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APEX - HAVEN APARTMENTS - FDP210012 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
FINAL DRAINAGE REPORT 19 OLD TOWN SQUARE #238 | FORT COLLINS, CO 80524 | 970-530-4044 | www.unitedcivil.com A PEX -H AVEN A PARTMENTS Replat of Lots 1 and 2, The Slab Property Observatory Park Subdivision Fort Collins, CO Prepared for: Maxiiimo Development and Asset Management Group, LLC 720/730 West Prospect Road Fort Collins, CO 80526 Date: April 28, 2021 F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO i U19031_Drainage Report.docx April 28, 2021 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Apex-Haven Apartments Fort Collins, Colorado Project Number: U19031 Dear Staff: United Civil Design Group, LLC. is pleased to submit this Final Drainage Report for the Apex-Haven Apartments site in Fort Collins, Colorado. In general, this report serves to document the stormwater impacts associated with the proposed improvements related to the existing site. We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in the Fort Collins Stormwater Criteria Manual (FCSCM). This report was prepared in compliance with technical criteria set forth in both the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual and the Fort Collins Stormwater Criteria Manual. If you should have any questions or comments as you review this report, please feel free to contact us at your convenience. Sincerely, United Civil Design Group Colton Beck, PE Kevin Brazelton, PE Project Engineer Principal F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO ii U19031_Drainage Report.docx TABLE OF CONTENTS I. General Location and Description ......................................................................................................................1 A. Location and Project Description ................................................................................................. 1 B. Description of Property ................................................................................................................ 2 C. Floodplains ................................................................................................................................... 2 II. Drainage Basins and Sub-Basins .........................................................................................................................3 A. Major Basin Description ............................................................................................................... 3 B. Sub-Basin Description .................................................................................................................. 3 III. Drainage Design Criteria ....................................................................................................................................3 A. Regulations ................................................................................................................................... 3 B. Directly Connected Impervious Area (DCIA) ................................................................................ 3 C. Hydrological Criteria ..................................................................................................................... 4 D. Hydraulic Criteria.......................................................................................................................... 4 E. Modifications of Criteria .............................................................................................................. 4 IV. Drainage Facility Design .....................................................................................................................................4 A. General Concept ........................................................................................................................... 4 B. Specific Details ............................................................................................................................. 4 V. Erosion Control ................................................................................................................................................ 10 VI. Conclusions ..................................................................................................................................................... 10 A. Compliance with Standards ....................................................................................................... 10 B. Drainage Concept ....................................................................................................................... 10 C. Stormwater Quality .................................................................................................................... 10 VII. References ................................................................................................................................................... 11 APPENDICES APPENDIX A – Hydrology Calculations APPENDIX B – Hydraulic Calculations B.1 – Low Impact Development Calculations B.2 – Water Quality Calculations B.3 – Detention Pond and Orifice Calculations B.4 – Inlet Sizing Calculations B.5 – Storm Pipe Calculations B.6 – Curb Channel Calculations B.7 – Weir Calculation APPENDIX C – Referenced Materials APPENDIX D – Drainage Exhibits F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 1 U19031_Drainage Report.docx I.GENERAL LOCATION AND DESCRIPTION A.LOCATION AND PROJECT DESCRIPTION The Apex-Haven Apartments site (referred herein as “the site”) is proposed as a replat Lots 1 and 2 of The Slab Property, located in the southwest quarter of Section 14, T7N, R69W of the 6th P.M., City of Fort Collins, Larimer County, Colorado. The property, consisting of approximately 2.63 acres, is located immediately north of West Prospect Road, approximately 750- feet west of South Whitcomb Street and currently exists as a residential property with an apartment complex, two single family structures and a recently constructed detention pond. The proposed Apex-Haven site improvements are limited to 1.19 acres on the east side of the property, formerly recognized as “Lot 2” of the Slab Property. The recently developed portion of the property to the west (formerly known as Lot 1) is referred herein as “The Slab” property. The property is bounded by West Prospect Road to the south, a recently developed apartment complex to the west, a single- family residence to the east, and an existing apartment complex to the north. Stormwater on the site currently drains southeast via sheet flow to West Prospect Road and is then conveyed easterly to storm sewer infrastructure associated with the Old Town master drainage basin. The proposed development of the site consists of the restoration of two existing on-site single-family residences and the construction of a new apartment building with a 11,300-sf footprint. Associated with the apartment building and existing residence improvements are proposed drive lanes, parking, utilities, an underground water quality facility, and improvements to the existing on-site detention pond. On-site stormwater, both detained and undetained, is largely designed to discharge to West Prospect Road. FIGURE 1:SITE VICINITY MAP This drainage report presents the overall drainage plan for the development. In general, this report serves to provide an analysis of the drainage impacts associated with the development of site as it relates to existing and proposed drainage facilities on-site. W Prospect Rd S WhitcombStW Lake St F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 2 U19031_Drainage Report.docx B.DESCRIPTION OF PROPERTY The project site currently exists largely as a gravel and grass/weed landscape, and also includes concrete pavement and rooftop, comprising of an existing imperviousness of 11.6%. In its historic condition, the site primarily sheet flows in two general directions: southeast where it is conveyed to West Prospect Road, and off-site to the north and northeast. In its existing (non-historic) condition, a minor portion of the site drains to a recently constructed detention pond associated with the development of “The Slab” property to the west. Similar to historic flows, runoff conveyed to the existing detention pond is ultimately released to West Prospect Road. Below are summaries of key components of the site in its existing conditions. Land Use - The site’s current land use is residential. Ground Cover - The site exists with two residential homes with gravel/dirt driveways and surrounding weed/grass landscaping. The weed/grass cover is good (ie., heavy or dense cover with nearly all ground surfaces protected by vegetation). Existing Topography – Historically, the site slopes in two general directions: northeasterly and southeasterly. Approximately the southern half of the property drains southeasterly to West Prospect Road, and minor portion of this area drains