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Home My WebLink About20182811.tiffPRELIMINARY DRAINAGE REPORT MAKENA GAS PLANT Located in the: E 1/2 & OF THE SE 14 OF SECTION 25, TOWNSHIP 8 NORTH, RANGE 62 WEST OF THE PRINCIPAL MERIDIAN, WELD COUNTY, CO Prepared: May 7, 2018 Prepared for: Outrigger DJ Operating LLC 1200 Seventeenth Street, Suite 900 Denver, CO 80202 Prepared By: Crestone Consultants, LLC 14145 West Warren Cir. Lakewood, CO 80228 303.997.61j3 Crestone Project No. 18009 CRESTONE CONSULTANTS, laic civil engineering solutions CERTIFICATION OF COMPLIANCE ENGINEERING DESIGNED TO WELD COUNTY CODE STANDARDS AND CRITERIA I Joseph M. Erjavec, P.E. , Consultant Engineer for Outrigger DJ Operating, LLC ("Applicant"), understand and acknowledge that Applicant is seeking land use approval of LI SR18- ("Application") for the property described in the attached Exhibit "A." I have designed or reviewed the design ("Design") for the proposed land use set forth in the Application. I hereby certify, on behalf of Applicant that the Design will meet all applicable drainage requirements of the Weld County Code with the exception of variance(s) described below. This certification is not a guarantee or warranty either expressed or implied. (Engineer's Stamp) Engineer of Record Signature VARIANCE REQUEST 1) Describe the Weld County Code criteria of which a variance is being requested. 2) Describe why it is not possible to meet the Weld County Code. 3) Describe the proposed alternative with engineering rational which supports the intent of the Weld County Code. I understand and agree that the intention of the Code is to reduce impacts of development on neighboring downstream properties and the public. I understand if this variance request is approved it is not precedent setting and is based on site specific constraints. Planning Director Approval indicated when signed by director or appointee. Planning Director Name Signature Date of approval 1/13/15 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 ENGINEER'S CERTIFICATION I hereby certify that this report for the preliminary drainage design of the Makena Gas Plant was prepared by me (or under my direct supervision) in accordance with the provisions of the Weld County storm drainage criteria for the owners thereof. yrii JosepK M. Erthics4P.E Registered Professional Engineer State of Colorado No. 31224 Crestone Project No. 18009 Page I i MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 TABLE OF CONTENTS I - INTR[CTII...4. 0444404004004444444444 4 44040440404004004444444444 4 4 Page . 4 4 4 1. 4 4 4 4 ... 4 4 4 .. 4 4 4. 44 4444440444440444****4 4 4 ... 1 II - GENERAL LOCATION & DESCRIPTION 1 Location 4+ 000444044 if 00 000 4444444444 t 4 4 444 .+4444'44'444444+44 WOW 444444 44 44 *4.0 0 4 4 4 4 4 444 4•4 4 4 4 4 4 4 Description of Property •••....•....•.... 4444444 •••••• 44444 •••••••• 4fff f4f.f.f/i ff.ff'ff tfffff/6444let 64.4.44.44+4+4444444+4+.4. III — DRAINAGE BASINS AND SUB —BASINS man 4....f .s 1 MajorBasin Description ail 44t.Ot6+tt 4.4 tti 4.644• 4.4 t tt 4.4 t*t 4.4.444•+t+444t.t4•4*4* 4.4444444 t Of t 4.4th 4.4 et* 4.4+•+fief. - 2 Historic Sub -Basin Description f 4t...444....tt... ile OOOOO ell 09 6++66.4 f4 4+66.4 et 4 2 Developed Basin Descriptions+64444..4444ft4.....444...44444 t 3 IV - DRAINAGE DESIGN CRITERIA 3 Development Criteria Reference and Constraints ft4..+44.4flee eel ......f.f... 414..4 iti.nog ....i ti... 4 t4 se Hydrological Criteria II 4 Hydraulic Criteria.... 4...t 4.... 4.4..OM/ t........ t 6+466..+44.././4 t 4 .44 t 5 Y -DRAINAGE FACILITY DESIGN . 4 4 R I R .... 4 .. U I i i i 4 4 f. 4 ........... 4 ... i i i. ... i .......... 4 .. .. I I U f 4 4.................................. 7 General Concep 444.4+646444.4.' ___ 4+444. 4. 4464. 44f 4f444+4444.4+4+6464.4.4.4.444f64Of4.4.4.f0f44444. 4.+.44444044444_-_- t 4.4 ft 44444444.4 # Specific Details t6.f.4...tflee t4/t.t.......................tt....t.t 8 VII - CONCLUSIONS............. .. 10 - - - - ••••••••••• - - - _ - 4444444•9•4444044 4 4 i 44 4 4 ! 66440404 - - - - - VIII REFERENCES id Crestone Project No. 18009 Page I ii MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 LIST OF APPENDICES APPENDIX A— General Information Vicinity Map NRCS Soils Data FERIA Flood Insurance Rate Map APPENDIX B— Hydrologic Calculations (Historic & Developed Condition) Rational Method Calculations Hydrologic Calculation Reference Materials APPENDIX C — Hydraulic Calculations (Historic & Developed Condition) Channel Sizing Calculations Detention Pond Sizing Calculations Hydraulic Calculation Reference Materials APPENDIX D — Maps Historic Drainage Exhibit Developed Drainage Exhibit Drainage Details Crestone Project No. 18009 Page I iii MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 I - INTRODUCTION This Preliminary Drainage Report has been prepared for the Makena Gas Plant and will outline the methodology for sizing of stormwater conveyances and attenuation facilities associated with the proposed Project Site. The owner of the facility, Outrigger DJ Operating LLC is proposing to construct a Gas Plant which includes various equipment, buildings and access roads. The proposed facility will also include a Detention Pond for stormwater attenuation & water quality enhancement. II - GENERAL LOCATION & DESCRIPTION Location A) The USR Parcel is located in the East Half of the Southeast Quarter of Section 25, Township 8 North, Range 62 West of the 6th Principal Meridian, approximately 3.5 miles east of Briggsdale, Colorado, approximately 27.5 miles northeast of the Town of Greeley, Colorado. The Project Site is located in the north half (+/-) of the USR Parcel within the East Half of the Southeast Quarter of Section 25. See Appendix A for a Vicinity Map. B) The site is located approximately /2 mile south of Hwy 14 along the west side of Weld County Road 85. C) No major drainageways n ageways exist within the USR Parcel. The site is located within the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (Map #08123C1025E, Effective January 20, 2016) which is "Not Printed". Description of Property A) The area associated with the USR Parcel is approximately 80.0 acres. The developed area is approximately 23.6 acres. For the purposes of this report, "Project Site" refers to the 23.6 acres of developed area associated with the Makena Gas Plant. B) The entire USR Parcel is undeveloped and consists of undeveloped pasture. As per the National Resources Conservation Service (NRCS), the predominant soils within the study area (portion of USR Parcel located in the north half (+/-) East Half of the Southeast Quarter of Section 25) are described as follows: 44— Olney fine sandy loam, 0 to 6 percent slopes Parent material: Calcareous loamy alluvium , slope ranging from 0 to 6%, have a moderately high to high water capacity, are well drained, have a depth to water table greater than 80 inches, are moderately susceptible to erosion from water, and have a moderate susceptibility to wind erosion. The NRCS Hydrologic Soil Group for this type of soil has been classified as Group B (moderate infiltration rate; moderate runoff potential). Crestone sto ne Project No. 18009 Page I 1 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 54- Platner loam, 0 to 3 percent slopes Parent material: Mixed eolian n deposits over tertiary aged alluvium derived from igneous, metamorphic and sedimentary rock, slope ranging from 0 to 3%, have a moderately low to moderately high water capacity, are well drained, have a depth to water table greater than 80 inches, are moderately susceptible to erosion from water, and have a moderate to high susceptibility to wind erosion. The NRCS Hydrologic Soil Group for this type of soil has been classified as Group C (slow infiltration rate; moderate runoff potential). 55- Renohill fine sandy loam, 0 to 6 percent slopes Parent material: Calcareous, clayey loamy residuum weathered from shale, slope ranging from 0 to 6%, have a moderately low to moderately high water capacity, are well drained, have a depth to water table greater than 80 inches, are moderately susceptible to erosion from water, and have a moderate to high susceptibility to wind erosion. The NRCS Hydrologic Soil Group for this type of soil has been classified as Group D (very slow infiltration rate; high runoff potential). Please refer to Appendix A for NRCS soils data. C) The Project Site does not include a major drainageway and is not located within a regulated floodplain. D) The project involves construction of a Gas Plant which includes various equipment, buildings and access roads. The proposed facility will also include a Detention Pond for stormwater attenuation & water quality enhancement. E) The Project Site does not include irrigation facilities. III - DRAINAGE BASINS AND SUB -BASINS Major Basin Description The Project Site is within the South Platte River watershed (via Crow Creek) and does not contain a major drainageway. The site is located within the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (Map #08123C1025E, Effective January 20, 2016) which is "Not Printed". Historic Sub -Basin Description A) The Project Site includes 1 historic sub -basin which is described as follows: Basin Hi (23.60 ac/2% Imp) Basin Hi encompasses the majority of the Project Site and includes the Gas Plant. The basin generally slopes from northeast to southwest with slopes ranging from approximately 0.5% to 3.0%. Please refer to Appendix D for a copy of the Historic Drainage Exhibit. Crestone Project No. 18009 Page 12 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 B) Runoff from the Project Site and the overall USR Parcel generally sheet flows south/southwesterly into the adjacent parcel on the west side of the USR parcel. A small portion of the project site within the northeast corner of the USR parcel sheet flows easterly, towards Weld County Road 85. Additionally, a ridgeline exists near the north boundary of the USR parcel. This ridgeline limits the amount of offsite runoff flowing into the USR Parcel as the runoff generated on the north side of the ridgeline sheet flows north, into the adjacent parcel on the north side of the USR Parcel. Developed Basin Descriptions In the developed condition, the Project Site has been delineated into 3 basins (Basins D1 -D3). The developed basins are described as follows: Basin Dl (10.44 ac/40.0% Imp) Basin D1 is comprised of the west half of the Gas Plant. Runoff generated within this basin sheet flows southwesterly into a proposed drainage channel (CH1) along the west side of the plant which directs the runoff into the proposed detention pond at Design Point 1. A small portion of the basin will sheet flow directly into the proposed detention pond. Basin D2 (10.90 ac/40.3% Imp) Basin D2 is comprised of the east half of the Gas Plant. Runoff generated within this basin sheet flows southeasterly into a proposed drainage channel (CH2) along the east side of the plant which directs runoff into the proposed detention pond at Design Point 2. A small portion of the basin wi l l sheet flow directly into the proposed detention pond. Basin D3 (2.25 ac/100.0% Imp) Basin D3 is located south of the Gas Plant and is comprised of the proposed detention pond. Runoff generated by this basin is directed westerly (within the pond bottom) to the detention pond outlet structure located at Design Point 3. Please refer to Appendix D for a copy of the Developed Drainage Exhibit. IV - DRAINAGE DESIGN CRITERIA The regulations, guidelines, and drainage design criteria used in the preparation of this report are those contained within the Weld County, W Charter and County Code, Article XII - Storm Drainage Criteria and the Urban Drainage and Flood Control District (UDFCD), Urban Storm Drainage Criteria Manual - Volumes 1, 2, and 3. Development Criteria Reference and Constraints A) The Project Site is not included in any known previous drainage studies. B) The siting of the proposed facility within the USR parcel was influenced by the location of an existing buried oil & gas pipeline which runs north/south along the west side of Weld County Road 85 (approximately 75' west of the existing traveled way). To limit the earthrnoving Crestone Project No. 18009 Page 13 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 operations, the Gas Plant is generally located within the area of the USR Parcel that has the mildest existing slopes. Hydrological Criteria A) The 1 hour rainfall depths listed below were obtained from the National Oceanic and Atmospheric Administration (NOAA) Precipitation Frequency Data Server and were utilized in determining the historic and developed hydrologic calculations, as well as in calculating the required pond volume (Modified FAA Method) for the proposed Detention Pond. 2 YR 5 YR 10 YR 100 YR 0.92 1.19 1.45 2.57 The design storms analyzed in this report are as follows: Minor Storm —10 year, 1 hour storm occurrence (utilized for determining the historic release from the Project Site which was used in the Modified FAA Method Detention Pond sizing calculation) Please Note — based on coordination with Weld County, the USR Parcel and Project Site are located in a NON -URBANIZING AREA. Major Storm —100 year, 1 hour storm occurrence (open channel, culvert & riprap sizing calculations) B) The Rational Method was used to determine the historic & developed flow rates for the 2, 5, 10 & 100 year storms. The Rational Method formula is described as follows: Rational Formula = CIA C = maximum rate of runoff (cubic feet per second = cfs) C = runoff coefficient I = average intensity of rainfall (inches/hour) for a duration equal to the time of concentration, Tc Where the average intensity ("I") is calculated as follows: I = (28.5*P1)/(10+Tc)a.]&r' (Reference 2) I = rainfall Intensity, inches per hour P1=1 hour point rainfall depth, inches Tc = time of concentration, minutes A = area (acres) Crestone sto ne Project No. 18009 Page 14 MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 C) The following table summarizes the historic and developed Rational Method flowrates for the Project Site: Basin Area (ac) QS (cfs) Q10 (cfs) 0100 (cfs) Historic Hi 23.60 1.5 5.2 31.1 Basin Area (ac) (cfs) QS Q1p (cfs) Q100 (cfs) Developed D1 10.44 7.4 10.6 28.3 D2 10.90 7.7 11.1 29.6 D3 2.25 5.5 6.8 12.3 Sum DI -D3 23.60 18.8 26.2 66.3 A) UDFCD equations were utilized to determine required Water Quality Capture Volume (WQCV) for the Project Site. A diversion berm/swale(s) is proposed along the north and west sides of the Project Site to keep offsite runoff from entering the Project Site. The diversion berm/swale(s) will direct runoff to the west and south where it will combine with other historic flows which will not be attenuated in the proposed Detention Pond. Refer to Appendix B for Hydrologic Calculations and Reference Materials. Hyd r~a ulic Criteria A) Autodesk Hydraflow Express Extensions was used to determine channel sizes necessary to convey the applicable developed design flow. Hydraflow employs the Manning's Equation in open channel calculations, which, for the purposes of design, the flow is assumed to be steady and uniform (allowing the use of Manning's Equations). The Manning's Equation can be stated as follows: Manning's Equation 1.49AR213 Sen it n = Manning's roughness coefficient A = flow area (ft2) R = hydraulic radius Sf = friction slope (Le. slope of the pipe, ft/ft) Crestone Project No. 18009 Pagel MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 The design parameters for the channels are as follows: Maximum Velocity = 5.0 feet per second (grass lined) Maximum Velocity =16.0 feet per second (riprap lined) Ivlanning's roughness coefficient (n) = 0.045 B) The proposed Detention Pond has been sized based on the entire area that is tributary to the pond, which includes the Project Site. The Modified FAA Method was utilized to size the Detention Pond, which has been sized for the 100 year, 1 hour storm with a 10 year, 1 hour storm (NON -URBANIZING AREA) historic release rate. WQCV will be provided as part of the required 100 year detention volume. The following table sum marizes the Detention Pond sizing: Basin Area ac Req'd Volume (ac-ft) WQCV R&M 100 Year via Modified Detention Volume FAA Method ac- D1 -D3 23.60 0.46 3039 1. The runoff volume stored in the proposed Detention Pond will be released at or below historic discharge rates (which are defined as the 10 year/ 1 hour storm, since the Project Site is located within a NON -URBANIZING AREA). The Detention Pond outlet structure will control the release from the pond. The outlet structure consists of a modified CDOT Type C inlet which includes a 2 -stage release and a trash rack. The initial release includes a WO Plate which has been sized to release the WQCV over a 40 hour duration. The WO Plate includes 1 column of 4 rows of 4.75"x1.00" openings. The second release includes a Restrictor Plate which covers the outlet structure's 12" RCP outfall pipe. This release reduces the 100 year release from the pond to the historic (10 year, 1 hour) release rate. 2. A 12" RCP outfall pipe will convey the pond release from the outlet structure to existing ground west of the Detention Pond. 3. An emergency overflow has been designed as part of the Detention Pond. The emergency overflow has been sized to convey the 100 year developed in -flow rate into the pond (66.3 cfs) at a total depth of 0.5 ft. The emergency overflow crest length is 60 ft and includes a concrete cutoff wall and buried riprap on the downstream side of the spillway. 4. The pond includes 1 ft of freeboard above the emergency overflow crest. 