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Home My WebLink AboutRIDGEWOOD HILLS FIFTH FILING - PDP190018 - SUBMITTAL DOCUMENTS - ROUND 4 - DRAINAGE REPORTPREPARED FOR: Goodwin Knight PREPARED BY: Galloway & Company, Inc. 5265 Ronald Regan Blvd., Suite 210 Johnstown, Colorado 80534 ORIGINAL PREPARATION: November 13, 2019 REVISED: February 12, 2020 June 3, 2020 RIDGEWOOD HILLS – FIFTH FILING FORT COLLINS, COLORADO PRELIMINARY DRAINAGE REPORT PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 2 of 16 I. CERTIFICATIONS ..................................................................................................................................... 3 CERTIFICATION OF ENGINEER .................................................................................................... 3 CERTIFICATION OF OWNER ......................................................................................................... 3 II. GENERAL LOCATION AND DESCRIPTION ........................................................................................... 4 SITE LOCATION .............................................................................................................................. 4 DESCRIPTION OF PROPERTY ...................................................................................................... 4 III. DRAINAGE BASINS AND SUB-BASINS ................................................................................................. 5 MAJOR BASIN DESCRIPTION ....................................................................................................... 5 SUB-BASIN DESCRIPTION ............................................................................................................ 5 IV. DRAINAGE DESIGN CRITERIA ............................................................................................................. 7 REGULATIONS ............................................................................................................................... 7 DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ................................................. 7 HYDROLOGICAL CRITERIA ........................................................................................................... 8 HYDRAULIC CRITERIA................................................................................................................... 9 V. DRAINAGE FACILITY DESIGN ............................................................................................................. 10 GENERAL CONCEPT ................................................................................................................... 10 VI. EROSION AND SEDIMENT CONTROL MEASURES .......................................................................... 13 VII. FLOODPLAIN ....................................................................................................................................... 14 VIII. CONCLUSIONS .................................................................................................................................. 15 COMPLIANCE WITH STANDARDS .............................................................................................. 15 VARIANCES .................................................................................................................................. 15 IX. REFERENCES ...................................................................................................................................... 16 Appendices: A. Appendix A – Reference Material B. Appendix B – Hydrologic Calculations C. Appendix C – Hydraulic Calculations D. Appendix D – Existing Drainage Study Excerpts E. Appendix E – Proposed Condition Drainage Map TABLE OF CONTENTS PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 3 of 16 I. CERTIFICATIONS CERTIFICATION OF ENGINEER “I hereby certify that this report for the preliminary drainage design of the Ridgewood Hills Fifth Filing was prepared by me (or under my direct supervision) in accordance with the provisions of the Fort Collins Stormwater Criteria Manual (December 2018) for the owners thereof.” To be signed and sealed at time of Final Drainage Report ______________________________________ Donald Bender Cecil, P.E. Registered Professional Engineer State of Colorado No. 0052303 For and on behalf of Galloway & Company, Inc. CERTIFICATION OF OWNER “Goodwin Knight hereby certifies that the drainage facilities for Ridgewood Hills Fifth Filing shall be constructed according to the design presented in this report. We understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed and/or certified by our engineer. We also understand that the City of Fort Collins relies on the representation of others to establish that drainage facilities are designed and constructed in compliance with City of Fort Collins guidelines, standards or specifications. Review by the City of Fort Collins can therefore in no way limit or diminish any liability, which we or any other party may have with respect to the design or construction of such facilities.” ____________________________________ Goodwin Knight Attest: ___________________________________ Name of Responsible Party __________________________________ Notary Public __________________________________ Authorized Signature PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 4 of 16 II. GENERAL LOCATION AND DESCRIPTION SITE LOCATION The Ridgewood Hills Fifth Filing (hereafter referred to as “the site” or “project site”) is a 34.81-acre project site located in the City of Fort Collins, Larimer County, Colorado. The project site is bound to the north by Triangle Drive, to the east by South College Avenue (US HWY 287), and to the south by undeveloped land. The west property boundary is adjacent to parkland and open space to the north and portions of Ridgewood Hills Filings Nos. 3 and 4 to the south. Ridgewood Hills Filing No. 4 is currently under construction. The project site is located on four separate parcels. Parcel 1 is described as Tract A of the Shenandoah P.U.D. Filing No. 1. Parcel 2 is described as a portion of the East ½ of the Southeast ¼ of Section 14, Township 6 North, Range 69 West of the 6th Prime Meridian, in Larimer County Colorado. Parcel 3 is described as a portion of the East ½ of the Southeast ¼ of Section 14, Township 6 North, Range 68 West of the 6th Prime Meridian, in Larimer County Colorado. Parcel 4 is described as a portion of the Tract C of the Shenandoah P.U.D. DESCRIPTION OF PROPERTY The 34.81-acre project site is currently undeveloped and consists of open fallow land. Vegetation on the project site consists of mostly invasive weeds and grasses. The project site currently drains from west to east at slopes ranging from 2% to 50%. The steeper slopes up to 50% occur adjacent to the east property boundary at South College Avenue. There are several existing delineated natural areas and buffer zones present on the site, as defined by Section 3.4.1 of the City of Fort Collins Land Use Code. There are four wetland areas delineated on the project site – two at the northeast corner of the site, near the intersection of Triangle Drive and South College Avenue, and two at the southwest corner of the site. A section of the North Loudon Ditch bisects the project site, which is also classified as a natural area. Proposed development that disturbs these areas and their buffer zones will require mitigation as required by the Land Use Code. An inlet swale bisects the north quarter of the site and conveys offsite drainage from the neighborhood to the north of Triangle Drive. Diverted flows owned by City of Fort Collins Natural Areas Department and emergency overflow flows from Louden Ditch also are conveyed through the inlet swale. The inlet swale drains to an existing 48” RCP under College Avenue that outlets to Robert Benson Lake to the east. Undetained offsite drainage areas, immediately to the west of the project site, were delineated as part of the Ridgewood Hills Filings No. 3. These offsite basins are currently being constructed as part of the Ridgewood Hills Filing No. 4. While the majority of the Filing No. 3 basins will be captured and detained with the construction of the Filing No. 4, a small portion of runoff generated from the Filing No. 4 development will flow undetained onto the project site. These offsite areas drain onto the project site and will be routed through as part of the project development. A copy of the drainage maps from the Ridgewood Hills Filing Nos. 3 and 4 are included in Appendix E. Proposed improvements with the Fifth Filing project include the construction of multi-family, single-family attached, and single-family detached residential units with associated roads, drives and utilities infrastructure. Detention of the project site will be divided amongst three separate constructed ponds that will control release rates to allowable measures. Stormwater quality features will be constructed to satisfy the City of Fort Collins Low Impact Development (LID), and Natural Areas mitigation requirements. