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Home My WebLink AboutTHE QUARRY BY WATERMARK - PDP200019 - DOCUMENT MARKUPS - ROUND 3 - DRAINAGE REPORT PRELIMINARY DRAINAGE REPORT THE QUARRY BY WATERMARK FORT COLLINS, COLORADO March 3, 2021 NORTHERNENGINEERING.COM 970.221.4158 FORT COLLINS GREELEY This Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in its entirety. When a hard copy is necessary, we recommend double-sided printing. NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE MEMO: THORNBURG HAMILTON FIFTH SUBDIVISION FORT COLLINS | GREELEY COVER LETTER March 3, 2021 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, CO 80521 RE: PRELIMINARY DRAINAGE REPORT FOR THE QUARRY BY WATERMARK Dear Staff, Northern Engineering is pleased to submit this Preliminary Drainage Report for your review. This report accompanies the combined Preliminary Plan submittal for the proposed The Quarry by Watermark This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM) and serves to document the stormwater impacts associated with the proposed The Quarry by Watermark housing project. We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in the FCSCM. If you should have any questions as you review this report, please feel free to contact us. Sincerely, NORTHERN ENGINEERING SERVICES, INC. MASON RUEBEL, EI DANNY WEBER, PE Project Engineer Project Manager NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: THORNBURG HAMILTON FIFTH SUBDIVISION FORT COLLINS | GREELEY TABLE OF CONTENTS TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION ................................................................ 1 II. DRAINAGE BASINS AND SUB-BASINS ..................................................................... 3 III. DRAINAGE DESIGN CRITERIA ................................................................................ 4 IV. DRAINAGE FACILITY DESIGN ................................................................................. 6 V. CONCLUSIONS .................................................................................................. 10 VI. REFERENCES .................................................................................................... 10 TABLES AND FIGURES Figure 1 – Vicinity Map ........................................................................................................1 Figure 2 – Aerial Photograph ..............................................................................................2 Figure 3 – FEMA Firmette (Map Numbers 08069CO978G and 08069CO979H) ..................3 APPENDICES APPENDIX A – HYDROLOGIC COMPUTATIONS APPENDIX B – HYDRAULIC COMPUTATIONS APPENDIX C – WATER QUALITY COMPUTATIONS APPENDIX D – DETENTION POND & SWMM MODEL APPENDIX E – EROSION CONTROL REPORT APPENDIX F – USDA SOILS REPORT APPENDIX G – FEMA FIRMETTE MAP POCKET DR1 – DRAINAGE EXHIBIT NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 1 | 21 I. GENERAL LOCATION AND DESCRIPTION A. LOCATION Vicinity Map Figure 1 – Vicinity Map The Quarry by Watermark project site is located in the northwest quarter of Section 23, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. The project site (refer to Figure 1) is bordered to the north by Hobbit Street; to the east by Canal Importation Ditch; to the south by Spring Creek; and to the west by Shields Street. Spring Creek and Canal Importation Ditch are a major drainageways located adjacent to the project site. The confluence of Spring Creek and Canal Importation Ditch is in the southeast corner of the site. B. DESCRIPTION OF PROPERTY The Quarry by Watermark comprises of ± 19.38 acres. The site is currently an undeveloped parcel surrounded by multi-family to the north, west, and south and single-family homes to the east NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 2 | 21 Figure 2 – Aerial Photograph The existing groundcover consists of short grasses. The existing on-site runoff generally drains from the northwest to the southeast across flat grades (e.g., <1.00%) into the Canal Importation Ditch. From there, the drainage continues through Canal Importation Ditch to Spring Creek, and on to the Cache La Poudre River. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx), the site consists primarily of Altvan-Satanta loams (Hydrologic Soil Group B) and Nunn clay loam (Hydrological Soil Group C). Springs Creek and Canal Importation Ditch are the only major drainageways within or adjacent to the project site. The proposed development will consist of seventeen (17) townhome buildings containing a total of 313 units with detached garages. Other proposed improvements include parking lots, sidewalks, pool, clubhouse, and landscaping. The proposed land use is multi-family. This is a permitted use in the Medium-Density Mixed-Use Neighborhood District (MMN). C. FLOODPLAIN 1. The eastern and southern edges of the site is in a FEMA regulatory floodplain; however, the developable project area is outside of the FEMA floodplain. In particular, the FEMA designated 100-year floodplain Basins E1 and E2 on the Drainage Exhibit includes the FEMA regulatory floodplains for Spring Creek and Canal Importation Ditch (Map Numbers 08069CO978G and 08069CO979H and effective date of May 2, 2012). The eastern portion on this site, along the Canal Importation Ditch, is located within the City of Fort Collins Regulatory floodplain/floodway. No development is proposed within Basins E1 and E2. A copy of the FEMA Firmette is provided in Appendix G. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 3 | 21 2. We have analyzed the FEMA Floodplain map and cross sections for Spring Creek and Canal Importation Ditch and determined that the highest base flood elevation adjacent to the project site is 5016 (NAVD88). All buildings have been elevated 1.5’ above this elevation. Furthermore, the buildings all maintain a minimum of 12” between the finished floor elevation and the top of bank along the south and east side of the property. II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description The north and east halves of The Quarry by Watermark is located within the City of Fort Collins Canal Importation major drainage basin. The southwest quarter of the site is located within the City of Fort Collins Spring Creek major drainage basin. Specifically, the project site is situated at the confluence of the Spring Creek and Canal Importation major drainage basins. Detention requirements for this basin are to detain the difference between the 100-yr developed inflow rate and the historic 2-year release rate. B. Sub-Basin Description The outfall for the project site is at the confluence of Springs Creek and Canal Importation Basins. The existing subject site can be defined with twelve (22) sub-basins that encompasses the entire project site and three (3) offsite basins that drain onto the project site. The existing site runoff generally drains from northwest-to-southeast and into the Canal Importation Ditch. The project site receives runoff from Shields Street and Hobbit Street. Figure 3 – FEMA Firmette (Map Numbers 08069CO978G and 08069CO979H) NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 4 | 21 III. DRAINAGE DESIGN CRITERIA A. Optional Provisions There are no optional provisions outside of the FCSCM proposed with the Quarry by Watermark. B. STORMWATER MANAGEMENT STRATEGY The overall stormwater management strategy employed with The Quarry by Watermark utilizes the “Four Step Process” to minimize adverse impacts of urbanization on receiving waters. The following is a description of how the proposed development has incorporated each step. Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the stormwater impacts of this development is the site selection itself. By choosing an already developed site with public storm sewer currently in place, the burden is significantly less than developing a vacant parcel absent of any infrastructure. The Quarry by Watermark aims to reduce runoff peaks, volumes and pollutant loads from frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and 2-year storm events) by implementing Low Impact Development (LID) strategies. Wherever practical, runoff will be routed across landscaped areas or through a rain garden or water quality pond. These LID practices reduce the overall amount of impervious area, while at the same time Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA techniques will be implemented, where practical, throughout the development, thereby slowing runoff and increasing opportunities for infiltration. Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow Release. The efforts taken in Step 1 will help to minimize excess runoff from frequently occurring storm events; however, urban development of this intensity will still have stormwater runoff leaving the site. The primary water quality treatment will occur between underground vaults located at the south end of the project and a single rain garden along the east side of the property. The remaining runoff will be treated for water quality in the proposed detention ponds along the Spring Creek. Step 3 – Stabilize Drainageways. As stated in Section I.B.6, above, the Spring Creek and Canal Importation drainage is adjacent to the subject site, however no changes to the channel are proposed with this project. While this step may not seem applicable to The Quarry by Watermark, the proposed project indirectly helps achieve stabilized drainageways, nonetheless. Once again, site selection has a positive effect on stream stabilization. By developing an infill site with stormwater infrastructure, combined with LID and MDCIA strategies, the likelihood of bed and bank erosion and the frequency of erosive flows are reduced. Furthermore, this project will pay one-time stormwater development fees, as well as ongoing monthly stormwater utility fees, both of which help achieve Citywide drainageway stability. Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to industrial and commercial developments. C. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS The subject property is not part of any Overall Development Plan (ODP) drainage study or similar “development/project” drainage master plan. The site plan is constrained to the north and west by public streets, to the south by Spring Creek, and to the east by the Canal Importation Ditch. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 5 | 21 D. HYDROLOGICAL CRITERIA The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure 3.4-1 of the FCSCM, serve as the source for all hydrologic computations associated with The Quarry by Watermark development. Tabulated data contained in Table 3.4-1 has been utilized for Rational Method runoff calculations. The Rational Method has been used to estimate peak developed stormwater runoff from drainage basins within the developed site for the 2-year, 10-year, and 100-year design storms. Peak runoff discharges determined using this methodology have been used to check the street capacities, inlets, swales, and storm drain lines. Two separate design storms have been utilized to address distinct drainage scenarios. The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second event considered is the “Major Storm,” which has a 100-year recurrence interval. E. HYDRAULIC CRITERIA The drainage facilities proposed with The Quarry by Watermark project are designed in accordance with criteria outlined in the FCSCM. As stated in Section I.C.1, above, the subject property is located next to a FEMA designated floodplain but is not located within the floodplain limits. F. FLOODPLAIN REGULATIONS COMPLIANCE As previously mentioned, this project is adjacent to a FEMA regulated floodplain. The developable area of the project is located outside of the floodplain, and as such, it will not be subject to any floodplain regulations. However, the storm outfall will be located within the floodway, and that work will be subject to the applicable floodplain regulations of Chapter 10 of the City Municipal Code. Despite most of the project not being located within the floodplain, consideration has been given to the floodplain elevations as they relate to the proposed buildings and the finished floors have been elevated accordingly. G. MODIFICATIONS OF CRITERIA There are no optional provisions outside of the FCSCM proposed with the Quarry by Watermark. H. CONFORMANCE WITH WATER QUALITY TREATMENT CRITERIA City Code requires that 100% of runoff from impervious surfaces in a project site shall receive some sort of water quality treatment. This project proposes to provide water quality treatment using several methods. A single rain garden will be located along the east edge of the site. Two separate areas along the south side of the site will use underground chambers for treatment. Both areas will discharge into two proposed detention ponds that will provide water quality for the remainder of the site before discharge into the Canal Importation Basin. Due to the physical constraints associated with an infill project of this nature and the prohibition of providing water quality facilities within the public right-of-way, there are some small, narrow areas around the perimeter of the project that cannot be captured. The uncaptured areas tend to be narrow strips of concrete flatwork that link the building entrances to the public sidewalks as well as small planter beds between the building and public sidewalks or property lines. While these small areas will not receive formal water quality treatment, most areas will still see some treatment as runoff is directed across through the landscaped areas or across the landscaped NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 6 | 21 parkways before reaching the roadway curb and gutter. I. CONFORMANCE WITH LOW IMPACT DEVELOPMENT (LID) The project site will conform with the requirement to treat a minimum of 75% of the project site using a LID technique. A single rain garden and underground chambers will be used to capture and filter or infiltrate the water quality capture volume. J. SIZING OF LID FACILITIES Rain Gardens/Underground Chambers 1. The rain gardens and chambers were sized by first determining the required water quality capture volume (WQCV) for Basins B1-B7 for the rain garden and Basins A2 & D4-7 for the chambers. A 12-hour drain time was used in this calculation. 2. Once the WQCV was identified, each rain garden and chamber area were sized for its respective WQCV. The rain gardens will be constructed with a biomedia filter and underdrain. An overflow drain will be provided in each rain garden and weir for chambers to pass storms greater than the WQCV. Water Quality Pond 1. The water quality pond was sized by first determining the required water quality capture volume (WQCV) for Basins D1 and A3. Offsite flows from Basins OS1 and OS2 (Shields Street) will be treated in the water quality ponds. A 40-hour drain time was used in this calculation. 2. Once the WQCV was identified, the water quality pond was sized to provide the WQCV. An outlet control structure with overflow will be provided to pass storms greater than the WQCV. IV. DRAINAGE FACILITY DESIGN A. GENERAL CONCEPT 1. The main objective of The Quarry by Watermark drainage design is to maintain existing drainage patterns, while not adversely impacting adjacent properties 2. A list of tables and figures used within this report can be found in the Table of Contents at the front of the document. The tables and figures are located within the sections to which the content best applies. 