5. The Detention Pond will be located within the fenced area to protect animals and humans from accessing the pond area. Crestone Project No. 18009 Page 16 MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 A summary of the Detention Pond includes: Pond Invert: 5007.42 Top of Pond (Berm): 5013.00 WQCV W.S. Elev: 5009.24 Provided 100 Year Pond Volume at 100 Yr WS Elev: 4.22 ac -ft (required volume = 3.39 ac -ft) 100 Yr WS Elev.: 5012.00 Emergency OverflowCrest Elev: 5012.00 Provided Freeboard: 1.0 ft C) Permanent erosion control features consist of the proposed Detention Pond, riprap erosion protection throughout the various onsite channels and where concentrated flows will enter and exit the proposed Detention Pond. Refer to Appendix C for all Hydraulic Calculations (which include channel sizing, riprap sizing and detention pond sizing) and Reference Materials. V - DRAINAGE FACILITY DESIGN General Concept A) The storm drainage conveyance and storage elements have been designed to safely collect and convey developed condition runoff generated by a 100 year storm event within the Project Site. The runoff from the Project Site will be attenuated in a proposed Detention Pond and release from the pond will be controlled via a 2 -stage outlet structure. The outlet structure has been designed to release the WQCV over a 40 hour period and the 100 year storm event will be released at the historic (10 year, 1 hour) release rate. Regarding offsite releases, since the Project Site will be routed through the Detention Pond and released at historic rates, offsite releases will be less than or equal to historic 10 year, 1 hour storm release rate. The water released from the Detention Pond will be conveyed overland west/southwesterly to match existing flow patterns of the Project Site and USR Parcel. C) Multiple tables, figures and drawings have been included within the appendices of this report and include the following: APPENDIX A - General Information Vicinity Map NRCS Soils Data APPENDIX B - Hydrologic Calculations (Historic & Developed Condition) Rational Method Calculations Hydrologic Calculation Reference Materials Crestone Project No. 18009 Page 17 MAKENA► GAS PLANT: Preliminary Drainage Report May 7, 2018 APPENDIX C -� Hydraulic Calculations (Historic & Developed Condition) Channel Sizing Calculations Detention Pond Sizing Calculations Hydraulic Calculation Reference Materials APPENDIX D — Maps Historic Drainage Exhibit Developed Drainage Exhibit Drainage Details D) In addition to the Detention Pond and its associated features, hydraulic structures associated with the proposed Makena Gas Plant are limited to drainage channels, swales and a concrete drainage pan. Channels (CH) have a bottom width of 5 feet, 4:1 side slopes and a minimum depth of 2 ft. Proposed channels are located within Basins D1 & D2. Swales will be comprised of a AP section with 3:1 maximum side slopes and a minimum depth of 0.5'. Swales will be provided to direct runoff away from buildings and plant equipment. Culverts (beyond the Detention Pond outlet) are not proposed. The Detention Pond outlet is discussed in previous sections. Specific Details A) The proposed Detention Pond includes a maintenance access on the north side of the pond which provides access to the bottom of the pond. Additionally, the pond's outlet pipe includes a 2 -stage outlet structure on the upstream end (within the pond) and a cut-off wall and riprap erosion protection on the discharge end. The pond's emergency overflow will include a cut-off wall as well as buried riprap to help protect the berm in the event of a pond overflow. ) Maintenance Plan All stormwater facilities designed herein are privately owned &. maintained. The property owner will be responsible for regular maintenance and repairs of the drainage facilities which include drainage channels, culverts and the Detention Pond and its associated features. Drainage channels, culverts and pond shall be inspected routinely on at least a quarterly basis and after significant storm events. Routine maintenance activities for the channels, culverts and pond (including pond outlet structure, emergency overflow and maintenance access) include mowing/weed control, trash & debris removal, erosion mitigation through replanting/watering, overgrown vegetation removal and structural repair. Crestone Project No. 18009 Page 18 MAKENA GAS PLANT: Preliminary Drainage Report ay 7, 2018 The following table provides routine maintenance guidelines: Summary of Routine Maintenance Activities Maintenance Activity Minimum Frequency Look for: Maintenance Action Trash/Debris Removal Monthly Trash channel & debris and in pond Remove trash and and debris dispose of Mowing Twice annually native species for Excessive height/aesthetics grass Mow height native of grass to a 6" Inflow Outlet Point/Trash Works Cleaning Rack/ As needed; significant events; maintenance w/ storm other after Clogged channel release; water inflow culverts, ponding points, pond Remove debris/trash/sediment allow and proper dispose function of to Weed Control As needed, upon inspections based Noxious Unwanted weeds; vegetation Treat pull; weed w/ Consult inspector herbicide the local or hand Vegetation Tree Thinning Removal/ As needed, upon inspections based Trees vegetation channel bottom, pond emergency and release, features/ inflow plant around overflow points, Remove tree trimming Consult concerning species; surface vegetation with restore arborist evasive tools; grade with and Rodent Damage As needed, upon inspections based Holes, dirt, small raised piles burrows of Evaluate animal DOW for damage; control guidance consult specialist or Mosquito Treatment As needed Standing water/mosquito habitat Treat chemicals w/ EPA approved Based on the routine inspections, provide periodic minor and major maintenance activities for the channels, culverts and pond (including pond outlet structure, emergency overflow and maintenance access) include sediment removal from the channels, riprap pads, pond bottom, pond outlet structure; erosion repair; overgrown vegetation removal; structural repair/replacement. The following table provides minor maintenance guidelines: Summary of Minor Maintenance Activities Maintenance Activity Frequency Minimum Look for: Maintenance Action Sediment Removal As needed, based upon inspections Sediment build-up Remove sediment and dispose of Erosion Repair As needed, based inspections upon Rills/gullies channel side slopes, bottom, forming pond in on Repair Re of eroded -vegetate; erosion address areas source Vegetation As needed, Large trees/wood Remove vegetation with tree Crestone Project No. 18009 Page 19 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 Maintenance Activity Frequency Minimum Look for: Maintenance Action Removal/Tree Thinning inspections based upon vegetation channel channel features bottom around and trimming arborist species; surface tools; concerning restore Consult grade evasive with and Drain Cleaning/ Jet Vac As needed, based inspections upon Sediment inflow culverts, dissipaters. points, energy build-up channel at Clean dissipaters, basins; culverts, Jet and Vac if drains, stilling needed energy Re -vegetation inspections As needed, based upon Bare areas Repair or sodding by localized seeding The following table provides major maintenance guidelines: Summary of Major Maintenance Activities Maintenance Activity Minimum Frequency Look for: Maintenance Action Major Sediment Removal As needed, upon inspections based Large sediment; conveyance quantities reduced capacity of Remove dispose vegetation and of sediment. as lawfully needed Repair Major Repair Erosion As needed, upon inspections based Severe gullies, displacement, holes erosion including excessive soil, settlement, Repair and problem avoid stabilize future erosion, —find and address erosion re -vegetate cause to of Structural Repair As needed, upon inspections based Deterioration damage components concrete, to damaged structural and/or — broken pipes Structural the design structure repair to restore to its original VII - CONCLUSIONS A) Compliance with Weld County Code This Preliminary Drainage Report has been prepared in accordance with Weld County Code. The Detention Pond proposed with this report has been sized in accordance Weld County detention requirements. B) Drainage Concept 1. Developed runoff generated from the Project Site is collected and conveyed southerly via sheet flow and channels into the proposed Detention Pond. All developed areas of the Project Site will be routed through the Detention Pond and released via the 2 -stage outlet structure at attenuated release rates (40 hour duration for WQCV release and historic 10 year, 1 hour release for 100 year event). Since releases form the Project Site will be less than or equal to historic 10 year, 1 hour release rate, downstream improvements should not be adversely impacted by the proposed Makena Gas Plant. Crestone sto n e Project No. 18009 Page 110 MAKENA GAS PLANT: Preliminary Drainage Report May 7, 2018 2. The Project Site is not included within a Master Drainage Plan and therefore, not impacted by previous plan requirements/recommendations. 3. The Project Site is not encumbered by irrigation facilities. 4. Please refer to Appendices A through D for specific technical criteria and references. VIII - REFERENCES 1. Weld County, CO Charter and County Code, Article XII — Storm Drainage Criteria. 2. Weld County Engineering & Construction Guidelines, Updated July 2017. 3. Denver Urban Drainage and Flood Control District (UDFCD), Drainage Criteria Manual, Volume 1, revised March 2017, Volume 2, revised September 2017, Volume 3, revised April 2018. 4. Natural Resources Conservation Service (MRCS), Web Soil Survey Weld County Colorado, Northern Part, Version 12, October 10, 2017. Crestone Project No. 18009 Page 111 APPENDIX A General Information Vicinity Map NRCS Soils Data FEMA — FIRM Map VICINITY MAP hil ttap Pip 3: t3 rt a a £CR86 7,500' r a e 0 WCR U HWY 14 MAKENA GAS PLANT PROJECT SITE tin as U WCR 94 WCRmi92 Cr O 14. _Ire a 1NCR-82 1 c U 15,000' 1" 7,500' 1 4 _ CRESTONE CONSULTANTS, civil engineering solutions 14145 West Warren Cirche 30,3-997-6113 - t ww_creStnneUUc.coan Lakewood, CO 80228 CAUT10N. THE ENGINEER PREPARING THESE PLANS AND CRESTONE CONSULTANTS, LLC. WILL NOT BE RESPONSIBLE FOR OR LIABLE FOR UNAUTHORIZED CHANGES TO OR USES OF THESE FLANS. ALL CHANGES TO THE PLANS MUST BE IN WRITING AND MUST BE APPROVED BY THE PREPARER OF THESE LADS. PROJECT: MAKENA GAS PLANT TITLE: VICINITY MAP DATE: 04/2018 DRAWN BY: LJM 400 37 59" N 400 37 76" N 8 104° 15' 57" W 562100 932 �r�I 100 LP1 A 562200 562300 Soil Map —Weld County, Colorado, Northern Part (Makena Gas Plant) 562400 ay riot be valid at the le sk_ 53a)00 �y,�+�77 562300 562 400 Map Scale: 1:5,030 if printed on A portrait (8.511 x 11") sheet. Meters 0 so lop 200 300 502600 562 600 Feet 0 200 400 800 1200 Map p -lion : Web Mercator Corner coordinates: WGSS4 Edge tics: UTM Zone 13N WGSS4 567700 5600 � = rams w �+} II�y 562700 562800 104° 13' 23" 104° 15'23"W 400 37 59" N 40O 37' 26" N USDA Natural Resources Web Soil Survey Ia. Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1of3 Soil Map Weld County, Colorado, Northern Part (Makena Gas Plant) MAP LEGEND Area of Interest (A01) Area of Interest (AOl) Soils likkail Soil Map Unit Polygons Soil Map Unit Lines 0 Soil Map Unit Points Special Point Features X Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sod is Spot a Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation 4-44 Rails pwftail Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography MAP INFORMATION The soil surveys that comprise your AOl were mapped at 1:24,000. 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 -MRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Northern Part Survey Area Data: Version 12, Oct 10, 2017 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 1, 2016 Sep 22, 2016 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 Conservation Service Web Soil Survey National Cooperative Soil Survey 4/5/2018 Page 2of3 Soil Map —Weld County, Colorado, Northern Part Makena Gas Plant Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 44 Olney fine sandy percent slopes loam, 0 to 6 0.2 0.2% 54 Platner slopes loam, 0 to 3 percent 20.1 20.6% 55 Renohill 6 fine sandy percent slopes loam, 0 to 77.1 79.1% Totals for Area of Interest 97.5 100.0% USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 3 of 3 Map Unit Description: Olney fine sandy loam, 0 to 6 percent slopes --Weld County, Colorado, Makena Gas Plant Northern Part Weld County, Colorado, Northern Part 44 —Olney fine sandy loam, 0 to 6 percent slopes Map Unit Setting National map unit symbol: 35zy Elevation: 3,500 to 5,800 feet Mean annual precipitation: 11 to 15 inches Mean annual air temperature: 46 to 54 degrees F Frost -free period: 125 to 175 days Farmland classification: Farmland of statewide importance Map Unit Composition Olney and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit Description of Olney Setting Landform: Plains Down -slope shape: Linear Across -slope shape: Linear Parent material: Calcareous loamy alluvium Typical profile H? - 0 to 6 inches: fine sandy loam H2 - 6 to 18 inches: sandy clay loam H3 - 18 to 60 inches: sandy loam H4 - 60 to 64 inches: sandy loam Properties and qualities Slope: 0 to 6 percent Depth to restrictive feature: More than 80 inches Natural drainage class: well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Moderate (about 8.1 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4c Hydrologic Soil Group: B Ecological site: Loamy Plains (8067 BY002CO) USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1 of 2 Map Unit Description: Olney fine sandy loam, 0 to 6 percent slopes --Weld County, Colorado, Makena Gas Plant Northern Part Hydric soil rating: No Minor Components Stoneham Percent of map unit: 9 percent Hydric soil rating: No Ascalon Percent of map unit: 6 percent Hydric soil rating: No Data Source Information Soil Survey Area: Weld County, Colorado, Northern Part Survey Area Data: Version 12, Oct 10, 2017 USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 2 of 2 Map Unit Description: Platner loam, 0 to 3 percent slopes ---Weld County, Colorado, Northern Makena Gas Plant Part Weld County, Colorado, Northern Part 54—Platner loam, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 2tl n 0 Elevation: 4,000 to 4,930 feet Mean annual precipitation: 14 to 17 inches Mean annual air temperature: 46 to 50 degrees F Frost -free period: 135 to 160 days Farmland classification: Prime farmland if irrigated Map Unit Composition Platner and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit Description of Platner Setting Landform: In terflu ryes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down -slope shape: Linear Across -slope shape: Linear Parent material: Mixed eolian deposits over tertiary aged alluvium derived from igneous, metamorphic and sedimentary rock Typical profile Ap - 0 to 6 inches: loam Bt 1 - 6 to 11 inches: clay Bt2 - 11 to 20 inches: clay Bk1 - 20 to 27 inches: loam Bk2 - 27 to 37 inches: sandy clay loam C - 37 to 80 inches: sandy clay loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): : Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline (0.0 to 1.0 mmhoslcm) Available water storage in profile: Moderate (about 8.1 inches) USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1 of 2 Map Unit Description: Platner loam, 0 to 3 percent slopes ---Weld County, Colorado, Northern Makena Gas Plant Part Interpretive groups Land capability classification (irrigated): 3s Land capability classification (nonirrigated): 4s Hydrologic Soil Group: C Ecological site: Loamy Plains (R067BY002CO) Hydric soil rating: No Minor Components Ascalon Percent of map unit: 10 percent Landform: In terflu ve s Landform position (two-dimensional): Summit, shoulder Landform position (three-dimensional): Interfluve Down -slope shape: Linear Across -slope shape: Linear Ecological site: Loamy Plains (8067 BY002CO) Hydric soil rating: No Raga, rarely flooded Percent of map unit 4 percent Landform: Drainageways Landform position (two-dimensional): Toeslope Landform position (three-dimensional): Base slope, head slope Down -slope shape: Linear Across -slope shape: Concave Ecological site: Overflow (R067BYO36CO) Hydric soil rating: No Rago, ponded Percent of map unit: 1 percent Landform: Playas Landform position (two-dimensional): Summit Landform position (three-dimensional): I nterfluve Down -slope shape: Concave Across -slope shape: Concave Ecological site: Closed Upland Depression (R007BY010CO) Hydric soil rating: No Data Source Information Soil Survey Area: Weld County, Colorado, Northern Part Survey Area Data: Version 12, Oct 10, 2017 USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 2 of 2 Map Unit Description: Renohill fine sandy loam, 0 to 6 percent slopes ---Weld County, Makena Gas Plant Colorado, Northern Part Weld County, Colorado, Northern Part 55—Renohill fine sandy loam, 0 to 6 percent slopes Map Unit Setting National map unit symbol: 360b Elevation: 3,600 to 6,200 feet Mean annual precipitation: 11 to 16 inches Mean annual air temperature: 46 to 48 degrees F Frost -free period: 100 to 160 days Farmland classification: Not prime farmland Map Unit Composition Renohill and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit Description of Renohill Setting Landform: Plains Down -slope shape: Linear Across -slope shape: Linear Parent material: Calcareous, clayey loamy residuum weathered from shale Typical profile H1 - 0 to 5 inches: fine sandy loam H2 - 5 to 18 inches: clay H3 - 18 to 32 inches: clay loam H4 - 32 to 36 inches: unweathered bedrock Properties and qualities Slope: 0 to 6 percent Depth to restrictive feature: 20 to 40 inches to paralithic bedrock Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately low to moderately high (0.06 to 0.20 inlh r) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhoslcm ) Available water storage in profile: Low (about 5.4 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: D USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1 of 2 Map Unit Description: Renohill fine sandy loam, 0 to 6 percent slopes ---Weld County, Makena Gas Plant Colorado, Northern Part Ecological site: Loamy Plains (R067BY002CO) Hydric soil rating: No Minor Components Shingle Percent of map unit: 5 percent Hydric soil rating: No Midway Percent of map unit: 4 percent Hydric soil rating: No Ulm Percent of map unit: 3 percent Hydric soil rating: No Other soils Percent of map unit: 3 percent Hydric soil rating: No Data Source Information Soil Survey Area: Weld County, Colorado, Northern Part Survey Area Data: Version 12, Oct 10, 2017 USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 2 of 2 40° 37 59" N 40° 37 26" N 8 104° 15' 57" W 562100 582104 LP1 A 582200 Hydrologic Soil Group —Weld County, Colorado, Northern Part (Makena Gas Plant) 5100 562400 ay not be valid at thi ale. %MO 562300 56240D 562500 Map Scale: 1:5,030 if printed on A portrait (8.5" x 11") sheet. Meters 0 50 lop 200 300 562 600 Feet 0 200 400 800 1200 Map projection: Web Mercator Corner coordinates: WGSS4 Edge tics: UTM Zone 13N WGSS4 562700 500 �+} I �r7I 562700 562800 104° 13' 23" 104° 15'23"W 40° 3759"N 40° 37' 26" N USDA Natural Resources Web Soil Survey Ia. Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1 of 4 ea 0 L C z 0 Umem C co M 2 Co 2 s z 0 2 Ce O ILL 0 4 2 MAP LEGEND were mapped at C 0 ita tf) _c1 Li 0 0 13 co 03 45 T3 C ts 70 U 4 6 2 ca rei w 0? C 0 co Chi 0 -E5E 413 0 C m 0 a).3 (46 tip 003 g C { �- ED c > 4) c '45 glint 1130 It MUCU - a r _c C~ to CO FS 0 EM ith C t sg k.-cp sag ea" i` t1) al w E sc 3 fi • C a) Z a ® ■ Area of Interest (ACM) Area of Interest (ACSl) U) Soil Rating Polygons • Water Features Streams and Canals Transportation m' cb (0 ea Q - czi co a3 co -o C/) sr 0 0 03L nE?} = 'r_ CL u) E 0'5 w u.. 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L to in Q (13 {6 0 ne to . 173 a o C L `C t m • • (13 Mar 1, 2016 —Sep images were photographed: to lines were n which the soi I C C 3 C tU r n Q } c C tv A �— i13 CD E 03 U9 t E •.C Sno a) ict 0 co -0 -C "C C O6 ▪ as C� C C C :5 cu O - ccJ � r 03 < • -� - C 0 0 c C I CNl i- 0 .t cn al C C _ J _ £ 0 O 7 L 4 an ] 0 0 O 7 • Ratin .a t0 Rating Points OEM a 40 <C a oe] [] co 'Tr y... c7") CI C`ri cp at D) CO a - a) r� V ) ny 'a co 0 L OD a ecl C z Natural Resources Conservation Service DL Hydrologic Soil Group —Weld County, Colorado, Northern Part Makena Gas Plant Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 44 Olney fine 0 to 6 sandy loam, percent slopes B 0.2 0.2% 54 Platner loam, percent slopes 0 to 3 C 20.1 20.6% 55 Renohill loam, slopes fine sandy 0 to 6 percent D 77.1 79.1% Totals for Area of Interest 97.5 100.0% 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 a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 3 of 4 Hydrologic Soil Group —Weld County, Colorado, Northern Part Makena Gas Plant 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 4/5/2018 Page 4 of 4 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Physical Soil Properties This table shows estimates of some physical characteristics and features that affect soil behavior. These estimates are given for the layers of each soil in the survey area. The estimates are based on field observations and on test data for these and similar soils. Depth to the upper and lower boundaries of each layer is indicated. Particle size is the effective diameter of a soil particle as measured by sedimentation, sieving, or micrometric methods. Particle sizes are expressed as classes with specific effective diameter class limits. The broad classes are sand, silt, and clay, ranging from the larger to the smaller. Sand as a soil separate consists of mineral soil particles that are 0.05 millimeter to 2 millimeters in diameter. In this table, the estimated sand content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. Silt as a soil separate consists of mineral soil particles that are 0.002 to 0.05 millimeter in diameter. In this table, the estimated silt content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. Clay as a soil separate consists of mineral soil particles that are less than 0.002 millimeter in diameter. In this table, the estimated clay content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. The content of sand, silt, and clay affects the physical behavior of a soil. Particle size is important for engineering and agronomic interpretations, for determination of soil hydrologic qualities, and for soil classification. The amount and kind of clay affect the fertility and physical condition of the soil and the ability of the soil to adsorb cations and to retain moisture. They influence shrink -swell potential, saturated hydraulic conductivity (Ksat), plasticity, the ease of soil dispersion, and other soil properties. The amount and kind of clay in a soil also affect tillage and earthmoving operations. Moist bulk density is the weight of soil (ovendry) per unit volume. Volume is measured when the soil is at field moisture capacity, that is, the moisture content at 1/3- or 1/10 -bar (33kPa or 10k Pa) moisture tension. Weight is determined after the soil is dried at 105 degrees C. In the table, the estimated moist bulk density of each soil horizon is expressed in grams per cubic centimeter of soil material that is less than 2 millimeters in diameter. Bulk density data are used to compute linear extensibility, shrink -swell potential, available water capacity, total pore space, and other soil properties. The moist bulk density of a soil indicates the pore space available for water and roots. Depending on soil texture, a bulk density of more than 1.4 can restrict water storage and root penetration. Moist bulk density is influenced by texture, kind of clay, content of organic matter, and soil structure. USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 1 of 6 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates in the table are expressed in terms of micrometers per second. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture. Saturated hydraulic conductivity (Ksat) is considered in the design of soil drainage systems and septic tank absorption fields. Available water capacity refers to the quantity of water that the soil is capable of storing for use by plants. The capacity for water storage is given in inches of water per inch of soil for each soil layer. The capacity varies, depending on soil properties that affect retention of water. The most important properties are the content of organic matter, soil texture, bulk density, and soil structure. Available water capacity is an important factor in the choice of plants or crops to be grown and in the design and management of irrigation systems. Available water capacity is not an estimate of the quantity of water actually available to plants at any given time. Linear extensibility refers to the change in length of an unconfined clod as moisture content is decreased from a moist to a dry state. It is an expression of the volume change between the water content of the clod at 1/3- or 1/10 -bar tension (33kPa or 10kPa tension) and oven dryness. The volume change is reported in the table as percent change for the whole soil. The amount and type of clay minerals in the soil influence volume change. Linear extensibility is used to determine the shrink -swell potential of soils. The shrink -swell potential is low if the soil has a linear extensibility of less than 3 percent; moderate if 3 to 6 percent; high if 6 to 9 percent; and very high if more than 9 percent. If the linear extensibility is more than 3, shrinking and swelling can cause damage to buildings, roads, and other structures and to plant roots. Special design commonly is needed. Organic matter is the plant and animal residue in the soil at various stages of decomposition. In this table, the estimated content of organic matter is expressed as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. The content of organic matter in a soil can be maintained by returning crop residue to the soil. Organic matter has a positive effect on available water capacity, water infiltration, soil organism activity, and tilth. It is a source of nitrogen and other nutrients for crops and soil organisms. Erosion factors are shown in the table as the K factor (Kw and Kf) and the T factor. Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (LISLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The estimates are based primarily on percentage of silt, sand, and organic matter and on soil structure and Ksat. Values of K range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water. Erosion factor Kw indicates the erodibility of the whole soil. The estimates are modified by the presence of rock fragments. Erosion factor Kf indicates the erodibility of the fine -earth fraction, or the material less than 2 millimeters in size. USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 2 of 6 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Erosion factor T is an estimate of the maximum average annual rate of soil erosion by wind and/or water that can occur without affecting crop productivity over a sustained period. The rate is in tons per acre per year. Wind erodibility groups are made up of soils that have similar properties affecting their susceptibility to wind erosion in cultivated areas. The soils assigned to group 1 are the most susceptible to wind erosion, and those assigned to group 8 are the least susceptible. The groups are described in the "National Soil Survey Handbook." Wind erodibility index is a numerical value indicating the susceptibility of soil to wind erosion, or the tons per acre per year that can be expected to be lost to wind erosion. There is a close correlation between wind erosion and the texture of the surface layer, the size and durability of surface clods, rock fragments, organic matter, and a calcareous reaction. Soil moisture and frozen soil layers also influence wind erosion. Reference: United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430 -VI. (http://soils.usda.gov) USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 3 of 6 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Report Physical Soil Properties Three values are provided to identify the expected Low (L), Representative Value (R), and High (H). Physical Soil Properties —Weld County, Colorado, Northern Part Map symbol Depth Sand Silt Clay Moist Saturated Available Linear Organic Erosion Wind Wind and soil name bulk hydraulic water extensibility matter factors erodibility erodibility density conductivity capacity group index Kw Kf T In Pct Pct Pct g/cc micro r/sec in/fn Pct Pct 44 -Olney fine sandy loam, 0 to 6 percent slopes Olney 0-6 -65- -20- 10-15- 20 1.35-1.43 4.00-23.00-42.0 0.13-0.14-0. 0.0- 1.5- 2.0 0.5- 0.8- .24 .24 5 3 86 -1.50 0 15 1.0 6-18 -56- -18- 18-27- 35 1.25-1.33 4.23-9.00-14.11 0.13-0.15-0. 0.0- 1.5- 2.9 0.5- 0.8- .20 .20 -1.40 17 1.0 18-60 -63- -18- 15-19- 30 1.25-1.33 4.23-9.00-14.11 0.11-0.13-0. 0.0- 1.5- 2.0 0.0- 0.3- .24 .24 -1.40 15 0.5 60-64 -64- -27- 5-10- 15 1.40-1.50 14.11-28.00-42. 0.06-0.10-0. 0.0- 1.5- 2.9 0.0- 0.3- .32 .32 -1.60 33 13 0.5 usDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 4 of 6 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Physical Soil Properties -Weld County, Colorado, Northern Part Map symbol and soil name Depth Sand Silt Clay Moist bulk density Saturated hydraulic conductivity Available water capacity Linear extensibility Organic matter Erosion factors Wind erodibility group Wind erodibility index Kw Kf T In Pct Pet Pet g/cc micro rn/sec }rain Pct Pct 54-Platner loam, percent slopes 0 to 3 Platner 0-6 35-43- 50 28-38- 50 15-19- 22 1.33-1.41 -1A9 4.23-9.17-42.34 0.14-0.15-0. 17 1.0- 2.0- 3.3 1.0- 1.5- 2.0 .43 .43 5 5 56 6-11 25-30- 42 13-30- 40 35-40- 45 1.32-1.36 -1.40 0.42-0.92-1.41 0.13-0.15-0. 16 6.0- 7.3- 8.7 1.0- 1.5- 2.0 .28 .28 11-20 25-30- 42 13-30- 40 35-40- 45 1.32-1.36 -1.40 0.42-0.92-1.41 0.13-0.15-0. 16 6.0- 7.3- 8.7 1.0- 1.5- 2.0 .28 .28 20-27 30-37- 55 11-37- 47 23-27- 34 1.45-1.56 -1.66 1.41-9.17-14.11 0.12-0.17-0. 17 0.8- 1.3- 2.6 0.5- 0.8- 1.0 .32 .32 27-37 48-61- 72 3-19- 37 15-20- 25 1.41-1.54 -1.66 4.23-9.17-42.34 0.10-0.12-0. 13 0.3- 0.9- 1.6 0.0- 0.5- 1.0 .24 .24 37-80 48-61- 72 3-19- 37 15-20- 25 1.47-1.58 -1.70 4.23-9.17-42.34 0.10-0.12-0. 13 0.3- 0.9- 1.6 0.0- 0.5- 1.0 .24 .24 55-Renohill sandy 0 to 6 fine loam, percent slopes Renohill 0-5 -65- -20- 13-16- 19 1.35-1.43 -1.50 4.00-23.00-42.0 0 0.13-0.14-0. 15 0.0- 1.5- 2.9 1.0- 1.5- 2.0 .24 .24 3 3 86 5-18 -27- -29- 35-45- 55 1.15-1.28 -1.40 0.42-1.00-1.41 0.14-0.17-0. 20 6.0- 7.5- 8.9 0.5- 0.8- 1.0 .24 .24 18-32 -37- -36- 20-27- 34 1.25-1.33 -1.40 1.41-8.00-14.11 0.16-0.18-0. 19 0.0- 1.5- 2.9 0.0- 0.5- 1.0 .37 .37 32-36 - - - - 0.42-1.00-1.41 - - - USDA Natural Resources a Conservation Service Web Soil Survey National Cooperative Soil Survey 4/5/2018 Page 5of6 Physical Soil Properties ---Weld County, Colorado, Northern Part Makena Gas Plant Data Source Information Soil Survey Area: Weld County, Colorado, Northern Part Survey Area Data: Version 12, Oct 10, 2017 USDA Natural Resources Web Soil Survey a Conservation Service National Cooperative Soil Survey 4/5/2018 Page 6of6 APPENDIX B Hydrologic Calculations (Historic & Developed Condition) Rational Method Calculations Weighted "C" Calculations Weighted Slope Calculations Time of Concentration Runoff Calculations Hydrologic Calculation Reference Materials Percent Imperviousness Values (UDFCD) Comp C Runoff Coefficients (UDFCD) Time of Concentration (UDFCD) NOAA Atlas 14, Vol 8, Ver 2 — Point Precipitation Frequency Estimates (NOAA) Intensity -Duration Curves for Rational Method (UDFCD) Rational Method Calculations Pro,ce: No. 18009 Makena Gas Plant Final Drainage Report 5/4/2018 10:38 PM WEIGHTED "C" CALCULATIONS - REFERENCE UDSCM {VOL. 1) Table 6-3. Recommended Percentage Imperviousness Values (March 2017) - REFERENCE UDSCM {VOL_ 1), Table 6-4. Runoff Coefficient Equations Bused on MRCS Soil Group (Ind Storm Return Period (March 2017) Historic/ Open Space Roof,. Drives & Walks Pavement, Pond Industrial (Light Areas) Gravel Surfacing Channels/ Side Slopes b0 I mperv. SOIL HYDRO 2O 90 0 100e 80e 40 v 44'a Total Total Percent A SOIL B SOIL C/D SOIL 2 year 5 year 10 year 100 Year BASIN GROUP Area Area Area Area Area Area Area Itr) Area (Ac) Impervious AREA AREA AREA C C C C H1 Li 1,D27.830 1,027,630 23.60 2.0t 0.00 0.010 23.60 G.01 0.05 0.15 0,49 D1 I? 454,688 454,688 10.44 40.0/0 0.00 10,44 1.30 0.36 0.43 0.65 (32 L1 2,664 472,350 475,014 10.90 40,3,rn 0.00 110.90 10.30 0.37 0.43 0,65 (33 U 98.129 98,129 3.25 100.0/0 0.00 2,25 10.83 0.86 0.87 10.89 SUM D1 -D3 0 2,664 98.129 0 927,038 0 1,027,8.31 23.60 45,9,O 0.00 23.60 0,35 0.41 0.47 0,67 KIRCS Soil Types Runoff Coefficients Storm Return Period 2-yr 5-yr 10-yr 25-yr .50-yr 100-yr A CA=0.84i' $ry CA=0,86i'''r CA=0,87i'' , CA=0,84i11'° CA=0.85i+0.025 CA=0.78i+0.110 B C8=0,84i1'icu C6=G.86i-'r'`� CB=D.R1it0.057 C8=0.53H-0.249 CB=0.56H-0328 C6rD.47itO.425 C {D CrfD=0_$.3ii._zz Cr/D=O.821+D.035 CrID=O.741+0.132 CrID=O.561+0..319 CrfD=O.49i+D .393 Cr/D=O_41i+D 484 in which: r = I ; /100, imperviousness ratio I ; = watershed imperviousness in percent Cres:onc Gansu :an:s. L LC Page 10 7 Project No. 18009 WEIGHTED "SLOPE" CALCULATIONS -REFERENCE UDSCM (VOL. 1), Equation 6-7 & Figure 6-4. Slope Correction for Streams and Vegetated Channels Makena Gas Plant Final Drainage Report 5/4/2018 1D:38 PM TRAVEL SEGMENTS DESIGN MEASURED ADJUSTED MEASURED ADJUSTED MEASURED ADJUSTED MEASURED ADJUSTED TOTAL WEIGHTED BASIN POINT LENGTH 1 SLOPE 1 SLOPE 1 LENGTH 2 SLOPE 2 SLOPE 2 LENGTH 3 SLOPE 3 SLOPE 3 LENGTH 4 SLOPE 4 SLOPE 4 LENGTH SLOPE _ ft°° ft 4#eu 46 ft A° e`° ft I° ,64 ft i° H1 74 0.10,O D.104; 350 1.31,E 1.3141 329 0.804b D.804; 282 1.674 1,674; 103S 1.O04) D1 1. 11 22,7040 22.72O 633 0.90O 0.9040 8 25.0040 25.0040 665 0.754b 0,7540 1317 0.9040 D2 D3 2 3 11 129 22,70, 0.7540 22.7DO 0.754) 490 529 0.904 0.504 D,90, 0.5040 9 2S,D0, ; 25.O0.0 828 0.7S D,7.54: 1.338 658 0.90,) 0.50,0 Crestone Consultants, LLC Page 2 of 7 Project No. 18009 TIME OF CONCENTRATION Forest & Heavy Meadow Tillage/Field Ma Marta Gas Plant Final Drainage Report Watercourse Coefficient 2.5 Short Pasture & Lawns 7 5 Nearly Bare Ground 10 Paved Areas & Shallow Paved Swales 5/4/2018 10:38 PM Grassed Waterway 15 20 SUB -BASIN DATA INITIAL/ TIME OVERLAND TRAVEL TIME T(t) T(c) (URBANIZED & CHECK BASINS) FINAL T(c) DESIGN DRAIN AREA C(S) Length Slope T(i) Length Slope Coeff. T(t) COMP. TOTAL i T(c) CHECK POINT BASIN ac, ft, ° min ft. "o min, T(c) LENGTH Imp Ratio UDFCD Eq 6-5 min, Hi 23.60 0.05 300 1.0 32.8 735 1.0 5.0 24.5 57.3 1035 0.02 N/A 57.3 1 D1 10.44 0.3E 100 0.9 13.8 1217 0.9 15.0 14.3 28.1 1317 0.40 35.0 28.1 2 D2 10.90 0.37 100 0.9 13.7 1238 0.9 15.0 14.5 28.2 1338 0.40 35.2 28.2 3 D3 215 0,86 50 0.5 3.9 608 0,5 15+0 9.6 13,5 658 1.00 15.7 13,5 Crestone Consultants, LLC Page 3 of 7 Project No. 18009 RUNOFF CALCULATIONS (Rational Method Procedure) Ma Marta Gas Plant Final Drainage Report = 28.5 R1( 10+Tc.ss Rainfall Depth -Duration -Frequency (1 -hr) = (From NOAA Atlas 14, Vol 8, Ver 2 - Briggsdale, CO) 0.92 Design Storm 2 Year REMARKS BASIN INFORMATION DIRECT RUNOFF TOTAL RUNOFF DESIGN POINT DRAIN BASIN AREA ac. RUNOFF COEFF Tic) miry C x A I inihr Q cfs Tic) mire SUM C x A I inihr Q cis 1 2 3 Hi D1 D2 D3 2160 10.44 10.90 2.25 0,01 0.30 0.30 0.83 57,3 28.1 28.2 13.5 0,24 3.10 3.26 1.87 0,95 1.49 1.49 2.18 0,2 4.6 4.9 4.1 28.2 8.23 1.49 12.3 SUM D1 -D3 5/4/2018 10:38 PM Crestone Consultants, LLC Page 4 of 7 Project No. 18009 RUNOFF CALCULATIONS (Rational Method Procedure) Makena Gas Plant Final Drainage Report = 28.5 R1/(19+T °'86 Rainfall Depth -Duration -Frequency (1 -hi) = (From NOAA Atlas 14, Vol 8, Ver 2 - Briggsdale, CO) 1.19 Design Storm 5 Year REMARKS BASIN INFORMATION DIRECT RUNOFF TOTAL RUNOFF DESIGN POINT DRAIN BASIN AREA ac. RUNOFF COEFF T(c) min C x A I ire/hr Q cfs T(c) min SUM C x A I in/hr Q cfs 1 2 3 Hi D1 D2 D3 23.60 10.44 10.90 2,25 0.05 0.36 0.37 0.86 57.3 28.1 28.2 13.5 1.21 3.79 3.98 1.93 1.24 1.94 1.94 2.84 1,5 7.4 7.7 5.5 28.2 9.70 1.94 18.8 SUM Dl -D3 5/4/2018 10:38 PM Crestone Consultants, LLC Page 5 of 7 Project No. 18009 RUNOFF CALCULATIONS (Rational Method Procedure) Makena Gas Plant Final Drainage Report = 28.5 81/(19+T °'86 Rainfall Depth -Duration -Frequency (1 -hi) = (From NOAA Atlas 14, Vol 8, Ver 2 - Briggsdale, CO) 1.45 Design Storm 10 Year REMARKS BASIN INFORMATION DIRECT RUNOFF TOTAL RUNOFF DESIGN POINT DRAIN BASIN AREA ac RUNOFF COEFF T(c) min C x A I ire/hr cfs Q T(c) min SUM C x A I in/hr Q cfs 1 2 3 Hi D1 D2 D3 23.60 10.44 10.90 2,25 0.15 0.43 0.43 0.87 57.3 28.1 28.2 13.5 3.46 4.47 4.69 1.96 1.51 2.36 2.36 3.46 10.6 11.1 5.2 6.8 28.2 11.12 2.36 26.2 