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Home My WebLink About20232842.tiffUSE BY SPECIAL REVIEW (USR) APPLICATION FOR PLANNING DEPARTMENT USE: AMOUNT $ APPLICATION RECEIVED BY DATE RECEIVED: CASE # ASSIGNED: PLANNER ASSIGNED: P ROPERTY INFORMATION Is the property currently in violation? ✓ No / Parcel Number: 0 9 6 1 _ 2 4 Yes Violation Case Number: 3 _0 0 _0 3 6 _ S ite Address: near 23041 COUNTY ROAD 54, GREELEY, CO 80631 Legal Description: A portion of PT S2SW4 24-5-65 LOT B REC EXEMPT RE -4137 (1.5D) Section: 24 , Township 5 N, Range 65 W Zoning District: A Acreage: 74.2898 Within subdivision or townsite? No / Yes Name: Water (well permit # or water district tap #): N/A Sewer (On -site wastewater treatment system permit # or sewer account #): N/A Floodplain No/ Yes Geological Hazard P ROJECT U SR Use being applied for: Solar Facilities Name of proposed business: CBEP Solar 30, LLC No/ Yes Airport Overlay PROPERTY OWNER(S) (Attach additional sheets if necessary.) Name: David I. Weinmeister No / ✓ Yes Company: Phone #: (970) 373-9746 Email: weinmeister1@msn.com Street Address: 23041 County Road 54 City/State/Zip Code: Greeley, CO 80631 APPLICANT/AUTHORIZED AGENT (Authorization Form must be included if there is an Authorized Agent) Name: Zach Brammer Company: CBEP Solar 30, LLC Phone #: (970) 425-3175 Email: zach@cloudbreakenergy.com Street Address: PO Box 1255 City/State/Zip Code: Sterling, CO 80751 I (We) hereby depose and state under penalties of perjury that all statements, proposals, and/or plans submitted with or contained within the application are true and correct to the best of my (our) knowledge. All fee owners of the property must sign this application. If an Authorized Agent signs, an Authorization Form signed by all fee owners must be included with the application. If the fee owner is a corporation, evidence must be included indicating the signatory has the legal authority to sign for the corporation. S ignature Zachary Brammer Date Signature Date P rint Print 07/22 9 CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Planning Questionnaire 1. Explain the proposed use and business name: o CBEP Solar 13, LLC is proposing to construct and operate the Island Grove Solar Project ("Project") in unincorporated Weld County on Parcel ID number 096124300036. The Project will be a 3.7 MWac community solar garden and will be constructed on approximately 23.21 acres of privately owned land. It will consist of solar modules mounted about 5 feet above the existing grade on single -axis trackers, which allow the panels to track the sun from east to west over the course of the day. The project will also include inverters mounted on steel posts or beams, concrete -pad mounted transformers, other electrical equipment, an access road, and a perimeter game fence with gates. 2. Explain the need for the proposed use: o Ensuring long-term energy security for the United States requires a mixture of all different types of energy production, including community solar projects like the Island Grove Solar Project. 3. Describe the current and previous use of the land. o The land is currently vacant (no existing water rights to be used for crop production) and has historically been used for oil and gas production. 4. Describe the proximity of the proposed use to residences. o The nearest residence is approximately 200 feet from the western side of the Project's fenceline. 5. Describe the surrounding land uses of the site and how the proposed use is compatible with them. o The surrounding land uses include oil and gas production and agricultural land. The parcel across County Road 54 to the south is a storage yard for industrial/oil and gas equipment. The Project will not interfere with any of the nearby uses. The aesthetics of a community solar garden will fit in well with the surrounding uses. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK PAGE 2 6. Describe the hours and days of operation (i.e. Monday thru Friday 8:00 a.m. to 5:00 g,m,), o Construction activities will take place Monday through Saturday from 7:00 a.m. to 6:00 p.m. After construction is completed, occasional maintenance will occur between 7:00 a.m. and 7:00 p.m. as needed. 7. Describe the number of employees including full-time, part-time and contractors. If shift work is proposed, detail number of employees,, schedule and duration of shifts. o Construction may require up to 50 workers to be on -site at one time during the peak of construction, all contractors during the day shift. Construction employees may include up to 15 civil workers, 15 electricians, 15 racking builders, and an additional 5 employees. During operations, two to four employees may be needed for maintenance, as needed, approximately twice a year. 8. Describe the maximum number of users, patrons, members, buyers or other visitors that the site will accommodate at any one time. o No users, patrons, members, buyers, or other visitors are expected to be on the site at any time. 9. List the types and maximum numbers of animals to be on the site at any one time (for dairies, livestock confinement operations, kennels, etc.). o Up to 500 sheep. 10. List the types and number of operating and processing equipment. o The Project will consist of approximately 9,100 solar modules mounted about 5 feet above the existing grade on single -axis trackers, which allow the panels to track the sun from east to west over the course of the day. The project will also include 37 inverters mounted on steel posts or beams, 2 concrete pad mounted transformers, and other electrical equipment. 11. List the types, number and uses of the existing and proposed structures. o There are no existing structures on the Project's site. o The proposed structures for the Project will include: I. Approximately 9,100 solar modules mounted about 5 feet above the existing grade on single -axis trackers, which allow the panels to track the sun from east to west over the course of the day. ii. 37 inverters mounted on steel posts or beams iii. 2 concrete pad mounted transformers iv. Approximately 5 utility poles that will connect the project to the existing Xcel Energy distribution line on located on the south side of the parcel of the property. (970) 425-3175 I INFO©aCLOUDBFREAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK PAGE 3 v. One temporary construction trailer vi. Two 10' x 40' storage containers that will store parts, tools, and equipment on -site during construction and operations 12. Describe the size of any stockpile, storage or waste areas. o During construction, a laydown area located within the limits of the Project area will be used to store Project facility items while facilities are installed. During operations, there will be no open stockpiling, uncovered storage, or waste areas. Up to two storage containers approximately 40 -feet in length, 10 feet in width, and 10 feet in height to store spare parts, tools, and equipment on site during construction and operations. 13. Describe the method and time schedule of removal or disposal of debris junk and other wastes associated with the proposed use. o Debris, junk, and other wastes will be stored in appropriate waste receptacles such as dumpsters during construction. CBEP Solar 13, LLC or its contractors will hire a waste management provider to regularly remove wastes associated with construction of the Project from the receptacles and bring the waste to an approved landfill or disposal site. Maintenance contractors will properly dispose of any wastes generated during operation of the Project by bringing the wastes to an approved landfill or disposal site. 14. Include a timetable showing the periods of time required for the construction of the operation. o Project construction is expected to begin in Q1 2024 and is expected to be completed in 02 2024. Construction activities would follow the estimated timetable below: Construction Phase Season/Duration Construction Begins Q1 2024 Site preparation 1-2 months Structural work 3-5 months Electrical work 2-4 months Utility work 2-4 months Construction Completion Q2 2024 15. Describe the proposed and existing lot surface type and the square footage of each type (i.e. asphalt, gravel, landscaping, dirt, grass, buildings). (970) 425-3175 I INFO©aCLOUDB!REAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK PAGE 4 o The existing lot surface type is all vegetated land. The proposed surface types and square footage of each type are listed below: i. Concrete: 173 sq ft ii. Gravel: 37,700 sq ft iii. Swales: 10,540 sq ft iv. Grass/Vacant: 187,263 sq ft v. Solar Racking: 782,438 sq ft 16. How many parking spaces are proposed? How many handicap -accessible parking spaces are proposed? o No parking spaces or handicap -accessible parking spaces are proposed. 17. Describe the existing and proposed fencing and screening for the site including all parking and outdoor storage areas. o There is no existing fencing or screening on the site. The Project will be surrounded by a game fence that is at least 7 feet tall. 18. Describe the existing and proposed landscaping for the site. o No existing landscaping. See landscaping/screening details for details on proposed future landscaping. 19. Describe reclamation procedures to be employed as stages of the operation are phased out or upon cessation of the Use by Special Review activity. o Decommissioning of the Project will commence within 12 months after power production has permanently ceased and be completed within 12 months of the decommissioning work commencing. Decommissioning will include the removal of: i. All non -utility owned equipment, conduits, structures, fencing, and foundations to a depth of at least three (3) feet below grade ii. All fences, graveled areas and access roads unless the property owner agrees for this to remain o The property will be restored to a condition reasonably similar to its condition prior to the development of the Project 20. Describe the proposed fire protection measures. o The Project is located within the La Salle Fire Protection District. The Project will comply with all Colorado Public Utilities Commission requirements as well as national codes and standards for construction, electrical, and fire. A supervisory control and data acquisition (SCADA) system will remotely monitor and control the Project 24 hours per day. The SCADA system will transmit Project data and control signals over the internet. (970) 425-3175 I INFO©aCLOUDB!REAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK PAGES 21. Explain how this proposal is consistent with the Weld County Comprehensive Plan per Chapter 22 of the Weld County Code. o The Project is consistent with the Weld County Comprehensive Plan because it: ' i. Does not interfere with any existing agricultural operations within the vicinity. ii. Respects private property rights by allowing the owner of the property to do what is in their best interest while complying with local regulations and not interfering with or infringing upon the rights of others. iii. Promotes economic growth and stability by providing a diversified source of income for the landowner, the shepherd, and the County while also offering local residents the opportunity to save money on their electricity bills through Xcel's Solar*Rewards Community Program. iv. Protects the health, safety, and general welfare of the citizens of the County by providing an emission -free source of energy. v. Is harmonious with surrounding agricultural and industrial uses. vi. Supports future mineral development by reserving space on the landowner's property where minerals can be extracted in the future. II 22. Explain how this proposal is consistent with the intent of the zone district in which it is located. (Intent statements can be found at the beginning of each zone district section in Article III of Chapter 23 of the Weld County Code.) o The landowner will continue using the water rights associated with the Project parcel on their other agricultural land. By allocating a portion of this land to the solar development, the property will be able to better allocate water to the remaining agricultural land that belongs to the landowner. The new solar development will also not interfere with any of the surrounding agricultural land uses. The Project's array will protect the land underneath and in turn allow the soil to revitalize over time, therefore preserving the land to be used for agricultural purposes in the future, if desired. We will be planting a native seed mixture on the property that will not require irrigation and grazing sheep. 23. Explain how this proposal will be compatible with future development of the surrounding area or adopted master plans of affected municipalities. o The Project will be located within the Town of Kersey and the Town of Evans' Intergovernmental Agreement area. (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBPEAKEN EPGY.COM CLOUDBREAK PAGE6 o The Project's area is included on the Future Land Use maps in the 2016 Town of Kersey Comprehensive Plan which identifies the land as "Undetermined Use". Therefore, the proposed solar development will not go against any established future plans. As described in the Town of Kersey Comprehensive Plan, one of the action items (R2.5.4) is "continue to explore alternative energy sources (solar, wind, etc.) and new technology for power sources and other critical infrastructure." This Project would allow the Town of Kersey to meet their clean energy exploration goals and continue pursuing more renewable initiatives such as the "Sustainable Energy City" designation also mentioned in the Comprehensive Plan. The Project's area is included in the Future Land Use maps in the 2022 City of Evans Master Community Plan which identifies the land as "Rural Residential". The document includes "energy production facilities "as a one of the secondary intended uses of the land earmarked for rural residential use. Therefore, the proposed solar development will not go against any future plans that the city has established. This project will fit in well with a future rural residential development due to the minimal noise, odor, traffic, and visibility impacts of a solar array. Additionally, this solar array will help reduce the energy burden on the local energy grid as local energy increases due to the city's growth. 24. Explain how this proposal impacts the protection of the health, safety and welfare of the inhabitants of the neighborhood and the County. o The Project is not anticipated to impact the health, safety, and welfare of Weld County citizens. Designs will comply with Colorado Public Utilities Commission requirements as well as national codes and standards for construction, electrical, and fire. A supervisory control and data acquisition (SCADA) system will remotely monitor and control the Project 24 hours per day. The SCADA system will transmit Project data and control signals over the internet. 25. Describe any irrigation features. If the proposed use is to be located in the A (Agricultural) Zone District, explain your efforts to conserve prime agricultural land in the locational decision for the proposed use. o The water rights for the property will be redistributed to prime agricultural land that the landowner will continue farming. By allocating a portion of this land to the solar development, the property will be able to better allocate water to the remaining agricultural land that belongs to the landowner. We will be planting a native seed mixture on the property and grazing sheep to maintain the vegetation at a height of no more than 18-22 inches. 26. Explain how this proposal complies with Article V and Article XI of Chapter 23 if the proposal is located within any Overlay Zoning District (Airport, Geologic Hazard, or (970) 425-3175 I INFO©aCLOUDBPEAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK PAGE7 Historic Townsites Overlay Districts) or a Special Flood Hazard Area identified by maps officially adopted by the County. o Flood Hazard, Geologic Hazard, and Historic Townsites: The Project is not located within the 1% Annual Chance Flood Hazard Area (Flood Zone A). According to the Colorado Geological Survey, no geologic hazards were identified within the Project Area. The Weld County property portal's Historic Townsite layer showed no presence of historic sites within the Project Area. o Airport: The Project is located within the Airport Overlay District. This District has unique height limitations as well as unique use restrictions. The use restrictions in Section 23-5-40 of the Weld County Code are defined as follows: "Notwithstanding any other provisions of this Division, no USE may be made of land or water within any zone established by this Division in such a manner as to create electrical interference with navigational signals or radio communication between the GREELEY-WELD COUNTY AIRPORT and aircraft, make it difficult for pilots to distinguish between GREELEY-WELD COUNTY AIRPORT lights and others, result in glare in the eyes of pilots using the GREELEY-WELD COUNTY AIRPORT, impair visibility in the vicinity of the GREELEY-WELD COUNTY AIRPORT, create bird strike hazards or otherwise in any way endanger or interfere with the landing, takeoff or maneuvering of aircraft intending to use the GREELEY-WELD COUNTY AIRPORT." As detailed below, the Project complies with these use restrictions as well as the height limitations: i. Electrical Interference - According to "Electro-Magnetic Interference from Solar Photovoltaic Arrays" published by the U.S. Department of the Navy, "The Federal Aviation Admiration (FAA) has indicated that EMI from PV installations is low risk. PV systems equipment such as step-up transformers and electrical cables are not sources of electromagnetic interference because of their low -frequency (60 Hz) of operation and PV panels themselves do not emit EMI. The only component of a PV array that may be capable of emitting EMI is the inverter. Inverters, however, produce extremely low frequency EMI similar to electrical appliances and at a distance of 150 feet from the inverters the EM field is at or below background levels." ii. Lights - The Project will not include any lighting, therefore there will be n o effect in distinguishing Greeley -Weld County Airport lights and others. iii. Glare - CBEP Solar 2, LLC performed a glare analysis for the Project which is included within the application package. The Project will follow all FAA regulations and utilize mitigation measures proposed by the study. iv. Visibility - The Project will not impair visibility. (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBPEAKEN EPGY.COM CLOUDBREAK PAGE 8 v. Bird Strikes and Other Hazards: The Project will not create bird strike hazards or otherwise in any way endanger or interfere with the landing, takeoff or maneuvering of aircraft intending to use the Greeley -Weld County Airport. There will be no lights on the array nor anything else that would attract birds to the project area. vi. Height Limitations: Upon review of the Greeley -Weld County Airport Master Plan's Airport Layout Plan drawings, the parcel containing the Project Area was identified as a part of the Transitional Zone as well as the Horizontal Zone. The Project abides by the Airport Zone height limitations of both the Transitional Zone and the Horizontal Zone outlined in Sec. 25-5-30. 27. Detail known State or Federal permits required for your proposed use(s) and the status of each permit. Provide a copy of any application or permit. o There are no Federal permits required for the Project. o There are two State permits that may be required - the Colorado Department of Public Health and Environment Construction Stormwater Discharge Permit and the Colorado Department of Public Health and Environment Air Permit. No applications for State permits have been submitted. (970) 425-3175 I INFO©aCLOUDB!REAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 17, 2023 PROJECT: Island Grove Solar Project SUBJECT: Development Review Questionnaire 1. Describe the access location and applicable use types (i.e., agricultural, residential, commercial/industrial, and/or oil and gas) of all existing and proposed accesses to the parcel. Include the approximate distance each access is (or will be if proposed) from an intersecting county road. State that no existing access is present or that no new access is proposed, if applicable: o There are 5 accesses on the Project parcel. - Access 1, the proposed access location for the Island Grove Solar Project, is an existing access located on the southern side of the parcel to the west of the Project parcel. This access is a residential access that will also be used to access the solar array. This access is located directly off of County Road 54, approximately 825 feet to the east of County Road 47 and 4,565 feet west of County Road 49. - Access 2 is located on the southern side of the parcel on County Road 54, approximately 2,650 feet east of County Road 47 and 2,765 feet west of County Road 49. This is an Agricultural and Oil and Gas access. - Access 3 is located on the western side of the parcel on County Road 47, approximately 150 feet north of County Road 54 and 4,205 feet south of County Road 47 1/2. This is an Agricultural Access. - Access 4 is located on the western side of the parcel on County Road 47, approximately 1,100 feet north of County Road 54 and 3,220 feet south of County Road 47 1/2. This is an Agricultural Access. - Access 5 is located on the western side of the parcel on County Road 47, approximately 1,145 feet north of County Road 54 and 3,185 feet south of County Road 47 1/2. This is an Agricultural Access. 