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 5 of 16 According to the Natural Resources Conservation Service (NRCS) Web Soil Survey, the project site consists of a mix of soil types and Hydrologic Soil Groups (HSGs)including: - Fort Collins Loam, HSG ‘C’, 41.9% of total project area - Heldt Clay Loam, HSGs ‘C’, 12.2% - Longmont Clay, HSGs ‘D’, 18.2% - Renohill Clay Loam, HSGs ‘D’, 1.0% - Santana Loam, HSGs ‘B’, 9.7% - Wiley Silt Loam, HSGs ‘B’, 17.0% The predominant on-site HSG is ‘C’. Group C soils are described as 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. Refer to Appendix A, for the Web Soil Survey and soils information. A geotechnical report was prepared by CTL Thompson, Incorporated in August 2019 for the project site. The report included site-specific borings for the project site. Twelve exploratory borings were performed across the project site and discovered that subsurface conditions generally consisted of sandy clay over weathered and competent bedrock. Bedrock consisted primarily of sandy claystone. Groundwater was observed at depths of approximately 0.5’ to 23.5’ below the ground surface. Areas that experience shallow groundwater under the existing condition are located primarily at the south end of the site, at the location of the existing wetlands. The shallow groundwater present on the site contributes to the existing wetlands and should help reestablish wetlands within areas proposed as mitigation for those to be disturbed. Proposed site improvements, including the detention ponds, are determined to be above modeled groundwater levels as outlined in the geotechnical report. III. DRAINAGE BASINS AND SUB-BASINS MAJOR BASIN DESCRIPTION The project site is enveloped entirely within the Fossil Creek drainage basin, as delineated by the City of Fort Collins Drainage Basin Master Plan. The Drainage Basin Master Plan was approved by City Council in June of 2004 and describes the flooding history of the specified basins and offers guidance for new development within the basins. Onsite detention is required for the runoff volume difference between the 100-year developed flow rate and the 2-year historic release rate. In the Fossil Creek basin the two year historic release rate is 0.2 cfs/acre. The project site is shown on FEMA Map Number 08069C1200F. The floodplain map indicates the project exists within Zone X - Area of Minimal Flood Hazard and is, therefore, not impacted by an existing floodplain/floodway. Refer to Appendix A for a Firmette of the Flood Plain Hazard Map. SUB-BASIN DESCRIPTION The sub-basin development included herein is intended as a step toward informing future detailed preliminary and final storm drain infrastructure design. The developed drainage basins shown on sheets C5.0 and C5.1 will be further subdivided as the grading design evolves. A Basins: These basins are compositionally similar and comprised of the north and east portion of the project site, east of Strasburg Drive, Strasburg Drive, and portions of Castle View Drive, west of Strasburg PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 6 of 16 Drive. The composition of the development consists of the building roof areas from the multifamily buildings and clubhouse building, asphalt, curb and gutter, sidewalks, landscaping, and outdoor amenity areas. These basins are intended to be captured via the on-site drainage system and routed to Detention Pond A at the northeast corner of the site, near the intersections of College Avenue and Triangle Drive. The outlet flows from Detention Pond A will be routed to the inlet swale and eventually into the existing 48” RCP storm drain that passes under College Avenue and discharges into Robert Benson Lake. B Basins: These basins are compositionally similar and are comprised of a portion of the proposed Castle View Drive right-of-way; a portion of the Field View Drive right-of-way, north of Avondale Road; a portion of the east right-of-way of the Avondale Road extension, north of Field View Drive; and a portion of the detached single-family buildings to the south of Castle View Drive. The composition of development consists of paved roadways and sidewalks, paved parking areas, roof areas from detached single-family homes, landscaped areas and other hardscape. These basins are intended to be captured via the curb and gutter, overland flow and on-site storm sewer system and routed to Detention Pond B to the southwest of the intersection of Strasburg Drive and Castle View Drive. The outlet flows from Detention Pond B will be routed to the inlet swale via underground storm sewer and eventually into the existing 48” RCP storm drain that passes under College Avenue and discharges into Robert Benson Lake. C Basins: These basins are compositionally similar and are comprised of the Avondale Road right-of-way extension, south of Field View Drive; the detached single-family buildings to the north and south of Field View Drive, east of Avondale Road; the proposed Maroon Vista Way, Pyramid Vista Way and Long Vista Way; and the attached single-family buildings along Longmont Street and Field View Drive. The composition of development consists of paved roadways and sidewalks, paved parking areas, roof areas from attached and detached single-family homes, landscaped areas and other hardscape. These basins are intended to be captured via the on-site drainage system and routed to Detention Pond C at the southwest corner of the site. The outlet flows from Detention Pond C will be routed to the existing 24” RCP that runs parallel to the south property boundary and discharges into Stanton Creek on the east side of College Avenue. D Basins: These basins are not to be captured and conveyed offsite via the proposed on-site stormwater conveyance system. Basins D1 and D3 are comprised of a portion of roof areas of the west facing garage buildings along the east property line, landscaped areas, and sidewalk that runs parallel to College Avenue. Due to the location of these basins directly adjacent to the College Avenue right-of-way, runoff generated in these basins cannot be captured via the on-site drainage system and will runoff directly into College Avenue. Basin D2 consists of the Robert Benson Lake inlet swale from which all runoff is conveyed to the existing 48” RCP storm drain that passes under College Avenue and discharges into Robert Benson Lake. Basin D4 consists of landscaped areas, sidewalk and other hardscapes. Due to the location of this basin directly adjacent to the Triangle Drive right-of-way, runoff generated in these basins cannot be captured via the on-site drainage system and will runoff directly into Triangle Drive. Basin D5 is located at the southwest corner of the site and consists of the existing wetland area and buffers and a small amount of roof area, sidewalk, and landscaped area at the far southwest corner of the townhomes. Runoff from the small portion of developed area is expected to travel via overland flow across grassy buffers and vegetation before traveling across undisturbed open space. The delineated wetland areas and buffers within Basin D5 are to remain undeveloped as undisturbed wetland area. Ridgewood Hills Filings Nos. 3 and 4 Offsite Basins: These basins exist along the west property boundary. These basins were originally delineated with the Ridgewood Hills Filing No. 3 development PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 7 of 16 and consist of portions of single-family residential lots, paved roadway associated with the Avondale Road extension to the east, and undeveloped fallow land. Under current conditions, runoff from these basins sheet flow directly onto the project site. Upon completion of the Ridgewood Hills Filing No. 4, which is currently under construction, the Avondale Road extension and the majority of the developed areas will be captured and routed to existing detention ponds constructed with the Ridgewood Hills Filing No. 3. A small portion of Filing No. 4 along the west property boundary slopes sharply to the Fifth Filing project site and will not be captured and directed to the existing detention ponds. These areas will remain undeveloped and will primarily consist of lawn and landscaped areas. The basins will be diverted at the property boundary via a system of swales and curb and gutter and directed into the Ridgewood Hills Filing No. 5 underground storm sewer system. Shenandoah P.U.D. First Filing Offsite Basins: The basins consist of a developed neighborhood subdivision to the north of Triangle Drive. These basins were delineated with the Shenandoah P.U.D. First Filing development and consist of portions of single-family residential lots, paved roadways, sidewalk, landscape, and other hardscape. These basins are captured via a system of underground storm sewer that discharges on the project site into the Robert Benson Inlet Swale. The underground storm drain from the Shenandoah First Filing will be re-routed through the project site where it will discharge into the inlet swale and eventually into the 48” RCP culvert under College Avenue that discharges into Robert Benson Lake. Louden Irrigation Ditch: A portion of the Louden Irrigation Ditch bisects the existing project site. The ditch enters the site at the south property boundary, where it meanders across the property, generally from south to north. The ditch enters a culvert near the north property line at Triangle Drive where it passes under the street and resumes open-channel flow north of Triangle Drive. The Ridgewood Hills Fifth Filing project requires the relocation of the ditch. The ditch will still enter the site at the south property boundary where it will continue in its current configuration to a point