SUM D1 -D3 5/4/2018 10:38 PM Crestone Consultants, LLC Page 6 of 7 Project No. 18009 RUNOFF CALCULATIONS (Rational Method Procedure) Ma Marta Gas Plant Final Drainage Report = 28.5 81(10+T)°.8s Rainfall Depth -Duration -Frequency (1 -hr) From NOAA Atlas 14, Vol 8, Ver 2 - Briggsdale, CO) 2.57 Design Storm 100 Year REMARKS BASIN INFORMATION DIRECT RUNOFF TOTAL RUNOFF DESIGN POINT DRAIN BASIN AREA ac. RUNOFF COEFF Tic) miry C x A I inihr Q cfs Tic) mire SUM C x A I inihr Q cis 1 2 3 Hi D1 D2 D3 23.60 10.44 10.90 2.25 0.49 0.65 0.65 0.89 57.3 28.1 28.2 13.5 11,61 6.76 7.08 2.01 2.68 4.19 4.18 6.13 31.1 28.3 29.6 12.3 28.2 15.86 4.18 66.3 SUM D1 -D3 5/4/2018 10:38 PM Crestone Consultants, LLC Page 7 of 7 Hydrologic Calculation Reference Materials Table 6-3. Recommended percentage imperviousness values i _ Surface Land Use Characteristics or Percentage Imperviousness (%) Business: Downtown Areas 95 Suburban Areas 75 Residential lots (lot area only): Single-family 2.5 acres or larger 12 0.7 2.5 acres 20 — 0.25 — 0.75 acres 30 0.25 acres or less 45 Apartments 75 Industrial: Light areas 80 Heavy areas 90 Parks, cemeteries 10 Playgrounds ' 5 Schools 55 Railroad yard areas 50 Undeveloped Areas: Historic flow analysis Greenbelts, agri cultural 2 Off -site defined) flow analysis (when land uSC not 45 Streets: Paved 100 Gravel (packed) 40 Drive and walks 90 Roofs 90 Lawns, sandy soil Lawns, clayey soil 2 HISTORIC CONDITION DEVELOPED CONDITION - POND DEVELOPED CONDITION - ROADS! CHANNELS DEVELOPED I CONDITION - ROOFS 6-8 Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual Vol • e 1 March 2017 Table 6-4. Runoff coefficient equations based on NRCS soil group and storm return period Storm Return Period NRCS Soil Group 2 -Year 5 -Year 10 -Year 25 -Year 50 -Year 100 -Year 500 -Year A CA— CA C = CA CA CA 0.8411.302 0.8611.27° 0.87i1-232 0.8411.124 A 0.851+0.025 0.781+0.110 0.651+0.254 B CB= CB = CB CB = CB= CB = CB 0.86i1.M88 0.471+0.426 0.8411.169 0.811+0.05 0.631+0.249 0.56H-0.328 0.371+0.536 C D COD— CC.ID CC COD GOOD COD 0.83i1.122 0.821+0.035 0.741+0.132 /ii 0.561+0.319 0.491+0.393 0.411+0.484 cmD 0.321+0.588 Where: CB °A) imperviousness (expressed as a decimal) Runoff coefficient for Natural Resources Conservation Service (NRCS) HSG A soils Runoff coefficient for NRCS HSG B soils = Runoff coefficient for NRCS 14SG C and D soils. The values for various catchment imperviousness and storm return periods are presented graphicallin Figures 6-1 through 6-3, and are tabulated in Table 6-5. These coefficients were developed for the Denver region to work in conjunction with the time of concentration recommendations in Section 2.4. Use of these coefficients and this procedure outside of the semi -arid climate found in the Denver region may not be valid. The UD-Rational Excel workbook performs all the needed calculations to find the runoff coefficient given the soil type and imperviousness and the reader may want to take advantage of this macro- enabled Excel workbook that is available for download from the UDFCD's website www.udfcd.org. See Examples 7.1 and 7.2 that illustrate the Rational Method. March 2017 Urban Drainage and Flood Control District 6-9 Urban Storm Drainage Criteria Manual Vol e 1 Table 6-5. Runoff coefficients, c Impervious or Effective NRCS Hydrologic Soil Group A Total % 2 -Year 5 -Year 10 -Year 25 -Year 50 -Year 100 -Year 500 -Year 2% 0.01 0.01 0.01 0.01 0.04 0.13 0.27 5% 0.02 0.02 0.02 0.03 0.07 0.15 0.29 10% 0.04 0.05 0.05 0.07 0.11 0.19 0.32 15% 0.07 0.08 0.08 0.1 0.15 0.23 0.35 20% 0.1 0.11 0.12 0.14 0.2 0.27 0.38 25% 0.14 0.15 0.16 0.19 0.24 0.3 0.42 30% 0.18 0.19 0.2 0.23 0.28 0.34 0.45 35134 0.21 0.23 0.24 0.27 0.32 0.38 0.48 40% 0.25 0.27 0.28 0.32 0.37 0.42 0.51 45% 0.3 0.31 0.33 0.36 0.41 0.46 0.54 50% 0.34 0.36 0.37 0.41 0.45 0.5 0.58 55% 0.39 0.4 0.4.E 0.45 0.49 0.54 0.61 60% 0.43 0.45 0.47 0.5 0.54 0.58 0.64 65% 0.48 0.5 0,51 0.54 0.58 0.62 0.67 70% 0.53 0.55 0.56 0.59 0.62 0.65 0.71 75% 0.58 0.6 0.61 0.64 0+66 0.69 0.74 80% 0.63 0.65 0.66 0.69 0.71 0.73 0.77 85% 0.68 0.7 0.71 0.74 0.75 0.77 0.8 90°'% 0.73 0.75 0.77 0.79 0.79 0.81 0.84 95% 0.79 0.81 0.82 0.83 0+84 0.85 0.87 100% 0.84 0.86 0.87 0.88 0.88 0.89 0.9 Total % or Effective Impervious NRCS Hydrologic Soil Group B 2 -Year 5 -Year 10 -Year 25 -Year 50 -Year 100 -Year 500 -Year 2% 0.01 0.01 0.07 0.26 0.34 0.44 0.54 5% 0.03 0.03 0.1 0.28 0.36 0.45 0.55 10% 0.06 0.07 0.14 0.31 0.38 0.47 0.57 15% 0.09 0.11 0.18 0.34 0.41 0.5 0.59 20% 0.13 0.15 0.22 0.38 0.44 0.52 0.61 25% 0.17 0.19 0.26 0.41 0.47 0.54 0.63 30`0 0.2 0.23 0.3 0.44 0.49 0.57 0.65 35% 0.24 0.27 0.34 0.47 0.52 0.59 0.66► 40% 0.29 0.32 0.38 0.5 0.55 0.61 0.68 45% 0.33 036 0.42 0.53 0.58 0.64 0.7 50% 0.37 0.4 0.46 0.56 0.61 0.66 0.72 55% 0.42 0.45 0.5 0.6 0.63 0.68 0.74 60% 0.46 0.49 0.54 0.63 0.66 0.71 0.76 65% 0.5 0.54 0.58 0.66 0.69 0.73 0.77 70% 0.55 0.58 0.62 0.69 0.72 0.75 0.79 75% 0.6 0.63 0.66 0.72 0.75 0.78 0.81 80% 0.64 0.67 0.7 0.75 0.77 0.8 0.83 85% 0.69 0.72 0.74 0.78 0.8 0.82 0.85 90% 0.74 0.76 0.78 0.81 0.83 0.84 0.87 95% 0.79 0.81 0.82 0.85 0.86 0.87 0.88 100% 0.84 0.86 0.86 0.88 0.89 0.89 0+9 6-10 Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual Vol e March 2017 Table 6-5. Runoff coefficients, c (continued) Impervious or Effective NRCS Hydrologic Soil Group C Total % 2 -Year 5 -Year 10 -Year 25 -Year 50 -Year 100 -Year 500 -Year 2% 0.01 0.05 0.15 0.33 0.40 0.49 0.59 5% 0.03 0.08 0.17 0.35 0.42 0.5 0.6 10% 0.06 0.12 0.21 0.37 0.44 0,52 0.62 15% 0.1 0.4 0.47 0,55 ,5 5� 0.64 20% 0.14 0.2 0.28 0.43 0.49 �Yf0.24 �� 0,57 • 0,65 2.5% 0.18 0.24 0.32 0.46 a52 0.59 0.67 30% 0.22 0.28 0.35 0.49 0.54 0.61 0.68 35% 0.26 0.32 0.39 0.51 0.57 0.63 0.7 �i % 0►3 0,36 + 0.43 0.54 0.59 0.65 + 0.�'I' 1 45% 0.34 .4 0.46 0.57 Vf . ✓ i 0.62 0, f 0.73 50% 0.38 0.44V 0.5 0.6 0.64 / 0.69 /0j /3 V.75 55% 0.43 0.48 0.54 0.63 0.66 0.71^ 0.76 60% 0.47 0.52 0.57 0.65 0.69 0.73 3 ' 0.78 65% 0.51 0.56 0.61 0.68 0.71 0.75 0.79 70% 0.56 0.61 0.65 0.71 0.74 0.77 0.81 75% 0.6 0.65 0.68 0.74 0.76 0.79 0.82 80% 0.65 0.69 0.72 0.77 7 f V. 79 0.84 85% 0.7 0.73 0.76 �.f 0.79 i! 0.81 +0.81 0 .83 0.86 90% 0.74 0.77 0.79 0.82 0.84 0.85 0.87 95% 0.79 0.811 0.83 0.85 0.86 0.87 0.89 100% 0.83 0.85 + 0.87 0.88 0.89 0.89 0.9 C 1U LT C L4 d i 7 1.00 0.80 U _ 60 _ 4 0.20 0.00 0 10 20 30 40 50 60 70 80 `0 100 Watershed Percentago Imperviousness.,, % Figure 6-1. Runoff coefficient vs. watershed imperviousness NRCS HSG -- 5- yr O10 -0-50-yr X 100-yr March 2017 Urban Drainage and Flood Control District 6-11 Urban Storm. Drainage Criteria Manual Volume 1 2.3 Limitations The Rational Method is the simplistic approach for estimating the peak flow rate and total runoff volume from a design rainstorm in a given catchment. Under the assumption of uniform hydrologic losses, the method is limited to catchments smaller than 90 acres. Under the condition of composite soils and land uses, use an area -weighted method to derive the catchment's hydrologic parameters. The greatest drawback to the Rational Method is that it normally provides only one point (the peak flow rate) on the runoff hydrograph. When the areas become complex and where subcatchments come together, the Rational Method will tend to overestimate the actual flow, which results in oversizing of drainage facilities. The Rational Method provides no means or methodology to generate and route hydrographs through drainage facilities. One reason the Rational Method is limited to small areas is that good design practice requires the routing of hydrographs for larger catchments to achieve an economically sound design. Another disadvantage of the Rational Method is that with typical design procedures, one normally assumes that all of the design flow is collected at the design point and that there is no water running overland to the next design point This is not an issue of the Rational Method but of the design procedure. Use additional analysis to account for this scenario. 2A Time of Concentration One of the basic assumptions underlying the Rational Method is that runoff is linearly proportional to the average rainfall intensity during the time required for water to flow from the most remote part of the drainage area to the design point. In practice, the time of concentration is empirically estimated along the selected waterway through the catchment. To calculate the time of concentration, first divide the waterway into overland flow length and channelized flow lengths, according to the channel characteristics. For urban areas (tributary areas of greater than 20 percent impervious), the time of concentration, tc, consists of an initial time or overland flow time, t,, plus the channelized flow travel time, t1, through the storm drain, paved gutter, roadside ditch, or channel. For non -urban areas, the time of concentration consists of an overland flow time, t;, plus the time of travel in a defined drainage path, such as a Swale, ch nel, or stream. Estimate the channelized travel time portion, tt, of the time of concentration from the hydraulic properties of the conveyance element. Initial or overland flow time, on the other hand, will vary with surface slope, depression storage, surface cover, antecedent rai a all, and infiltration capacity of the soil, as well as distance of surface flow. Compute the time of concentration for both urban and non -urban areas using Equation -: Where: ti+tt computed time of concentration (minutes) t; = overland (initial) flow time (minutes) tt = channelized flow time (minutes). Equation 6-2 6-4 Urban Drainage and Flood Control District March 2017 Urban Storm Drainage Criteria Manual Vol l e 1 24.1 Initial or Overland Flow Time The initial or overland flow time, t1, may be calculated using Equation 6-3: 0.3950.1— C5}11, U.33 o Where: Equation 6-3 t; = overland (initial) flow time (minutes) Cs = runoff coefficient for -year frequency (from Table 6-4) L; = length of overland flow (ft) S0 = average slope along the overland flow path (ft/ft) Equation 6-3 is adequate for distances up to 300 feet in urban areas and 500 feet in rural areas. Note that in a highly urbanized catchment, the overland flow length is typically shorter than 300 feet due to effective man-made drainage systems that collect and convey runoff 2.4.2 Channelized Flow Time The channelized flow time (travel time) is calculated using the hydraulic properties of the conveyance element. The channelized flow time, tt, is estimated by dividing the length of conveyance by the velocity. The following equation, Equation 6-4 (Guo 2013), can be used to determine the flow velocity in conjunction with Table 6-2 for the conveyance factor. Where: L, Li 60K . ,' 60V, t, = channelized flow time (travel time, min) Lt = waterway length (ft) So = waterway slope (;ftl t;) Vt = travel time velocity (ft/sec) = ICA/So K = MRCS conveyance factor (see Table 6-2). Table 6-2. MRCS Conveyance factors, K Equation 6-4 Conveyance Factor, K Type of Land Surface Heavy meadow 2.5 5 Tillage/field Short pasture and lawns 7 Nearly bare ground 10 Grassed waterway 15 Paved areas and shallow paved swales 20 March 2017 Urban Drainage and Flood Control District 6-5 Urban Storm Drainage Criteria Manual Vol e 1 The time of concentration, te, is the sum of the initial (overland) flow time, t1, and the channelized flow time, tt, as per Equation 6-2. 2.4.3 First Design Point Time of Concentration in Urban Catchments Equation 6-4 was solely determined by the waterway characteristics and using a set of empirical formulas. A calibration study between the Rational Method and the Colorado Urban Hydrograph Procedure (CUHP) suggests that the time of concentration shall be the lesser of the values calculated by Equation 6- 2 and Equation 6-5 (Guo and Urbonas 2013). (26— 17i + Equation 6-5. 6004i + 91) ,, Where: t, = minimum time of concentration for first design point when less than to from Equation 6-1. L, = length of channelized flow path (ft) i ` imperviousness (expressed as a decimal) St = slope of the channelized flow path (ftlft). Equation 6-5 is the regional time of concentration that warrants the best agreement on peak flow predictions between the Rational Method and CUHP when the imperviousness of the tributary area is greater than 20 percent. It was developed using the UDFCD database that includes 295 sample urban c atc. • ents under 2-, 5-, 10-, 50, and 100-yr storm events (MacKenzie 2010) . It suggests that both initial flow time and channelized flow velocity are directly related to the catchment's imperviousness (Guo and MacKenzie 2013). The first design point is defined as a node where surface runoff enters the storm drain system. For example, all inlets are "first design points" because inlets are designed to accept flow into the storm drain. Typically, but not always, Equation 6-5 will result in a lesser time of concentration at the first design point and will govern in an urbanized watershed. For subsequent design points, add the travel time for each relevant s eg i ent downstream. 2.4.4 Minimum Time of Concentration Use a minimum to value of 5 minutes for urbanized areas and a minimum t, value of 10 minutes for areas that are not considered urban. Use minimum values even when calculations result in a lesser time of concentration. 14.5 Common Errors in Calculating Time of Concentration A common mistake in urbanized areas is to assume travel velocities that are too slow. Another common error is to not check the runoff peak resulting from only part of the catchment. Sometimes a lower portion of the catchment or a highly impervious area produces a larger peak than that computed for the whole catchment. This error is most often encountered when the catchment is long or the upper portion contains grassy open land and the lower portion is more developed. 6-6 Urban Drainage and Flood Control District March 2017 Urban Storm Drainage Criteria Manual Vol l e 1 4/5/2018 Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Briggsdale, Colorado, USA* Latitude: 40.6297°, Longitude: -104.2604° Elevation: 5014.82 ft** * source: ESRI Maps * source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Deborah Martin, Sandra Pavtovic, Isharii Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoifery 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 inch a)1 Average recurrence interval (years) Duration I 1 2 I 5 I '1 1 L 25 50 100 1000 -min 0.256 (0.198-0.332) 0.308 (0.238-0.399) 0.402 (0.309-0.521) 0.489 (0.374-0.637) 0.622 (0.467-0.848) 0.735 (0.537-1.01) 0.858 (0.606-1.20) 0.991 (0.672-1.41) 1.18 (0.772-1.72) 1.34 (0.847-1.95) 10 -min 0.375 (0.290-0.486) 0.451 (0.348-0.584) 0.588 (0.453-0.764) 0.716 (0.548-0.932) 0.911 (0.684-1.24) l 1.08 (0.786-1.48) 1.26 (0.887-1.75) 1.45 (0.985-2.07) 1.73 (1.13-2.52) 1.96 (1.24-2.86) 15 -min 0.457 (0.354-0.592) I 0.550 (0.425-0.712) 0.7'17 (0.552-0.931) 0.873 (0.668-1.14) 1.11 (0.834-1.51) 1.31 (0.959-1.80)1 1.53 1.08-2.14) 1.77 (1.20-2.52) 2.11 (1.38-3.07) 2.39 (1.51-348) I 30 -min 0.619 (0.479-0.802) 0.744 (0.574-0.963) 0.968 (0.746-1.26) 1.18 (0.900-1.53) 1.49 (1.12-2.03) 1.76 (1.28-2.40n 2.04 (1.44-2.85) 2.35 (1.60-3.35) 2.80 (1.83-4.06) 3.16 (2.00-4.60) 60 -min 0.768 (0.594-0.994) 0.915 (0.707-1.19; 1.19 (0.916-1.54) 1.45 (1.11-1.89) 1.85 (1.39-2.5'3) 2.19 (1.61-3.02) 2.57 ( 1.82-3.60) 2.99 (2.03-4.26) 3.59 (2.34-5.22) 4.08 (2.58-5.94) 2 -hr 0.917 i (0.717-1.17) 1.09 (0.849-1.39) 1.41 (1.10-1.81) 1.72 (1.33-2.22) 2.21 (1.69-3.00) 2.64 (1.95-3.59) 3.10 (2.22-4.30) 3.62 (2.49-5.13) 4.38 (2.89-6.32) 5.00 (3.20-7.22) 3 -hr 0.998 (0.786-1.27) 1.18 (0.925-1.50) 1.52 (1.19-1.94) 1.86 (1.45-2.38) + 2.88 (2.15-3.90) I 3.41 (2.46-4.71) 4.00 (2.77-5.63) I 4.86 (3.24-6.98) 5.58 (3.59-8.01). 6 -hr 1.14 (0.910-1.44) 1.35 t (1.07-1.70) 1.74 (1.38-2.20) 2.13 (1.68-2.69) 2.73 (2.13-3.65) i 3.26 (2.46-4.37) i 3.85 (2.81-5.25) 4.50 (3.15-6.27) 5.45 (3.67-7.74) 6.23 (4.06-8.85) i 12 -hr 1.31 (1.06-1.63) 1.56 (1.26-1.94) 2.02 (1.62-2.51) I 2.43 (1.94-3.04) 1 3.07 (2.40-4.01) 3.60 (2.74-4.74) 4.18 (3.07-5.61) 4.81 (3.39-6.59) 5.70 i (3.87-7.98) 6.43 (4.23-9.04) 24 -hr 1.55 (1.26-1.90) 1.81 (1.47-2.22) 2.28 (1.85-2.80) 2.71 (2.19-3.34) 3.35 (2.65-4.32) 3.90 (3.00-5.07) 4.49 x(3.34-5.95) 5.13 (3.65-6.94) 6.03 (4.14-8.35) 6.77 (4.50-9.42) 2 -day 1.77 (1.46-2.15) 2.06 (1.70-2.50) 2.58 (2.12-3.13) I 3.03 (2.48-3.70) 1 3.71 (2.95-4.70) I 4.26 (3.31-5.45) 4.85 (3.64-6.33) 5.47 (3.94-7.31) 6.35 (4.39-8.68) 7.05 (4.74-9.71) 3-da I ll 1.94 (1.61-2.33) 2.23 (1.86-2.69) 2.74 I (2.27-3.31) 3.20 (2.64-3.88) 3.88 (3.11-4.88) 4.43 (3.4T5.64) 5.03 (3.80-6.52) 5.66 (4.10-7.51) 6.54 (4.56-8.89) 7.25 (4.91-9.93) 4 -day 2.07L (1.73-2.48) 2.37 (1.98-2.84) 2.89 (2.40-3.47) 3.35 (2.77-4.04) 4.03 (3.25-5.04 ) 4.58 (3.60-5.79 ) 1 5.17 3.93-6.68 ( ) 5.80 (4.23-7.66 ) 6.69 (4.68-9.04) 7.39 (5.02.10.1) A 7 -day 2.36 (2.00-2.80) 2.71 (2.29-3.22) 3.29 (2.77-3.91) 3.78 (3.16-4.52) 4.49 (3.64-5.52) 5.05 (3.99-6.29) 5.62 (4.30-7.15) 6.22 (4.56-8.11) 7.04 (4.96-9.40) 7.67 (5.26-10.4) 10 -day 2.62 (2.23-3.09) I 3.01 (2.56-3.55) 3.64 (3.08-4.30) 4.17 (3.51-4.94) 4.89 (3.98-5.97) 5.46 (4.34-6.74) ° 6.03 (4.63-7.61) 6.61 (4.87-8.55) 7.39 (5.23-9.79) 7.98 (5.50-10.7) 20 -day 3.41 (2.94-3.97 3.87 (3.33-4.51) 4.60 (3.95-5.38) 5.20 (4.44-6.10 6.01 (4.94-7.21) 6.62 (5.32-8.05) 7.22 (5.61-8.98) 7.82 (5.82-9.96) 8.59 (6.15-11.2) 9.16 (6.40-12.2) 30 -day 4.08 (3.54-4.71) 4.60 (3.99-5.32) 5.44 I (4.70-6.30) I 6.11 (5.25-7.11) 7.00 I (5.79-8.32) I 7.67 1 (6.21-9.24) 8.31 (6.50-10.2) 8.94 (6.70-11.3) 9.74 (7.02-12.6) 10.3 (7.26-13.6) 45 -day 4.92 (4.30-5.64) 5.55 " (4.85-6.37) 6.55 (5.70-7.53) 7.34 (6.35-8.47) 8.36 (6.96-9.84) 9.'17 (7.42-10.9) 9.81 (7.72-12.0) 10.5 (7.90-13.1) . 