2. Describe any anticipated change(s) to an existing access, if applicable: o No accesses will be relocated, but one existing access will be improved as a part of the Project. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK PAGE 2 3. Describe in detail any existing or proposed access gate including its location: o There will be a 7 -foot tall perimeter fence around the Project. There will be an access gate located along the western side of the Project Area. 4. Describe the location of all existing accesses on adjacent parcels and on parcels located on the opposite side of the road. Include the approximate distance each access is from an intersecting county road: o The parcel to the north of the Project parcel utilizes accesses located on adjacent parcels. There are 4 accesses through adjacent parcels that can access this parcel. - Access 1 is located on County Road 54, approximately 2,650 feet to the east of County Road 47 and 2,765 feet to the west of County Road 49. - Access 2 is located on County Road 47, approximately 1,145 feet north of County Road 54 and 3,185 feet south of County Road 47 1/2. - Access 3 is on County Road 47, approximately 1,840 feet north of County Road 54 and 2,510 feet south of County Road 47 1/2. - Access 4 is located on County Road 47, approximately 2,650 feet north of County Road 54 and 1,685 feet south of County Road 47 1/2. o The parcel to the east of the Project parcel has 8 accesses. - Access 1 is located on County Road 54, approximately 2,650 feet to the east of County Road 47 and 2,765 feet to the west of County Road 49. - Access 2 is located on County Road 54, approximately 4,110 feet to the east of County Road 47 and 1,130 feet to the west of County Road 49. - Access 3 is located on County Road 54, approximately 5,140 feet to the east of County Road 47 and 90 feet to the west of County Road 49. - Access 4 is located on County Road 49, approximately 810 feet north of County Road 54 and 4,890 feet south of CO -34. - Access 5 is located on County Road 49, approximately 2,015 feet north of County Road 54 and 3,700 feet south of CO -34. - Access 6 is located on County Road 49, approximately 2,170 feet north of County Road 54 and 3,550 feet south of CO -34. - Access 7 is located on County Road 49, approximately 2,380 feet north of County Road 54 and 3,335 feet south of CO -34. - Access 8 is located on County Road 49, approximately 3,060 feet north of County Road 54 and 2,670 feet south of CO -34. o There are two adjacent parcels to the south of the Project parcel. The eastern parcel to the south of the Project parcel has 2 accesses. - The first access is located on County Road 54, approximately 830 feet to the east of County Road 54 and 4,575 feet to the west of County Road 49. (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBPEAKEN EPGY.COM CLOUDBREAK PAGE 3 - The second access is located on County Road 54, approximately 580 feet to the east of County Road 47 and 4,820 feet to the west of County Road 49. o There are two adjacent parcels to the south of the Project parcel. The western parcel to the south of the Project parcel has 3 accesses. - Access 1 is located on County Road 54, approximately 305 feet to the east of County Road 47 and 5,030 feet to the west of County Road 49. - Access 2 is located on County Road 54, approximately 580 feet to the east of County Road 47 and 4,820 feet to the west of County Road 49. - Access 3 is located on County Road 47, approximately 85 feet to the north of County Road 54 and 4,255 feet to the south of County Road 47. o The parcel to the west of the Project parcel across County Road 47 has 7 accesses. - Access 1 is on the southern side of the parcel directly off of County Road 54, approximately 900 feet west of County Road 47 and 4,335 feet east of County Road 45. - Access 2 is on the eastern side of the parcel, approximately 1,300 feet north of County Road 54 and 3,070 feet south of County Road 47 1/2. - Access 3 is on the southern side of the parcel, approximately 1,345 feet west of County Road 47 and 3,880 feet east of County Road 45. - Access 4 is on the southern side of the parcel, approximately 1,790 feet west of County Road 47 and 3,420 feet east of County Road 45. - Access 5 is on the southern side of the parcel, approximately 2,260 feet west of County Road 47 and 2,960 feet east of County Road 45. - Access 6 is on the southern side of the parcel, approximately 2,420 feet west of County Road 47 and 2,790 feet east of County Road 45. - Access 7 is on the southern side of the parcel, 2,470 feet north of County Road 47 and 2,705 feet east of County Road 45. o There are two adjacent parcels across County Road 54 to the south of the Project parcel. The parcel to the west of the Project parcel across County Road 47 has 4 accesses. - Access 1 is located on County Road 54, approximately 3,260 feet to the east of County Road 47 and 2,130 feet to the west of County Road 49. - Access 2 is located on County Road 54, approximately 290 feet to the east of County Road 47 and 5,080 feet to the west of County Road 49. - Access 3 is located on County Road 47, approximately 640 feet t0 the south of County Road 54 and 4,560 feet to the north of County Road 52. (970) 425-3175 I INFO©aCLOUDBFREAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK PAGE 4 - Access 4 is located on County Road 47, approximately 820 feet to the south of County Road 54 and 4,382 feet to the north of County Road 52. o There are two adjacent parcels across County Road 54 to the south of the Project parcel. The parcel to the east of the Project parcel across County Road 47 has 1 access. This access is located on County Road 54, approximately 2,650 feet east of County Road 47 and 2,765 feet west of County Road 49. 5. Describe any difficulties seeing oncoming traffic from an existing access and any anticipated difficulties seeing oncoming traffic from a proposed access: o The proposed access should not have any difficulties seeing oncoming traffic. 6. Describe any horizontal curve (using terms like mild curve, sharp curve, reverse curve, etc.) in the vicinity of an existing or proposed access: o The proposed access does not have any horizontal curves in the vicinity. 7. Describe the topography (using terms like flat, slight hills, steep hills, etc.) of the road in the vicinity of an existing or proposed access: o The topography of the road in the vicinity of the proposed access is flat. (970) 425-3175 I INFO©aCLOUDBFREAKENEPGY.COM I CLOUDBPEAKENEPGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Environmental Health Questionnaire 1. Discuss the existing and proposed potable water source. If utilizing a drinking water well, include either the well permit or well permit application that was submitted to the State Division of Water Resources. If utilizing a public water tap, include a letter from the Water District, a tap or meter number, or a copy of the water bill.: o The Project area does not have an existing potable water source. There is no proposed potable water source for the Project. Bottled water will be provided for the construction team. Any water used for dust mitigation will be brought to the property from an external source. 2. Discuss the existing and proposed sewage disposal system. What type of sewage disposal system is on the property? If utilizing an existing on -site wastewater treatment system, provide the on -site wastewater treatment permit number. (If there is no on -site wastewater treatment permit due to the age of the existing on -site wastewater treatment system, apply for a on -site wastewater treatment permit through the Department of Public Health and Environment prior to submitting this application.) If a new on -site wastewater treatment system will be installed, please state "a new on -site wastewater treatment system is proposed." (Only propose portable toilets if the use is consistent with the Department of Public Health and Environment's portable toilet p olicy.) o There is no existing on -site sewage disposal system. The operation of the Project is not anticipated to require a sewage disposal system. CBEP Solar 13, LLC or its contractors will provide portable toilets during construction. 3. If storage or warehousing is proposed, what type of items will be stored: o The Project will include up to two 10' x 40' storage containers that will store parts, tools, and equipment on site during construction and operations. 4. Describe where and how storage and/or stockpile of wastes, chemicals, and/or petroleum will occur on this site: o During construction wastes will be stored in appropriate waste receptacles such as dumpsters. CBEP Solar 13, LLC and its contractors will hire a waste management provider to regularly remove wastes associated with construction of the Project from the receptacles and bring the waste to an approved landfill (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK PAGE2 or disposal site. Maintenance contractors will properly dispose of any wastes generated during operation of the Project by bringing the wastes to an approved landfill or disposal site. During construction, up to 1,000 gallons of fuel will be stored on -site in appropriate containers. No fuel will be stored on site for operations. No other chemicals are anticipated to be stored during construction or operation of the Project. 5. If there will be fuel storage on site, indicate the gallons and the secondary containment. State the number of tanks and gallons per tank: o Up to 1,000 gallons of fuel are anticipated to be stored on one site at one time during construction. Storage of fuel will follow applicable secondary containment requirements, as applicable. There will not be fuel storage during operation of the Project. 6. If there will be washing of vehicles or equipment on site, indicate how the wash water will be contained: o There will not be vehicle washing/equipment on site during the construction and operation of the Project. 7. If there will be floor drains, indicate how the fluids will be contained: o None of the facilities constructed for the Project will contain floor drains or require wastewater treatment. 8. Indicate if there will be any air emissions (e.g. painting, oil storage, etc.): o Traffic volume, primarily in the form of passenger vehicles, would increase in and around the Project area during construction. The increased traffic would temporarily increase odors and exhaust from vehicle emissions. Odors are anticipated from the operation of heavy machinery during grading, pile driving, and other installation activities at specific time periods throughout construction. Impacts from odors during Project operation would be minimal, likely restricted to emissions from the vehicles of maintenance personnel. 9. Provide a design and operations plan if applicable (e.g. composting, landfills, etc.): o A design and operations plan is not applicable to the Project. 10. Provide a nuisance management plan if applicable (e.g. dairies, feedlots, etc.): o A nuisance management plan is not applicable to the Project. 11. Additional information may be requested depending on type of land use requested: o If any additional information is required, please don't hesitate to contact Zach Brammeratzach@cloudbreakenergy.com- (970) 425-3175. (970) 425-3175 I INFO©aCLOUDB!REAKENEPGY.COM I CLOUDBPEAKENEPGY.COM FOR COMMERCIAL OR INDUSTRIAL BUILDINGS, PLEASE COMPLETE THE FOLLOWING INFORMATION: Business Name: Address: Business Owner: Home Address: CBEP Solar 13, LLC PO Box 1255 Cloudbreak Energy Partners, LLC PO Box 1255 Phone: City, state, zip: Phone: City, state, zip: List up to three persons in the order to be called in the event of an emergency: NAME Zachary Brammer TITLE COO PHONE (970) 425-3175 (970) 425-3175 Sterling, CO 80751 (970) 425-3175 Sterling, CO 80751 ADDRESS PO Box 1255, Sterling, CO 80751 Becca Gallery Partner (970) 573-6440 PO Box 1255, Sterling, CO 80751 James Cleland CEO (970) 425-3175 PO Box 1255, Sterling, CO 80751 Business Hours: 8-5 UTILITY SHUT OFF LOCATIONS: Main Electrical: Gas Shut Off: Depicted on USR Map Days: M -F N/A Exterior Water Shutoff: N/A Interior Water Shutoff: N/A 07/22 12 4754284 09/09/2021 09:56 AM Total Pages: 4 Rec Fee: $28.00 Carly Koppes - Clerk and Recorder, Weld County , CO EASEMENT OPTION AGREEMENTM�,M+® MEMORANDUM OF LEASE AND OPTION AGREEMENT OF LEASE AND EASEMENT Weinmeister THIS MEMORANDUM �� 1 and between David L. Wei is entered into as of September 7, by. � � company, and its ("Memoraftth1fl') � ers LLC, a Delaware limited liability p Y ("Owner), and Cloudbreak Energy Partners, successors and assigns ("Operator"). RECITALS ' thatcertain Lease and Easement Option. Agreement Owner and Operator have entered into that��Owner has granted A."September 2021(the "Effective Date"), whereby "Lease Agreement"), �, dated �'� to lease and develop a (the �and an option conduct due diligence on the Owner's Propertyp Operator the right to rights his can, over, under, across, and Owner's Property ery (the "Option"), together with easement g portion of the p � inState of Colorado, and being more particularly Owner's Property, the County/City of Weld, through said pProperty"). inmade a part hereof (the "Owner's described Schedule A attached hereto and.. to evidence the Lease Agreement and This Memorandum is being executed and recorded sect. B. • - � provisions of the Lease Agreement in any respect. shall not be construed to limit, amend or mode the MEMORANDUM David L. Weinmeister, with an address of 23041 1. OWNER. The name of the Owner is County Road 54, Greeley, CO 80631. OPERATOR. The name of the Operator is Cloudbreak Energy Partners, LLC, a Delaware . , of 4845 Pearl East : Circle, Suite 11.8 #53242, Boulder, limited liability company, hav xng an address Colorado 80301, and its successors and assigns. 3. LEGAL DESCRIPTION. . The specific legal description of the Owner's Property is de scribed on Schedule A and is incorporated herein by this reference. 4. OPTION TERM. granted Owner has Operator the right to conduct due diligence on the Owner's Property to determine if the Operator would like to enter into a lease. The initial term of the Option Agreement is a period commencing September ommencin on 7, 2021 and ends on September 7, 2024. The term of the calebdar year, as provided in the Lease Option may be extended, at Operator's discretion, for one (1.} p Agreement. 5. LEASE TERM. In the event the Option is exercised under the Lease Agreement, the term of the lease will commence on the Commencement Date (as defined in the Lease Agreement) and shall on the twentieth 20'") anniversary of the Commercial Operation Date (as defined in the Lease expire ( Agreement). 6. EXTENTION TERMS. Operator has the option to extend the term of the lease for three (3) additional extension terms of five (5) years each on the terms and conditions more particularly set forth in the Lease Agreement. 7. EASEMENTS. In connection with the Lease Agreement, Owner has granted or has agreed to grant Operator a number of easements on, over, under, across and through Owner's Property, which are fully described in the Lease Agreement. 1 4840-2683-2374.5 4754284 09/09/2021 09:56 AM Paget of4 8. OTHER. TERMS. In addition to those terms referenced herein, the Lease Agreement contains numerous other terms, covenants and conditions, and notice is hereby given that reference should be made to the Lease Agreement directly with respect to the details of such terms, covenants, and conditions. In the event of a conflict between the provisions of this instrument and the Lease Agreement, the provisions of the Lease Agreement shall control. 9. AGREEMENT TO COOPERATE: At the request of Owner after expiration of the termination of the Lease Agreement, Operator shall reasonably cooperate with Owner in all respects with obtaining the removal of the Memorandum from title, including without limitation executing a termination of Memorandum in form reasonably required by Owner. IN WITNESS WHEREOF, the undersigned have caused this instrument to be executed as of the date first written above. OWNER 141 David L. Weinmeister STATE OF COLORADO ) ss. COUNTY OF WELD The foregoing instrument was acknowledged before me this 7th day of September, 2021, by David L. Weinmeister. Witness my hand and official seal My commission expires: — ) S 5 My f Notary number is: co I got Not ry Public PAMELA ANN THOMPSON NOTARY PUBLIC STATE OF COLORADO NOTAF?Y ID 20014018021 intentionally blank. Si' MY COMMISSIont ,na .re .com u�twtR%wN �[Remaitider of pagee y �. 2 4840-2683-2374.5 4754284 09/09/2021 09:56 AM Page 3 of 4 OPERATOR Cloudbreak Energy Partners, LLC, a Delaware limited liability company By: Na . Zachary Ti e: A‘-) .� t STATE OF COLORADO ) ss. COUNTY OF WELD ) The foregoing instrument was acknowledged before me this 7th day of September, 2021, by Zachary Brammer, the A tkniclitritzrts S; G,4„t( 'of Cloudbreak Energy Partners, LLC, a Delaware limited liability company, on behalf of the limited liability company. Witness my hand and official seal My commission expires: 6, — � .v PAMELA ANN THOMPSON NOTARY PUBLIC STATE OF COLORADO NOTARY ID 20014018021 M COMMISSION EXPIRES JUNE 15, 2025 3 4840-2683-2374.5 4754284 09/09/2021 09:56 AM Page 4 of 4 Schedule A to Exhibit D TO MEMORANDUM OF LEASE AND EASEMENT OPTION AGREEMENT Description of Owner's Property The following real property located in the County of Weld, State of Colorado: Parcel number: 0961243 0003 6 Legal: PT 525W4 24-5-65 LOT B REC EXEMPT RE -4137 (1.5D) Property Address: 23170 County Road 54, Greeley, CO 80631 Property Map: 4 4840-2683-2374.5 i TRC March 23, 2023 Brandon Marette Energy Liaison and Land Use Coordinator Colorado Parks and Wildlife Northeast Region Office 6060 Broadway Denver, CO 80216 123 N. College Ave., Ste. 370 970.484.3263 Fort Collins, CO 80524 TRCcompanies.com Sent via email to: brandon.marette@state.co.us RE: Cloudbreak Energy Partners, LLC — Island Grove Solar Project Review and Request for Concurrence Mr. Marette, Cloudbreak Energy Partners, LLC (Cloudbreak) is seeking assistance with identifying developmental constraints for the Island Grove Solar Project (Project, Project Area), a proposed solar photovoltaic energy development that will generate 3.04 MWac of alternating current and 3.95 MW of direct current power. The Project Area occupies approximately 27 acres located north of County Road 54, approximately 0.2 miles east of County Road 47, and approximately 0.5 miles west of County Road 49 in unincorporated Weld County, Colorado (Township 5N Range 65W Section 24). Figure 1 illustrates the location of the Project. TRC anticipates approximately 150 feet of new overhead transmission line running from the Project Area's southwest corner across CR 54 to interconnect with the exiting transmission line on the south side of CR 54 (Figure 1). Preliminary timeline estimates are Q2 of 2024 for start of construction Q4 of 2024 for COD. TRC completed a Project -specific desktop analysis to identify critical development issues. The following biological resources were identified within the Project Area: • The Project Area consists entirely of private land classified as cultivated crops. • TRC conducted a wetland and waterbody analysis of the Project Area using U.S. Geological Survey National Hydrography Dataset (NHD) and U.S. Fish and Wildlife Service National Wetlands Inventory (NWI) desktop data. No wetlands or waterbodies were identified within the 27 -acre Project Area. According to the NHD and NWI, the nearest waterbodies are the Latham Ditch, which sits approximately 0.3 miles east of the Project Area; and an unnamed excavated riverine feature running along County Road 54 terminating approximately 0.2 miles west of the Project Area. The Project Area does not sit within a Federal Emergency Management Agency floodplain. Based on aerial imagery, an excavated irrigation ditch runs along the Project Area's northern boundary (Figure 2). • The Colorado Parks and Wildlife (CPW) Threatened and Endangered Species List includes 31 state -listed threatened and endangered species including one amphibian species, eight bird species, 14 fish species, and eight mammal species. According to CPW Species Activity Maps and High Priority Habitats GIS data, the Project Area is within the breeding range of the burrowing owl and overall range of Preble's meadow jumping mouse. Based on an assessment of each species' habitat requirements, range, and distribution, it is unlikely potentially suitable habitat for either state listed species is Brandon Marette March 23, 2023 Page 2 of 2 present within the Project Area. Suitable habitat for burrowing owls may be present to the south of the Project Area across CR 54. • The Project does not sit within or in the vicinity of any State Wildlife Areas. • According to data from the CPW Wildlife Species Map Application, bald eagle winter range, winter forage, winter concentration, and summer forage area is mapped approximately 0.8 miles north of the Project Area. A bald eagle roost area is located approximately 1.5 southeast of the Project Area. An inactive bald eagle nest is located approximately 1.8 miles east of the Project Area (Figure 3A). The Project Area is also within the golden eagle breeding range. Although foraging habitat may be present, the Project Area lacks any nesting substrate (cliffs or large trees) to support breeding golden eagles. • The Project Area is within mule deer overall range. Mule deer winter range, severe winter range, concentration area, and winter concentration area is located approximately 1.1 miles northwest of the Project Area (Figure 3B). A designated mule deer highway crossing is mapped approximately 0.75 miles north of the Project Area. TRC, on behalf of Cloudbreak, requests CPW's review and concurrence of the state -listed species findings. Cloudbreak will coordinate with CPW to develop applicable avoidance and minimization measures, where required. If species -specific surveys are recommended, please provide the preferred survey methodology. Project -specific shapefiles have been provided to assist in your review. If you have any questions regarding this request, please contact me at (970) 214-3338 and plorenz@trccompanies.com. Thankyou in advanceforyourpromptresponsetothis request. Sincerely, Patti Lorenz Senior Environmental Specialist ae.e.. Ben Hall Biologist Enclosures: Figure 1 (Project Overview); Figure 2 (Landuse Map); Figures 3A and 3B (CPW High Priority Habitat Overview); Shapefiles cc: Zach Brammer (Cloudbreak) Alec Shobe (Cloudbreak) Jamie Schlangen (TRC) OORDINATE SYSTEM: NAD 1983 2011 STATEPLANE COLORADO NORTH FIPS 0501 FT US: MAP ROTATION: 0 OUT NAME ISLitNr)GROVE FIGURE" �lY "' ON 1t19/2023. 