north and west of the large existing wetland at the southwest corner of the site. There, the ditch will be intercepted and conveyed via a system of underground storm sewer to the north where it will connect to the Triangle Drive culvert and continue its current conveyance pattern. At one point, midway through the project site, the ditch will resume open channel flow as it crosses onto a neighboring property to the east. The ditch is then intercepted again within underground storm sewer as it re-enters the site further north, and continues toward Triangle Drive. IV. DRAINAGE DESIGN CRITERIA REGULATIONS This preliminary drainage design presented herein is prepared in accordance with the Fort Collins Stormwater Criteria Manual (December 2018). DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS The project site is enveloped entirely within the Fossil Creek drainage basin, as delineated by the City of Fort Collins Drainage Basin Master Plan. The Drainage Basin Master Plan was approved by City Council in June of 2004 and describes the flooding history of the specified basins and offers guidance for new development within the basins. Several site specific constrains helped develop the Low Impact Design Water Quality BMPs and detention pond design presented here. • The outfall for the proposed Detention Pond A and Detention Pond B is the inlet swale at the northeast corner of the site that drains to a 48” RCP culvert under South College Avenue. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 8 of 16 • The outfall for the proposed Detention Pond C is a 24” RCP storm sewer that runs parallel to the south property boundary. This storm sewer passes under South College Avenue where it discharges into Stanton Creek on the west side of South College Avenue. The 24” RCP was designed and constructed with the Ridgewood Hills P.U.D. Filing No. 3. • The project site currently drains from west to east at slopes ranging from 2% to 50%. The steeper slopes up to 50% occur adjacent to the east property boundary at South College Avenue, however slopes as great as 30% exist at several locations throughout the project site. • The property has direct frontage along South College Avenue to the east and Triangle Drive to the north. • The existing soils are unsuitable for infiltrating stormwater runoff and generally consist of clayey sand/sandy lean clay and/or lean clay with sand subsoils Due to the project site being encumbered by these constraints, we developed a strategy for implementing “The Four-Step Process” for stormwater quality management to the Maximum Extent Practicable (MEP). Each step is listed below along with a brief narrative describing the implementation strategy. Step 1 – Employ Runoff Reduction Practices All developed runoff from Drainage Basin A, B, and C will be routed through the on-site detention ponds. The detention ponds will restrict the flowrate of stormwater leaving the site and reduce the impact on downstream drainage areas. Further, the design will allow for greater than 75% of the project’s added impervious area will be routed through an approved LID water quality treatment Best Management Practice (BMP), including underwater stormwater quality chambers and rain garden/bioretention ponds. Step 2 – Implement BMPs that provide a Water Quality Capture Volume Approximately 75% or more of the project’s added impervious area will be routed through the underwater stormwater quality chambers or bioretention basins to meet the LID requirements set forth. Generated runoff from the majority of Basin B, which will not be routed through the LID BMPs, will be treated for water quality in extended detention basin within Detention Pond B before it is piped directly into the inlet swale that flows into the 48” RCP culvert under South College Avenue. Step 3 – Stabilize Drainageways The existing Louden Ditch is to be removed and replaced with an underground storm drain. The Robert Benson Lake Inlet Swale will be preserved to the greatest extent possible. Contributing areas to the inlet swale will be piped across the project site. Earthen swales and embankments exceeding slopes of 4:1 (horizontal: vertical) will be planted to stabilize the shallow embankments and prevent erosion. Step 4 – Implement site specific and other source control BMPs An erosion control plan and Stormwater Management Plan will be implemented to prevent erosion and control sediment on the project site and downstream drainageways during and after construction. HYDROLOGICAL CRITERIA For urban catchments that are not complex and generally 160 acres or less in size, it is acceptable to estimate the design storm runoff with the rational method. The rational method is often used when only the peak flow rate or total volume of runoff is needed (e.g., inlet sizing, storm sewer sizing or simple detention basin sizing). The Rational Method is based on the Rational Formula: Q = CiA PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 9 of 16 where: Q = the maximum rate of runoff, cfs C = a runoff coefficient that is the ratio between the runoff volume from an area and the average rate of rainfall depth over a given duration for that area i = average intensity of rainfall in inches per hour for a duration equal to the time of concentration A = area, acres The runoff coefficient, C, for each basin is a weighted average of the runoff coefficient associated with each zoning classifcation type (e.g., commercial = 0.85). Refer to Appendix A and Tables 3.2-1 and 3.2-3 which list runoff coefficient associated with each zoning classification type and the Frequency Adjustment Factors (Cf) that were used to adjust the runoff coefficients for lower probability storm events. The one-hour rainfall Intensity-Duration-Frequency tables for use with the Rational Method of runoff analysis are provided in Table 3.4.1 (refer to Appendix B). The 2-year and 100-year storm events serve as the basis for the drainage system design. The 2-year storm is considered the minor storm event. It has a fifty percent probability of exceedance during any given year. The 100-year storm is considered the major storm event. It has a one percent probability of exceedance in any given year. The 2-year drainage system, at a minimum, must be designed to transport runoff from the 2-year recurrence interval storm event with minimal disruption to the environment. The 100-year drainage system, as a minimum, must be designed to convey runoff from the 100-year recurrence interval flood to minimize life hazards and health, damage to structures, and interruption to traffic and services. HYDRAULIC CRITERIA The storm drain system is limited to culverts and swales on the project site that will convey runoff underneath drives and parking areas to the water quality and detention BMPs. The storm drain system hydraulic analysis will completed in a future submittal using Bentley StormCAD V8i. This software routes flows based on the longest upstream Time of Concentration (tc) at each junction. Given the controlling tc, StormCAD V8i calculates the flow at the junction with the corresponding intensity (e.g., i2 and i100) and aggregate CA. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 10 of 16 V. DRAINAGE FACILITY DESIGN GENERAL CONCEPT The preliminary design presents the design of a system for collecting and conveying developed runoff from the proposed development at the Ridgewood Hills Fifth Filing project site into the on-site water quality and detention BMPs. Developed runoff will generally consist generally of flows generated from roof areas, paved roads/drives and parking areas, landscaped areas, and hardscape. The developed runoff for each basin begins as overland flow at numerous locations throughout the project site. The runoff then flows via a stormwater conveyance system consisting of swales, curb and gutter, and underground storm sewer into the assigned water quality BMPs above ground detention ponds. Significant work is required beyond that which is included herein to design the on-site stormwater conveyance and water quality and detention system. This work includes: • fine grading design; • further sub-basin delineation; • area inlet design; • swale design; • storm drain system design (i.e., hydraulic grade line analysis). SPECIFIC DETAILS A Basins These basins comprise approximately 9.14 acres. The developed runoff from these basins is captured via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff from the A Basins is diverted through the below ground water quality treatment basins. Runoff treated in the below ground water quality treatment basins are then conveyed via underground storm sewer to Detention Pond A. The total contributing area from A Basins to the underground water quality treatment system is 7.85 acres. The underground water quality treatment system will be comprised on the Stormtech Subsurface Stormwater Management System (Stormtech) manufactured by Advanced Drainage Systems, Inc., which is an allowed method by the City of Fort Collins for the Low Impact Development (LID) stormwater management technique requirements. Stormtech utilizes underground stormwater collection chambers to achieve the necessary volume required to be treated for Water Quality. The captured volume then infiltrates through a filtering fabric at the floor of the chamber, removing contaminants. An underdrain system then captures the filtered runoff and conveys the runoff to the on-site detention pond. The required water quality capture volume routed through the chambers was determined using the City of Fort Collins Modified FAA Method for the 2-year Return Period. Calculations for the sizing of the Underground Water Quality System are included in Appendix C. All on-site detention ponds were sized using City of Fort Collins Modified FAA Method for the 2-year Return Period. The proposed release rate for the detention ponds were determined using the allowable 0.2 cfs per acre of project area for projects within the Fossil Creek Drainage Basin. The allowable release rate for Pond A was calculated to be 1.8 cubic feet per second (cfs). The pond has a volume of 135,581 cubic feet and provides the required detention control for the 100-year return period. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 11 of 16 Calculations for the sizing of the Detention Pond A are included in Appendix C. The detention pond will discharge via an outlet structure that is connected to underground storm sewer that conveys discharge from the pond directly into the Robert Benson Lake Inlet Swale and eventually to the 48” RCP culvert under South College Avenue. B Basins These basins comprise approximately 3.97 acres. The developed runoff from these basins is captured via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff from the B Basins is conveyed via the underground storm sewer into Detention Pond B. The allowable release rate for Pond B was calculated to be 0.8 cubic feet per second (cfs). The pond has a volume of 60,646 cubic feet and provides the required detention control for the 100-year return period. In addition to detention for the 100-year return period, the basin will be designed as an extended detention basin (EDB) to capture the required water quality volume for the B Basins. Calculations for the sizing of the Detention Pond B are included in Appendix C. The detention pond will discharge via an outlet structure that is connected to underground storm sewer that conveys discharge from the pond directly into the Robert Benson Lake Inlet Swale and eventually to the 48” RCP culvert under South College Avenue. C Basins These basins comprise approximately 15.61 acres. The developed runoff from these basins is captured via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff from the C Basins is diverted trough an above ground bioretention/rain garden system. Runoff treated in the bioretention/rain garden system will infiltrate into a below ground underdrain system that conveys treated runoff to proposed wetland mitigation areas. Developed runoff from the C basins and will drain into a Bioretention Pond. The UDFCD defines a Bioretention Pond as “A BMP that utilizes bioretention is an engineered, depressed landscape area designed to capture and filter or infiltrate the water quality capture volume (WQCV). BMPs that utilize bioretention are frequently referred to as rain gardens or porous landscape detention areas (PLDs).” During storm events exceeding the water quality event, the bioretention pond is designed to fill to the design volume and spill excess runoff into the detention pond. The incoming runoff will spill through a weir designed to pass the 100-year incoming flows at a flow depth of 18”. The downstream face of the spillway will be protected with a turf reinforcement mat. The spillway and downstream protection are designed for peak 100-year developed runoff entering the bioretention pond and passing through the wier. The downstream spillway slope is exposed because the water surface elevation in the detention pond has not reached the weir elevation. The allowable release rate for Detention Pond C was calculated to be 3.1 cubic feet per second (cfs). The pond has a volume of 172,862 cubic feet and provides the required detention control for the 100-year return period. Calculations for the sizing of the Detention Pond C are included in Appendix C. The detention pond will discharge via an outlet structure that is connected to underground storm sewer that conveys discharge from the pond directly into the 24” RCP storm sewer that runs parallel to the south property boundary and was constructed with the Ridgewood Hills Filing No. 3 project. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 12 of 16 Avondale Road Improvements An extension of Avondale Road is proposed with the Ridgewood Hills Fifth Filing. The road will be dedicated as public right-of-way and will connect the northwest corner of the proposed development to the southeast corner of the site. The roadway will connect to an extension of Avondale Road to the project’s west property line that is currently under construction with the Ridgewood Hills Filing No. 4. A series of curb inlets in Avondale to be constructed within Filing No. 4 will intercept runoff before it shall continue southeast down the portion of Avondale Drive proposed with this project. Runoff generated within the right-of-way associated with the Fifth Filing will be conveyed via the proposed curb and gutter to curb inlets on the Fifth Filing project site. Runoff captured in the curb inlets will convey runoff via the underground storm sewer system into the proposed on-site detention ponds. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 13 of 16 VI. EROSION AND SEDIMENT CONTROL MEASURES A General Permit for Stormwater Discharge Associated with Construction Activities issued by the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division (WQCD), will be acquired for the project site. Prior to any earth disturbing activity a Stormwater Management Plan (SWMP) will be prepared to identity the Control Measures which, when implemented, will meet the requirements of said General Permit. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 14 of 16 VII. FLOODPLAIN According to FEMA FIRM Map Numbers 08069C1200F - effective date: 12/19/2006, the project site resides in Zone X – Area of Minimal Flood Hazard. Refer to Appendix A, pages A-X and A-X for the FIRM Map and Firmette. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 15 of 16 VIII. CONCLUSIONS COMPLIANCE WITH STANDARDS The design presented in this preliminary drainage report for Ridgewood Hills Fifth Filing has been prepared in accordance with the design standards and guidelines presented in the Fort Collins Stormwater Criteria Manual. VARIANCES No variance(s) requested at this time. PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing) June 3, 2020 Galloway & Company, Inc. Page 16 of 16 IX. REFERENCES 1. Fort Collins Stormwater Criteria Manual (December (2018) 2. Urban Drainage and Flood Control District, Drainage Criteria Manual Volumes 1 and 2, prepared by Wright-McLaughlin Engineers, originally published March 1969 and updated August 2018, and the Volume 3, prepared by Wright-McLaughlin Engineers, originally published September 1992 and updated April 2018. ` APPENDIX A REFERENCE MATERIAL ` VICINITY MAP SCALE: NTS VICINITY MAP S. COLLEGE AVE W. TRILBY RD SITE CARPENTER RD TRIANGLE DRIVE AVONDALE ROAD STRASBURG DRIVE ` NRCS SOILS MAP Hydrologic Soil Group—Larimer County Area, Colorado (Ridgewood Hills - Fifth Filing) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/6/2019 Page 1 of 4 4481000 4481100 4481200 4481300 4481400 4481500 4481600 4481700 4481800 4481000 4481100 4481200 4481300 4481400 4481500 4481600 4481700 4481800 493000 493100 493200 493300 493400 493500 493000 493100 493200 493300 493400 493500 40° 29' 14'' N 105° 5' 1'' W 40° 29' 14'' N 105° 4' 33'' W 40° 28' 46'' N 105° 5' 1'' W 40° 28' 46'' N 105° 4' 33'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 200 400 800 1200 Feet 0 50 100 200 300 Meters Map Scale: 1:4,250 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C 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 The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 37 Fort Collins loam, 5 to 9 percent slopes C 15.8 41.9% 49 Heldt clay loam, 3 to 6 percent slopes C 4.6 12.2% 63 Longmont clay, 0 to 3 percent slopes D 6.9 18.2% 90 Renohill clay loam, 3 to 9 percent slopes D 0.4 1.0% 96 Satanta loam, 3 to 5 percent slopes B 3.7 9.7% 108 Thedalund loam, 3 to 9 percent slopes C 0.0 0.0% 119 Wiley silt loam, 3 to 5 percent slopes B 6.4 17.0% Totals for Area of Interest 37.7 100.0% Hydrologic Soil Group—Larimer County Area, Colorado Ridgewood Hills - Fifth Filing Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/6/2019 Page 3 of 4 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 C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), 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 Hydrologic Soil Group—Larimer County Area, Colorado Ridgewood Hills - Fifth Filing Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/6/2019 Page 4 of 4 ` FEMA FIRMETTE 01820/69C1200F19/2006 Not Printed AREA OF MINIMAL Zone FLOOD X HAZARD T6N R69W S14 T6N R69W S13 T6N R69W S23 T6N R69W S24 CITY OF 080102 FORT COLLINS LARIMER 080101 COUNTY USGS The National Map: Orthoimagery. Data refreshed April, 2019. National Flood Hazard Layer FIRMette 0 250 500 1,000 1,500 2,000 Feet Ü 105°5'1.75"W 40°29'12.38"N 105°4'24.30"W 40°28'45.01"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT HAZARD SPECIAL FLOOD AREAS Without Zone A, V, Base A99 Flood Elevation (BFE) With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas depth areasdrainage of less less than than one one foot square or with