initially to a recently constructed detention pond associated with the development to the west. The northern portion of the site drains off-site to the northeast. Grades – In general, the northern portion of the site is sloped northeasterly at approximately 1.0% to 5.0%; the southern portion of the site is sloped southeasterly at approximately 1.0% to 10.0% Soil Type - The USDA’s Web Soil Survey shows that the site consists of a “Type B” soil. The Web Soil Survey indicates the site is comprised of Altvan Santana Loams (0 to 3% slopes). The on-site soils provide moderate infiltration and are suitable for development. Utilities – The following dry utility lines run along the south side of the site: gas, electric, cable TV, fiber optic. Water mains are also present on the south side of the site within West Prospect Road. A recently constructed sanitary sewer service exists at the northwest portion of the site. Drainage Features and Storm Sewer – A recently constructed detention pond exists at the southwest corner of the site, releasing runoff to West Prospect Road immediately to the South. C.FLOODPLAINS The proposed development is not in a FEMA designated floodplain. According to the FEMA Flood Insurance Rate Map Panel, the site is zoned as an area outside of the 500-year floodplain. The FEMA FIRM Map is included in the appendix. FIGURE 2:FLOODPLAIN MAP F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 3 U19031_Drainage Report.docx II.DRAINAGE BASINS AND SUB-BASINS A.MAJOR BASIN DESCRIPTION The proposed development is located within the Old Town Basin, located primarily in Old Town Fort Collins. No known master planning improvements are associated with or adjacent to the site. B.SUB-BASIN DESCRIPTION “The Slab” portion of the property, formerly recognized as Lot 1, was previously analyzed in a Final Drainage Report entitled “The Slab,” dated September 21, 2016 by Northern Engineering. The development of this area provided the addition of concrete drives, and sidewalks. Improvements also included a detention pond on the Apex-Have site (formerly known as Lot 2). This recently constructed pond is re-analyzed in conjunction with the proposed on-site improvements. In its developed condition, runoff from the site will largely be directed south to the on-site detention pond either via overland flow to surface improvements or via proposed storm sewer. Due to site grading constraints, a portion of the site will continue to drain directly to West Prospect Road undetained. A minor portion of the site – a largely decreased area relative to historic conditions – is designed to continue draining off-site to the north and northeast. III.DRAINAGE DESIGN CRITERIA A.REGULATIONS The design criteria for this study are directly from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual and the Urban Storm Drainage Criteria Manuals Volumes 2, and 3 (referred to herein as USDCM). B.DIRECTLY CONNECTED IMPERVIOUS AREA (DCIA) With the adoption of the USDCM, the City has also adopted the “Four Step Process” that is recommended in Volume 3 of the USDCM in selecting structural BMPs for the redeveloping urban areas. The following portions of this summary describe each step and how it has been utilized for this project: Step 1 – Employ Runoff Reduction Practices The objective of this step is to reduce runoff peaks and volumes and to employ the technique of “minimizing directly connected impervious areas” (MDCIA). This project accomplishes this by: Routing the roof and pavement flows through a bioretention facility, underground water quality treatment/infiltration facilities and vegetated swales to increase time of concentration, promote infiltration and provide water quality. Step 2 – Provide Water Quality Capture Volume (WQCV) The objective of providing WQCV is to reduce the sediment load and other pollutants that exit the site. For this project WQCV is provided within underground treatment facilities and a bioretention pond. Step 3 – Stabilize Drainageways The site is not adjacent or near a major drainageway; however, this project will pay stormwater development and stormwater utility fees which the City uses, in part, to maintain the stability of the City drainageway systems. Step 4 – Consider Need for Site Specific and Source Control BMPs Site specific and source control BMPs are generally considered for large industrial and commercial sites. The redevelopment of the existing site will include multiple site specific and source controls, including: Dedicated maintenance personnel providing landscape maintenance and snow and ice management. Dedicated dog park. F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 4 U19031_Drainage Report.docx C.HYDROLOGICAL CRITERIA City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, provided by Figure RA-16 of the Fort Collins Stormwater Criteria Manual, are utilized for all hydrologic computations related to the site in its existing/historic and proposed conditions. Since this site is relatively small and does not have complex drainage basins, the peak flow rates for design points have been calculated based on the Rational Method as described in the USDCM and the City of Fort Collins Stormwater Criteria Manual (FCSCM) with storm duration set equal to the time of concentration for each sub-basin. This method was used to analyze the developed runoff from the 10-year (minor) and the 100-year (major) storm events. The Rational Method is widely accepted for drainage design involving small drainage areas (less than 160 acres) and short time of concentrations. Runoff coefficients are assumed based on impervious area and are given in the Appendices. D.HYDRAULIC CRITERIA The developed site will convey runoff to the proposed pond or underground treatment facility via swales, concrete channels, and pipes. The City of Fort Collins Stormwater Criteria Manual (FCSCM) and USDCM are referenced for all hydraulic calculations. In addition, the following computer programs are utilized: Storm Sewer Extension for AutoCAD Civil3D Hydraflow Express Extension for AutoCAD Civil3D UD-Inlet by UDFCD Drainage conveyance facility capacities proposed with the development project, including storm sewer, swales, and inlet capacities, are designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria Manual (UDFCD). E.MODIFICATIONS OF CRITERIA Hardships related to a lack of public storm sewer adjacent to the site and the limited number of solutions available to the site due to the historic preservation requirements of existing on-site residences present difficulties in limiting the release of on- site runoff to the historic 2-year event. A separate variance request has been submitted to allow a design of the proposed site that provides runoff release to West Prospect Road, in addition to release off-site the north, at values that do not exceed the historic 100-year condition. Moreover, a bioretention pond related to the site improvements is designed with a 6-in bioretention media section, as opposed to a standard 18-in section per City of Fort Collins standards. Finally, due to area constraints associated with maintaining existing trees adjacent to Pond B, the detention volume for the pond is inclusive of the water quality volume required for the basin. IV.DRAINAGE FACILITY DESIGN A.GENERAL CONCEPT Developed runoff is designed to be conveyed in a safe and effective manner via swales, concrete channels, and storm sewer systems/inlets. Stormwater is designed to be released to West Prospect Road at a rate equivalent to the 100-year historic flow rate. Runoff that drains off-site to the north is heavily reduced with the proposed site; runoff from the site in its improved condition is primarily conveyed to bioretention, detention, and underground water quality facilities, all of which are designed at the southern end of the property. Due to grading constraints, not all on-site runoff is fully detained - these areas are considered in the overall release rate from the site. B.SPECIFIC DETAILS Hydrology As previously stated, hydrology from the developed site is designed to comply with criteria set forth in the City of Fort Collins Stormwater Criteria Manual with exception of the modifications stated in the “Modification of Criteria” section. Referenced tables, charts, formulas, etc. are included in the appendices. The area, time of concentration, and runoff of each proposed F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 5 U19031_Drainage Report.docx sub-basin is summarized in Appendix A. The following information outlines the basin characteristics and drainage patterns for each basin. On-site Basins The following basins provide proposed drainage delineations for the site in its improved condition. Note that Basins S1 and ON1 are per “The Slab” report by Northern Engineering. Refer to Appendix A for hydrology computations and Appendix B for calculations related to Detention, Water