12:20:22 PM: FILE PATH. riv-LIECTSICEEPV OORDINATE SYSTEM: NAD 1983 STATEPLANE COLORADO NORTH F1PS O501 FEET MAP ROTATION: C OUT NAME ISLANDGROVE FIGURE2 r`• ,ROVF%2-APRX\ISL4NDGROVE.APRX; ti'OJF_ C TSICi3EP152' BY.. BLEE ON 1/2.0/2023. 14:25:20 PM: Ft ^ PA-' T. °ORDINATE SYSTEM: NAD 1983 STATEPLANE COLORADO NORTH FIPS 0501 FEET MAP ROTATION: C LAYOUT NAME ISLANDGROVE FIGURE3A IECTSICBEP1528689 ISLANDGROVEl2 APRXUSLANDGROVE.APRX: BY 11 cr DN 1/23/2023, 15:13:39 PAS'- rTf PROJECT: SITE BOUNDARY BALD EAGLE SUMMER FORAGE, WINTER CONCENTRATION, WINTER FORAGE, WINTER RANGE, ROOST SITE, AND NEST SITES BALD EAGLE ACTIVE NEST SITE 1/4 MILE BUFFER BALD EAGLE ACTIVE NEST SITE 1/2 MILE BUFFER BASE MAP: GOOGLE SATELLITE (2021). DATA SOURCES: TRC, COLORADO PARKS AND WILDLIFE 0 0.25 0.5 MILES 1:36,000 1" = 3 000' CLOUDBREAK ENERGY PARTNER ISLAND GROVE SOLAR SITE WELD COUNTY, COLORADO TITLE: CPW HIGH PRIORITY HABITAT OVERVIEW DRAWN BY: B. LEE CHECKED BY: B. TRACY APPROVED BY: B. HALL DATE: JANUARY 2023 PROJ. NO.: 528689 FIGURE 3A 1526 COLE BOULEVARD BUILDING 3, SUITE 150 LAKEWOOD, CO 80401 PHONE: 303.792.5555 FILE: ISLANDGROVE OORDINATE SYSTEM: NAD 1983 STATEPLANE COLORADO NORTH FIPS O501 FEET MAP ROTATION: C LAYOUT NAME ISLANDGROVE FIGURE3B JECTSICBEP1528669 ISLANDGROVEl2 APRXUSLANDGROVE.APRX: :34 PM: FILE BY.. BLEE ON 2/17/2023. 1.:' PROJECT: SITE BOUNDARY WHITE-TAILED DEER CONCENTRATION AREA AND WINTER RANGE MULE DEER CONCENTRATION AREA, SEVERE WINTER RANGE, WINTER RANGE, AND WINTER CONCENTRATION AREA BASE MAP: GOOGLE SATELLITE (2021). DATA SOURCES: TRC, COLORADO PARKS AND WILDLIFE 0 0.25 0.5 MILES 1:36,000 1" = 3 000' CLOUDBREAK ENERGY PARTNER ISLAND GROVE SOLAR SITE WELD COUNTY, COLORADO TITLE: CPW HIGH PRIORITY HABITAT OVERVIEW DRAWN BY: B. LEE CHECKED BY: B. TRACY APPROVED BY: B. HALL DATE: FEBRUARY 2023 PROJ. NO.: 528689 FIGURE 3B TRC 1526 COLE BOULEVARD BUILDING 3, SUITE 150 LAKEWOOD, CO 80401 PHONE: 303.792.5555 FILE: ISLANDGROVE CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Decommissioning Plan Approach CBEP Solar 13, LLC has developed this decommissioning plan for the Island Grove Solar Project, to be implemented after the contracted lease term has ended. CBEP Solar 13, LLC, the owner of the 3.7 MW AC Solar Energy Facility (SEF) will be responsible for the decommissioning. Decommissioning of the Project will include removal of all above and below -ground infrastructure, including the arrays, inverter structures, concrete foundations and pads, and electrical infrastructure. All fences, graveled areas and access roads shall be removed unless landowner agreement to retain is presented, in writing, in which the property owner agrees for this to remain. The property shall be restored to a condition reasonably similar to its condition prior to development of the 3.7 MW AC SEE Grading and re -vegetation will comply with all applicable rules and regulations. Exclusions from the decommissioning plan include planting trees, removing internal site roads, and re -grading to previous conditions. All non -utility owned equipment, conduits, structures, fencing, and foundations to a depth of at least 3' below grade shall be removed. Decommissioning activities will follow the CDOT best management practices (BMPs) for erosion and sediment control and stormwater management that are applied during project construction, or any new BMPs relevant at the time. CBEP Solar 13, LLC will decommission the Project once the contracted lease term is over, if the lease term is not extended or renewed. Decommissioning may also be initiated if the project is no longer viable, or in the case of a force majeure event (described below). CBEP Solar 13, LLC will provide notice to Weld County prior to commencement of decommissioning the Project. Estimated Timeline and Cost Decommissioning/reclamation shall commence within 12 months after power production has permanently ceased and be completed within 12 months from the start date of the decommissioning/reclamation work. Decommissioning/reclamation cost estimates, which shall be updated every five years from the establishment and submittal of the Security, shall include all costs associated with the dismantlement, recycling, and safe disposal of facility components and site reclamation activities, including the following elements: (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK PAGE 2 • All labor, equipment, transportation, and disposal costs associated with the removal all facility components from the facility site • All costs associated with full reclamation of the facility site, including removal of non-native soils, fences, and constructed access roads • All costs associated with reclamation of any primary agricultural soils at the facility site to ensure each area of direct impact shall be materially similar to the condition it was before construction • All decommissioning/reclamation activity management, site supervision, and site safety costs • All other costs, including administration costs, associated with the decommissioning and reclamation of the facility site • The established date of submission of the financial assurance mechanism to Weld County Prior to construction, CBEP Solar 13, LLC will provide the County with an irrevocable standby letter of credit, bond, or alternate form of financial assurance mechanism in an amount sufficient to fund the estimated decommissioning costs required by the Code. The Security shall: • Name the Board of County Commissioners of Weld County as the sole beneficiary of the letter of credit • Be issued by an A -rated financial institution based upon a rating provided by S&P, Moody's, Fitch, AM Best, or other rating agency with similar credentials • Include an automatic extension provision or "evergreen clause" • Be "bankruptcy remote", meaning the financial assurance mechanism will be unaffected by the bankruptcy of the SEF operator Weld County, in its sole discretion, may approve alternative forms of a financial assurance mechanism such as, but not limited to bonds, letters of credit, or other securities, if it finds that such alternative forms will provide an assurance of the availability of financial resources for decommissioning/reclamation that equals or exceeds that provided by the form required herein. Furthermore, Weld County shall have the right to draw upon the irrevocable standby letter of credit, or other form of financial assurance mechanism, to pay for decommissioning in the event that the holder has not commenced decommissioning/reclamation activities within 90 days of the Board of County Commissioners order or resolution directing decommissioning/reclamation. Continued Beneficial Use If prior to decommissioning the Project, the landowner determines that any of the Project components can be beneficially used on the land after disassembly, such items would be (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBF EAKEN EPGY.COM CLOUDBREAK PAGE 3 exempt from the requirements for decommissioning. If a third party acquires the Project or a portion of the Project, such third party would be responsible for providing evidence of a plan of continued beneficial use for their relevant Project components. Force Majeure An exception to these requirements will be allowed for a force majeure event, which is defined as any event or circumstance that wholly or partly prevents or delays the performance of any material obligation arising under the Project permits, but only t0 the extent: • Such event is not within the reasonable control, directly or indirectly, of CBEP Solar 13, LLC (including without limitation events such as fire, earthquake, flood, tornado, hurricane, acts of God and natural disasters; war, civil strife or other similar violence); • CBEP Solar 13, LLC has taken all reasonable precautions and measures to prevent or avoid such event or mitigate the effect of such event on CBEP Solar 13, LLC's ability to perform its obligations under the Project permits and which, by the exercise of due diligence, it has been unable to overcome; and • Such event is not the direct or indirect result of the fault or negligence of CBEP Solar 13, LLC. In the event of a force majeure event, which results in the absence of electrical generation by the Project for 12 months, CBEP Solar 13, LLC must demonstrate to Weld County by the end of the 12 months of non -operation that the Project will be substantially operational and producing electricity within 24 months of the force majeure event. If such a demonstration is not made to Weld County's satisfaction, then decommissioning of the Project must be initiated 18 months after the force majeure event. (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBPEAKEN EPGY.COM Weld County Drainage Code Certificate of Compliance Weld County Case Number: USR23-0021 Parcel Number: #0961124300036 Legal Description, SectionfTownship/Range: THE SOUTH 112 OF THE SOUTHWEST 1/4 OF SECTION 24, TOWNSHIP 5 NORTH, RANGE 65 WEST OF THE 6TH P.M. Date: July _ 3, 2023 I Allyson Williamson , Consultant Engineer for TRC (Applicant), understand and acknowledge that the applicant is seeking land use approval of the case and parcel in the description above. I have designed or reviewed the design for the proposed land use set for in the application. I hereby certify, on behalf of the applicant, that the design will meet all applicable drainage requirements of the Weld County Code with the exception of the variance(s) described on the attached exhibits. This certification is not a guarantee or warranty either expressed or implied. Engineer's Stamp: is 4 4Upon/ waliamean, 1/41 i% •'gy f. 4- 1. rE�:k'IJ -; Oa) 100.'31';')Z3 y E gineer of Record Signature Variance Request (If Applicable) 1. 2. 3. Describe List Describe Demonstrate that result _This the there of design drainage the the the are project. hardship proposed that no criteria granting adverse st for of alternative the which impacts of Weld the s the variance prepared. County with from variance engineering stormwater Code will is still rea being of adequately runoff which rationale requested. a to r variance the which protect m public supports is public being rights from health, the -of requested. -way intent safety, t and/or of r� the and offsite Weld general for properties County a welfare r Code. as uir and a s .1 detention for the proposed development to com l with the Weld Count En ineerin and Construction Criteria (WCECC) Manual Requirements, updated January 2021. The study summarizes findings from performing a h drolo is analysis of the project site to identify the potential stormwater impact from the proposed solar project and ensures that stormwater will not be concentrated, nor will it exceed historical flows when it leaves the parcel to County Y Road 5 54, protecting the existing in restructure of Weld County. kineiwarie_ l��le its s aPublic Works DirectorlDesignee fie 9 _ i� Zv23 of Sign gn ure Comments: Public Works Director/Designee Review (If p blic„ ble) Signature Approved El Denied • Department of Public Works I Development Review 1111 H Street, Greeley, CO 80631 I Ph: 970-304-6496 I www.weldgov,com/departments/public_works/development_review 08/02/2019 Ay TRC Stormwater Drainage Study CLOUDBREAK L NLRGY PARTNLRS Date: To: From: Project: Subject: 08/31/2023 Cloudbreak Energy Allyson Williamson, TRC Companies 700 Highlander Blvd., Suite 210 Arlington, TX 76015 Island Grove Solar Project On -Site Drainage Study FOR PERMITTING PURPOSES ONLY Ally }an/ altanuon aj O REG T �O WI II"viz vo £ F9 60360 - EXP 10/31/2023 ,rFss/ 0 N A L E\%\�a Prepared by or under the Direct Supervision of: Allyson Williamson, P.E. 60360 "08/31/2023" Cloudbreak Energy is pursuing the development of the Island Grove project, a photovoltaic energy generation facility at a 27.8 -acre site in Weld County, Colorado, alongside Co Rd 54 (See Appendix A — Site Plans C-301 & C-302). The existing site currently is used for agricultural purposes with approximately 1% slopes. This drainage study was prepared to summarize findings from performing a hydrologic analysis of the project site to identify the potential stormwater impact from the proposed solar project and develop appropriate drainage best management practices (BMPs) to address the impact. This drainage study was prepared to request for variance from Section 5.10 Storage requiring detention for the proposed development to comply with the Weld County Engineering and Construction Criteria (WCECC) Manual Requirements, updated January 2021. The study summarizes findings from performing a hydrologic analysis of the project site to identify the potential stormwater impact from the proposed solar project and ensures that stormwater will not be concentrated, nor will it exceed historical flows when it leaves the parcel to County Road 54, protecting the existing infrastructure of Weld County. Proposed Project The proposed solar project will consist of pole mounted photovoltaic (PV) arrays. Ground disturbance under the panels will be minimal; thus, the existing perviousness of the soil will be maintained under the solar cells allowing infiltration. Rainfall runoff from the panels will not be concentrated and flow under the pole mounted PV panels matching the pre -development flow patterns. Additional improvements associated with this project are limited to gravel drives for vehicle access and concrete pads for distribution transformers (see Appendix A - Site plans C-301 & C-302). No public access or utility infrastructure improvements are anticipated at this time. FEMA Floodplains According to FEMA Flood Insurance Rate Map (FIRM) Panel Number 08123C1563E (Jan 20th, 2016), the project is located outside the mapped 100 -year floodplain. The risk of flooding within the project site is not anticipated. A copy of the FIRM is included in Appendix B. Onsite Drainage Currently, the existing site includes a ditch north of the project area responsible for irrigation. The soils in the area consist of hydrologic soil group (HSG) C and D soils given by the Natural Resources Conservation Service (NRCS — Appendix C). The proposed development footprint will Stormwater Drainage Study be in areas with soil types C&D. Based upon the drainage patterns, the site is analyzed as one drainage area labeled A, with an estimated area of 27.8 ac. External offsite flows follow the existing ditches and are not expected to affect the project site. See Appendix A for the drainage area maps and details. A hydrologic analysis was prepared using the Rational Method based upon requirements in the WCECC Manual. The analysis provided estimates of the peak flow rates for the 100 -year storm under both pre- and post -development conditions. The design rainfall depth for a 1 -hour, 100 - year storm is 2.71 inches based upon NOAA Atlas 14: Precipitation -Frequency Atlas. The Rational Method shown below was used to determine the peak flow rates from each drainage area. Existing conditions are undeveloped and determined to be "Greenbelt, Agriculture" which correlates to a 2% impervious value according to Table 5-2, Weld County Engineering and Construction Criteria. In Table 5-5, based off the soil type and impervious percentage, the existing area -weighted runoff coefficient was calculated to be 0.5095. Proposed conditions were determined to be the weighted average of "Greenbelt, Agriculture" (2% impervious), "Solar Facilities C&D Soils" (25% impervious), "Packed Gravel" (40% impervious), and "Conc. Pads" (100% impervious). Using the same process as before, the area -weighted runoff coefficient was calculated to be 0.5449. The drainage area imperviousness and resulting flow rates from pre - and post -development conditions are summarized below. See Appendix D for the runoff coefficient calculations. Q=C*I*A Where: Q- Runoff rate in cubic feet per second (cfs) /— Rainfall Intensity in inches per hour (in/hr) A - Area of the basin in acres (ac) Pre -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 27.8 0.5095 5.65 Post -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 27.8 0.5449 5.65 Stormwater Drainage Study 100 -year Runoff Calculation Results Drainage Area Pre -development Peak Flow (cis) Rate Post Peak -development Flow (cfs) Rate DIFFERENCE (cfs) A 80.13 85.61 5.48 Based upon the above results, the increase of impervious area has shown to result in some change (less than 7%) between the pre -development and post -development runoff peak flows. Because of this, a detention basin facility will not be proposed. Instead, grass swales will be introduced within the project site boundary to mitigate energy and attenuate the minimal flow increase from gravel roads and concrete pads. Erosion Control/Stormwater Management Plan Erosion control features such as silt fences and a grass swale (also mentioned above) will be installed on the site prior to construction activities. Such measures will be included in the erosion control plan and detail sheets within the final construction documents. Grass swale sizing calculations are summarized in Appendix E. Conclusion The variance request and attached drainage maps were produced in accordance with requirements from Weld County Engineering and Construction Criteria Manual, updated January 2021. The existing storm water flow characteristics are expected to remain unchanged and decrease in peak flow rate. A variance from detention is reasonable because the results ensure that stormwater will not be concentrated, nor it will exceed historical flows when it leaves the parcel to County Road 54. The proposed development will not alter historic drainage patterns or adjacent and downstream property owners. Stormwater Drainage Study References 1. Weld County, Weld County Engineering and Construction Criteria Manual, January 2021. 2. Web Soil Survey, Natural Resources Conservation Service, United States Department of Agriculture. Online at: http://websoilsurvey.nrcs.usda.gov, accessed January 2023. 3. Flood Insurance Rate Map, Weld County, Texas and Incorporated Areas, Jan 20, 2016, Map Number 08123C1563E, Federal Emergency Management Agency. 4. NOAA Atlas 14, Volume 11, Version 2. ESRI Maps. USGS. Sanja Perica, Sandra Pavlovic, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Orlan Wilhite. Appendices A. Site Plans C-301 & C-302 5-7 B. FEMA Firmette Map 8-9 C. NRCS Soil Layer Map 10-14 D. Rational Method Calculations 15-22 Existing Calculations 17-19 Proposed Calculations 20-22 E. Grass Swale Calculations 23-26 Stormwater Drainage Study Appendix A: SITE PLANS C301 & C302 Stormwater Drainage Study Appendix B: FEMA FIRMETTE MAP Stormwater Drainage Study Appendix C: NRCS SOIL LAYER MAP 40° 22' 49" N 40° 22' 37' N ti a Co 0 d- 104° 37' 4" W 532460 532520 532580 532640 532700 532760 532820 532880 532940 533000 104° 37' 4" W 532460 532520 532580 I Hydrologic Soil Group —Weld County, Colorado, Southern Part (Island Grove Drainage Area A Soil Map) 532640 532700 Map Scale: 1:2,730 if printed on A landscape (11" x 8.5") sheet Meters 0 40 80 160 240 Feet 0 100 200 400 600 Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 532760 532820 532880 532940 533000 104° 36' 39" W 104° 36 39" W 40° 22' 49" N 3 cp 4 40° 22'37'N ,b Natural Resources lain Conservation Service Web Soil Survey National Cooperative Soil Survey 8/31/2023 Page 1 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part (Island Grove Drainage Area A Soil Map) MAP LEGEND Area of Interest (AO!) Area of Interest (A01) ) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines 0 0 A A/D B B/D C C/D D Not rated or not available Soil Rating Points II O O O A A/D B B/D MAP INFORMATION C The soil surveys that comprise your AOI were mapped at 1:24,000. C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background ,; Aerial Photography Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Southern Part Survey Area Data: Version 21, Sep 1, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 8, 2021 Jun 12, 2021 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. ,b Natural Resources lain Conservation Service Web Soil Survey National Cooperative Soil Survey 8/31/2023 Page 2 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part Island Grove Drainage Area A Soil Map Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Altvan loam, percent slopes 0 to 1 B 0.1 0.4% 3 Aquolls and Aquents, gravelly substratum D 5.6 20.3% 22 Dacono 3 clay loam, percent slopes 1 to C 16.8 60.4% 41 Nunn clay percent loam, slopes 0 to 1 C 1.4 5.0% 42 Nunn clay loam, percent slopes 1 to 3 C 3.9 13.9% Totals for Area of Interest 27.8 100.0% e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 8/31/2023 Page 3 of 4 Hydrologic Soil Group —Weld County, Colorado, Southern Part Island Grove Drainage Area A Soil Map 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 (A/D, B/D, and CID). 