mile Zone X Future ChanceAnnual Conditions Flood Hazard 1% Zone X Area Levee.to with See Reduced Notes. Flood Risk due Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This digital map flood complies maps if with it is FEMA's not void standards as described for the below. use of The accuracy basemap standards shown complies with FEMA's basemap The authoritative flood hazard NFHL information web services is derived provided directly by FEMA. from This the map was reflectnot exported changes on or 11/amendments 6/2019 at 11:subsequent 19:16 AM to and this does date and time. becomeor The superseded NFHL and effective by new data information over time. may change This elementsmap map image do not is appear: void if basemap the one or imagery, more of flood the following zone labels, legend, FIRM panel scale number, bar, map and creation FIRM effective date, community date. Map identifiers,images for unmapped regulatoryfor purposes. and unmodernized areas cannot be used Legend OTHER FLOOD AREAS HAZARD OF OTHER AREAS STRGUECNTUERREASL FEATURES OTHER MAP PANELS 8 ` APPENDIX B HYDROLOGY CALCULATIONS ` PROPOSED RUNOFF CALCULATIONS FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins Subdivision: Triangle Development Project Name: Triangle Development Location: CO, Fort Collins Project No.: Calculated By: HHF Checked By: HHF INPUT User Input Date: 6/2/20 OUTPUT Calculated Value Single-Family Alley-Loaded SF Duplex/AttachedMulti-Family 95% 5% 60% 70% 75% 80% A1 0.72 95 0.00 0 20 0.72 20 60 0.00 0 0.85 A2 3.24 95 0.00 0 20 3.24 20 60 0.00 0 0.85 A3 1.81 95 0.00 0 20 1.81 20 60 0.00 0 0.85 A4 0.71 95 0.00 0 21 0.71 21 61 0.00 0 0.85 A5 1.06 95 0.00 0 22 1.06 22 62 0.00 0 0.65 A6 0.31 95 0.00 0 23 0.31 23 63 0.00 0 0.65 pondA 1.29 95 0.00 0 20 1.29 20 60 0.00 0 0.20 7.85 B1 0.25 95 0.00 0 20 0.25 20 60 0.00 0 0.65 B2 1.78 95 0.00 0 20 1.78 20 60 0.00 0 0.65 B3 0.90 95 0.00 0 20 0.90 20 60 0.00 0 0.65 B4 0.18 95 0.00 0 20 0.18 20 60 0.00 0 0.65 pondB 0.86 95 0.00 0 20 0.86 20 60 0.00 0 0.20 3.11 C1 2.46 95 0.00 0 20 2.46 20 60 0.00 0 0.65 C2 0.23 95 0.00 0 20 0.23 20 60 0.00 0 0.65 C3 0.20 95 0.00 0 20 0.20 20 60 0.00 0 0.85 C4 0.46 95 0.00 0 20 0.46 20 60 0.00 0 0.85 C5 0.24 95 0.00 0 20 0.24 20 60 0.00 0 0.85 C6 1.11 95 0.00 0 20 1.11 20 60 0.00 0 0.85 C7 0.96 95 0.00 0 20 0.96 20 60 0.00 0 0.65 C8 1.07 95 0.00 0 20 1.07 20 60 0.00 0 0.85 C9 1.03 95 0.00 0 20 1.03 20 60 0.00 0 0.85 C10 0.34 95 0.00 0 20 0.34 20 60 0.00 0 0.85 C11 0.17 95 0.00 0 20 0.17 20 60 0.00 0 0.85 C12 0.49 95 0.00 0 20 0.49 20 60 0.00 0 0.65 C13 1.12 95 0.00 0 20 1.12 20 60 0.00 0 0.85 C14 1.61 95 0.00 0 20 1.61 20 60 0.00 0 0.85 C15 0.60 95 0.00 0 20 0.60 20 60 0.00 0 0.85 C16 0.51 95 0.00 0 20 0.51 20 60 0.00 0 0.65 pondC 3.02 95 0.00 0 20 3.02 20 60 0.00 0 0.20 12.59 D1 0.29 95 0.00 0 20 0.29 20 60 0.00 0 0.20 D2 0.96 96 0.00 0 21 0.96 21 61 0.00 0 0.20 D3 0.60 97 0.00 0 22 0.60 22 62 0.00 0 0.20 D4 0.23 98 0.00 0 23 0.23 23 63 0.00 0 0.20 D5 3.83 95 0.00 0 20 3.83 20 60 0.00 0 0.20 5.91 Σ Basins 34.64 ΣDetention Pond Tributary Area 28.73 COMPOSITE RUNOFF COEFFICIENTS Basin ID Total Area (ac) Runoff Coefficient Area (ac) Lots (e.g., Single-Family, Alley Loaded) Runoff Coefficient Area (ac) Area Weighted Asphalt + Concrete Walks Lawns, Heavy Soil: Flat <2% Area Weighted Subdivision: Triangle Development Project Name: Triangle Development Location: CO, Fort Collins Project No.: Calculated By: HHF Checked By: HHF Date: 6/2/20 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 21 22 23 24 BASIN D.A. Hydrologic C2 C5 C100 L S Ti | 2-Year Ti | 100-Year L Calculated S Cv VEL. Tt COMP. Tc | 2-Year COMP. Tc | 100-Year TOTAL Urbanized Tc Tc | 2-Year Tc | 100-Year ID (AC) Soils Group Cf=1.00 Cf=1.00 Cf=1.25 (FT) (%) (MIN) (MIN) (FT) Slope, % (%) (FPS) (MIN) (MIN) (MIN) LENGTH(FT) (MIN) (MIN) (MIN) A1 0.72 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0 0.4 0.1 2 10.0 5.0 5.0 A2 3.24 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 A3 1.81 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 A4 0.71 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 A5 1.06 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 A6 0.31 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 pondA 1.29 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 0.00 B1 0.25 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 B2 1.78 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 B3 0.90 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 B4 0.18 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 pondB 0.86 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 0.00 C1 2.46 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 C2 0.23 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 C3 0.20 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C4 0.46 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C5 0.24 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C6 1.11 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C7 0.96 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 C8 1.07 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C9 1.03 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C10 0.34 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C11 0.17 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C12 0.49 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 C13 1.12 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C14 1.61 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C15 0.60 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0 C16 0.51 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0 pondC 3.02 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 0.00 D1 0.29 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 D2 0.96 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 D3 0.60 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 D4 0.23 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 D5 3.83 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0 NOTES: Ti = (1.87*(1.1 - CCf)*(L)^0.5)/((S)^0.33), S in % Cv Tt=L/60V 2.5 Velocity V=Cv*S^0.5, S in ft/ft 5 Tc Check = 10+L/180 7 For urbanized basins a minimum Tc of 5.0 minutes is required. 10 For non-urbanized basins a minimum Tc of 10.0 minutes is required 15 20 DATA Type of Land Surface Heavy Meadow Tillage/Field Short Pasture and Lawns (Tt) (URBANIZED BASINS) Paved Areas and Shallow Paved Swales Project Name: Triangle Development Subdivision: Triangle Development Project No.: GNK10.20 Location: CO, Fort Collins Calculated By: HHF Design Storm: Checked By: HHF Date: TRAVEL TIME STREET Design Point Basin ID Area (Ac) Runoff Coeff. | C 2 Tc | 2-Year (min) C*A (Ac) I (in/hr) Q (cfs) Tc (min) C*A (Ac) I (in/hr) Q (cfs) Slope (%) Street Flow (cfs) Design Flow (cfs) Slope (%) Pipe Size (inches) Length (ft) Velocity (fps) Tt (min) REMARKS A1 A1 0.72 0.85 5.0 0.61 2.85 1.7 A2 A2 3.24 0.85 5.0 2.75 2.85 7.8 A3 A3 1.81 0.85 5.0 1.54 2.85 4.4 A4 A4 0.71 0.85 5.0 0.60 2.85 1.7 A5 A5 1.06 0.65 5.0 0.69 2.85 2.0 A6 A6 0.31 0.65 5.0 0.20 2.85 0.6 A pondA 1.29 0.20 5.0 0.26 2.85 0.7 B1 B1 0.25 0.65 5.0 0.16 2.85 0.5 B2 B2 1.78 0.65 5.0 1.16 2.85 3.3 B3 B3 0.90 0.65 5.0 0.58 2.85 1.7 B4 B4 0.18 0.65 5.0 0.12 2.85 0.3 B pondB 0.86 0.20 5.0 0.17 2.85 0.5 C1 C1 2.46 0.65 5.0 1.60 2.85 4.6 C2 C2 0.23 0.65 5.0 0.15 2.85 0.4 C3 C3 0.20 0.85 5.0 0.17 2.85 0.5 C4 C4 0.46 0.85 5.0 0.39 2.85 1.1 C5 C5 0.24 0.85 5.0 0.20 2.85 0.6 C6 C6 1.11 0.85 5.0 0.95 2.85 2.7 C7 C7 0.96 0.65 5.0 0.62 2.85 1.8 C8 C8 1.07 0.85 5.0 0.91 2.85 2.6 C9 C9 1.03 0.85 5.0 0.87 2.85 2.5 C10 C10 0.34 0.85 5.0 0.29 2.85 0.8 C11 C11 0.17 0.85 5.0 0.14 2.85 0.4 C12 C12 0.49 0.65 5.0 0.32 2.85 0.9 C13 C13 1.12 0.85 5.0 0.96 2.85 2.7 C14 C14 1.61 0.85 5.0 1.36 2.85 3.9 C15 C15 0.60 0.85 5.0 0.51 2.85 1.4 C16 C16 0.51 0.65 5.0 0.33 2.85 0.9 C pondC 3.02 0.20 5.0 0.60 2.85 1.7 D1 D1 0.29 0.20 5.0 0.06 2.85 0.2 D2 D2 0.86 0.20 5.0 0.17 2.85 0.5 D3 D3 0.60 0.20 5.0 0.12 2.85 0.3 STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) Project Name: Triangle Development Subdivision: Triangle Development Project No.: GNK10.20 Location: CO, Fort Collins Calculated By: HHF Design Storm: Checked By: HHF Date: TRAVEL TIME STREET Design Point Basin ID Area (Ac) Runoff Coeff. | C 100 Tc | 100-Year (min) C*A (Ac) I (in/hr) Q (cfs) Tc (min) C*A (Ac) I (in/hr) Q (cfs) Slope (%) Street Flow (cfs) Design Flow (cfs) Slope (%) Pipe Size (inches) Length (ft) Velocity (fps) Tt (min) REMARKS A1 A1 0.72 1.06 5.0 0.76 9.95 7.6 A2 A2 3.24 1.06 5.0 3.44 9.95 34.3 A3 A3 1.81 1.06 5.0 1.92 9.95 19.1 A4 A4 0.71 1.06 5.0 0.75 9.95 7.5 A5 A5 1.06 0.81 5.0 0.86 9.95 8.5 A6 A6 0.31 0.81 5.0 0.26 9.95 2.5 A pondA 1.29 0.25 5.0 0.32 9.95 3.2 7.85 B1 B1 0.25 0.81 5.0 0.20 9.95 2.0 B2 B2 1.78 0.81 5.0 1.45 9.95 14.4 B3 B3 0.90 0.81 5.0 0.73 9.95 7.3 B4 B4 0.18 0.81 5.0 0.15 9.95 1.5 B pondB 0.86 0.25 5.0 0.22 9.95 2.2 2.93 C1 C1 2.46 0.81 5.0 2.00 9.95 19.9 C2 C2 0.23 0.81 5.0 0.19 9.95 1.8 C3 C3 0.20 1.06 5.0 0.21 9.95 2.1 C4 C4 0.46 1.06 5.0 0.49 9.95 4.9 C5 C5 0.24 1.06 5.0 0.26 9.95 2.5 C6 C6 1.11 1.06 5.0 1.18 9.95 11.8 C7 C7 0.96 0.81 5.0 0.78 9.95 7.7 C8 C8 1.07 1.06 5.0 1.14 9.95 11.3 C9 C9 1.03 1.06 5.0 1.09 9.95 10.9 C10 C10 0.34 1.06 5.0 0.37 9.95 3.6 C11 C11 0.17 1.06 5.0 0.18 9.95 1.8 C12 C12 0.49 0.81 5.0 0.40 9.95 3.9 C13 C13 1.12 1.06 5.0 1.19 9.95 11.9 C14 C14 1.61 1.06 5.0 1.71 9.95 17.0 C15 C15 0.60 1.06 5.0 0.64 9.95 6.3 ` APPENDIX C HYDRAULIC