3. Drainage for the project site has been analyzed using twenty-one (22) onsite drainage sub- basins, designated as sub-basins A1- A2, B1-B7, C1-C2, D1-D7, E1-E2, and F1-F2. Furthermore, there are three (3) offsite drainage sub-basins designated as sub-basins OS1, OS2, and OS3. The drainage patterns anticipated for the basins are further described below. Sub-Basins A1 Sub-Basins A1 encompasses approximately 7% of the total site area. Basin A1 contains Detention Pond 1 which is the collection point of every sub-basin on site before release into the Canal Importation Ditch. This pond, in conjunction with Detention Pond 2, will moderate the release rate into the ditch during the Major Storm. An outlet structure with a restrictor plate will be installed with Pond 1 and an outfall pipe will be used for the discharge into the Canal Importation Ditch. Emergency Overflow from this pond will be directed into the Canal Importation Ditch. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 7 | 21 Sub-Basins A2 Sub-Basin A2 encompasses approximately 9% of the total site area. Basin A2 is comprised primarily of roof area, concrete flatwork, parking lot and landscaped areas. This basin will drain into a valley pan and curb and gutter located in the parking lot and be captured by an inlet and storm drain. This area will be treated by Stormtech Chambers 2, located just south of the collection point. The WQCV will be captured in these chambers during the minor storm and flow from larger storms will then proceed to Detention Pond 1 and the Canal Importation Ditch. Sub-Basin B1 – B7 Sub-Basins B1 through B7 encompasses approximately 36% the total site area. Basin B1 mainly comprises of Rain Garden A, which will be the main treatment method for the B sub-basins. Minor flows will be treated in this rain garden, while flows from larger storms will proceed to Detention Pond 1 and to the Canal Importation ditch. The remaining sub-basins (B2-B7) are comprised primarily of roof area, concrete flatwork, parking lot, and landscaped areas. The sub-basins will drain into a valley pan and curb & gutter located within each sub-basin and towards a common storm sewer. This common storm sewer will discharge into Rain Garden A. Storm sewers will be sized to convey major storms. Sub-Basin C1 Sub-basin C1 is comprised of an existing ditch along the north property line (Ditch C). This existing ditch conveys runoff from OS3 (Hobbit Street) and discharges directly into the Canal Importation Ditch. This is an existing condition and there will be no added flows or change in drainage patterns. Sub-Basin C2 This sub-basin is comprised primarily of roof area, concrete flatwork, and landscaped areas. Flows from the sub-basin will flow north into curb and gutter along Hobbit Street. Hobbit Street will convey runoff, along with drainage from Sub-Basin OS3 to Ditch C. Flows will then proceed to the Canal Importation Ditch. Sub-Basin D1 Sub-Basins D1 encompasses approximately 5% the total site area. This basin contains Detention Pond 2, which will collect runoff from Sub-Basins D, F, and the offsite flows from Shields (OS1 & OS2). Detention Pond 2 will serve as the water quality pond for the remaining basins that are not treated with LID. An outlet structure will be constructed with a water quality plate and restrictor plate. The outfall for Pond 2 will discharge into Pond 1. The combination of the detention ponds will lower the release rate into the Canal Importation Ditch. Emergency overflow from detention pond 2 will spill into detention pond 1 prior to discharging into the Canal Importation Ditch Sub-Basin D2 Sub-Basin D2 encompasses approximately 1% the total site area. This sub-basin is comprised primarily of primarily of landscaped areas. No development is proposed in this area and flows from the sub-basin will discharge directly into Spring Creek. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 8 | 21 Sub-Basin D3 These sub-basins are comprised primarily of roof area, concrete flatwork, parking lot, and landscaped areas. The sub-basins will drain into a common storm sewer via valley pans and curb and gutter. The storm sewer will collect drainage from all the sub-basins, including Sub-Basins OS1 and OS2, and discharge into Detention Pond 2. Flows will then proceed to the Canal Importation Ditch. Sub-Basin D4-D7 Sub-Basin D2 encompasses approximately 14% the total site area. These sub-basins are comprised primarily of roof area, concrete flatwork, parking lot, and landscaped areas. The sub- basins will drain into a common storm sewer via valley pans and curb and gutter. The storm sewer will collect drainage from all the sub-basins and discharge into Stormtech Chambers 1. The WQCV will be captured in these chambers during minor flows. Larger flows will bypass the chambers and discharge directly into Detention Pond 2. Flows will then proceed to the Canal Importation Ditch. Storm sewer will be sized to convey major storms. Sub-Basin E1 Sub-basin E1 encompasses approximately 17% the total site area. This sub-basin comprises of the Spring Creek flood plain. No improvements, except for storm