Quality, Low Impact Development, and other hydraulic features. Basin A Sub-basins A1-A3 (see Drainage Plan attached) are generally located around the south and southeast region of the site. These basins consist of roofs, concrete paving, and landscaping. Runoff within these Basins is conveyed to an underground water quality system (Pond A) via inlets and downspouts. Runoff conveyed to the underground water quality system is ultimately discharged southeast of the site to West Prospect Road via a concrete curb channel. Basin B Sub-basins B1-B3 represent on-site drainage basins where runoff is captured and conveyed to an on-site bioretention and detention pond (Pond B). These basins consist of roofs, concrete paving and landscaping. Sub-basin B1 largely consists of the pond area - runoff within this area drains directly to the pond via sheet flow or by means of storm sewer related to “The Slab” property. Runoff within sub-basin B2 is conveyed to the Pond B via curb and a concrete channel, and runoff within sub-basin B3 is conveyed to Pond B via a roof drain system. The proposed pond area is designed to receive flows from “The Slab” property immediately west of the site, however, these flows are treated by upstream, off-site infrastructure. An outlet structure is proposed with the mentioned pond and is designed to release stormwater to West Prospect Road. Basin C Sub-basins C1 and C2 consists primarily of roofing, concrete walks, and landscaped area. Runoff within these basins is conveyed to a proposed detention pond (Pond C) via sheet flow and storm sewer/roof drains. Basin D Sub-basins D1 and C2, consists primarily of landscaped area and concrete pavement. Due to grading constraints, runoff developed within these basin drains off-site undetained to the south and southeast via sheet flow. Basin E Basin E1, similar to Basins D1 and D2, consists primarily of landscaped area concrete pavement. Due to grading constraints, runoff developed within this basin drains off-site undetained to the north and northeast via sheet flow. Basin ON1 Basin ON1 is a drainage basin associated with the design and construction of “The Slab” property, per the Northern Engineering Final Drainage Report. This approved drainage report provided a design with runoff draining off-site to the north. The on-site improvements are expected to have negligible impact on the original design of Basin ON1. Basin S1 Basin S1 is a drainage basin associated with the design and construction of “The Slab” property, per the Northern Engineering Final Drainage Report. This approved drainage report provided a design with runoff draining further on-site form the west. The on-site improvements are expected to have negligible impact on the original design of Basin S1. Stormwater Quality I.Underground Water Quality An underground water quality facility is designed to divert storm water runoff during the water quality event and treat the flows through infiltration prior to being collected within an underdrain system. This provides for the removal of sediment and other pollutants from the runoff while also promoting infiltration. Underground water F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 6 U19031_Drainage Report.docx quality chambers are designed to collect and treat storm water runoff from Basins A1-A3 and Basins C1-C2 prior to being released to West Prospect Road. The underground water quality system, designated as “Pond A” is designed with a volume of 248-cf which exceeds the minimum design requirements for the area (195-cf). Below is a summary table for water quality related to all “A” and “C” Basins. Refer to Appendix B for additional information. Pond WQCV Required (cf) WQCV Provided (cf) WQ Release Rate (cfs) Pond A 195 248 0.13 II.Bioretention Bioretention is designed to remove sediment and pollution from stormwater runoff via infiltration through an engineered sand media. This slows the conveyance rate of storm water runoff, reduces runoff and provides a flow path across a vegetated surface. A bioretention pond is proposed with the site improvements and is utilized to convey and treat stormwater prior to release to West Prospect Road. The proposed bioretention pond, a reconstruction of the existing detention pond, is designed to maintain its existing top-of-pond elevation per “The Slab” Final Drainage Report. Moreover, the pond in its existing condition is designed to overflow to the south in West Prospect Road – the overflow weir will remain as designed despite reconstruction. Per “The Slab” report, the original pond was designed with excess capacity of approximately 3,000-cf for detention; however, the proposed site improvements require detention of a significantly larger volume due to the extent of growth in impervious area relative to historic conditions. Therefore, an expansion in the size of the constructed pond is necessary for the managing of developed stormwater in a safe and effective manner. The proposed bioretention pond is designed to provide about 1,040-sf of bioretention area and is located at the bottom of the detention pond. Provided six inches of depth, approximately 495-cf of the pond’s volume is specifically intended for bioretention purposes – this volume exceeds the required WQCV for Basins B1-B3 (372-cf). Ponding above the initial six inches of pond depth is intended for detention purposes further discussed in the report. Below is a summary of the bioretention pond, recognized as Pond B: Pond Bottom of Pond Elevation Bioretention WSEL Bioretention Volume Required (cf) Bioretention Volume Provided (cf) Pond B 5022.50 5023.00 372 495 Low Impact Development (LID) In December of 2015, Fort Collins City Council adopted the revised Low Impact Development (LID) policy and criteria which requires developments within City limits to meet certain enhanced stormwater treatment requirements in addition to more standard treatment techniques. The proposed development will be required to meet the newly adopted LID criteria which requires the following: -Treat no less than 75% of any newly added impervious area using one or a combination of LID techniques. -Treat no less than 50% of any newly added impervious area using one or a combination of LID techniques when at least 25% of any newly added pavement is provided with permeable pavement. The following measures are implemented with this proposed development: I.Underground Water Quality Basins A1-A3 and C1-C2, combined for 7,406-sf of proposed impervious area, are designed to be routed through an underground water quality system located in the southeastern portion of the site. The proposed impervious area F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 7 U19031_Drainage Report.docx treated through underground water quality includes existing and proposed roof areas. The underground water quality system is designed with an overall capacity of 248-cf which exceeds the minimum design requirements for the area. Refer to Appendix B for additional information. II.Bioretention Basins B1-B3, with 13,979-sf of proposed impervious area, are designed to be conveyed to a Pond B, a proposed bioretention facility. The proposed impervious area treated through bioretention includes existing roof areas. Approximately 1,040-sf of the pond with six inches of depth is designed specifically for water quality. Without the use of permeable pavement, the site is required to treat no less than 75% of added impervious area. Provided the LID measures noted above, approximately 92% of the site is treated in its improved condition. Refer to Appendix B for calculations Detention I.Pond A The design of Pond A is intended for underground water quality purposes; underground detention is not considered with the site improvements. In the 100-year event, runoff conveyed to the underground water pond is designed to bypass the facility and be released at the improved site’s 100-year flows (0.52-cfs). II.Pond B As mentioned in the above section regarding the bioretention pond, ponding depth above the six inches of depth designed for bioretention is reserved for detention purposes. Due to site and grading constraints, the 100-yr event design capacity includes the volume typically utilized for water quality purposes. The required detention volume for Pond B is a function of both the cumulative impact of impervious areas associated with the pond, and the overall release rate to West Prospect Road. The designed volume of the detention is 6,788cf – this volume exceeds that of the required volume for drainage basins related to Pond B (Basins B1-B3 in addition to a 0.49-ac basin conveyed to the Pond from “The Slab” property per the Northern Engineering Report). Runoff in an event that exceeds the 100- yr storm is designed to drain to West Prospect Road via a reconstructed emergency overflow weir similar to that of what was designed and constructed with “The Slab” property’s