CALCULATIONS Project Number: GNK10.20 Date: 6/2/2020 Project Location: Fort Collins, Colorado Calculations By: HHF Pond Description: pondA User Input Cell: Blue Text 100-year 97027 0.91 2.23 9.14 1.8 0.2 minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet 5 300 9.95 24827 548 24279 0.56 10 600 7.72 38526 1097 37429 0.86 15 900 6.52 48807 1645 47161 1.08 20 1200 5.60 55893 2194 53699 1.23 25 1500 4.98 62131 2742 59389 1.36 30 1800 4.52 67670 3290 64380 1.48 35 2100 4.08 71263 3839 67425 1.55 40 2400 3.74 74657 4387 70270 1.61 45 2700 3.46 77701 4936 72766 1.67 50 3000 3.23 80596 5484 75112 1.72 55 3300 3.03 83166 6032 77133 1.77 60 3600 2.86 85636 6581 79055 1.81 65 3900 2.71 87907 7129 80777 1.85 70 4200 2.59 90477 7678 82799 1.90 75 4500 2.48 92822 8226 84596 1.94 80 4800 2.38 95018 8774 86244 1.98 85 5100 2.29 97139 9323 87816 2.02 90 5400 2.21 99260 9871 89389 2.05 95 5700 2.13 100982 10420 90562 2.08 100 6000 2.06 102803 10968 91835 2.11 105 6300 2.00 104799 11516 93283 2.14 110 6600 1.94 106496 12065 94431 2.17 115 6900 1.88 107893 12613 95280 2.19 120 7200 1.84 110189 13162 97027 2.23 Catchment 'C': Required Storage, ac-ft: Modified FAA Method- Storage Volume Calculations Inputs | Tributary Area Output | Detention Volume Return Period for Detention Control: Required Storage, cubic feet: Average Outflow Storage Volume Storage Volume Catchment Drainage Area, ac: Release Rate, cfs: Storm Duration Time Rainfall Intensity Inflow Volume Project Number: GNK10.20 Project Location: Fort Collins, Colorado Date: 6/2/2020 Calculations By: H. Feissner Pond Description: pondA User Input Cell: Blue Text Design Point: N/A Design Storm: WQCV Required Volume: 0 ft3 N/A ft Design Storm: N/A Required Volume: 0 ft3 N/A ft Design Storm: 100-year Required Volume: 97027 ft3 5033.5 ft Contour Elevation Contour Area Depth Incremental Volume Cummulative Volume Incremental Volume Cummulative Volume Cummulative Volume ft ft2 ft ft3 ft3 ft3 ft3 ac-ft 5025.90 0 0 0 0 0 0 0.0 5026.00 320 0.10 16 16 11 11 0.0 5027.00 5710 1.00 3015 3031 2461 2471 0.1 5028.00 8919 1.00 7315 10346 7255 9726 0.2 5029.00 11261 1.00 10090 20436 10067 19794 0.5 5030.00 13717 1.00 12489 32925 12469 32262 0.7 5031.00 16304 1.00 15011 47935 14992 47254 1.1 5032.00 19044 1.00 17674 65609 17656 64911 1.5 5033.00 21955 1.00 20500 86109 20482 85393 2.0 5034.00 25055 1.00 23505 109614 23488 108881 2.5 5035.00 28380 1.00 26718 136331 26700 135581 3.1 Detention Pond Stage-Storage Calculations Average End Area Method: Required Volume Water Surface Elevation Conic Volume Method: 100-year 5019 5021 5023 5025 5027 5029 5031 5033 5035 5037 0 20000 40000 60000 80000 100000 120000 140000 160000 Contour Elevation, ft Cummulative Volume, ft3 Stage - Storage | pondA Project Number: GNK10.20 Date: 6/2/2020 Project Location: Fort Collins, Colorado Calculations By: HHF Pond Description: pondA - LID Calculations User Input Cell: Blue Text 2-year 13112 0.73 0.30 9.14 1.8 0.2 minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet 5 300 2.85 5689 548 5141 0.12 10 600 2.21 8823 1097 7726 0.18 15 900 1.87 11199 1645 9553 0.22 20 1200 1.61 12855 2194 10662 0.24 25 1500 1.43 14273 2742 11531 0.26 30 1800 1.30 15570 3290 12280 0.28 35 2100 1.17 16349 3839 12510 0.29 40 2400 1.07 17087 4387 12700 0.29 45 2700 0.99 17786 4936 12850 0.30 50 3000 0.92 18365 5484 12881 0.30 55 3300 0.87 19103 6032 13071 0.30 60 3600 0.82 19642 6581 13062 0.30 65 3900 0.78 20241 7129 13112 0.30 70 4200 0.73 20401 7678 12723 0.29 75 4500 0.70 20960 8226 12734 0.29 80 4800 0.66 21080 8774 12305 0.28 85 5100 0.64 21718 9323 12396 0.28 90 5400 0.61 21918 9871 12047 0.28 95 5700 0.58 21998 10420 11578 0.27 100 6000 0.56 22357 10968 11389 0.26 105 6300 0.54 22637 11516 11120 0.26 110 6600 0.52 22836 12065 10771 0.25 115 6900 0.51 23415 12613 10802 0.25 120 7200 0.49 23475 13162 10313 0.24 Average Outflow Storage Volume Storage Volume Catchment Drainage Area, ac: Release Rate, cfs: Storm Duration Time Rainfall Intensity Inflow Volume Catchment 'C': Required Storage, ac-ft: Modified FAA Method- Storage Colume Calculations Inputs | Tributary Area Output | Detention Volume Return Period for Detention Control: Required Storage, cubic feet: 1 2 3 4 5 6 7 8 9 10 11 12 13 UDSCM WQCV (CF) WQ FLOW (CFS) CHAMBER TYPE (A) RELEASE RATE/ CHAMBER (CFS) VOLUME/ CHAMBER (CF) VOLUME/ CHAMBER + AGGREGATE (CF) NUMBER OF CHAMBERS REQUIRED PER WQCV COMBINED RELEASE RATE WQCV METHOD (CFS) FAA REQUIRED STORAGE VOLUME (CF) NUMBER OF CHAMBERS PER FAA METHOD TOTAL VOLUME (CF) COMBINED RELEASE RATE FAA METHOD (CFS) TOTAL NUMBER OF CHAMBERS PROVIDED 9016 9.1 SC-740 0.024 45.9 74.9 121 2.85 13112 176 8078.4 4.15 176 85.4 51.0 4355.4 30.25 0.35 10.59 0.024 (A - COLUMN 4) FLOW RATE (GPM/SF) FLOW RATE PER CHAMBER (GPM) FLOW RATE PER CHAMBER (CFS)) Project Number: GNK10.20 Date: 6/2/2020 Project Location: Fort Collins, Colorado Calculations By: HHF Pond Description: pondB User Input Cell: Blue Text 100-year 30650 0.69 0.70 3.98 0.8 0.2 minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet 5 300 9.95 8197 238.8 7959 0.18 10 600 7.72 12720 477.6 12243 0.28 15 900 6.52 16115 716.4 15398 0.35 20 1200 5.60 18454 955.2 17499 0.40 25 1500 4.98 20514 1194 19320 0.44 30 1800 4.52 22343 1432.8 20910 0.48 35 2100 4.08 23529 1671.6 21858 0.50 40 2400 3.74 24650 1910.4 22739 0.52 45 2700 3.46 25655 2149.2 23506 0.54 50 3000 3.23 26611 2388 24223 0.56 55 3300 3.03 27459 2626.8 24832 0.57 60 3600 2.86 28275 2865.6 25409 0.58 65 3900 2.71 29025 3104.4 25920 0.60 70 4200 2.59 29873 3343.2 26530 0.61 75 4500 2.48 30648 3582 27066 0.62 80 4800 2.38 31373 3820.8 27552 0.63 85 5100 2.29 32073 4059.6 28013 0.64 90 5400 2.21 32773 4298.4 28475 0.65 95 5700 2.13 33342 4537.2 28804 0.66 100 6000 2.06 33943 4776 29167 0.67 105 6300 2.00 34602 5014.8 29587 0.68 110 6600 1.94 35162 5253.6 29909 0.69 115 6900 1.88 35624 5492.4 30131 0.69 120 7200 1.84 36382 5731.2 30650 0.70 Catchment 'C': Required Storage, ac-ft: Modified FAA Method- Storage Colume Calculations Inputs | Tributary Area Output | Detention Volume Return Period for Detention Control: Required Storage, cubic feet: Average Outflow Storage Volume Storage Volume Catchment Drainage Area, ac: Release Rate, cfs: Storm Duration Time Rainfall Intensity Inflow Volume Sheet 1 of 3 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 66.0 % B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.660 C) Contributing Watershed Area Area = 3.980 ac D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in Runoff Producing Storm E) Design Concept (Select EURV when also designing for flood control) 1 F) Design Volume (WQCV) Based on 40-hour Drain Time VDESIGN = 0.086 ac-ft (VDESIGN = (1.0 * (0.91 * i 3 - 1.19 * i 2 + 0.78 * i) / 12 * Area ) G) For Watersheds Outside of the Denver Region, VDESIGN OTHER = ac-ft Water Quality Capture Volume (WQCV) Design Volume (VWQCV OTHER = (d6 *(VDESIGN /0.43)) H) User Input of Water Quality Capture Volume (WQCV) Design Volume VDESIGN USER = ac-ft (Only if a different WQCV Design Volume is desired) I) NRCS Hydrologic Soil Groups of Tributary Watershed i) Percentage of Watershed consisting of Type A Soils HSG A = % ii) Percentage of Watershed consisting of Type B Soils HSG B = % iii) Percentage of Watershed consisting of Type C/D Soils HSG C/D = % J) Excess Urban Runoff Volume (EURV) Design Volume For HSG A: EURVA = 1.68 * i 1.28 EURVDESIGN = ac-f t For HSG B: EURVB = 1.36 * i 1.08 For HSG C/D: EURVC/D = 1.20 * i 1.08 K) User Input of Excess Urban Runoff Volume (EURV) Design Volume EURVDESIGN USER = ac-f t (Only if a different EURV Design Volume is desired) 2. Basin Shape: Length to Width Ratio L : W = : 1 (A basin length to width ratio of at least 2:1 will improve TSS reduction.) Project Number: GNK10.20 Project Location: Fort Collins, Colorado Date: 6/2/2020 Calculations By: H. Feissner Pond Description: pondB User Input Cell: Blue Text Design Point: N/A Design Storm: WQCV Required Volume: 3746 ft3 5047.87 ft Design Storm: N/A Required Volume: 0 ft3 N/A ft Design Storm: 100-year Required Volume: 34396 ft3 5051.1 ft Contour Elevation Contour Area Depth Incremental Volume Cummulative Volume Incremental Volume Cummulative Volume Cummulative Volume ft ft2 ft ft3 ft3 ft3 ft3 ac-ft 5046.00 0 0 0 0 0 0 0.0 5047.00 1941 1.00 971 971 647 647 0.0 5048.00 5495 1.00 3718 4689 3567 4214 0.1 5049.00 8340 1.00 6918 11606 6868 11083 0.3 5050.00 10784 1.00 9562 21168 9536 20618 0.5 5051.00 13258 1.00 12021 33189 12000 32618 0.7 5052.00 15815 1.00 14537 47726 14518 47136 1.1 5052.80 17983 0.80 13519 61245 13510 60646 1.4 Detention Pond Stage-Storage Calculations Required Volume Water Surface Elevation Average End Area Method: Conic Volume Method: 100-year 5019 5024 5029 5034 5039 5044 5049 5054 5059 0 10000 20000 30000 40000 50000 60000 70000 Contour Elevation, ft Cummulative Volume, ft3 Stage - Storage | pondA Project Number: GNK10.20 Date: 6/2/2020 Project Location: Fort Collins, Colorado Calculations By: HHF Pond Description: pondC User Input Cell: Blue Text 100-year 149167 0.83 3.42 15.61 3.1 0.2 minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet 5 300 9.95 38675 937 37738 0.87 10 600 7.72 60014 1873 58140 1.33 15 900 6.52 76028 2810 73218 1.68 20 1200 5.60 87066 3746 83320 1.91 25 1500 4.98 96784 4683 92101 2.11 30 1800 4.52 105412 5620 99793 2.29 35 2100 4.08 111010 6556 104453 2.40 40 2400 3.74 116296 7493 108803 2.50 45 2700 3.46 121038 8429 112608 2.59 50 3000 3.23 125547 9366 116181 2.67 55 3300 3.03 129550 10303 119247 2.74 60 3600 2.86 133398 11239 122159 2.80 65 3900 2.71 136935 12176 124759 2.86 70 4200 2.59 140939 13112 127826 2.93 75 4500 2.48 144592 14049 130543 3.00 80 4800 2.38 148013 14986 133027 3.05 85 5100 2.29 151317 15922 135394 3.11 90 5400 2.21 154620 16859 137762 3.16 95 5700 2.13 157302 17795 139507 3.20 100 6000 2.06 160140 18732 141408 3.25 105 6300 2.00 163249 19669 143581 3.30 110 6600 1.94 165892 20605 145287 3.34 115 6900 1.88 168069 21542 146527 3.36 120 7200 1.84 171645 22478.4 149167 3.42 Catchment 'C': Required Storage, ac-ft: Modified FAA Method- Storage Colume Calculations Inputs | Tributary Area Output | Detention Volume Return Period for Detention Control: Required Storage, cubic feet: Average Outflow Storage Volume Storage Volume Catchment Drainage Area, ac: Release Rate, cfs: Storm Duration Time Rainfall Intensity Inflow Volume Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 76.