sewer outfalls, are proposed within this sub-basin Sub-Basin E2 Sub-basin E2 encompasses approximately 7% the total site area. This sub-basin comprises of the Canal Importation flood plain. No improvements, except for storm sewer outfalls, are proposed within this sub-basin Sub-Basins F1 & F2 Sub-basins F1 and F2 encompasses approximately 1% the total site area. These sub-basins are comprised primarily of concrete flatwork and landscaped areas. Flows from the sub-basin will drain into curb and gutter along Shield Street. The curb and gutter will then convey the flows to the intersection of Shields Street and Stuart Street (also the west entrance of the site), into Sub- Basin D3, and ultimately Detention Pond 2. Flows will then proceed to the Canal Importation Ditch. Sub-Basin OS1 & OS2 Offsite Sub-Basins OS1 and OS2 consists of the west edge of Shields Street that directly impacts the project site. These sub-basins are comprised primarily of asphalt, concrete flatwork, and a landscaped parkway. Flows from the sub-basin will drain into curb and gutter along Shield Street. The curb and gutter will then convey the flows to the intersection of Shields Street and Stuart Street (also the west entrance of the site), into Sub-Basin D3, and ultimately into Water Quality Pond D. Half of the flow from these basins will be treated in Detention Pond 2 and will then proceed to Pond 1 and the Canal Importation Ditch. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 9 | 21 Sub-Basin OS3 Offsite Sub-Basins OS3 consists of Hobbit Street north of the project site. This sub-basin is comprised primarily of asphalt and concrete flatwork. Flows from the sub-basin will drain into curb and gutter along Hobbit Street. The curb and gutter will then convey the flows to Ditch C and ultimately into the Canal Importation Ditch. A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report. B. SPECIFIC DETAILS Two detention ponds are proposed with this development and will detain up to the 100-yr storm event and release at or below the caluclated release rate. A SWMM model was created to deterim the detention volumes. See Appendix C for more detail. See table 1 for detention summary. Table 1 – Detention Summary LID treatment is being provided within Rain Garden 1 and Stormtech Chambers 1 & 2. These provide mare that the required LID treatement of 75% of the impervious site runoff. Please see the LID exhibt and calculations in Appendix C. Detention allowable release rate is based on computed 2-year historic flow for the overall property. We have added historic flow from Right of Way area in addition to the property. Basins OS1 and OS2 (Please see Historic Drainage Exhibit), with a combined area of 2.28 acres, will be taken into Pond 2 and will be detained. Thus, we have added 2-year historic flow from these basins to the site allowable release. Based on historic flow computations provided in the appendix, the summation of onsite historic 2-year flow and 2-year flows from Basins OS1 and OS2 is 11.5 cfs. We propose to release slightly below this rate as shown in Table 1, above. Stormwater facility Standard Operations Procedures (SOP) will be provided by the City of Fort Collins in the Development Agreement. Final Design details, and construction documentation shall be provided to the City of Fort Collins for review prior to Final Development Plan approval. Pond ID 100-Yr. Detention Vol. (Ac-Ft) Peak Release (cfs) WQCV (Ac-Ft) Pond 1 1.99 5.10 n/a Pond 2 0.89 5.60 0.13 POND SUMMARY TABLE NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE QUARRY BY WATERMARK FORT COLLINS | GREELEY 10 | 21 V. CONCLUSIONS A. COMPLIANCE WITH STANDARDS The drainage design proposed with The Quarry by Watermark complies with the City of Fort Collins Master Drainage Plan for the Spring Creek and Canal Importation Basins. The project is adjacent to the Spring Creek and Canal Importation FEMA regulatory floodplains. However, the development is constructed outside of the floodplains, and buildings are located 18-inches above the base flood elevation. No improvements are proposed within the FEMA regulated floodplains. All applicable provisions within Chapter 10 of the City Municipal Code shall be adhered to. The drainage plan and stormwater management measures proposed with The Quarry by Watermark project are compliant with all applicable State and Federal regulations governing stormwater discharge. B. DRAINAGE CONCEPT The drainage plan and stormwater management measures proposed with The Quarry by Watermark project are compliant with all applicable State and Federal regulations governing stormwater discharge. The Quarry by Watermark will not impact the Master Drainage Plan recommendations for the Canal Importation and Spring Creek major drainage basin. VI. REFERENCES Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright- McLaughlin Engineers, Denver, Colorado, Revised April 2008. NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: THORNBURG HAMILTON FIFTH SUBDIVISION FORT COLLINS | GREELEY APPENDIX APPENDIX A HYDROLOGIC COMPUTATIONS Runoff Coefficient1 Percent Impervious1 0.95 100% 0.95 90% 0.50 40% 0.50 40% 0.20 2% 0.20 2% Basin