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 (A/D, 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. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie -break Rule: Higher e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 8/31/2023 Page 4of4 Stormwater Drainage Study Appendix D: RATIONAL METHOD CALCULATIONS 1/27/23, 3:07 PM Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Greeley, Colorado, USA* Latitude: 40.3796°, Longitude: -104.6161° Elevation: 4640.41 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES 1"."ti1F ti Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) J Duration 1 2 5 10 25 50 100 200 I 500 1000 5 -min ! 0.243 (0.201-0.298) 0.294 (0.242-0.361) 0.391 (0.320-0.481) 0.484 (0.394-0.599) 0.631 (0.500-0.838) 0.760 (0.580-1.02) 0.901 (0.658-1.24) 1.06 (0.733-1.51) 1.29 (0.848-1.89) 1.47 (0.935-2.17) 10 -min 0.357 (0.294-0.437), 0.431 (0.355-0.529) 0.573 (0.469-0.705)I(0.577-0.878) 0.709 0.924 (0.732-1.23) 1.11 (0.850-1.49) 1.32 (0.964-1.82) 1.55 (1.07-2.20) 1.88 (1.24-2.76) 2.16 (1.37-3.18) 0.435 (0.358-0.533)1 0.526 (0.433-0.645) 0.698 (0.572-0.860) I + 1.36 (1.04-1.82) 1.61 (1.18-2.22) 1.89 (1.31-2.69) 2.30 (1.51-3.37) 2.6388) 30 -min 0.584 (0.481-0.716) 0.705 (0.580-0.865) 0.936 (0.767-1.15) 1.16 ' (0.944-1.44) ` 1.52 (1.20-2.01) I 1.83 (1.40-2.45) 2.17 (1.59-2.99) 2.55 (1.77-3.63) 3.11 (2.05-4.56) 3.57 (2.26-5.26) j 60 -min 0.726 (0.598-0.890) 0.864 (0.711-1.06) 1.14 (0.933-1.40) 1.41 (1.15-1.75) 1.86 (1.48-2.49) 2.26 (1.73-3.05) 2.71 (1.98-3.75) 3.21 (2.23-4.59) 3.95 (2.61-5.81) 4.57 (2.90-6.74) 2-h r 0.868 (0.721-1.06) I 1.02 (0.848-1.25) 1.34 (1.11-1.64) 1.67 (1.37-2.05) 2.21 (1.78-2.94) 3.87 4.80 5.58 (3.57-8.14) 3 -hr 0.951 (0.793-1.15) 1.11 (0.923-1.34) 1.44 (1.20-1.75) 1.79 (1.48-2.19) 2.38 (1.93-3.16) 2.92 (2.27-3.90) 3.53 (2.63-4.84) 4.22 (2.98-5.96) 5.26 (3.54-7.64) 6.13 (3.95-8.90) 6 -hr 1.09 (0.914-1.31) a 1.29 (1.08-1.54) 1.68 (1.40-2.02) 2.07 (1.72-2.51) 4 2.72 (2.21-3.56) 3.30 (2.58-4.35) 3.95 (2.96-5.34) 4.68 (3.33-6.52) 5.76 (3.91-8.26) 6.66 (4.34-9.58) 12 -hr 1.27 (1.07-1.51) 1.97 (1.66-2.35) 2.40 (2.01-2.89) 3.08 (2.50-3.94) 4.30 (3.24-5.73) 5.01 6.03 (4.12-8.53) 6.87 (4.52-9.78) 24 -hr 1.51 (1.29-1.78) Y 1.78 (1.51-2.10) 2.27 (1.92-2.69) 2.72 I (2.29-3.24) I 3.42 (2.80-4.32) i 4.02 (3.18-5.14) 4.67 (3.54-6.14) 5.38 (3.89-7.29) 6.40 (4.41-8.94) 7.23 (4.81-10.2) 2 -day 1.74 (1.49-2.04) i 2.05 (1.76-2.40) 2.60 (2.22-3.06) 3.09 I (2.62-3.65) i 3.83 (3.14-4.75) i 4.43 (3.53-5.58) 5.08 (3.88-6.57) 5.77 (4.20-7.71) 6.74 (4.68-9.29) 7.52 (5.06-10.5) i 3 -day 1.91 (1.64-2.22) 2.22 (1.91-2.59) M2.77 (2.38-3.24) 3.27 (2.78-3.84) 4.01 (3.30-4.95) 4.62L__ (3.70-5.78) 5.27 (4.05-6.78) 5.97 (4.37-7.92) 6.95 (4.86-9.52) 7.74 ll (5.24-10.7) 4 -day 2.03 (1.76-2.36)J 2.35 (2.03-2.73) 2.92 III4.16 (2.51-3.40) 3.42 1 (2.92-4.00) I (3.44-5.12) 4.78 (3.84-5.96) 5.43 (4.19-6.96) 6.13 (4.50-8.10) 7.12 (5.00-9.69) 7.90 (5.37-10.9) 7 -day a 2.31 (2.01-2.66) I 2.69 (2.34-3.10) 3.33 (2.88-3.86) 3.88 (3.34-4.52) I 4.67 (3.87-5.65) j 5.30 (4.27-6.51) 5.94 (4.60-7.51) 6.61 (4.88-8.62) 7.53 (5.32-10.1) 8.24 (5.65-11.3) i 10 -day 2.55 (2.22-2.92) 2.98 (2.60-3.42) 3.69 (3.20-4.25) 4.28 (3.69-4.95) 5.10 (4.23-6.11) 5.74 (4.63-6.99) 6.38 (4.95-7.99) 7.03 (5.21-9.09) 7.90 (5.60-10.5) 8.56 (5.90-11.6) 20 -day 3.26 (2.87-3.71) 3.77 (3.31-4.29) 4.59 (4.02-5.24) 5.26 (4.57-6.04) 6.16 (5.14-7.29) 6.84 (5.57-8.23) 7.51 (5.88-9.29) 8.17 (6.10-10.4) 9.02 (6.46-11.9) 9.65 (6.73-13.0) 30 -day a 3.83 (3.39-4.34) i 5.32 i (4.68-6.05) 6.06 I (5.29-6.92) I 7.04 (5.90-8.27) i 7.78 (6.36-9.29) 8.49 (6.68-10.4) 9.18 (6.90-11.6)1 10.1 (7.25-13.2) 10.7 (7.51-14.3) V 45 -day 4.53 (4.02-5.10) 5.20 (4.61-5.86) 6.27 (5.53-7.08) 7.11 (6.24-8.08) 8.22 (6.91-9.58) 9.04 (7.42-10.7) 9.82 (7.76-12.0) 10.6 (7.98-13.3) 11.5 (8.33-14.9) 12.2 (8.59-16.2) 60 -day 5.09 (4.53-5.71) 5.87 (5.22-6.59) 7.09 (6.28-7.98) 8.05 (7.08-9.10) 9.29 (7.83-10.8) 10.2 (8.39-12.0) 11.0 (8.75-13.4) 11.8 (8.97-14.8) 12.8 (9.31-16.5) 13.5 (9.57-17.9) 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/hdsc/pfds/pfds_printpage.html?lat=40.3796&Ion=-104.6161 &data=depth&units=english&series=pds 1/4 EXISTING CALCULATIONS CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 27.80 2.00 C II. Rainfall Information Design Storm Return Period, Tr = 01= C2= C3= P1= Acres ok A, B, C,orD I (inch/hr) = Cl * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.51 0.51 0.16 0.16 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration LEGEND L a Beginning, Flow D ircdio n C ate lime ht o adary NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage/ Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales/ Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output Flow Time Tf minutes output 0.0030 300 0.16 N/A 0.11 43.74 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = 1.89 5.65 5.00 0.32 58.66 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Rainfall Intensity at User -Defined Tc, I = 5.65 inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 102.40 17.85 17.85 26.76 80.13 80.13 cfs cfs cfs Island Grove EX 100 Yrs.xls, Tc and PeakQ 8/31/2023, 9:59 AM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR Illustration LEGEND: Flow Direction C atchm€nt D Ada ry Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. A C* CA input input input output B Soil 0.10 0.36 0.04 C Soil 22.10 0.51 11.27 D Soil 5.60 0.51 2.86 sum: 27.80 sum: 14.16 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5095 *See sheet "Design Info" for inperviousness-based runoff coefficient values. PROPOSED CALCUATIONS CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 27.80 25.00 C II. Rainfall Information Design Storm Return Period, Tr = 01= C2= C3= P1= Acres A, B, C, or D I (inch/hr) = C1 * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.56 0.54 0.28 0.28 Reach :3 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration - overland Reach 1 flow Reach 2 LEGEND (J Beginning Flow Direction Catenate at B o uit�d NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage! Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales! Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 0.0030 300 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output 0.28 N/A 0.13 Flow Time Tf minutes output 38.15 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = Rainfall Intensity at User -Defined Tc, I = 1.39 5.65 5.65 2.50 0.16 117.32 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 155.47 17.85 17.85 21.10 85.61 85.61 cfs cfs cfs Island Grove PR 100 Yrs.xls, Tc and PeakQ 8/31/2023, 10:00 AM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR Illustration LEGEND: Flow Dire Lion Gatos et Br 6 Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. A C* CA input input input output B Soil 0.10 0.36 0.04 C Soil 6.40 0.51 3.26 D Soil 1.94 0.51 0.99 Solar, C Soil 14.88 0.56 8.33 Solar, D Soil 3.66 0.56 2.05 Gravel Road 0.82 0.58 0.48 Concrete Pads 0.00 0.96 0.00 Sum: 27.80 Sum: 15.15 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5449 *See sheet "Design Info" for inperviousness-based runoff coefficient values. Island Grove PR 100 Yrs.xls, Weighted C 8/31/2023, 10:00 AM Stormwater Drainage Study Appendix E: GRASS SWALE CALCULATIONS T-2 Grass Swale RESIDUAL CAPACITY FOR LARGER FLOODS 1;,, • 4" (MIN) SANDY LOAM 6" MI IN _L 2-YR WSE 6" MI TRAPEZOIDAL SWALE SECTION NTS I RESIDUAL CAPACITY FOR LARGER FLOODS 2-YR WS•E 4'° MIN. SANDY LOAM 12" MIN. MIN. D 1.0' 12" MIN. (2-YR) 1.0 FPS !Y TRIANGULAR SIAN GULAR SWALE SECTION NTS CONCRETE COI I AR ENERGY DISSIPATION b ir. l' rf I PROVIDE DOUBLE CLEANOUTS WITH WATER TIGHT CAPS @150' O.O. USE 90* SWEEP OR (2) 45' BENDS (OFFSET FROM SWALE CENTERLINE TO AVOID IMPEDING FLOW WHEN USING A TRIANGULAR SECTION Design Example 1 4 MIN. GRADE CONTROL STRUCTURE BEYOND GRADE CONTROL STRUCTURE BEYOND UNDERDRAIN AND SANDY LOAM RECOMMENDED FOR LONGITUDINAL SLOPES < 2.0%. 4" SLOTTED PIPE MEETING TABLE 05-3 WITH CDOT CLASS C FILTER MATERIAL ALL AROUND OR PERFORATED HOPE PIPE WITH AASHTO #67 ALL AROUND CONTAINED WITHIN CEOTEXTILE FABRIC. ASTM D4751-AOS US STD. SIEVE #50 TO 7a, ASTM D4533 MIN. TRAPEZOIDAL TEAR STRENGTH 100 X 60 LBS, MINIMUM COE SPECIFIED OPEN AREA OF 4%. GRADE CONTROL EXTEND GRADE CTROL STRUCTURE STRUCTURES INTO ONTHE BANK A MIN. OS ABOVE THE 2-YR WSE Ii UNDERDRAIN ENSURE ACCESS TO OUTLET BY CLEAN OUT OR OTHER ACCESSIBLE STRUCTURE SWALE PROFILE NITS Figure GS -1. Grass Swale Profile and Sections The UD-BMP workbook, designed as a tool for both designer and reviewing agency is available at www.udfcd.org. This section provides a completed design form from this workbook as an example. GS -6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Hydraulic Analysis Report Project Data Project Title: Designer: Project Date: Monday, January 30, 2023 Project Units: U.S. Customary Units Notes: Channel Analysis: Swale A Notes: input Parameters Channel Type: Trapezoidal Side Slope 1 (Z1): 3.0000 ft/ft Side Slope 2 (Z2): 3.0000 ft/ft Channel Width 1.00 ft Longitudinal Slope: 0.0070 ft/ft Manning's n: 0.0350 Depth 1.0000 ft Result Parameters Flow 9.4932 cfs Area of Flow 4.0000 ft^2 Wetted Perimeter 7.3246 ft Hydraulic Radius 0.5461 ft Average Velocity 2.3733 ft/s Top Width 7.0000 ft Froude Number: 0.5533 Critical Depth 0.7608 ft Critical Velocity 3.8014 ft/s Critical Slope: 0.0247 ft/ft Critical Top Width 5.56 ft Calculated Max Shear Stress 0.43681b/ft^2 Calculated Avg Shear Stress 0.2385 lb/ft^2 'TRC Stormwater Drainage Study CLOUDBREAK ENERGY PARTNERS Date: To: From: Project: Subject: 03/10/2023 Cloudbreak Energy Allyson Williamson, TRC Companies 700 Highlander Blvd., Suite 210 Arlington, TX 76015 Island Grove Solar Project On -Site Drainage Study PRELIMINARY FOR INTERIM REVIEW ONLY. NOT FOR PERMITTING, BIDDING, NOR CONSTRUCTION. Prepared by or under the Direct Supervision of: Allyson Williamson, P.E. 60360 "03/10/2023" Cloudbreak Energy is pursuing the development of the Island Grove project, a photovoltaic energy generation facility at a 23.8 -acre site in Weld County, Colorado, alongside Co Rd 54 (See Appendix A — Site Plans C-301 & C-302). The existing site currently is used for agricultural purposes with approximately 1% slopes. This drainage study was prepared to summarize findings from performing a hydrologic analysis of the project site to identify the potential stormwater impact from the proposed solar project and develop appropriate drainage best management practices (BMPs) to address the impact. This drainage study was prepared to comply with the requirements from the Weld County Engineering and Construction Criteria (WCECC) Manual, updated January 2021. Proposed Project The proposed solar project will consist of pole mounted photovoltaic (PV) arrays. Ground disturbance under the panels will be minimal; thus, the existing perviousness of the soil will be maintained under the solar cells allowing infiltration. Rainfall runoff from the panels will not be concentrated and flow under the pole mounted PV panels matching the pre -development flow patterns. Additional improvements associated with this project are limited to gravel drives for vehicle access and concrete pads for distribution transformers (see Appendix A - Site plans C-301 & C-302). No public access or utility infrastructure improvements are anticipated at this time. FEMA Floodplains According to FEMA Flood Insurance Rate Map (FIRM) Panel Number 08123C1563E (Jan 20th, 2016), the project is located outside the mapped 100 -year floodplain. The risk of flooding within the project site is not anticipated. A copy of the FIRM is included in Appendix B. Onsite Drainage Currently, the existing site includes a ditch north of the project area responsible for irrigation. The soils in the area consist of hydrologic soil group (HSG) C and D soils given by the Natural Resources Conservation Service (NRCS — Appendix C). The proposed development footprint will be in areas with soil types C&D. Based upon the drainage patterns, the site is analyzed as one drainage area labeled A, with an estimated area of 23.8 ac. External offsite flows follow the existing ditches and are not expected to affect the project site. See Appendix A for the drainage area maps and details. Stormwater Drainage Study A hydrologic analysis was prepared using the Rational Method based upon requirements in the WCECC Manual. The analysis provided estimates of the peak flow rates for the 100 -year storm under both pre- and post -development conditions. The design rainfall depth for a 1 -hour, 100 - year storm is 2.71 inches based upon NOAA Atlas 14: Precipitation -Frequency Atlas. The Rational Method shown below was used to determine the peak flow rates from each drainage area. Existing conditions are undeveloped and determined to be "Greenbelt, Agriculture" which correlates to a 2% impervious value according to Table 5-2, Weld County Engineering and Construction Criteria. In Table 5-5, based off the soil type and impervious percentage, the runoff calculation was 0.51, respectively. Proposed conditions were determined to be the weighted average of "Greenbelt, Agriculture" (2% impervious), "Solar Facilities C&D Soils" (25% impervious), "Packed Gravel" (40% impervious), and "Conc. Pads" (100% impervious). Using the same process as before, the runoff coefficient was weighted to be 0.5702, respectively. The drainage area imperviousness and resulting flow rates from pre -and post -development conditions are summarized below. See Appendix D for the runoff coefficient calculations. Q=C*I*A Where: Q- Runoff rate in cubic feet per second (cfs) / Rainfall Intensity in inches per hour (in/hr) A - Area of the basin in acres (ac) Pre -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 23.8 0.51 5.65 Post -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 23.8 0.5702 5.65 Stormwater Drainage Study 100 -year Runoff Calculation Results Drainage Area Pre -development Peak Flow (cfs) Rate Post Peak -development Flow (cfs) Rate DIFFERENCE (cfs) A 68.6 76.7 8.10 Based upon the above results, the increase of impervious area has shown to result in some change (less than 12%) between the pre -development and post -development runoff peak flows. Because of this, a detention basin facility will not be proposed. Instead, grass swales will be introduced within the project site boundary to mitigate energy and attenuate the minimal flow increase from gravel roads and concrete pads. Erosion Control/Stormwater Management Plan Erosion control features such as silt fences and a grass swale (also mentioned above) will be installed on the site prior to construction activities. Such measures will be included in the e rosion control plan and detail sheets within the final construction documents. Grass swale sizing calculations are summarized in Appendix E. Conclusion The drainage study and attached drainage maps were produced in accordance with requirements from Weld County Engineering and Construction Criteria (WCECC) Manual, u pdated January 2021. The existing stormwater flow characteristics are expected to remain u nchanged and increases in peak flow rates have been proven to be negligible. A basin type of stormwater detention is not be necessary. Improvements proposed with the project site are limited to a gravel paved drive and one small concrete distribution transformer pads. No public access or utility infrastructure improvements are anticipated at this time. The proposed development will not alter historic drainage patterns and adjacent and downstream property owners. Stormwater Drainage Study References 1. Weld County, Weld County Engineering and Construction Criteria Manual, January 2021. 2. Web Soil Survey, Natural Resources Conservation Service, United States Department of Agriculture. Online at: http://websoilsurvey.nrcs.usda.gov, accessed Januar 2023. 3. Flood Insurance Rate Map, Weld County, Texas and Incorporated Areas, Jan 20, 2016, Map Number 08123C1563E, Federal Emergency Management Agency. 4. NOAA Atlas 14, Volume 11, Version 2. ESRI Maps. USGS. Sanja Perica, Sandra Pavlovic, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Orlan Wilhite. Appendices A. Site Plans C-301 & C-302 5-7 B. FEMA Firmette Map 8-9 C. NRCS Soil Layer Map 10-14 D. Rational Method Calculations 15-29 Existing Calculations 16 Proposed Calculations 23 E. Grass Swale Calculations 30-33 Stormwater Drainage Study Appendix A: SITE PLANS C301 & C302 Stormwater Drainage Study Appendix B: FEMA FIRMETTE MAP Stormwater Drainage Study Appendix C: NRCS SOIL LAYER MAP 40° 22' 49" N 1 9 0 ti 4 40° 22' 37' N 4 104° 37'3"W N Hydrologic Soil Group —Weld County, Colorado, Southern Part (IslandGrove_DABoundary) 532640 Map Scale: 1:2,600 if printed on A landscape (11" x 8.5") sheet Meters 0 35 70 140 210 Met 0 100 200 400 600 Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 104° 36' 39" W 40° 22' 49" N 0 N- co 4 0 4 co 40° 22'37'N 1040 36' 39" W ,b Natural Resources as Conservation Service Web Soil Survey National Cooperative Soil Survey 1/27/2023 Page 1 of 5 Hydrologic Soil Group —Weld County, Colorado, Southern Part (IslandGrove_DABoundary) MAP LEGEND Area of Interest (AO!) Area of Interest (A01) ) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines 0 0 A A/D B B/D C C/D D Not rated or not available Soil Rating Points II O O O A A/D B B/D MAP INFORMATION C The soil surveys that comprise your AOI were mapped at 1:24,000. C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background ,; Aerial Photography Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Southern Part Survey Area Data: Version 21, Sep 1, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 8, 2021 Jun 12, 2021 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. ,b Natural Resources lain Conservation Service Web Soil Survey National Cooperative Soil Survey 1/27/2023 Page 2of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Altvan loam, percent slopes 0 to 1 B 0.0 0.0% 3 Aquolls and Aquents, gravelly substratum D 3.8 16.1% 22 Dacono 3 clay loam, percent slopes 1 to C 15.6 65.5% 41 Nunn clay percent loam, slopes 0 to 1 C 1.0 4.2% 42 Nunn clay loam, percent slopes 1 to 3 C 3.4 14.2% Totals for Area of Interest 23.8 100.0% e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 3of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary 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 (A/D, B/D, and CID). 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 (A/D, 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. Rating Options Aggregation Method: Dominant Condition e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 4of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole. A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not. For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods. The aggregation method "Dominant Condition" first groups like attribute values for the components in a map unit. For each group, percent composition is set to the sum of the percent composition of all components participating in that group. These groups now represent "conditions" rather than components. The attribute value associated with the group with the highest cumulative percent composition is returned. If more than one group shares the highest cumulative percent composition, the corresponding "tie -break" rule determines which value should be returned. The "tie -break" rule indicates whether the lower or higher group value should be returned in the case of a percent composition tie. The result returned by this aggregation method represents the dominant condition throughout the map unit only when no tie has occurred. Component Percent Cutoff. None Specified Components whose percent composition is below the cutoff value will not be considered. If no cutoff value is specified, all components in the database will be considered. The data for some contrasting soils of minor extent may not be in the database, and therefore are not considered. Tie -break Rule: Higher The tie -break rule indicates which value should be selected from a set of multiple candidate values, or which value should be selected in the event of a percent composition tie. e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 5of5 Stormwater Drainage Study Appendix D: RATIONAL METHOD CALCULATIONS 1/27/23, 3:07 PM Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Greeley, Colorado, USA* Latitude: 40.3796°, Longitude: -104.6161° Elevation: 4640.41 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES 1"."ti1F ti Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) J Duration 1 2 5 10 25 50 100 200 I 500 1000 5 -min ! 