detention pond. Below is a summary of the detention feature related to Pond B: Pond Bottom of Pond Detention WSEL Top of Pond Elevation Detention Volume Required (cfs) Detention Volume Provided (cf) 100-yr Release Rate (cfs)* Pond B 5022.50 5026.00 5026.60 6,428 6,788 0.85 * 0.85-cfs includes 0.30-cfs of treated runoff from the Slab Property, not included in the cumulative “on-site” release to West Prospect Road F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 8 U19031_Drainage Report.docx III.Pond C A proposed detention system is associated with Basins C1 and C2. This system is designed to release captured runoff within at a rate of 0.28-cfs in the 100-yr event. This release rate is controlled by its relationship with the site’s overall release rate to West Prospect Road (see the following page). Smaller storm events (i.e. water quality events) are designed to pass through the pond without any significant storage in the pond. To reduce the risk of stormwater infiltrating from the pond during larger storm events and into the adjacent basement of Building 3 and/or neighboring properties, the pond will be lined with a minimum of a 30-mil PVC liner outside of the wall limits (Refer to the Construction Plans for a pond wall detail). Additionally, to further protect Building 3, a foundation drain with a sump pump located in the basement of the building will be provided. For emergency situations, the pond is designed to spill stormwater through the emergency overflow structure which is located at the southeast corner of the pond wall. Water discharged from the emergency overflow will be directed via an onsite drainage swale from the overflow location to the eastern property line south of Building 3 and south of the existing residence east of the site. Once at the property line, water will be conveyed along the property line to West Prospect Road. Below is a summary of Pond C utilizing the FAA method: Pond Detention Volume Required (cf) Detention Volume Provided (cf) 100-yr Release Rate (cfs) Pond C 788 1,080 0.28 Drainage Summary A basin summary table is included below: Existing/Historic Basins Basin Area %I C2 C100 Q2 Q100 (acre) (cfs) (cfs) EX1 0.64 15.9% 0.35 0.44 0.50 2.29 EX2 0.55 11.6% 0.32 0.40 0.38 1.64 Totals 0.88 3.93 Proposed Basins Basin Area %I C2 C100 Q2 Q100 (acre) (cfs) (cfs) A1 0.02 90.0% 0.95 1.00 0.05 0.19 A2 0.03 34.7% 0.51 0.64 0.05 0.20 A3 0.01 90.0% 0.95 1.00 0.03 0.12 B1 0.19 16.7% 0.37 0.46 0.17 0.76 B2 0.25 68.3% 0.76 0.95 0.55 2.40 B3 0.13 90.0% 0.95 1.00 0.35 1.27 C1 0.05 25.6% 0.44 0.55 0.06 0.26 C2 0.13 90.0% 0.95 1.00 0.36 1.31 D1 0.13 25.2% 0.42 0.52 0.14 0.66 D2 0.06 2.0% 0.25 0.31 0.04 0.17 E1 0.09 17.6% 0.37 0.47 0.09 0.41 S1 0.04 48.9% 0.62 0.78 0.07 0.31 ON1 0.06 42.4% 0.57 0.71 0.10 0.44 Totals 2.06 8.52 F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 9 U19031_Drainage Report.docx Refer to Appendix D for a Historic Drainage Exhibit that provides a visual representation of Historic Basins EX1 and EX2. In its improved condition, the total release of on-site runoff to West Prospect Road is designed not to exceed the historic 100-yr condition (e.g. Basin EX1). Similarly, on-site runoff that drains off-site to the north is improved in the 100-yr event. Below are summary tables of the on-site runoff release in the 100-yr event: Standard Operating Procedures (SOPs) In order for physical stormwater Best Management Practices (BMPs) to be effective, proper maintenance is essential. Maintenance includes both routinely scheduled activities, as well as non-routine repairs that may be required after large storms, or as a result of other unforeseen problems. Standard Operating Procedures should clearly identify BMP maintenance responsibility. BMP maintenance is typically the responsibility of the entity owning the BMP. Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is allocated for maintenance is critical to the long-term success of BMPs. Maintenance responsibility may be assigned either publicly or privately. For this project, the privately owned BMPs including grass swales, underground water quality and detention, and the bioretention pond, are to be maintained by the property owner. Storm Sewers There are multiple storm sewer networks proposed with the site improvements. Related to conveyance of runoff to the bioretention pond, multiple roof drain systems interconnected with an outfall to the bioretention pond. Other roof drains, storm drains, and underground water quality features are interconnected with an outfall to West Prospect Road. All storm sewers will be private and are sized to accommodate the flows from the 100-year storm event. Hydraulic computations of these systems will be provided within Appendix B. Inlets There are multiple inlets proposed with the site improvements, including nyloplast drain basins and a Type R inlet. The Type R Inlet is designed on-grade to capture runoff developed within Basin A1. On-site drain basins are designed in a sump condition and are designed to convey runoff produced within smaller interior basins to the underground detention system. All inlets on the site are sized to provide adequate capacity and convey the 100-year storm event. Hydraulic computations of these systems will be provided within Appendix B. 100-yr Event: On-site release to West Prospect Road Basin/Pond Designation Release Rate (cfs) Basin EX1 2.29 *Slab Property 0.30 Existing Release 2.59 Basin D1 0.66 Basin D2 0.17 Pond A 0.52 Pond B 0.85 Pond C 0.28 Proposed Release 2.48 * Runoff drained to Pond B from “The Slab” property per the Northern Engineering report is included in the Pond B release; however, this flowrate (0.30-cfs) is not included in “on-site” release calculations. 100-yr Event: On-site release to North Basin/Pond Designation Release Rate (cfs) Basin EX2 1.64 Existing Release 1.64 Basin E1 0.41 Basin ON1 0.44 Proposed Release 0.85 F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 10 U19031_Drainage Report.docx V.EROSION CONTROL A separate Erosion Control Report / Storm Water Management Plan (SWMP) will be prepared for the site in accordance with the Stormwater Discharge Permit for Colorado Department of Public Health and Environment as the site will disturb an area greater than 1-acre. The Erosion Control Report is provided with the Final Compliance phase of the project and includes more detailed information on the sediment and erosion control items for this project. It is intended that the proposed improvements will comply with Erosion Control Criteria per the FCSCM, and all Erosion Control Materials are provided with the Final Drainage Report. At a minimum, the following temporary BMP’s will be installed and maintained to control on-site erosion and prevent sediment from traveling off-site during construction: Silt Fence – a woven synthetic fabric that filters runoff. The silt fence is a temporary barrier that is placed at the base of a disturbed area. Vehicle Tracking Control – a stabilized stone pad located at points of ingress and egress on a construction site. The stone pad is designed to reduce the amount of mud transported onto public roads by construction traffic. Riprap – Riprap will be used downstream of all storm sewer outfalls to control erosion of the receiving channels. Inlet Protection – acts as a sediment filter. It is a temporary BMP and requires proper installation and maintenance to ensure their performance. Straw Wattles – wattles act as a sediment filter in swales around inlets. They are a temporary BMP and require proper installation and maintenance to ensure their performance. Slope Protection – Slopes should be terraced using a “tracked” vehicle, run perpendicular to slope to inhibit rill/gulley erosion. The contractor shall store all construction materials and equipment and shall provide maintenance and fueling of equipment in confined areas on-site from which runoff will be contained and filtered. Temporary Best Management Practices (BMP’s) will be inspected by the contractor at a minimum of once every two weeks and after each significant storm event. VI.CONCLUSIONS A.COMPLIANCE WITH STANDARDS Storm drainage calculations have followed the guidelines provided by the Urban Storm Drainage Criteria Manuals Volumes 1, 2 and 3 and the City of Fort Collins Stormwater Criteria Manual. B.DRAINAGE CONCEPT The drainage system has been designed to convey the runoff to the designated design points and the existing public infrastructure in an effective, safe manner. No negative impacts are anticipated to the City of Fort Collins Master Drainage Plan or to downstream properties or infrastructure due to the proposed improvements. C.STORMWATER QUALITY Multiple long-term stormwater quality measures have been selected for the site that will provide treatment of stormwater prior it to being discharged from the site. For this site this includes grass swales, a bioretention pond, and underground water quality. F INAL D RAINAGE R EPORT A PEX -H AVEN A PARTMENTS F ORT C OLLINS ,CO 11 U19031_Drainage Report.docx VII.REFERENCES 1.City of Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, November 2017. 