11.3 (8.19-14.8 11.9 (8.41-15.6) 60 -day 5.62 (4.95-6.41) 6.37 (5.60-7.28) 7.54 (6.61-8.63) 8.45 (7.36-9.71) 9.61 (8.02-11.2) 10.4 (8.53-12.4) ft 11.2 (8.83-13.6) 11.9 (8.99-14.8) 12.7 (9.25-16.3) 13.3 (9.44-17.4) 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://hdsc.nws.noaa.gov/hdsclpfds/pfds_printpage.h4 I?lat-4O.6297&Ion=-104.2604&data-depth&unifs=english&series=pds 1/4 4/5/2018 Precipitation Frequency Data Server raw I um minai PDS-based depth -duration -frequency (DDF) curves Latitude: 40.629P, Longitude: -L04..2604, ccill C rn 5 10 25 50 100 200 NOAH, Atlas 14, Volume El, Version 2 th th aC rti Duration >I>s IT IT13 rn 'KZ Average recurrence interval (years) 0 0fin 13 13 500 1000 Created (GMT): Thu Apr 5 22:17:56 201a Back to Top Maps & aerials Small scale terrain :rage recurrence irtert a I (years) 1 2 10 25 100 200 500 1000 D&t.I.t aiJ u n 5 -min 1 trtrt 1 in 3O -min 60 -nn 2 -hr 3 -hr 6 -hr 12 -hr 24-thr 2 -day 3 -clay 4 -day 7 -day 10 -days 20 -day 30i -day 45 -day 60 -day https://hdsc.nws.noaa.gov/hdsclpfds/pfds_printpage.h 4 Plat-40.6297&Ion=-104.2604&data-depth&unifs=english&serial=pds 2/4 4/5/2018 Precipitation Frequency Data Server Ir ese unth- Rd 90 C 3km 2mi off 0 Irk + w _ fl PM 0 . 1 Large scale terrain Fortcollins Liincr, Pei* :41345 I Sri Pi edit; ine et...N alien al • Forest. Boulder. • c:heyenne • Longmont i e Denver 100km I km i Fort Colig s u N Large scale map CI'i .. enn Greelel c� rant Boulder Eambf 100km 1 demi 1 Large scale aerial https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=40.6297&Ion=-104.2604&data=depth&units=english&series=pds 3/4 41512018 Precipitation Frequency Data Server Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: H DSC.Questions@noaagov Disclaimer https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=40.6297&Ion=-104.2604&data=depth&units=english&series=pds 414 Chapter 5 Rainfall 4.0 Intensity -Duration Curves for Rational Method To develop depth -duration curves or intensity -duration curves for the Rational Method of runoff analysis take the 1 -hour depth(s) obtained from NOAA Atlas 14 and apply Equation 5-1 for the duration (or durations) of interest: 1 28.5 P (10 + Td )°''86 Where: 1 = rainfall intensity (inches per hour) P, = 1 -hour point rainfall depth (inches) storm duration (rn'iutcs) Equation 5-1 March 2017 Urban Drainage and Flood Control District 5-9 Urban Storm Drainage Criteria Manual Volume 1 APPENDIX C Hydraulic Calculations (Historic & Developed Condition) Channel Sizing Calculations Detention Pond Sizing Calculations Hydraulic Calculation Reference Materials Riprap Channel Manning's n Values (Weld County) Riprap Sizing (UDFCD/USAGE) Calculation of WQCV (UDFCD) Channel Sizing Calculations Channel Report Hydraflow Express Extension for Autodesk® AutoCADO Civil 3D® by ALitodesk, Inc. Channel 7 (CHI) - Basin Dl - Q100 = 28.3 cfs Trapezoidal Bottom Width (ft) Side Slopes (z:1) Total Depth (ft) Invert Elev (ft) Slope (°/a) N -Value Calculations Compute by: Known Q (cfs) Elev (ft) 103.00 102.50 102.00 101.50 101.00 100.50 100.00 99.50 5.00 4.00, 4.00 _ 2.00 100.00 = 0.75 = 0.045 Known Q _ 28.30 Section Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s} Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) Friday, May 4 2018 1.20 28.30 11.76 2A1 14.90 0.81 14.60 = 1.2 Depth (ft) 0 5 10 15 20 25 30 35 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCADO Civil 3D® by ALitodesk, Inc. Channel 2 (CH2) - Basin D2 - Q100 = 29.6 cfs Trapezoidal Bottom Width (ft) Side Slopes (z:1) Total Depth (ft) Invert Elev (ft) Slope (°/a) N -Value Calculations Compute by: Known Q (cfs) Elev (ft) 103.00 102.50 102.00 101.50 101.00 100.50 100.00 99.50 5.00 4.00, 4.00 _ 2.00 100.00 _ 0.75 = 0.045 Known 29.60 Section Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s} Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) Friday, May 4 2018 1.22 29.00 12.05 2.46 15.06 0.83 14.76 1.31 Depth (ft) 0 5 10 15 20 25 30 35 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 Reach (ft) Detention Pond Sizing Calculations Project No. 18009 Makena Gas Plant Final Drainage Report DETENTION POND - WATER QUALITY CAPTURE VOLUME (WQCV) CALCULATIONS -REFERENCE UDFCD DRAINAGE CRITERIA MANUAL VOL. 3 - CHAPTER 3 Water Quality Capture Volume = WQCV = a*(0.91/3-1.1912+0.781) (watershed inches) I = Total Imperviousness Ratio = Iwc/100 a = 40 -hr Drain Time = 1.0 BASIN DESIGN POINT IMPERVIOUSNES (percent) PERCENT S� I ,� wQ IMPERVIOUSNESS RATIO, l WATER QUALITY CAPTURE VOLUME, WQCV (watershed inches) . - D1 -D3 I 1 45.9 1 0.46 I 0.20 -REFERENCE UDFCD DRAINAGE CRITERIA MANUAL VOL. 3 - CHAPTER 3 Required Storage = [WQCV/12]*A*1.2 (acre -ft) A = Tributary Catchments Area (acres) 1.2 Factor = Multiplier to account for 20% sediment accumulation BASIN DESIGN POINT TRIBUTARY AREA, (acres) A* REQUIRED QUALITY (acre STORAGE -ft) WATER REQUIRED QUALITY (ft3) STO WATER RAG E D1 -D3 I 1 2 3.60 I 0.46 I 20,063 5/4/2018 10:48 PM Crestone Consultants, LLC Page 1 of 1 5!4i2018 11):53 PM DETENTION VOLUME BY THE MODIFIED FAA METHOD (See USDCM Volume 2 Storage Chapter for description of method) Project: MAKENA GAS PLANT Basin ID: BASINS Di -D3 (For catchments less than 160 acres only. For larger catchments, use hydrograph routing method) (NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended) Determination of MINOR Detention Volume Using Modified FAA Method Determination of MAJOR Detention Volume Using Modified FAA Method Design Information (Input): Design Information (Input): Catchment Drainage Imperviousness I. = 45.90 percent Catchment Drainage Imperviousness I. = 45.90 percent Catchment Drainage Area A = 23.60 acres Catchment Drainage Area A = 23.600 acres Predevelopment NRCS Soil Group Type = O A, B, C, or O Predevelopment NRCS Soil Group Type = D A, B, C, or D Return Period for Detention Control T = 10 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100) Time of Concentration of Watershed To = 28 i minutes Time of Concentration of Watershed Tc = 28 minutes Allowable Unit Release Rate q = 0,22 cis, acre Allowable Unit Release Rate q = 0.22 1cfstacre One -hour Precipitation Pi = 1.45 inches One -hour Precipitation Pi = 2.57 inches Design Rainfall IDF Formula I = C1` P1t(C2+TJ' C3 Design Rainfall IDF Formula I = C,' PII(C2+TG)^Cg Coefficient One C. = 28 50 Coefficient One C1 = 28.50 Coefficient Two C2 = 10 Coefficient Two O2 = 10 Coefficient Three C = 0.789 Coefficient Three O; = 0.789 Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated): Runoff Coefficient C = 0.44 Runoff Coefficient C = 0.59 InflowPeak Runoff (gyp -in = 24.18 cfs Inflow Peak Runoff Op -in = 57.46 cfs Allowable Peak Outflow Rate Qp-out = 5.2 cfs Allowable Peak Outflow Rate Qp-out = 5.2 cfs Mod. FAA Minor Storage Volume = 43,289 cubic feet Mod. FAA Major Storage Volume = 147,532 cubic feet Mod. FAA Minor Storage Volume = 0.99 acre -ft Mod. FAA Major Storage Volume = 3.39 acre -ft 10 c- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5 -Minutes) Rainfall Duration minutes (input) Rainfall Intensity inches 1 hr (output) Inflow Volume cubic feet (output) Adjustment Factor "m" (output) Average Outflow cfs (output) Outflow Volume cubic feet (output) Storage Volume cubic feet (output) Rainfall Duration minutes (input) Rainfall Intensity inches I hr (output) Inflow Volume cubic feet (output) Adjustment Factor "m" (output) Average Outflow cfs (output) Outflow Volume cubic feet (output) Storage Volume cubic feet (output) 15 3.26 30,468 1.00 5.19 4,673 25,795 15 5.78 72,412 1.00 5.19 4,673 67,739 25 2.50 38,940 1.00 5.19 7,788 31,152 25 4.43 92.547 1.00 5.19 7,788 84,759 35 2.05 44,711 0.90 4.70 9,860 34,851 35 3.63 106,262 0.90 4.70 9,860 96,402 45 1.75 49,068 0.81 4.23 11,417 37,650 45 3.10 116,616 0.81 4.23 11,417 105,199 55 1.53 52,566 0.76 3.93 12,975 39,591 55 2.72 124,930 0.76 3.93 1.2,975 111,955 65 1.37 55,491 0.72 3.73 14,532 40,958 65 2.43 131,881 0.72 3.73 14,532 117,349 75 1.24 58,007 0.69 3.58 16,090 41,91.7 75 2.20 137,861 0.69 3.58 16,090 121,771 85 1.14 60,218 0.67 3.46 17,648 42,570 85 2.02 143,116 0.67 3.46 17,648 125,468 95 1.05 62,192 0.65 3.37 19,205 42,987 95 1.86 147,808 0.65 3.37 19,205 128,603 105 0.98 63,978 0.63 3.30 20,763 43,215 105 1.73 152,052 0.63 3.30 20,763 131,289 115 0.92 65,609 0.62 3.23 22,320 43,289 115 1.62 155,930 0.62 3.23 22,320 133,609 125 0.86 67,113 0.61 3.18 23,878 43,235 125 1.53 159,503 0.61 3.18 23,878 135,625 135 0.81 68,508 0.60 3.14 25,436 43,073 135 1.44 162,820 0.60 3.14 25,436 137,384 145 0.77 69,811 0.60 3.10 26,993 42,818 145 1.37 165,916 0..60 3.10 26,993 138,923 155 0.74 71,034 0.59 3.07 28,551 42,483 155 1.30 168,822 0.59 3.07 28,551 140,272 165 0.70 72,186 0.59 3.04 30,108 42,078 165 1.24 171,562 0.59 3.04 30,108 141,453 175 0.67 73,277 0.58 3.02 31.,666 41,611 175 1.19 174,154 0.58 3.02 31,666 142,488 185 0.64 74,313 0.58 2.99 33,224 41,089 185 1.14 176,615 0.58 2.99 33,224 143,391 195 0.62 75,299 0.57 2.97 34,781 40,518 195 1.10 178,959 0.57 2.97 34,781 144,178 205 0.60 76,241 0.57 2.95 36,339 39,902 205 1.06 181,198 0.57 2.95 36,339 144,859 215 0.58 77,143 0.57 2.94 37,896 39,246 215 1.02 183,341 0.57 2.94 37,896 145,445 225 0.56 78,008 0.56 2.92 39,454 38,554 225 0.99 185,397 0.56 2.92 39,454 145,943 235 0.54 78,840 0.56 2.91 41,012 37,828 235 0.95 187,374 0.56 2.91 41,012 146,362 245 0.52 79,641 0.56 2.90 42,569 37,071 245 0.92 189,278 0.56 2.90 42,569 146,708 255 0.51 80,413 0.56 2.88 44,127 36,287 255 0.90 191,114 0.56 2.88 44,127 146,987 265 0.49 81,160 0.55 2.87 45,684 35,475 265 0.87 192,888 0.55 2.87 45,684 147,204 275 0.48 81,882 0.55 2.86 47,242 34,640 275 0.85 194,605 0.55 2.86 47,242 147,363 285 0.47 82,582 0.55 2.85 48,800 33,782 285 0.82 196,268 0.55 2.85 48,800 147,468 295 0.45 83,260 0.55 2.85 50,357 32,903 295 0.80 197,880 0.55 2.85 50,357 147,523 305 0.44 83,919 0.55 2.84 51,915 32,004 305 0.78 199,446 0.55 2.84 51,915 147,532 315 0.43 84,560 0.54 2.83 53,472 31,087 315 0.76 200,968 0.54 2.83 53,472 147,496 325 0.42 85,183 0.54 2.82 55,030 30,153 325 0.75 202,449 0.54 2.82 55,030 147,419 335 0.41 85,790 0.54 2.82 56,588 29,202 335 013 203,891 0.54 2.82 56,588 147,304 345 0.40 86.381 0.54 2.81 58,145 28,236 345 0.71 205,297 0.54 2.81 58,145 147,152 355 0.39 86.958 0.54 2.80 59,703 27,255 355 0.70 206,668 0.54 2.80 59.703 146,965 365 0.38 87,521 0.54 2.80 61,260 26,260 365 0.68 208,006 0.54 2.80 61,260 146,745 375 0.38 88,071 0.54 2.79 62,818 25,253 375 0.67 209,313 0.54 2.79 62,818 146,495 385 0.37 88,608 0.54 2..79 64,376 24,233 385 0.65 210,591 0.54 2.79 64,376 146215 395 0.36 89,134 0.54 2.78 65,933 23,201 395 0.64 211,840 0.54 2.78 65,933 145.907 405 0.36 89,649 0.53 2.78 67,491 22.158 405 0.63 213,063 0.53 2.78 67,491 145,572 415 0.35 90,153 0.53 2.77 69,048 21,104 415 0.62 214,261 0.53 2.77 69,048 145212 425 0.34 90,646 0.53 2.77 70,606 20,040 425 0.61 215,434 0.53 2.77 70,606 144,828 435 0.60 216,584 0.53 2.76 72,164 144,420 435 0.34 91,130 0.53 2.76 72,164 18,967 445 0.33 91,605 0.53 2..76 73,721 17,884 445 0.59 217,712 0.53 2.76 73,721 143,991 455 0.32 92,070 0.53 2.76 75,279 16,792 455 0.58 218,819 0.53 2.76 75,279 143,540 465 0.32 92,527 0.53 2.75 76,836 15,691 465 0.57 219,905 0.53 2.75 76,836 143,069 475 0.31 92,976 0.53 2.75 78,394 14,582 475 0.56 220,972 0.53 2.75 78.394 142,578 485 0.31 93,417 0.53 2.75 79,952 13,466 485 0.55 222,020 0.53 2.75 79,952 142,068 495 0.30 93,851 0.53 2.74 81,509 12,341 495 0.54 223,050 0.53 2.74 81.509 141,540 505 0.53 224,062 0.53 2..74 83,067 140,995 505 0.30 94,277 0.53 2..74 83,067 11,210 515 0.30 94.696 0.53 2.74 84,624 10,071 515 0.52 225,058 0.53 2.74 84,624 140,434 525 0.29 95,108 0.53 2.74 86,182 8,926 525 0.52 226,038 0.53 2.74 86,182 139,856 535 0.29 95,514 0.53 2.73 87,740 7,774 535 0.51 227,002 0.53 2.73 87,740 139263 545 0.28 95,913 0.53 2.73 89,297 6,616 545 0.50 227,952 0.53 2.73 89,297 138,654 555 0.28 96,306 0 53 2.73 90,855 5,452 555 0.49 228,886 0.53 2.73 90,855 138,032 565 0.27 96,694 0.53 2..73 92,412 4,282 565 0.49 229,807 0.53 2.73 92,412 137,395 575 0.27 97,076 0.52 2.72 93,970 3,106 575 0.48 230,715 0.52 2.72 93,970 136,745 585 0.27 97,452 0.52 2.72 95,528 1,924 585 0.47 231,609 0.52 2.72 95,528 136,081 595 0.26 97,823 0.52 2.72 97,085 738 595 0.47 232,491 0.52 2.72 97,085 135,405 605 0.26 98,189 0.52 2.72 98;643 -454 605 046 233,360 0.52 2.72 98,643 134,717 615 0.26 98.550 0.52 2,72 100,200 -1,651 615 046 234,217 0.52 2.72 100,200 134,017 Mod. FAA Minor Storage Volume (cubic ft.) = 43,289 Mod. FAA Major Storage Volume (cubic ft.) Mod. FAA Minor Storage Volume (acre -ft.) = 0.99 Mod. FAA. Major Storage Volume (acre -ft.) = UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.2, Released January2010 147,532 3.39 Creston Consultants, LLC Page 1a2 P'rysc. No. 't3C0 5!4•i2018 11):53 PM DETENTION VOLUME BY THE MODIFIED FAA METHOD (See US DCM Volume 2 Storage Chapter for description of method) Project: MAKENA GAS PLANT Basin ID: BASINS DI -D3 250,000 200,000 150,000 ci ci U 31oo,000 50,000 0 -50,000 Inflow and Outflow Volumes vs. Rainfall Duration • • • 00 O 00000000000ta.._, f JLs+,- - - 0000 00O 00 200 ' 400 500 600 7Q Duration (Minutes) - mirr-ctrcilr^Irv+VNunr mince Smrm°afa6t v chime o mines Storm Storage volume major Storm inn t:w volume ire Major Storm OULhow voitme • major Storm Storage volume 0 UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.2, Released January 2010 Crestorte Consultants, LLC Page 2 o' Project No. 18009 DETENTION POND VOLUME CALCULATIONS (11 Required WQCV = 100 Yr Detention Req'd Volume Makena Gas Plant Final Drainage Report 0.46 ac -ft 3.39 ac -ft From WOO/ Calculations From UDFCD Modified FAA Method Calculation (1) Per Weld County Code, WQCV included as a portion of the total 100 Yr required detention volume. POND VOLUME = 113(A1+A2+(A1*A2)A0.5)*D DETENTION POND INCREM CUM M. CU MM. ELEV AREA VOLUME VOLUME VOLUME SQ FT (ft3) (ft3) (ac -ft) (1)100 YR VOLUME WQCV 5007.42 0 0 0 0.00 5008.00 3,272 633 633 0.01 5009.00 22,088 11,287 11,920 0.27 5009.24 20,063 0.46 Freeboard 5010.00 46,715 33,642 45,561 1.05 5011.00 72,083 58,942 104,504 2.40 5012.00 86,533 79,198 183,702 4.22 Freeboard t 5013.00 97,137 91,784 275,486 6.32 Pond volumes based on Prismoidal Method calculations 05/4/2018 10:49 PM Crestone Consultants, LLC Page 1 of 1 Job No. 18009 Makena Gas Plant Final Drainage Report DETENTION POND RELEASE STRUCTURE BOX SIZING Orifice Equation- Area=Qr/ (0.65 * (2 * g * h)°5) Qr = Allowable release rate [cfs] g = 32.2 [ft2/s] h = Difference from water surface elevation to top of grate elevation [ft] WATER SURFACE *TOP GRATE OF 100-YR W.S. ELEV Qr no (cfs) HEAD Qr at (ft) AREA (ft2) REQ'D Release I 5009.24 5012.00 5.20 2.76 1 0.60 *Top of box grate elevation is set to WQCV Water Surface Elevation Weir Equation - Or = C * L* h3/2 Qr = Allowable release rate [cfs] c = Weir Coefficient, 3.33 used L = Length of Weir [ft] h = Difference from water surface elevation to top of grate elevation [ft] WATER SURFACE *TOP GRATE OF 100-YR W.S. ELEV Qr 100 (cfs) HEAD Qr at (ft) LENGTH (ft) REQ'D Release I 5009.24 5012.00 5.20 2.76 1 0.34 *Top of box grate elevation is set to WQCV Water Surface Elevation Release Structure Box - Try CDOT Type C Inlet Box Length = 2.92 ft Width = 2.92 ft Aope„ = 8.53 ft2 x 50% Clogging Factor = 4.27 ft2 Orifice Check- A►req'd = 0.60 ft2, Aopen = 4.27 ft2, therefore OK, CDOT Type C Inlet Box OK Weir Check- Lreq'd = 0.34 ft, L = 4*2.92 = 11.68 ft2, therefore, CDOT Type C Inlet Box OK 5/4/2018 10:50 PM Crestone Consultants, LLC Page 1 of 1 Pro,00: No. 1.099 STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET 11 Project: Makena Gas Plant Basin ID: Basins a1 -D3 WQCV Desiun Volume (Input): Catchment Imperviousness. is _ Catclime,rit Area, A = Depth at WWWQDV outlet above, lowest perforation, H = Vertical distance between rows, h _ 45.9 23.600 16 4.00 Number of rows, (AL = Orifice ctist.Tharge coefficient. C„ = Outlet Design Information (Output): a 65 percent acres inches inches Diameter of holes, D = Muml;tr of holes per row, N = Height of slot, H = Width of slot, W = Water Du al Qapture Volume (1 0 * (0.9'1 * I u - 1.19 * I''2 + 0.78 * I); 4'', OlCV = Water Dual it',f Capture Volume, 0A/QCCV) = Design Volume (WOO/ 112* Area " 1.2) Vol = Peuornrnenc1,c1 maximum outlet area per row r.l-ased on 4" vertical spacing of rows), Art = Total opening area at eacF`, row based on user -input above. A0 = Total opening area at each row based on user -input above. A0 = Calculation of Collection Capacity: OR 1.00 75 in in. Time to Drain the Pond = 40 hours. Water Quality Capture Volume Method Selected (40 - Hour Release) 0.20 watershed inches 0 36 acre-feet 0.►r acre-feet 4.79 square inches 4.75 square inches 0.033 square feet C C SIP Cfr a O O 0 4 O O O .71 01'71- 0 O 0 c C 0 0 Ci a I I 0 Per(nrai!c d Piufci Era nip/ r' s Stage ft (input) Central Elevations of Rows of Holes in feet 1- Flow Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Pow 7 Row S Pow ? Row 10 R. ow 11 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 5007.50 5007.63 5008.17 5003.50 Collection Capacity for Each Row of Holes in cis 5007.50 0.000 0.000 0.000 0.000 0.00 3007.83 0.099 0.000 0.000 0.000 0.10 5008.16 0.140 0.099 0.000 0.000 0.24 5008.49 0.171 0.140 0.097 0.000 0.41 5008±2 0.198 0.171 0.139 0.097 0.60 5009.15 0.221 0.196 0.170 0.139 0.73 3009.48 0.242 0.221 0.197 0.170 0.83 3009.81 0.262 0.242 0.220 0.197 0.92 5010.14 0.260 0.262 0.242 0.220 1.00 3010.47 0.297 0.260 0.261 0.242 1.08 5010.80 0.313 0.297 0.279 0.261 1.15 301-1.13 0.328 0.313 0.296 0.279 9 1.22 5011.46 0.342 0.326 0.312 0.296 1.28 f.3011 .7 0.356 0.342 0.327 U. 12 1.34 3012.00 0.365 0.351 0.337 0.322 1.37 #NIA #N?A #NIA #NIA #N(A #NIA #NIA #NIA #NIA #N(A #NIA #NIA #N/A #N1rA #N(A #NIA #tN/A MN/A #NrA #N(A MN/A #NrA #N!A #NrA #N(A #N/A #NrA #NrA #NrA #N(A #NrA #N/A #N(A. #NIA #N(A #NrA #NrA #NIA #NIA #N/A #NIA #NIA #NIA #NIA #N/A #NIA #NIA #NIA #NIA #NiA MN/A #NIA #NIA #NIA #N/A MN/A #NIA #NIA #NIA #N/A #NIA #NI"A #N/A #NJIA #NIA #NIA #NIA #NIA #NIA #NiA #NIA #NIA #INIA #NJIA #N/A #NrA #NrA #NrA #N/'A #N(A #NrA #NIA #N/A #NrA #NIA #NIA #N/A #N/A #N/A *NIA #NrA #N(A #N/A #N/A #NIA #N/A #N/A #NrA. #NrA #NIA #NrA #N?A #N/A #NIA #NIA #N1A #NrA #NrA #NrA #NIA #NrA #N.IA #NrA #N/A #NIA UN/A UN/A #NrA UN/A #NIA #NrA. UN/A #N.rA #NrA #NIA UN/A UN/A UN/A UN/A #NIA UN/A #N/A #N./A #N.rA #NIA UN/A #NrA Pt NIA UN/A #NIA #NIA #N'A #NIA #NlA #N(A 5/4/2018 1056 PM Cres:ono Gansu :an:s. L LC F J•_C 1 Cr 5/4/2018 Pro,ec: Na. 18009 STAGE -DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET Project: Makena Gas Plant Basin ID: Basins D1 -D3 Stage (feet, elev.) 6085.50 -- 5085.50 4085.50 3085.50 2085.50 1085.50 STAGE -DISCHARGE CURVE FOR THE WQCV OUTLET STRUCTURE • • 4 s i ♦ ♦ 85.50 0.00 0.20 0.40 0.60 0.80 Discharge (cfs) 1.00 1.20 1.40 1.60 I 14.56 PM Cres:anc Consu :an:s. L LC Page 2o: 2 Culvert Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Detention Pond Outfall Pipe (Capacity) Invert Elev Dn (ft) Pipe Length (It) Slope (%) Invert Elev Up (ft) Rise (in) Shape Span (in) No. Barrels n -Value Culvert Type Culvert Entrance Coeff. K,M,c,Y,k Embankment Top Elevation (ft) Top Width (ft) Crest Width (ft) Elev (ft)• 5.013.00 5012.00 &010.00 5009_{x} 5008.00 5007.00 5006.00 5005.00 = 5006.87 60.00 0.50 5007.17 12.0 Circular 12.0 1 0.016 Circular Concrete Square edge w/headwall (C) 0.0098, 2, 0.0398, 0.67, 0.5 = 5012.00 = 15.00 = 60.00 Detention Pond Outfall Pipe (Capacity) Calculations Qmin (cfs) Qmax (cfs) Tailwater Elev (ft) Highlighted Qtotal (cfs) Qpipe (cfs) Qovertop (cfs) Veloc Dn (ftls) Veloc Up (ft/s) HGL Dn (ft) HGL Up (ft) Hw Elev (ft) Hw/D (ft) Flow Regime Friday, May 4 2018 6.10 6.10 Crown 6.10 6.10 0.00 7.77 7.77 5007.87 5010.54 5011.94 4.77 Outlet Control Km Depth (It) nu del coni of A C IA 1 F 11A ?R VI q.k An Ac RR N ei5 '7c RA Circular Duly erl HGL Ernban k Reach (ft) 5.83 4_"a3 3.83 2.83 1.83 x+_83 -0.17 -1.17 -2.17 T C co 2 LO LU C) Project No. 18009 U) w U- 0 J U I- lx W J e lx O U C z N tO w F- J 0 re O F- C) lx I w lx C 0- its O its 2 Basins D-1 -D3 0 0 0 © 0 I O o F- C 0 0 0 0 4- 4- U) tO 0 4ral — U •— #2 Vertical Orifice #1 Vertical Orifice C7 csj N.