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.760 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 548,460 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 11,149 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 8337 sq ft D) Actual Flat Surface Area AActual = sq ft E) Area at Design Depth (Top Surface Area) ATop = sq ft F) Rain Garden Total Volume VT= cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) Donald Cecil Galloway & Company, Inc. June 2, 2020 Ridgewood Hills Filing No. 5 | C BASINS Fort Collins, CO UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO GNK10.20_UD-BMP_v3.07, RG 6/2/2020, 4:15 PM Project Number: GNK10.20 Project Location: Fort Collins, Colorado Date: 6/2/2020 Calculations By: H. Feissner Pond Description: pondC User Input Cell: Blue Text Design Point: N/A Design Storm: WQCV Required Volume: 0 ft3 N/A ft Design Storm: N/A Required Volume: 0 ft3 N/A ft Design Storm: 100-year Required Volume: 149167 ft3 5050.5 ft Contour Elevation Contour Area Depth Incremental Volume Cummulative Volume Incremental Volume Cummulative Volume Cummulative Volume ft ft2 ft ft3 ft3 ft3 ft3 ac-ft 5041.50 0 0 0 0 0 0 0.0 5042.00 949 0.50 237 237 158 158 0.0 5043.00 4382 1.00 2666 2903 2457 2615 0.1 5044.00 8159 1.00 6271 9173 6173 8788 0.2 5045.00 11636 1.00 9898 19071 9846 18635 0.4 5046.00 14952 1.00 13294 32365 13259 31894 0.7 5047.00 18637 1.00 16795 49159 16761 48655 1.1 5048.00 22985 1.00 20811 69970 20773 69428 1.6 5049.00 28575 1.00 25780 95750 25729 95157 2.2 5050.00 35910 1.00 32243 127993 32173 127330 2.9 5051.10 47129 1.10 45671 173664 45532 172862 4.0 Detention Pond Stage-Storage Calculations Required Volume Water Surface Elevation Average End Area Method: Conic Volume Method: 100-year 5038 5040 5042 5044 5046 5048 5050 5052 5054 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000 Contour Elevation, ft Cummulative Volume, ft3 Stage - Storage | pondC Project Number: GNK10.20 Project Location: Fort Collins, Colorado Date: 6/2/2020 Calculations By: H. Feissner Pond Description: pondC - Bioretention/Rain Garden User Input Cell: Blue Text Design Point: N/A Design Storm: WQCV Required Volume: 11149 ft 3 5053.50 ft Design Storm: N/A Required Volume: 0 ft 3 N/A ft Design Storm: 100-year Required Volume: 0 ft 3 N/A ft Contour Elevation Contour Area Depth Incremental Volume Cummulative Volume Incremental Volume Cummulative Volume Cummulative Volume ft ft 2 ft ft 3 ft 3 ft 3 ft 3 ac-ft 5052.50 9703 0 0 0 0 0 0.0 5053.00 11129 0.50 5208 5208 5204 5204 0.1 5053.50 12735 0.50 5966 11174 5961 11165 0.3 5054.40 13551 0.90 11829 23003 11827 22992 0.5 Detention Pond Stage-Storage Calculations Required Volume Water Surface Elevation Average End Area Method: Conic Volume Method: 5038 5040 5042 5044 5046 5048 5050 5052 5054 ` APPENDIX D DRAINAGE MAPS + VARIANCE APPLICATION EXISTING DRAINAGE STUDY EXCERPTS 8-UNIT 8-UNIT 6-UNIT 6-UNIT TOT LOT SPORTS COURT (110' X 50') CLUB HOUSE POOL AVONDALE ROAD TRIANGLE DRIVE 2' CURB CUT RIP RAP TYPE VL AS SHOWN D50=6" 1 N1 0.353 0.36 N2 0.36 2 N3 0.41 3 N4 0.33 4 5 6 7b 8 9 N5 0.55 0.276 0.301 0.211 1.872 12 STORM A PIPE - (45) STORM A PIPE - (44) FLOW TO EX. POND 1 EXISTING DETENTION POND 7a 11b 52.11 LF 12" HDPE @ 5.95% YARD INLET LATERALS HDPE N-12 (TYP) YARD INLET LATERALS HDPE N-12 (TYP) STORM A PIPE - (63) CDOT TYPE D AREA INLET STMH A1 EXISTING INLET CORE 8-UNIT 6-UNIT 24-UNIT 16-UNIT 16-UNIT 24-UNIT 24-UNIT PEYTON DRIVE AVONDALE ROAD TRIANGLE DRIVE RIP RAP TYPE VL AS SHOWN D50=6" 31 10 13 S2 0.125 0.25 S4 0.121 0.31 S5 0.125 0.29 S6 0.154 0.61 S7 0.155 0.25 S8 0.575 0.55 S9 0.112 0.63 S10 0.119 0.56 S11 0.201 0.46 S12 0.436 0.50 S13 0.041 0.45 S14 1.866 0.49 S15 1.153 0.66 S18 0.990 0.28 S17 0.810 0.18 S16 0.204 0.68 S19 0.352 0.25 14 15 16b 17 19 20 21 22 23 24 25 26 27 This unofficial copy was downloaded on Aug-27-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA This unofficial copy was downloaded on Aug-27-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA This unofficial copy was downloaded on Aug-27-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA This unofficial copy was downloaded on Aug-27-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA ` APPENDIX D DRAINAGE MAPS + VARIANCE DRAINAGE APPLICATION MAPS E T T T T T T acres C1 0.65 0.81 2.46 acres C2 0.20 0.25 0.23 acres A1 0.85 1.00 0.72 acres A3 0.85 1.06 1.81 acres pondB 0.20 0.25 0.86 acres C3 0.85 1.06 0.20 B1 acres A4 0.85 1.00 0.71 acres A5 0.65 0.81 1.06 acres pondA 0.20 0.25 1.29 acres A2 0.85 1.06 3.24 acres D1 0.20 0.25 T T T T T T T T T acres C8 0.85 1.00 1.07 acres C12 0.65 0.81 0.49 acres C13 0.85 1.00 1.12 acres C10 0.85 1.00 0.34 acres C14 0.85 1.00 1.61 acres C9 0.85 1.00 1.03 acres C7 0.65 0.81 0.96 acres C5 0.85 1.00 0.24 acres C6 0.85 1.00 1.11 acres pondC 0.20 0.25 3.02 acres C4 0.85 1.00 0.46 acres B1 0.65 0.81 0.25 acres D5 0.20 0.25 3.83 acres C15 0.85 1.00 0.60 acres C11 0.85 1.00 0.17 C8 C12 C13 C10 C14 C9 C7 C5 C6 C D5 C15 C16 C11 1 10 6 3 3 3 2 2 3 3 2 2 5 6 6 OFF-SITE RUNOFF FROM BASIN S13 OF RIDGEWOOD HILLS FOURTH FILING S13=0.35 ac 3 acres C16 0.65 0.81 0.51 - - - - - - - - - - - - - - STAMP Date: Drawn By: Project No: Checked By: # Date Issue / Description Init. RIDGEWOOD HILLS - FIFTH FILING PRELIMINARY UTILITY PLAN FORT COLLINS, CO THESE PLANS ARE AN INSTRUMENT OF SERVICE AND ARE THE PROPERTY OF GALLOWAY, AND MAY NOT BE DUPLICATED, DISCLOSED, OR REPRODUCED WITHOUT THE WRITTEN CONSENT OF GALLOWAY. COPYRIGHTS AND INFRINGEMENTS WILL BE ENFORCED AND PROSECUTED. COPYRIGHT GallowayUS.com 5265 Ronald Reagan Blvd., Suite 210 Johnstown, CO 80534 970.800.3300 PRELIMINARY NOT FOR BIDDING NOT FOR CONSTRUCTION 06.03.2020 GNK000010 JEP DBC LEGEND: PROPOSED STORM SEWER EXISTING STORM SEWER PROPOSED STORM INLET PROPOSED LOTLINE EASEMENT LINE EXISTING MINOR CONTOUR EXISTING MAJOR CONTOUR PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPERTY BOUNDARY EXISTING MANHOLE DRAINAGE SYMBOLS: DESIGN POINT MAJOR BASIN BOUNDARY (i.e., C-STORE) SUB-BASIN BOUNDARY (i.e., RATIONAL METHOD) OVERLAND FLOW DIRECTION (I.E., LANDSCAPING) DIRECT FLOW DIRECTION (I.E., PAVEMENT, CURB AND GUTTER) BASIN ID MINOR (2YEAR) RUNOFF COEFFICIENT MAJOR (100YEAR) RUNOFF COEFFICIENT BASIN AREA (ACRES) acres A1 0.23 0.45 1.00 A1 SCALE: 1"=60' 0 10 30 60 MATCHLINE-SEE SHEET C5.0 DRAINAGE PLAN C5.1 KEYMAP US HWY 287 STRASBURG DR TRIANGLE DR AVONDALE RD DRAINAGE NOTES PROPOSED OUTLET STRUCTURE PROPOSED STORM DRAIN PIPE PROPOSED STORM DRAIN INLET (CDOT TYPE R CURB INLET, No. 16 COMBINATION INLET, AREA INLET, ETC.) PROPOSED GRASS-LINED SWALE W/CONCRETE PAN PROPOSED RE-ALIGNMENT OF EXISTING IRRIGATION DITCH EXISTING IRRIGATION DITCH TO BE PROTECTED IN-PLACE PROPOSED INTERIM OUTFALL PROPOSED HEADWALL w/ORIFICE PLATE PROPOSED SIDEWALK CHASE PROPOSED BIORETENTION BASIN PROPOSED ADS STORMTECH SYSTEM EXISTING 48" OUTFALL TO ROBERT BENSON LAKE 1 2 3 4 5 6 7 8 9 10 11 12 C5.1 C5.0 0.29 acres D2 0.20 0.25 0.96 acres D3 0.20 0.25 0.60 acres D4 0.20 0.25 0.23 acres A6 0.65 0.81 0.31 C2 C1 A5 A4 A1 A2 A6 A3 A B C4 C3 B1 D1 D2 D3 D4 1 2 1 11 5 5 5 5 3 3 3 3 3 3 2 2 2 2 OFF-SITE RUNOFF FROM BASIN N7 OF RIDGEWOOD HILLS FOURTH FILING N7=0.90 ac 12 3 3 3 3 3 3 3 2 3 acres B2 0.65 0.81 1.78 acres B3 0.65 0.81 0.90 B4 acres B4 0.65 0.81 0.18 3 - - - - - - - - - - - - - - STAMP Date: Drawn By: Project No: Checked By: # Date Issue / Description Init. RIDGEWOOD HILLS - FIFTH FILING PRELIMINARY UTILITY PLAN FORT COLLINS, CO THESE PLANS ARE AN INSTRUMENT OF SERVICE AND ARE THE PROPERTY OF GALLOWAY, AND MAY NOT BE DUPLICATED, DISCLOSED, OR REPRODUCED WITHOUT THE WRITTEN CONSENT OF GALLOWAY. COPYRIGHTS AND INFRINGEMENTS WILL BE ENFORCED AND PROSECUTED. COPYRIGHT GallowayUS.com 5265 Ronald Reagan Blvd., Suite 210 Johnstown, CO 80534 970.800.3300 PRELIMINARY NOT FOR BIDDING NOT FOR CONSTRUCTION 06.03.2020 GNK000010 JEP DBC LEGEND: PROPOSED STORM SEWER EXISTING STORM SEWER PROPOSED STORM INLET PROPOSED LOTLINE EASEMENT LINE EXISTING MINOR CONTOUR EXISTING MAJOR CONTOUR PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPERTY BOUNDARY EXISTING MANHOLE DRAINAGE SYMBOLS: DESIGN POINT MAJOR BASIN BOUNDARY (i.e., C-STORE) SUB-BASIN BOUNDARY (i.e., RATIONAL METHOD) OVERLAND FLOW DIRECTION (I.E., LANDSCAPING) DIRECT FLOW DIRECTION (I.E., PAVEMENT, CURB AND GUTTER) BASIN ID MINOR (2YEAR) RUNOFF COEFFICIENT MAJOR (100YEAR) RUNOFF COEFFICIENT BASIN AREA (ACRES) acres A1 0.23 0.45 1.00 A1 SCALE: 1"=60' 0 10 30 60 DRAINAGE PLAN MATCHLINE-SEE SHEET C5.1 C5.0 KEYMAP US HWY 287 STRASBURG DR TRIANGLE DR AVONDALE RD C5.1 C5.0 DRAINAGE NOTES PROPOSED OUTLET STRUCTURE PROPOSED STORM DRAIN PIPE PROPOSED STORM DRAIN INLET (CDOT TYPE R CURB INLET, No. 16 COMBINATION INLET, AREA INLET, ETC.) PROPOSED GRASS-LINED SWALE W/CONCRETE PAN PROPOSED RE-ALIGNMENT OF EXISTING IRRIGATION DITCH EXISTING IRRIGATION DITCH TO BE PROTECTED IN-PLACE PROPOSED INTERIM OUTFALL PROPOSED HEADWALL w/ORIFICE PLATE PROPOSED SIDEWALK CHASE PROPOSED BIORETENTION BASIN PROPOSED ADS STORMTECH SYSTEM EXISTING 48" OUTFALL TO ROBERT BENSON LAKE 1 2 3 4 5 6 7 8 9 10 11 12 28 29 32 33 30 STORM B PIPE - (24) STORM B PIPE - (23) STORM B PIPE - (22) 34 16a EX. STM MANHOLE AND APPROX. 