SEC 15 -..DRAINAGE STUDY 5,DAG - DRAINAGE PLAM\ST Vk,AIN_,STORAGE_YARD_DP.dvg,2/4/X•11 11:38:31 AM, tf& 1 1 1 I 1 1 1 I I UNION PACIFIC RAILROAD COUNTY ROAD 19 PROPOSED ST. VRAIN LAYDOWN YARD COUNTY ROAD 19.5 4.1 ti. it TO3N S SURFACE OWNER: ANADARKO E&P COMPANY LP (PARCEL 120915200036) R67W COUNTY ROAD 34 X EXISTING ST. VRAIN _ COMPRESSOR STATION 15 SOIL STOCKPILE AREA LOCATION MAP 1" = 700' COUNTY ROAD 21 COUNTY ROAD 32.5 ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN LOCATED IN SECTION 15, T3 N, R67W, 6TH P.M. WELD COUNTY, COLORADO I 5 US 85 US 34 PROJECT SITE 1-76 WELD COUNTY VICINITY MAP PAGE INDEX 1 - COVER SHEET 2 - SITE OVERVIEW 3 - LAYDOWN YARD 4 - SOIL STOCKPILE 5 - STORAGE SWALE OUTLET 6 - SPILLWAY DETAILS 7 - OUTLET DETAILS S - BMP TYPICALS GENERAL NOTES: 1. 2. 3. THIS DRAINAGE AND EROSION CONTROL PLAN WAS PREPARED FOLLOWING WELD COUNTY MUNICIPAL CODE AND DESIGN GUIDANCE PROVIDED BY MILE HIGH FLOOD DISTRICT. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, PIPELINES, FLOWLI NES, AND SETBACK REQUIREMENTS. ORIGINAL DOCUMENT SIZE: 11"X 17" LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN COVER SHEET K:\A.NADARKCk.LU]d1'\202.1•_66_TOP_GUM_T3N_R67'N SEC 1S,DRATNAGE STUDYID'AC -DRAINAGE PLAM\ST bRATN_STORAGE_(ARD_DP.hg,2;4; AL'A1 11:43:14 AM, Why UNNAMED DITCH \ \ c �1 1 \ 5' CONTOURS LEGEND EXISTING CONTOUR EXISTING IRRIGATION DITCH PROPOSED FENCE PROPOSED ACCESS ROAD STORMWATER DRAINAGE UNION PACIFIC RAILROAD GENERAL NOTES: 1. 2. SURFACE OWNER: ANADARKO E&P COMPANY LP (PARCEL 120915200036) EXISTING ROAD PROPOSED ACCESS it% ROAD PROPOSED GRADED LAYDOWN YARD (7.67 ACRES) DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, I'I I'ELI NES, FLOWLI NES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVDHH (CEOID12B). EXISTING ST. VRAIN COMPRESSOR STATION LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776,4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 COUNTY ROAD 34 UNNAMED DITCH COUNTY ROAD 32.5 Western Midstream BEEMAN DITCH ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN SITE OVERVIEW K:\A.NADARKCk.2020'\202.1._56_TOP_GUM_T3N_R{s7'N SEC 15\DRATNAGE STUDYID'AC - DRAINAGE PL.N\ST bRATN_STORAGE_(ARD_DP.hg,2; 4; AL'21 11:44:51 APt tyL'r V CONTOURS LEGEND - EXISTING CONTOUR EXISTING ROAD M► STORM WATER DRAINAGE PROPOSED CONTOUR -X- PROPOSED ACCESS ROAD PROPOSED FENCE EXISTING WELL �+- 0.4% DITCH SLOPE DIVERSION DITCH PROPOSED DITCH CENTERLINE PROPOSED BERM PROPOSED CULVERT PROTECTION / RIPRAP 100 -YEAR STORM WATER STO RAGE FOOTPRINT PROPOSED PERMANENT SEEDING EMERGENCY SPILLWAY ----- ---------- GENERAL NOTES: MAVERICK STATE 4C-16HZ WELL PAD (RECLAIMED) BERM (TO MAINTAIN 1' OF FREEBOARD) 1. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, PII'ELINES, FLOWLI NES, AND SETBACK REQUIREMENTS. 2. ELEVATIONS ARE BASED ON NAVDBB (GEOID12B). 3. TOPSOIL STOCKPILE AND STORAGE SWALES WILL BE SEEDED AND VEGETATED. LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 STORAGE SWALE UNDISTURBED' /; (NATIVE) .f STORAGE AREA: x%/ii ..ly i ce UNDISTURBED (NATIVE) /; STORAGE AREA: Western Midstream 12" HDPE OUTLET PIPE STO RAGE SWALE TOMCAT F14 FACILITY ENTRANCE GATE PROPOSED ACCESS ROAD EXISTING ROAD ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN LAYDOWN YARD K:\A.NADARKCk2020\202.C•_66_TOP_GUM_T3N_R67'N SEC 1S,DRAINAGE STUDYID'AC - DRAINAGE PLAM\ST bRATN_STORAGE_(ARD_DP.dxg,2; 4; AL'A1 3:47:4A FM, ty r - - - - EXISTING CONTOUR EXISTING ROAD �M► STORMWATER DRAINAGE EXISTING FENCE DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, I'I !'ELI NES, FLOWLI NES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVDMI (CEOID12B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 K�\E NADARKiD\2026\2O20_66_TOP_GUN_T3N_R67W_SEC_t5 DRAINAGE STUDI',DWG - DRAINAGE PLANc$T_VRAIN_STORAGE_YARD_DP.dvq, 2/4/202i 1i:48 EDGE OF STORAGE SWALE ELEVATION 4793.05' I 7'\\r/N \� /�\/\ •\N"//, \/\\/\\�, * ,<,\\\ \ \t/N(/ /*\(\ 100 -YEAR STORAGE 5 -YEAR STORAGE �f. \\‘ 4 IL TOP OF BERM ELEVATION 4795.07' OUTLET PROFILE SCALE: NTS N a \\ \\\A.,/ //\/\\ \\<//\/\\///V ////\ j/\///\,// //x." STORAGE SWALE / OUTLET PIPE INVERT ELEVATION 4792.17' /\ . /\/\/\/\/ \/\/\\/\\\\ N\./'\\/.\-).>,\///� \ EXISTING ROAD 10,5' ////// //\///\(/ •‘\\\ *\/\\\\ \-///>//////<2", s\c/ \ //\ ,/`\\/\\/\\/\V \/\/\/\\//\\/\-/V\V\\\/\/\\/ /\ \\/\/ \\/\\/\`‘ \\" \/////e /.\\\,/,x /4,<\>>,\ \\\:\\>/\\ /\\„. 7,,,\/*\\\ \\/\\ *\./ *\\ \ \\ \///\////////\" < \\/"N \\//\\/'1‘,*.\‘K\A\-/ OUTLET ELEVATION 4791.92' \ N 30' BOLT -ON HDPE ANTI -SEEP COLLAR 45' / /\ 12" HOPE PIPE GENERAL NOTES: 1. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMEN TS, PI I'ELI NES, FLOWLI NES, AND SETBACK REQUIREMENTS. ELEVATIONS ARE BASED ON NAVD88 (CEOID12B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN STORAGE SWALE OUTLET RA E U �': KMG REV S K�\E NADARK41.2026\2O20_66_TOP_GUN_T3N_R67W_SEC_t5 DRAINAGE STUDI',DWG - DRAINAGE PLANc$T_VRAIN_STORAGE_YARD_DP.dvq, 2/4/202i 1i:5U: PROPOSED TOPSOIL STOCKPILE //,/ \ <e> 100-YEAR STORAGE ELEVATION 4794,02' 0.2% STORAGE SWALE SLOPE Ut 74n>,,/,,>-/Ivp\>,\>z- /\\,\\4,\I,,\ \/\\. \//\\ \\, \ -\ >XX / ` \ // ,\/ \/\/\/ ,/\/\/\/\/\/\/\/\/\/\/\/\/ ,/\, / \/\/\\/` /\/\\/\\/\/ ,/\/\/\/ ,,/ ,/\/\/\ \/\\/\/\\/\\/\\/\\/\\/\\/\\.\\/\\/\\/\\/\/\/\/\,\/\/\\/\/\\/\\/\\/\\/ti,,\/\\/\\/\\/\/ `�.,�\. 100 -YEAR PEAK FLOW SPILLWAY SECTION SCALE: NTS 28.00' SPILLWAY ELEVATION 4794.07' be 0t 0' ,/ MAVERICK STATE 4C-16HZ WELL PAD iELEVATION 4794.57' /\/\//'\/\/ \,/ \/\/\/\ 0.50' f� / \%` / \N \/ \/' \\•(/ \`//\/ \ �\ ` ,/ \� /\\ /4\ /;:i\> >\11/> //\\/\\/\/\\/\/\/1\/\/\/\/\//\"/\/\/\/\/\/\//\\/\\//\\//\�A/\/\/\\'/\\/\/�\/\/\/\/\� \/ti\/\\/\\/\\/\\/\\/\/\/\/\/\/\/`\f\/\/`./\/\/�,\/\/\\/\\/\/`\\/\/\\/ \\,\� \//\/`\I\\//` ,,///A`,r/j/.,1\/f\/\/\/\/\/\/\2�\/,\�/\r` \`\/`'\/,\\//\/ /\>>.// //A \��\� i//>% /\\//.\/<\-\\�\\ \\ \ ti , /\‘' \�\,.� \\`\ `\A \\\` \\ \\\A\ \\ <\\,/\\ -S SZ SPILLWAY ELEVATION 4794.07' // I- / /\\//N /N/A, f SPILI.WAY SPILLWAY PROFILE SCALE: NTS TOP OF BERM (TO MAINTAIN 1' OF FREEBOARD) EXISTING GRADE / / //\\/\`//\/\\f/\\`/\\,/\\/f\\\/ ,, '/\\/\\/\If f/\f/\\/\/'j\/`f\J//\°`\\ \ N \\\\\\\\\\\\ff\\'\\/`\/\/\/\\/\\/\\//ti\//\//\//\//`/\\\`; A*\>\.//'sx//., / A A fa *>(,/ \\/%K.W\C,\ 4\//, /1/, ///\ /\////N /\>S{ \\C <*\<\4/>\ /.\\\\ GENERAL NOTES: 1. DISCLAIMER: THIS PLAN REPRESENTS AN APPROXIMATE LOCATION OF DRAINAGE AND EROSION CONTROL FEATURES; EXACT LOCATION MAY VARY DEPENDING UPON EXISTING EASEMENTS, PIPELINES, FLOWLINES, AND SETBACK REQUIREMENTS. 2. ELEVATIONS ARE BASED ON NAB (GEOID12B). LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Sahcrton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 Western Midstream ST. VRAIN LAYDOWN YARD DRAINAGE AND EROSION CONTROL PLAN SPILLWAY DETAILS K�\E NADARK41.2026\2O20_66_TOP_GUN_T3N_R67W_SEC_t5 DRAINAGE STUDI',DWG - DRAINAGE PLANc$T_VRAIN_STORAGE_YARD_DP.dvq, 2/4/202i 1i:52: LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 307,674.0609 K�\E NADARKO1.2D2D\2020_66_TOP_GUN_T3N_R67W_SEC_t5 DRAINAGE STUDI',DWG - DRAINAGE PLANc$T_VRAIN_STORAGE_YARD_DP.dvq, 2/4/202i 1i:52:51 Culvert 1JfliA1 p. eleclas i (lavateuleamM Nola Make road earsiang. perperekulat to to dreinags to mu nmiz u pipe 1pnglh and at of 'Mailroom. NOT TO SCALE -:;- I W II . . .I164 ,,'. . . . .p r• ',. i, .' .,. . . . . •,. '.. . . ................I............ .•:,;.., x. •..• . • ,,... •. . .. . I - •`ra; : :,,,• ..... . tier • • SI oil. Or'filt...1 Exe reli u,.i i n 1 II, bleti0. 04.141,4 the singe. Osal IYDt errIr1 vele Owai, �umuu1 p'lrtre rACeitirsr Ara virtue Extend cu Ivan 1'6cyend fog of bp: NOT TO SCALE UNthr1 prafecaon es nitaded Soar ee 't. a-4cc bet eren weds Culver[ Ce3t7' FM slope — 'lace ou11t 4 INt %at neural g arld _ : ", la 44 r)r riFIMP OM*. RIO Se moo* Roadside dm& be 'Deena eeDal set leant' carond the flowers of one roadside ditch Wel prrriactiun es needed Culvert Culvert TYPE A 41 I r rta r 7 re a.ay a t in NOT TO SCALE Natural ground surtaca Roadbed Insiope 3-5% • r - Culvert — TYPE C Cvrnp acted Fill • ; 1 IN\ . ti, 1. 4. TYPE B Culwert Outlet protector' with rock rlprap Culvert Roadbed Inely 3-5% Roadbed Insteps 3-5% Compacted Fill Anchor tte slo3e :rein pipe to the till s'ope With slakes eaote anchor blocks. etc. 74 Compacted F]I Add riprao or other slope part ction Cutlet protection with rock riprap _ Outlet projection with cock riprap Jr 2V SLJBGRAE>IE 20' RUNNING SURFACE I 2.50% 2.30% 4.51 4" GRAVEL (MlN.) 1,3' DEEP DITCH (TIP.) Illthk 3. Diversion Ditch and Berm MD -1 Temporary Diversion Ditch and Berm 1.5-#t Tall (min) �4 it Wide (mini --- I FLOW NOTES: DIVERSION SWALE SHALL SLOPE BETWEEN 0.50% AND 8% TO A STABILIZED OUTLET SUCH AS A SEDIMENT TRAP. ALL BERMS MUST BE FULLY COMPACTED SO THAT THERE IS NO LOOSE SOIL Temporary and Permanent Seeding (T II PS) Table TS/PS-1, lk'Iinirntsto Drell Seeding Rates for Various Temporary An wool Grasses Species° ('Common name) Growth S n, Naiads of Pure Live Seed e (PLS)>rstrrfe Planting Depth (inches) 1. Oats C430i 35-50 1 -2 2, Spring when Cool 25 - 35 1 - 2 3, Spring barley Cool 25 - 35 1 - 2 • _. 4. Annual rycgrass Cool a 10 - 13 _.. 5. Millet Warm 3 - 15 °A - 3A 6. Sudangras5 Warm 5-10 11/4 ' "a 7., Sorghum Warm 5111 lei - ; R, Winter wheat Col 20-35 1 - 2 9. Wl{nylcr barley' Cool 20-35 I _ 2 10. Winter. rye Cool 20-35 1 - 2 l 1. Tritiolk Cool 25-40 1 - 2 a Successful seeding of annual usually produce enough dead wind and water erosion for is not disturbed or mowed-clo€er Hydraulic seeding may be substituted steeper than 3:1 or where access ceding is used, hydraulic munching opesatiern, when practical, to the much, ' irrigation. if consistently applied„ species during the summer I: Seeding rates should be doubled percent if done using a Brillion an monllis. grass -pt' additional prevent nt than limitations may if Drill resulting .residua g for should the extend seed or in adequate plain tc provide protection year. This assumes inches. chiRine only where exist. When hydraulic he applied ass a separate seeds from being encapsulated the use of cool Ls broadeasts or increased by hydraulic seeding. growth will from that the cover slopes are iii season by 50 ST. VRAIN LAYDOWN YARD fIRAINAGF ANl FRfSIfN C'fNTRIlI PI AN GENERAL NOTES: LOVELAND OFFICE 6706 North Franklin Avenue Loveland, Colorado 80538 Phone 970.776.4331 SHERIDAN OFFICE 1095 Saherton Avenue Sheridan, Wyoming 82801 Phone 3071574.0609 Western Midstream BM P TYPICALS ICALS A LEN ViR S ' 8 I 4 • !FA rozioni rte'' elk g Irttt� ear RA ED :': KMG I REV S Ap endix B: Weld County Drainage Code Certificate of Compliance Weld County Drainage Code Certificate of Compliance Weld County Case Number: Parcel Number: 120915200036 Legal Description, Section/Township/Range: NW4 S15/T3N/R67vv Date: I Tyler French , Consultant Engineer for Western Midstream (Applicant), understand and acknowledge that the app [cant is seeking land use approval of the case and parcel in the description above. I have designed or reviewed the design for the proposed land use set for in the application. I hereby certify, on behalf of the applicant, that the design will meet all applicable drainage requirements of the Weld County Code with the exception of the variance(s) describedexhibits. This certification is not a guarantee or warranty either expressed or implied. OC(N: .. (4/ /It • efies as` (..) /NC,/ Cias. itice4' O ' .£ t c + ' 1sCj Engineer's Stamp: Y Engineer of Record Signature 1. 2. 3. Describe List Describe Demonstrate that result the there of design the the the are project. hardship proposed that no criteria granting adverse oIONAL of Weld the County with from variance Variance Request (If Applicable) licable health, -of requested. the -way intent safety, and/or of the and offsite Weld general properties County welfare Code. as and a variance the engineering stormwater Code will is still being of adequately which rationale runoff requested. a to variance the which protect public supports is public being rights for of alternative the which impacts Public Works Director/Designee Review (If Applicable) Public Works Director/Designee Name Date of Signature Comments: Signature Approved ❑ Denied Department of Public Works I Development Review 1111 H Street, Greeley, CO 80631 I Ph: 970-304-6496 I www.weldgov.com/departments/public_works/development_review 08/02/2019 Appendix C: NRCS Web Soil Survey - Soils Report 40° 14'6"N 40° 13' 24" N 104° 53' 13"W 8 A Hydrologic Soil Group —Weld County, Colorado, Southern Part (St. Vrain Laydown Yard) 510000 510000 Map Scale: 1:6,190 if printed on A portrait (831 x 11") sheet. Meters 0 50 100 20D 300 510100 510100 510200 510200 Feet 0 300 600 1200 1800 Map p --lion : Web Mercator Corner coordinates: WGSS4 Edge tics: UTM Zone 13N WG584 510300 510300 510400 510400 510500 104° 52' 33" W 1040 52' 33" W 40° 14'6"N 40° 13' 24" N USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 1/21/2021 Page 1 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part (St. drain Laydown Yard) MAP LEGEND Area of Interest (AOI) O C Area of Interest (AOl) 1:24,000. D CID Soi is Soil Rating Polygons n A I A/D B B/0 C C{0 0 Not rated or not available Soil Rating Lines fora oirco A/D prasso prisisso B BID C ,�• C!D D • Not rated or not available Soil Rating Points 0 0 ■ ■ A AID B B/0 m 0 0 Not rated or not available Water Features Streams and Canals Transportation . Rails sarao Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography MAP IN FORMATION The soil surveys that comprise your AOI were mapped at Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Southern Part Survey Area Data: Version 19, Jun 5, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 19, 2018 —Aug 10, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources a Conservation Service Web Soil Survey National Cooperative Soil Survey 1/21/2021 Page 2 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part St. Vrain Laydown Yard Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Altman loam, percent slopes 0 to 1 B 33.6 22.0% 41 Nunn clay loam, percent slopes Oto 1 C 86.7 56.8% 46 Olney fine 0 to 1 sandy loam, percent slopes B 2.9 1.9% 69 Talent sand, percent slopes 0 to 3 A 29.3 19.2% Totals for Area of Interest 152.6 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID, BID, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas.Only the soils that in their natural condition are in group D are assigned to dual classes. USDA Natural Resources Web Soil Survey r Conservation Service National Cooperative Soil Survey 1/21/2021 Page 3 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part St. Vrairl Laydown Yard Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie -break Rule.- Higher USDA. Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 1/21/2021 Page 4 of 4 Appendix D: FEMA Flood Insurance Rate Map FIRMette National Flood Hazard Layer FIRMette FEMA Legend 104°53'15"W 40413'59"N 0 250 500 11000 1, 500 2,000 t6,00►0 104°52'38"W 40413'31"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) eA,tiA99 With BFE or Depth Zone AE, A{}, AR, yE, AR Regulatory Floodway OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Future Conditions 1% Annual Chance Flood Hazard Area with Reduced Flood Risk due to Levee. See Notes. zone X Area with Flood Risk due to Levee Zone D NO SCREEN Area of Minimal Flood Hazard zonex I I I I I I I 20.2 Effective LOMRs Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Base Flood Elevation Line (BFE) Limit of Study Jurisdiction Boundary Coastal Transect Baseline Profile Baseline Hydrographic Feature Digital Data Available No Digital Data Available Unmapped N The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FE MA. This map was exported on 12/4/2020 at 4:15 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. A pendx E: NOAH Atlas 14 Point Precipitation Frequency Estimates 1/12/2021 Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Platteville, Colorado, USA* Latitude: 40.229°, Longitude: -104.8823° Elevation: 4796.27 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF tabular PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) Duration ,JI 1 2 5 I 1 0 25 50 100 200 500 1000 5 -min 0.234 (0.183-0.301) 0.283 (0.221-0.365) 0.380 (0.295-0.491) 0.477 (0.368-0.61 ►) 0.633 (0.483-0.883) 0.772 (0.570-1.08) 0.927 (0.660-1.33) 1.10 (0.751-1.63)i 1 1.36 (0.889-2.06) 1.57 (0.992-2.38) . 