- Q 5,007.17 O • ' O � is- co 0' Is C C, Orifices or Pi II II II II II C01-2 o •s 0 col 5 a 0 0, .55 0 I w 0 w L CU w 0) Fr. Co as Design Depth CU i 2 I ors U) V 0) . Lt I C 03 4} E I- 0 ats 4, 3 C, U as C.) O U- co c's ci cej CO CO 0 F - C) c i n 4 2 LL = LL. •0 O U 0 4, .L O tQ U 03 CT is_ co e - C 4- 4, 4- 4 co inis's.t L ietac3.1416) V 0) 4) 0 II II II <c. F- > 4) -'S CO C W ) O 0 O) 4- 4111 LL E O C on CD C (72 4 - W +}i O O W C .0 C C, 4, 0 .2' 0 •ice v C11�� 2 I- 0 sha 1121 as C, 0. W Li co II II C) L 0 0 4-a Cu 4) ft cr 4- 15 U E a co 0) L co 03 W t 0 05 2' O U) co C- 0 J C CO Can O U.) C CD Clips Weir Report Hydraflow Express Extension for Autodesk® AutoCADO Civil 3D® by ALitodesk, Inc. Detention Pond - EM Overflow Trapezoidal Weir Crest Bottom Length (ft) Total Depth (ft) Side Slope (z:1) Calculations Weir Coeff. Cw Compute by: Known 0 (cfs) Depth (ft) 2.00 1.50 1.00 0.50 0.00 -0.50 Sharp 60.00 1.00 4.00 3.10 Known Q _ 66.30 Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s) Top Width (ft) Detention Pond - EM Overflow Friday, May 4 2018 = 0.50 _ 66.30 _ 1.00 _ 2.14 64.00 Depth (ft) 10 Weir 15 20 25 W.S. 30 35 40 45 50 55 60 65 70 75 80 2.00 1.50 1.00 0.50 0.00 0.50 Length (ft) Hydraulic Calculation Reference Materials 5.7 MAJOR DRAINAGE This section presents concise, practical guidelines for the design of major drainage systems. For more information regarding the design of major drainage systems, refer to Chapter 8 of the Weld County Code and the major drainage chapter of the UDFCD Manual (Volume 1). s.7.1 Design Flows The major drainage system must be able to convey the fully developed flow from a watershed for the 100 -year event without significant damage to the system. 5.7.2 Design Criteria Table 5-9 summarizes the general design guidelines for channels. More information and design examples are provided in Chapter 8 of the Weld County Code and the major drainage chapter of the UDFCD Manual (Volume 1). Table 5-9 Channel Lining Criteria Design Item Criteria for Various Types of Channel Lining Grass: Erosive Soils Grass: Erosion Resistant Soils Concrete Riprap Maximum 100-yr velocity 5.0 ft/sec 5.0 ft/sec 16.0 ft/sec 18.0 ft/sec Minimum Manning's check n — stability 0.020 0.020 0.03 0.011 Maximum Manning's check n- capacity 0.035 0.035 0.04 0.013 Maximum Froude number 0.5 0.8 0.8 N/A Maximum flow depth outside zone low- 5.0 ft 5.0 ft N/A N/A Maximum channel slope longitudinal 0.6% 0.6% 1.0% N/A Maximum side slope& 4H:1V 4H:1V 2.5H:1V 1.5H:1V1 Minimum centerline bend radius for a 2 x top width 2 x top width 2 x top I width 2 x top _ width Minimumfreeboard2 1.0ft315 ..oft315 2..0ft3 2.0 ft4 Portions of this table were obtained from Table MD -1, UDFCD Manual (Volume 1), Table MD -2 1 Side slopes may be steeper if designed as a structurally reinforced wall to withstand soil and groundwater forces. 2 Add superelevation to the normal water surface to set freeboard at bends. 3 Suggested freeboard is 2.0 feet to the lowest adjacent habitable structure's lowest floor. 4 For super critical channels, use the freeboard recommended in the major drainage chapter of the UDFCD Manual (Volume 11 Section 4.3.1.5. 5 Grass -lined open channels conveying less than 50 cfs may reduce the minimum 1.0 foot freeboard requirement to the freeboard required to convey 1.33 times the 100 -year design flow. The reduced freeboard may only occur if a 1.0 -ft minimum freeboard is not physically possible and a variance request is submitted. 6 Maximum side slopes may be as steep as 3H:1V; however, the design engineer should address how the channels will be maintained since it may not be safe to mow on slopes that are greater than 4H:1V. The developer/engineer is encouraged to use the spreadsheets and programs provided by the UDFCD to assist in designing major drainage. Other software programs may be used, but the designs will be WELD COUNTY ENGINEERING & CONSTRUCTION CRITERIA Page 144 Hydraulic Structures Chapter 3.2.1 Riprap Apron This section addresses the use of riprap for erosion protection downstream of conduit and culvert outlets. Refer to the Open Channels chapter for additional information on applications for and placement of riprap. Those criteria will be useful in design of erosion protection for conduit outlets. When incorporating a drop into the outfall use Figure 9-40 or 9-41. Rock Size The procedure for determining the required riprap size downstream of a conduit outlet is in Section 3.2.3. Configuration of Riprap Apron Figure 9-34 illustrates typical riprap protection of culverts at conduit outlets. Extent of Protection The length of the riprap protection downstream from the outlet depends on the degree of protection desired. If it is necessary to prevent all erosion, the riprap must extend until the velocity decreases to an acceptable value. The acceptable major event velocity is set at 5 ft/sec for non -cohesive soils and at 7 ft/sec for erosion resistant soils. The rate at which the velocity of a jet from a conduit outlet decreases is not well known. The procedure recommended here assumes the rate of decrease in velocity is related to the angle of lateral expansion, 0, of the jet. The velocity is related to the expansion factor, (1/(2tanO)), which can be determined directly using Figure 9-35 or Figure 9-36, by assuming that the expanding jet has a rectangular shape: ( 1 v At 2 tan 0 AY, w I Where: L , = length of protection (ft) W — width of the conduit (ft, use diameter for circular conduits) Yt = tailwater depth (ft) 0 = the expansion angle of the culvert flow and: where: design discharge (cfs) V = the allowable non -eroding velocity in the downstream channel (ft/sec) t = required area of flow at allowable velocity (ft2) Equation 9-11 Equation 9-12 9-66 Urban Drainage and Flood Control District September 2017 Urban Storm Drainage Criteria Manual Volume 2 Chapter 9 Hydraulic Structures In certain circumstances, Equation -11 may yield unreasonable results. Therefore, in no case should Lp be less than 3H or 3D, nor does Lp need to be greater than 10H or 10D whenever the Froude parameter, 0/1/VW's or O D2'5, is less than 8.0 or 6.0, respectively. Whenever the Froude parameter is greater than these maximums, increase the maximum Lp required by 34 Dir or H for circular or rectangular (box) culverts, respectively, for each whole number by which the Fronde parameter is greater than 8.0 or 6.0, respectively. Once Li, has been determined, the width of the riprap protection at the furthest downstream point should be verified. This dimension is labeled "T" on Figure 9-34. The first step is to solve for using the results from Figure 9-35 or 9-36: 0 = tan I( 1 2(ExpansionFactor)) Equation 9-13 Where: Expansion Factor = determined using Figure 9-35 or 9-36 T is then calculated using the following equation: T = 2 (L,7 tan 0) + Equation 9-14 Multiple Conduit Installations The procedures outlined in this section can be used to design outlet erosion protection for multi -barrel culvert installations by replacing the multiple barrels with a single hydraulically equivalent hypothetical rectangular conduit. The dimensions of the equivalent conduit may be established as follows: 1. Distribute the total discharge, Q, among the individual conduits. Where all the conduits are hydraulically similar and identically situated, the flow can be assunned to be equally distributed; otherwise, the flow through each barrel must be computed. 2. Compute the Froude parameter Q1/D25 (circular conduit) or Q1/WH115 (rectangular conduit), 'where the subscript i indicates the discharge and dimensions associated with an individual conduit. 3. If the installation includes dissimilar conduits, select the conduit with the largest value of the Froude parameter to determine the dimensions of the equivalent conduit. 4. Make the height of the equivalent conduit, Het,, equal to the height, or diameter, of the selected individual conduit. 5. The width of the equivalent conduit, Weil, is determined by equating the Froude parameter from the selected individual conduit with the Froude parameter associated with the equivalent conduit, September 2017 Urban Drainage and Flood Control District 9-67 Urban Storm Drainage criteria Manual Volume 2 Hydraulic Structures Chapter EXTEND RIPRAP TO HEIGI—IT OF PIPE OR 6OXc MIN, RIPRAP MORE THAN 1,0' ABOVE PIPE INVERT SHALL RE INSTALLED 6M BELOW FINISHED GRADE AND BURIED WITH TOPSOIL FIN A SHED GRACE • r" ti: �--- 05 I pre s, cri. lr PLAN VIEW NITS END TREATMENT MAY CONSIST OF RCP END SECTION' (WITH TOEWALL) O HEADWALL, (SEE DETAILS) JDIN1T F 2D50 MIN — RESTRAINTS (2) L PROFILE INS SOIL RIPRAP OR VOID —FILLED RIPRAP O OS Figure 9-34. Riprap apron detail for culverts in -line with the channel 9-68 Urban Drainage and Flood Control District September 2017 Urban Storm Drainage Criteria Manual Volume 2 Chapter 9 Hydraulic Structures Expansion Angle N cig cr 0 1- 0 EXPANSION 6 5 2 11 1 rdere 1 2 .3 .4 .5 .6 .7 TAILWATER DEPTH/ CONDUIT HEIGHT, 1 / 0 Figure 9-35. Expansion factor for circular conduits 8 September 2017 Urban Drainage and Flood Control District 9-69 Urban Storm Drainage criteria Manual Volume 2 Hydraulic Structures Chapter 9 ewe 6 e C Q 045 at P 2 a a �.t X w $ = Expansion Angle .2 .3 .4 .5 .6 . .8 TAILWATER DEPTH/ CONDUIT HEIGHT= Yt /H Figure 9-36. Expansion factor for rectangular conduits 1O 9-70 Urban Drainage and Flood Control District September 2017 Urban Storm Drainage Criteria Manual Volume 2 Chapter 9 Hydraulic Structures 3.2.2 Low Tailwater Basin The design of low tailwater riprap basins is necessary when the receiving channel may have little or no flow or tailwatcr at time when the pipe or culvert is in operation. Figure 9-37 provides a plan and profile view of a typical low tailwater riprap basin. By providing a low tailwater basin at the end of a storm drain conduit or culvert, the kinetic energy of the discharge dissipates under controlled conditions without causing scour at the channel bottom. Low tailwater is defined as being equal to or less than !; of the height of the storm drain, that is: yt - yl - or 3 Where: yt = tailwater depth at design flow (feet) D = diameter of circular pipe (feet) H height of rectangular pipe (feet) Rock Size The procedure for determining the required riprap size downstream of a conduit outlet is in Section 3.23. After selecting the riprap size, the minimum thickness of the riprap layer, T, in feet, in the basin is defined as: T =2 D50 Equation 9-15 Basin Geometry Figure 9-37 includes a layout of a standard low tailwatcr riprap basin with the geometry parameters provided. The minimum length of the basin (L) and the width of the bottom of the basin (Wi) are provided in a table at the bottom of Figure 9-37. All slopes in the low tailwater basin shall be 3 (H): 1(v), minimum. Other Design Requirements Extend riprap up the outlet embankment slope to the mid -pipe level, minimum. It is recommended that riprap that extends more than 1 foot above the outlet pipe invert be installed 6 inches below finished grade and buried with topsoil. Provide pipe end treatment in the form of a pipe headwall or a flared -end section headwall. See Section 3.1 for options. September 2017 Urban Drainage and Flood Control District 9-71 Urban Storm Drainage criteria Manual Volume 2 Hydraulic Structures Chapter R I P FLAP MORE THAN ABDVE PIPE INVERT SHALL BE INSTALLED 6" BELOW FINISHED GRADE AND BURIED WITH TOPSOIL FINISHED GRADE MEM JOINT RESTRAINTS (2) RCP WITH FES SHOWN END TREATMENT MAY CONSIST OF PIPE HEADWALL OR FES HE/CD/ALL L FES H EADWALL SHOWN ui _ PROFILE j • 00 I - FINISHED GRADE D SEE TABLE — SOIL RIPRAP OR T=2D50 MIN VOID —FILLED RIPRAP PIPE SIZE OR D W* L BOX HEVGHT 18'; — 24YI 1f_n 4'. 15' 30" — 36" 1r-6" 6' 20' 42" — 48" 2' —On 7' 24' 54" — 50" 2' —6" 81. 28' 88" - 72?? 3'—O s 9' 32' * IF OUTLET PIPE IS A EGX CULVERT WITH A WIDTH GREATER THAN W, THEN W = CULVERT WIDTH Figure 9-37. Low tailw ater riprap basin 9-72 Urban Drainage and Flood Control District September 2017 Urban Storm Drainage Criteria Manual Volume 2 Chapter 9 Hydraulic Structures 3.2.3 Rock Sizing for Riprap Apron and Low Tailwater Basin Scour resulting from highly turbulent, rapidly decelerating flow is a common problem at conduit outlets. The following section summarizes the method for sizing riprap protection for both riprap aprons (Section 3.2.1) and low tailwater basins (Section 3.2.2). Use Figure 9-38 to determine the required rock size for circular conduits d Figure 9-39 for rectangular conduits. Figure 9-38 is valid for Q/D25 of 6.0 or less and Figure 9-39 is valid for Q/WH1'5 of 8.0 or less. The parameters in these two figures are: 1. Q/DL5 or Q/WHas in which Q is the design discharge in cfs, Dc is the diameter of a circular conduit in feet, and W and H are the width and height of a rectangular conduit in feet. 2. Yt/DC or 11/H in which Y, is the tailwater depth in feet, a, is the diameter of a circular conduit in feet, and H is the height of a rectangular conduit in feet. In cases where Yt is unknown or a hydraulic jump is suspected downstream of the outlet, use Yt/Dt = Yt/H = 0.40 when using Figures 9-38 and 9-39. 3. The riprap size requirements in Figures 9-38 and 9-39 are based on the non -dimensional parametric Equations 9-16 and 9-17 (Steven, Simons, and Watts 1971 and Smith 1975). Circular culvert: 5 0.023Q y 1.2 D °. t Rectangular culvert: 0.014H 0.5Q d so = Ytw Equation 9-16 Equation 9-17 These rock size requirements assume that the flow in the culvert is subcritical. It is possible to use Equations 9-16 and 9-17 when the flow in the culvert is supercritical (and less than full) if the value of De or H is modified for use in Figures 9-38 and 9-39. Note that rock sizes referenced in these figures are defined in the Open Channels chapter. Whenever the flow is supercritical in the culvert, substitute Da for a and Ha for H, in which Da i.s defined as: Da (D, + Y„ 2 Where the maximum value of Da shall not exceed DL, and Equation 9-18 September 2017 Urban Drainage and Flood Control District 9-73 Urban Storm Drainage criteria Manual Volume 2 Hydraulic Structures Chapter Ha +y,, 2 Where the maximum value of Ha shall not exceed H, and: r C 0 Da Equation 9-19 parameter to use in place of D in Figure 9-38 Then flow is supercritical (ft) D, = diameter of circular culvert (ft) H„ = parameter to use in place of H in Figure 9-39 when flow is supercritical Ut) H = height of rectangular culvert (ft) n = normal depth of supercritical flow in the culvert (ft) 60 40 20 I a p Ilk 4, .4se OA" G ihas.-A.cl I ' rePe * -)le , .8 Y t / D Use Da instead of Di whenever flow is supercritical in the barrel. **Use Type L for a distance of 3D doownstrear a 1.0 Figure 9-38. Riprap erosion protection at circular conduit outlet (valid for Q/D2.5 ≤ 6.0) 9-74 Urban Drainage and Flood Control District September 2017 Urban Storm Drainage Criteria Manual Volume 2 Chapter 9 Hydraulic Structures 6O 40 r 3 a o0 kit I lh f F kf 4 Crte SA, ci- .