44 LF OF EX. 30" D/S STORM DRAIN TO BE REMOVED AND REPLACED AT GRADE SHOWN. 36.5 LF 24" RCP @ 2.00% 64.10 LF 12" HDPE @ 6.99% YARD INLET LATERALS HDPE N-12 (TYP) 5' TYPE R INLET RIM EL. = 5087.6 INV IN = 5077.68 INV OUT = 5075.93 STMH B1 20' TYPE R INLET 5' TYPE R INLET 6' DENVER #16 STMH B2 COMBO INLET STMH C1 TYPE D M-604-11 AREA INLET RIM EL. = 5070.0 STMH B3 STORM C PIPE - (34) CORE DRILL 12" HDPE STORM B PIPE - (21) STORM C PIPE - (59) 24" ADS AREA DRAIN RIM: 5091.50 INV: 5089.50 24" ADS AREA DRAIN RIM: 5090.44 INV: 5087.87 24" ADS AREA DRAIN RIM: 5094.25 INV: 5088.18 66.15 LF 12" HDPE @ 4.07% 24" ADS AREA DRAIN RIM: 5091.00 INV: 5085.05 24" ADS AREA DRAIN RIM: 5091.20 INV: 5085.09 24" ADS AREA DRAIN RIM: 5090.74 INV: 5087.57 24" ADS AREA DRAIN RIM: 5083.40 INV: 5078.42 24" ADS AREA DRAIN RIM: 5083.40 INV: 5078.83 24" ADS AREA DRAIN RIM: 5083.40 INV: 5079.05 53.65 LF 12" HDPE @ 1.0% 54.47 LF 12" HDPE @ 1.0% 7.00 LF 6" PVC @ 1.00% 7.00 LF 6" PVC @ 1.00% 2' SIDEWALK CHASE AND CURB CUT 7.00 LF 6" PVC @ 1.00% 7.00 LF 6" PVC @ 1.00% 35.54 LF 12" HDPE @ 5.97% STORM C PIPE - (60) CORE DRILL 12" HDPE 61.24 LF 12" HDPE @ 5.97% 72.51 LF 12" HDPE @ 5.97% 50.00 LF 12" HDPE @ 4.07% 6.65 LF 12" RCP @ 7.50% 16.4 LF 12" HDPE @ 2.01% 24" ADS AREA DRAIN RIM: 5083.32 INV: 5075.00 12.38 LF 6" PVC @ 1.00% 20.00 LF 8" HDPE @ 4.20% EXIST. FIRE HYDRANT IS TO BE RELOCATED CORE DRILL 12" HDPE 35.45 LF 12" HDPE @ 6.99% TEE 12" HDPE TEE 12" RCP 92.88 INV. 92.03 INV. 90.60 INV. 90.47 INV. 12" TEE INV=5084.21 28.27 LF 12" HDPE @ 1.0% 25.65 LF 12" HDPE @ 1.0% 20.07 LF 12" HDPE @ 1.0% 24" BASIN COVERED LID INV.=78.22 12" TEE 12" TEE INV.=78.57 INV.=78.76 2' SIDEWALK CHASE 95.45 INV. 95.38 INV. 94.60 INV. 94.54 INV. 89.45 INV. 89.38 INV. 88.65 INV. 88.57 2' SIDEWALK INV. CHASE 45.12 LF HDPE @ 1.75% 2' CURB CUT (TYP X3) SEE SEPARATE L.I.D. PLAN SET FOR SUBDRAIN DETAILS S1 0.560 0.43 8.0 LF 8" HDPE @ 2.05% 93.86 INV. 93.69 INV. 4' VALLEY PAN 24" ADS AREA DRAIN RIM: 5083.22 INV: 5081.22 87.11 LF 12" HDPE @ 1.75% 12" TEE INV: 5080.43 12" FES INV: 5078.90 EXISTING MANHOLE STORM C PIPE - (59) NORTH 0 15' 30' 60' 90' SCALE: 1"= 30'-0" MATCHLINE (SEE SHEET 6 OF 9) 1-800-922-1987 NOTES 1. SEE SHEET 5 FOR DRAINAGE DATA SUMMARY TABLE 2. SEE SHEETS 19 - 21 FOR STORM DRAIN PLAN & PROFILES. MATCHLINE (SAME SHEET) MATCHLINE (SAME SHEET) LEGEND: DRAINAGE BASIN I.D. DESIGN POINT OVERLAND FLOW DIRECTION # # 0.000 0.00 MINOR STORM RUNOFF COEFFICIENT DRAINAGE BASIN AREA (AC) CITY OF FORT COLLINS, COLORADO UTILITY PLAN APPROVAL THIS DRAWING, AS AN INSTRUMENT OF SERVICE, IS AND SHALL REMAIN THE PROPERTY OF TFG DESIGN, LLC. AND SHALL NOT BE REPRODUCED, PUBLISHED OR USED IN ANY WAY WITHOUT THE PERMISSION OF THE LANDSCAPE ARCHITECT. 1269 N Cleveland Ave, Loveland CO 80537 (970) 669.3737 design@tfgdesign.com www.tfgdesign.com ATTN: SHEET OF SHEET NUMBER: SHEET TITLE: REVISIONS: PROJECT INFORMATION: OWNER: DRAWN BY: FILE LOCATION: T:\Projects\1000 General\1053 TFG\1053-001 RidgewoodHills4th\DWGS\C2.0_Drainage Plans.dwg PLOT DATE: 11/19/2013 7:34 AM PROJECT NUMBER: DATE: PHASE: M. TIMM DEVELOPMENT BILL TIMM 233 CARILLO STREET SANTA BARBARA, CA 93101 (805) 963-0358 RIDGEWOOD HILLS FOURTH FILING AVONDALE RD & TRIANGLE FORT COLLINS, COLORADO 111-122FC AUG 07, 2014 FP 36 DRAINAGE PLAN SOUTH 6 6 SOUTH WALL OF INLET BOX TO ACCEPT PIPING FROM PROPOSED DEVELOPMENT STMH A2 W/ NEENAH R-2553 GRATE RIM EL. = 5080.33 INV. EL. (W) = 5075.30 INV. EL. (E) = 5075.10 24" ADS AREA DRAIN RIM: 5098.25 INV: 5096.25 24" ADS AREA DRAIN RIM: 5093.00 INV: 5091.00 24" ADS AREA DRAIN RIM: 5085.25 INV: 5083.25 24" ADS AREA DRAIN RIM: 5080.25 INV: 5078.25 24" ADS AREA DRAIN RIM: 5098.25 INV: 5095.30 12" TEE INV: 5089.90 12" TEE INV: 5082.76 24" ADS AREA DRAIN RIM: 5079.91 INV: 5077.45 24" ADS AREA DRAIN RIM: 5098.25 INV: 5095.79 24" ADS AREA DRAIN RIM: 5098.25 INV: 8093.60 24" ADS AREA DRAIN RIM: 5094.20 INV: 5090.81 24" ADS AREA DRAIN RIM: 5092.34 24" ADS AREA DRAIN RIM: 5092.76 INV: 5086.60 24" ADS AREA DRAIN RIM: 5088.15 INV: 5083.50 24" ADS AREA DRAIN RIM: 5084.85 INV: 5081.13 24" ADS AREA DRAIN RIM: 5084.50 INV: 5080.18 24" ADS AREA DRAIN RIM: 5094.25 INV: 5090.22 24" ADS AREA DRAIN RIM: 5094.25 INV: 5092.25 25.00 LF 12" HDPE @ 4.07% 45.82 LF 12" HDPE @ 1.00% 47.06 LF 12" HDPE @ 1.00% 46.83 LF 12" HDPE @ 3.64% 76.60 LF 12" HDPE @ 3.64% 76.12 LF 12" HDPE @ 1.16% 39.91 LF 12" HDPE @ 4.96% 36.83 LF 12" HDPE @ 6.05% 64.60 LF 12" HDPE @ 3.67% 23.78 LF 12" HDPE @ 0.51% 71.42 LF 12" HDPE @ 0.51% 79.12 LF 12" HDPE @ 1.20% 21.96 LF 12" HDPE @ 2.55% 68.75 LF 12" HDPE @ 0.33% 12" TEE INV: 5078.02 34.29 LF 12" HDPE @ 6.27% EXIST. 24" RCP EXIST. 36" RCP 12" ELBOW INV: 5083.13 12" ELBOW INV: 5090.79 37.30 LF 12" HDPE @ 5.78% 63.98 LF 12" HDPE @ 2.00% 12" HDPE INV: 5074.48 12" ELBOW INV: 5091.23 25.00 LF 12" HDPE @ 4.07% SEE SEPARATE L.I.D. PLAN SET FOR SUBDRAIN DETAILS S3 0.235 0.29 N6 0.830 0.71 N7 0.900 0.25 OS-1 0.401 0.61 18.42 LF 12" HDPE @ 1.16% NORTH 0 15' 30' 60' 90' SCALE: 1"= 30'-0" MATCHLINE (SEE SHEET 7 OF 9) DRAINAGE DATA SUMMARY TABLE 1-800-922-1987 LEGEND: DRAINAGE BASIN I.D. DESIGN POINT OVERLAND FLOW DIRECTION # # 0.000 0.00 MINOR STORM RUNOFF COEFFICIENT DRAINAGE BASIN AREA (AC) CITY OF FORT COLLINS, COLORADO UTILITY PLAN APPROVAL THIS DRAWING, AS AN INSTRUMENT OF SERVICE, IS AND SHALL REMAIN THE PROPERTY OF TFG DESIGN, LLC. AND SHALL NOT BE REPRODUCED, PUBLISHED OR USED IN ANY WAY WITHOUT THE PERMISSION OF THE LANDSCAPE ARCHITECT. 1269 N Cleveland Ave, Loveland CO 80537 (970) 669.3737 design@tfgdesign.com www.tfgdesign.com ATTN: SHEET OF SHEET NUMBER: SHEET TITLE: REVISIONS: PROJECT INFORMATION: OWNER: DRAWN BY: FILE LOCATION: T:\Projects\1000 General\1053 TFG\1053-001 RidgewoodHills4th\DWGS\C2.0_Drainage Plans.dwg PLOT DATE: 11/19/2013 7:34 AM PROJECT NUMBER: DATE: PHASE: M. TIMM DEVELOPMENT BILL TIMM 233 CARILLO STREET SANTA BARBARA, CA 93101 (805) 963-0358 RIDGEWOOD HILLS FOURTH FILING AVONDALE RD & TRIANGLE FORT COLLINS, COLORADO 111-122FC AUG 07, 2014 FP 36 NOTES 1. SEE SHEETS 19 - 21 FOR STORM DRAIN PLAN & PROFILES. DRAINAGE PLAN NORTH 5 5 5056 0 2000 4000 6000 8000 10000 12000 Contour Elevation, ft Cummulative Volume, ft3 Stage - Storage | pondC 3. Basin Side Slopes A) Basin Maximum Side Slopes Z = ft / ft (Horizontal distance per unit vertical, 4:1 or flatter preferred) 4. Inlet A) Describe means of providing energy dissipation at concentrated inflow locations: 0.086 5. Forebay A) Minimum Forebay Volume VFMIN = 0.002 ac-ft (VFMIN = 2% of the WQCV) B) Actual Forebay Volume VF = ac-ft C) Forebay Depth (DF = 18 inch maximum) D F = in D) Forebay Discharge i) Undetained 100-year Peak Discharge Q100 = cfs ii) Forebay Discharge Design Flow QF = cfs (QF = 0.02 * Q100 ) E) Forebay Discharge Design F) Discharge Pipe Size (minimum 8-inches) Calculated DP = in G) Rectangular Notch Width Calculated WN = in Flow too small for berm w/ pipe Design Procedure Form: Extended Detention Basin (EDB) Ridgewood Hills Filing No. 5 | B Basins Galloway & Company, Inc. June 2, 2020 Fort Collins, CO Herman Feissner UD-BMP (Version 3.07, March 2018) Choose One Excess Urban Runoff Volume (EURV) Choose One Wall with Rect. Notch Berm With Pipe Water Quality Capture Volume (WQCV) Wall with V-Notch Weir GNK10.20_UD-BMP_v3.07, EDB 6/2/2020, 4:12 PM SC-740 CHAMBER SPECIFICATIONS STORMTECH CHAMBER VOLUME AND RELEASE RATE CALCULATIONS CHAMBER LENGTH (IN) CHAMBER WIDTH (IN) CHAMBER FOOTPRINT (SQ IN) CHAMBER FOOTPRINT (SF) C16 C16 0.51 0.81 5.0 0.41 9.95 4.1 C pondC 3.02 0.25 5.0 0.75 9.95 7.5 12.59 D1 D1 0.29 0.25 5.0 0.07 9.95 0.7 D2 D2 0.86 0.25 5.0 0.22 9.95 2.1 D3 D3 0.60 0.25 5.0 0.15 9.95 1.5 D4 D4 0.23 0.25 5.0 0.06 9.95 0.6 D5 D5 3.83 0.25 5.0 0.96 9.95 9.5 5.81 100-Year DIRECT RUNOFF TOTAL RUNOFF STREET 6/2/20 PIPE Page 1 of 1 6/2/2020 D4 D4 0.23 0.20 5.0 0.05 2.85 0.1 D5 D5 3.83 0.20 5.0 0.77 2.85 2.2 DIRECT RUNOFF TOTAL RUNOFF STREET PIPE STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) 2-Year 6/2/20 Page 1 of 1 6/2/2020 Nearly Bare Ground Grassed Waterway STANDARD FORM SF-2 TIME OF CONCENTRATION SUB-BASIN Tc CHECK GNK10.20 FINAL INITIAL/OVERLAND (Ti) TRAVEL TIME Page 1 of 1 6/2/2020 Runoff Coefficient Area (ac) GNK10.20 Area Weighted C2 Page 1 of 1 6/2/2020 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 1:6,000 B 20.2 The point pin selected displayed by the on the user map and is does an approximate not represent an authoritative property location. of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 14, Sep 13, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (Ridgewood Hills - Fifth Filing) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/6/2019 Page 2 of 4