0.243 (0.201-0.298) 0.294 (0.242-0.361) 0.391 (0.320-0.481) 0.484 (0.394-0.599) 0.631 (0.500-0.838) 0.760 (0.580-1.02) 0.901 (0.658-1.24) 1.06 (0.733-1.51) 1.29 (0.848-1.89) 1.47 (0.935-2.17) 10 -min 0.357 (0.294-0.437), 0.431 (0.355-0.529) 0.573 (0.469-0.705)I(0.577-0.878) 0.709 0.924 (0.732-1.23) 1.11 (0.850-1.49) 1.32 (0.964-1.82) 1.55 (1.07-2.20) 1.88 (1.24-2.76) 2.16 (1.37-3.18) 0.435 (0.358-0.533)1 0.526 (0.433-0.645) 0.698 (0.572-0.860) I + 1.36 (1.04-1.82) 1.61 (1.18-2.22) 1.89 (1.31-2.69) 2.30 (1.51-3.37) 2.6388) 30 -min 0.584 (0.481-0.716) 0.705 (0.580-0.865) 0.936 (0.767-1.15) 1.16 ' (0.944-1.44) ` 1.52 (1.20-2.01) I 1.83 (1.40-2.45) 2.17 (1.59-2.99) 2.55 (1.77-3.63) 3.11 (2.05-4.56) 3.57 (2.26-5.26) j 60 -min 0.726 (0.598-0.890) 0.864 (0.711-1.06) 1.14 (0.933-1.40) 1.41 (1.15-1.75) 1.86 (1.48-2.49) 2.26 (1.73-3.05) 2.71 (1.98-3.75) 3.21 (2.23-4.59) 3.95 (2.61-5.81) 4.57 (2.90-6.74) 2-h r 0.868 (0.721-1.06) I 1.02 (0.848-1.25) 1.34 (1.11-1.64) 1.67 (1.37-2.05) 2.21 (1.78-2.94) 3.87 4.80 5.58 (3.57-8.14) 3 -hr 0.951 (0.793-1.15) 1.11 (0.923-1.34) 1.44 (1.20-1.75) 1.79 (1.48-2.19) 2.38 (1.93-3.16) 2.92 (2.27-3.90) 3.53 (2.63-4.84) 4.22 (2.98-5.96) 5.26 (3.54-7.64) 6.13 (3.95-8.90) 6 -hr 1.09 (0.914-1.31) a 1.29 (1.08-1.54) 1.68 (1.40-2.02) 2.07 (1.72-2.51) 4 2.72 (2.21-3.56) 3.30 (2.58-4.35) 3.95 (2.96-5.34) 4.68 (3.33-6.52) 5.76 (3.91-8.26) 6.66 (4.34-9.58) 12 -hr 1.27 (1.07-1.51) 1.97 (1.66-2.35) 2.40 (2.01-2.89) 3.08 (2.50-3.94) 4.30 (3.24-5.73) 5.01 6.03 (4.12-8.53) 6.87 (4.52-9.78) 24 -hr 1.51 (1.29-1.78) Y 1.78 (1.51-2.10) 2.27 (1.92-2.69) 2.72 I (2.29-3.24) I 3.42 (2.80-4.32) i 4.02 (3.18-5.14) 4.67 (3.54-6.14) 5.38 (3.89-7.29) 6.40 (4.41-8.94) 7.23 (4.81-10.2) 2 -day 1.74 (1.49-2.04) i 2.05 (1.76-2.40) 2.60 (2.22-3.06) 3.09 I (2.62-3.65) i 3.83 (3.14-4.75) i 4.43 (3.53-5.58) 5.08 (3.88-6.57) 5.77 (4.20-7.71) 6.74 (4.68-9.29) 7.52 (5.06-10.5) i 3 -day 1.91 (1.64-2.22) 2.22 (1.91-2.59) M2.77 (2.38-3.24) 3.27 (2.78-3.84) 4.01 (3.30-4.95) 4.62L__ (3.70-5.78) 5.27 (4.05-6.78) 5.97 (4.37-7.92) 6.95 (4.86-9.52) 7.74 ll (5.24-10.7) 4 -day 2.03 (1.76-2.36)J 2.35 (2.03-2.73) 2.92 III4.16 (2.51-3.40) 3.42 1 (2.92-4.00) I (3.44-5.12) 4.78 (3.84-5.96) 5.43 (4.19-6.96) 6.13 (4.50-8.10) 7.12 (5.00-9.69) 7.90 (5.37-10.9) 7 -day a 2.31 (2.01-2.66) I 2.69 (2.34-3.10) 3.33 (2.88-3.86) 3.88 (3.34-4.52) I 4.67 (3.87-5.65) j 5.30 (4.27-6.51) 5.94 (4.60-7.51) 6.61 (4.88-8.62) 7.53 (5.32-10.1) 8.24 (5.65-11.3) i 10 -day 2.55 (2.22-2.92) 2.98 (2.60-3.42) 3.69 (3.20-4.25) 4.28 (3.69-4.95) 5.10 (4.23-6.11) 5.74 (4.63-6.99) 6.38 (4.95-7.99) 7.03 (5.21-9.09) 7.90 (5.60-10.5) 8.56 (5.90-11.6) 20 -day 3.26 (2.87-3.71) 3.77 (3.31-4.29) 4.59 (4.02-5.24) 5.26 (4.57-6.04) 6.16 (5.14-7.29) 6.84 (5.57-8.23) 7.51 (5.88-9.29) 8.17 (6.10-10.4) 9.02 (6.46-11.9) 9.65 (6.73-13.0) 30 -day a 3.83 (3.39-4.34) i 5.32 i (4.68-6.05) 6.06 I (5.29-6.92) I 7.04 (5.90-8.27) i 7.78 (6.36-9.29) 8.49 (6.68-10.4) 9.18 (6.90-11.6)1 10.1 (7.25-13.2) 10.7 (7.51-14.3) V 45 -day 4.53 (4.02-5.10) 5.20 (4.61-5.86) 6.27 (5.53-7.08) 7.11 (6.24-8.08) 8.22 (6.91-9.58) 9.04 (7.42-10.7) 9.82 (7.76-12.0) 10.6 (7.98-13.3) 11.5 (8.33-14.9) 12.2 (8.59-16.2) 60 -day 5.09 (4.53-5.71) 5.87 (5.22-6.59) 7.09 (6.28-7.98) 8.05 (7.08-9.10) 9.29 (7.83-10.8) 10.2 (8.39-12.0) 11.0 (8.75-13.4) 11.8 (8.97-14.8) 12.8 (9.31-16.5) 13.5 (9.57-17.9) 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/hdsc/pfds/pfds_printpage.html?lat=40.3796&Ion=-104.6161 &data=depth&units=english&series=pds 1/4 EXISTING CALCULATIONS PEAK RUNOFF PREDICTION BY THE RATIONAL METHOD Version 1.02a, Released August 2005 Urban Drainage and Flood Control District Denver, Colorado Purpose: Function: Content: Intro Weighted C Tc and PeakQ Design Info Notation Acknowledgements: Comments? Revisions? This workbook applies the Rational Method to estimate stormwater runoff and peak flows from small urban catchments, i.e., typically less than 90 acres. 1. To apply the area -weighting method to calculate the representative runoff coefficient C for a catchment. 2. To calculate the time of concentration, and then compare with the empirical time of concentration limit used for the Denver region. The smaller one is recommended as the rainfall duration for use with the Rational Method. 3. To calculate the design rainfall intensity and peak flow rate. The workbook consists of the following five sheets: Describes the purpose of each sheet in the workbook. Applies the area -weighting method to determine the runoff C. Calculates Tc and Q -peak. Provides the recommended runoff C's for various land uses. Defines the variables used. Spreadsheet Development Team: Dr. James C.Y. Guo, P.E. Professor, Department of Civil Engineering University of Colorado at Denver Ken A. MacKenzie, P.E. Urban Drainage and Flood Control District Wright Water Engineers, Inc. Denver, Colorado Direct all comments regarding this spreadsheet workbook to: UDFCD E -Mail Check for revised versions of this or any other workbook at: Downloads Island Grove EX 100 Yrs.xls, Intro 1/31/2023, 5:00 PM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR Illustration rEr : Flow Direction Catch ent B arundary Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. A C* CA input input input output C Soil 20.00 I 0.51 10.20 D Soil 3.80 0.51 1.94 I I sum: 2 23.80 sum: 1 12.14 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5100 *See sheet "Design Info" for inperviousness-based runoff coefficient values. Island Grove EX 100 Yrs.xls, Weighted C 1/31/2023, 5:00 PM CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 23.80 2.00 C II. Rainfall Information Design Storm Return Period, Tr = 01 = C2= C3= P1= Acres ok A, B, C, or D I (inch/hr) = C1 * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.51 0.51 0.16 0.16 Reach 3 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration Reach 21. - Reach 1 o tre rland flow LEGEND 0 B,eginnhkg Flow Dirertion C at: nt B o undary NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage/ Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales/ Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output Flow Time Tf minutes output 0.0030 300 0.16 N/A 0.11 43.74 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = Rainfall Intensity at User -Defined Tc, I = 1.89 5.65 5.65 5.00 0.32 58.66 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 102.40 17.85 17.85 22.91 68.60 68.60 cfs cfs cfs Island Grove EX 100 Yrs.xls, Tc and PeakQ 1/31/2023, 5:00 PM Runoff Coefficient vs. Watershed Imperviousness Based on Runoff Coefficient estimating equation published by Urbonas, et.al. (1990) & WEF (1998) Basic equation for NRCS Soil Types C & D: Cep = K CD + (0.858 */ i - 0.786 *12 + (1.774 *i + 0.04) Basic equation for NRCS Soil Type A: C_4 = K 4 + (1.31 *i3 - 1.44 *i 2 + 1.135 *i - 0.12) in which use values for C-4 > 0 in which: i = Ic,/100, imperviousness ratio I, = watershed imperviousness in percent CA = Runoff Coefficient for NRCS Soil Type A KA = Correction factor for CA when the storm return period is greater than 2 -years CCn A -CD = Runoff Coefficient for NRCS Soil Types C and D = Correction factor for CCD when the storm return period is greater than 2 -years Values of Correction Factors Kc•D & KA NRCS Stone Return Period Soil Types, • 2-}n 5-yr 10-yr 25-yr 50-yr 100-yr C & D 0.00 [-0.10*i+0.11] [-0.18*i-0.21] [-0.28*i+0.33] [-0.33*i-0.40] [-0.39*i+0.46] A 0.00 [-0.08*i+0.09] [-0.1 t*/ -0.17] [-0.19*i+0.24] [-0.22*/ 0.28] [-0.25*i+0.32] Values of Runoff Coefficient C CD Values of Runoff Coefficient C,4 Imp en: . 1 Te C mid D NRCS Hydrologic Soil Groups Type A NRCS Hydrologic Soils Group tRau° 11! 2-yr >-yT 1 U -n 2l-yl. >U-yT 1 UU-yT 2-yr l-yi- 1O -n 2.5-yT :)U -,,I 1 Ull-,1* 0.00 0.04 0.15 0.25 0.37 0.44 0.50 -0.12 -0.03 0.05 0.12 0.16 0.20 0.05 0.08 0.18 0.28 0.39 0.46 0.52 -0.07 0.02 0.10 0.16 0.20 0.24 0.10 0.11 0.21 0.30 0.41 0.48 0.53 -0.02 0.06 0.14 0.20 0.24 0.28 0.15 0.14 0.24 0.32 0.43 0.49 0.54 0.02 0.10 0.17 0.23 0.27 0.30 0.20 0.17 0.26 0.34 0.44 0.50 0.55 0.06 0.13 0.20 0.26 0.30 0.33 0.25 0.20 0.28 0.36 0.46 0.52 0.56 0.09 0.16 0.23 0.29 0.32 0.35 0.30 0.22 0.30 0.38 0.47 0.53 0.57 0.13 0.19 0.25 0.31 0.34 0.37 0.35 0.25 0.33 0.40 0.48 0.54 0.57 0.16 0.22 0.28 0.33 0.36 0.39 0.40 0.28 0.35 0.42 0.50 0.55 0.58 0.19 0.25 0.30 0.35 0.38 0.41 0.45 0.31 0.37 0.44 0.51 0.56 0.59 0.22 0.27 0.33 0.37 0.40 0.43 0.50 0.34 0.40 0.46 0.53 0.57 0.60 0.25 0.30 0.35 0.40 0.42 0.45 0.55 0.37 0.43 0.48 0.55 0.59 0.62 0.29 0.33 0.38 0.42 0.45 0.47 0.60 0.41 0.46 0.51 0.57 0.61 0.63 0.33 0.37 0.41 0.45 0.47 0.50 0.65 _ 0.45 0.49 0.54 0.59 0.63 0.65 0.37 0.41 0.45 0.49 0.51 0.53 0.70 0.49 0.53 0.57 0.62 0.66 0.68 0.42 0.45 0.49 0.53 0.54 0.56 0.75 0.54 0.58 0.62 0.66 0.69 0.71 0.47 0.50 0.54 0.57 0.59 0.61 0.80 0.60 0.63 0.66 0.70 0.73 0.74 0.54 0.56 0.60 0.63 0.64 0.66 0.85 0.66 0.68 0.71 0.75 0.78 0.79 0.61 0.63 0.66 0.69 0.70 0.72 0.90 0.73 0.75 0.77 0.80 0.83 0.83 0.69 0.71 0.73 0.76 0.77 0.79 0.95 0.80 0.82 0.84 0.87 0.89 0.89 0.78 0.80 0.82 0.84 0.85 0.86 1.00 0.89 0.90 0.92 0.94 0.96 0.96 0.89 0.90 0.92 0.94 0.95 0.96 Runoff Coefficient Notes: 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0 For Type B Soils. use the average of coefficients Cu) and CA . When the Runoff Coefficient in above table is < 0, use 0. When compositing the Runoff Coefficient for different soil typ Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soils C & D 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Watershed Impervious Ratio 1.0 es, use the table values above regardless if they are < 0 100-yr 4 25-yr 10—yr ;sr 5—yr 2—yr Runoff Coefficient Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soil A 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 =%.J 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Watershed Impervious Ratio 100-yr t 25-yr • 10-yr 5-yr 2-yr Page 4 I. One -hr Precipitation Values for Metro Denver Area Return period in years 2 5 10 50 100 Depth in inches 0.93 1.35 1.61 2.20 2.60 II. Recommended Runoff Coefficients for Metro Denver Land Use or Surface Characteristics Percent Imper- viousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family " Multiunit (detached) 60 Multiunit (attached) 75 Half -acre lot or larger Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks. cemeteries: 5 Playgrounds: 10 Schools: 50 Railroad yard areas: 15 Undeveloped areas: Historical Flow Analysis 2 Greenbelts. agricultural Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Driveways and sidewalks: 90 Roofs: 90 Lawns. sandy soil 0 Lawns. clayey soil 0 *Refer to Figures RO-3 through RO-5 in Runoff Chapter of USDCM. Page 5 List of Variables A= C= C1, O2, and C3 C5 I= ID = L= S= P1 = Tc Td Tf Tr Qp V= watershed area in acres runoff coefficient coefficients in IDF formula 5-yr runoff coefficient rainfall intensity in inches/hour user defined identification number flow length in ft slope for flow length in ft/ft one hour precipitation value in inches time of concentration in minutes design rainfall duration in minutes flow time in minutes return period in years peak runoff rate in cfs flow velocity in ft/second Island Grove EX 100 Yrs.xls, Notation 1/31/2023, 5:00 PM PROPOSED CALCUATIONS PEAK RUNOFF PREDICTION BY THE RATIONAL METHOD Version 1.02a, Released August 2005 Urban Drainage and Flood Control District Denver, Colorado Purpose: Function: Content: Intro Weighted C Tc and PeakQ Design Info Notation Acknowledgements: Comments? Revisions? This workbook applies the Rational Method to estimate stormwater runoff and peak flows from small urban catchments, i.e., typically less than 90 acres. 1. To apply the area -weighting method to calculate the representative runoff coefficient C for a catchment. 2. To calculate the time of concentration, and then compare with the empirical time of concentration limit used for the Denver region. The smaller one is recommended as the rainfall duration for use with the Rational Method. 3. To calculate the design rainfall intensity and peak flow rate. The workbook consists of the following five sheets: Describes the purpose of each sheet in the workbook. Applies the area -weighting method to determine the runoff C. Calculates Tc and Q -peak. Provides the recommended runoff C's for various land uses. Defines the variables used. Spreadsheet Development Team: Dr. James C.Y. Guo, P.E. Professor, Department of Civil Engineering University of Colorado at Denver Ken A. MacKenzie, P.E. Urban Drainage and Flood Control District Wright Water Engineers, Inc. Denver, Colorado Direct all comments regarding this spreadsheet workbook to: UDFCD E -Mail Check for revised versions of this or any other workbook at: Downloads Island Grove PR 100 Yrs.xls, Intro 1/31/2023, 5:03 PM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR Illustration 1..E GIIND : Flow Direction Catchm eat Boundary Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. _ A C* CA input input input output C Soil 19.27 0.56 10.79 D Soil 3.80 0.56 2.13 Packed Gravel _ 0.72 0.89 _ 0.64 Conc. Pads 0.01 0.96 0.01 Sum: 23.80 sum: 13.57 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5702 *See sheet "Design Info" for inperviousness-based runoff coefficient values. Island Grove PR 100 Yrs.xls, Weighted C 1/31/2023, 5:03 PM CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 23.80 25.00 C II. Rainfall Information Design Storm Return Period, Tr = 01 = C2= C3= P1= Acres ok A, B, C, or D I (inch/hr) = C1 * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.56 0.57 0.28 - is Reach :3 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration Reach 2 Reach 1 overland flow LEGEND Beginning Flow Direc do n C aic lune of B o undary NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage/ Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales/ Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output Flow Time Tf minutes output 0.0030 300 0.28 N/A 0.13 38.02 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = Rainfall Intensity at User -Defined Tc, I = 1.39 5.65 5.65 2.50 0.16 117.32 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 155.34 17.85 17.85 18.91 76.70 76.70 cfs cfs cfs Island Grove PR 100 Yrs.xls, Tc and PeakQ 1/31/2023, 5:03 PM Runoff Coefficient vs. Watershed Imperviousness Based on Runoff Coefficient estimating equation published by Urbonas, et.al. (1990) & WEF (1998) Basic equation for NRCS Soil Types C & D: Cep = Ka) + (0.858 *i3 - 0.786 *(+ 0.774 *i + 0.04) Basic equation for NRCS Soil Type A: C_4 = K .r + (1.31 *i3 - 1.44 *i 2 + 1.135 *i - 0.12) in which use values for C-4> 0 in which: i = Ic,/100, imperviousness ratio I, = watershed imperviousness in percent CA = Runoff Coefficient for NRCS Soil Type A KA = Correction factor for CA when the storm return period is greater than 2 -years CCn A -CD = Runoff Coefficient for NRCS Soil Types C and D = Correction factor for CCD when the storm return period is greater than 2 -years Values of Correction Factors KGD & KA NRCS Stone Return Period Soil Types, • 2-}n 5-yr 10-yr 25-yr 50-yr 100-yr C & D 0.00 [-0.10*i+0.11] [-0.18*i-0.21] [-0.28*i+0.33] [-0.33*i-0.40] [-0.39*i+0.46] A 0.00 [-0.08*i+0.09] [-0.1 t*/ -0.17] [-0.19*i+0.24] [-0.22*/ 0.28] [-0.25*i+0.32] Values of Runoff Coefficient C CD Values of Runoff Coefficient C,4 Imp en: . 1 Te C mid D NRCS Hydrologic Soil Groups Type A NRCS Hydrologic Soils Group tRau° 11! 2-yr :)-yr 1 U-yr 2l-yl. >U-yr 100-yr 2-yr l-yi- 10 -NT 2.5-yr :)U-yT 1 Ull-n 0.00 0.04 0.15 0.25 0.37 0.44 0.50 -0.12 -0.03 0.05 0.12 0.16 0.20 0.05 0.08 0.18 0.28 0.39 0.46 0.52 -0.07 0.02 0.10 0.16 0.20 0.24 0.10 0.11 0.21 0.30 0.41 0.48 0.53 -0.02 0.06 0.14 0.20 0.24 0.28 0.15 0.14 0.24 0.32 0.43 0.49 0.54 0.02 0.10 0.17 0.23 0.27 0.30 0.20 0.17 0.26 0.34 0.44 0.50 0.55 0.06 0.13 0.20 0.26 0.30 0.33 0.25 0.20 0.28 0.36 0.46 0.52 0.56 0.09 0.16 0.23 0.29 0.32 0.35 0.30 0.22 0.30 0.38 0.47 0.53 0.57 0.13 0.19 0.25 0.31 0.34 0.37 0.35 0.25 0.33 0.40 0.48 0.54 0.57 0.16 0.22 0.28 0.33 0.36 0.39 0.40 0.28 0.35 0.42 0.50 0.55 0.58 0.19 0.25 0.30 0.35 0.38 0.41 0.45 0.31 0.37 0.44 0.51 0.56 0.59 0.22 0.27 0.33 0.37 0.40 0.43 0.50 0.34 0.40 0.46 0.53 0.57 0.60 0.25 0.30 0.35 0.40 0.42 0.45 0.55 0.37 0.43 0.48 0.55 0.59 0.62 0.29 0.33 0.38 0.42 0.45 0.47 0.60 0.41 0.46 0.51 0.57 0.61 0.63 0.33 0.37 0.41 0.45 0.47 0.50 0.65 _ 0.45 0.49 0.54 0.59 0.63 0.65 0.37 0.41 0.45 0.49 0.51 0.53 0.70 0.49 0.53 0.57 0.62 0.66 0.68 0.42 0.45 0.49 0.53 0.54 0.56 0.75 0.54 0.58 0.62 0.66 0.69 0.71 0.47 0.50 0.54 0.57 0.59 0.61 0.80 0.60 0.63 0.66 0.70 0.73 0.74 0.54 0.56 0.60 0.63 0.64 0.66 0.85 0.66 0.68 0.71 0.75 0.78 0.79 0.61 0.63 0.66 0.69 0.70 0.72 0.90 0.73 0.75 0.77 0.80 0.83 0.83 0.69 0.71 0.73 0.76 0.77 0.79 0.95 0.80 0.82 0.84 0.87 0.89 0.89 0.78 0.80 0.82 0.84 0.85 0.86 1.00 0.89 0.90 0.92 0.94 0.96 0.96 0.89 0.90 0.92 0.94 0.95 0.96 Runoff Coefficient 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Notes: For Type B Soils. use the average of coefficients Cu) and CA . When the Runoff Coefficient in above table is < 0, use 0. When compositing the Runoff Coefficient for different soil typ Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soils C & D 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Watershed Impervious Ratio 1.0 es, use the table values above regardless if they are < 0 100-yr —•-25-yr 10-yr a 5-yr 2-yr Runoff Coefficient Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soil A 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Watershed Impervious Ratio 100-yr 25-yr 10-yr 5 yr 2-yr Page 4 I. One -hr Precipitation Values for Metro Denver Area Return period in years 2 5 10 50 100 Depth in inches 0.93 1.35 1.61 2.20 2.60 II. Recommended Runoff Coefficients for Metro Denver Land Use or Surface Characteristics Percent Imper- viousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family " Multiunit (detached) 60 Multiunit (attached) 75 Half -acre lot or larger Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks. cemeteries: 5 Playgrounds: 10 Schools: 50 Railroad yard areas: 15 Undeveloped areas: Historical Flow Analysis 2 Greenbelts. agricultural Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Driveways and sidewalks: 90 Roofs: 90 Lawns. sandy soil 0 Lawns. clayey soil 0 *Refer to Figures RO-3 through RO-5 in Runoff Chapter of USDCM. Page 5 List of Variables A= C= C1, O2, and C3 C5 I= ID = L= S= P1 = Tc Td Tf Tr Qp V= watershed area in acres runoff coefficient coefficients in IDF formula 5-yr runoff coefficient rainfall intensity in inches/hour user defined identification number flow length in ft slope for flow length in ft/ft one hour precipitation value in inches time of concentration in minutes design rainfall duration in minutes flow time in minutes return period in years peak runoff rate in cfs flow velocity in ft/second Island Grove PR 100 Yrs.xls, Notation 1/31/2023, 5:03 PM Stormwater Drainage Study Appendix E: GRASS SWALE CALCULATIONS T-2 Grass Swale RESIDUAL CAPACITY FOR LARGER FLOODS 1;,, • 4" (MIN) SANDY LOAM 6" MI IN _L 2-YR WSE 6" MI TRAPEZOIDAL SWALE SECTION NTS I RESIDUAL CAPACITY FOR LARGER FLOODS 2-YR WS•E 4'° MIN. SANDY LOAM 12" MIN. MIN. D 1.0' 12" MIN. (2-YR) 1.0 FPS !Y TRIANGULAR SIAN GULAR SWALE SECTION NTS CONCRETE COI I AR ENERGY DISSIPATION b ir. l' rf I PROVIDE DOUBLE CLEANOUTS WITH WATER TIGHT CAPS @150' O.O. USE 90* SWEEP OR (2) 45' BENDS (OFFSET FROM SWALE CENTERLINE TO AVOID IMPEDING FLOW WHEN USING A TRIANGULAR SECTION Design Example 1 4 MIN. GRADE CONTROL STRUCTURE BEYOND GRADE CONTROL STRUCTURE BEYOND UNDERDRAIN AND SANDY LOAM RECOMMENDED FOR LONGITUDINAL SLOPES < 2.0%. 4" SLOTTED PIPE MEETING TABLE 05-3 WITH CDOT CLASS C FILTER MATERIAL ALL AROUND OR PERFORATED HOPE PIPE WITH AASHTO #67 ALL AROUND CONTAINED WITHIN CEOTEXTILE FABRIC. ASTM D4751-AOS US STD. SIEVE #50 TO 7a, ASTM D4533 MIN. TRAPEZOIDAL TEAR STRENGTH 100 X 60 LBS, MINIMUM COE SPECIFIED OPEN AREA OF 4%. GRADE CONTROL EXTEND GRADE CTROL STRUCTURE STRUCTURES INTO ONTHE BANK A MIN. OS ABOVE THE 2-YR WSE Ii UNDERDRAIN ENSURE ACCESS TO OUTLET BY CLEAN OUT OR OTHER ACCESSIBLE STRUCTURE SWALE PROFILE NITS Figure GS -1. Grass Swale Profile and Sections The UD-BMP workbook, designed as a tool for both designer and reviewing agency is available at www.udfcd.org. This section provides a completed design form from this workbook as an example. GS -6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Hydraulic Analysis Report Project Data Project Title: Designer: Project Date: Monday, January 30, 2023 Project Units: U.S. Customary Units Notes: Channel Analysis: Swale A Notes: input Parameters Channel Type: Trapezoidal Side Slope 1 (Z1): 3.0000 ft/ft Side Slope 2 (Z2): 3.0000 ft/ft Channel Width 1.00 ft Longitudinal Slope: 0.0070 ft/ft Manning's n: 0.0350 Depth 1.0000 ft Result Parameters Flow 9.4932 cfs Area of Flow 4.0000 ft^2 Wetted Perimeter 7.3246 ft Hydraulic Radius 0.5461 ft Average Velocity 2.3733 ft/s Top Width 7.0000 ft Froude Number: 0.5533 Critical Depth 0.7608 ft Critical Velocity 3.8014 ft/s Critical Slope: 0.0247 ft/ft Critical Top Width 5.56 ft Calculated Max Shear Stress 0.43681b/ft^2 Calculated Avg Shear Stress 0.2385 lb/ft^2 CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Dust Abatement Plan The purpose and intent of this Dust Abatement Plan is to ensure that the Project complies with applicable state and federal air quality standards. The Environmental Protection Agency (EPA) sets forth the National Ambient Air Quality Standards (NAAQs) pursuant to the Clean Air Act. Air quality impacts associated with construction projects generally arise from fugitive dust generation during the operation of heavy equipment. Colorado administers the NAAQS through issuance of the Air Pollutant Emission Notice (APEN). The Project will not exceed the NAAQS and will follow best management practices to ensure that the production of dust will be controlled by the regular application of water to the Project. The Project will obtain an APEN permit prior to construction. Minimal dust is expected to be generated during construction and operations due to the planned use of dust suppression best management practices and soil stabilization following construction and throughout operations. During construction, CBEP Solar 13, LLC and its contractors will control dust by applying water to disturbed soils and soil piles to control fugitive dust from blowing and impairing air quality. Once the construction phase is completed, the site will be visited 1-2 times per year for routine maintenance and as needed for emergency maintenance. Disturbed areas not covered with gravel as part of the Project design will be reseeded with native seed to revegetate disturbed areas and hold soil in place, minimizing fugitive dust impacts during operations. CBEP Solar 13, LLC would employ native revegetation methods or chemical control methods for infestations of weeds during regular maintenance if necessary. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Dust and Weed Mitigation Plan Dust Control: • Minimal dust is expected to be generated during construction and operations due to the planned use of dust suppression best management practices and soil stabilization following construction and throughout operations. During construction, CBEP Solar 13, LLC and its contractors will control dust by applying water to disturbed soils and soil piles to control fugitive dust from blowing and impairing air quality. • During the operations of the Project, the land under and around the Project will be seeded with a native grass seed mixture, which will mitigate dust. Weed Control: • The site will be inspected annually by CBEP Solar 13, LLC or its contractors for the presence of invasive species. Minor presences will be managed by cutting and pulling in a manner to not disburse or promote spreading of weed seeds. If a major presence occurs, mowing and the potential application of herbicides will be deployed. Herbicide selection may vary depending on the time of year, the life cycle of the noxious weed species. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO©CLOD DBREAKEN ERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Landscape and Screening Plan The Project will be surrounded by a 7 -foot tall game fence. Please refer to sheet C-402 of the USR Map for additional detail on the proposed security fence. (970) 425-3175 I INFO©CLOUDBREAKENERGY.COM I CLOUDBREAKENERGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Lighting Plan CBEP Solar 13, LLC is proposing to construct and operate the Island Grove Solar Project in unincorporated Weld County, Colorado. The Project includes construction of 3.7 MW of solar electric generation on a 74.17 acre parcel. This Lighting Plan describes lighting during the construction and operations phases of the Project. Temporary Construction Lighting: The need for lighting during construction is expected to be limited because the majority of construction activities will occur during daylight hours. If lighting is needed during construction, lights will be positioned and/or shielded from oncoming traffic and residences in the vicinity of the project site, as necessary. Cutoff -type luminaires would be used where practicable. Individual light sources would not exceed 150,000 lumens per light source (typical of a 1250W metal halide light) and would project 0.1 lumen or less at property lines. Unnecessary lighting will not be used. Lights would not exceed 24 feet in height. Any lighting needed for construction is not shown in the dimensioned elevation drawing of the USR Map due to its temporary nature. Project Operations Lighting: There will be no lighting on the Project after construction is completed. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 IN FO©CLOD DBREAKEN ERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Manure Management Plan CBEP Solar 13, LLC is proposing to construct and operate the Island Grove Solar Project in unincorporated Weld County, Colorado. The Project includes the construction of 3.7 Megawatts (MW) of solar electric generation on a portion of a 74.29 -acre parcel. In addition to the solar array, the Project site will continue to contribute to the agricultural economy of Weld County by using the pasture land underneath the solar array for sheep grazing. This Manure Management Plan describes CBEP Solar 13, LLC's plan to maintain and minimize the impacts of the manure on the Project parcel and neighboring community. Background: CBEP Solar 13, LLC intends to partner with a local shepherd that will be grazing no more than 500 sheep on the Island Grove Solar Project site for periods during the grazing season. The Island Grove Solar Project is one of many fields the flock of sheep will rotate between. These sheep will be processed in Weld County at Innovative Foods. Manure Load Management: Through rotational grazing and harrowing, the manure load will be evenly distributed across the parcel and have minimal impact on the neighboring community. Rotational Grazing: The shepherd will section off portions of the Project and graze the herd in the subsections, rotating the sheep to new subsections regularly. The shepherd will also rotate the herd between several Cloudbreak solar projects to manage the manure load and forage materials on the land. This will make the overall manure load very manageable and reduce the impact to surrounding properties. The herd will not stay permanently at the Island Grove Solar Project. The Project site will not serve as a feedlot for sheep. Harrowing: If necessary, a harrowing machine will be used on the Island Grove Solar Project site to spread out and break up the manure once the sheep move on to the next subsection or pasture. This machine will disturb the topsoil to help break down and bury the manure. Composting: If the manure load ever becomes problematic, CBEP Solar 13, LLC will physically remove the manure and compost it offsite. (970) 425-3175 I INFO©CLOUDBREAKENERGY.COM I CLOUDBREAKENERGY.COM <i TRC Noise Study Report January 2023 I Island Grove Solar Project Prepared For: Cloudbreak Energy Partners, LLC 4845 Pearl East Circle,Suite 118 Boulder, Colorado 80301 Prepared By: TRC Companies, Inc. 123 North College Avenue, Suite 370 Fort Collins, Colorado 80524 i TRC Noise Study Island Grove Solar Project Weld County, Colorado NOISE STUDY Cloudbreak Energy Partners, LLC (Cloudbreak) is proposing to construct and operate the Island Grove Solar Project (Project) in unincorporated Weld County, Colorado. The Project includes construction of up to 4 direct current (DC) Megawatts (MW) of solar electric generation on a 24.9 -acre tract. The purpose of this noise study was to determine the level of noise impact from the Project at nearby residences and to ensure that the Project complies with state and county regulations. The level of impact has been determined based on The State of Colorado Noise Law and WCC Chapter 14 Article 9 (Noise). Fundamentals of Noise Noise can be defined as unwanted sound. When a noise is distinctly louder than the ambient noise environment and reaches a certain level, it can disrupt normal activities. The magnitude of noise or the deviation from the ambient noise level is usually described by sound pressure. The magnitude of noise is usually described by a ratio of its sound pressure to a reference sound pressure, which is usually 20 micro - Pascals. A logarithmic scale is used to relate sound pressure to a common reference pressure, yielding the sound pressure level (SPL). SPL is measured in dimensionless units of decibels (dB) and are modified by frequency response of human hearing or weighting. The commonly accepted limits of human hearing to detect sound are between the threshold of hearing at 0 dB and the threshold of pain at 140 dB. Sound frequencies are represented in units of Hertz (Hz), which correspond to the number of vibrations per second of a given tone. Sound occurs over a wide range of frequencies. Three weightings have been established for measuring sound pressure: A, B, and C. The commonly accepted audible frequency is between 20 Hz and 20,000 Hz, and human hearing is most sensitive to the frequencies between 1,000 Hz and 6,000 Hz. The A -weighted scale is adjusted to frequencies most sensitive to human ears. Sound levels that are measured using the A -weighted scale are often expressed as dB(A). All noise levels in this noise impact analysis report will be expressed in dB(A). A key concept in evaluating potential noise impacts is the perceived effect of incremental increases in existing noise levels. Changes in dB(A) are exponential; therefore, an increase of 3 dB(A) is barely perceptible, an increase of 5 dB(A) is readily perceptible, and a 10 dB(A) increase would be perceived by someone to be a doubling of the noise level (loudness). Existing Noise Environment: The subject site is located northeast of the intersection of County Road 47 and County Road 54 in an unincorporated area of Weld County, Colorado. The Project Area sits adjacent to existing oil and gas industrial areas to the east and south, as well as agricultural fields to the north, east, and west. Residential properties are located to the southwest, west, and northwest of the Project. The applicable setbacks from adjacent property lines and roadways will be required, and much of the existing vegetation (if present) within the setbacks will be retained. Existing noise sources at the site occur mainly from infrequent 1 i TRC Noise Study Island Grove Solar Project Weld County, Colorado vehicular traffic traveling on nearby roadways. The oil and gas operations to the east and southeast of the Project Area are expected to generate some level of noise as well. State of Colorado Noise Law Colorado Revised Statutes 25-12-103: Maximum Permissible Noise Levels. 1. Every activity to which this article is applicable shall be conducted in a manner so that any noise produced is not objectionable due to intermittence, beat frequency, or shrillness. Sound levels of noise radiating from a property line at a distance of twenty-five feet or more there from in excess of the dB(A) established for the following time periods and zones shall constitute prima facie evidence that such noise is a public nuisance (Table 1). 2. In the hours between 7:00 a.m. and the next 7:00 p.m., the noise levels permitted in subsection (1) of this section may be increased by ten dB(A) for a period of not to exceed fifteen minutes in any one -hour period. 3. Periodic, impulsive, or shrill noises shall be considered a public nuisance when such noises are at a sound level of five dB(A) less than those listed in subsection (1) of this section. 4. Construction projects shall be subject to the maximum permissible noise levels specified for industrial zones for the period within which construction is to be completed pursuant to any applicable construction permit issued by proper authority or, if no time limitation is imposed, for a reasonable period of time for completion of project. Table 1. State of Colorado Maximum Allowable Noise Sound Pressure Levels for Specified Premises Zone 7am to next 7pm 7pm to next 7am Residential 55 dB(A) 50 dB(A) Commercial 60 dB(A) 55 dB(A) Light Industrial 70 dB(A) 65 dB(A) Industrial 80 dB(A) 75 dB(A) Weld County Code Noise Ordinance Weld County Code (WCC) 14-9-40: Maximum Permissible Noise Levels A. Sound levels shall be measured as provided for in Section 14-9-50. B. Sound levels are hereby established for each type of property during specific hours of the day. Any sound level which exceeds the level set for a type of property at any time of day is prohibited (Table 2). 2 i TRC Noise Study Island Grove Solar Project Weld County, Colorado C. Between the hours of 9:00 p.m. and 7:00 a.m., the noise levels set forth in Table 2 may be exceeded by up to ten (10) decibels for up to fifteen (15) minutes in a one -hour period. Table 2. Weld County Maximum Permissible Noise Levels Land Use 7am to 9pm 9pm to 7am Residential property or Commercial Area 55 dB(A) 50 dB(A) Industrial area or Construction activities 80 dB(A) 75 dB(A) Non -specified areas 55 dB(A) 50 dB(A) D. Vehicles operating in the public right-of-way are subject to the following maximum noise levels (Table 3) Table 3. Maximum Vehicular Sound Levels Vehicle Class (GVWR) Maximum 35 mph noise or less in Speed zone Limit Maximum noise over 35 mph in Speed zone Limit Over 10,000 lbs. 86 dB(A) 90 dB(A) Any other vehicle 80 dB(A) 84 dB(A) Weld County Code Exceptions Weld County Code (WCC) 14-9-60: Exceptions. The provisions of the Weld County Code do not apply to the following: N. Any noise produced at a construction site. Project Noise Construction Construction noise represents a shod -term (temporary) impact on ambient noise levels. Temporary noise impacts during construction would occur during daylight hours while construction equipment is being operated including, but not limited to, passenger vehicles, earthmoving equipment, concrete mixers, water trucks, and semi-tractor/trailer trucks. The spatial distribution of construction noise emissions would vary during the day and depend upon the type of activity. Construction traffic will generate noise along the haul route. This noise would be temporary during commuting hours and when supplies are delivered over the course of construction. Operations Sources of noise during operation would only include temporary vehicle noise from maintenance personnel access and typical noise emissions from the solar array, inverters (which convert electricity from AC -to -DC, and DC -to -AC), transformers (which "step up" and "step down" the system voltage), and overhead 3 i TRC Noise Study Island Grove Solar Project Weld County, Colorado transmission. Project facilities that emit sound during operation include inverters. Noise emission from inverters depends on the inverter model and number of inverters, which will be determined based on detailed engineering to be completed during final design and approval of the site, but typical emissions from industrial photovoltaic (PV) inverters and associated supporting equipment utilized in previous solar projects within the region range from 48 to 72 dB(A) at a distance of 10 feet (Tech Environmental 2012). Within the 48 to 72 dB(A) range, inverter sound levels are generally indistinguishable from background noise levels at a distance of 150 feet from the inverter (Tech Environmental 2012). Typical equipment that is expected to be utilized for this Project includes Module Model HELIENE 144M M8 530W Bifacial or similar and Inverter Model CPS SCH125KTL-DO/US-600 or similar. For comparison, a gas lawnmower can produce around 90 dB(A), a vacuum cleaner around 70 dB(A), and a dishwasher in the next room around 50 dB(A) (FAA 2022). Based on the typical sound levels from Project operation and the distance to the boundary, the Project will adhere to Weld County and State of Colorado permissible noise levels. Conclusion The purpose of this noise study was to determine the level of noise impact the Project will produce and ensure that the Project will comply with state and county regulations. The level of noise impact from the Project has been determined based on the Weld County noise regulations as well as the state of Colorado Noise Law. Based on typical solar energy facility equipment, it is expected that the noise levels from Project facilities will comply with the Weld County Noise Ordinance and state statute requirements. References Federal Aviation Administration (FAA). 2022. Fundamentals of Noise and Sound. Available https://www.faa.gov/regulations_policies/policy_ guidance/noise/basics/. Accessed March 23, 2022. Tech Environmental, Inc. 2012. Study of Acoustic and EMF Levels from Solar Photovoltaic Projects. Prepared by Tech Environmental, Inc., Waltham, MA. Prepared for Massachusetts Clean Energy Center, Boston, MA. December 2012. 4 CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Sewage Disposal Documentation No sewage disposal will be required for the operation of the Project. CBEP Solar 13, LLC or its contractor will provide portable toilets during construction. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM 'TRC Stormwater Drainage Study CLOUDBREAK ENERGY PARTNERS Date: To: From: Project: Subject: 03/10/2023 Cloudbreak Energy Allyson Williamson, TRC Companies 700 Highlander Blvd., Suite 210 Arlington, TX 76015 Island Grove Solar Project On -Site Drainage Study PRELIMINARY FOR INTERIM REVIEW ONLY. NOT FOR PERMITTING, BIDDING, NOR CONSTRUCTION. Prepared by or under the Direct Supervision of: Allyson Williamson, P.E. 60360 "03/10/2023" Cloudbreak Energy is pursuing the development of the Island Grove project, a photovoltaic energy generation facility at a 23.8 -acre site in Weld County, Colorado, alongside Co Rd 54 (See Appendix A — Site Plans C-301 & C-302). The existing site currently is used for agricultural purposes with approximately 1% slopes. This drainage study was prepared to summarize findings from performing a hydrologic analysis of the project site to identify the potential stormwater impact from the proposed solar project and develop appropriate drainage best management practices (BMPs) to address the impact. This drainage study was prepared to comply with the requirements from the Weld County Engineering and Construction Criteria (WCECC) Manual, updated January 2021. Proposed Project The proposed solar project will consist of pole mounted photovoltaic (PV) arrays. Ground disturbance under the panels will be minimal; thus, the existing perviousness of the soil will be maintained under the solar cells allowing infiltration. Rainfall runoff from the panels will not be concentrated and flow under the pole mounted PV panels matching the pre -development flow patterns. Additional improvements associated with this project are limited to gravel drives for vehicle access and concrete pads for distribution transformers (see Appendix A - Site plans C-301 & C-302). No public access or utility infrastructure improvements are anticipated at this time. FEMA Floodplains According to FEMA Flood Insurance Rate Map (FIRM) Panel Number 08123C1563E (Jan 20th, 2016), the project is located outside the mapped 100 -year floodplain. The risk of flooding within the project site is not anticipated. A copy of the FIRM is included in Appendix B. Onsite Drainage Currently, the existing site includes a ditch north of the project area responsible for irrigation. The soils in the area consist of hydrologic soil group (HSG) C and D soils given by the Natural Resources Conservation Service (NRCS — Appendix C). The proposed development footprint will be in areas with soil types C&D. Based upon the drainage patterns, the site is analyzed as one drainage area labeled A, with an estimated area of 23.8 ac. External offsite flows follow the existing ditches and are not expected to affect the project site. See Appendix A for the drainage area maps and details. Stormwater Drainage Study A hydrologic analysis was prepared using the Rational Method based upon requirements in the WCECC Manual. The analysis provided estimates of the peak flow rates for the 100 -year storm under both pre- and post -development conditions. The design rainfall depth for a 1 -hour, 100 - year storm is 2.71 inches based upon NOAA Atlas 14: Precipitation -Frequency Atlas. The Rational Method shown below was used to determine the peak flow rates from each drainage area. Existing conditions are undeveloped and determined to be "Greenbelt, Agriculture" which correlates to a 2% impervious value according to Table 5-2, Weld County Engineering and Construction Criteria. In Table 5-5, based off the soil type and impervious percentage, the runoff calculation was 0.51, respectively. Proposed conditions were determined to be the weighted average of "Greenbelt, Agriculture" (2% impervious), "Solar Facilities C&D Soils" (25% impervious), "Packed Gravel" (40% impervious), and "Conc. Pads" (100% impervious). Using the same process as before, the runoff coefficient was weighted to be 0.5702, respectively. The drainage area imperviousness and resulting flow rates from pre -and post -development conditions are summarized below. See Appendix D for the runoff coefficient calculations. Q=C*I*A Where: Q- Runoff rate in cubic feet per second (cfs) / Rainfall Intensity in inches per hour (in/hr) A - Area of the basin in acres (ac) Pre -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 23.8 0.51 5.65 Post -development Runoff Calculation Parameters Drainage Area Area, A (ac) Weighted Coefficient, Runoff C Rainfall I (in/hr) Intensity, A 23.8 0.5702 5.65 Stormwater Drainage Study 100 -year Runoff Calculation Results Drainage Area Pre -development Peak Flow (cfs) Rate Post Peak -development Flow (cfs) Rate DIFFERENCE (cfs) A 68.6 76.7 8.10 Based upon the above results, the increase of impervious area has shown to result in some change (less than 12%) between the pre -development and post -development runoff peak flows. Because of this, a detention basin facility will not be proposed. Instead, grass swales will be introduced within the project site boundary to mitigate energy and attenuate the minimal flow increase from gravel roads and concrete pads. Erosion Control/Stormwater Management Plan Erosion control features such as silt fences and a grass swale (also mentioned above) will be installed on the site prior to construction activities. Such measures will be included in the e rosion control plan and detail sheets within the final construction documents. Grass swale sizing calculations are summarized in Appendix E. Conclusion The drainage study and attached drainage maps were produced in accordance with requirements from Weld County Engineering and Construction Criteria (WCECC) Manual, u pdated January 2021. The existing stormwater flow characteristics are expected to remain u nchanged and increases in peak flow rates have been proven to be negligible. A basin type of stormwater detention is not be necessary. Improvements proposed with the project site are limited to a gravel paved drive and one small concrete distribution transformer pads. No public access or utility infrastructure improvements are anticipated at this time. The proposed development will not alter historic drainage patterns and adjacent and downstream property owners. Stormwater Drainage Study References 1. Weld County, Weld County Engineering and Construction Criteria Manual, January 2021. 