#1*.As;? .4 Vt/H 6 10 Use Ha instead of H whenever culvert has supercritical flow in the barrel. **Use Type L for a distance of 3H downstream Figure 9-39. Riprap erosion protection at rectangular conduit outlet (valid for Q/WH1.5 8.0) 3.2.4 Outfalls and Rundowns A grouted boulder outfall or "rundown" dissipates energy and provides erosion control protection. Grouted boulder outfalls are most commonly used in large rivers like the South Platte. Figure 9-40 provides a plan view and cross section for a standard grouted boulder rundown. See the grouted boulder drop profiles (Al, A2, and A3) in Figure 9-12 for site specific profile options, (i.e., depressed or free - draining basin for use with a stable downstream channel or with no basin for use in channels subject to degradation) . Figure 9-41 provides a plan view of the same structure for use when the structure is in -line with the channel. Evaluate the following when designing a grouted boulder outfall or rundown: ■ Minimize disturbance to channel bank • Determine water surface elevation in receiving channel for base flow and design storm(s) • Determine flow rate, velocity, depth, etc. of flow exiting the outfall pipe for the design storm(s) • Evaluate permitting procedures and requirements for construction adjacent to large river system. September 2017 Urban Drainage and Flood Control District 9-75 Urban Storm Drainage Criteria Manual Volume 2 EM 1110-2-1601 1 July 1991 US Army Corps of Engineers ENGINEERING AND DESIGN Hydraulic Design of Flood Control Channels ENGINEER MANUAL EM 1110-2-1601 Change 1 30 Jun 94 * attack in braided streams is thought to occur when the water surface is at or slightly above the tops of the mid - channel bars. At this stage, flow is confined to the multi- ple channels that often flow into or "impinge" against bank lines or levees. At lesser flows, the depths and velocities in the multiple channels are decreased. At higher flows, the channel area increases drastically and streamlines are in a more downstream direction rather than into bank lines or levees. (b) The discharge that produces a stage near the tops of the midchannel bars is!trncbt Qt his probably highly correlated with the channel -forming discharge concept. In the case of the Snake River near Jackson, Wyoming, talc}, is 15,00018,000 cfs, which has an average recurrence interval of about 2-5 years. Using cross-section data to determine the channel area below the tops of the midchannel bars and Otine') allows determina- tion of the average channel velocity at the top of the midchannel bars, Vanch (c) Field measurements at impingement sites were taken in 1991 on the Snake River near Jackson, Wyoming, and reported in Maynord (1993). The maxi- mum observed ratio Vss/Vt,r,,t, = 1.6 , which is almost identical to the ratio shown in Plate 33 for sharp bend - ways having RAY = 2 in natural channels, and this ratio is recommended for determining Vss for impinged flow. The second area of the design procedure requiring modifi- cation for impinged flow is the velocity distribution coef- ficient Cv , which varies with R1W in bendways as shown in Plate 40. Impinged flow areas are poorly aligned bends having low RAW and Cv = 1.25 is recommended for design. (6) Transitions in size or shape may also require riprap protection. The procedures in this paragraph are applicable to gradual transitions where flow remains tran- quil. In areas where flow changes from tranquil to rapid andthen back to tranquil, riprap sizing methods applicable to hydraulic structures (HD(HDC 712-1) should be used. In converging transitions, the procedures based on Equa- tion 3-3 can be used unaltered. In expanding transitions, flow can concentrate on one side of the expansion and design velocities should be increased_. For installations. immediately downstream of concrete channels, a vertical velocity distribution coefficient of 1.25 should be used due to the difference in velocity profile over the two surfaces. 3) Steep slope riprap design. In cases where unit discharge is low, riprap can be used on steep slopes ranging from 2 to 20 percent. A typical application is a rock -lined chute. The stone size equation is 1.95 S°."5 q 213 D30 — t/3 g where = slope of bed q = unit. discharge (3-5) Equation 3-5 is applicable to thickness = 1.5 D100, angular rock, unitweight of 167 pcf, D85/D15 from 1.7 to 2.7, slopes from 2 to 20 percent, and uniform flow on a down - slope with no tailwater. The following steps should be used in application of Equation 3-5: (1) Estimate q = Q/b where b = bottom width of chute. (2) Multiply q by flow concentration factor of 1.25. Use greater factor if approach flow is skewed. (3) Compute D30 using Equation 3-5. (4) Use uniform gradation having D 85/D15 ≤,2 such as Table 3-1. (5) Restrict application to straight channels with side slope of 1V:2.5H or flatter. (6) Use filter fabric beneath rock. The guidance for steep slope riprap generally results in large riprap sizes. Grouted riprap is often used instead of loose riprap in steep slope applications. 3-8. Revetment Top and End Protection Revetment lop and end protection requirements, as with all channel protective measures, are to assure the project benefits, to perform satisfactorily throughout the project economic life,, and not to exceed reasonable maintenance 3-8 Open Channels Chapter 8 CHANNEL BED FLOW DESIGN WSE RIPRAP OR SOIL RIPRAP NOT STEEPER THAN 2.5H:1 V \fc*\,,, 3' MIN (5 MIN FOR SOILS THAT ARE NOT COHESIVE) ' r \\/\s/1 x\o/ \\// ,e(\\sc \\,/,/,(//x //,><>Mitx\i\\\t ).); .\-gsstC./</e111./1"\\ zei\A\A\N> k \\As \\././ GRANULAR BEDDING, REQUITED FOR RIPRAP. ALSO REQUIRED FOR SOIL RIPRAP WHEN SPECIFICIED RPRAP DESICNA I ION SMALLER GIVEN WEIGHT SITE THAN HY INTERM I EDIATE E I' I I ROCK HE D50* (INCHES) 70 — C01 12 TYPE VI_50 35 70 50 9 6 — 2 - 10 2 70 — 100 15 TYPE 50 55 — 70 50 12 9 — 2 — 1e 3 70 — 100 21 TYPE E kd1 5D 35 '0 — 50 1 8 12 12 — 10 4 70 — 1Ca 30 TYRE H 50 35 — 70 — 50 24 18 18 — 1G *D50 MEAN ROCK SIZE = Figure 8-34. Riprap and soil riprap placement and gradation (part 1 of 3) 8-76 Urban Drainage and Flood Control District January 2016 Urban Storm Drainage Criteria Manual Volume 1 Chapter 8 Open Channels SOIL RIPRAP NOTES: 1. ELEVATION TOLERANCES FOR THE SOIL RIPRAP SHALL BE a 1 FEET. THICKNESS OF SOIL RIPRAP SHALL BE NO LESS THAN THICKNESS SHOWN AND NO MORE THAN 2 —INCHES GREATER THAN THE THICKNESS SHOWN. WHERE "SOIL RIPRAP" IS DESIGNATED ON THE CONTRACT DRAWINGS, RIP RAP VOIDS ARE TO BE FILLED WITH NATIVE SOIL THE RIPRAP SHALL BE PRE —MIXED WITH THE NATIVE SOIL AT THE FOLLOWING PROPORTIONS BY VOLUME SSPERCENT RIPRAP AND 35 PERCENT SOIL, THE SOIL USED FOR MIXING SHALL BE NATIVE TOPSOIL AND SHALL HAVE A MINIMUM FINES CONTENT OF 15 PERCENT. THE SOIL RIPRAP SHALL BE INSTALLED IN A MANNER THAT RESULTS IN A DENSE, INTERLOCKED LAYER OF RIPRAP WITH RIPRAP VOIDS FILLED COMPLETELY WITH SOIL. SEGREGATION OF MATERIALS SHALL BE AVOIDED AND IN NO CASE SHALL THE COMBINED MATERIAL CONSIST PRIMARILY OF SOIL; THE DENSITY AND INTERLOCKING NATURE OF RIPRAP IN THE MIXED MATERIAL SHALL ESSENTIALLY BE THE SAME AS IF THE RIPRAP WAS PLACED WITHOUT SOIL WHERE SPECIFIED (TYPICALLY AS 'BURIED SOIL RIPRAP"), A SURFACE LAYER OF TOPSOIL SHALL BE PLACED OVER THE SOIL RIPRAP ACCORDING TO THE THICKNESS SPECIFIED ON THE CONTRACT DRAWINGS. THE TOPSOIL SURFACE LAYER SHALL BE COMPACTED TO APPROXIMATELY 85% OF MAXIMUM DENSITY AND WITHIN TWO PERCENTAGE POINTS OF OPTIMUM MOISTURE IN ACCORDANCE WITH ASTM D698. TOPSOIL SHALL BE ADDED TO ANY AREAS THAT SETTLE. ALL SOIL RIPRAP THAT IS BURIED WITH TOPSOIL SHALL BE REVIEWED AND APPROVED BY THE ENGINEER PRIOR TO ANY TOPSOIL PLACEMENT. GRADATION FOR GRANULAR BEDDING G.S. STANDARD SIEVE SIZE PERCENT PASSING BY WEIGHT TYPE I COOT SECT. 703.01 TYPE II COOT SECT.. 703.09 CLASS A 3 INCHES - 90 - 100 12 INCHES - - 34 INCHES - 20 - 90 % INCHES 100 - 4 95 - 100 0 - 20 #16 45 - 80 - #50 1 G - 30 - 1 DG 2 - 10 - #200 G — 2 0 — 3 RIPRAP BEDDING Figure 8-34. Riprap and soil riprap placement and gradation (part 2 of 3) January 2016 Urban Drainage and Flood Control District 8-77 Urban Storm Drainage Criteria Manual Volume 1 Open Channels Chapter 8 THICKNESS REQUIREMENTS FOR GRANULAR BEDDING RIPRAP DESIGNATION MINIMUM BEDDING THICKNESS (INCHES) FINE-GRAINED SOILS 1 COARSE -GRAINED SOILS 2 TYPE I (LOWER LAYER) TYPE II (UPPER LAYER) TYPE II VL (D50 = 6 I N) 4 4 6 L (D50 = 9 IN) 4 4 6 M (D50 = 12 IN) 4 4 6 H (D50 = 18 IN) 4 6 8 VH (D50 = 24 IN) 4 6 8 NOTES: 1. MAY SUBSTITUTE ONE 12 -INCH LAYER OF TYPE II BEDDING. THE SUBSTITUTION OF ONE LAYER OF TYPE II BEDDING SHALL NOT BE PERMIITTED AT DROP STRUCTURES. THE USE OF A COMBINATION OF FILTER FABRIC AND TYPE II BEDDING AT DROP STRUCTURES IS ACCEPTABLE, 2. FIFTY PERCENT OR MORE BY WEIGHT RETAINED ON THE #40 SIEVE. Figure 8-34. Riprap and soil riprap placement and gradation (part 3 of 3) 8-78 Urban Drainage and Flood Control District January 2016 Urban Storm Drainage Criteria Manual Volume 1 Chapter 3 Calculating the WQCV and Volume Reduction 3.0 Calculation of the WQCV The first step in estimating the magnitude of runoff fro . a site is to estimate the site's total imperviousness. The total imperviousness of a site is the weighted average of individual areas of like imperviousness. For instance, according to Table RO-3 in the Runoff chapter of Volume 1 of this manual, paved streets (and parking lots) have an imperviousness of 100%; drives, walks and roofs have an imperviousness of 90%; and lawn areas have an imperviousness of 0%. The total imperviousness of a site can be determined taking an area -weighted average of all of the impervious and pervious areas. When measures are implemented minimize directly connected impervious area (MD I ), the imperviousness used to calculate the WQCV is the "effective imperviousness." Sections 4 and 5 of this chapter provide guidance and examples for calculating effective imperviousness and adjusting the WQCV to reflect decreases in effective imperviousness. The WQCV is calculated as a function of imperviousness and BMP drain time using Equation 3-1, and as shown in Figure 3-2: WQCV = a(0.91I3 - 1.19/2 + 0.78/) Equation 3-1 Where: WQCV I Water Quality Capture Vol i e (watershed inches) = Coefficient corresponding to WQCV drain 1 . e (Table 3-2) Imperviousness (%/100) (see Figures 3-3 through 3-5 [single family land use] and nor the Runoff chapter of Volume 1 [other typical land uses]) Table 3-2. Drain Time Coefficients for WQCV Calculations Coefficient, a Drain Time (hrs) hours D . 8 `12 2 1 hours 0.9 40 hours 1.0 Figure 3-2, which illustrates the relationship between imperviousness and WQCV for various drain times, is appropriate for use in Colorado's high plains near the foothills. For other portions of Colorado or United States, the WQCV obtained from this figure can be adjusted using the following relationships: Q Vother Where: WQCV WQC other tl� rWQCV d6 L 4.43 Equation 3-2 WQCV calculated using Equation 3-1 or Figure 3-2 (watershed inches) WQCV outside of Denver region (watershed inches) depth of average runoff producing storm from Figure 3-1 (watershed inches) August 2011 Urban ainage and Flood Control District 3-5 Urban Storm Drainage Criteria Manual Volume 3 Calculating the WQCV and Volume Reduction Chapter 3 Once the WQCV in watershed inches is found from Figure 3-2 or using Equation 3-1 and/or 3-2, the required BMP storage volume in acre-feet can be calculated as follows: WQCV V=( 12 )A Where: V = required storage volume (acre -if) A = tributary catchment area upstream (acres) WQCV = Water Quality Capture Volume (watershed inches) 0.500 0.450 a40 0 inc 0.350 a) am) 0.250 Ct a20 0 0.150 O 0.100 0.050 0.000 Equation 3-3 I I 40 hour drain time de de de de j24 hour drain time WQC V I (O.91 1.19 +0.78 I 0 12 24 -hr -hr drain drain time a = 0.8 time a = 0.9 de -s -` 40 -hr drain time a = 1.0 dor ,,r•+� el. No doll ai'm doe .00 le 401 12 hour drain time I di.IS+'' 004. die 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Total Imperviousness Ratio (i = la/100) Figure 3-2. Water Quality Capture Volume (WQCV) Based on BMP Drain Time 3-6 Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual Volume 3 August 2011 APPENDIX D Maps Historic Drainage Exhibit Developed Drainage Exhibit Drainage Details \ \ ' 5 ` k \ �,\,\ 4~ .,\`_�� -� / ^ r 1 t, 1,4 1 1 I S \f ) �\ \�1\ \,lt/ 1I I , r J_-4 4 ti. t \--•,'7 ;c\ \,. .\ \, \+ L \ \ \ ••---4.-\•••• 4\ 44 rf _ ) —4-4 / ' r AAA / 4 T / 1 _ _ '5 4. ~ ! \�• \\ 1 \• ,\\ / i• --- \fly, ^� \\ ` �� . \ —r /` . / —it.x. \ , i—r• -- usRFAgfl r N� �-,a �\ .--15112. �. \ �` r y}1�. '\ .\\ \` `'• \'`i •:`,„ � �r s � \ r• • .%C \ \i 4 N � \ ti \4\''� ~ „„ re. �//r• t' x�\ '4\ x ti t t ti ,C120 IN \ \ •/\ � 1 1 \ \ \ ' 1 1 1 11 1t 11 1 \t r' ` \se 1 ti 1 N. `\`\ �• , l It t', 5� '�5 1 ti ti \ N \ \ \ \ t t 11 1 44 4 1 1 \ •` \, \ , '- ' �. 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REFERENCED DRAWINGS DRAWING REVISIONS DRAWING NUMBER TITLE BY APVD DATE A USR SUBMITTAL LIM JME 05/07/18 133-997-5113 trogincomolluarn KEY MAP LEGEND BASIN DESIGNATION AREA (ACRES) % IMPERMOUS BASIN BOUNDARY HYDROLOGIC SOIL GROUP BOUINDARY [PER NROS] HYDROLOGIC SOIL GROUP DESIGNATION [PER N RCS] EXISTING GROUND INT. CONTOUR [1' INTERVAL] EXISTING GROUND INDEX CONTOUR [51 INTERVAL] HISTORIC BASIN FLOW SUMMARY AREA 05 Olo Oloo PRELIMINARY NOT FOR CONSTRUCTION MAKENA GAS PLANT OUTRIGGER ENERGY Kin aim LITLITY enrivani MIN INFICMCI1 {ENO CF MORAN ter ED-II2Z-1087) AT LEAST TAO) OLGINESS STAN ecti &Watt UV HISTORIC DRAINAGE EXHIBIT JOB NO: 15044 DRAWING NO:1804.4-003-2001 SCALE:AS SHOWN A ii T Iii IIH KEY MAP _ , H IIciddy • ' !A .. N. II I . uSR F ' -' -- --__ ` d.. `' ! " r - Ir.: .1ytiA��•, i �y ' •usR Pp a __ __ _ ----- __ �_fat* ARY — ±tt: 111 r i BOUNDARY ROAD. 85 - - N.T.S. _ ,...BOUNDARY .50?J' BERM/$'WALE �a 1 _ - DIRECTING CFR`�TE ?� ti I I It \ _ _ — : RUNOFF AROUND PROJECT SITE \\ .�� F ;vim �_•`�.c f. II ;I_ ,� '4'' V„ T _-_ ` a`r l , K•N l'•. I'I T•7 y r,"1...<• ` l\ ,11 I. I - - \ \ �` _ —` :.a4 r r _ h \ `}c,,-..-. \ CONC. 1 0 50r 100' 410' —j— _ _— — . — — I \ I y DRAINAGE" ' I .. !' I -,, PAN ', I (II I zli1T� COUNTY ROAD 86 /• ~' �. _, '�a ` II I� I k - l rI _Y'r , ' I +I .V ` 4 - . ii f \�lr k', \~�\ I 11 X?� �� „,_______-• I~-�;� I i LEGEND \3N\ h ,� :::: • !,I IIi�I.r.� ..-I, ;'I I BAN \ I ( +„ ; C �{ .I ,-0 r' i tl 1 I -• I' I I I IbilY m DESIGNATION D1 /` ~` \ 1 ' I } , :: j I :':.: "'.:. s _ sift + 1 I c� I. r 6 1'Fi RUNOFF COEF. r �` I — ..::. ::... ::..::.'.::'.::: v' I �] J • V BASIN BOUNDARY I ! ,„-;'r....... .:I �' ,.' 0 A DESIGN POINT I , • •••• • ,•?' " y .�•:, ...}.........i , 5 I I HYDROLOGIC SOIL GROUP BOUNDARY[PER MRCS ] --^~ N. I '•'`• w:L., I BERM/$WALE' �� — ti r DIRECTING '' I AROUND ( , d _ '_ r r`'��)j J `+ ' HYDROLOGIC SOIL GROUP DESIGNATION [PER NRCS] PROJECT SITE 1 !. I w wllawla�ialww ! fr I I CI ----- 8 ----- EXISTING GROUND INT, CONTOUR [1' INTERVAL] :::. I t ca I - '- ::.'.�1 f — — —5'6180— — EXISTING GROUND INDEX CONTOUR INTERVAL] hSr^ 1 y N �' I \ . :i:-.:. !'� I I �':.'.' • • ;: i~ I ? 1 MI — [5' �;C��1 \ l 1 • L„ �w�_. EXISTING STORM SEWER {CULVERT] & RIPRAP 9` f� r �. \ ,... ,'-� i__•5.8 I j I j • ...I.:: •i ~ '::' . I +1881 FIN19I GROUND INT. CONTOUR [1' INTERVAL] ' • r ` 4� .. I--4�. 1, ::.''... I \ • ' 4831 FINISH GROUND INDEX CONTOUR [5' INTERVAL] \ z q_ .•y... ,. :: :... � �f I•- ! •... :... :.:I (f1.21_670)� PROP. STORM FLARED END DIVER, OUTLET STRUCTURE Yc SECTION t..:. •:::x —' CH1> — CHANNEL SECTION CALLOUT I I ~ 'I •:I:.'.:' e p L 'v'' RIPRAP SIZE DESIGNA71ON (TYPE TYPE IA) N, :'•, �::; ......... X. ` �� N. .... ' •:X• I I S OVERLAND FLOW DIRECTION e..--\ 4 \ ~• I` +*^ CH1 9 -:'r-:: --: _ , CH2 I CAUTION - EXISTING ~ 'N/ \ - -' \ �~ I _ . , tii �� BURIED PIPEUNES OVERFLOW DIRECTION/PATH -. • ,.., ~� •-. :, 1 _ ."• r.::....,: 14.94 417.3% UNK NOM DEPTHS f` N - k i ' - !r '. I TO CONSTRU TI N �� SITE OUTFACE x. ti , !x.....................1� �..''''..:..': L" , ~•- ti` f \ \. X \ ! 1. I'. ' I .' �d'' (' 1t ti I <' y� i i'.. ■ a' •-:-..-:-#.:_ ^"�_ !} Y .. -:: I } •, 1 I I I I gC17 ;....: ;._ y ...._..... u t.......:.'.'.'.•:`.-�,� ,.,.....::: I '.'........ ...:'.�:I-.. I.•. .'.� •.:•: .' _ ,gam •� it DEVELOPED BASIN FLOW I'•, :::::::' I. y I ti •, -- k `• \ 1, S ` ti \ % �' 'I ti y `' ! g11 f.l... 'tea 15.44 ,.. Ac a0� 36 ... .' y........ _,.':: .. '.:::.., I t " �r x r ` x I• �,-� pp — • '' { ' T I ' BASIN AREA (Ac) Q5 (CPS) F Q10 F (CPS) Q100 (CPS) �\ \ ` - _t \ g, 1 ,:. , . _ Xrj r` �'� _ _ �r ' t'� D1 10.44 7,4 10.6 28.3 `111::1:11. 02 1Q 90 7 7 '11 1 29.6 \ : /:r II I ly y y II I ::•• - x alit? t I D3 2.25 5.5 B.S 123 1 z: j 1� t S i I .":" x Jt f~:'::'::'::'::':::'.::: _ ------------- / -l�,i `•I SUM Di —p3 23,60 18.8 2r}.2 68.3 Jf ,l \ ."; .. .: •y POND OUTFACE - , 50.0 LF(-I2' RCP AT 0.5% I , ,3 1 -::r.'::::';.: `=:.•:•:•:•:•:.'•::::::.. .. �'.'..: .'. t...... -- '^k ::.:. ?t¢-_ ~�� J \ ` '',POND It RELEASE LYINTRDLLQS &Y 'I •r3 I �� I• I f7 r S 2 -STAG£ OUTLET STRUCTURE I / I i II _ fD3 y^t — rI I f' k I ti I + r•. aifil�_ _ .L tt1U 13 PAPE11t, / 11, -'l ' S s /!! i S;40,10.11‘ f t )i \ ' :1 \ 11 I, 5, I Pt1Np EM IBVERF°_trN I 5 FT CREST LEN �� S� GT�1 E . I ; i• - 225 AC 100% 0.86 - ) 1 S • .. '� _ D - I ti >_ r�I I �: �. IMO' i I; ''',yI,I I }{ I1 k1 \ 5TQRMWATtn FROM THE ti ' 34'13 " .._ \ '" _ \ PP.UF_CT SITE SHEET FLOWS 1 11 5514 / \ \ \ II \SES1/SOUTHNESTERLY TO THE S, ADJACENT PARCEL LOCATED I I i i �a __ .-S0:i---L—Z--t` w r c, "r -` ,sj +X / " �II FY / I I - \ ' y MIST OF THE PROJECT SITE I $ 7 pFTFNTInM PONE / / _ � T N \ �, l L .1 \ \4.- 1 N. \ \ \ 'l `• \ I y I II 1 y I I S i k y I I t k • \. �. •i, \ \ \ \ \ \ �• \ \ \ ,, \, N ti. I'. \ \ y \ \ \\ \ \ \ ` \ \ I \ \` '\ ,, \ \ \ tit l \ \ \ \ 'l \ \ \ �\ \ , \ \ \ \ \ N. \ \ \ ` I y f •S ', l t \ \ •. _ - ` \ \ \ ` ` \ (No_BWLOJ�.k3-STt'AGE) POND INYt_' 5007_.il TCP OF POND {BERM'). 5513.00 'AWN W5.E.; 8501.24 Mgt 100-VR VOL 339 A FT IDD-YR VOL PRCA,D; 4.22 AC -F7 1 YR W.S,E•; 6012.00 DA. OhEF�FLCAY C SI: 501290 FREEBOARD: 1.0' - — • — — r --7J1;-- / f _ . r' f / . • ` r` 1 j f I �-e f - r ; f f gfr9�� .r _ .�--I—I—1 y-- - _ _ v I Ni' I. II t I_ I• U s Iti I t _ ,.. I .� Ic+n Eno MITIIMw1D, MIN rxnllr nai CUTER {f L iOPp110 11 `I '•. y til `.. \ k '} \ \ y, �' \ 1, \ __ `` it - _ _ _ _ _ _ _ i • ' - - - - - -_ - - - _ _ _ - - - -' r "" - = ` r _ 1.-•.: t `I PRELIMINARY NOT FOR CONSTRUCTION in eaD--on-ior6 mss .: --. ATDLEAST YS BTWO 12) 018 v'S uolsou on ,.M,xtked,e,,. THIS pf$AANG HAS NOT BEEN PUBLISHED BUT RATHER WS BEEN PREPARED BY ZAP ENGINEERING do CONSTRUCTION SERVICES, INC. FOR USE BY THE CLIENT NAMED IN THE TITLE BLOCK SOLELY IN RESPECT OF THE CONSTRUCTION, OPERATION AND MAINTENANCE OF THE FPCIUTY NAMED IN THE TITLE BLOCK AND SHALL NOT BE USED FOR MY OTHER PURPOSE OR FURNISHED REFERENCED DRAWINGS DRAWING REVISIONS J ,. `i's'"„ �, H![ca*a' wIa ILCOMMINIUC aor. u IVICIS_x1c OUTRIGGER ENERGY 4;� MAKENA GAS PLANT DEVELOPED DRAINAGE EXHIBIT DRAWING NUMBER TITLE REV DESCRIPTION BY CHI< APVD DATE A USR SUBMITTAL LIM JME 05/07/18 F _• 30,3-997-5113 ++A• A�a111 JOB NO: 18044 DRAWING NO: 18044-0O3-2002 RElr', TO ANY OTHER PARTY WITHOUT THE EXPRtt_+b CONSENT OF ZAP ENGINEERING 6: OONSTRUCT1ON SERVICES. INC. PLOT SIZE:ANSI D SCALE:AS SHOWN A - PROCESS AREA SECTION - - - (RE: PLAN at SITE IrNr'4Ti€r ►t+' Os-NV.1 IE:>1Cf"J SURFACING SECTIONS DTL) ialgator 'WaI C a* CCM :. ~lt -P _ Mt rata it Jar Tot i am timi cum SkAt a _ _ ASS' 0 S WIC -IrF - IPROPOSED CULVERT de F.E.S. L PLAN) k ` t* 't*x" — COMPACTED SUBGRADE PREPARE PER PROJECTS d - (SEE �; ��a_ IT� PLANS FOR END a x, - 'F (SEE •— - '—}- GEOTECHNICAL REPORT) I It TREATMENT T4PE & SIZE) •-I —.— ,.,i`,-y'.; I I —� I —I ; ._ -: - i- tif�i+�1•`- `';I MIN RIPRAP THICKNESS • ", III I I I k y. ,-..f„.. *< I III — . ►� t S� T. 1.5 TIMES I}1[[ _ {`• '* i r T ,�I$n_nT I I M1RRFI 140N �!4 s: 1S FLOW I GEOTEXTILE FABRIC L'I m .x 4 _ Q • I -I I I -I I I p _ {OR APPLA) EQUAL) �J/ _ rr C '. I-� i n ; f ^ + ^w } , D - RIPRAP RUNDOII,N , .k a� .� SEE '" . .7 ti' —I l I —I l I —I I '� ��' - "• I —III , EROSION PROTECTION — x ' Egailanngiria `--"c{., r ,, :: I=I l I —I l I "•" TREATMENT DETAILS �'_ •.