2.Urban Storm Drainage Criteria Manual Volume 1 and 2, Urban Drainage and Flood Control District, Denver, Colorado, June 2001, Revised April 2008. 3.Final Drainage Report for The Slab, Northern Engineering, Fort Collins, Colorado, September 2016. 4.Final Drainage Report for Observatory Park, DMW Civil Engineers, Fort Collins, Colorado, August 2007. 5.Natural Resources Conservation Service Web Soil Survey at: websoilsurvey.nrcs.usda.gov/app 6.Preliminary Flood Insurance Rate Map, FEMA, Panel 2079E, https://hazards.fema.gov/femaportal/ 7.Stormwater Discharges Associated with Construction Activity, Stormwater Management Plan Preparation Guides, State of Colorado, www.colorado.com A PPENDIX A H YDROLOGY C ALCULATIONS RUNOFF COEFFICIENTS AND % IMPERVIOUS Apex-Haven Apartments, Fort Collins, CO Basin Design Pt.Composite NRCS Soil Total Total Roof (1)Asphalt Concrete(1)Gravel(1)Lawns(1)Imperviousness Type C2 C100 %I = 90%%I = 100%%I = 90%%I =40%%I=2%(%I) acres sf sf sf sf sf sf EX1 EX1 0.64 27,985 2,310 760 3,127 21,788 15.9%0.35 0.44 EX2 EX2 0.55 24,067 1,233 262 2,602 19,970 11.6%0.32 0.40 ----- 1.19 52,052 3,543 -1,022 5,729 41,758 13.9%0.34 0.42 Basin Design Pt.Composite NRCS Soil Total Total Roof (1)Asphalt Concrete(1)Permeable Pavement Lawns(1)Imperviousness Type C2 C100 acres sf %I = 90%%I = 100%%I = 90%%I =40%%I=2%(%I) sf sf sf sf sf A1 A1 0.02 849 849 --90.0%0.95 1.00 A2 A2 0.03 1,393 518 -875 34.7%0.51 0.64 A3 A3 0.01 525 525 ---90.0%0.95 1.00 B1 B1 0.19 8,260 745 631 -6,884 16.7%0.37 0.46 B2 B2 0.25 11,107 982 2,693 4,385 -3,047 68.3%0.76 0.95 B3 B3 0.13 5,576 5,576 ---90.0%0.95 1.00 C1 C1 0.05 2,076 460 96 -1,520 25.6%0.44 0.55 C2 C2 0.13 5,728 5,728 ---90.0%0.95 1.00 D1 D1 0.13 5,495 1,060 270 -4,165 25.2%0.42 0.52 D2 D2 0.06 2,735 --2,735 2.0%0.25 0.31 E1 E1 0.09 3,840 682 -3,158 17.6%0.37 0.47 S1 S1 0.04 1,760 937 -823 48.9%0.62 0.78 ON1 ON1 0.06 2,708 1,161 188 1,359 42.4%0.57 0.71 ---- 1.19 52,052 14,016 3,753 9,529 188 24,566 49.0%0.62 0.77 Notes: (1) Recommended % Imperviousness Values per USDCM Volume 1, Table 6-3. (2) Runoff C is based on %I and NRCS soil group per UDFCD Volume 1, Table 6-4. Proposed Total Composite Runoff Coefficients (2)Areas Existing Basins Proposed Basins Existing Total Areas Composite Runoff Coefficients (2) Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm 2-YEAR TIME OF CONCENTRATION Apex-Haven Apartments, Fort Collins, CO Basin Design Pt.Area C(1)Length Slope ti (2)Length Slope Cv Velocity (3)tt (4)Check tc?Total Length tc (5) acres ft %min ft %fps min min Urban?ft min min EX1 EX1 0.64 0.35 130 4.0%9.7 95 1.6%20 2.5 0.6 10.3 Yes 225 11 10.3 EX2 EX2 0.55 0.32 115 3.3%10.2 145 0.5%15 1.1 2.3 12.5 Yes 260 11 11.4 Basin Design Pt.Area C(1)Length Slope ti (2)Length Slope Cv Velocity (3)tt (4)Check tc?Total Length tc (5) acres ft %min ft %fps min min Urban?ft min min A1 A1 0.02 0.95 60 4.0%1.3 10 5.5%20 4.7 0.0 1.4 Yes 70 10 5.0 A2 A2 0.03 0.51 25 5.0%3.1 105 4.0%15 3.0 0.6 3.7 Yes 130 11 5.0 A3 A3 0.01 0.95 45 6.0%1.0 20 2.0%20 2.8 0.1 1.1 Yes 65 10 5.0 B1 B1 0.19 0.37 75 5.0%6.7 55 0.5%15 1.1 0.9 7.6 Yes 130 11 7.6 B2 B2 0.25 0.76 40 3.5%2.6 125 0.5%20 1.4 1.5 4.1 Yes 165 11 5.0 B3 B3 0.13 0.95 30 2.0%1.2 100 0.5%20 1.4 1.2 2.4 Yes 130 11 5.0 C1 C1 0.05 0.44 45 6.0%4.4 55 0.5%15 1.1 0.9 5.3 Yes 100 11 5.3 C2 C2 0.13 0.95 30 2.0%1.2 100 0.5%20 1.4 1.2 2.4 Yes 130 11 5.0 D1 D1 0.13 0.42 25 5.0%3.6 135 0.5%15 1.1 2.1 5.7 Yes 160 11 5.7 D2 D2 0.06 0.25 50 3.5%7.2 35 2.0%15 2.1 0.3 7.5 Yes 85 10 7.5 E1 E1 0.09 0.37 15 5.5%2.9 130 2.2%15 2.2 1.0 3.9 Yes 145 11 5.0 S1 S1 0.04 0.62 30 2.5%3.5 100 4.7%20 4.3 0.4 3.9 Yes 130 11 5.0 ON1 ON1 0.06 0.57 20 5.0%2.5 60 0.5%20 1.4 0.7 3.2 Yes 80 10 5.0 Notes: (1) C=Cx*Cf (2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (300' max) (3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4 (4)tt=L/(V*60 sec/min) (5)tc check (for urban or developed areas only) = total length/180 + 10 (6)min tc = 5 min Existing Basins Travel/Channelized Time of Flow (tt) ti+tt tc Check for Urbanized Basins Final tc (6) Proposed Basins Travel/Channelized Time of Flow (tt) ti+tt tc Check for Urbanized Basins Final tc (6) Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm 100-YEAR TIME OF CONCENTRATION Apex-Haven Apartments, Fort Collins, CO Basin Design Pt.Area C(1)Length Slope ti (2)Length Slope Cv Velocity (3)tt (4)Check tc?Total Length tc (5) acres ft %min ft %fps min min Urban?ft min min EX1 EX1 0.64 0.44 130 4.0%8.6 95 1.6%20 2.5 0.6 9.2 Yes 225 11 9.2 EX2 EX2 0.55 0.40 115 3.3%9.1 145 0.5%15 1.1 2.3 11.4 Yes 260 11 11.4 Basin Design Pt.Area C(1)Length Slope ti (2)Length Slope Cv Velocity (3)tt (4)Check tc?Total Length tc (5) acres ft %min ft %fps min min Urban?ft min min A1 A1 0.02 1.00 60 4.0%0.9 10 5.5%20 4.7 0.0 0.9 Yes 70 10 5.0 A2 A2 0.03 0.64 25 5.0%2.5 105 4.0%15 3.0 0.6 3.0 Yes 130 11 5.0 A3 A3 0.01 1.00 45 6.0%0.7 20 2.0%20 2.8 0.1 0.8 Yes 65 10 5.0 B1 B1 0.19 0.46 75 5.0%5.9 55 0.5%15 1.1 0.9 6.8 Yes 130 11 6.8 B2 B2 0.25 0.95 40 3.5%1.2 125 0.5%20 1.4 1.5 2.6 Yes 165 11 5.0 B3 B3 0.13 1.00 30 2.0%0.8 100 0.5%20 1.4 1.2 2.0 Yes 130 11 5.0 C1 C1 0.05 0.55 45 6.0%3.7 55 0.5%15 1.1 0.9 4.6 Yes 100 11 5.0 C2 C2 0.13 1.00 30 2.0%0.8 100 0.5%20 1.4 1.2 2.0 Yes 130 11 5.0 D1 D1 0.13 0.52 25 5.0%3.1 135 0.5%15 1.1 2.1 5.2 Yes 160 11 5.2 D2 D2 0.06 0.31 50 3.5%6.6 35 2.0%15 2.1 0.3 6.9 Yes 85 10 6.9 E1 E1 0.09 0.47 15 5.5%2.5 130 2.2%15 2.2 1.0 3.5 Yes 145 11 5.0 S1 S1 0.04 0.78 30 2.5%2.4 100 4.7%20 4.3 0.4 2.7 Yes 130 11 5.0 ON1 ON1 0.06 0.71 20 5.0%1.9 60 0.5%20 1.4 0.7 2.6 Yes 80 10 5.0 Notes: (1) C=Cx*Cf (2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (300' max) (3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4 (4)tt=L/(V*60 sec/min) (5)tc check (for urban or developed areas only) = total length/180 + 10 (6)min tc = 5 min Existing Basins Travel/Channelized Time of Flow (tt) ti+tt tc Check for Urbanized Basins Final tc (6) Proposed Basins Travel/Channelized Time of Flow (tt) ti+tt tc Check for Urbanized Basins Final tc (6) Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm RATIONAL METHOD PEAK RUNOFF Apex-Haven Apartments, Fort Collins, CO Basin Design Pt.Area 2-Year 100-Year acre tc tc C2 C100 I2 I100 Q2 Q100 min min in/hr in/hr cfs cfs EX1 EX1 0.64 10 9 0.35 0.44 2.21 8.03 0.50 2.29 EX2 EX2 0.55 11 11 0.32 0.40 2.13 7.42 0.38 1.64 0.88 3.93 Basin Design Pt.Area 2-Year 100-Year acre tc tc C2 C100 I2 I100 Q2 Q100 min min in/hr in/hr cfs cfs A1 A1 0.02 5 5 0.95 1.00 2.85 9.95 0.05 0.19 A2 A2 0.03 5 5 0.51 0.64 2.85 9.95 0.05 0.20 A3 A3 0.01 5 5 0.95 1.00 2.85 9.95 0.03 0.12 B1 B1 0.19 8 7 0.37 0.46 2.40 8.80 0.17 0.76 B2 B2 0.25 5 5 0.76 0.95 2.85 9.95 0.55 2.40 B3 B3 0.13 5 5 0.95 1.00 2.85 9.95 0.35 1.27 C1 C1 0.05 5 5 0.44 0.55 2.85 9.95 0.06 0.26 C2 C2 0.13 5 5 0.95 1.00 2.85 9.95 0.36 1.31 D1 D1 0.13 6 5 0.42 0.52 2.67 9.95 0.14 0.66 D2 D2 0.06 7 7 0.25 0.31 2.52 8.80 0.04 0.17 E1 E1 0.09 5 5 0.37 0.47 2.85 9.95 0.09 0.41 S1 S1 0.04 5 5 0.62 0.78 2.85 9.95 0.07 0.31 ON1 ON1 0.06 5 5 0.57 0.71 2.85 9.95 0.10 0.44 2.06 8.52 Existing Basins Totals Totals Peak Discharge Proposed Basins Runoff Coefficients Rainfall Intensity Peak Discharge Rainfall IntensityRunoff Coefficients Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm A PPENDIX B H YDRAULIC C ALCULATIONS LOW IMPACT DEVELOPMENT SUMMARY Apex-Haven Apartments, Fort Collins, CO Basin Proposed Impervious Area LID Treatment Area Treated % of Site Treated (sf)(acres)(sf)(%) A1 764 Underground Water Quality 764 3% A2 484 Underground Water Quality 484 2% A3 473 Underground Water Quality 473 2% B1 1,376 Bioretention 1,376 5% B2 7,584 Bioretention 7,584 30% B3 5,018 Bioretention 5,018 20% C1 531 Underground Water Quality 531 2% C2 5,155 Underground Water Quality 5,155 20% D1 1,386 None -0% D2 55 None -0% E1 677 None -0% S1 860 Bioretention 860 3% ON1 1,147 Offsite Infiltration System 1,147 4% Total Site 25,510 23,392 92% Low Impact Development (LID) Treated Areas Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm WATER QUALITY Apex-Haven Apartments, Fort Collins, CO Required Onsite Water Quality Capture Volume Basin Area Area Imperviousness Watershed WQCV (sf)(acres)(%)(inches)(cf) A-Total (1)2,767 0.064 62%0.19 45 B-Total (2)24,943 0.573 56%0.18 372 C-Total (1)7,804 0.179 73%0.23 150 D-Total 8,230 0.189 18%0.10 86 E1 3,840 0.088 18%0.11 41 Less Basins D and E that are free released from site 127 Total WQ Required 567 (1) Water quality provided by underground detention and based on 12-hour storage (2) Water quality provided by bioretention and based on 12-hour storage (3) Basins D and E free release from the site Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND VOLUME (FAA Method) Apex-Haven Apartments, Fort Collins, CO POND ID:Pond A (Underground Water Quality) WQ Basin Characateristics Area =10,571 square feet Area =0.24 acres C 2 = 0.79 Q in = 0.55 cfs WQ Release Rate Determined from Number of Chambers and Chamber Release Rate Q OUT = 0.13 cfs Unit Flow =0.52 cfs/acre T C =0.0 minutes Notes: 1. Release rate out of pond based on number of chambers multiplied by release rate per chamber. 