2. Web Soil Survey, Natural Resources Conservation Service, United States Department of Agriculture. Online at: http://websoilsurvey.nrcs.usda.gov, accessed Januar 2023. 3. Flood Insurance Rate Map, Weld County, Texas and Incorporated Areas, Jan 20, 2016, Map Number 08123C1563E, Federal Emergency Management Agency. 4. NOAA Atlas 14, Volume 11, Version 2. ESRI Maps. USGS. Sanja Perica, Sandra Pavlovic, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Orlan Wilhite. Appendices A. Site Plans C-301 & C-302 5-7 B. FEMA Firmette Map 8-9 C. NRCS Soil Layer Map 10-14 D. Rational Method Calculations 15-29 Existing Calculations 16 Proposed Calculations 23 E. Grass Swale Calculations 30-33 Stormwater Drainage Study Appendix A: SITE PLANS C301 & C302 Stormwater Drainage Study Appendix B: FEMA FIRMETTE MAP Stormwater Drainage Study Appendix C: NRCS SOIL LAYER MAP 40° 22' 49" N 1 9 0 ti 4 40° 22' 37' N 4 104° 37'3"W N Hydrologic Soil Group —Weld County, Colorado, Southern Part (IslandGrove_DABoundary) 532640 Map Scale: 1:2,600 if printed on A landscape (11" x 8.5") sheet Meters 0 35 70 140 210 Met 0 100 200 400 600 Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 104° 36' 39" W 40° 22' 49" N 0 N- co 4 0 4 co 40° 22'37'N 1040 36' 39" W ,b Natural Resources as Conservation Service Web Soil Survey National Cooperative Soil Survey 1/27/2023 Page 1 of 5 Hydrologic Soil Group —Weld County, Colorado, Southern Part (IslandGrove_DABoundary) MAP LEGEND Area of Interest (AO!) Area of Interest (A01) ) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines 0 0 A A/D B B/D C C/D D Not rated or not available Soil Rating Points II O O O A A/D B B/D MAP INFORMATION C The soil surveys that comprise your AOI were mapped at 1:24,000. C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background ,; Aerial Photography Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Weld County, Colorado, Southern Part Survey Area Data: Version 21, Sep 1, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 8, 2021 Jun 12, 2021 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. ,b Natural Resources lain Conservation Service Web Soil Survey National Cooperative Soil Survey 1/27/2023 Page 2of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Altvan loam, percent slopes 0 to 1 B 0.0 0.0% 3 Aquolls and Aquents, gravelly substratum D 3.8 16.1% 22 Dacono 3 clay loam, percent slopes 1 to C 15.6 65.5% 41 Nunn clay percent loam, slopes 0 to 1 C 1.0 4.2% 42 Nunn clay loam, percent slopes 1 to 3 C 3.4 14.2% Totals for Area of Interest 23.8 100.0% e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 3of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary 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 (A/D, B/D, and CID). 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 (A/D, 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. Rating Options Aggregation Method: Dominant Condition e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 4of5 Hydrologic Soil Group —Weld County, Colorado, Southern Part IslandGrove_DABoundary Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole. A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not. For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods. The aggregation method "Dominant Condition" first groups like attribute values for the components in a map unit. For each group, percent composition is set to the sum of the percent composition of all components participating in that group. These groups now represent "conditions" rather than components. The attribute value associated with the group with the highest cumulative percent composition is returned. If more than one group shares the highest cumulative percent composition, the corresponding "tie -break" rule determines which value should be returned. The "tie -break" rule indicates whether the lower or higher group value should be returned in the case of a percent composition tie. The result returned by this aggregation method represents the dominant condition throughout the map unit only when no tie has occurred. Component Percent Cutoff. None Specified Components whose percent composition is below the cutoff value will not be considered. If no cutoff value is specified, all components in the database will be considered. The data for some contrasting soils of minor extent may not be in the database, and therefore are not considered. Tie -break Rule: Higher The tie -break rule indicates which value should be selected from a set of multiple candidate values, or which value should be selected in the event of a percent composition tie. e Natural Resources Web Soil Survey Conservation Service National Cooperative Soil Survey 1/27/2023 Page 5of5 Stormwater Drainage Study Appendix D: RATIONAL METHOD CALCULATIONS 1/27/23, 3:07 PM Precipitation Frequency Data Server NOAA Atlas 14, Volume 8, Version 2 Location name: Greeley, Colorado, USA* Latitude: 40.3796°, Longitude: -104.6161° Elevation: 4640.41 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES 1"."ti1F ti Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Average recurrence interval (years) J Duration 1 2 5 10 25 50 100 200 I 500 1000 5 -min ! 0.243 (0.201-0.298) 0.294 (0.242-0.361) 0.391 (0.320-0.481) 0.484 (0.394-0.599) 0.631 (0.500-0.838) 0.760 (0.580-1.02) 0.901 (0.658-1.24) 1.06 (0.733-1.51) 1.29 (0.848-1.89) 1.47 (0.935-2.17) 10 -min 0.357 (0.294-0.437), 0.431 (0.355-0.529) 0.573 (0.469-0.705)I(0.577-0.878) 0.709 0.924 (0.732-1.23) 1.11 (0.850-1.49) 1.32 (0.964-1.82) 1.55 (1.07-2.20) 1.88 (1.24-2.76) 2.16 (1.37-3.18) 0.435 (0.358-0.533)1 0.526 (0.433-0.645) 0.698 (0.572-0.860) I + 1.36 (1.04-1.82) 1.61 (1.18-2.22) 1.89 (1.31-2.69) 2.30 (1.51-3.37) 2.6388) 30 -min 0.584 (0.481-0.716) 0.705 (0.580-0.865) 0.936 (0.767-1.15) 1.16 ' (0.944-1.44) ` 1.52 (1.20-2.01) I 1.83 (1.40-2.45) 2.17 (1.59-2.99) 2.55 (1.77-3.63) 3.11 (2.05-4.56) 3.57 (2.26-5.26) j 60 -min 0.726 (0.598-0.890) 0.864 (0.711-1.06) 1.14 (0.933-1.40) 1.41 (1.15-1.75) 1.86 (1.48-2.49) 2.26 (1.73-3.05) 2.71 (1.98-3.75) 3.21 (2.23-4.59) 3.95 (2.61-5.81) 4.57 (2.90-6.74) 2-h r 0.868 (0.721-1.06) I 1.02 (0.848-1.25) 1.34 (1.11-1.64) 1.67 (1.37-2.05) 2.21 (1.78-2.94) 3.87 4.80 5.58 (3.57-8.14) 3 -hr 0.951 (0.793-1.15) 1.11 (0.923-1.34) 1.44 (1.20-1.75) 1.79 (1.48-2.19) 2.38 (1.93-3.16) 2.92 (2.27-3.90) 3.53 (2.63-4.84) 4.22 (2.98-5.96) 5.26 (3.54-7.64) 6.13 (3.95-8.90) 6 -hr 1.09 (0.914-1.31) a 1.29 (1.08-1.54) 1.68 (1.40-2.02) 2.07 (1.72-2.51) 4 2.72 (2.21-3.56) 3.30 (2.58-4.35) 3.95 (2.96-5.34) 4.68 (3.33-6.52) 5.76 (3.91-8.26) 6.66 (4.34-9.58) 12 -hr 1.27 (1.07-1.51) 1.97 (1.66-2.35) 2.40 (2.01-2.89) 3.08 (2.50-3.94) 4.30 (3.24-5.73) 5.01 6.03 (4.12-8.53) 6.87 (4.52-9.78) 24 -hr 1.51 (1.29-1.78) Y 1.78 (1.51-2.10) 2.27 (1.92-2.69) 2.72 I (2.29-3.24) I 3.42 (2.80-4.32) i 4.02 (3.18-5.14) 4.67 (3.54-6.14) 5.38 (3.89-7.29) 6.40 (4.41-8.94) 7.23 (4.81-10.2) 2 -day 1.74 (1.49-2.04) i 2.05 (1.76-2.40) 2.60 (2.22-3.06) 3.09 I (2.62-3.65) i 3.83 (3.14-4.75) i 4.43 (3.53-5.58) 5.08 (3.88-6.57) 5.77 (4.20-7.71) 6.74 (4.68-9.29) 7.52 (5.06-10.5) i 3 -day 1.91 (1.64-2.22) 2.22 (1.91-2.59) M2.77 (2.38-3.24) 3.27 (2.78-3.84) 4.01 (3.30-4.95) 4.62L__ (3.70-5.78) 5.27 (4.05-6.78) 5.97 (4.37-7.92) 6.95 (4.86-9.52) 7.74 ll (5.24-10.7) 4 -day 2.03 (1.76-2.36)J 2.35 (2.03-2.73) 2.92 III4.16 (2.51-3.40) 3.42 1 (2.92-4.00) I (3.44-5.12) 4.78 (3.84-5.96) 5.43 (4.19-6.96) 6.13 (4.50-8.10) 7.12 (5.00-9.69) 7.90 (5.37-10.9) 7 -day a 2.31 (2.01-2.66) I 2.69 (2.34-3.10) 3.33 (2.88-3.86) 3.88 (3.34-4.52) I 4.67 (3.87-5.65) j 5.30 (4.27-6.51) 5.94 (4.60-7.51) 6.61 (4.88-8.62) 7.53 (5.32-10.1) 8.24 (5.65-11.3) i 10 -day 2.55 (2.22-2.92) 2.98 (2.60-3.42) 3.69 (3.20-4.25) 4.28 (3.69-4.95) 5.10 (4.23-6.11) 5.74 (4.63-6.99) 6.38 (4.95-7.99) 7.03 (5.21-9.09) 7.90 (5.60-10.5) 8.56 (5.90-11.6) 20 -day 3.26 (2.87-3.71) 3.77 (3.31-4.29) 4.59 (4.02-5.24) 5.26 (4.57-6.04) 6.16 (5.14-7.29) 6.84 (5.57-8.23) 7.51 (5.88-9.29) 8.17 (6.10-10.4) 9.02 (6.46-11.9) 9.65 (6.73-13.0) 30 -day a 3.83 (3.39-4.34) i 5.32 i (4.68-6.05) 6.06 I (5.29-6.92) I 7.04 (5.90-8.27) i 7.78 (6.36-9.29) 8.49 (6.68-10.4) 9.18 (6.90-11.6)1 10.1 (7.25-13.2) 10.7 (7.51-14.3) V 45 -day 4.53 (4.02-5.10) 5.20 (4.61-5.86) 6.27 (5.53-7.08) 7.11 (6.24-8.08) 8.22 (6.91-9.58) 9.04 (7.42-10.7) 9.82 (7.76-12.0) 10.6 (7.98-13.3) 11.5 (8.33-14.9) 12.2 (8.59-16.2) 60 -day 5.09 (4.53-5.71) 5.87 (5.22-6.59) 7.09 (6.28-7.98) 8.05 (7.08-9.10) 9.29 (7.83-10.8) 10.2 (8.39-12.0) 11.0 (8.75-13.4) 11.8 (8.97-14.8) 12.8 (9.31-16.5) 13.5 (9.57-17.9) 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/hdsc/pfds/pfds_printpage.html?lat=40.3796&Ion=-104.6161 &data=depth&units=english&series=pds 1/4 EXISTING CALCULATIONS PEAK RUNOFF PREDICTION BY THE RATIONAL METHOD Version 1.02a, Released August 2005 Urban Drainage and Flood Control District Denver, Colorado Purpose: Function: Content: Intro Weighted C Tc and PeakQ Design Info Notation Acknowledgements: Comments? Revisions? This workbook applies the Rational Method to estimate stormwater runoff and peak flows from small urban catchments, i.e., typically less than 90 acres. 1. To apply the area -weighting method to calculate the representative runoff coefficient C for a catchment. 2. To calculate the time of concentration, and then compare with the empirical time of concentration limit used for the Denver region. The smaller one is recommended as the rainfall duration for use with the Rational Method. 3. To calculate the design rainfall intensity and peak flow rate. The workbook consists of the following five sheets: Describes the purpose of each sheet in the workbook. Applies the area -weighting method to determine the runoff C. Calculates Tc and Q -peak. Provides the recommended runoff C's for various land uses. Defines the variables used. Spreadsheet Development Team: Dr. James C.Y. Guo, P.E. Professor, Department of Civil Engineering University of Colorado at Denver Ken A. MacKenzie, P.E. Urban Drainage and Flood Control District Wright Water Engineers, Inc. Denver, Colorado Direct all comments regarding this spreadsheet workbook to: UDFCD E -Mail Check for revised versions of this or any other workbook at: Downloads Island Grove EX 100 Yrs.xls, Intro 1/31/2023, 5:00 PM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR Illustration rEr : Flow Direction Catch ent B arundary Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. A C* CA input input input output C Soil 20.00 I 0.51 10.20 D Soil 3.80 0.51 1.94 I I sum: 2 23.80 sum: 1 12.14 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5100 *See sheet "Design Info" for inperviousness-based runoff coefficient values. Island Grove EX 100 Yrs.xls, Weighted C 1/31/2023, 5:00 PM CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Existing 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 23.80 2.00 C II. Rainfall Information Design Storm Return Period, Tr = 01 = C2= C3= P1= Acres ok A, B, C, or D I (inch/hr) = C1 * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.51 0.51 0.16 0.16 Reach 3 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration Reach 21. - Reach 1 o tre rland flow LEGEND 0 B,eginnhkg Flow Dirertion C at: nt B o undary NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage/ Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales/ Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output Flow Time Tf minutes output 0.0030 300 0.16 N/A 0.11 43.74 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = Rainfall Intensity at User -Defined Tc, I = 1.89 5.65 5.65 5.00 0.32 58.66 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 102.40 17.85 17.85 22.91 68.60 68.60 cfs cfs cfs Island Grove EX 100 Yrs.xls, Tc and PeakQ 1/31/2023, 5:00 PM Runoff Coefficient vs. Watershed Imperviousness Based on Runoff Coefficient estimating equation published by Urbonas, et.al. (1990) & WEF (1998) Basic equation for NRCS Soil Types C & D: Cep = K CD + (0.858 */ i - 0.786 *12 + (1.774 *i + 0.04) Basic equation for NRCS Soil Type A: C_4 = K 4 + (1.31 *i3 - 1.44 *i 2 + 1.135 *i - 0.12) in which use values for C-4 > 0 in which: i = Ic,/100, imperviousness ratio I, = watershed imperviousness in percent CA = Runoff Coefficient for NRCS Soil Type A KA = Correction factor for CA when the storm return period is greater than 2 -years CCn A -CD = Runoff Coefficient for NRCS Soil Types C and D = Correction factor for CCD when the storm return period is greater than 2 -years Values of Correction Factors Kc•D & KA NRCS Stone Return Period Soil Types, • 2-}n 5-yr 10-yr 25-yr 50-yr 100-yr C & D 0.00 [-0.10*i+0.11] [-0.18*i-0.21] [-0.28*i+0.33] [-0.33*i-0.40] [-0.39*i+0.46] A 0.00 [-0.08*i+0.09] [-0.1 t*/ -0.17] [-0.19*i+0.24] [-0.22*/ 0.28] [-0.25*i+0.32] Values of Runoff Coefficient C CD Values of Runoff Coefficient C,4 Imp en: . 1 Te C mid D NRCS Hydrologic Soil Groups Type A NRCS Hydrologic Soils Group tRau° 11! 2-yr >-yT 1 U -n 2l-yl. >U-yT 1 UU-yT 2-yr l-yi- 1O -n 2.5-yT :)U -,,I 1 Ull-,1* 0.00 0.04 0.15 0.25 0.37 0.44 0.50 -0.12 -0.03 0.05 0.12 0.16 0.20 0.05 0.08 0.18 0.28 0.39 0.46 0.52 -0.07 0.02 0.10 0.16 0.20 0.24 0.10 0.11 0.21 0.30 0.41 0.48 0.53 -0.02 0.06 0.14 0.20 0.24 0.28 0.15 0.14 0.24 0.32 0.43 0.49 0.54 0.02 0.10 0.17 0.23 0.27 0.30 0.20 0.17 0.26 0.34 0.44 0.50 0.55 0.06 0.13 0.20 0.26 0.30 0.33 0.25 0.20 0.28 0.36 0.46 0.52 0.56 0.09 0.16 0.23 0.29 0.32 0.35 0.30 0.22 0.30 0.38 0.47 0.53 0.57 0.13 0.19 0.25 0.31 0.34 0.37 0.35 0.25 0.33 0.40 0.48 0.54 0.57 0.16 0.22 0.28 0.33 0.36 0.39 0.40 0.28 0.35 0.42 0.50 0.55 0.58 0.19 0.25 0.30 0.35 0.38 0.41 0.45 0.31 0.37 0.44 0.51 0.56 0.59 0.22 0.27 0.33 0.37 0.40 0.43 0.50 0.34 0.40 0.46 0.53 0.57 0.60 0.25 0.30 0.35 0.40 0.42 0.45 0.55 0.37 0.43 0.48 0.55 0.59 0.62 0.29 0.33 0.38 0.42 0.45 0.47 0.60 0.41 0.46 0.51 0.57 0.61 0.63 0.33 0.37 0.41 0.45 0.47 0.50 0.65 _ 0.45 0.49 0.54 0.59 0.63 0.65 0.37 0.41 0.45 0.49 0.51 0.53 0.70 0.49 0.53 0.57 0.62 0.66 0.68 0.42 0.45 0.49 0.53 0.54 0.56 0.75 0.54 0.58 0.62 0.66 0.69 0.71 0.47 0.50 0.54 0.57 0.59 0.61 0.80 0.60 0.63 0.66 0.70 0.73 0.74 0.54 0.56 0.60 0.63 0.64 0.66 0.85 0.66 0.68 0.71 0.75 0.78 0.79 0.61 0.63 0.66 0.69 0.70 0.72 0.90 0.73 0.75 0.77 0.80 0.83 0.83 0.69 0.71 0.73 0.76 0.77 0.79 0.95 0.80 0.82 0.84 0.87 0.89 0.89 0.78 0.80 0.82 0.84 0.85 0.86 1.00 0.89 0.90 0.92 0.94 0.96 0.96 0.89 0.90 0.92 0.94 0.95 0.96 Runoff Coefficient Notes: 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0 For Type B Soils. use the average of coefficients Cu) and CA . When the Runoff Coefficient in above table is < 0, use 0. When compositing the Runoff Coefficient for different soil typ Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soils C & D 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Watershed Impervious Ratio 1.0 es, use the table values above regardless if they are < 0 100-yr 4 25-yr 10—yr ;sr 5—yr 2—yr Runoff Coefficient Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soil A 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 =%.J 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Watershed Impervious Ratio 100-yr t 25-yr • 10-yr 5-yr 2-yr Page 4 I. One -hr Precipitation Values for Metro Denver Area Return period in years 2 5 10 50 100 Depth in inches 0.93 1.35 1.61 2.20 2.60 II. Recommended Runoff Coefficients for Metro Denver Land Use or Surface Characteristics Percent Imper- viousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family " Multiunit (detached) 60 Multiunit (attached) 75 Half -acre lot or larger Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks. cemeteries: 5 Playgrounds: 10 Schools: 50 Railroad yard areas: 15 Undeveloped areas: Historical Flow Analysis 2 Greenbelts. agricultural Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Driveways and sidewalks: 90 Roofs: 90 Lawns. sandy soil 0 Lawns. clayey soil 0 *Refer to Figures RO-3 through RO-5 in Runoff Chapter of USDCM. Page 5 List of Variables A= C= C1, O2, and C3 C5 I= ID = L= S= P1 = Tc Td Tf Tr Qp V= watershed area in acres runoff coefficient coefficients in IDF formula 5-yr runoff coefficient rainfall intensity in inches/hour user defined identification number flow length in ft slope for flow length in ft/ft one hour precipitation value in inches time of concentration in minutes design rainfall duration in minutes flow time in minutes return period in years peak runoff rate in cfs flow velocity in ft/second Island Grove EX 100 Yrs.xls, Notation 1/31/2023, 5:00 PM PROPOSED CALCUATIONS PEAK RUNOFF PREDICTION BY THE RATIONAL METHOD Version 1.02a, Released August 2005 Urban Drainage and Flood Control District Denver, Colorado Purpose: Function: Content: Intro Weighted C Tc and PeakQ Design Info Notation Acknowledgements: Comments? Revisions? This workbook applies the Rational Method to estimate stormwater runoff and peak flows from small urban catchments, i.e., typically less than 90 acres. 1. To apply the area -weighting method to calculate the representative runoff coefficient C for a catchment. 2. To calculate the time of concentration, and then compare with the empirical time of concentration limit used for the Denver region. The smaller one is recommended as the rainfall duration for use with the Rational Method. 3. To calculate the design rainfall intensity and peak flow rate. The workbook consists of the following five sheets: Describes the purpose of each sheet in the workbook. Applies the area -weighting method to determine the runoff C. Calculates Tc and Q -peak. Provides the recommended runoff C's for various land uses. Defines the variables used. Spreadsheet Development Team: Dr. James C.Y. Guo, P.E. Professor, Department of Civil Engineering University of Colorado at Denver Ken A. MacKenzie, P.E. Urban Drainage and Flood Control District Wright Water Engineers, Inc. Denver, Colorado Direct all comments regarding this spreadsheet workbook to: UDFCD E -Mail Check for revised versions of this or any other workbook at: Downloads Island Grove PR 100 Yrs.xls, Intro 1/31/2023, 5:03 PM Area -Weighting for Runoff Coefficient Calculation Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR Illustration 1..E GIIND : Flow Direction Catchm eat Boundary Instructions: For each catchment subarea, enter values for A and C. Subarea Area Runoff Product ID acres Coeff. _ A C* CA input input input output C Soil 19.27 0.56 10.79 D Soil 3.80 0.56 2.13 Packed Gravel _ 0.72 0.89 _ 0.64 Conc. Pads 0.01 0.96 0.01 Sum: 23.80 sum: 13.57 Area -Weighted Runoff Coefficient (sum CA/sum A) = 0.5702 *See sheet "Design Info" for inperviousness-based runoff coefficient values. Island Grove PR 100 Yrs.xls, Weighted C 1/31/2023, 5:03 PM CALCULATION OF A PEAK RUNOFF USING RATIONAL METHOD Project Title: Catchment ID: Cloudbreak Island Grove - Proposed 100 YR I. Catchment Hydrologic Data Catchment ID = Area = Percent Imperviousness = NRCS Soil Type = A 23.80 25.00 C II. Rainfall Information Design Storm Return Period, Tr = 01 = C2= C3= P1= Acres ok A, B, C, or D I (inch/hr) = C1 * P1 /(C2 + Td)AC3 100 28.50 10.00 0.786 2.71 years (input return period for design storm) (input the value of C1) (input the value of C2) (input the value of C3) inches (input one -hr precipitation --see Sheet "Design Info") III. Analysis of Flow Time (Time of Concentration) for a Catchment Runoff Coefficient, C = Overide Runoff Coefficient, C = 5-yr. Runoff Coefficient, C-5 = Overide 5-yr. Runoff Coefficient, C = 0.56 0.57 0.28 - is Reach :3 (enter an overide C value if desired, or leave blank to accept calculated C.) (enter an overide C-5 value if desired, or leave blank to accept calculated C-5.) Illustration Reach 2 Reach 1 overland flow LEGEND Beginning Flow Direc do n C aic lune of B o undary NRCS Land Type Conveyance Heavy Meadow 2.5 Tillage/ Field 5 Short Pasture/ Lawns 7 Nearly Bare Ground 10 Grassed Swales/ Waterways 15 Paved Areas & Shallow Paved Swales (Sheet Flow) 20 Calculations: Reach ID Overland Slope S ft/ft input Length L ft input 5-yr Runoff Coeff C-5 output NRCS Convey- ance input Flow Velocity V fps output Flow Time Tf minutes output 0.0030 300 0.28 N/A 0.13 38.02 1 0.0040 1,113 2 3 4 5 Sum 1,413 IV. Peak Runoff Prediction Rainfall Intensity at Computed Tc, I = Rainfall Intensity at Regional Tc, I = Rainfall Intensity at User -Defined Tc, I = 1.39 5.65 5.65 2.50 0.16 117.32 Computed Tc = Regional Tc = User -Entered Tc = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = inch/hr Peak Flowrate, Qp = Calculated values for Tc & Qp are based on overide values entered for C & C-5. 155.34 17.85 17.85 18.91 76.70 76.70 cfs cfs cfs Island Grove PR 100 Yrs.xls, Tc and PeakQ 1/31/2023, 5:03 PM Runoff Coefficient vs. Watershed Imperviousness Based on Runoff Coefficient estimating equation published by Urbonas, et.al. (1990) & WEF (1998) Basic equation for NRCS Soil Types C & D: Cep = Ka) + (0.858 *i3 - 0.786 *(+ 0.774 *i + 0.04) Basic equation for NRCS Soil Type A: C_4 = K .r + (1.31 *i3 - 1.44 *i 2 + 1.135 *i - 0.12) in which use values for C-4> 0 in which: i = Ic,/100, imperviousness ratio I, = watershed imperviousness in percent CA = Runoff Coefficient for NRCS Soil Type A KA = Correction factor for CA when the storm return period is greater than 2 -years CCn A -CD = Runoff Coefficient for NRCS Soil Types C and D = Correction factor for CCD when the storm return period is greater than 2 -years Values of Correction Factors KGD & KA NRCS Stone Return Period Soil Types, • 2-}n 5-yr 10-yr 25-yr 50-yr 100-yr C & D 0.00 [-0.10*i+0.11] [-0.18*i-0.21] [-0.28*i+0.33] [-0.33*i-0.40] [-0.39*i+0.46] A 0.00 [-0.08*i+0.09] [-0.1 t*/ -0.17] [-0.19*i+0.24] [-0.22*/ 0.28] [-0.25*i+0.32] Values of Runoff Coefficient C CD Values of Runoff Coefficient C,4 Imp en: . 1 Te C mid D NRCS Hydrologic Soil Groups Type A NRCS Hydrologic Soils Group tRau° 11! 