10 -min 0.343 0.415 (0.323-0.534) 0.557 (0.433-4.719 f 0.698 (0.539-0.906 0.927 (0.708-1.29) 1.13 (0.835-1.59) 1.36 (0.967-1.95) 1.61 (1.10-2.38) 2.30 (1.45-3.49) 15 -min 0.418 (0.326-0.538) 0.506 (0.394-0.651) 0.679 (0.528-0.877) 0.852 (0.657-1.11) 1.13 (0.863-1.58j 1.66 I (1.18-2.38) 1.97 (1.34-2.91) 2.42 (1.59-3.68) 2.80 (1.77-4.26) 30 -rain 0.562 (0.439-0.723) 0.678 (0.528-0.873) 0.908 (0.705-1.17) 1.14 (0.878-1.48) 1.51 (1.15-2.11) 1.84 (1.36-2.59) 2.21 1 (1.58-3.19) 2.63 (1.80-3.89) 3.25 (2.13-4.93) 3.76 (2.38.5.72) 60 -ruin 0.692 (0.540-0.890) 0.827 (0.645-1.07) 1.10 (0.857-1.43) 1.39 (1.07-1.80) 1.85 (1.42-2.59) 2.27 (1.68-3.19) 2.74 (1.95-3.95) 3.27 (2.23-4.84) 4.05 (2.66-6.16) 4.71 (2.98-7.16) 2 -hr 0.822 (0.647-1.05) 0.977 (0.769-1.24) 1.30 (1.02-1.66) 1.63 (1.27-2.09) 2.19 (1.69-3.03) 2.69 (2.01-3.74) 3.26 (2.35-4.64) 3.90 (2.70-5.71) 4.86 (3.22-7.30) 5.66 (3.62-8.50) 3 -hr 0.897 (0.710-1.13) 1.06 (0.838-1.34) 1 1.40 (1.11-1.78) 1.76 (1.38-2.24) 2.36 (1.84-3.25) 2.90 (2.19-4.02) 3.52 (2.56.4.99) 4.23 (2.94-6.14) 5.27 (3.52-7.86) 6.15 (3.96-9.16) 6-hrI 1.06 (0.848-1.32) 1.247 (0.992-1.55) 2.01 (1.60-2.54) 2.67 ► (2.10-3.63) 3.27 (2.49-4.46) 4.71 (3.31-6.75) 5.85 (3.95-8.60) 6.81 (4.43-9.99) 1.26 (1.02-1.56) 1.50 (1.21-1.85) 2.37 _ (1.90-2.95) 3.07 (2.42-4.07) 3.67 (2.81-4.91) 4.35 (3.21-5.95) 5.10 (3.61-7.16) 6.1 (4.21-8.93) 7.10 (4.67-10.3) 24 -hr 1.51 (1.23-1.84) 1.79 (1.46-2.18) 2.30 (1.87-2.82) 2.78 (2.24-3.41) 3.51 (2.78-4.55) 4.13 (3.18-5.41) 4.81 (3.58-6.45) 5.55 (3.96-7.65) 6.61 (4.53-9.36) 7.47 (4.97-10.7) 2 -day 1.73 (1.43-2.09) 2.08 (172-2.51) 2.69 (2.21-3.25) 3.22 (2.63-3.91) 4.00 (3.18-5.08) 4.64 (3.60-5.96) 5.31 (3.98-6.99) 6.03 (4.33-8.15) 7.03 (4.86-9.77) 7.82 (5.26-11.0) 3 -day 1.89 (1.57-2.27) 2.25 (1.86-2.69) 2.86 (2.36-3.43) i 4.19 (3.35-5.27) 4.84 (3.77-6.16) 5.52 (4.16-7.20) 6.24 (4.51-8.37) 7.25 (5.05-9.99) 8.05 (5.45-11.2) 4 -day 2.02 (1.69-2.40) 2.38 (1.98-2.83) 2.99 (2.48-3.58) 3.54 (2.924.24) 4.33 I (3.48-5.42) I 4.99 i(3.91.6.31) 5.67 I (4.29-7.36) 6.40 (4.65-8.53) 7.42 (5.19-10.2) 8.23 (5.59-114) 1 117-day2.31 (1.94-2.72) 2.70 (2.27-3.19) 3.37 (2'.82-3.98) 3.95 (3.28-4.69) 4.77 l (3.86-5.88) 5.44 (4.29-6.79) 6.13 l (4.67-7.84) 6.85 (5.01-9.00) i 7.84 (5.52-10.6) 8.61 (5.91-11.8) ,14 -dad, 2.56 (2.16-2.99) 2.99 (2.52-3.50) 3.70 (3.11-4.35) 4.31 (3.60-5.08) w 5.16 (4.18-6.30) R 5.84 (4.62-7.22) t 6.53 (5.00-8.27) 7.24 (5.32-9.42) 8.21 (5.81-11.00 8.95 (6.18-12.2) 20 -day 3.27 (2.79-3.78) 4.58 (3.90-5.31) 5.26 (4.45-6.12) 6.19 (5.06-7.42) 6.91 (5.52-8.40) 7.62 (5.90-9.49) 8.35 (620-10.7) 1 9.31 (6.66-12.2') 10.0 7.00-13.4 30-day3.83 (3.29-4.39) 4.39 (3.77-5.05) 5.3'1 6.06 1 (5...16-7.00) 7.07 (5.81-8.39) 7.85 (6.31-9.45) 8.61 1 (6.70-10.6) 9.37 (7.00-11.9) i 10.4 (7.46-13.5) 11.1 (7.80-14.7) 45 -day 4.51 (3.90-5.13) 5.18 (4.47-5.90) 6.25 (5.38-7.14) i 7.11 (6.09-8.16) 8.27 (6.83-9.72) 9.14 (7.39-10.9) 9.98 (7.80-12.2) 10.8 (8.12-13.5) 11.9 (8.59-15.3) 12.6 (8.94-16.6) 5.05 (4.39-5.73) 5.83 (5.06-6.61) 7.07 (6.11-8.03)1; y 9.35 (7.75-10.9) 10.3 (8.37-12.2) 12.1 (9.15-15.1) 13 3 14.1 (9.99-18.3) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical https://hdscsnws.noaa.govlhdsclpfds/pfds_printpage.html?Iat=40.2290&Ian=-104.8823&data=depth&units=english&series=pds 1 k4 1/12/2021 Precipitation Frequency Data Server PDS-based depth -duration -frequency (DDF) curves Latitude: 40.2:290°, Longitude: -104.8823° cZ i 4J ra 0 a l C O 4J CL 16 14 12 10 8 6 16 14 .C E in C 5 10 25 50 100 200 NOAA Atlas 14, Volume 6, Version 2 C L. Duration csti A ni ' 6 H Average reLurrertce interval (years) i ra fa rti t 6 6 Ln 0- 61 f set ,c 500 1000 Created (GMT) : Tue Jan 12 15:58:25 2021 Back to Top Maps & aerials Small scale terrain varage recurrence interval years) 1 2 5' 10 25 50 100 200 5O0 1000 DJur"ationn. 5 -wan 10 -min 1 !--rein 3 -rain 6 0-rnon 2-mr 3 -hr 6-IIl r 12-h r 24 -hr -day. 3Aay 4 -day 7 -day 10 -day. 20 -day 30 -day 45 -day 60 -day, https://hdsc nws.noaa.govlhdsclpfds/pfds_printpage.html?lat=40.2290&Ian=-1 Q4.8823&data=depth&units=english&series=pds 2/4 1/12/2021 Precipitation Frequency Data Server unt.J Rd .. _ Platt f r 3km 2mi l (� Large scale terrain Large scale map it Ts'e •, 100km I gy�� y s C m •751 sr — Large scale aerial https://hdscsnws.nvaa.gov/hdsc/pfds/pfds_printpage.html?lat=4O.2290&Ian=-1 Q4.8823&data=depth&units=english&series=pds 3/4 1/12/2021 Precipitation Frequency Data Server Back to Top Fort Colt rnE= US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer https://hdsc.nws.noaa.gov/hdsclpfds/pfds_printpage.html?lat-4{x.2290&Ion=-104.8823&data-depth&units=english&series=pds 4/4 Appendix F: UD-Rational Spreadsheet Calculations Calculation of Peak Runoff using Rational Method Designer: Company: TPF 609 Consulting Date: 214/2021 Project Location: St. Wain Laydown Yard Version 2.00 released May 2017 Cells of this color are for required user -input Cells of this color are for optional override values Cells of this color are for calculated results based on over ti ` sia33 0.395(1.1 — Cs3� __ lit Lit 601C.,/ St 60Vt Computed tc = tr + tc Lit Regionaltc=(26-171)+ 60(141 + 9) titrinimain= 5 (urban) tminimun,= 10 (non -urban) Selected tc = max(tminimum , min(Computcd tc , Regional t,)) Select UDFCD location for NOAA Atlas 14 Rainfall Depths from the pulidown list OR enter your own depths obtained from the NOAA website (click this link) 1 -hour rainfall depth, P1 (in)= Rainfall intensity Equation Coefficients= 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 500-yr 0.827 I 1.10 1.39 1.85 I 227 2.74 a b C 28.50 I 10-00 0-7816 t(in/hr) = (b+tfc Q(c'f s) = CIA Subcatchment Name Area (ac) NRCS Hydrologic Soil Group Runoff Coefficient, C Overland (Initial) Flow Time Channelized (Travel) Flow Time Time of Concentration Rainfall Intensity, I (inthr) Peak Flow, 4 (cfs) Percent Imperviousness 2-yr 5-yr 10-yr 25-yr 59-yr 100-yr 500-yr Overland Flow Length L, (ft) U/S Elevation (ft) (Optional) DOS Elevation (ft) (Optional) Overland Flow Slope S; (ftlft) Overland Flow Time t; (min) Channelized Flow Length L. (ft) WS Elevation (ft) : r aal CIS Elevation (ft) lc r onal) Channelized Flow Shope S; (ftfft) NRCS Conveyance Factor K Channelized Flow Velocity V, (ft/sec) Channelized Flow Time t, (min) Computed tt[min) Regional I (min) Selected t (min) 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 500-yr 2-yr Syr 10-yr 25-yr 50-yr 100-yr 500-yr Laydown Yard Historic 16.11 C 2.0 0.01 0.05 0.15 0.33 0.40 0.49 0.59 500 0.002 72.01 3"C 0.003 10 0.55 9.43 81.44 35.82 35.82 1.17 1.55 1.96 2.61 3.20 3.86 0.2 1.3 4.6 13.9 20.8 30.6 0.06 0.16 0.26 0.38 0.45 0.51 64.55 73.98 73.98 0.72 0.96 1.22 1.62 1S9 2.40 0.7 2.5 5.1 9.9 14.4 19.7 0.15 0.21 0.29 0.44 D.50 0.57 0.66 47.37 66.75 38.52 38.52 1.11 1.48 1.87 2.49 3.06 3.69 2.7 5.0 8.7 17.6 24.6 34.0 0.18 0.27 0.35 0.45 0.50 0.55 44.38 63.76 3.2 6.3 10.4 17.9 24.8 32.9 0.01 0.05 0.15 0.33 0.40 0.49 0.59 Soil Stockpile Area - Historic 6.67 C 2.0 500 0.004 0 0.004 10 0.63 0.00 57.29 57.29 25.66 25.66 1.42 1.89 2.39 3.18 3.90 4.71 D.1 0.6 2.3 7.0 10.5 15.4 0.06 0.16 0.26 0.38 0.45 0.51 51.35 51.35 51.35 0.93 1.23 1.56 2.07 2.54 3.07 0.4 1.3 2.7 5.3 7.6 10.4 Soil Stockpile Area - Proposed 6.67 C 2.0 0.01 0.05 0.15 0.33 0.40 0.49 0.59 500 0.006 50.11 280 0 006 10 0.77 6-02 56.14 32-15 32.15 1.25 1.66 2.09 2.79 3.42 4.13 D.1 0.6 2.0 6.1 9.2 13.5 0.06 0.16 0.26 0.38 0.45 0.51 44.92 50 94 50.94 0.93 1.24 1.57 2.08 2.56 3.09 0.4 1.3 2.7 5.3 7.7 10.5 Appendix G: MHFD-Detention Spreadsheet Calculations DETENTION BASIN STAGE -STORAGE TABLE BUILDER MYFD-Detention, Version 4.03 (May 020) Project: St. grain Laydown Yard Basin II}: Laydown Yard - Proposed "'ONE 4 .ZONC2 IUF:YR 1 vouimi BaRi j WQCV - ,F f ION E At(D 2 r 01Slt4NCh1T Ca RC ES F'O3L I, fOMFw F ti Example Zone Configuration (Retention Pond) Watershed Information Flood Control Only Selected BMP Type = Watershed Area = Watershed Length = Watershed Length to Centroid = Watershed Sope = Watershed Imperviousness = Percentage Hydrologic Soil Group A = Percentage Hydrologic Soil Group B = Percentage Hydrologic Sal Groups C/D = Target WQCV Drain Time = Location for 1 -hr Rainfall Depths = User Input No BMP 16.11 930 500 0.002 21.40% 0.0% 0.0% 100.0°/0 40.0 acres ft ft ft/ft Flat Slope c 0.005 (tiff percent percent percent percent hours After providing required inputs above induding 1 -hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure. Water Quality Capture Volume (WQCV) = Excess Urban Runoff Volume (EURV) = 2-yr Runoff Volume (P1 = 0.83 in.) = 5-yr Runoff Volume (P1 = 1.1 in.) = 10-yr Runoff Volume (P1 = 1.39 in.) = 25-yr Runoff Volume (P1 = 1.85 in.) = 50-yr Runoff Volume (P1 = 2.27 in.) = 100-yr Runoff Volume (P1 = 2.74 in.) = 500-yr Runoff Volume (P1 = 4.05 in.) = Approximate 2-yr Detention Volume Approximate 5-yr Detention Volume Approximate 10-yr Detention Volume Approximate 25-yr Detention Volume Approximate 50-yr Detention Volume Approximate 100-yr Detention Volume Define Zones and Basin Geometry Zone 1 Volume (100 -year) Select Zone 2 Storage Volume (Optional) Select Zone 3 Storage Volume (Optional) Total Detention Basin Volume Initial Surcharge Volume (ISV) Initial Surcharge Depth (ISD) Total Available Detention Depth (Htotal) Depth of Trickle Channel (I-+rc) Sope of Trickle Ctannel (STc) Slopes of Main Basin Sides (Strain) Basin Length -to -Width Patio (R1,,,k,) Initial Surcharge Area (Ars;,) Surcharge Volume Length (L7s ) Surcharge Volume Wdth Depth of Basin Floor (HRooft) Length of Basin Floor (Lac, ) _ Width of Basin Floor (WRc,) Area of Basin Floor (Aaccn) = Volume of Basin Floor (VRcen) _ Depth of Main Basin (Hrt41N) _ Length of Main Basin (Lr.1 IN) _ Width of Main Basin (Wht=urr) _ Area of Main Basin (Artsura) _ Volume of Main Basin (Vr.1Arra) Calculated Total Basin Volume (Metal) _ 0.163 0.305 0.180 0.359 0.674 1.359 1.924 2.651 4.530 0.179 0.345 0.446 0.600 0.685 0.945 0.945 0.945 N/A N/A user user user user user user user user user user user user user user user user user user user acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet ft: R ft ft ft/ft H:V ft R ft ft ft ft ft ft ft ft ft ft` ft acre-feet Optional User Oerrides acre-feet acre-feet inches inches inches inches inches inches inches 0.827 1.10 1.39 1.85 2.27 2.74 4.05 Depth Increment = ft Stage - Storage Description Stage (ft) Optional Override Stage (It) Length (ft) 4lridth (ft) Area (ft `) Optional Override Area I ft `) Area (acre) Volume (ft) Volume (ac -It) Media Surface -- 0.00 -- -- -- 0 0.000 -- 0.05 -- -- -- 664 0.015 16 0.000 -- 0.10 -- -- -- 2,065 0.047 84 0.002 -- 0.15 -- -- -- 2,535 0.058 199 0.005 -- 0.20 -- -- -- 3,981 0.091 324 0.007 -- 0.25 -- -- -- 4,502 0.103 574 0.013 -- 0.30 -- -- -- 5,990 0.138 837 0.019 -- 0.35 -- -- -- 6,564 0.151 1,151 0.026 0.40 -- -- -- 8,094 0.186 1,517 0.035 -- 0.45 -- -- -- 8,715 0.200 1,851 0.042 -- 0.50 -- -- -- 10,291 0.236 2,412 0.055 0.55 -- -- -- 10,959 0.252 2,944 0.068 -- 0.60 -- -- -- 12,582 0.289 3,532 0.081 -- 0.65 -- -- -- 13,299 0.305 4,179 0.096 0.70 -- -- - 14,968 0.344 4,738 0.109 -- 0.75 -- -- -- 15,582 0.358 5,649 0.130 -- 0.80 -- -- -- 17,137 0.393 6,467 0.148 0.85 -- -- -- 17,782 0.408 7,340 0.169 -- 0.90 -- -- -- 19,724 0.453 8,278 0.190 -- 0.95 -- -- -- 20,989 0.482 9,087 0.209 1.00 -- -- -- 23,239 0.533 10,402 0.239 -- 1.05 -- -- -- 24,335 0.559 11,591 0.266 -- 1.10 -- -- -- 27,771 0.638 12,894 0.296 1.15 -- -- -- 32,921 0.756 14,411 0.331 -- 1.20 -- -- -- 37,135 0.852 15,795 0.363 -- 1.25 -- -- -- 43,131 0.990 18,169 0.417 1.30 -- -- -- 50,925 1.169 20,520 0.471 -- 1.35 -- -- -- 63,331 1.454 23,376 0.537 -- 1.40 -- -- -- 69,851 1.604 26,706 0.613 -- 1.45 -- - -- 80,341 1.844 30,460 0.699 -- 1.50 -- -- -- 85,992 1.974 34,619 0.795 -- 1.55 -- -- -- 98,938 2.271 39,242 0.901 1.60 -- -- -- 108,227 2A85 44,421 1.020 -- 1.65 -- -- -- 119,454 2.742 50,113 1.150 -- 1.70 -- -- -- 126,603 2.906 56,264 1.292 1.75 -- - - 135,920 3.120 62,827 1.442 -- 1.80 -- -- -- 142,532 3.272 69,788 1.602 -- 1.85 -- -- -- 154,379 3.544 77,211 1.773 1.90 -- -- - 157,520 3.616 85,009 1.952 -- 1.95 -- -- -- 167,681 3.849 93,138 2.138 -- 2.00 -- -- -- 170,249 3.908 101,587 2.332 2.05 -- -- -- 178,980 4.109 110,317 2.533 -- 2.10 -- -- -- 183,114 4.204 119,370 2.740 -- 2.15 -- -- -- 188,325 4.323 128,656 2.954 2.20 -- -- - 195,007 4.477 138,239 3.174 -- 2.25 -- -- -- 199,689 4.584 148,106 3.400 -- 2.30 -- -- -- 203,968 4.682 158,198 3.632 2.35 -- -- -- 209,569 4.811 168,536 3.869 -- 2.90 -- -- -- 299,456 6.875 308,518 7.083 MHFD-Deten ion_v4 03_ST VRAIN.xsrn, Bas n / 7:1 1_:03 P1/ DETENTION BASIN STAGE -STORAGE TABLE BUILDER MHFD-Detention, Version 413 (May 2020) 20 15 5 0 0.00 1.00 2.00 Stage (ft) — Length Ott) — Width {ft) Area (sq.ft.) 3.00 4.00 299600 224700 149800 - N 74900 0 6.880 5.160 In U a 3.440 sec L720 0-000 a /r ode X 0.00 1.00 2.00 Stage (ft.) Area (acres) — Volumeat- ft) 3.00 7.100 5.325 1375 0-000 4.00 MHFD-Deten"an_v4 03_ST VRAIN.xsm, Bas n 1/22/2021, 12:03 PM DETENTION BASIN OUTLET STRUCTURE DESIGN MHFD-Detention, Version 4,03 (May 2020) Project: St. Vrain Laydown Yard Basin ID: Laydown Yard - Proposed 1 AAY.VR VOLUME EURV WOcY T I PERMANENT— } POOL ZONE -ZONE 2 [L'JNL1 -- n - ZONE 1 AND 2'1 ORIFICES -1©0-YEAR ORIFICE Example Zone Configuration (Retention Pond) Zone 1 (100 -year) Zone 2 Zone 3 User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) ft (distance below the filtration media surface) inches Underdrain Orifice Invert Depth = Underdrain Orifice Diameter = N/A N/A Estimated Stage (ft) Estimated Volume (ac -ft) Outlet Type 1.57 0.945 Circular Orifice Total (all zones) 0.945 Underdrain Orifice Area = Underdrain Orifice Centroid = Calculated Parameters for Underdrain N/A N/A ft2 feet User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Invert of Lowest Orifice = Depth at top of Zone using Orifice Plate = Orifice Plate: Orifice Vertical Spacing = Orifice Plate: Orifice Area per Row = N/A N/A N/A N/A ft (relative to basin bottom at Stage = 0 ft) ft (relative to basin bottom at Stage = 0 ft) inches inches User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest' Stage of Orifice Centroid (ft) Orifice Area (sq. inches) Stage of Orifice Centroid (ft) Orifice Area (sq. inches) WQ Orifice Area per Row = Elliptical Half -Width = Elliptical Slot Centroid = Elliptical Slot Area = Calculated Parameters for Plate ft2 feet feet ft2 N/A N/A N/A N/A Row 1 (optional) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A Row 9 (optional, Row 10 (optional) Row 11 (optional, Row 12 (optional, Row 13 (optional) Row 14 (optional) Row 15 (optional; Row 16 (optional, N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A User Input: Vertical Orifice (Circular or Rectangular) Invert of Vertical Orifice = Depth at top of Zone using Vertical Orifice = Vertical Orifice Diameter = Zone 1 Circular Not Selected 0.00 4.00 12.00 ft (relative to basin bottom at Stage = 0 ft) ft (relative to basin bottom at Stage = 0 ft) inches Vertical Orifice Area = Vertical Orifice Centroid = Calculated Parameters for Vertical Orifice Zone 1 Circular Not Selected 0.79 0.50 ft2 feet User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir (and No Outlet Pipe) Overflow Weir Front Edge Height, Ho = Overflow Weir Front Edge Length Overflow Weir Grate Slope = Horiz. Length of Weir Sides = Overflow Grate Open Area % = Debris Clogging % = Not Selected Not Selected ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = feet Overflow Weir Slope Length = H:V Grate Open Area / 100-yr Orifice Area = feet Overflow Grate Open Area w/o Debris = %, grate open area/total area Overflow Grate Open Area w/ Debris = 0/ User Input: Outlet Pipe wif How Restriction Plate (Circular Orifice, Restrictor Plater or Rectangular Orifice) Depth to Invert of Outlet Pipe = Circular Orifice Diameter = Not Selected Not Selected User Input: Emergency Spillway (Rectangular or Trapezoidal) Spillway Invert Stage= Spillway Crest Length = Spillway End Slopes = Freeboard above Max Water Surface = 1.90 20.00 4.00 0.50 ft (distance below basin bottom at Stage = 0 ft) inches ft (relative to basin bottom at Stage = 0 ft) feet H:V feet Calculated Parameters for Overflow Weir Not Selected Not Selected feet feet ft2 ft2 Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate Outlet Orifice Area = Outlet Orifice Centroid = Half -Central Angle of Restrictor Plate on Pipe = Spillway Design Flow Depth= Stage at Top of Freeboard = Basin Area at Top of Freeboard = Basin Volume at Top of Freeboard = Not Selected Not Selected N/A N/A Calculated Parameters for Spillway 0.50 2.90 6.87 7.08 feet feet acres acre -ft ft2 feet radians Routed Hydrocraph Results Design Storm Return Period = One -Hour Rainfall Depth (in) = CUHP Runoff Volume (acre -ft) _ Inflow Hydrograph Volume (acre -ft) = CUHP Predevelopment Peak Q (cfs) = OPTIONAL Override Predevelopment Peak Q (cfs) _ Predevelopment Unit Peak Flow, q (cfs/acre) = Peak Inflow Q (cfs) = Peak Outflow Q (cfs) = Ratio Peak Outflow to Predevelopment Q = Structure Controlling Flow = Max Velocity through Grate 1 (fps) = Max Velocity through Grate 2 (fps) _ Tme to Drain 97% of Inflow Volume (hours) Tme to Drain 99% of Inflow Volume (hours) = Maximum Pending Depth (ft) = Area at Maximum Ponding Depth (acres) = Maximum Volume Stored (acre -ft) = The user can override the default CL/HP hvdrograohs and runoff volumes by entering new values in the Inflow Hvdrograohs table (Columns W through Al). WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year N/A N/A 0.83 1.10 1.39 1.85 2.27 2.74 4.05 0.163 0.305 0.180 0.359 0.674 1.359 1.924 2.651 4.530 N/A N/A 0.180 0.359 0.674 1.359 1.924 2.651 4.530 N/A N/A 0.1 1.1 3.6 9.8 14.3 20.0 34.2 N/A N/A 5.1 N/A N/A 0.01 0.07 0.23 0.61 0.89 0.32 2.13 N/A N/A 1.5 3.1 5.8 12.3 17.0 23.1 38.3 1.9 2.9 0.8 1.6 2.8 3.7 4.1 4.4 12.1 N/A N/A N/A 1.4 0.8 0.4 0.3 0.9 0.4 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Vertical Orifice 1 Spillway N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 3 3 5 5 5 6 7 9 11 4 4 5 5 6 7 8 10 12 0.84 1.12 0.53 0.76 1.05 1.47 1.66 1.85 2.14 0.41 0.68 0.24 0.36 0.56 1.87 2.74 3.54 4.28 0.164 0.309 0.060 0.133 0.266 0.718 1.150 1.773 2.868 MHFD-Detention v4 03 ST VRAIN.xlsm, Outlet Structure -1/2212021, 12:03 PM DETENTION BASIN OUTLET STRUCTURE DESIGN MH'FD-Detention, Version 4.00 (December 2019 FLOW [cis] cn tin tin on s - - ® SOOYRIN - - - 500YR OUT - 100YR IN - - 100YR OUT - SOYR N - - - SOYA OUT - 25YR IN - 25YR OUT - e 10YR IV - _ - - 10YR OUT - SYR IN - - - 5YR OUT - ! 