• `L (SEE PLAN FOR - .4..� + w - I {THIS SHEET) ..r. ';' ; i4.irr' ';�.1 I I —I I=III=I I I I —I' LOCATIONS & SIZES) i sWau�'yf 1►nri. —I l I =I = YM�t D1A�! MICA blf ➢Ip 1Mr�fkAT r ytP 1« f>"141E 11 III —I I —I I III —III —III I I I IM IPIPO �'5�1' RIPRAP EROSION PROTEc11ON I GRANULAR BEDDING SEE IIAJGr' P�goJ4�A F!!l�r+++•�+>Io1►»RMI7t+�++?�4a9 PLAN VIEW APPROVED EQUIVALENT) III I I I I THICKNESS REQUIREMENTS (OR —I —III (THIS SHEEN Itli - WI 11 fr` 56 - 75 35 - 3D I I VD, a d '34k7aliVIS i iumine W to Vtiiiihtliii nee i' - 1Q a I nets Amy% trttkdas MCC- . RIPRAP AT CULVERT END RIPRAP AT WATER QUALITY POND RUNDOWNS''' ''�'�"�''" 'Cn�1IilLS-=Assit---i410 "I MILS V S5 - AO I ism {LawriP Lola?. riot u ILnci ua> 1 iwt M IRAFI 14GN - Ir,f • 4 p GEOTEX11LE FABRIC • RIPRAP EROSION PROTECTION SEE PLAN FOR SIZE DESIGNATION & (OR APP YD EQUAL) ICU, ` 0 - �3 II III, y I t !t T g r M ift*RIPRAP illNt . GRADATION TABLE THIS SHEET l�j{' e _ - !0 i (IS r Pi IIP,I 4 4 h MIN, THICKNESS = 1.5 TIMES (Dino) !I + �• � 1 i 1 '� 41 ICS s it s9) • y. 0 F j,}^l 7t° - /tm SW is Wig a JY oil • " 4 v .„r. _ a ,; ' SD 1+I 71 GRANULAR BEDDING SEE � t THICKNESS REQUIREMENTS !I �'�"' w ' I4 y, J'.,'I�'i . '_'. tl- .e..4 y�CMM�M� � THIS SHEET) r �`c �r T' o ;r '+-- I-11.Jelt - IQ I Pe To I ta hefts. hi u :r,r 'r - Iii I i I i I _...� � _jL � �, 1J _- J1 11 11=11 11=I�✓=II= — -- - - - al 1I=1I 1I 1I�1I-1I -- --- � O � � M�II�M�✓=MME •!Li , - mix SKIM' p '- 4ULIPTIVIr P?'!Q -gip WV 7 �. a CMG- ]ME 1ua Pr t � 'Fe!� l if`,.�iF�ii. ".1111 hQ1' � � �' tl!� /�tl+ 'JI�'7'i. � .t'Si CI : L-CIalualk'tlola 4! MI& Wain: LWYI hit a 101, id WO ,iftfIUCirtk�'S �i: fri_E... +a-_i SEE PLANS FOR LOCATIONSSIZES OF '- COMPACTED 5U6{`,RADE RIPRAP EROSION PROTECTION (PREPARE PER PROJECT GEOTEGHNIQPL REPORT) RIPRAP SECTION I1gmari.lt 11 r.pantsadrIprapµ1..icntarlcrri.l4..iilp.r7I.431 RIPRAP GRADATION TABLE 111r11' ?MELT Oa 414:411ER,' ! ? LT3 In THE /L5 SSE riven is u Kips" lag ri0 rlpn1 pibr.eral .adcr.d.ela.. twain 1 al 1) GRANULAR BEDDING GRADATION TABLE & THICKNESS REQUIREMENTS URBAN DRAINAGE •'x. FLOOD CONTROL DISTRICT URBAN DRAINAGE & FLOOD CONTROL DISTRICT RIPRAP EROSION PROTECTION DETAIL 2010 2.0' MIN. _ (SEE PLAN) M.T.S. DAYLIGHT 4:1 MAX DAYIJGHTING IN "FILL" SITUA.TICN DAYUGHTING IN - "CUT" SITUATION DAYLIGHT JP,,r off 3 I —I I —I I— 9r' sly Cr ,� ,° 4,1 MAX III=I I__ ,�5ti , f a - -I I 1-I I 1 ` .i" "?:' _III I I `3.9t W % —I 1 —I 4 e•'' FINISHED GROUND l I l I I i aa' —I W+f2 W/2 CONCRETE CUTOFF SMALLER ROCKS TO BE HAND l-1 I I PLACED AND GROUTED IN PLACE. I l I l I _ -• } --•;v ' MIRAFl 140N Y/ALL REINFORCING: r SMAALLER RbC#4S T4 11 I GEOTEXTILE FABRIC \\%---SMAI 5 AT 12A 4.G. EACH f HAND PLACED RIPRAP, —III= COMPACTED SUBGRADE _III I _ —III- = _— — SMALLER ROCKS 713 HAND PLACED PLACED SEE TABLE FOR SIZING. -I I —(PREPARE (OR APP'VD EQUAL) WAY {TOP) ROUTED PER THE PROJECT II- RIPRAP. MIND WIDE g — BE HAND PLACED AND TRANSITION GEOIECHNIChL REPORT] I III l I I l I �v AT SIDES OF FES. GROUTED IN PLACE. 12 SLOPE I - SIDE SLOPE RIPRAP EROSION t —' -., ,�.E ' I,AkD END I fI --HI—ill—II—in I i DRAINAGE CHANNEL SHALL BE LINED W/� PROTECTION CONDITION _ ♦- HAND PLACCED--PIPR-,F; SEE TABL'FFL S4$1N DapE r � �kT.,o1L +� - " CHANNEL 2 D TIMES ; , FLaftED END EITHER p. IAhJ. 6 w1,5 rAINUS fiRpVEL, SECTION CONTROL RIPRAP EROSION PROTECTION, OR RIPRAP .'vS• _ GRANULAR BEDDING SEE - - .. �!+ _ _ '1i� 12" 6R -PREPARED RE -SEEDED 141TH NATIVE SEED. POINT THICKNESS THICKNESS REQUIREMENTS _• •�y ` •�.. . "''•, ' • _.FTEINFORCED CONCRETE - i SEE PLAN FOR ' DEPTH, 3 MIN. :.; tt�?a11d�71, . ' 3 MIN. � )SUBGRADE SEE PLANS FOR CHANNEL LOCATIONS a PIPE BEDDING SURFACING/STABIIJZAZION REQUIREMENTS a (THIS ( HIS SHEET) - a Cj,1TCiFF LL �`--FES CONTROL POINT - - - r- `� OUTLET PIPE FES CONCRETE CUTOFF __ - = - FEs CONTROL FLARED END - CONTROL WI #5 REINFORCING WALL BARS CONCRETE CUTOFF WALL CHANNEL DESIGN TABLE W/ #5 S REINFORCING BARS POINT SECTION POINT AT 12 0.C, EACH ISOMETRIC VIEW SECTION A -A WAY ('1w) AT 12" a.c. EACH WAY (TIP) SECTION 8-8 CHANNELSIDE MIN. W (ft) MIN. D (ft) SLOPE A (H: V) SIDE SLOPE B (H; V) NOTES CHI 5.0 20 4: I 4:1 CH2 5,0 2.0 4:1 4:1 1. REINFORCED CONCRETE PIPE SHALL MEET CDOT STANDARDS (RE: CDDT STANDARD PLAN NO. M-503-2. REINFORCED CONCRETE PIPE, '1 SHEET) 2. CONCRETE FLARED END SECTIONS (F.E.S,) SHALL MEET CDOT STANDARDS (RE: CDOT STANDARD PLAN NO. M—BD3-1O, FLARED END SECTION END TREATMENT CONCRETE AND METAL END SECTION. 2 SHEETS) cnaim Matt unman' UfLITY rxILTonaiO tsrllt F C{AFibh 2 END TREATMENT DETAIL 3 DRAINAGE CHANNEL DETAIL �� 2010 N.T.S. 2014 N.T.S. . _ or eaD-022.1[87) hT L )y°°° PRELIMINARY NOT FOR CONSTRUCTION n� DAti5 B •mmxau+yratt.era THIS pf$AVI1NG HAS NOT BEEN PUBLISHED BUT RATHER WS BEEN PREPARED BY ZAP ENGINEERING do CONSTRUCTION SERVICES, INC. FOR USE BY THE CLIENT NAMED IN THE TITLE BLOCK SOLELY IN RESPECT OF THE CONSTRUCTION, OPERATION AND MAINTENANCE OF THE FACILITY NAMED IN THE TITLE BLOCK AND SHALL NOT BE USED FOR WY OTHER PURPOSE OR FURNISHED REFERENCED DRAWINGS DRAWING REVISIONS ,r„ cxaartlllialn I,CvwarantC11ON aararrCta_rwe OUTRIGGER ENERGY , I may= �� MAKENA GAS PLANT DRAINAGE DETAILS DRAWING NUMBER TITLE REV DESCRIPTION BY CHK APVD DATE A USR SUBMITTAL UM JME 05/07/16 .:>., .. .t,„, ;an ,. • -- a. 30.3-997-5I13 wronsialtm.dh+i^' JOB NO: 18,044 DRAWING NO: 18044—0O3-2010 REV: TO ANY OTHER PARTY WITHOUT THE EXPRt_+. CONSENT OF ZAP WGINEERING 8: OUNSTRUCTICIN SE ICES. INC. PLOT SIZE: ANSI D SCALE:AS SHOWN A ---/\V I GCiLLIM4 5" WS, I" TALL X 4.75" 1410E 3/S' GALVe+p X HOLES SPACED AT 4" COOT TYPE C INLET BOX PLATE O.C. (rip) TOP OF WQ PLATE rr YIQCV W,S.EL= 5009,24 CA ' �y . 1,5" {TOP ) STANDARD COOT TYPE C INLET GRATE p .5408.50i A}- 5008.17 . • u o 5007.83 NOTE: CONTRACTOR TO 0 SEE RESTRICTOR PLATE DTL „54.07.50 FIELD VERIFY REMOVABLE (THIS SHEET) TRASH RACK DIMENSIONS BOTTOM OF W14 PLATE • PRIOR TO FABRICATION Et A 2x2xY+ STEEL SQUARE EL=5607.17 ` - 2.91 3.92' 1.50' TUBE WELDED TO ANGLE, SEE WO PLATE DTL y 5f8" STAINLESS �' OPEN TO ALLOW [THIS SHEET)TOP 2.92' WQCV PLATE DTL BOLTS (TOP} TRASH RACK TO SUDE VIEW THROUGH (TYP) 2' 2,c' 2° N.T.S. REMOVABLE TRAM RACK SCREEN; —■.1 /Iz' PLACE , r - 1.00'--I 'vEE SEE TRASH RACK DTL STAINLESS STEEL #83 �- / ' . ' {THIS SHEET} R p * US FILTER) 1 (TYP) u IJ 5/S STAINLESS BOLTS rP) 1.5 (MP) SUPPORT ROM #1,56VEE AT I - - - - - - I .1 r- air SPACING L FRAME: 3/8" X 1° (MIN.) PLATE 4 5/8` STAINLESS -, A I 3/3` GALVANIZED 10"• BOLTS (ram) f 3.92' 1,5° {TOP',, PLATE I. X156 bEE . . 2"x%" PLATE WELDED p1 ■ • ' _ TO THE SIDE OF THE (HIZONTPL .sue �2' � TRASH RACK (TYP) CONTROL AND POINT (SEE VERTICAL PLANS) 0" B OUTLET BOX PLAN VIEW RESTRICTOR PLATE DTL REMOVABLE TRASH RACK DTL 100-YR W5 Y ItT.S, N.T.S. N.T.S. EL= 5012.00 47" 6u 35. v.. r 6' r 2. Cr� 3 -(SEE TYPE C INLET TOP OF BOX/GRATE II I I 4,D�� I� (SEE COOT STANDARD EL=5009.24 (WQCv W_5 -E_) - _ ' '� I I s * I I .j PLAN M-604-10] 1.00' CONCRETE I I OPENING BOTTOM OF RESTRICTOR PLATE - •* 1 I I - -`� 1 I * I STANDARD CDOT TYPE C INLET GRATE EL=5447,73 BOTTOM OF POND/ I / jr J' --- v1. kl I SEE TRASH RACK fa {THIS SHEET) BOTTOM OF TRASH RACE{ * I 4 �h. ,}� .� EL=5007A-2 `•— I s I �7G �Lr ). ��- rf �' ��"��—SEE RESTRICTOR PLATE DTL BOTTOM OF 14Q PLATE �..._ � PLATE EL=5U07.17 \\\ (THIS SHEET) SECTION A -A N-12' DIk RCP INV. OUT = 5007.17 6" TOPSOIL SEE TRASH RACK ❑TL {THIS SHEET) �. Icl. N.T.S FAIRAFI FILTER 140' FABRIC 5, TYPE L BURIED 0.50 = MIN. THICKNESS 2 TIMES Dso RIPRAP = 5, 6' TOPSOIL I. 3.9 y I6' THE OUTLET PIPE IS TO BE 1< TYPE L BURIED RIPRAP TOP OF POND 292 r^� s7rE��sa�sa, 4 10 BACKFlLLED WITH NATIbE EARTH 05a = 9". 4,5.. �� EL=5013.OD °`�""�" SOIL NO BEDDING MATERIAL 1:,, rc t 1, Ys`t1 y! s {— :;i MIN. THICKNESS = EST k �rrti : 7ri mi , 2 TIMES Ds]. 1 ��.�,rs� ELL5012.04 SEE RESTRICTOR PLATE 'c� �` i._, iii6" GRANULAR ' DETENTION POND . $ MOE x 3' BEEP ,u'u'I wri DTL (THIS SHEET) o— SEE Wt? PLATE DTL I x 76' LONG CONC. 4 eD 4• BEDDING �, 1 I i� I —I t-itI s .I •I� L. COMPACTED SUBCRADE CUT-OFF WALL 7(Nls SHEET) ----�—__ '-- REINFORCE W - / 1 AT 12 MO, 0 II (PREPARE PER PROJECT GEOTECHNICAL REPORT) ,.Y2��._; _ w 8 " WIDE x 3' DEEP I. BOTTOM or 0 0 o MIRaFI 14ON RCEO 1" RESTRICTOR PLATE /� -T it Rep I I EACH WAY TYP a Iw FILTER FABRIC CUT -OF WALL e iv EL -500}.73 0.56' o 10 O COMPACTED SUBCRADE --p I I o o `� c rei B' GRANULAR E#EDDING (PREPARE PER PROJECT INV. OUT EL=5007.17 — ji.) o orti v a v GEOTECHNICAL REPORT) � yr w LI LO I- a o--- CONCRETE CUTOFF VIALS (B" THICK) PLACED ----1- I I `4 SECTION A —A SECTION B — B AT 1/3 AND 2/3 OF THE PIPE LENGTH. EMBED 18' (MIN) INTO UNDISTURBED EARTHEN SOIL (TOP) N4, 5 BAR 3° CLR EMERGENCY OVERFLOW SECTION B —B 1 DETENTION POND DETAILS N.T.S. 811 uBDC±'. LQcsmr>3 2011 NOT FOR CONSTRUCTION N.T.S. (n IM -022-1097) r hT LEAST TWO P} BURIESPRELIMINARY DAYS d VDU °E THIS DRAWING HAS NOT BEEN PUBLISHED BUT RATHER HAS BEEN PREPARED BY ZAP ENGINEERING CONSTRUCTION SERVICES, INC_ FOR USE BY THE CLIENT NAMED IN THE 11TLE BLOCK SOLELY IN RESPECT OF THE CONSTRUCTION, OPERATION AND MAINTENANCE OF THE FACILITY NAMED IN THE TITLE BLOCK AND SHALL NOT BE USED FOR ANY OTHER PURPOSE OR FURNISHED REFERENCED DRAWINGS DRAWING REVISIONS EIP3WWwsa 1.0001114161PCTION saminummise OTRIGGER T a� T ' ] li- y MAKENA GAS PLANT D +,WAGE DETAILS DRAWING NUMBER TITLE REV DESCRIPTION BY CHI{ AFND. DATE A USR SUBMITTAL LIM JME 05/07/16 � ` ,;',,:, .. „„, : o, c �._ 3A3-997-5I23 wywatsintsikcorn JOB NO: 15044 DRAWING NO: 1$044—0O3-2011 REV: TO ANY OTHER PARTY WITHGUT THE EXPRt_+. CONSENT OF ZAP ENGINEERING & CONSTRUCTION SERVICES. INC. PLOT SIZE: ANSI D SCALE: AS SHOWN A. a ROAD SECTION (DP) w (RE: PLAN & SITE 5' �I La �1 a 4_I■# a Kt CINEMA wan SURFACING SEC11ONS OIL] w 4 - ar r r`rmlta k I•I �yl At: tl w �„� like F# WIRT I R€1 EA L �_�_,_�y 1 Sec; ark* ■ . IM lash di 1 I ¢., :era INLEIS w I I r I it I, Irma ar aria tar Van a•r:r•t a>m r i.ttrsir if 1 MN UtsS a ymil# l hilt: l e ti! aFl t kl li wadi wit r w �.- ; ■ `sue is u A [r r'1 ? Itt USN •= a MX s li as ■ VO a■[ II !L W ttt LIt sal Oa se `.'': ' f ..� II rte. XI ItZ047 arC•fuftl L •aae alba. , L.I Ant as.. rat 1I — -, �. • • ,• . ) r •• _ + ' c / :xi n r t •.: : l !3i■ C LUCIA .�a[im a.a msatt *711 SS sae sr.iE.a i1= I . 'I V41 G e : Iw'r`� i I - 7 , r hi 5 -. ,. L�r�.� Ti LIS Si-, anima' it #• i I to ITLITR ILE ■ MO Mall rem sac RN ■ XL tvi ■ a ■ WM Irt1a:S II•..- •. ',.2.1P4 ■ o. IMO Pa MOM a■► I Ella. WAY Mwarn ■all +oa, J r r , a ■ H SAWN aid. floral 3t 8.41 i- _ — — — B 9: . . 4 • •. B •u* ?" ` ■ r ,- . : a .: n • - r I 0-!4L1 M CM !.� �- r3iPlA4i17J{ r» rlrl Kik•. NO, AT 12" O.C I I 4 t L [ a —y a1 . w :� m •_ . a t ' sar■ au ar■t7a c■tIR SF 441•414 � a atm m ana.Z r r■ art ■ I■ MICA# ii) THICK EACH WAY (TYP) r 474 +1 i4i+/eB+�f a i+ •4!T1r 9'I RCS R� CONCRETE I I m — a�i 1 r ,c I o w r ti a M'TT≥'el ■ n:s IA II ISM l COMPACTED SUBGRADE I - I ell Is.7 744.1444L 70 - mini a t & WS Eta ft aetsLiFr e ■ 1t . r1 •I .e I , i i t :.� A Ii a ft I Ir1 a A iat • >w R X II IaWerr( t4I ca S aril. a IM■ i M ror Ir11t airamira Be ■ at (PREPARE PER PRO\.ECT I -�p[ 74001#4251 f I T ; ti a -- i S in i ■ a 1 11 GEOT CI-INIGAL REPORT) ' 1K7titir TNr a,. I .a a a la La aIII A . ar M IXXX a w la[,sa`'lIlslf 11 [a fa arms •� SECTION A— PLAN >' i-• •-• t. %3t -' na all I -', La t k di LC: *lei=13 r.,`ttAIIh:E►t swanEFIKIII #�,►,a1 ■ a11ra7 Six se SLIM w, ta■natr<tr Mai w, CT 14 lit tiallt al AM43. NC alsairlaMM 'MC 401142Pit ea a ata a ,na x.x I, I • IS 1r 1'M r IN I ■ a ¢1t o • : a , n la tsar 4 worn a- af}•1d5 _____ ,.. #4 nr—a7 eta •a9 a n Ir t=Y: i Era SON Wall :Iel■r-■aii al +i P M +[ #F:�4 rf1 a• R WPM!. NOTES'XowInn % as Lana a a stills ca a ".r. a tarts: ran a asst• r a own n stCl W SEC miasmal I �{ � gtr. as � i w r -.r w o 1. CONCRETE (MIN. 4,1700 PSI) MIX DESIGN W/ TYPE I OR oA1a[NslOr'+� sop-I#EtasoNOED �GOaC�T'E v[t� ■ *roman a f n -nazi aaa it Cr o TYPE II CEMENT (MAX WATER/CDS'IENT RATION NOT TO kl ',a ran ""'' Z Y EXCEED 0.6) PER GEOTECHNICAL REPORT & COOT I l: w la r C• x °° :SPECIFICATIONS. - �� 20' .,,,. • 2. REINFORCING STEEL SHALL BE ASTM A-615 GRADE 60 "' = �1=._ r''• �" ` � ..-- 2% FAIN II o NO. 5 AT 12" 4.C. 3• MAX. JOINT SPACING IS 10 FT EACH WAY. n w EACH WAY TYP (TYP) R PIPE !NTH ve SECT t I d Ita l d y •r, H1•r tll FLOWLINE SLOPE - fL•I it as N 1.t1 r}falalaralanrr■ a• ea aJMiraI • e 'C- r oh `t,_rx`.` VIM a .sa s- •. r-ssf •« ^ > ' d ;. ' r to to sr u to o Ch a n a Y • ,W - gar B' kill IF r14r:f1S !MAW a'ata4A. • arm «� � erg I, ■ �.• :s t■ I t . - H l �1 ! `. 1 .s: ma e ■ ■.el.r. ra.ass ■ new .a CMS u. .[fir' • as i a ain R [` - : - . St. a . Main Il [Y _I I � r, 4j F Li - ram. art es mama an naps a - —a we atta w t5uLL + r �a . ��u o . am ,I a . -. _ s n cm 4 `71 .` e I � I - a ► ^f a 44 I' ueLr I. g N ill P. In '- , as 7 H -I' y- _r- tiL•src . a - .2. -..turn XII I. a 11411 . I :f n r 1 n n n t o nil ( 1'ITT 1 D' TYP i -1_ Lain •■c�a turn or nano liar IS a J COMPACTED 5UBC,Rp.OE =UM - r H- Marl. I+— r M I ICQM'DI*v�r'it.* IILLO ^Ngle OriaGE f•° IME[Oxt%- ti* *ILL (PREPARE PER PROJECT - �.1 I - Pili lild OW R•G•n P:I°G QYCR RillreR MOVE Mot GEOTECHNICAL REPORT) F• L� r 12 :du_ UV:: WOVE CPC wisnGWT LAO SC.CFICett SECTION B —B rrt.or •a H '+ ii stock aaror atwl nit. 411•• Cfl- _. Ir ab Pita -Mike Srac I 0144.43:00,1 y 10�17[� r*tn t el T,.zt leo. c uLa r YtA F �Fl ` s'I PLAN NO. :. - - R } 1 I- GR A) r JIi .-- �1CONCRETE f ,,''a' ! tmi=1bb;ll PAN -- ...a-4-n,-ar `•� , - . , :_1`4"."-- �'. .i�p' y'a•,;P•'r"� Fataa:>!zt-tWN';ct tlaa<iaa-lyJ�s.:- Pt,_''�J ICI L.. IL LTE� ��E •_ ` { 201 �i NITS . , • 117iw'Illitln Pigged Ikappor4 SWI:7F l .x Oar c.. -.a a _s can LL, SC I� at .:.i fi1•r'teal e•a-.:fl-Fr•^ •- -a 4.213] •-`I••h'r MI- I oil a % ' OthtP'JL ftl n•N412.0.1T lag I m r a.. -.J .1.•• _ _- A a rr ! a• ASHASHI I. 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'I1- �' ' WI MTV' cssti yaw rSRrarrr r•tp 4 A9 n ri a a r d aus �..1_ Elms SELT➢l1M rats- PE1pFG1aCE0 C TL Ei.9Ri-S11.i1R R • v. r _ _ ,_ _ _ JOOMT FASTER (T u i� JCaL1�iI �iiKBCiF17 c�.4at+ itf it•'r lrlonlr Ims1 }7ic[ - 111atfnt 7r1 if team ST,t1�I� �xJ� �r i.nss.vlrwxi Cain?* Cora, 'matt al ituaport■tifA[7.1-17.', y. �•,y IAN "V�•y :...- -•... ..oD10fJa i� [��at i�ja � r (��{ CONCRETE E ✓ D _4'F.a�'•'•�• it COI �•.T AND •�/R1 r i! I-.--1-'• -�+. _. a�•31.. Li 061.41 L043 f �Lrir ,� !1^ list •,111L1 LYri --� rirafJ; • �J _ - aNl� -laiar - i '1 FOR ants Uf11TY r({IK41O1 -.� -s-, tar .fa, r' T�ar:i &{' %16O3.ln _ - - .— - win� Via' _ i ,� `iI 41•QtIF 0 •.•r .—,..,a,.r•iraraar,a eer MD t .ea,,",r ¢.r' '4aFTAL FND SFCTION l�r�• h� l 1I~i 'ti SECTIONS 'cur �e ao T Fi h ,• t r �,. ,- ,.>a it Err- rP4tr•r[f eii•:L'•a+1L Orem I`ll it.TA _. 1� Dit�0p�1 �&+.: 6C'fLTy ke4- AS wL�i 1 L"�.'2 o(2of 1,�•: S� `I PRELIMINARY NOT FOR CONSTRUCTIONSI '-.Z.:1111'...-•••• hT�LEA,STBiyp 0) O OMESS ectittaleeYou d1. THIS pf$AMNG HAS NOT BEEN PUBLISHED BUT RATHER HAS BEEN PREPARED BY ZAP ENGINEERING do CONSTRUCTION SERVICES, INC. FOR USE BY THE CLIENT NAMED IN THE TITLE BLOCK SOLELY IN RESPECT OF THE CONSTRUCTION, OPERATION AND MAINTENANCE OF THE FACIUTY NAMED IN THE TITLE BLOCK AND SHALL NOT BE USED FOR ANY OTHER PURPOSE OR FURNISHED REFERENCED DRAIIA'INGS DRAWING REVISIONS r', ,a EMCAlIMN0ICOMIMEM nom NIKVIC°L_1•IC OUT ENERGY �I1 fl �Ir`I�'"Z` 1.JGL tG IDRAWING MAKENA GAS PLANT DRAINAGE DETAILS DRAWING NUMBER TITLE REV DESCRIPTION BY CHK APVD DATE A USR SUBMITTAL LIM JME 05/07/16 ,:, ...t,„, cttaT'j n„ "tea— 30,3-997-5I13 •r+v'•vectmlaatmm JOB NO: 1 S044 NO: 1S044 -0O3-2012 REV: TO ANY OTHER PARTY WITHOUT THE EXPRI__+I CONSENT OF ZAP ENGINEERING 6: ODNSTRUC11ON SERVICES. INC. PLOT SIZE:ANSI D SCALE:AS SHOtlANN A DRAINAGE REPORT REVIEW CHECKLIST Project Name: US RI 8-0052 Makena Gas Plant The purpose of this checklist is to provide the applicant's Engineer a basic list of items that County Staff will review in regards to a drainage report. The drainage design shall meet the requirements of the Weld County Code and commonly accepted engineering practices and methodologies. A detention pond design (or other stormwater mitigation design) is appropriate for projects which have a potential to adversely affect downstream neighbors and public rights -of -way from changes in stormwater runoff as a result of the development project. The design engineer's role is to ensure adjacent property owners are not adversely affected by stormwater runoff created by development of the applicant's property. REPORT (X = complete, ❑ = required) ❑ Stamped by PE, scanned electronic PDF acceptable ❑Certification of Compliance ❑Variance request, if applicable Description/Scope of Work Number of acres for the site — 23.6 Methodologies used for drainage report & analysis Design Parameters Design storm — 100 yr/16year Release rate - 5.2 cfs URBANIZING or NON -URBANIZING Overall post construction site imperviousness Soils types D Discuss how the offsite drainage is being routed - Diverted Conclusion statement must also include the following: xl xl xl xl xl xl xl xl xl xl N Indicate that the historical flow patterns and run-off amounts will be maintained in such a manner that it will reasonably preserve the natural character of the area and prevent property damage of the type generally attributed to run-off rate and velocity increases, diversions, concentration and/or unplanned ponding ng of storm run-off for the 100 -year storm. How the project impacts are mitigated. N Construction Drawings Drawings stamped by PE, (scanned electronic PDF preferred) Drainage facilities xl N Outlet details Spillway Maintenance Plan Frequency of onsite inspections Repairs, if needed Cleaning of sediment and debris from drainage facilities Vegetation maintenance N N x N ❑ Include manufacturer maintenance specifications, if applicable Comments: Why is the outlet pipe minimum Q 6.1 cfs when flows out of the pipe are 5.2 cfs maximum? Page 7, Section V.B — please clarify. Earlier in the report it mentions that offsite flows will be diverted around the site. 4/11/2018 Weld County Department of Public WorksI Development Review 1111 H Street, Greeley, CO 80631 I Ph: 970-400-3750 I Fax: 970-304-6497 www.weldgov.comidepartments/public_worksidevelopment_review/ Hello