ID Basin Area (sq.ft.) Basin Area (acres) Asphalt, Concrete (acres)Rooftop (acres) Gravel (acres) Pavers (acres) Undeveloped: Greenbelts, Agriculture (acres) Lawns, Clayey Soil, Flat Slope < 2% (acres) Percent Impervious C2*Cf Cf = 1.00 C5*Cf Cf = 1.00 C10*Cf Cf = 1.00 C100*Cf Cf = 1.25 H-A1 44,062 1.012 0.000 0.000 0.000 0.000 1.012 0.000 2%0.20 0.20 0.20 0.25 H-A2 6,773 0.155 0.000 0.000 0.000 0.000 0.155 0.000 2%0.20 0.20 0.20 0.25 H-B1 110,004 2.525 0.000 0.000 0.000 0.000 2.525 0.000 2%0.20 0.20 0.20 0.25 H-B2 170,633 3.917 0.015 0.000 0.000 0.000 3.902 0.000 2%0.20 0.20 0.20 0.25 H-B3 19,023 0.437 0.020 0.000 0.000 0.000 0.417 0.000 6%0.23 0.23 0.23 0.29 H-C1 32,204 0.739 0.000 0.000 0.000 0.000 0.739 0.000 2%0.20 0.20 0.20 0.25 H-C2 238,190 5.468 0.009 0.000 0.000 0.000 5.459 0.000 2%0.20 0.20 0.20 0.25 H-D1 7,509 0.172 0.000 0.000 0.000 0.000 0.172 0.000 2%0.20 0.20 0.20 0.25 H-E1 147,424 3.384 0.283 0.019 0.000 0.000 3.082 0.000 11%0.27 0.27 0.27 0.33 H-E2 60,287 1.384 0.143 0.002 0.000 0.000 1.239 0.000 12%0.28 0.28 0.28 0.35 H-F1 1,947 0.045 0.028 0.000 0.000 0.000 0.000 0.017 64%0.67 0.67 0.67 0.84 H-F2 7,695 0.177 0.094 0.000 0.000 0.000 0.000 0.082 54%0.60 0.60 0.60 0.75 OS1 21,067 0.484 0.407 0.000 0.000 0.000 0.000 0.077 84%0.83 0.83 0.83 1.00 OS2 78,428 1.800 1.706 0.000 0.000 0.000 0.000 0.094 95%0.91 0.91 0.91 1.00 Comb OS1, OS2 99,495 2.284 2.113 0.000 0.000 0.000 0.000 0.171 93%0.89 0.89 0.89 1.00 OS3 20,406 0.468 0.405 0.000 0.000 0.000 0.000 0.063 87%0.25 0.25 0.25 0.31 Total- Onsite 849,927 19.512 0.167 0.000 0.000 0.000 14.209 0.099 2%0.20 0.20 0.20 0.25 EXISTING RUNOFF COEFFICIENT CALCULATIONS Asphalt, Concrete Rooftop Gravel Pavers The Quarry by Watermark A.Cvar March 2, 2021 Project: Calculations By: Date: Character of Surface Streets, Parking Lots, Roofs, Alleys, and Drives: Lawns and Landscaping: Combined Basins 2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins Stormwater Manual (FCSM). Lawns, Clayey Soil, Flat Slope < 2% USDA SOIL TYPE: C Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2 1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM. Page 1 of 1 Project: Date: Where: Length (ft) Elev Up Elev Down Slope (%) Ti 2-Yr (min) Ti 10-Yr (min) Ti 100-Yr (min) Length (ft) Elev Up Elev Down Slope (%)Surface Roughness (n) Flow Area3 (sq.ft.) WP 3 (ft) Hydraulic Radius (ft) Velocity (ft/s) Tt (min) Max. Tc (min) Comp. Tc 2-Yr (min) Tc 2-Yr (min) Comp. Tc 10-Yr (min) Tc 10-Yr (min) Comp. Tc 100-Yr (min) Tc 100-Yr (min) h-a1 H-A1 200 15.34 10.61 2.37%17.9 17.9 16.9 159 10.61 7.95 1.67%Swale (4:1)0.025 4.00 8.25 0.48 4.76 0.56 11.99 18.42 11.99 18.42 11.99 17.43 11.99 h-a2 H-A2 45 15.23 14.59 1.42%10.0 10.0 9.5 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.25 10.04 10.04 10.04 10.04 9.48 9.48 h-b1 H-B1 200 14.80 13.63 0.59%28.5 28.5 26.9 278 13.63 11.74 0.68%Swale (8:1)0.025 8.00 16.12 0.50 3.08 1.50 12.66 29.96 12.66 29.96 12.66 28.38 12.66 h-b2 H-B2 148 17.33 16.31 0.69%23.1 23.1 21.8 365 16.31 13.44 0.79%Swale (8:1)0.025 8.00 16.12 0.50 3.31 1.84 12.85 24.94 12.85 24.94 12.85 23.63 12.85 h-b3 H-B3 52 17.33 16.20 2.17%9.0 9.0 8.4 180 16.20 15.20 0.56%Swale (4:1)0.025 4.00 8.25 0.48 2.74 1.09 11.29 10.11 10.11 10.11 10.11 9.50 9.50 h-c1 H-C1 90 17.23 10.63 7.33%8.2 8.2 7.8 175 10.63 10.10 0.30%Swale (4:1)0.025 4.00 8.25 0.48 2.02 1.44 11.47 9.66 9.66 9.66 9.66 9.20 9.20 h-c2 H-C2 60 17.48 16.29 1.98%10.4 10.4 9.8 826 16.29 13.33 0.36%Swale (8:1)0.025 8.00 16.12 0.50 2.24 6.16 14.92 16.52 14.92 16.52 14.92 15.94 14.92 h-d1 H-D1 60 19.31 17.33 3.30%8.8 8.8 8.3 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.33 8.75 8.75 8.75 8.75 8.26 8.26 h-e1 H-E1 65 17.28 11.43 9.00%6.0 6.0 5.6 1272 11.43 3.16 0.65%Floodplain 0.045 46.50 23.32 1.99 4.23 5.01 17.43 11.05 11.05 11.05 11.05 10.57 10.57 h-e2 H-E2 40 14.10 7.58 16.30%3.8 3.8 3.5 735 7.58 4.17 0.46%Floodplain 0.035 18.00 13.00 1.38 3.60 3.40 14.31 7.23 7.23 7.23 7.23 6.91 6.91 h-f1 H-F1 22 18.47 17.99 2.18%2.9 2.9 1.8 175 17.99 17.00 0.57%Gutter 0.012 3.61 19.18 0.19 3.07 0.95 11.09 3.84 5.00 3.84 5.00 2.70 5.00 h-f2 H-F2 40 20.24 19.49 1.88%4.8 4.8 3.4 570 19.49 16.79 0.47%Gutter 0.012 3.61 19.18 0.19 2.81 3.38 13.39 8.18 8.18 8.18 8.18 6.74 6.74 os1 OS1 30 22.53 21.47 3.53%1.8 1.8 0.7 420 21.47 16.95 1.08%Gutter 0.012 3.61 19.18 0.19 4.23 1.65 12.50 3.47 5.00 3.47 5.00 2.33 5.00 os2 OS2 26 36.00 34.55 5.58%1.0 1.0 0.5 1738 34.55 16.79 1.02%Gutter 0.012 3.61 19.18 0.19 4.12 7.02 19.80 8.04 8.04 8.04 8.04 7.56 7.56 Comb OS1, OS2 Comb OS1, OS2 26 36.00 34.55 5.58% 5.9 5.9 5.9 1738 34.55 16.79 1.02% Gutter 0.012 3.61 19.18 0.19 4.12 7.02 19.80 12.94 12.94 12.94 12.94 12.94 12.94 os3 OS3 32 20.10 20.05 0.16%16.7 16.7 15.5 615 20.05 12.88 1.17%Gutter 0.012 3.61 19.18 0.19 4.40 2.33 13.59 19.02 13.59 19.02 13.59 17.79 13.59 Total- Onsite Total- Onsite 60 17.48 16.29 1.98% 12.7 12.7 12.7 826 16.29 13.33 0.36% Swale (8:1) 0.025 8.00 16.12 0.50 2.24 6.16 14.92 18.84 14.92 18.84 14.92 18.84 14.92 EXISTING TIME OF CONCENTRATION COMPUTATIONS Overland Flow, Time of Concentration: Calculations By: The Quarry by Watermark A.Cvar R = Hydraulic Radius (feet) S = Longitudinal Slope, feet/feet Maximum Tc: Combined Basins Design Point Basin Overland Flow Channelized Flow Time of Concentration Channelized Flow, Velocity:Channelized Flow, Time of Concentration: V = Velocity (ft/sec) n = Roughness Coefficient March 2, 2021 (Equation 3.3-2 per Fort Collins Stormwater Manual) 𝑇௜ =1.87 1.1 −𝐶∗𝐶𝑓𝐿 𝑆ଵ ଷൗ 𝑉=1.49 𝑛∗𝑅ଶ/ଷ ∗𝑆(Equation 5-4 per Fort Collins Stormwater Manual) 𝑇𝑐=𝐿 180 + 10 (Equation 3.3-5 per Fort Collins Stormwater Manual) 𝑇𝑡=𝐿 𝑉∗ 60 (Equation 5-5 per Fort Collins Stormwater Manual) Notes: 1) Add 5000 to all elevations. 