2-yr :)-yr 1 U-yr 2l-yl. >U-yr 100-yr 2-yr l-yi- 10 -NT 2.5-yr :)U-yT 1 Ull-n 0.00 0.04 0.15 0.25 0.37 0.44 0.50 -0.12 -0.03 0.05 0.12 0.16 0.20 0.05 0.08 0.18 0.28 0.39 0.46 0.52 -0.07 0.02 0.10 0.16 0.20 0.24 0.10 0.11 0.21 0.30 0.41 0.48 0.53 -0.02 0.06 0.14 0.20 0.24 0.28 0.15 0.14 0.24 0.32 0.43 0.49 0.54 0.02 0.10 0.17 0.23 0.27 0.30 0.20 0.17 0.26 0.34 0.44 0.50 0.55 0.06 0.13 0.20 0.26 0.30 0.33 0.25 0.20 0.28 0.36 0.46 0.52 0.56 0.09 0.16 0.23 0.29 0.32 0.35 0.30 0.22 0.30 0.38 0.47 0.53 0.57 0.13 0.19 0.25 0.31 0.34 0.37 0.35 0.25 0.33 0.40 0.48 0.54 0.57 0.16 0.22 0.28 0.33 0.36 0.39 0.40 0.28 0.35 0.42 0.50 0.55 0.58 0.19 0.25 0.30 0.35 0.38 0.41 0.45 0.31 0.37 0.44 0.51 0.56 0.59 0.22 0.27 0.33 0.37 0.40 0.43 0.50 0.34 0.40 0.46 0.53 0.57 0.60 0.25 0.30 0.35 0.40 0.42 0.45 0.55 0.37 0.43 0.48 0.55 0.59 0.62 0.29 0.33 0.38 0.42 0.45 0.47 0.60 0.41 0.46 0.51 0.57 0.61 0.63 0.33 0.37 0.41 0.45 0.47 0.50 0.65 _ 0.45 0.49 0.54 0.59 0.63 0.65 0.37 0.41 0.45 0.49 0.51 0.53 0.70 0.49 0.53 0.57 0.62 0.66 0.68 0.42 0.45 0.49 0.53 0.54 0.56 0.75 0.54 0.58 0.62 0.66 0.69 0.71 0.47 0.50 0.54 0.57 0.59 0.61 0.80 0.60 0.63 0.66 0.70 0.73 0.74 0.54 0.56 0.60 0.63 0.64 0.66 0.85 0.66 0.68 0.71 0.75 0.78 0.79 0.61 0.63 0.66 0.69 0.70 0.72 0.90 0.73 0.75 0.77 0.80 0.83 0.83 0.69 0.71 0.73 0.76 0.77 0.79 0.95 0.80 0.82 0.84 0.87 0.89 0.89 0.78 0.80 0.82 0.84 0.85 0.86 1.00 0.89 0.90 0.92 0.94 0.96 0.96 0.89 0.90 0.92 0.94 0.95 0.96 Runoff Coefficient 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Notes: For Type B Soils. use the average of coefficients Cu) and CA . When the Runoff Coefficient in above table is < 0, use 0. When compositing the Runoff Coefficient for different soil typ Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soils C & D 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Watershed Impervious Ratio 1.0 es, use the table values above regardless if they are < 0 100-yr —•-25-yr 10-yr a 5-yr 2-yr Runoff Coefficient Runoff Coefficient vs. Imperviousness NRCS Hydrologic Soil A 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Watershed Impervious Ratio 100-yr 25-yr 10-yr 5 yr 2-yr Page 4 I. One -hr Precipitation Values for Metro Denver Area Return period in years 2 5 10 50 100 Depth in inches 0.93 1.35 1.61 2.20 2.60 II. Recommended Runoff Coefficients for Metro Denver Land Use or Surface Characteristics Percent Imper- viousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family " Multiunit (detached) 60 Multiunit (attached) 75 Half -acre lot or larger Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks. cemeteries: 5 Playgrounds: 10 Schools: 50 Railroad yard areas: 15 Undeveloped areas: Historical Flow Analysis 2 Greenbelts. agricultural Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Driveways and sidewalks: 90 Roofs: 90 Lawns. sandy soil 0 Lawns. clayey soil 0 *Refer to Figures RO-3 through RO-5 in Runoff Chapter of USDCM. Page 5 List of Variables A= C= C1, O2, and C3 C5 I= ID = L= S= P1 = Tc Td Tf Tr Qp V= watershed area in acres runoff coefficient coefficients in IDF formula 5-yr runoff coefficient rainfall intensity in inches/hour user defined identification number flow length in ft slope for flow length in ft/ft one hour precipitation value in inches time of concentration in minutes design rainfall duration in minutes flow time in minutes return period in years peak runoff rate in cfs flow velocity in ft/second Island Grove PR 100 Yrs.xls, Notation 1/31/2023, 5:03 PM Stormwater Drainage Study Appendix E: GRASS SWALE CALCULATIONS T-2 Grass Swale RESIDUAL CAPACITY FOR LARGER FLOODS 1;,, • 4" (MIN) SANDY LOAM 6" MI IN _L 2-YR WSE 6" MI TRAPEZOIDAL SWALE SECTION NTS I RESIDUAL CAPACITY FOR LARGER FLOODS 2-YR WS•E 4'° MIN. SANDY LOAM 12" MIN. MIN. D 1.0' 12" MIN. (2-YR) 1.0 FPS !Y TRIANGULAR SIAN GULAR SWALE SECTION NTS CONCRETE COI I AR ENERGY DISSIPATION b ir. l' rf I PROVIDE DOUBLE CLEANOUTS WITH WATER TIGHT CAPS @150' O.O. USE 90* SWEEP OR (2) 45' BENDS (OFFSET FROM SWALE CENTERLINE TO AVOID IMPEDING FLOW WHEN USING A TRIANGULAR SECTION Design Example 1 4 MIN. GRADE CONTROL STRUCTURE BEYOND GRADE CONTROL STRUCTURE BEYOND UNDERDRAIN AND SANDY LOAM RECOMMENDED FOR LONGITUDINAL SLOPES < 2.0%. 4" SLOTTED PIPE MEETING TABLE 05-3 WITH CDOT CLASS C FILTER MATERIAL ALL AROUND OR PERFORATED HOPE PIPE WITH AASHTO #67 ALL AROUND CONTAINED WITHIN CEOTEXTILE FABRIC. ASTM D4751-AOS US STD. SIEVE #50 TO 7a, ASTM D4533 MIN. TRAPEZOIDAL TEAR STRENGTH 100 X 60 LBS, MINIMUM COE SPECIFIED OPEN AREA OF 4%. GRADE CONTROL EXTEND GRADE CTROL STRUCTURE STRUCTURES INTO ONTHE BANK A MIN. OS ABOVE THE 2-YR WSE Ii UNDERDRAIN ENSURE ACCESS TO OUTLET BY CLEAN OUT OR OTHER ACCESSIBLE STRUCTURE SWALE PROFILE NITS Figure GS -1. Grass Swale Profile and Sections The UD-BMP workbook, designed as a tool for both designer and reviewing agency is available at www.udfcd.org. This section provides a completed design form from this workbook as an example. GS -6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Hydraulic Analysis Report Project Data Project Title: Designer: Project Date: Monday, January 30, 2023 Project Units: U.S. Customary Units Notes: Channel Analysis: Swale A Notes: input Parameters Channel Type: Trapezoidal Side Slope 1 (Z1): 3.0000 ft/ft Side Slope 2 (Z2): 3.0000 ft/ft Channel Width 1.00 ft Longitudinal Slope: 0.0070 ft/ft Manning's n: 0.0350 Depth 1.0000 ft Result Parameters Flow 9.4932 cfs Area of Flow 4.0000 ft^2 Wetted Perimeter 7.3246 ft Hydraulic Radius 0.5461 ft Average Velocity 2.3733 ft/s Top Width 7.0000 ft Froude Number: 0.5533 Critical Depth 0.7608 ft Critical Velocity 3.8014 ft/s Critical Slope: 0.0247 ft/ft Critical Top Width 5.56 ft Calculated Max Shear Stress 0.43681b/ft^2 Calculated Avg Shear Stress 0.2385 lb/ft^2 CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 IN FO c©CLOU DBREAKEN ERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Traffic Narrative 1. Describe how many roundtrips/day are expected for each vehicle type: Passenger Cars/Pickups, Tandem Trucks, Semi-Truck/Trailer/RV (Roundtrip = One (1) trip in and One (1) trip out of site). • • • Maximum anticipated number of daily trips during peak period of construction: 10 - 15 vehicles per day during peak construction 7am - 3:30pm general hours Monday - Friday. % of heavy vehicles during peak period of construction: 5 - 10% During first few months of construction. Typical anticipated number of daily trips after construction is complete: 2 - 4 trips per year depending on O&M contract details. 2. Describe the expected travel routes or haul routes for site traffic. • The primary travel/haul route will be East on Highway 34, South onto County Road 47, East onto County Road 54, and then arriving at the Southern access point on the parcel. 3. Describe the travel distribution along the routes (e.g. 50% of traffic will come from the north, 20% from the south, 30% from the east, etc.). • 100% of the expected travel will follow the primary travel/haul route detailed above. 4. Describe the time of day that you expect the highest traffic volumes. • 7:00am - 3:30pm 1 a A Platte Rive Resort & E r. _ Island Grove Solar Site Northeast Quadrant of County Road 54 and County Road 47 Weld County, Colorado Traffic Letter KE Job #2023-025 Prepared for: TRC Companies, Inc. 123 N. College Avenue, Suite 206 Fort Collins, CO 80524 Prepared by: KELLAR ENGINEERING skellar@kellarengineering.com www.kellarengineering.com 970.219.1602 phone March 7, 2023 Sean K. Kellar, PE, PTOE This document, together with the concepts and recommendations presented herein, as an instrument of service, is intended only for the specific purpose and client for which it was prepared. Reuse of and improper reliance on this document without written authorization from Kellar Engineering LLC shall be without liability to Kellar Engineering LLC. 1.0 Introduction The purpose of this Traffic Letter is to evaluate the proposed traffic generated by the proposed Island Grove Solar Site project located at the northeast quadrant of Weld County Road 54 (CR 54) and Weld County Road 47 (CR 47) in Weld County, CO near 23041 CR 54, Greeley, CO. 2.0 Proposed Development The proposed project consists of a solar field land use on the property. Access to the site is proposed from a low traffic volume access off of CR 54 on the south side of the property. See Figure 1: Vicinity Map and Figure 2: Site Plan. Figure 1: Vicinity Map KELLAR ENGINEERING Island Grove Solar Site Traffic Letter -Page 2 3.0 Trip Generation Site generated traffic estimates are determined through a process known as trip generation. Rates and equations are applied to the proposed land use to estimate traffic generated by the development during a specific time interval. The acknowledged source for trip generation rates is the Trip Generation Report published by the Institute of Transportation Engineers (ITE). The Institute of Transportation Engineers' (ITE) Trip Generation Manual does not provide detailed data on solar field facilities. As such, KE was able to estimate the weekday peak hour trip generation for the AM and PM peak hours based upon information provided by the client and project team. The project team provided the following trip generation data: Trip Generation Data: • Maximum anticipated number of daily trips per day during peak period of construction = 10 — 15 vehicles per day during peak construction 7:00 AM - 3:30 PM general hours Monday — Friday. • % of heavy vehicles during peak period of construction = 5% - 10% during first few months of construction. • Typical anticipated number of daily trips after construction is complete = 2 — 4 trips per year depending on O&M contract details • Approximately 50% of the traffic will come from the west on CR 54 and approximately 50% of the traffic will come from the east on CR 54. Based upon the above data, the project is conservatively anticipated to generate a maximum of approximately 48 daily trips, 24 total (14 entering, 10 exiting) AM peak hour trips, and 20 total (6 entering, 14 exiting) PM peak hour trips. See Table 1: Trip Generation. Island Grove Solar Site Traffic Letter -Page 3 rica KELLAR ENGINEERING Table 1: Trip Generation Average Daily Trips AM Peak Hour PM Peak Hour Trips Trips Code ITE Land Use Size Rate Total Rate In Rate Out Total Rate In Rate Out Total N/A Solar Field * * 48 * 14 * 10 24 * 6 * 14 20 N/A = Not Available The Institute of Transportation Engineers' (ITE) Trip Generation Manual, 11th Edition does not provide detailed data related to the proposed use. Therefore, trip generation is based upon information obtained from the client and project team. See Section 3.0 Trip Generation for more information Island Grove Solar Site Traffic Letter Page 5 KELLAR ENGINEERING 4.0 Conclusions: The findings of the Traffic Letter are summarized below: • The proposed project is conservatively anticipated to generate a maximum of approximately 48 daily total weekday trips, 24 AM total peak hour trips, and 20 PM total peak hour trips. See Table 1: Trip Generation • The project's trip generation and site generated traffic is low. See Table 1: Trip Generation. • Due to the project's low site generated traffic, the proposed project will not create a negative traffic impact upon the local and regional traffic system and the existing roadway improvements are sufficient to accommodate the project's traffic. See Section 3.0. • The anticipated number of daily trips after construction is complete is only 2 — 4 trips per year. See Section 3.0. KELLAR ENGINEERING Island Grove Solar Site Traffic Letter -Page 6 APPENDIX Island Grove Solar Site Traffic Letter -Page 7 rica KELLAR ENGINEERING Aerial Image KELLAR ENGINEERING Island Grove Solar Site Traffic Letter -Page 8 KELLAR ENGINEERING Sean Kellar, PE, PTOE Principal Engineer Education B.S., Civil Engineering, Arizona State University — Tempe, AZ Registration Colorado, Professional Engineer (PE) Wyoming, Professional Engineer (PE) Idaho, Professional Engineer (PE) Arizona, Professional Engineer (PE) Kansas, Professional Engineer (PE) Missouri, Professional Engineer (PE) Professional Traffic Operations Engineer (PTOE) Professional Memberships Institute of Transportation Engineers (ITE) Industry Tenure 23 Years WORK EXPERIENCE: Sean's wide range of expertise includes: transportation plan- ning, traffic modeling roadway design, bike and pedestrian facili- ties, traffic impact studies, traffic signal warrant analysis, parking studies, corridor planning and access management. Sean's experience in both the private and public sectors; passion for safety and ex- cellence; and strong communication and collaboration skills can bring great value to any project. Prior to starting Kellar Engineering, Sean was employed at the Missouri Department of Transportation (MoDOT) as the District Traffic Engineer for the Kansas City District. Sean also worked for the City of Loveland, CO for over 10 years as a Senior Civil Engineer supervising a division of transportation/traffic engineers. While at the City of Loveland, Sean managed several capital improvement projects, presented several projects to the City Council and Planning Commission in public hearings, and managed the revisions to the City's Street Standards. Sean is also proficient in Highway Capacity Software, Synchro, PT Vissim, Rodel, GIS, and AutoCAD. Kellar Engineering, Principal Engineer/President - January 2016 - Present Missouri Department of Transportation, District Traffic Engineer, Kansas City District - June 2015 - January 2016 City of Loveland, Colorado, Senior Civil Engineer, Public Works Department - February 2005 June 2015 Kirkham Michael Consulting Engineers, Project Manager - February 2004 - February 2005 Dibble and Associates Consulting Engineers, Project Engineer - August 1999 - February 2004 CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Alternatives Statement Cloudbreak Energy Partners performed a rigorous search for ideal solar project locations across the State of Colorado. This search included hundreds, if not thousands, of properties within Weld County. The Weinmeister's property was chosen due to several factors including, but not limited to: • Close proximity to high quality Xcel Energy distribution infrastructure that has the capacity for a project of this size • Close proximity to Xcel Energy's Rosedale substation • Outside of floodplains and wetlands • Relatively flat • No geotechnical constraints • Landowner participation • Limited disturbance to nearby properties and property owners Alternatives to the Weinmeister's property were thoroughly evaluated but were ultimately dismissed due to at least one of the above factors. The proposed Project presents the most viable design and location with the least adverse impacts of all the alternatives. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Development Standards Statement 1. Height limitation. Ground -mounted solar collectors shall not exceed twenty-five (25) feet in height, measured from the highest grade below each solar panel to the highest extent of the solar panel rotation.: o The ground -mounted solar collectors will not exceed 25' in height, as measured from the highest grade below each solar panel to the highest extent of the solar panel rotation. 2. Glare. Concentrated solar glare from solar collectors shall not be directed toward or onto nearby properties or roadways at any time of the day: o A glare study for the Project is included in the application materials. The risk of glare being directed toward or onto nearby properties or roadways will be mitigated with screening as described in the Landscape and Screening Plan. 3. Setbacks. The improved area shall conform to the setback requirements of the underlying zone. Additionally, the improved area must be at least five hundred (500) feet from existing residential buildings and residential lots of a platted subdivision or planned unit development. The residential setback requirement may be reduced if appropriate screening through landscape or an opaque fence is installed, or upon submittal to Weld County of a waiver or informed consent signed by the residence owner agreeing to the lesser setback. If landscaping or opaque fencing is substituted for setback, a landsca Ding plan or fencing plan shall first be submitted to and approved by the Department of Planning Services: o The Project conforms to the setback requirements of the Agricultural zone and will be seeking wiavers for neighbors within 500 feet of the project or using a screening around the project near residences. 4. Dust mitigation. The operators of the SEF shall continuously employ the practices for control of fugitive dust detailed in their dust mitigation plan submitted as required by Subsection B.2., above: o The Project will continuously employ the practices for control of fugitive dust detailed in the submitted Dust Mitigation Plan. (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM CLOUDBREAK PAGE 2 5. Underground cables. All electrical cables on the improved area shall be buried, except for direct current string wires that connect between solar collectors, direct current collection circuits between rows of solar arrays that are no more than four (4) feet above grade crossings, substations, switchyards, and circuit voltages greater than 34.5 kilovolts (where necessary): a All electrical cables on the improved area shall be buried, except for direct current string wires that connect between solar collectors, direct current collection circuits between rows of solar arrays that are no more than four (4) feet above grade crossings, substations, switchyards, and circuit voltages greater than 34.5 kilovolts (where necessary). 6. Fencing. The SEF shall be enclosed with a security fence as approved pursuant t0 a fencing plan submitted to the Department of Planning Services. Appropriate signage shall be placed upon such fencing that warns the public of the high voltage therein: a The Project will be enclosed by a 7 foot tall game fence. Additional details are provided in the Landscape and Screening Plan as well as the USR Map. 7. Stormwater management. The Operator of the SEF shall submit a drainage report to comply with required Storm Drainage Criteria pursuant to Chapter 8, Article XI of this Code. Additional requirements for Municipal Separate Storm Sewer System (MS4) areas may be applicable pursuant to Chapter 8, Article IX of this Code. Ground -mounted solar collector systems shall be exempt from impervious surface calculations if the soil under the collectors is designated hydrologic A or B soil groups by the Natural Resources Conservation Service (NRCS): o A drainage report has been submitted as part of the Project's application. 8. Access permit. Prior to construction of the SEF, the applicant shall apply for and obtain an approved Access Permit from the Weld County Department of Public Works, pursuant to the provisions of Article XIV of Chapter 8 of this Code: a Prior to construction of the Project, CBEP Solar 13, LLC or its contractors shall apply for and obtain an approved Access Permit from the Weld County Department of Public Works pursuant to the provisions of Article XIV of Chapter 8 of this Code. 9. Existing irrigation systems. The nature and location or expansion of the SEF must not unreasonably interfere with any irrigation systems on or adjacent to the solar facility. a The Project will not interfere with any irrigation systems on or adjacent to the solar facility. (970) 425-3175 I I N FO©a CLOU DBPEAKEN EPGY.COM I CLOU DBPEAKEN EPGY.COM CLOUDBREAK CBEP SOLAR 13, LLC PO BOX 1255 STERLING, CO 80751 (970) 425-3175 INFO c©CLOUDBREAKENERGY.COM DATE: April 24, 2023 PROJECT: Island Grove Solar Project SUBJECT: Utility and Other Infrastructure Owners Infrastructure Owner Name Address none (970) 425-3175 I I N FO©a CLOU DBREAKEN ERGY.COM I CLOUDBREAKENERGY.COM ERGY.COM Weld County Treasurer Statement of Taxes Due Account Number R3990206 Assessed To Legal Description PT S2SW4 24-5-65 LOT B REC EXEMPT RE -4137 (1.5D) Year Tax Charge 2022 Total Tax Charge Tax Interest $1,553.28 $0.00 Parcel 096124300036 WEINMEISTER DAVID L 23041 COUNTY ROAD 54 GREELEY, CO 80631-9767 Sites Address 23170 COUNTY ROAD 54 WELD Fees Payments Balance $0.00 ($1,553.28) $0.00 $0.00 Grand Total Due as of 04/24/2023 $0.00 Tax Billed at 2022 Rates for Tax Area 0698 - 0698 Authority WELD COUNTY SCHOOL DIST #6 NORTHERN COLORADO WATER (NC CENTRAL COLORADO WATER (CCW CENTRAL COLORADO WATER SURD LASALLE FIRE AIMS JUNIOR COLLEGE HIGH PLAINS LIBRARY WEST GREELEY CONSERVATION Taxes Billed 2022 * Credit Levy Mill Levy 15.0380000* 50 3990000 1 0000000 10680000 1.5820000 5 1540000 63070000 3.1810000 0.4140000 Amount $277.61 $930.37 $18.46 $19.71 $29 20 $95.14 $116.43 $58.72 $7.64 84.1430000 $1,553 28 Values AG -FLOOD IRRRIGATED LAND AG -WASTE LAND Total Actual $69,886 $16 Assessed $18,450 $10 $69,902 $18,460 ALL TAX LIEN SALE AMOUNTS ARE SUBJECT TO CHANGE DUE TO ENDORSEMENT OF CURRENT TAXES BY THE LIENHOLDER OR TO ADVERTISING AND DISTRAINT WARRANT FEES. CHANGES MAY OCCUR AND THE TREASURER'S OFFICE WILL NEED TO BE CONTACTED PRIOR TO REMITTANCE AFTER THE FOLLOWING DATES: PERSONAL PROPERTY, REAL PROPERTY, AND MOBILE HOMES - AUGUST 1 TAX LIEN SALE REDEMPTION AMOUNTS MUST BE PAID BY CASH OR CASHIER'S CHECK. POSTMARKS ARE NOT ACCEPTED ON TAX LIEN SALE REDEMPTION PAYMENTS PAYMENTS MUST BE IN OUR OFFICE AND PROCESSED BY THE LAST BUSINESS DAY OF THE MONTH - A44-12? fre 3 Weld County Treasurer's Office 1400 N 17th Avenue PO Box 458 Greeley, CO 80632 Phone: 970-400-3290 Pursuant to the Weld County Subdivision Ordinance, the attached Statement of Taxes Due issued by the Weld County Treasurer are evidence that as of this date, all current and prior year taxes related to this parcel have been paid in full. Date: Hello