2. Rainfall intensities approximated as one-half the 2-yr peak runoff rate. 3. C2 utilized for water quality event detention calculation. 4. Pond is designed to provide WQ for all "A" and "C" Basins. Detention Volume Calculations Rainfall Rainfall Inflow Rate Inflow Volume Adjustment Factor Average Outflow Volume Required Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 1.425 0.3 82 0.50 0.06 19 63 10 1.105 0.2 127 0.50 0.06 38 90 15 0.935 0.2 162 0.50 0.06 57 105 20 0.805 0.2 186 0.50 0.06 75 110 25 0.715 0.1 206 0.50 0.06 94 112 30 0.650 0.1 225 0.50 0.06 113 111 35 0.585 0.1 236 0.50 0.06 132 104 40 0.535 0.1 247 0.50 0.06 151 96 45 0.495 0.1 257 0.50 0.06 170 87 50 0.460 0.1 265 0.50 0.06 189 76 55 0.435 0.1 276 0.50 0.06 208 68 60 0.410 0.1 283 0.50 0.06 226 57 65 0.385 0.1 288 0.50 0.06 245 43 70 0.365 0.1 294 0.50 0.06 264 30 75 0.345 0.1 298 0.50 0.06 283 15 80 0.330 0.1 304 0.50 0.06 302 2 85 0.315 0.1 309 0.50 0.06 321 -12 90 0.305 0.1 316 0.50 0.06 340 -23 95 0.290 0.1 317 0.50 0.06 359 -41 100 0.280 0.1 323 0.50 0.06 377 -55 105 0.270 0.1 327 0.50 0.06 396 -70 110 0.260 0.0 330 0.50 0.06 415 -86 115 0.255 0.0 338 0.50 0.06 434 -96 120 0.245 0.0 339 0.50 0.06 453 -114 Required Water Quality Volume V 100 = 112 cubic feet V 100 = 0.00 acre-ft Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND VOLUME (FAA Method) Apex-Haven Apartments, Fort Collins, CO POND ID:Pond A (Underground Water Quality) 100 Year Storm Into Detention Facility Area =2,767 square feet Area =0.06 acres C 100 = 0.82 Release Rate Out of Pond Q OUT = 0.52 cfs Unit Flow =8.12 cfs/acre Notes: 1. Release Rate controlled by 100-year historic flow rates from site to Prospect Avenue and includes 0.1 cfs from Pond C1. 2. Area analyzed Includes Basins A1-A3. 3. Pond is designed to provide WQ for all "A" and "C" Basins Detention Volume Calculations Rainfall Rainfall Inflow Rate Inflow Volume Adjustment Factor Average Outflow Volume Required Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 9.95 0.5 155 1.00 0.52 155 0 10 7.72 0.4 241 1.00 0.52 310 -69 15 6.52 0.3 305 1.00 0.52 464 -160 20 5.60 0.3 349 1.00 0.52 619 -270 25 4.98 0.3 388 1.00 0.52 774 -386 30 4.52 0.2 423 1.00 0.52 929 -506 35 4.08 0.2 445 1.00 0.52 1,084 -639 40 3.74 0.2 466 1.00 0.52 1,238 -772 45 3.46 0.2 485 1.00 0.52 1,393 -908 50 3.23 0.2 503 1.00 0.52 1,548 -1,045 55 3.03 0.2 519 1.00 0.52 1,703 -1,183 60 2.86 0.1 535 1.00 0.52 1,858 -1,323 70 2.59 0.1 565 1.00 0.52 2,167 -1,602 80 2.38 0.1 593 1.00 0.52 2,477 -1,883 90 2.21 0.1 620 1.00 0.52 2,786 -2,167 100 2.06 0.1 642 1.00 0.52 3,096 -2,454 110 1.94 0.1 665 1.00 0.52 3,406 -2,741 120 1.84 0.1 688 1.00 0.52 3,715 -3,027 Required Detention Volume V 100 = 0 cubic feet V 100 = 0.00 acre-ft Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND VOLUME (FAA Method) Apex-Haven Apartments, Fort Collins, CO POND ID:Pond B 100 Year Storm Into Detention Facility Area =48,047 square feet Area =1.10 acres C 100 = 0.83 Release Rate Out of Pond Q OUT = 0.85 cfs Unit Flow =0.77 cfs/acre Notes: 1. Release Rate includes 0.3 cfs from the The Slab property per the Northern Report plus 0.63 cfs from onsite, limiting the total site flows entering Prospect to the 100-year historic value. 2. Pond area includes 0.49 acres from the The Slab property per the Northern Report in addition to onsite Basins B1-B3 and S1. Detention Volume Calculations Rainfall Rainfall Inflow Rate Inflow Volume Adjustment Factor Average Outflow Volume Required Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 9.95 9.1 2,744 0.50 0.43 128 2,616 10 7.72 7.1 4,257 1.00 0.85 510 3,747 15 6.52 6.0 5,393 1.00 0.85 765 4,628 20 5.60 5.1 6,177 1.00 0.85 1,020 5,157 25 4.98 4.6 6,866 1.00 0.85 1,275 5,591 30 4.52 4.2 7,478 1.00 0.85 1,530 5,948 35 4.08 3.8 7,875 1.00 0.85 1,785 6,090 40 3.74 3.4 8,250 1.00 0.85 2,040 6,210 45 3.46 3.2 8,587 1.00 0.85 2,295 6,292 50 3.23 3.0 8,906 1.00 0.85 2,550 6,356 55 3.03 2.8 9,190 1.00 0.85 2,805 6,385 60 2.86 2.6 9,463 1.00 0.85 3,060 6,403 70 2.59 2.4 9,998 1.00 0.85 3,570 6,428 80 2.38 2.2 10,500 1.00 0.85 4,080 6,420 90 2.21 2.0 10,969 1.00 0.85 4,590 6,379 100 2.06 1.9 11,360 1.00 0.85 5,100 6,260 110 1.94 1.8 11,769 1.00 0.85 5,610 6,159 120 1.84 1.7 12,177 1.00 0.85 6,120 6,057 Required Detention Volume V 100 = 6,428 cubic feet V 100 = 0.15 acre-ft Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND STORAGE AND ORIFICE CALCULATIONS Apex-Haven Apartments, Fort Collins, CO POND ID:Pond B Stage Storage Calculations Elevation Area (sf)Depth (ft) Incremental Volume (cf)Volume total (cf) Volume total (ac- ft) 5,022.50 5.00 0.00 0 0 0.00 5,022.60 709.37 0.10 55 55 0.00 5,022.70 1,178.55 0.10 93 93 0.00 5,022.80 1,254.04 0.10 122 215 0.00 5,022.90 1,326.28 0.10 129 344 0.01 5,023.00 1,725.79 0.10 152 496 0.01 5,023.10 1,789.45 0.10 176 672 0.02 5,023.20 1,835.59 0.10 181 853 0.02 5,023.30 1,852.01 0.10 184 1,038 0.02 5,023.40 1,868.38 0.10 186 1,224 0.03 5,023.50 1,884.74 0.10 188 1,411 0.03 5,023.60 1,901.63 0.10 189 1,601 0.04 5,023.70 1,919.36 0.10 191 1,792 0.04 5,023.80 1,938.23 0.10 193 1,984 0.05 5,023.90 1,957.46 0.10 195 2,179 0.05 5,024.00 1,977.11 0.10 197 2,376 0.05 5,024.10 1,997.24 0.10 199 2,575 0.06 5,024.20 2,017.83 0.10 201 2,775 0.06 5,024.30 2,038.88 0.10 203 2,978 0.07 5,024.40 2,060.28 0.10 205 3,183 0.07 5,024.50 2,082.03 0.10 207 3,390 0.08 5,024.60 2,104.13 0.10 209 3,600 0.08 5,024.70 2,126.69 0.10 212 3,811 0.09 5,024.80 2,149.76 0.10 214 4,025 0.09 5,024.90 2,173.35 0.10 216 4,241 0.10 5,025.00 2,197.49 0.10 219 4,460 0.10 5,025.10 2,222.14 0.10 221 4,681 0.11 5,025.20 2,247.18 0.10 223 4,904 0.11 5,025.30 2,272.67 0.10 226 5,130 0.12 5,025.40 2,298.81 0.10 229 5,359 0.12 5,025.50 2,325.61 0.10 231 5,590 0.13 5,025.60 2,353.08 0.10 234 5,824 0.13 5,025.70 2,381.22 0.10 237 6,061 0.14 5,025.80 2,409.99 0.10 240 6,300 0.14 5,025.90 2,439.51 0.10 242 6,543 0.15 5,026.00 2,469.91 0.10 245 6,788 0.16 Detention Volume Required =6,428 ft3 Orifice Flow Rate, Q = CoAo(2gHo)0.5 cfs 0.15 ac-ft Area of orifice Ao, ft2 = Q Elev81 - Elev80 (VolRequired-Vol80)+Elev80 Co(2gHo)0.5 Vol81 - Vo80 C o = 0.65 Required W.S. Elevation = 5025.85 ft Q = Q out of pond = 0.85 cfs Provided W.S. Elevation = 5026.00 ft gravitational acceleration g = 32.2 ft/sec2 Detention Volume Provided =6,788 ft3 diam = 0.337 ft 0.16 ac-ft Effective head on orifice H o = D-1/2diam =3.33 ft 100-year Depth D = 3.50 ft Area of orifice A o = 0.09 ft2 Top-of-Berm = 5026.50 ft Area of orifice A o = 12.86 in2 Freeboard = 0.50 ft 100-Year Orifice Diameter = 4.05 4 1/16 inches Orifice OpeningDetention Pond Storage & Water Quality 100-Year Detention Volume and Elevations W.S. Elevation, ft = 100-Year Orifice Calculation Date: 4/21/2021 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND VOLUME (FAA Method) Apex-Haven Apartments, Fort Collins, CO POND ID:Pond C 100 Year Storm Into Detention Facility Area =7,804 square feet Area =0.18 acres C 100 = 0.88 Release Rate Out of Pond Q OUT = 0.28 cfs Unit Flow =1.56 cfs/acre Notes: 1. Pond area includes onsite Basins C1 and C2. Detention Volume Calculations Rainfall Rainfall Inflow Rate Inflow Volume Adjustment Factor Average Outflow Volume Required Duration (T)Intensity (I)Qin= ∑C100*Area*I Vi=(Qin*T*60)Factor Outflow Rate Vo=Qav*T *60 Storage Volume m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 9.95 1.6 470 0.50 0.14 42 428 10 7.72 1.2 730 1.00 0.28 168 562 15 6.52 1.0 925 1.00 0.28 252 673 20 5.60 0.9 1,059 1.00 0.28 336 723 25 4.98 0.8 1,177 1.00 0.28 420 757 30 4.52 0.7 1,282 1.00 0.28 504 778 35 4.08 0.6 1,350 1.00 0.28 588 762 40 3.74 0.6 1,414 1.00 0.28 672 742 45 3.46 0.5 1,472 1.00 0.28 756 716 50 3.23 0.5 1,527 1.00 0.28 840 687 55 3.03 0.5 1,575 1.00 0.28 924 651 60 2.86 0.5 1,622 1.00 0.28 1,008 614 70 2.59 0.4 1,714 1.00 0.28 1,176 538 80 2.38 0.4 1,800 1.00 0.28 1,344 456 90 2.21 0.3 1,880 1.00 0.28 1,512 368 100 2.06 0.3 1,947 1.00 0.28 1,680 267 110 1.94 0.3 2,017 1.00 0.28 1,848 169 120 1.84 0.3 2,087 1.00 0.28 2,016 71 Required Detention Volume V 100 = 778 cubic feet V 100 = 0.02 acre-ft Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm DETENTION POND STORAGE AND ORIFICE CALCULATIONS Apex-Haven Apartments, Fort Collins, CO POND ID:Pond C Stage Storage Calculations Elevation Area (sf)Depth (ft) Incremental Volume (cf)Volume total (cf) Volume total (ac- ft) 5,022.70 0.40 0.00 0 0 0.00 5,022.80 51.71 0.10 2 2 0.00 5,022.90 200.32 0.10 12 14 0.00 5,023.00 440.92 0.10 31 45 0.00 5,023.10 507.79 0.10 47 92 0.00 5,023.20 516.15 0.10 51 144 0.00 5,023.30 524.55 