2YR IN - - ® 2YR OUT EURV IN - - 4. ELM OUT - WOO/ IN — — WOCV OUT vo oft ` - a—~ . i. ti a - - . — — . — —. — „ f - .f — — .r ti,, I 3 ^ yy _ =-' 4-=:. - - - _ 0 r�l 0.1 1 110 TIME [hr] 2.5 500YR 100YR 50YR 2SYR 2 — 10YR SYR 2YR — EURV WQCV t' i c PONDING DEPTH If i 11;111 ll'hh‘ A rioldi r ti fI , IOppip„ ki 0.1 1 10 100 DRAIN TIM (1w] - 80 304,000 User Area Interpolated [ftA2] Area [ftA2] -0z� 250,000 Summary Area [ftA2] Volume [ft^3] —+1P- Summary Outflow Vol u.me [ft^3] - 60 200,000 [cfs] _,_,•-- _ Summary Outflow [cfs] 1 - 5b' cn 10,000ti 'r r.' � 7' U - 40 Di 3 Or'� 000 104,000 J --a u_ 30 0 u W d 1 : -1 1 - 20 50,000 -) - 10 r• .-, 0 i.1. _ 0 0.00 0,50 1.00 1.50 2.00 2.50 3400 3,50 4,00 PON DING DEPTH (t] S -A -V -D Chart Axis Override minimum bound maximum bound X-axis Left V -Axis Right V -Axis MHFD-Detention v4 03_ST VRAIN.xlsm, Outlet Structure 1/22/2021, 12:03 PM Appendix H: Pipe Buoyancy Calculations Buoyancy Calculations for Outlet Pipes 12" HDPE Pipe Ww — eir÷4)*(BcA2)*y 1.17 Bc = outside pipe diameter (feet) 62.42 y = unit weight of fresh water (pounds per cubic foot) 67.11 Ww = weight of displaced water (pounds per linear foot) Wt = -p 8.26 Wp = weight of pipe (pounds per linear foot) 58.85 Wt = resultant buoyant force of the submerged pipe (pounds per linear foot) Hi = (FS*Wt+Wi*Bc)_(O.1073*Bc) 68.0 Wi = average unit weight of inundated backfill (pounds per cubic foot) 1.5 FS = factor of safety 0.98 Hi = minimum depth of inundated backfill required above top of pipe (feet) INPUT CALCULATED * Assumes all backfill is inundated * Does not account for added weight from anti -seep collars Appendix I: Conveyance Calculations for Diversion Ditch Design Diversion Ditch Design (Typical) RESIDUAL IFOR LARGER FLOODS 12" ION. 2 YR WISE 5" MIN 4 -ft Wide (min) 1.5 -ft Tall (min) Low Estimated Capacity of Diversion Ditch Design (Typical) Depth of 1.oft* Bottom Width= 0.0 ft Side Slope (H:V)= 4 n= 0.035 A= 4.0 ftA2 P= 8.2 ft Minimum S= 0.004 ft/ft 1..49 AR213S"2 n Calculated Q= 6.6 cfs Calculated V= 1.7 fps Depth of 1.5ft* Bottom Width - Side Slope (H:V)= 0.0 ft 4 n= 0.035 A= 9.0 ft" 2 P= 12.4 ft Minimum S= 0.004 ft/ft 1.4' _,rig Calculated 0= 19.6 cfs Calculated V= 2.2 fps Depth of 2.oft* Bottom Width= 0.0 ft Side Slope (H:V)= 4 n= 0.035 A= 16.0 ft" 2 P= 16.5 ft Minimum 5= 0.004 ft/ft 1.49 , Calculated 0= 42.2 cfs Calculated V= 2.6 fps Cs 1' 4 -?X114 ENGINEERING Geotechnical Subsurface Exploration Program Anadarko St. Vrain Compressor Station Weld County Road 34 and Weld County Road 19 Weld County, Colorado Final Submittal Prepared For: Anadarko Petroleum Corporation 1099 18t" Street, Suite 2200 Denver, Colorado 80202 Attention: Mr. Cole Ones Job Number: 14-3559 May 21, 2014 41 Inverness Drive East I Englewood, CO 80112 I (303) 289-1989 I www.groundeng.com ENGLEWOOD I COMMERCE CITY I LOVELAND I GRANBY I GYPSUM I GRAND JUNCTION I GASPER TABLE OF CONTENTS Page Purpose and Scope of Study 1 Proposed Construction 1 Site Conditions Subsurface Exploration 4 Laboratory Testing 5 Subsurface Conditions 5 Engineering Seismicity Geotechnical Considerations for Design 7 Foundation/Floor System Overview 8 Foundation System Floor Systems 16 Mechanical Rooms/Mechanical Pads 19 Water Soluble Sulfates 19 Soil Corrosivity 20 Lateral Earth Pressures 23 Project Earthwork 24 Excavation Considerations 28 Utility Pipe Installation and Backfilling 29 Surface Drainage 32 Subsurface Drainage 34 Exterior Site Concrete 36 Gravel Road Section 38 Closure and Limitations 38 Locations of Test Holes Figure 1 Logs of Test Holes Figures 2-6 Legend and Notes Figure 7 Summary of Laboratory Test Results Table 1 Summary of Soil Corrosion Test Results Table 2 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal PURPOSE AND SCOPE OF STUDY This report presents the results of a subsurface exploration program performed by GROUND Engineering Consultants, Inc. (GROUND) for the proposed St. 'rain Compressor Station to be located near the intersection of County Road 34 and County Road 19 in Weld County, Colorado. Our study was conducted in general accordance with GROUND's Proposal No. 1403-0408, dated March 18, 2014. Field and office studies provided information obtained at the test hole locations regarding surface and subsurface conditions, including the existing site vicinity improvements. Material samples retrieved during the subsurface exploration were tested in our laboratory to assess the engineering characteristics of the site earth materials. Results of the field, office, and laboratory studies are presented below. This report has been prepared to summarize the data obtained and to present our conclusions and opinions based on the proposed construction and the subsurface conditions encountered. Design parameters and a discussion of engineering considerations related to construction of the proposed facility are included herein. The site plan and project configuration were altered following drilling operations for Test Holes 1 through 14 on March 27, 2014. Test Holes 15 through 22 were drilled following receipt of the new site plan. The design parameters presented herein are based on the test holes within the current project area (Test Holes 2, 3, and 15 through 22). PROPOSED CONSTRUCTION We understand that proposed construction is to include a compressor cooler, pipe racks and supports, air receiver, inlet slug catcher, generator building, skidded equipment, inlet separator, MCC building, and air compressor building. Additionally, gravel access roads are anticipated for the facility. Equipment/structure loads for most structures were provided in the Geotechnical Engineering Services document (provided by the Client) and ranged from approximately 2 to 600 kips. According to provided grading information, minimal material cuts and fills, up to approximately 2 feet, will be associated with the proposed project area. The perimeter of the project area will consist of an embankment that will initially slope away from the project area and result in material cuts Job No. 14-3559 Ground Engineering Consultants, Inc. Page 1 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal up to approximately 7 feet and material fills up to approximately 6 feet. The approximate proposed facility layout is shown in Figure 1. Development willlikely also include installation of shallow underground utilities to service the proposed facility. If proposed construction, including site grading or loading conditions, differ from those described above, or changes subsequently, GROUND should be notified to re-evaluate the information in this report. SITE CONDITIONS At the time of our exploration, the project site existed as vacant, agricultural land with remnant corn stubble and shod to tall grasses and weeds. An Anadarko production well/valves and an underground gas line exist within the project site. The general topography across the site was gently sloping to the northwest with slopes up to approximately 1 percent. The project site was bordered by County Road 19% to the east, county Road 34 to the north, county Road 19 to the west, and a lease road and agricultural field to the south. Although not obviously encountered in the test holes, man-made fill/tilled/disturbed soil likely exists within the upper 1 to 2 feet due to the past agricultural operations within the site. The exact extents, limits, and composition of any man-made fill were not determined as part of the scope of work addressed by this study, and should be expected to exist at varying depths and locations across the site. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 2 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Regional Geology Published maps (e.g., Colton, 19781) depict the site as underlain by the Quaternary Broadway Alluvium and Eolium Materials. These materials consisted of deposits of windblown sand and gravel deposited by the South Platte River and its tributaries. The Broadway Alluvium is mapped as underlain by the Upper Cretaceous Laramie Formation consisting of gray claystones, shales, and scattered beds of sandstone and lignite. Approximate Project Site Based on the published information reviewed for the site and the findings of this exploration program, the site appears to be feasible with respect to potential geologic hazards and general geotechnical design concerns. 1 Colton, Roger, B., 1978, Geologic map of the Boulder, Fort Collins, Greeley Area, Colorado: U.S. Geological Survey, Geologic Quadrangle Map l -655G, scale 1:24,000 Job No. 14-3559 Ground Engineering Consultants, Inc. Page 3 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal SUBSURFACE EXPLORATION The subsurface exploration for the project was conducted on March 27 and April 25, 2014. A total of twenty - 7 two (22) test holes were drilled with a truck -mounted, continuous flight power auger rig to evaluate the subsurface conditions as well as to retrieve soil samples for laboratory testing and analysis. As stated, Test Hole 1 through 14 were drilled within the original project area and Test Holes 15 through 22 were drilled within the revised project area. The test holes were advanced to depths ranging from approximately 35 to 50 feet below existing grade within/near the general proposed structure/equipment footprint limits and throughout the proposed facility. A representative of GROUND directed the subsurface exploration, logged the test holes in the field, and prepared the soil samples for transport to our laboratory. Samples of the subsurface materials were retrieved with a 2 -inch I.D. California liner sampler. The sampler was driven into the substrata with blows from a 140 -pound hammer falling 30 inches. This procedure is similar to the Standard Penetration Test described by ASTM Method D1586. Penetration resistance values, when properly evaluated, indicate the relative density or consistency of soils. Depths at which the samples were obtained and associated penetration resistance values are shown on the test hole logs. The approximate locations of the test holes are shown in Figure 1. Logs of the exploratory test holes are presented in Figures 2 through 6, Explanatory notes and a legend are provided in Figure 7. A representative of the Client surveyed the test holes for approximate location and elevation prior to drilling. Test Holes 2, 3, and 15 through 22 are located within the current project area. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 4 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal LABORATORY TESTING Samples retrieved from our test holes were examined and visually classified in the laboratory by the project engineer. Laboratory testing of soil samples obtained from the subject site included standard property tests, such as natural moisture contents, dry unit weights, grain size analyses, swell -consolidation potential, cdirect shear testing, and liquid and plastic limits. Water-soluble sulfate and corrosivity tests were completed on selected samples of the soils as well. Proctor tests were also completed on the composite bulk samples. Laboratory tests were performed in general accordance with applicable ASTM and AASHTO protocols. Results of the laboratory testing program are summarized on Tables 1 and 2. SUBSURFACE CONDITIONS The subsurface conditions encountered in the test holes consisted of a thin veneer of topsoil (approximately 2 inches thick, potentially greater) underlain by sand and/or clay. The test holes were extended to depths of approximately 35 to 50 feet below the existing grades. Bedrock was not encountered in the test holes to depths up to approximately 50 feet below existing grades. Sand was silty to clayey with gravel lenses, fine to gravel grained, non -plastic to medium plastic, loose to dense, moist, tan to brown in color, and occasionally calcareous. Sand and Clay were interbedded, fine to medium grained, low to highly plastic, loose to dense/medium to very stiff, moist, brown in color, and occasionally calcareous. Swell -consolidation testing of samples of the tested on -site materials encountered in the project test holes indicated a potential for heave/consolidation. A swell of approximately 0.1 percent and consolidations of approximately 0.5 to 2.3 percent were measured upon wetting under various surcharge pressures (Table 1). Groundwater was encountered in some of the test holes at depth ranging from approximately 18 to 27 feet (elevations of approximately 4,769 to 4,778 feet) below existing grades at the time of drilling and at a depth of approximately 20 feet (elevation of approximately 4,777 feet) below existing grade when measured 7 days later. Groundwater levels can be expected to fluctuate, however, in response to annual and Job No. 14-3559 Ground Engineering Consultants, Inc. Page 5 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal longer -term cycles of precipitation, irrigation, surface drainage, nearby rivers and creeks, land use, and the development of transient, perched water conditions. ENGINEERING SEISMICITY According to the 2012 International Building Code® (Section 1613 Earthquake Loads), "Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and theirsupports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with ASCE 7, excluding Chapter 14 and Appendix 11A. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 (2012 IBC) or ASCE 7." Exceptions to this are further noted in Section 1613. Utilizing the U's Seismic Design Maps Tool (http:llqeohazards.usqs.qovfdesiq nmaps/us/application .php) and site latitude/longitude coordinates of 40.229321 and —104.879495 (obtained from Google Earth), respectively, the project area is indicated to possess an Sips value of 0.181 and an SDI value of 0.089. Per 2012 IBC, Section 1613.5.2 Site class definitions, "Based on the site soil properties, the site shall be classified as Site Class Al E, C, D, E or F in accordance with Table 1613.5.2. When the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the building official or geotechnical data determines that Site Class E or F soil is likely to be present at the site". Based on the soil conditions encountered in the test hole drilled on the site, our review of applicable geologic maps, as well as our experience within the Project site vicinity, GROUND estimates that a Site Class a according to the 2012 IBC classification (Table 1613.5.2) could be anticipated for seismic foundation design. This parameter was estimated utilizing the above -referenced table as well as extrapolation of data beyond the deepest depth explored. Actual shear wave velocity testing/analysis and/or exploration to 100 feet was not performed. In the event the Client desires to potentially utilize Site Class C for design, according to the 2012 IBC, actual downhole seismic shear wave velocity testing and/or exploration to subsurface depths of at least 100 feet, should be performed. In the absence of additional subsurface exploration/analysis, a Site Class ID should be utilized for design. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 6 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal The largest recorded earthquake (estimated magnitude 6.2 to 6.6) in Colorado occurred in November 1882. While the specific location of this earthquake is very uncertain, it is postulated to have occurred in the Front Range near Rocky Mountain National Park. The most recent significant seismic movements associated with the Rock Mountain Arsenal Fault (commerce City, Colorado) occurred in the -1960s, generating earthquakes up to magnitude 5.5. Since the early 1960s, numerous earthquakes with magnitudes up to approximately 5, with the majority possessing magnitudes of 2 to 4, have been experienced within the State. Recently, earthquakes ranging in magnitude from 3.7 (Craig, Colorado) to 3.9 (Ends, Colorado and Trinidad, Colorado) occurred during the time period of July, 2009 through August, 2009. On August 23, 2011, a 5.3 magnitude earthquake occurred 9 miles west-southwest of Trinidad, Colorado. Earthquakes with similar magnitudes, and potentially greater, are anticipated to continue by the USGS, throughout the State. Furthermore, based on the subsurface conditions at the site and the risks associated with this nearest fault, the risk of liquefaction of the site soils is considered low. GEOTECHNICAL CONSIDERATIONS FOR DESIGN As stated, minimal cuts and fills are planned within the proposed project area. Additionally, an embankment will be constructed around the perimeter of the proposed project area that will necessitate material cuts up to approximately 7 feet and fills up to approximately 6 feet. The materials within the upper 6 feet of the existing grades within Test Holes 2, 3, and 15 through 22 (test holes located within the project area) consist of silty to clayey sands and sandy clay. Variable penetration resistance values and dry densities were observed in our field and laboratory testing programs. GROUND performed a settlement analysis for select structures. This analysis indicated that shallow foundations/floor systems placed directly on the site materials may result in the potential for settlement on the order of 1 to 1.5 inches, depending on the foundation size and approximate loading. Typically, deep foundation systems such as drilled piers are utilized to reduce the potential for post construction movement. However, given that bedrock was not encountered during our exploration program, a deep foundation option does not appear to be practical/cost-effective for this project. Anticipated foundation type for the structures is provided in the Foundation/Floor System Overview section. Caution should Job No. 14-3559 Ground Engineering Consultants, Inc. Page 7 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal be taken at this site regarding shallow foundations (footings and monolithic slabs/mats), since the allowable bearing pressure represents approximately `1 to 1.5 inches of settlement in response to structural loading. If the subsoils are exposed to changes in moisture content following the completion of construction, additional settlements are likely to occur. In an industrial selling, such as the proposed compressor station, post - construction moisture increases are generally lesser compared to residential or even commercial developments where landscaping is performed, large areas are covered by pavement/hardscaping, and vegetation is irrigated. FOUNDATION/FLOOR SYSTEM OVERVIEW Based on provided information, the following presents the anticipated foundation systems for the proposed structures/equipment and approximate loads. Equipment Approximate Loads Anticipated System Foundation/Floor Compressor Skid 120 kips Prepared Gravel Surface Compressor Cooler 65 kips Spread Footings/Helical Piles Pi p e F�acks�Pi p e Su pp orts 1-14 ki p s Spread Footings/Helical Footings/Drilled Piles Air Receiver 30 kips Concrete Mat InletSlug Catcher 600 kips Spread Footings Generator Building 75 kips Spread Footings/Helical Piles Skidded Equipment 2-14 kips Spread Footings/Helical Piles Inlet Separator 80 kips Concrete Mat MCC Building 250 kips Spread Footings/Helical Piles Air Compressor Building 30 kips Spread Footings/Helical Piles For structures such as the compressor cooler, inlet slug catcher, air receiver, generator building, inlet separator, and MCC building, shallow foundations consisting of spread footings or a concrete mat foundation are being considered. In order to reduce the risk of settlement and provide a uniform layer beneath footings and mat foundations, Job No. 14-3559 Ground Engineering Consultants, Inc. Page 8 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal overexcavation and replacement of the existing on -site soils to a depth of at least 3 feet should be performed. The soils should be properly prepared on -site generated soils should be placed prior in accordance with the Project Earthwork section of our report. Utilizing this option, we anticipate movement potentials on the order of 1 inch (based on the movement potential of the underlying subgrade material). A prepared gravel surface is anticipated for the compressor skid. A minimum of 3 feet of naturally occurring CDOT Class 6 aggregate base course should be utilized. Ideally, a layer of geotextile material (Mirafi HP 370 or equivalent) should be placed at the interface of the site soils and imported base course. For structures such as the pipe racks/pipe supports, skidded equipment and the air compressor building, lighter loads are anticipated. For these lightly loaded structures, the use of shallow foundations such as spread footings or drilled footings could be performed. Based on the results of our field and laboratory testing, moisture -density treatment of the existing soils to a depth of at least 12 inches should be performed beneath footings prior to the placement of any new fill materials (if applicable). For lightly loaded slabs, similar depths of moisture -density treatment should be performed. The materials should be placed in accordance with the Project Earthwork section of our report. To use these parameters, the Owner must accept the risk of post -construction foundation movement associated with shallow foundation systems placed on th.e on -site soils. Utilizing the above option as well as other applicable information in this report for the equipment stated above, GROUND estimates potential movements may be on the order of 1 inch (based on the movement potential of the underlying subgrade material). FOUNDATION SYSTEMS Deep/Intermediate Foundation Systems Screw pile/helical piers can be considered as an alternate foundation option and appear to be feasible for this site. Screw piles and helical piers differ primarily in the amount of capacity they can provide, with screw piles typically capable of higher capacities than helical piers. Screw piles can typically achieve capacities of up to 300,000 lbs, while helical piers are generally limited to around 100,000 lbs. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 9 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Helical piers sometime need to be pre -drilled to achieve minimum penetration depths, however we do not anticipate pre -drilling would be necessary for this site. We also do not anticipate that a very strong/resistant layer will be encountered upon which screw piles or helical piers would bear or be socketed into. Therefore, torque necessary to establish required capacities will most likely have to be developed by the number of helices on the piles/piers. Both screw piles and helical piers typically utilize hydraulic pressure converted to toque to determine when capacities have been achieved. The conversion from drive head pressure to torque is often based on a drive head calibration. Contractor submittals should include a current drive head pressure torque calibration performed within the last six months. Torque is also sometimes verified through the use of shear pins, or periodically verified on a few piles/piers during installation. The drive head calibration submittal requirement may be waived if shear pin torque verification is used on at least 50% of the piles/piers. To determine capacity, design/builders use an empirical torque coefficient (ETC) which is largely based on the available geotechnical data and experience. Therefore, true capacity is unknown unless a load test is performed to verify the ETC used in the design. We highly suggest a load test be performed if screw piles/helical piers are used on the project. In the absence of a load test, a highest ETC of 7 can be accepted from a design/builder and preferably not more than 5 ft -1. Full time observation of installation by a quality control representative should be performed. We are available to review screw pile/helical pier designs, and perform load test and installation observations upon request. A minimum depth of installation of 20 feet for screw piles/helical piers should be performed. Based on the available geotechnical data, the soils appear to generally gain in stiffness and strength at approximately 20 feet below existing grades. Screw piles/helical piers are typically handled by specialty design/build contractors, who should be provided with a copy of the available geotechnical data as well as the foundation plan, structural loads, and movement tolerances. Lateral loads are often handled by the installation of battered piles/piers, or alternatively the L -Pile design parameters presented below may be used. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 10 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Estimated Geotechnical Parameters for Lateral Load Analysis Sands and Clays Sand Soil Type Density (pcf) 120 111 Cohesion, C (psi) 10 - Friction Angle - 30 E50 (inn) 0.010 0.010 Kh (pci) 500 100 Shallow Foundation Systems The geotechnical parameters indicated below may be used for design of shallow foundations for the proposed structures. Geotechnical Parameters for Shallow Foundation Design Compressor Cooler, Inlet Slug Catcher, Air Receiver, Generator Building, Inlet Separator, and MCC Building Mat Foundations 1) Mat foundations should bear on 3 or more feet of properly prepared on -site generated fill soil. The fill section should extend should extend at full thickness across the structure/slab footprint and at least 3 feet laterally beyond the perimeter(s). Considerations for fill placement and compaction are provided in the Project Earthwork section of this report. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 11 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal The fill section should be laterally consistent and of uniform depth to reduce differential, post -construction foundation movements. A differential fill section will tend to increase differential movements. The contractor should provide survey data of the excavation beneath each structure indicating the depth and lateral extents of the remedial excavation. 2) Mat foundations bearing on properly prepared materials may be designed for an allowable soil bearing pressure of 2,500 psf. These values may be increased by' for transient loads such as wind or seismic loading. Compression of the bearing soils for the provided allowable bearing pressure is estimated to be 1 inch, based on an assumption of drained foundation conditions. If foundation soils are subjected to an increase/fluctuation in moisture content, the effective bearing capacity will be reduced and greater post -construction movements than those estimated above may result. This estimate of foundation movement from direct compression of the foundation soils is in addition to movements from collapse of hydro -compressive soils. To reduce differential settlements between footings or along continuous footings, footing loads should be as uniform as possible. Differentially loaded footings will settle differentially. A shear modulus value (G) of 100 ksf and Poisson's ratio of 0.3 can be utilized in the foundation design for the on -site soils. Structures (slabs) should bear at an elevation 3 or more feet below the lowest adjacent exterior finish grades to have adequate soil cover for frost protection Continuous foundation walls should be reinforced as designed by a structural engineer to span an unsupported length of at least 10 feet. Geotechnical parameters for lateral resistance to foundation loads are provided in the Lateral Earth Pressure section of this report. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 12 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal 7) Connections of all types must be flexible and/or adjustable to accommodate the anticipated, post -construction movements of the structure. Spread Footings Footingsshould bear on 3 or more feet of properly prepared on -site generated fill soil. The fill section should extend should extend at full thickness across the structure footprint and at least 3 feet laterally beyond the perimeter(s). Considerations for fill placement and compaction are provided in the Project Earthwork section of this report. The fill section should be laterally consistent and of uniform] depth to reduce differential, post -construction foundation movements. A differential fill section will tend to increase differential movements. The contractor should provide survey data of the excavation beneath each structure indicating the depth and lateral extents of the remedial excavation. 2 Footings bearing on properly compacted materials may be designed for an allowable soil bearing pressure of 2,500 psf for footings up to 11 feet in width (minimum lateral dimension). These values may be increased by Y3 for transient loads such as wind or seismic loading. For larger footings, a lower allowable bearing pressure may be appropriate. Compression of the bearing soils for the provided allowable bearing pressure is estimated to be 1 inch, based on an assumption of drained foundation conditions. If foundation soils are subjected to an increase/fluctuation in moisture content, the effective bearing capacity will be reduced and greater post -construction movements than those estimated above may result. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 13 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal This estimate of foundation movement from direct compression of the foundation soils is in addition to movements from expansive soils heave and/or collapse of hydro -compressive soils. To reduce differential settlements between footings or along continuous footings, footing loads should be as uniform as possible. Differentially loaded footings will settle differentially. 3 Spread footings should have a minimum lateral dimension of 16 or more inches for linear strip footings and 24 inches for isolated pad footings. Actual footing dimensions should be determined by the structural engineer. Footings/structures (slabs) should bear at an elevation 3 or more feet below the lowest adjacent exterior finish grades to have adequate soil cover for frost protection 5) Continuous foundation walls should be reinforced as designed by a structural engineer to span an unsupported length of at least 10 feet. Geotechnical parameters for lateral resistance to foundation loads are provided in the Lateral Earth Pressure section of this report. 7) Connections of all types must be flexible and/or adjustable to accommodate the anticipated, post -construction movements of the structure. Pipe Racks/Pipe Supports, Skidded Equipment and the Air Compressor Building Spread Footings 1) Footings should bear should bear on approximately 12 inches of properly compacted on -site generated material, Considerations for fill placement and compaction are provided in the Project Earthwork section of this report. Footings bearing on properly prepared site materials may be designed for an allowable soil bearing pressure of 1,.500 psf for footings up to 5 feet in width (minimum lateral dimension). Shallow foundations (drilled footings) bearing at Job No. 14-3559 Ground Engineering Consultants, Inc. Page 14 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal least 8 feet below adjacent final grades may be designed for an allowable soil bearing pressure of 2,500 psf. These values may be increased by V for transient loads such as wind or seismic loading. For larger footings, a lower allowable bearing pressure may be appropriate. Compression of the bearing soils for the provided allowable bearing pressure is estimated to be 1 inch, based on an assumption of drained foundation conditions. If foundation soils are subjected to an increase/fluctuation in moisture content, the effective bearing capacity will be reduced and greater post -construction movements than those estimated above may result. This estimate of foundation movement from direct compression of the foundation soils is in addition to movements from expansive soils heave and/or collapse of hydro -compressive soils. To reduce differential settlements between footings or along continuous footings, footing loads should be as uniform as possible. Differentially loaded footings will settle differentially. 3 4 Spread footings should have a minimum lateral dimension of 16 or more inches for linear strip footings and 24 inches for isolated pad footings. Actual footing dimensions should be determined by the structural engineer. Drilled footings should have a minimum diameter of 12 inches. Actual footing dimensions/sizes should be determined by the structural engineer. Footings bear at should an elevation 3 or more feet below the lowest adjacent exterior finish grades to have adequate soil cover for frost protection continuous foundation walls should be reinforced as designed by a structural engineer to span an unsupported length of at least 10 feet. 7) Geotechnical parameters for lateral resistance to foundation loads are provided in the Lateral Earth Pressure section of this report. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 15 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal 3 Connections of all types must be flexible and/or adjustable to accommodate the anticipated, post -construction movements of the structure. Shallow Foundation Construction 9) The contractor should take adequate care when making excavations not to compromise the bearing or lateral support for nearby improvements. 10) Care should be taken when excavating the foundations to avoid disturbing the supporting materials particularly in excavating the last few inches. 11) Footing excavation bottoms may expose loose, organic or otherwise deleterious materials, including debris. Firm materials may become disturbed by the excavation process. All such unsuitable materials should be excavated and replaced with properly compacted fill or the foundations deepened. 12) Foundation -supporting soils may be disturbed or deform excessively under the wheel loads of heavy construction vehicles as the excavations approach footing bearing levels. Construction equipment should be as light as possible to limit development of this condition. The movement of vehicles over proposed foundation areas should be restricted. 13) All foundation subgrade should be compacted with a vibratory plate compactor prior to placement of concrete. 14) Fill placed against the sides of the footings should be properly compacted in accordance with the Project Earthwork section of this report. FLOOR SYSTEMS/SLABS 1) Lightly loaded slab subgrade materials should be scarified to a minimum depth of 12 inches and re -compacted in accordance with the Project Earthwork section of this report subgrade vertical modulus (K) of 30 tcf may be utilized for lightly loaded slabs supported by the site soils. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 16 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal 3 5 The prepared surface on which the slabs will be cast should be observed by the Geotechnical Engineer prior to placement of reinforcement. Exposed loose, soft, or otherwise unsuitable materials should be excavated and replaced with properly compacted fill, placed in accordance with the Project Earthwork section of this report. Slabs should be separated from all bearing walls and columns with slip joints, which allow unrestrained vertical movement. Joints should be observed periodically, particularly during the first several years after construction. Slab movement can cause previously free -slipping joints to bind. Measures should be taken to assure that slab isolation is maintained in order to reduce the likelihood of damage to walls and other interior improvements. Interior partitions (if applicable) resting on floor/concrete slabs should be provided with slip joints so that if the slabs move, the movement cannot be transmitted to the upper structure. This detail is also important for wallboards and door frames. A slip joint, which will allow at least I or more inches of vertical movement should be utilized. If slip joints are placed at the tops of walls, in the event that the slabs move, it is likely that the wall will show signs of distress, especially where the slabs meet the exterior wall. Concrete slabs -on -grade should be placed on properly prepared subgrade. They should also be constructed and cured according to applicable standards and be provided with properly designed and constructed control joints. The design and construction of such joints should account for cracking as a result of shrinkage, tension, and loading; curling; as well as proposed slab use. Joint layout based on the slab design may require more frequent, additional, or deeper joints, and should also be based on the ultimate use and configuration of the slabs. Areas where slabs consist of interior corners or curves (at column blockouts or around corners) or where slabs have high length to width ratios, high degree of slopes, thickness transitions, high traffic loads, or other unique features should be carefully considered. The improper placement or construction of control joints will increase the potential for slab cracking. A I , AASHTO, a n d Job No. 14-3559 Ground Engineering Consultants, Inc. Page 17 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal other industry groups provide many guidelines for proper design and construction of concrete slabs -on -grade and the associated jointing. Slabs should be adequately reinforced. Structural considerations for slab thickness, jointing, and steel reinforcement in floor slabs should be developed by the Structural Engineer. Placement of slab reinforcement continuously through the control joint alignments will tend to increase the effective size of concrete panels and reduce the effectiveness of control joints. All plumbing lines should be carefully tested before operation. Where plumbing lines enter through the floor, a positive bond break should be provided. Flexible connections allowing 2 or more inches of vertical movement should be provided for slab -bearing mechanical equipment. 10) Moisture can be introduced into a slab subgrade during construction and additional moisture will be released from the slab concrete as it cures. The placement of a properly compacted layer of free -draining gravel, 6 or more inches in thickness, beneath the slabs should be performed. This layer will help distribute floor slab loadings, ease construction, reduce capillary moisture rise, and aid in drainage. The free -draining gravel should contain less than 5 percent material passing the No. 200 Sieve, more than 50 percent retained on the No. 4 Sieve, and a maximum particle size of 2 inches. 11) The Client/Project Team should review the American Concrete Institute's (Ail) Sections 30113021 60 for additional guidance regarding slab on grade design and construction. Vapor Barriers should meet applicable performance standards as stated in ATM E 1745. Slab movements are directly related to the increases in moisture contents to the underlying soils after construction is completed. The precautions and parameters itemized above will not prevent the movement of floor slabs if the underlying materials are subjected to moisture fluctuations. However, these steps will reduce the damage if such movement occurs Job No. 14-3559 Ground Engineering Consultants, Inc. Page 18 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal MECHANICAL ROOMS/MECHANICAL PADS Often, slab -bearing mechanical roomslmechanical equipment are incorporated into projects. Our experience indicates these are located as partially below -grade or adjacent to the exterior of a structure. These elements should be founded on the same type of foundation/floor systems as the main structure. Furthermore, mechanical connections must allow for potential differential movements. WATER-SOLUBLE SULFATES The concentration of water-soluble sulfates measured in selected samples obtained from the test holes were approximately 0.01 to 0.15 percent (Table 1). Such concentrations of water-soluble sulfates represent a negligible to moderate degree of sulfate attack on concrete exposed to these materials. Degrees of attack are based on the scale of 'negligible,' 'moderate,' 'severe' and 'very severe' as described in the "Design and Control of Concrete Mixtures," published by the Portland Cement Association (PCA). The Colorado Department of Transportation (CDOT) utilizes a corresponding scale with 4 classes of severity of sulfate exposure (Class 0 to Class 3) as described in the published table below. REQUIREMENTS TO PROTECT AGAINST DAMAGE TO CONCRETE BY SULFATE ATTACK FROM EXTERNAL SOURCES OF SULFATE Severity of Sulfate Exposure Water Sulfate(SO4In In -Soluble [dry Soil (°1) Sulfate(SO4)ater Water (ppm) Cementitious Ratio (maximum) Cementitious Material Requirements Class 0 0.00 to 0.10 0 to 150 0.45 Class 0 Class 1 0.11 to 0.20 151 to 1500 0.45 Class 1 Class 2 0.21 to 2.00 1501 to 10,000 0.45 Class 2 Class 3 2.01 or greater 10,001 or greater 0.40 Class 3 Based on our test results and PCA and CDOT guidelines, GROUND recommends use of sulfate -resistant cement in all concrete exposed to site soil and bedrock, conforming to one of the following Class 1 requirements: (1) ASTM C 150 Type II or V; Class C fly ash shall not be substituted for cement. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 19 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal (2) ASTM 595 Type IP(MS) ) or I P(H ); Class C fly ash shall not be substituted for cement. (3) ASTM C 1157 Type MS or HS; Class C fly ash shall not be substituted for cement. (4) When ASTM C 150 Type III cement is allowed, as in Class E concrete, it shall have no more than 8 percent C3A. Glass C fly ash shall not be substituted for cement. When fly ash is used to enhance sulfate resistance, it shall be used in a proportion greater than or equal to the proportion tested in accordance to ASTM C 1012, shall be the same source and it shall have a calcium oxide content no more than 2.0 percent greater than the fly ash tested according to ASTM C 1012. In addition, all concrete used should have a minimum compressive strength of 4,000 psi. The contractor should be aware that certain concrete mix components affecting sulfate resistance including, but not limited to, the cement, entrained air, and fly ash, can affect workability, set time, and other characteristics during placement, finishing and curing. The contractor should develop mix(es) for use in project concrete which are suitable with regard to these construction factors, as well as sulfate resistance. A reduced, but still significant, sulfate resistance may be acceptable to the owner, in exchange for desired construction characteristics. SOIL CORROSIVITY The degree of risk for corrosion of metals in contact with soils commonly is considered to be in two categories: corrosion in undisturbed soils and corrosion in disturbed soils. The potential for corrosion in undisturbed soil is generally low, regardless of soil types and conditions, because it is limited by the amount of oxygen that is available to create an electrolytic cell. In disturbed soils, the potential for corrosion typically is higher, but is strongly affected by soil conditions for a variety of reasons but primarily soil chemistry. corrosivity analysis was performed to provide a general assessment of the potential for corrosion of ferrous metals installed in contact with earth materials at the site, based on the conditions existing at the time of GROUND's evaluation. Soil chemistry and physical property data including pH, oxidation-reduction (redox) potential, sulfides,and moisture content were obtained. Test results are summarized on Table 2. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 20 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Soil Resistivity In order to assess the "worst case" for mitigation planning, samples of materials retrieved from the test holes were tested for resistivity in the in the laboratory, after being saturated with water, rather than in the field. Resistivity also varies inversely with temperature. Therefore, the laboratory measurements were made at a controlled tern perature. Measurements of electrical resistivity indicated values of approximately 1,155 to 9,362 ohm -centimeters in samples of retrieved soils. The following table presents the relationship between resistivity and a qualitative corrosivity rating Corrosivity Ratings Based on Soil Resistivity Soil Resistivity (ohm -cm) Corrosivity Rating >20,000 Essentially non -corrosive 10,000 - 20,000 Mildly corrosive 5,000 — 10,000 Moderately corrosive 3,000 - 5,0►00 Corrosive 1,000 — 3,000 Highly corrosive <1,000 Extremely corrosive pH Where pH is less than 4.0, soil serves as an electrolyte; the pH range of about 6.5 to 7.5 indicates soil conditions that are optimum for sulfate reduction. in the pH range above 8.5, soils are generally high in dissolved salts, yielding a low soil resistivity3. Testing indicated pH values of approximately 8.4 to 5.5. The American Water Works Association (AWWA) has developed a point system scale used to predict corrosivity. The scale is intended for protection of ductile iron pipe but is valuable for project steel selection. When the scale equals 10 points or higher, protective measures for ductile iron pipe are suggested. The AWWA scale is presented below. The soil characteristics refer to the conditions at and above pipe installation depth 2 ASM International, 2003, Corrosion: Fundamentals, Testing and Protection, ASM Handbook, Volume 13k 3 American Water Works Association ANSI/AWWA C105/A21.5-05 Standard Job No. 14-3559 Ground Engineering Consultants, Inc. Page 21 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Table A. 1 Soil -test Evaluation 3 Soil Characteristic / Value Points Resistivity <1,500 ohm -cm 10 1,500 to 1,800 ohm -cm 8 1,800 to 2,100 ohm -cm 5 2,100 to 2,500 ohm -cm 2 2,500 to 3,000 ohm -cm 1 >3,000 ohm -cm 0 pH 0to2.0 5 2.0 to 4.0 3 4.0 to 6.5 0 6.5to7.5 0* 7.5to8.5 0 >8.5 3 Redox Potential < Q (negative values) 5 0 to +50 mV 4 +50 to +100 mV 3% >+100mV 0 Sulfide Content Positive 3% Trace 2 Negative 0 Moisture Poor drainage, continuously wet 2 Fair drainage, generally moist 1 Good drainage, generally dry 0 * If sulfides are present and low or negative redox-potential results (< 50 my) are obtained, add three points for this range. We anticipate that drainage at the site after construction will be good. Nevertheless, based on the values obtained for the soil parameters, the overburden soilslbedrock appear(s) to comprise a corrosive environment for metals. If additional information is needed regarding soil corrosivity, GROUND suggests contacting the American Water Works Association or a Corrosion Engineer. It should be noted, however, that changes to the site conditions during construction, such as the Job No. 14-3559 Ground Engineering Consultants, Inc. Page 22 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal import of other soils, or the intended or unintended introduction of off -site water, might alter corrosion potentials significantly. LATERAL EARTH PRESSURES Structures which are laterally supported and can be expected to undergo only a limited amount of deflection should be designed for "at -rest" lateral earth pressures. The cantilevered retaining structures will be designed to deflect sufficiently to mobilize the full active earth pressure condition, and may be designed for "active" lateral earth pressures. "Passive" earth pressures may be applied in front of the wall embedment to resist driving forces. The at -rest, active, and passive earth pressures in terms of equivalent fluid unit weight for the on -site backfill and CDOT Class I structure backfill are summarized on the table below. Base friction may be combined with passive earth pressure if the foundation is in a drained condition. The use of passive pressure under a saturated condition is not suggested. The values for the on -site material provided in the table below were approximated utilizing a unit weight of 113 pcf and a phi angle of 29 degrees based on the direct shear results, our laboratory testing program, and experience. Lateral Earth Pressures (Equivalent Fluid Unit Weights) Water At -Rest Active Friction Passive Material Type Condition (pcf) (pcf) (pcf} Coefficient On -Site Backfill Drained 58 39 325 0.37 COOT Structure and CDOT 6 ABC* Class Backfill Class 1 Drained 55 35 440 0.45 *Aggregate Base Course If the selected on -site soil meets the criteria for COOT class 1 structure backfill as indicated in the Project Earthwork section of this report, the lateral earth pressures for CDOT Class 1 structure backfill as shown on the above table may be used. To realize Job No. 14-3559 Ground Engineering Consultants, Inc. Page 23 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal the lower equivalent fluid unit weight, the selected structure backfill should be placed behind the wall to a minimum distance equal to the retained wall height. The lateral earth pressures indicated above are for a horizontal upper backfill slope. The additional loading of an upward sloping backfill as well as loads from traffic, stockpiled materials, etc., should be included in the wall design. GROUND can provide the adjusted lateral earth pressures when the additional loading conditions and site grading are clearly defined. PROJECT EARTHWORK The following information is for private improvements; public roadways or utilities should be constructed in accordance with applicable municipal l agency standards. General Considerations: Site grading should be performed as early as possible in the construction sequence to allow settlement of fills and surcharged ground to be realized to the greatest extent prior to subsequent construction. Prior to earthwork construction, vegetation, and other deleterious materials should be removed and disposed of off -site. Relic underground utilities should be abandoned in accordance with applicable regulations, removed as necessary, and properly capped. Topsoil present on -site should not be incorporated into ordinary fills. Instead, topsoil should be stockpiled during initial grading operations for placement in areas to be landscaped or for other approved uses. Existing Fill Soils: Although not obviously encountered in the test holes, man-made fill may exist on -site. Actual contents and composition of the man-made fill materials are not known; therefore, some of the excavated man-made fill materials may not be suitable for replacement as backfill. The Geotechnical Engineer should be retained during site excavations to observe the excavated fill materials and provide guidance for its suitability for reuse. Use of Existing Native Soils: Overburden soils that are free of trash, organic material, construction debris, and other deleterious materials are suitable, in general, for Job No. 14-3559 Ground Engineering Consultants, Inc. Page 24 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal placement as compacted fill. Organic materials should not be incorporated into project fills. Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) larger than 3 inches in maximum dimension will require special handling and/or placement to be incorporated into project fills. In general, such materials should be placed as deeply as possible in the project fills. A Geotechnical Engineer should be consulted regarding appropriate guidance for usage of such materials on a case -by -case basis when such materials have been identified during earthwork. Standard guidelines that likely will be generally applicable can be found in Section 203 of the current CDOT Standard Specifications for Road and Bridge Construction. Imported Fill Materials: If it is necessary to import material to the site, the imported soils should be free of organic material, and other deleterious materials. Imported material should consist of relatively impervious soils that have less than 40 percent passing the No. 200 Sieve and should have a plasticity index of less than 15. Representative samples of the materials proposed for import should be tested and approved by the Geotechnical Engineer prior to transport to the site. Imported Structure Fill Select granular materials imported for use as structural fill should meet the criteria for CDOT Class 1 Structure Backfill as tabulated below. Representative samples of proposed imported structural fill should be tested and approved by GROUND prior to transport to the site. CDOT Class I Structure Backfill Sieve Size or Parameter Acceptable Range 2 -inch Sieve 100% passing No. 4 Sieve 30% to 100% passing No. 60 Sieve 10% to 60% passing No. 200 Sieve 5% to 20% passing Liquid Limit < 35 % Plasticity Index < 6 % a Job No. 14-3559 Ground Engineering Consultants, Inc. Page 25 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Imported Amiregate Base Course Select granular materials imported for use as base course should meet the criteria for CDOT Class 6 Aggregate Base Course as tabulated below. Representative samples of proposed material should be tested and approved by GROUND prior to transport to the site. CDOT Class 6 Aggregate Base Course Sieve Size or Parameter Acceptable Range 3/4 -inch Sieve 100% passing No. 4 Sieve 30% to 65% passing No. 8 Sieve 25% to 55% passing No. 200 Sieve 3% to 12% passing Liquid Limit < 30 % Fill Platform Preparation: Prior to filling, the top 8 to 12 inches of in -place materials on which fill soils will be placed should be scarified, moisture conditioned and properly compacted in accordance with the parameters below to provide a uniform base for fill placement. If over -excavation is to be performed, then these parameters for subgrade preparation are for the subgrade below the bottom of the specified over -excavation depth. If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material, additional material should be excavated, or other measures taken to establish a firm platform for filling. The surfaces to receive fill must be effectively stable prior to placement of fill. Fill Placement: Fill materials should be thoroughly mixed to achieve a uniform moisture content, placed in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted. Soils that classify as GP, GW, GM, GC, SP, SW, SM, or SC in accordance with the USCS classification system (granular materials) should be compacted to 95 or more percent of the maximum modified Proctor dry density at moisture contents within 2 percent of optimum moisture content as determined by ASTM D1557. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 26 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Soils that classify as ML, MH, , CL or CH should be compacted to 95 percent of the maximum standard Proctor density at moisture contents from 1 percent below to percent above the optimum moisture content as determined by ASTM D698. No fill materials should be placed, worked, rolled while they are frozen, thawing, or during poor/inclement weather conditions. Care should be taken with regard to achieving and maintaining proper moisture contents during placement and compaction. Materials that are not properly moisture conditioned may exhibit significant pumping, rutting, and deflection at moisture contents near optimum and above. The contractor should be prepared to handle soils of this type, including the use of chemical stabilization, if necessary. Compaction areas should be kept separate, and no lift should be covered by another until relative compaction and moisture content within the ranges are obtained. Use of Squeegee: Relatively uniformly graded fine gravel or coarse sand, i.e., "squeegee," or similar materials commonly are proposed for backfilling foundation excavations, utility trenches (excluding approved pipe bedding), and other areas where employing compaction equipment is difficult. Although commonly considered "self compacting," uniformly graded granular materials require densification after placement, typically by vibration. The equipment to densify these materials is not available on many► job -sites. Even when properly densified, uniformly graded granular materials are permeable and allow water to reach and collect in the lower portions of the excavations backfilled with those materials. This leads to wetting of the underlying soils and resultant potential loss of bearing support as well as increased local heave or settlement. Wherever possible, excavations be backfilled with approved, on -site soils placed as properly► compacted fill. Where this is not feasible, use of "Controlled Low Strength Material" (CLSM), i.e., a lean, sand -cement slurry ("flowable fill") or a similar material for backfilling should be considered. Where "squeegee" or similar materials are proposed for use by the contractor, the design team should be notified by means of a Request for Information (RFI), so that the Job No. 14-3559 Ground Engineering Consultants, Inc. Page 27 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal proposed use can be considered on a case -by -case basis. Where "squeegee" meets the project requirements for pipe bedding material, however, it is acceptable for that use. Settlements: Settlements will occur in filled ground, typically on the order of 1 to percent of the fill depth. If fill placement is performed properly and is tightly controlled, in GROUND's experience the majority (on the order of 60 to 80 percent) of that settlement will typically take place during earthwork construction, provided the contractor achieves the compaction levels indicated herein. The remaining potential settlements likely will take several months or longer to be realized, and may be exacerbated if these fills are subjected to changes in moisture content. Cut and Filled Slopes: Permanent site slopes supported by on -site soils up to 10 feet in height may be constructed no steeper than 3:1 (horizontal : vertical). Minor raveling or surfcial sloughing should be anticipated on slopes cut at this angle until vegetation is well re-established. Surface drainage should be designed to direct water away from slope faces. EXCAVATION CONSIDERATIONS The test holes for the subsurface exploration were excavated to the depths indicated by means of truck -mounted, flight auger drilling equipment. We anticipate no significant excavation difficulties in the majority of the site with conventional heavy-duty excavation equipment in good working condition. Temporary, un-shored excavation slopes up to 10 feet in height should be cut no steeper than 1.5 (H) to 1 (V) in the on -site soils in the absence of seepage. Some surface sloughing may occur on the slope faces at these angles. Where seepage or flowing groundwater is encountered in shallow project excavations, the Geotechnical Engineer should be retained to evaluate the conditions and provided additional information, as appropriate. The risk of slope instability will be significantly increased in areas of seepage along excavation slopes. Should site constraints prohibit the use of the indicated slope angles, temporary shoring should be used. The shoring should be designed to resist the lateral earth pressure exerted by structure, traffic, equipment, and stockpiles. GROUND can provide shoring design upon request under separate contract. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 28 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Groundwater was encountered in some of the test holes at depth ranging from approximately 18 to 27 feet (elevations of approximately 4,769 to 4,778 feet) below existing grades at the time of drilling and at a depth of approximately 20 feet (elevation of approximately 4,777 feet) below existing grade when measured 7 days later. Based on the likely depths of excavation, groundwater is not anticipated to be a significant factor for shallow earthworks during construction of this project. If seepage or groundwater is encountered in shallow project excavations, the Geotechnical Engineer should be retained to evaluate the conditions and provided additional parameters, as appropriate. Good surface drainage should be provided around temporary excavation slopes to direct surface runoff away from the slope faces. A properly designed swale should be provided at the top of the excavations. In no case should water be allowed to pond at the site. Slopes should be protected against erosion. Erosion along the slopes will result in sloughing and could lead to a slope failure. Any excavations in which personnel will be working must comply with all OSHA Standards and Regulations (CFR 29 Part 1926). The contractor's "responsible person" should evaluate the soil exposed in the excavations as part of the contractor's safety procedures. GROUND has provided the information above solely as a service to the client, and is not assuming responsibility for construction site safety or the contractor's activities. UTILITY PIPE INSTALLATION AND BACKFILLING Pipe Support: The bearing capacity of the site soils appeared adequate, in general, for support of the proposed water line. The pipe + water are less dense than the soils which will be displaced for installation. Therefore, GROUND anticipates no significant pipe settlements in these materials where properly bedded. Excavation bottoms may expose soft, loose or otherwise deleterious materials, including debris. Firm materials may be disturbed by the excavation process. All such unsuitable materials should be excavated and replaced with properly compacted fill. Areas allowed to pond water will require excavation and replacement with properly compacted fill. The contractor should take particular care to ensure adequate support near pipe joints which are less tolerant of extensional strains. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 29 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Where thrust blocks are needed, they may be designed for an allowable passive soil pressure of 320 psf per foot of embedment, to a maximum of 3,200 psf. Sliding friction at the bottom of thrust blocks may be taken as 025 times the vertical dead load. Trench Backfilling: Some settlement of compacted soil trench backfill materials should be anticipated, even where all the backfill is placed and compacted correctly. Typical settlements are on the order of 1 to 2 percent of fill thickness. However, the need to compact to the lowest portion of the backfill must be balanced against the need to protect the pipe from damage from the compaction process. Some thickness of backfill may need to be placed at compaction levels lower than specified (or smaller compaction equipment used together with thinner lifts) to avoid damaging the pipe. Protecting the pipe in this manner can result in somewhat greater surface settlements. Therefore, although other alternatives may be available, the following options are presented for consideration: Controlled Low Strength Material: Because of these limitations, backfilling the entire depth of the trench (both bedding and common backfill zones) with "controlled low strength material" (CLSM), i.e., a lean, sand -cement slurry, 'Towable fill," or similar material along all trench alignment reaches with low tolerances for surface settlements should be performed. CLSM should be used as pipe bedding and trench that exhibits a 28 -day unconfined compressive strength between 50 to 200 psi so that re -excavation is not unusually difficult. Placement of the CLSM in several lifts or other measures likely will be necessary to avoid `floating' the pipe. Measures also should be taken to maintain pipe alignment during CLSM placement. Compacted Soil Backfilling: Where compacted soil backfilling is employed, using the site soils or similar materials as backfill, the risk of backfill settlements entailed in the selection of this higher risk alternative must be anticipated and accepted by the Client/Rcaner. We anticipate that the on -site soils excavated from trenches will be suitable, in general, for use as common trench backfill within the above -described limitations. Backfill soils Job No. 14-3559 Ground Engineering Consultants, Inc, Page 30 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal should be free of vegetation, organic debris and other deleterious materials. Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) coarser than inches in maximum dimension should not be incorporated into trench backfills. If it is necessary to import material for use as backfill, the imported soils should be free of vegetation, organic debris, and other deleterious materials. Imported material should consist of relatively impervious soils that have less than 40 percent passing the No. 200 Sieve and should have a plasticity index of less than 15. Representative samples of the materials proposed for import should be tested and approved prior to transport to the site. Soils placed for compaction as trench backfill should be conditioned to a relatively uniform moisture content, placed and compacted in accordance with the Project Earthwork section of this report. Pipe Bedding: Pipe bedding materials, placement and compaction should meet the specifications of the pipe manufacturer and applicable municipal standards. Bedding should be brought up uniformly on both sides of the pipe to reduce differential loadings. As discussed above, the use of CLSM or similar material in lieu of granular bedding and compacted soil backfill should be considered where the tolerance for surface settlement is low. (Placement of CLSM as bedding to at least 12 inches above the pipe can protect the pipe and assist construction of a well -compacted conventional backfill, although possibly at an increased cost relative to the use of conventional bedding.) If a granular bedding material is specified, in regard to potential migration of fines into the pipe bedding, design and installation follow ABTM D2321. If the granular bedding does not meet filter criteria for the enclosing soils, then non -woven filter fabric (e.g., Mirafi® 140N, or the equivalent) should be placed around the bedding to reduce migration of fines into the bedding which can result in severe, local surface settlements. Where this protection is not provided, settlements can develop/continue several months or years after completion of the project. In addition, clay or concrete cut-off wails should be installed to interrupt the granular bedding section to reduce the rates and volumes of water transmitted along the sewer alignment which cancontribute to migration of fines. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 31 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal If granular bedding is specified, the contractor should anticipate that significant volumes of on -site soils may not be suitable for that use. Materials proposed for use as pipe bedding should be tested by a geotechnical engineer for suitability prior to use. Imported materials should be tested and approved by a geotechnical engineer prior to transport to the site. SURFACE DRAINAGE The site soils are relatively stable with regard to moisture content — volume relationships at their existing moisture contents. Other than the anticipated, post -placement settlement of fills, post -construction soil movement will result primarily from the introduction of water into the soil underlying the proposed structure, hardscaping, and pavements. Based on the site surface and subsurface conditions encountered in this study, we do not anticipate a rise in the local water table sufficient to approach grade beam or floor elevations. Therefore, wetting of the site soils likely will result from infiltrating surface waters (precipitation, irrigation, etc.), and water flowing along constructed pathways such as bedding in utility pipe trenches. The following drainage measures should be incorporated as part of project design and during construction. The facility should be observed periodically to evaluate the surface drainage and identify areas where drainage is ineffective. Routine maintenance of site drainage should be undertaken throughout the design life of the project. If these measures are not implemented and maintained effectively, the movement estimates provided in this report could be exceeded. 1) Wetting or drying of the foundation excavations and underslab areas should be avoided during and after construction as well as throughout the improvements' design life. Permitting increases/variations in moisture to the adjacent or supporting soils may result in a decrease in bearing capacity and an increase in volume change of the underlying soils, and increased total and/or differential movements. 2 Positive surface drainage measures should be provided and maintained to reduce water infiltration into foundation soils. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 32 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal The ground surface surrounding the exterior of each structure should be sloped to drain away from the foundation in all directions. A minimum slope of 12 inches in the first 10 feet should be incorporated in the areas not covered with pavement or concrete slabs, or a minimum 3 percent in the first 10 feet in the areas covered with pavement or concrete slabs. Reducing the slopes to comply with ADA requirements may be necessary by other design professionals but may entail an increased potential for moisture infiltration and subsequent volume change of the underlying soils and resultant distress. In no case should water be allowed to pond near or adjacent to foundation elements, hardscaping, utility trench alignments, etc. Drainage should be established and maintained to direct water away from sidewalks and other hardscaping as well as utility trench alignments. Where the ground surface does not convey water away readily, additional post -construction movements and distress should be anticipated. In GROUND's experience, it is common during construction that in areas of partially completed paving or hardscaping, bare soil behind curbs and gutters, and utility trenches, water is allowed to pond after rain or snow -melt events. Wetting of the subgrade can result in loss of subgrade support and increased settlements / increased heave. By the time final grading has been completed, significant volumes of water can already have entered the subgrade, leading to subsequent distress and failures. The contractor should maintain effective site drainage throughout construction so that water is directed into appropriate drainage structures. As stated, slopes descend toward facility. In such cases, even where the slopes as described above are implemented effectively, water may flow toward a n d beneath a structure or other site improvements with resultant additional, post - construction movements. Where the final site configuration includes graded or retained slopes descending toward the improvements, surface drainage swales and/or interceptor drains should be installed between the improvements and the slope. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 33 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Where irrigation is applied on or above slopes, drainage structures commonly are needed near the toe -of -slope to prevent on -going or recurrent wet conditions. Roof downspouts and drains should discharge well beyond the perimeter of the structure foundations (minimum 10 feet) and backfill zones and be provided with positive conveyance off -site for collected waters. Maintenance as described herein may include complete removal and replacement of site improvements in order to maintain effective surface drainage. Detention ponds commonly are incorporated into drainage design. When a detention ponds fills, the rate of release of the water is controlled and water is retained in the pond for a period of time. Where in -ground storm sewers direct surface water to the pond, the granular pipe bedding also can direct shallow groundwater or infiltrating surface water toward the pond.. Thus, detention ponds can become locations of enhanced and concentrated infiltration into the subsurface, leading to wetting of foundation soils in the vicinity with consequent heave or settlement, Therefore, unless the pond is clearly down -gradient from the proposed buildings and other structures that would be adversely affected by wetting of the subgrade soils, including off -site improvements, the detention pond should be provided with an effective, low permeability liner. In addition, cut-off walls and/or drainage provisions should be provided for the bedding materials surrounding storm sewer lines flowing to the pond, SUBSURFACE DRAINAGE As a component of project civil design, properly functioning, subsurface drain systems (underdrains) can be beneficial for collecting and discharging saturated subsurface waters. Underdrains will not collect water infiltrating under unsaturated (vadose) conditions, or moving via capillarity, however. In addition, if not properly constructed and maintained, underdrains can transfer water into foundation soils, rather than remove it. This will tend to induce heave or settlement of the subsurface soils, and may result in distress. Underdrains can, however, provide an added level of protection against relatively severe post -construction movements by draining saturated conditions near individual structures should they arise, and limiting the volume of wetted soil. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 34 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Although inclusion of an underdrain system is common on commercial sites like the subject facility, particularly where shallow foundations are used, professional opinion varies regarding the potential benefits relative to the cost. Therefore, the owner and the design team and contractor should assess the net benefit of an underdrain system as a component of overall project drainage. If, however, below -grade or partially below -grade level(s) are added, an underdrain system should be included. Damp -proofing should be applied to the exteriors of below - grade elements. The provision of Tencate MiraFia -series backing (or comparable wall drain provisions) on the exteriors of (some) below -grade elements may be appropriate, depending on the intended use. If a (partially) below -grade level is limited in extent, the underdrain system, etc., may be local to that area. Geotechnical Parameters for Underdrain Design The underdrain system should be designed in accordance with the recommendations below. The actual underdrain layout, outlets, and locations should be developed by a civil engineer. The underdrain system should be tested by the contractor after installation and after placement and compaction of the overlying backfill to verify that the system functions properly. 1 The underdrain system should consist of perforated, rigid, PVC collection pipe at least 6 inches in diameter, non -perforated, rigid, PVC discharge pipe at least inches in diameter, free -draining gravel, and filter fabric. 2 The free -draining gravel should contain less than 5 percent passing the No. 200 Sieve and more than 50 percent retained on the No. 4 Sieve, and have a maximum particle size of 2 inches. Each collection pipe should be surrounded on the sides and top (only) with 6 or more inches of free -draining gravel. 3) The gravel surrounding the collection pipe(s) should be wrapped with filter fabric (MiraFi 140N® or the equivalent) to reduce the migration of fines into the drain system. 4 The underdrain system should be designed to discharge at least 5 gallons per minute of collected water. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 35 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal 5 6 The high points) for the collection pipe flow lines should be below the grade beam or shallow foundation bearing elevation. Multiple high points can be beneficial to reducing the depths to which the system would be installed. The collection and discharge pipe for the underdrain system should be laid on a slope sufficient for effective drainage, but a minimum of 1 percent. (Flatter gradients may be used but will convey water less efficiently and entail an increased risk of local post -construction movements.) Underdrain `clean -outs' should be provided at intervals of no more than 100 feet to facilitate maintenance of the underdrains. Clean -outs also should be provided at collection and discharge pipe elbows of 60 degrees or more. 7) The underdrain discharge pipes should be connected to one or more sumps from which water can be removed by pumping, or to outlet(s) for gravity discharge. We suggest that collected waters be discharged directly into the storm sewer system, if possible. EXTERIOR SITE CONCRETE Concrete Scaling Surface scaling of flatwork and other exterior concrete can result from poor workmanship during construction, such as 'over -finishing' the surface. It also can result from exposure to relatively severe weather conditions with repeated freeze - thaw cycles. In GROUND's experience, if reducing the potential for freeze -thaw scaling is a design consideration, the following measures are beneficial: a) Maintaining a maximum water/cement ratio of 0.45 by weight for exterior concrete. b) Including Type F fly ash in the mix for exterior concrete as 20 percent of the cementitious material. Use of exterior concrete that exhibits a minimum compressive strength of 4,500 psi. Inclusion of `fibermesh' in the concrete mix also may be beneficial for reducing surficial scaling. (These concrete mix design criteria should be Job No. 14-3559 Ground Engineering Consultants, Inc. Page 36 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal coordinated with other project requirements including the criteria forsulfate resistance presented in the Water -Soluble Sulfates section of this report). In addition, the use of de-icing salts on exterior concrete flatwork during the first winter after construction will increase the likelihood of the development of scaling. Placement of flatwork concrete during cold weather so that it is exposed to freeze -thaw cycling before it is fully cured also increases its vulnerability to scaling. Concrete placing during cold weather conditions should be blanketed or tented to allow full curing. Depending on the weather conditions, this may result in 3 to 4 weeks of curing, and possibly more. Frost and Ice Considerations Nearly all soils other than relatively coarse, clean,. granular materials are susceptible to loss of density if allowed to become saturated and exposed to freezing temperatures and repeated freeze — thaw cycling. The formation of ice in the underlying soils can result in heaving of pavements, flatwork and other hardscaping ("ice jacking") in sustained cold weather of 2 inches or more. This heaving can develop relatively rapidly. A portion of this movement typically is recovered when the soils thaw, but due to loss of soil density some degree of displacement typically will remain. This can result even where the subgrade soils were prepared properly. Where hardscape movements are a design concern, e.g., at doorways, replacement of the subgrade soils with 3 or more feet of dean, coarse sand or gravel with a drain should be considered, or the element supported on foundations similar to the building and spanning over a void. Detailed information in this regard can be provided upon request. It should be noted that where such open graded granular soils are placed, water can infiltrate and accumulate in the subsurface relatively easily, which can lead to increased settlement or heave from factors unrelated to ice formation. The relative risks from these soil conditions should be taken into consideration where ice jacking is a concern. GROUND will be available to discuss these concerns upon request. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 37 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal GRAVEL ROAD SECTION GROUND understands that gravel surfaced access areas/roads may be constructed. Based on our experience with similar facilities, traffic for the facility will consist of 20 passenger trucks per day, three 8,000 gallon tanker trucks on a weekly basis, and heavier maintenance trucks and cranes approximately once over three months. Based on our experience with similar facilities, at least 12 inches of naturally occurring CDOT Class 6 aggregate base course should be utilized. Another section that may be considered that is currently desired by the client is a section consisting of a minimum of 4 inches of CDOT Class 6 aggregate base course overlaying a minimum of 8 inches of COOT Class 2 aggregate base course placed on a layer of woven geotextile (US Fabric's US 50 or approved equal). This material should be compacted to at least 95 percent of the maximum modified Proctor dry density. It should be noted that CDOT Class 2 and 6 aggregate base course may be difficult to maintain and as a result, some rutting may occur over time. If water infiltrates these areas, additional rutting and other distress may occur. Therefore, GROUND recommends that regular maintenance be developed and implemented to ensure proper subsurface and surface drainage, repaired distressed areas, and performance of grading and leveling operations. Application of additional aggregate may be required. In the event a pavement section consisting of asphalt and/or concrete is desired, we should be notified to provide these recommendations. CLOSURE Geotechnical Review The author of this report should be retained to review project plans and specifications to evaluate whether they comply with the intent of the information in this report. The review should be requested in writing. The geotechnical information presented in this report are contingent upon observation and testing of project earthworks by representatives of GROUND. If another geotechnical consultant is selected to provide materials testing, then that consultant must assume all responsibility for the geotechnical aspects of the project by concurring in writing with the information in this report, or by providing alternative parameters. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 38 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal Materials Testing The client should consider retaining a Geotechnical Engineer to perform materials testing during construction. The performance of such testing or lack thereof, in no way alleviates the burden of the contractor or subcontractor from constructing in a manner that conforms to applicable project documents and industry standards. The contractor or pertinent subcontractor is ultimately responsible for managing the quality of their work; furthermore, testing by the geotechnical engineer does not preclude the contractor from obtaining or providing whatever services they deem necessary to complete the project in accordance with applicable documents. Limitations This report has been prepared Anadarko Petroleum Corporation as it pertains to design of the proposed St. Frain Compressor Station as described herein. It may not contain sufficient information for other parties or other purposes. The owner or any prospective buyer relying upon this report must be made aware of and must agree to the terms, conditions, and liability limitations outlined in the proposal. In addition, GROUND has assumed that project construction will commence by Spring/Summer 2014. Any changes in project plans or schedule should be brought to the attention of the Geotechnical Engineer, in order that the geotechnical parameters may be re-evaluated and, as necessary, modified. The geotechnical conclusions and information in this report relied upon subsurface exploration at a limited number of exploration points, as shown in Figure 1, as well as the means and methods described herein. Subsurface conditions were interpolated between and extrapolated beyond these locations. It is not possible to guarantee the subsurface conditions are as indicated in this report. Actual conditions exposed during construction may differ from those encountered during site exploration. If during construction, surface, soil, bedrock, or groundwater conditions appear to be at variance with those described herein, the Geotechnical Engineer should be advised at once, so that re-evaluation may be made in a timely manner. In addition, a contractor who relies upon this report for development of his scope of work or cost estimates may find the geotechnical information in this report to be inadequate for his purposes or find Job No. 14-3559 Ground Engineering Consultants, Inc. Page 39 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal the geotechnical conditions described herein to be at variance with his experience in the greater project area. The contractor is responsible for obtaining the additional geotechnical information that is necessary to develop his workscope and cost estimates with sufficient precision. This includes current depths to groundwater, etc. The materials present on -site are stable at their natural moisture content, but may change volume or lose bearing capacity or stability with changes in moisture content. Performance of the proposed structures will depend on implementation of the parameters in this report and on proper maintenance after construction is completed. Because water is a significant cause of volume change in soils and rock, allowing moisture infiltration may result in movements, some of which will exceed estimates provided herein and should therefore be expected by the owner. This report was prepared in accordance with generally accepted soil and foundation engineering practice in the project area at the date of preparation. Current applicable codes may contain criteria regarding performance of structures and/or site improvements which may differ from those provided herein. Our office should be contacted regarding any apparent disparity. GROUND makes no warranties, either expressed or implied, as to the professional data, opinions or information contained herein. Because of numerous considerations that are beyond GROUND's control, the economic or technical performance of the project cannot be guaranteed in any respect. ALL DEVELOPMENT CONTAINS INHERENT RISKS, it is important that ALL aspects of this report, as well as the estimated performance (and limitations with any such estimations) of proposed project improvements are understood by the Client, Project Owner (if different), or properly conveyed to any future owner(s). Utilizing these it for planning, design, and/or construction constitutes understanding and acceptance of the information provided herein, potential risks, associated improvement performance, as well as the limitations inherent within such estimations. If any information referred to herein is not well understood, it is imperative for the Client, Owner (if different), or anyone using this report to contact the author or a company principal immediately. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 40 of 41 St. Vrain Compressor Station County Road 34 and County Road 19 Weld County, Colorado Final Submittal GROUND appreciates the opportunity to complete this portion of the project and welcomes the opportunity to provide the Owner with a cost proposal for construction observation and materials testing prior to construction commencement. Sincerely, GROUND Engineering Consultants, Inc. Amy Crandall, P.E. Reviewed by Jason A. Smith, R.E.M., P.E. Job No. 14-3559 Ground Engineering Consultants, Inc. Page 41 of 41 14[ —13 F 12: It 'T. .1 1 � Indicates test hole number and approximate location. —S. I - lip I rrEE -i • i I r T 1 nr- rt i s IlL eifr 1 SW p 3 I l P}'IIN1Y RCIM I $-1/2 IEu\.IGIONEERO MS CCONSUILTFMITS LOCATION OF TEST HOLES (Not to Scale) JOB NO.: 14-3559 FIGURE: 1 CADFILE NAME: 3559S ITE.DWG 4800 4790 4780 a _c 4770 I) w 4760 4750 4740 Test Hole 1 Elev. 4796.22' 0 .7,,, '♦♦♦♦ , / irI ♦ 5/12 4/12 16/12 11/12 18/12 142/12 125/12 121/12 I 50/10 7/12 Test Hole 2 Elev. 4797.30' r-; .,l r r./.♦ 0 I I I I I I I I I 11/12 8/12 9/12 41/12 34/12 37/12 28/12 50/11 11/12 32/12 Test Hole 3 Elev. 4796.77' art♦♦' 'C,♦♦♦' r, /I 9/12 `yr. i♦♦ 7 6 I 6/12 12/12 28/12 134/12 I I ID 29/12 18/12 6/12 37/12 ID 50/11 Test Hole 4 Elev. 4795.97' 0 r r \ I I I I I I I I I I 10112 6/12 10/12 30/12 18/12 32/12 26/12 23/12 32/12 28/12 Test Hole 5 Elev. 4798.39' 0 I I I I I I I I I I 13/12 6/12 9/12 8/12 15112 45112 50111 42/12 50/12 10/12 EN1 O EEPD1 S CONSULTFONITE LOGS OF TEST HOLES , JOB NO.: 14-3559 FIGURE: 2 CADFILE NAME: 3559L0 01.DW 4800 4790 4780 75 o _x4770 I) w 4760 4750 4740 Test Hole 6 Elev. 4797.40' 0 ii ] 8/12 14/12 ] 10/12 ] 11/12 ] 8/12 ] 21/12 ] 26/12 ] 37/12 ] 20/12 ] 24/12 Test Hole 7 Elev. 4796.00' 0 r r.r•r / r•r•r ..*/*. rr'i"r / r'i" r / /./...0.1 / r.r.r � � '1 �`r. -fir, -�.- `\ 1 12/12 16/12 40/12 50/6 40/12 37/12 14/12 19/12 50/5 50/5 Test Hole 8 Elev. 4795.80' 0 I I I I I J I ID ID I 10/12 12112 16/12 18/12 22112 21/12 28112 7/12 28/12 28/12 Test Hole 9 Elev. 4798.80' 0 J I I I I I I J I I 6/12 10/12 15/12 37/12 45/12 50/6 41/12 18/12 33/12 8/12 Test Hole 10 Elev. 4797.60' 0 ii I I I I I I I I I 7/12 14/12 32/12 40/12 38/12 43/12 33/12 50112 41112 35/12 EN1 O EERO S CONSULTFONITE LOGS OF TEST HOLES JOB NO.: 14-3559 FIGURE: 3 CADFILE NAME: 3559L0 02.DW 4800 4790 4780 w 4760 4750 4740 Test Hole 11 Elev. 4795.86' 0 ii I I I I I I I I I I 12/12 22/12 20/12 22/12 24/12 28/12 35/12 8/12 30/12 14/12 Test Hole 12 Elev. 4799.70' 0 I I I I I I I J 9/12 14/12 27/12 30/12 50/6 45/12 50/6 50/6 40/12 50/6 Test Hole 13 Elev. 4798.90' 0 I I I I I I I I 8/12 14/12 28/12 14/12 16/12 34/12 Test Hole 14 Elev. 4796.04' 40/12 0 39/12 33/12 47/12 11 II II II 11 11 II 11 II I I I I I I I I I 10/12 28/12 20/12 24/12 28/12 25/12 35/12 40/12 37/12 Test Hole 15 Elev. 4797.30' 0 • / F.//. / • // I/ / . . / / • / • / 1' . /, •//•/•/ •/r// •/::/:/ • f /./. / • / e• r / •//*// •//'f/ •/e.e./ • / 1././ 9 / 44/ • / .0..4/ • / ,./. / • / 7/ / • / 7/ A • / / / / • / f. e'. / •/•e./,/ 9/12 15/12 26/12 24/12 27/12 21/12 14/12 50/10 29/12 EN1O1 EIERO S CONSULTF0NITE LOGS OF TEST HOLES JOB NO.: 14-3559 FIGURE: 4 CADFILE NAME: 8559LO 03.DW 4800 4790 4780 W 4760 4750 4740 Test Hole 16 Elev. 4798.34' 0 I ii I I I I I I I 8/12 12/12 14/12 16/12 28/12 26112 24112 4/12 11/12 Test Hole 17 Elev. 4797.14' 0 ii / r•r•r / /5/5/ / r'r'r //'I'? ..':'• / //S/ ....•./ / /5/5/ .. •F•, / /•r•r / r•r•r / /77 / r'/'2 / r/:e / /.•./ /.de., / r•r•r / r ....• / r •r • r • ••r.r / i'i'i ///.• / /.r.r f f•v./ 6/12 5/12 9/12 12/12 24/12 19/12 20/12 9/12 16/12 Test Hole 18 Elev. 4796.84' 0 I I I I I I I 12/12 8/12 9/12 27/12 21/12 Test Hole 19 Elev. 4798.52' 14/12 0 10/12 50/9 35/12 11 II II 11 II I I I I I I I I I 7/12 9/12 14/12 22/12 14/12 31/12 50/11 8/12 30/12 Test Hole 20 Elev. 4797.56' 0 li I I I I I I I I I 14/12 12/12 10/12 17/12 19/12 20/12 28/12 10/12 20/12 ENSONEIERONS CONSULTFONITE LOGS OF TEST HOLES • JOB NO.: 14-3559 FIGURE: 5 CADFILE NAME: 3559L0 04.DW 4800 4790 4780 w 4760 4750 4740 Test Hole 21 Elev. 4798.50' 0 ii 16/12 15/12 16/12 26/12 27/12 22/12 14/12 I 15/12 50/10 Test Hole 22 Elev. 4797.51' 0 / /.1.1 / /././ / /././ / /*/•/ / /7'7 15/12 21/12 14/12 12/12 15/12 16/12 6112 20/12 33/12 ENSONEERONS CONSULTFONITE LOGS OF TEST HOLES , JOB NO.: 14-3559 FIGURE: 6 CADFILE NAME: 3559L0 05.DW LEGEND: IN, ID Topsoil Sand: Silty to clayey with gravel lenses, fine to gravel grained, non -plastic to medium plastic, loose to dense, moist, tan to brown in color, and occasionally calcareous. Sand and Clay: Interbedded, fine to medium grained, low to highly plastic, loose to dense/medium to very stiff, moist, brown in color, and occasionally calcareous. Drive sample, 2 -inch I.D. California liner sample 23/12 Drive sample blow count, indicates 23 blows of a 140 -pound hammer falling 30 inches were required to drive the sampler 12 inches. 0 NOTES: Caved Hole Depth to water level and number of days after drilling that measurement was taken. 1) Test holes were drilled on 03/27/2014 and 04/26/2014 with 4 -inch diameter continuous flight augers. 2) Locations of the test holes were professionally surveyed by a representative of the client for and approximate location and shown on the site plan provided. elevation pp e c p e 3) Elevations of the test holes were not measured and the logs of the test holes are drawn to elevation. 4) The test hole locations and elevations should be considered accurate only to the degree implied by the method used. 5) The lines between materials shown on the test hole logs represent the approximate boundaries between material types and the transitions may be gradual. 6) Groundwater level readings shown on the logs were made at the time and under the conditions indicated. Fluctuations in the water level may occur with time. 7) The material descriptions on this legend are for general classification purposes only. See the full text of this report for descriptions of the site materials and related recommendations. ENSON1EI ONG CD SULT( INTS LEGEND AND NOTES JOB NO.: 14-3559 FIGURE: 7 CADFILE NAME: 3559LEG.DWG R OUD ENGINEERING CONSULTRNTS TABLE "1 SUMMARY OF LABORATORY TEST RESULTS Sample Location Natural Moisture Content (%) Natural Dry Density (pcf) Gradation Percent Passing No. 200 Sieve Atterberg Limits Percent Swell (Surcharge Pressure(psf)) USCS Classifi- cation AASHTO Classifi- cation (GI) Soil or Bedrock Type Test Hole No. Depth (feet) Gravel (%) Sand (%) Liquid Limit Plasticity Index 1 2 20.3 99.2 - - 66 33 13 -2.3 (250) CL A-6(7) Sandy lean clay 1 4 7.2 106.5 - - 17 NV NP - SM A -1-b(0) Silty sand 1 8 2.3 S/D 24 74 2 NV NP - SW A -1-a(0) Sand with gravel 2 4 2.0 S/D 8 90 2 NV NP - SP A -1-b(0) Sand 2 6 2.6 112.7 21 75 4 NV NP - SW A -1-b(0) San.d with gravel 2 15 3.5 110.7 0 96 4 NV NP - SP A -1-b(0) Sand 3 4 15.0 100.0 - - 45 31 11 -0.5 (500) SC A-6(2) Clayey sand 3 35 15.3 111.5 7 75 18 NV NP - SP A-2-4(0) Silty sand 4 6 2.4 109.6 - - 2 NV NP - SP A -1-b(0) Sand 4 8 2.4 SID - - 3 NV NP - SP A -1-b(0) Sand 5 4 7.1 102.5 - - 15 NV NP - SM A -1-b(0) Silty sand 5 20 2.9 S/D 1 81 18 NV NP - SM A -1-b(0) Silty sand 6 2 10.3 110.0 - - 15 NV NP - SM A -1-b(0) Silty sand 6 10 7.5 101.8 - - 5 NV NP - SP-SM A -1-b(0) Sand with silt 7 2 35.2 87.3 - - 62 50 24 - CH A-7-6(13) Sand fat clay 7 6 1.9 S/D - - 2 NV NP - SP A -1-b(0) Sand 8 15 2.9 108.3 1 96 3 NV NP - SP A -1-b(0) Sand 8 20 20.2 88.9 0 74 26 NV NP - SPv1 A-2-4(0) Silty sand 9 2 10.8 101.8 - - 11 NV NP - SP-SM A -1-b(0) Sand with silt 9 6 5.6 109.1 0 92 8 NV NP - SP-SM A-3(0) Sand with silt 10 4 6.2 104.6 0 91 9 NV NP - SP-SM A-3(0) Sand with silt 10 15 1.8 106.2 0 97 3 NV NP - SP A -1-b(0) Sand 11 20 21.2 103.5 - - 17 NV NP - SM A -1-b(0) Silty sand 11 30 9.9 113.6 33 61 6 NV NP - SW-SM A -1-b(0) Sand with silt and gravel 12 6 4.1 105.4 - - 6 NV NP - SP-SM A -1-b(0) Sand with silt 12 8 4.9 111.2 - - 6 NV NP - SP-SM A -1-b(0) Sand with silt 13 4 7.7 111.3 0 88 12 NV NP - SP-SM A-2-4(0) Sand with silt 13 25 16.8 98.1 0 92 8 NV NP - SP-SM A-3(0) Sand with silt 14 2 6.5 103.2 - - 11 NV NP - SP-SM A -1-b(0) Sand with silt 14 4 2.0 120.5 26 71 3 NV NP - SW A -1-a(0) Sand with gravel 3 Bulk 11.4* 124.7* - - 23 NV NP - SM A-2-4(0) Sand with Silt * Indicates optimum moisture content and maximum standard Proctor density (ASTM D-698) Job NO. 14-3559 GROUND ENGINEERING CONSULTFINTS TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Sample Location Natural Moisture Content (%) Natural Dry Density (pcf) Gradation Percent Passing No. 200 Sieve Atterberg Limits Percent Swell (Surcharge Pressure(psf)) USCS Classifi- cation AASHTO Classifi- cation (GI) Soil or Bedrock Type Test Hole No. Depth (feet) Gravel (%) Sand (%) Liquid Limit Plasticity Index 15 2.5 26.3 96.7 - - 87 62 35 0.1 (200) CH ,A-7-6(34) Sandy Clay 15 7.5 1.3 SID - - 7 NV NP - SP-SM A-2-4(0) Sand with Silt 16 2.5 5.8 97.8 12 74 14 26 9 - SC A-2-4(0) Clayey Sand 16 10 1.5 108.5 21 70 9 NV NP - SP-SM A -1-b(0) Sand with Silt 17 2.5 15.6 107.1 - - 57 34 12 0.1 (200) CL A-6(5) Sandy Clay 17 5 25.4 92.9 - - 82 34 12 - CL A-6(9) Sandy Clay 17 25 18.1 105.1 0 94 6 NV NP - SP-SM A-2-4(0) Sand with Silt 18 15 3.5 102.9 0 94 6 NV NP - SP-SM A-2-4(0) Sand with Silt 18 25 24.9 96.6 1 27 72 47 23 - CL A-7-6(16) Sandy Clay 19 2.5 4.7 122.2 - - 12 27 11 - SC A-2-6(0) Clayey Sand 19 10 1.4 107.7 - - 10 NV NP - SP-SM A-2-4(0) Sand with Silt 20 5 2.1 SID - - 2 NV NP - SP A-2-4(0) Sand 20 20 8.2 99.7 - - 5 NV NP - SP A-2-4(0) Sand 21 7.5 0.9 S/D 21 75 4 NV NP - SP A -1-a(0) Sand 21 15 1.4 106.8 16 74 10 NV NP - SP-SM A -1-b(0) Sand with Silt 22 7.5 1.0 SID 37 57 6 NV NP - SP-SM A -1-a(0) Sand with Silt 22 20 9.5 107.5 0 91 9 NV NP - SP-SM A-2-4(0) Sand with Silt Bulk 1-5 8.1* 129.5* - - 25 22 7 - SC-SM A-2-4(0) Clayey, Silty Sand * Indicates optimum moisture content and maximum standard Proctor density (ASTM D-698) Job No. 14-3559 GROUND ENGINEERING CONSULTANTS TABLE 2 SUMMARY OF SOIL CORROSION TEST RESULTS Sample Location Water Soluble Sulfates (%) pH Redox Potential (my) Sulfides Content Resistivity (ohm -cm) USCS Classifi- cation Soil or Bedrock Type Test Hole No. Depth (feet) 1 4 0.02 8.4 -84 Positive 1,509 SM Silty Sand 3 4 0.03 8.5 -87 Positive 1,155 SC Clayey Sand 5 20 0.01 8.7 -100 - SM Silty Sand Trace 9 6 0.02 8.8 -102 Positive 1,314 SP-SM Sand with Silt 12 6 0.03 8.6 -93 Positive 9,362 SP-SM Sand with Silt 16 2.5 0.15 8.5 -91 Positive 6,398 SC Clayey Sand 19 2.5 0.01 8.5 -87 Positive 7,297 SC Clayey Sand 20 5 0.01 8.5 -94 Positive 7,394 SP Sand Job No. 14-3559 Notice of Inquiry Weld County Pre -application Case # PRE20-0153 Date of Inquiry 9121/20 Municipality Firestone CPA Name of Person Inquiring Aileen Yeung 4' Property Owner Anadarko E&P Company Planner Diana Aungst Li r Planner Phone Number 970-400-3524 i Planner Email Address daungst@weldgov.com Legal Description Lot C of RE -3621 being the NW4 Section 15, T3N, R67VV Parcel Number 1209-1520-0036 Nearest Intersection CR 34 and CR 19 Type of Inquiry Storage yard and stockpiling r The above person met with County Planning staff about developing a parcel of land inside your designated Intergovernmental Agreement/Coordinated Planning Agreement Boundary. County Planner's signature I Would you like to pursue annexation of this property? NO YES Date of Contact A PE 2lit 2-O2O Comments: I' MNPJIJfr ffill" W22r20 Signature of Municipality .aepresentative Title Date Please sign and date to acknowledge that the applicant has contacted you and return this signed form to Weld County Department of Planning Services. Weld County Planning Department 15:55 N nth Ave, Greeley, CO H06. 1 (970) -1100-en 00 �- (97u) 304-6498 Fax Notice of Inquiry Weld County Pre -application Case # Date of Inquiry Municipality Name of Person Inquiring Property Owner Planner Planner Phone Number Planner Email Address Legal Description Parcel Number Nearest Intersection Type of Inquiry PRE20-0153 9/21/20 Mead CPA Aileen Yeung Anadarko E&P Company Diana Aungst 970-400-3524 daungst@weldgov.com Lot C of RE -3621 being the NW4 Section 15, T3N, R67W 1209-1520-0036 CR34and CR19 Storage yard and stockpiling The above person met with County Planning staff about developing a parcel of land inside your designated Intergovernmental Agreement/Coordinated Planning Agreement Boundary County Planner's signature Would you like to purse anneation of this property? NO X YES Date of Contact 4' Is 2f12O l � Comments: Signature of Mu epresentative Ti e PIJ'^nn'ry t4yt,kve _ ilasvre- 31.42 Date Please sign and date to acknowledge that the applicant has contacted you and return this signed form to Weld County Department of Planning Services. Weld County Planning Department 15.55 17th Aye, Greeley, CO 8O631 (970) 4OO-81OO -- (970) 3O4-6498 Fax Notice of Inquiry Weld County Pre -application Case # PR Egg-OO18 Date of I n+q u iry 1131120 Municipality ' Milliken CPA Name of Person Inquiring Aileen Veung Property Owner Anadarko E & P Company LP Planner J Diana Aungst Planner Phone Number 970-400-3524 Planner Email Address 1 daungstigweldgov.com Legal Description Lot C of RE -3621 being the NW4 Section 15, T3N, R6TW Parcel Number 120915200036 Nearest Intersection CR 34 and CR 19 Type of Inquiry Expand a compressor station and add stockpiling The above person met with County Planning staff about developing a parcel of land inside your designated Intergovernmental Agreement/Coordinated Planning Agreement Boundary. County Planner's signature Would you like to pursue annexation of this property? NO Date of Contact Comments: 11111111 - YES sr? 4-1,61;743/ Signat of Mu iclpality I epresen -live This Date Please sign and date to acknowledge that the applicant has contacted you and return this signed form to Weld County Department of Planning Services. Weld County Planning Department 1565 Nx ith Ave, Greeley, CO 80831 -s (970) 400e6100 se (970) 304-6498 Fax 20181107 Notice of Inquiry Weld County Pre --application Case # PRE =O 163 Date of Inquiry 9/21/20 Municipality Milliken CPA t lame of Person Inquiring I Aileen Veung Property Owner Anadarko E&P Company Planner Diana Aungst Planner Phone Number 9704004524 Planner Email Address daungst@weldgotcom Legal Description Lot C of RE -3621 being the NW4 Section 15, T3N, R6 Parcel Number 1209-1520-0036 Nearest Intersection CR 34 and CR 19 Type of Inquiry Storage yard and stockpiling The above person met with County Planning staff about developing a parcel of land inside your designated Intergovernmental AgreementiCoordinated Planning Agreement Boundary. County Planner's signature IME Please sign and dame to acknowledge that the applicant has contacted you and return this signed form to Weld County Department of Planning Services. Weld County Planning Department 1555 N 1lth Ave, Greeley, CO 80631 Pim.% (970) 400-6100 (970) 46498 Fax Notice of inquiry Weld County Pre -application Case # PRE20-0153 153 Date of inquiry 9/21/20 Municipality Platteville CPA Name of Person Inquiring Aileen Yeurig Property Owner Anadarko E& P Company Planner Diana Aungst Planner Phone Number 9 -- Planner Email Address aurtgst reldg+ay.cc m Legal Description Lot of E- 1 being the ection 1 , � N t Parcel Number 1209-1520-0036 Nearest Intersection CR 34 and CR 19 Type of Inquiry Storage yard and stockpiling _� �a - . , . , _., ...._..,,.,- - - - - --.- . The above person met with County Planning staff about developing a parcel of land inside your designated Intergovernmental Agreement/Coordinated Planning Agreement Boundary. County Planner's signature Would you like to pursue annexation of this property? NO _ YES Date of Contact sdira a.,,aal aare? 0 Comments: Signature of unicipality lity Representative ,_,/.1.0chrte,rtof osiveriff :pc sae< Title 7.-;p 2 Date Please sign and date to acknowledge that the applicant has contacted you and return this signed form to Weld County Department of Planning Services. Weld County Planning Department 1555 N 17th Aye, Greeley, CO80031 (97O) 400-6100 (97O) 3O4-6498 Fax Weld County Treasurer Statement of Taxes Due Account Number 82724104 Parcel 1209 [5200036 520003 6 Legal Description PT N W4 15-3-67 LOT C REC EXEMPT RE -3621 EXC UPR.R RE (4,01R) Account: R2724104 ANADARKO E & P COMPANY LP ATTN: TRAVIS HOLLAND-APC PROPERTY TAX PO BOX 173779 DENVER, CO 80217-3779 Year Tax Tax Charre 2020 Adjustments Interest Sims Address 9290 COUNTY ROAD 34 WELD C Fees Payments Balance $2,371.44 $0.00 $0.00 $0.00 $0.00 $2,371.44 Total Tax Charge $2}371.44 Grand Total Due as of 03/17/2021 $2,371.44 Tax Billed at 2020 Rates for Tax Area 3052 - 3052 Authority WELD COUNTY SCHOOL 01ST RE1 NORTHERN COLORADO WATER (NC CENTRAL COLORADO WATER (CCW CENTRAL COLD WATER WELL (CC PLATTEVILLE-GI LCRE$T FIRE AIMS JUN [OR COLLEGE HIGH PLAINS LIBRARY Taxes Billed 2020 * Credit Levy Mill Levy 15.0380000* 14.6920000 * 1,0000000 1.1560000 9.0000000 7,4820000 6.3050000 3.1810000 Amount $616.41 $602.22 $40.99 $47.38 $368.91 $306.69 $258.45 $130,39 57.8 540000 $2,371.44 Values REFININ r1PETROLEU M -LAND REFI N I NGIP'ETROLEU M -[M PS AG -DRY FARM LAND AG -WASTE LAND Total Actual $15,038 $116,834 $9,494 $0 $141,366 Asscsscd $4,360 $33,880 $2,750 $0 $40,990 Weld County Treasurer's Office 1400 N 17th Avenue PO Box 458 Greeley, CO 80632 Phone: 970-400-3290 Pursuant to the Weld County Subdivision Ordinance, the attached Statement of Taxes Due issued by the Weld County Treasurer, are evidence of the status as of this date of all property taxes, special assessments, and prior tax liens attached to this account. Current year's taxes are due but not delinquent. Date: a r7?202( Hello