0.10 52 196 0.00 5,023.40 533.00 0.10 53 248 0.01 5,023.50 541.50 0.10 54 302 0.01 5,023.60 550.05 0.10 55 357 0.01 5,023.70 558.65 0.10 55 412 0.01 5,023.80 567.32 0.10 56 469 0.01 5,023.90 576.06 0.10 57 526 0.01 5,024.00 584.88 0.10 58 584 0.01 5,024.10 593.76 0.10 59 643 0.01 5,024.20 602.72 0.10 60 702 0.02 5,024.30 611.81 0.10 61 763 0.02 5,024.40 621.04 0.10 62 825 0.02 5,024.50 630.44 0.10 63 887 0.02 5,024.60 639.99 0.10 64 951 0.02 5,024.70 649.71 0.10 64 1,015 0.02 5,024.80 659.59 0.10 65 1,081 0.02 Detention Volume Required =778 ft3 Orifice Flow Rate, Q = CoAo(2gHo)0.5 cfs 0.02 ac-ft Area of orifice Ao, ft2 = Q Elev81 - Elev80 (VolRequired-Vol80)+Elev80 Co(2gHo)0.5 Vol81 - Vo80 C o = 0.65 Required W.S. Elevation = 5024.32 ft Q = Q out of pond = 0.28 cfs Provided W.S. Elevation = 5024.80 ft gravitational acceleration g = 32.2 ft/sec2 Detention Volume Provided =1,081 ft3 diam = 0.220 ft 0.02 ac-ft Effective head on orifice H o = D-1/2diam =1.99 ft 100-year Depth D = 2.10 ft Area of orifice A o = 0.04 ft2 Top-of-Berm = 5024.80 ft Area of orifice A o = 5.48 in2 Freeboard = 0.00 ft 100-Year Orifice Diameter = 2.64 2 5/8 inches Detention Pond Storage & Water Quality Orifice Opening 100-Year Detention Volume and Elevations 100-Year Orifice Calculation W.S. Elevation, ft = Date: 4/21/2021 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm UNDERGROUND DETENTION & WATER QUALITY Apex-Haven Apartments, Fort Collins, CO Pond A - Underground WQ Volume Chamber Total Required Detention/Chamber Chamber Unit Chamber *Installed Min.Min.Min. Req'd Design No. of Provided Provided Total ID Detention/WQ WQ Type Release Ratec Unit Chamber Unit No. of WQ Isolator Row Controli Chambers WQ Isolator Installed Volumea Inflowb Volumed Volume inc.Chambersf Release Volume by Provided Release Row System Aggregatee Rateg FAA Methodh Ratej Volumek Volumel (cf)(cfs)(cfs)(cf)(cf)(ea)(cfs)(cf)(cfs)(cf)(cf) Pond A (WQ/LID)195 0.42 SC-310 0.016 14.70 31.00 7 0.11 112 WQCV 8 0.13 118 248 *Volume assumes minimum aggregate depth below chamber. a. Total required WQCV calculated per 12-hr drain time. b. WQ inflow is approximated as one-half the 2-yr peak runoff rate. c. Release rate per chamber, limited by flow through geotextile with accumulated sediment. d. Volume within chamber only, not accounting for void spaces in surrounding aggregate. The Isolator Row(s) are sized per this unit volume. e. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit. The total system WQCV is sized per this unit volume. f. Number of chambers required to provide full WQCV within total installed system, including aggregate. g. Release rate per chamber times number of chambers. This is used at the 'outlet control' for the FAA calculations. h. Minimum 'chamber-only' volume to ensure dirty water is fully contained within Isolator Row. i. Determines whether the design is controlled by the Isolator Row volume or WQCV. j. Release rate per chamber times number of chambers provided. This is the approximate controlled discharge from the WQ event. k. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume. l. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required 12-hr WQCV. m. Underground facility is designed to provide WQ for all "A" and "C" Basins Date: 12/9/2020 C:\United Civil Dropbox\Projects\U19031 - Haven Apartments\Reports\Drainage\Calculations\U19031-Drain Calcs-Revised Site.xlsm 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10Capacity (cfs)Head (ft) Nyloplast 8" Dome Grate Inlet Capacity Chart Project: Inlet ID: Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb TBACK =0.5 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.020 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.013 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =24.0 ft Gutter Width W =1.00 ft Street Transverse Slope SX =0.020 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.055 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =10.0 10.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Allow Flow Depth at Street Crown (leave blank for no)check = yes MINOR STORM Allowable Capacity is based on Spread Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Spread Criterion Qallow =7.4 7.4 cfs Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Version 4.06 Released August 2018 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Apex-Haven Apartments Inlet 1-6 UD-Inlet_v4.06.xlsm, Inlet 1-6 4/21/2021, 8:28 PM Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a')aLOCAL =3.0 3.0 inches Total Number of Units in the Inlet (Grate or Curb Opening)No =1 1 Length of a Single Unit Inlet (Grate or Curb Opening)Lo =5.00 5.00 ft Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =N/A N/A ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf-G =N/A N/A Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf-C =0.10 0.10 Street Hydraulics: OK - Q < Allowable Street Capacity'MINOR MAJOR Total Inlet Interception Capacity Q =0.0 0.2 cfs Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =0.0 0.0 cfs Capture Percentage = Qa/Qo =C% =100 100 % CDOT Type R Curb Opening INLET ON A CONTINUOUS GRADE Version 4.06 Released August 2018 CDOT Type R Curb Opening UD-Inlet_v4.06.xlsm, Inlet 1-6 4/21/2021, 8:28 PM Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Thursday, Apr 22 2021 Curb Channel A: 100 yr Event Rectangular Bottom Width (ft)= 2.00 Total Depth (ft)= 0.50 Invert Elev (ft)= 1.00 Slope (%)= 0.50 N-Value = 0.013 Calculations Compute by:Known Q Known Q (cfs)= 1.52 Highlighted Depth (ft)= 0.27 Q (cfs)= 1.520 Area (sqft)= 0.54 Velocity (ft/s)= 2.81 Wetted Perim (ft)= 2.54 Crit Depth, Yc (ft)= 0.27 Top Width (ft)= 2.00 EGL (ft)= 0.39 0 .5 1 1.5 2 2.5 3 Elev (ft)Depth (ft)Section 0.75 -0.25 1.00 0.00 1.25 0.25 1.50 0.50 1.75 0.75 2.00 1.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Thursday, Apr 22 2021 Curb Channel B: 100 yr Event Rectangular Bottom Width (ft)= 2.00 Total Depth (ft)= 0.50 Invert Elev (ft)= 1.00 Slope (%)= 1.00 N-Value = 0.013 Calculations Compute by:Known Q Known Q (cfs)= 2.40 Highlighted Depth (ft)= 0.29 Q (cfs)= 2.400 Area (sqft)= 0.58 Velocity (ft/s)= 4.14 Wetted Perim (ft)= 2.58 Crit Depth, Yc (ft)= 0.36 Top Width (ft)= 2.00 EGL (ft)= 0.56 0 .5 1 1.5 2 2.5 3 Elev (ft)Depth (ft)Section 0.75 -0.25 1.00 0.00 1.25 0.25 1.50 0.50 1.75 0.75 2.00 1.00 Reach (ft) Weir Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Thursday, Apr 22 2021 Pond B Weir: 100 yr Event Rectangular Weir Crest = Sharp Bottom Length (ft)= 39.33 Total Depth (ft)= 0.60 Calculations Weir Coeff. Cw = 3.33 Compute by:Known Q Known Q (cfs)= 4.73 Highlighted Depth (ft)= 0.11 Q (cfs)= 4.730 Area (sqft)= 4.29 Velocity (ft/s)= 1.10 Top Width (ft)= 39.33 0 5 10 15 20 25 30 35 40 45 50 Depth (ft)Depth (ft)Pond B Weir: 100 yr Event -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft)Weir W.S. Weir Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, Apr 27 2021 Pond C Weir: 100 yr Event Rectangular Weir Crest = Broad Bottom Length (ft)= 9.00 Total Depth (ft)= 0.50 Calculations Weir Coeff. Cw = 2.60 Compute by:Known Q Known Q (cfs)= 1.57 Highlighted Depth (ft)= 0.16 Q (cfs)= 1.570 Area (sqft)= 1.48 Velocity (ft/s)= 1.06 Top Width (ft)= 9.00 0 1 2 3 4 5 6 7 8 9 10 11 Depth (ft)Depth (ft)Pond C Weir: 100 yr Event -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft)Weir W.S. A PPENDIX C R EFERENCED M ATERIALS +=8;6@-=0;! $5=0;7-=3?0!&86953-7.0",-;3-7.0!$9953.-=387 4OY^!TL!7TWY!4TQQOSX!DGYKW!BYOQOYOKX!6SMOSKKWOSM +0.=387!$#!’723700;")@70;!(718;6-=387 6SMOSKKW!<GRK############################################>NTSK########################### @YWKKY!!3JJWKXX############################################################################# 4OY^##########################################@YGYK########################EOUF############ =\SKW!<GRK##############################################>NTSK########################### @YWKKY!!3JJWKXX############################################################################# 4OY^##########################################@YGYK########################EOUF############ +0.=387!&#!$5=0;7-=3?0!&86953-7.0",-;3-7.0!(718;6-=387 +0.=387!%#!*;898<0/!*;840.=!(718;6-=387 9KMGQ!JKXIWOUYOTS!GSJ’TW!GJJWKXX!TL!UWTUKWY^F#################FFFFFFF########################### >WTPKIY!<GRK############################################FFFFFFF########################### >WTPKIY’3UUQOIGYOTS!<ZRHKW!LWTR!5K[KQTURKSY!?K[OK\!"O&K&!75>)*+,-.#FFFFFFFFFFFFFFFFFFFFFFFFFF 5KXIWOUYOTS!TL!>WTPKIY#####################################FFFFFFF########################### FFFFFFFFFFFF############################################FFFFFFF########################### 6]OXYOSM!BXK!"/41/6!;91#1!!!!!WKXOJKSYOGQ!!!!!STS%WKXOJKSYOGQ!!!!!RO]KJ%ZXK!!!!![GIGSY!MWTZSJ >WTUTXKJ!BXK!"/41/6!;91#1!!!!!WKXOJKSYOGQ!!!!!STS%WKXOJKSYOGQ!!!!!RO]KJ%ZXK!!!!!TYNKWFFFFFFFFFFFFFFFFFFFF 8L!STS%WKXOJKSYOGQ!TW!RO]KJ!ZXK$!JKXIWOHK!OS!JKYGOQ#############FFFFFFF########################### FFFFFFFFFFFF############################################FFFFFFF########################### FFFFFFFFFFFF############################################FFFFFFF########################### @YGYK!YNK!WKVZOWKRKSY!LWTR!\NOIN!GQYKWSGYO[K!ITRUQOGSIK’[GWOGSIK!OX!XTZMNY&!">QKGXK!OSIQZJK! GUUQOIGHQK!5WGOSGMK!4WOYKWOG!;GSZGQ![TQZRK$!INGUYKW!GSJ!XKIYOTS&#! DNGY!NGWJXNOU!UWK[KSYX!YNOX!XOYK!LWTR!RKKYOSM!YNK!WKVZOWKRKSY2 DNGY!GQYKWSGYO[K!OX!UWTUTXKJ!LTW!YNK!XOYK2 ’??./4!>1<.=.?1!>411?!52!91/1>>.=B ’??./4!>1<.=.?1!>411?!52!91/1>>.=B Kevin Brazelton 970-530-4044 1501 Academy Court Suite 203 Fort Collins CO 80525 Maxiimo Development Group (Attn: Christian Bachelet)970-566-2948 706 South College Avenue, Suite 207 Fort Collins CO 80524 Haven Apartments Lot 2 of the Slab Property Subdivision The restoration of two existing on-site single-family residences and the construction of a new 14,000 sf footprint apartment building. Chapter 6 (Detention), Section 1.1 Master Plan Requirements, Typical Release Rates See attached. See attached. Wxsvq{exiv#Zevmergi#Viuyiwx# Lezir#Etevxqirxw# Jsvx#Gsppmrw/#GS# [lex#levhwlmt#tvizirxw#xlmw#wmxi#jvsq#qiixmrk#xli#viuymviqirxC# The Old Town Master Drainage Basin requires that detention release rates be limited to the 2-year historic event. The east residence has a historical designation which limits drainage solutions adjacent to the building (i.e. a standard open detention pond adjacent to the building will not be allowed). Due to the lack of public storm sewer adjacent to the site and that the location of the existing detention pond is uphill from the eastern residence, Basins C1 and C2 of the site cannot be detained and the release from these basins exceed the 2-year historic event. Therefore, limiting the site release rate to the 2-year historic event will not be feasible. [lex#epxivrexmzi#mw#tvstswih#jsv#xli#wmxiC# The development is proposing to limit the release rate from the site to the 100-year historic condition. To do so, the development will expand the existing detention pond and over-detain flows intercepted by the pond to the extent feasible. Additionally, the development will provide a small underground detention pond south of the existing eastern residence to provide water quality and detention for as much site area as feasible. Together, the site will hold the total release to Prospect Avenue to the 100-year historic event. United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Larimer County Area, Colorado Haven Apartments Natural Resources Conservation Service September 4, 2019 9 Custom Soil Resource Report Soil Map 449068044907004490720449074044907604490780449080044908204490840449068044907004490720449074044907604490780449080044908204490840492340 492360 492380 492400 492420 492440 492460 492340 492360 492380 492400 492420 492440 492460 40° 34' 6'' N 105° 5' 25'' W40° 34' 6'' N105° 5' 20'' W40° 34' 0'' N 105° 5' 25'' W40° 34' 0'' N 105° 5' 20'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 40 80 160 240 Feet 0 10 20 40 60 Meters Map Scale: 1:865 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 Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features 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 of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 13, Sep 10, 2018 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. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 3 Altvan-Satanta loams, 0 to 3 percent slopes 3.1 100.0% Totals for Area of Interest 3.1 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. Custom Soil Resource Report 11 An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 Larimer County Area, Colorado 3—Altvan-Satanta loams, 0 to 3 percent slopes Map Unit Setting National map unit symbol: jpw2 Elevation: 5,200 to 6,200 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Altvan and similar soils: 45 percent Satanta and similar soils: 30 percent Minor components: 25 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Altvan Setting Landform: Benches, terraces Landform position (three-dimensional): Side slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Mixed alluvium Typical profile H1 - 0 to 10 inches: loam H2 - 10 to 18 inches: clay loam, loam, sandy clay loam H2 - 10 to 18 inches: loam, fine sandy loam, silt loam H2 - 10 to 18 inches: gravelly sand, gravelly coarse sand, coarse sand H3 - 18 to 30 inches: H3 - 18 to 30 inches: H3 - 18 to 30 inches: H4 - 30 to 60 inches: H4 - 30 to 60 inches: H4 - 30 to 60 inches: Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Very high (about 13.2 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Custom Soil Resource Report 13 Hydrologic Soil Group: B Hydric soil rating: No Description of Satanta Setting Landform: Terraces, structural benches Landform position (three-dimensional): Side slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Mixed alluvium and/or eolian deposits Typical profile H1 - 0 to 9 inches: loam H2 - 9 to 18 inches: loam, clay loam, sandy clay loam H2 - 9 to 18 inches: loam, clay loam, fine sandy loam H2 - 9 to 18 inches: H3 - 18 to 60 inches: H3 - 18 to 60 inches: H3 - 18 to 60 inches: Properties and qualities Slope: 0 to 1 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Very high (about 27.4 inches) Interpretive groups Land capability classification (irrigated): 1 Land capability classification (nonirrigated): 3c Hydrologic Soil Group: B Hydric soil rating: No Minor Components Nunn Percent of map unit: 10 percent Hydric soil rating: No Larim Percent of map unit: 10 percent Hydric soil rating: No Stoneham Percent of map unit: 5 percent Hydric soil rating: No Custom Soil Resource Report 14 This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA This unofficial copy was downloaded on Aug-01-2019 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA A PPENDIX D D RAINAGE E XHIBITS N89°22'14"W 491.32' (M)S89°22'14"E 212.50' (M)S00°37'46"W (M)227.20'S00°00'00"E (R)WSEW PROSPECT RDEXISTINGRESIDENCEEXISTINGRESIDENCEEXISTINGBUILDINGEXISTINGPARKING LOTEXISTINGGRAVELEX10.640.350.44EX20.550.320.40EXISTINGIMPROVEMENTSRELATED TO "THE SLAB"PROPERTY ARE NOTCONSIDERED INHISTORIC CONDITIONPATH:0'30'60'SCALE: 1" = 30'15'P:\U19031 - HAVEN APARTMENTS\CADD\ET\2019-10-10_EX DRAINAGE EXHIBIT.DWG 2019-10-10_EX DRAINAGE EXHIBITDRAWING NAME:SHEET SIZE: 11 x 17 APEX-HAVEN APARTMENTSHISTORIC DRAINAGE EXHIBITDATE:March 2, 2020PREPARED FOR:MAXIIIMO DEVELOPMENT GROUPJOB NUMBER:U19031NOTE:THIS EXHIBIT WAS PREPARED FOR INFORMATION ONLY AND THE ENGINEER PREPARING THESE PLANS WILL NOT BE RESPONSIBLE FOR UNAUTHORIZED USE OF THEM.1501 ACADEMY COURT, SUITE 203 FORT COLLINS, CO 80524 (970) 530-4044 WWW.UNITEDCIVIL.COMSHEETOF11UNITED CIVILDesign GroupLLCNORTH DRAINAGE SUMMARYBasinArea%IC2C100Q2Q100(acre)(cfs)(cfs)Existing BasinsEX10.6415.9%0.350.440.502.29EX20.5511.6%0.320.400.381.64TOTAL1.1913.9% 262.50'S00°37'46"W (M)227.20' S00°00'00"E (R)A10.020.951.00A20.030.510.64A30.010.951.00C10.050.440.55D20.060.250.31B10.190.370.46B20.250.760.95E10.090.370.47ON10.060.570.71S10.040.620.78D10.130.420.52WEST PROSPECT ROAD(RIGHT-OF-WAY VARIES)EXISTINGRESIDENCE(BUILDING 2)EXISTINGRESIDENCE(BUILDING 3)PROPOSEDAPARTMENTS(BUILDING 1)EXISTING APEXBUILDINGBIORETENTIONPONDPOND BPOND AUNDERGROUNDWATER QUALITYC20.130.951.001B30.130.951.00DETENTIONPONDPOND CEXISTINGPARKING LOTPOND B OUTLET PIPEPOND OUTLET PIPEFOREBAYPOND OUTLETSTRUCTUREPOND OUTLET STRUCTUREROOF DRAIN SYSTEMCURB CHASE ACURB CHANNEL BMAXIIIMO DEVELOPMENT GROUP 04/28/2021U190311" = 20'1" = N/AAPEX-HAVEN APARTMENTS NORTH 4/27/2021 6:15:12 PMC:\UNITED CIVIL DROPBOX\PROJECTS\U19031 - HAVEN APARTMENTS\CADD\CP\C5.00 - DRAINAGE PLAN.DWGC5.00 - DRAINAGE PLAN KRB CDB C5.0028DRAINAGE PLAN020'40'SCALE: 1" = 20'10'PREPARED FOR:JOB NUMBERSHEET NUMBERSHEETSOFDATE SUBMITTED: The engineer preparing these plans will not be responsible for, or liable for, unauthorized changes to or uses of these plans. All changes to the plans must be in writing and must be approved by the preparer of these plans. NO.BY DATE CAUTIONREVISIONS:VERTICAL:HORIZONTAL:SCALEP R E L IM I N A R Y P L A N SNOT FOR CONSTRUCTION1501 Academy Ct.Ste. 203Fort Collins, CO 80524(970) 530-4044www.unitedcivil.comCivil Engineering &ConsultingPROJ. MGR:DRAWING NAME:PATH:DESIGNER:DATE:TIME:UNITED CIVILDesign GroupLLC15X.XXX.XXXX.XXBASIN DESIGNATIONBASIN AREA (ACRE)2 - YR RUNOFF COEFF.100 - YR RUNOFF COEFF.DESIGN POINTFLOW DIRECTIONDPD1LEGENDDRAINAGE SUMMARYBasinDesign PointArea%IC2C100Q2Q100(acre)(cfs)(cfs)Existing BasinsEX1EX10.6415.9%0.350.440.502.29EX2EX20.5511.6%0.320.400.381.64TOTAL1.1913.9%Proposed BasinsA1A10.0290%0.951.000.050.19A2A20.0335%0.510.640.050.20A3A30.0190%0.951.000.030.12B1B10.1917%0.370.460.170.76B2B20.2568%0.760.950.552.40B3B30.1390%0.951.000.351.27C1C10.0526%0.440.550.060.26C2C20.1390%0.951.000.351.31D1D10.1325%0.420.520.140.66D2D20.062%0.250.310.040.17E1E10.0918%0.370.470.090.41S1S10.0449%0.620.780.070.31ON1ON10.0642%0.570.710.100.44TOTAL1.1949%