2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min. 3) Assume a water depth of 6" and a typical curb and gutter per Larimer County Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a water depth of 1', fixed side slopes, and a triangular swale section for grass channelized flow. Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley pan for channelized flow in a valley pan. Page 1 of 1 Tc2 Tc10 Tc100 C2 C10 C100 I2 (in/hr) I10 (in/hr) I100 (in/hr) Q2 (cfs) Q10 (cfs) Q100 (cfs) h-a1 H-A1 1.012 11.99 11.99 11.99 0.20 0.20 0.25 2.09 3.57 7.29 0.4 0.7 1.8 h-a2 H-A2 0.155 10.04 10.04 9.48 0.20 0.20 0.25 2.21 3.78 8.03 0.1 0.1 0.3 h-b1 H-B1 2.525 12.66 12.66 12.66 0.20 0.20 0.25 2.02 3.45 7.04 1.0 1.7 4.4 h-b2 H-B2 3.917 12.85 12.85 12.85 0.20 0.20 0.25 2.02 3.45 7.04 1.6 2.7 7.0 h-b3 H-B3 0.437 10.11 10.11 9.50 0.23 0.23 0.29 2.21 3.78 8.03 0.2 0.4 1.0 h-c1 H-C1 0.739 9.66 9.66 9.20 0.20 0.20 0.25 2.26 3.86 8.03 0.3 0.6 1.5 h-c2 H-C2 5.468 14.92 14.92 14.92 0.20 0.20 0.25 1.90 3.24 6.62 2.1 3.6 9.1 h-d1 H-D1 0.172 8.75 8.75 8.26 0.20 0.20 0.25 2.35 4.02 8.38 0.1 0.1 0.4 h-e1 H-E1 3.384 11.05 11.05 10.57 0.27 0.27 0.33 2.13 3.63 7.57 1.9 3.3 8.6 h-e2 H-E2 1.384 7.23 7.23 6.91 0.28 0.28 0.35 2.52 4.31 9.06 1.0 1.7 4.4 h-f1 H-F1 0.045 5.00 5.00 5.00 0.67 0.67 0.84 2.85 4.87 9.95 0.1 0.1 0.4 h-f2 H-F2 0.177 8.18 8.18 6.74 0.60 0.60 0.75 2.40 4.10 9.06 0.3 0.4 1.2 os1 OS1 0.484 5.00 5.00 5.00 0.83 0.83 1.00 2.85 4.87 9.95 1.1 2.0 4.8 os2 OS2 1.800 8.04 8.04 7.56 0.91 0.91 1.00 2.40 4.10 8.59 3.9 6.7 15.5 Comb OS1, OS2 Comb OS1, OS2 2.284 12.94 12.94 12.94 0.89 0.89 1.00 2.02 3.45 7.04 4.1 7.0 16.1 os3 OS3 0.468 13.59 13.59 13.59 0.25 0.25 0.31 1.95 3.34 6.82 0.2 0.4 1.0 Total-Onsite Total-Onsite 19.512 14.92 14.92 14.92 0.20 0.20 0.20 1.90 3.24 6.62 7.4 12.6 25.8 EXISTING DIRECT RUNOFF COMPUTATIONS Intensity Flow The Quarry by Watermark A.Cvar March 2, 2021 Project: Calculations By: Date: Rational Equation: Q = CiA (Equation 6-1 per MHFD) Design Point Basin Area (acres) Runoff C Combined Basins Intensity, I from Fig. 3.4.1 Fort Collins Stormwater Manual Tc (Min) Page 1 of 1 Runoff Coefficient 1 Percent Impervious1 0.95 100% 0.95 90% 0.50 40% 0.85 90% 0.20 2% 0.20 2% Basin ID Basin Area (sq.ft.) Basin Area (acres) Asphalt, Concrete (acres)Rooftop (acres) Gravel (acres) Residential: High Density (acres) Undeveloped: Greenbelts, Agriculture (acres) Lawns, Clayey Soil, Flat Slope < 2% (acres) Percent Impervious C2*Cf Cf = 1.00 C5*Cf Cf = 1.00 C10*Cf Cf = 1.00 C100*Cf Cf = 1.25 A1 57,578 1.322 0.036 0.009 0.000 0.000 0.000 1.277 5%0.23 0.23 0.23 0.28 A2 76,238 1.750 1.220 0.133 0.000 0.000 0.000 0.397 77%0.78 0.78 0.78 0.97 B1 26,648 0.612 0.051 0.152 0.000 0.000 0.000 0.409 32%0.45 0.45 0.45 0.56 B2 23,356 0.536 0.248 0.191 0.000 0.000 0.000 0.098 79%0.81 0.81 0.81 1.00 B3 151,782 3.484 1.890 0.820 0.000 0.000 0.000 0.774 76%0.78 0.78 0.78 0.98 B4 12,548 0.288 0.241 0.022 0.000 0.000 0.000 0.025 91%0.88 0.88 0.88 1.00 B5 20,910 0.480 0.007 0.269 0.000 0.000 0.000 0.205 53%0.63 0.63 0.63 0.79 B6 49,947 1.147 0.666 0.321 0.000 0.000 0.000 0.159 84%0.85 0.85 0.85 1.00 B7 21,377 0.491 0.037 0.241 0.000 0.000 0.000 0.213 53%0.62 0.62 0.62 0.78 C1 4,634 0.106 0.000 0.000 0.000 0.000 0.000 0.106 2%0.20 0.20 0.20 0.25 C2 7,076 0.162 0.007 0.080 0.000 0.000 0.000 0.075 50%0.60 0.60 0.60 0.75 D1 42,626 0.979 0.060 0.000 0.000 0.000 0.000 0.919 8%0.25 0.25 0.25 0.31 D2 9,531 0.219 0.000 0.000 0.000 0.000 0.000 0.219 2%0.20 0.20 0.20 0.25 D3 9,336 0.214 0.104 0.080 0.000 0.000 0.000 0.030 82%0.84 0.84 0.84 1.00 D4 33,439 0.768 0.600 0.130 0.000 0.000 0.000 0.038 93%0.91 0.91 0.91 1.00 D5 50,568 1.161 0.670 0.300 0.000 0.000 0.000 0.191 81%0.83 0.83 0.83 1.00 D6 2,943 0.068 0.009 0.033 0.000 0.000 0.000 0.026 58%0.67 0.67 0.67 0.83 D7 27,830 0.639 0.067 0.270 0.000 0.000 0.000 0.302 49%0.60 0.60 0.60 0.74 E1 147,424 3.384 0.283 0.019 0.000 0.000 3.082 0.000 11%0.27 0.27 0.27 0.33 E2 60,287 1.384 0.143 0.002 0.000 0.000 1.239 0.000 12%0.28 0.28 0.28 0.35 F1 1,947 0.045 0.028 0.000 0.000 0.000 0.000 0.017 64%0.67 0.67 0.67 0.84 F2 7,690 0.177 0.094 0.000 0.000 0.000 0.000 0.082 54%0.60 0.60 0.60 0.75 OS1 21,067 0.484 0.407 0.000 0.000 0.000 0.000 0.077 84%0.83 0.83 0.83 1.00 OS2 78,428 1.800 1.706 0.000 0.000 0.000 0.000 0.094 95%0.91 0.91 0.91 1.00 OS3 38,019 0.873 0.750 0.000 0.000 0.000 0.000 0.468 87%0.92 0.92 0.92 1.00 Total 845,715 19.415 6.461 3.072 0.000 0.000 4.321 5.562 49%2.25 2.25 2.25 1.00 Lawns and Landscaping: Combined Basins 2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins Stormwater Manual (FCSM). Lawns, Clayey Soil, Flat Slope < 2% USDA SOIL TYPE: C Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient 2 1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM. DEVELOPED RUNOFF COEFFICIENT CALCULATIONS Asphalt, Concrete Rooftop Gravel Residential: High Density The Quarry by Watermark M. Ruebel March 1, 2021 Project: Calculations By: Date: Character of Surface Streets, Parking Lots, Roofs, Alleys, and Drives: Page 1 of 11 Project: Date: Where: V = Velocity (ft/sec) n = Roughness Coefficient R = Hydraulic Radius (feet) S = Longitudinal Slope, feet/feet Length (ft) Slope (%) Ti 2-Yr (min) Ti 10-Yr (min) Ti 100-Yr (min) Length (ft) Slope (%)Surface Roughness (n) Flow Area3 (sq.ft.) WP 3 (ft) Hydraulic Radius (ft) Velocity (ft/s) Tt (min) Max. Tc (min) Comp. Tc 2-Yr (min) Tc 2-Yr (min) Comp. Tc 10-Yr (min) Tc 10-Yr (min) Comp. Tc 100-Yr (min) Tc 100-Yr (min) a1 A1 5 5.00%2.1 2.1 2.0 570 1.61%Valley Pan 0.015 6.00 10.25 0.59 0.88 10.76 13.19 12.90 12.90 12.90 12.90 12.76 12.76 a2 A2 50 2.00%3.4 3.4 1.3 915 0.50%Valley Pan 0.015 6.00 10.25 0.59 0.49 30.94 15.36 34.30 15.36 34.30 15.36 32.26 15.36 b1 B1 240 2.46%14.0 14.0 11.6 0 N/A Valley Pan 0.015 6.00 10.25 N/A N/A 0.00 11.33 13.99 11.33 13.99 11.33 11.59 11.33 b2 B2 60 5.00%2.4 2.4 0.8 87 1.03%Valley Pan 0.015 6.00 10.25 0.59 0.71 2.05 10.82 4.48 5.00 4.48 5.00 2.90 5.00 b3 B3 130 2.46%5.0 5.0 1.9 610 0.79%Valley Pan 0.015 6.00 10.25 0.59 0.62 16.49 14.11 21.49 14.11 21.49 14.11 18.40 14.11 b4 B4 40 2.00%2.0 2.0 0.9 162 0.68%Valley Pan 0.015 6.00 10.25 0.59 0.57 4.71 11.12 6.73 6.73 6.73 6.73 5.65 5.65 b5 B5 50 2.80%4.4 4.4 2.9 51 1.06%Swale (8:1)0.038 8.00 16.12 0.50 0.26 3.32 10.56 7.72 7.72 7.72 7.72 6.24 6.24 b6 B6 96 2.29%3.5 3.5 1.4 227 0.97%Valley Pan 0.015 6.00 10.25 0.59 0.68 5.53 11.79 9.06 9.06 9.06 9.06 6.92 6.92 b7 B7 40 3.00%3.9 3.9 2.6 291 0.69%Valley Pan 0.015 6.00 10.25 0.59 0.58 8.42 11.84 12.32 11.84 12.32 11.84 11.04 11.04 c1 C1 13 12.85%2.6 2.6 2.4 190 0.87%Swale (8:1)0.038 8.00 16.12 0.50 0.23 13.60 11.13 16.19 11.13 16.19 11.13 16.05 11.13 c2 C2 40 6.33%3.2 3.2 2.2 0 N/A Valley Pan 0.015 6.00 10.25 N/A N/A 0.00 10.22 3.19 5.00 3.19 5.00 2.22 5.00 d1 D1 40 15.03%4.1 4.1 3.8 200 0.51%Valley Pan 0.015 6.00 10.25 0.59 0.50 6.72 11.33 10.81 10.81 10.81 10.81 10.51 10.51 d2 D2 100 1.42%15.0 15.0 14.1 0 N/A Valley Pan 0.015 6.00 10.25 N/A N/A 0.00 10.56 14.97 10.56 14.97 10.56 14.14 10.56 d3 D3 40 2.57%2.2 2.2 0.9 60 0.50%Gutter 0.015 3.61 19.18 0.19 0.23 4.33 10.56 6.54 6.54 6.54 6.54 5.20 5.20 d4 D4 82 1.87%2.6 2.6 1.4 185 0.50%Gutter 0.015 3.61 19.18 0.19 0.23 13.33 11.48 15.89 11.48 15.89 11.48 14.70 11.48 d5 D5 40 1.00%3.2 3.2 1.2 277 0.96%Gutter 0.015 3.61 19.18 0.19 0.32 14.46 11.76 17.70 11.76 17.70 11.76 15.65 11.76 d6 D6 40 2.35%3.9 3.9 2.4 25 0.68%Valley Pan 0.015 6.00 10.25 0.59 0.57 0.73 10.36 4.59 5.00 4.59 5.00 3.10 5.00 d7 D7 40 3.18%4.1 4.1 2.9 280 0.64%Valley Pan 0.015 6.00 10.25 0.59 0.56 8.40 11.78 12.46 11.78 12.46 11.78 11.26 11.26 e1 E1 65 9.00%6.0 6.0 5.6 1272 0.65%Floodplain 0.056 46.50 23.32 1.99 0.34 62.65 17.43 68.69 17.43 68.69 17.43 68.21 17.43 e2 E2 40 16.30%3.8 3.8 3.5 735 0.46%Floodplain 0.044 18.00 13.00 1.38 0.29 42.51 14.31 46.34 14.31 46.34 14.31 46.01 14.31 f1 F1 22 2.18%2.9 2.9 1.8 175 0.57%Gutter 0.015 3.61 19.18 0.19 0.25 11.88 11.09 14.77 11.09 14.77 11.09 13.64 11.09 f2 F2 40 1.88%4.8 4.8 3.4 570 0.47%Gutter 0.015 3.61 19.18 0.19 0.22 42.29 13.39 47.09 13.39 47.09 13.39 45.65 13.39 os1 OS1 30 3.53%1.8 1.8 0.7 420 1.08%Gutter 0.015 3.61 19.18 0.19 0.34 20.68 12.50 22.49 12.50 22.49 12.50 21.35 12.50 os2 OS2 26 5.58%1.0 1.0 0.5 1738 1.02%Gutter 0.015 3.61 19.18 0.19 0.33 87.80 19.80 88.82 19.80 88.82 19.80 88.34 19.80 os3 OS3 18 2.06%1.1 1.1 0.6 615 1.38%Gutter 0.015 3.61 19.18 0.19 0.38 26.78 13.52 27.88 13.52 27.88 13.52 27.40 13.52 total Total 40 2.35%-10.2 -10.2 0.9 25 0.68%Valley Pan 0.015 6.00 10.25 0.59 0.57 0.73 10.36 -9.50 5.00 -9.50 5.00 1.62 5.00 March 1, 2021 Combined Basins Design Point Basin Overland Flow Channelized Flow Time of Concentration DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Overland Flow, Time of Concentration: Calculations By: The Quarry by Watermark M. Ruebel Maximum Tc: Channelized Flow, Velocity:Channelized Flow, Time of Concentration: (Equation 3.3-2 per Fort Collins Stormwater Manual) =1.87 1.1 − ∗ =1.49 ∗ /∗(Equation 5-4 per Fort Collins Stormwater Manual) =180 + 10 (Equation 3.3-5 per Fort Collins Stormwater Manual) =∗ 60 (Equation 5-5 per Fort Collins Stormwater Manual) Notes: 1) Add 5000 to all elevations. 2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min. 3) Assume a water depth of 6" and a typical curb and gutter per Larimer County Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a water depth of 1', fixed side slopes, and a triangular swale section for grass Page 2 of 11 Tc2Tc10Tc100C2C10C100I2(in/hr)I10(in/hr)I100(in/hr)Q2(cfs)Q10(cfs)Q100(cfs)a1A11.32212.9012.9012.760.230.230.282.023.457.040.61.02.6a2A21.75015.3615.3615.360.780.780.971.873.196.522.64.411.1b1B10.61211.3311.3311.330.450.450.562.133.637.420.61.02.5b2B20.5365.005.005.000.810.811.002.854.879.951.22.15.3b3B33.48414.1114.1114.110.780.780.981.923.296.715.29.022.9b4B40.2886.736.735.650.880.881.002.604.449.630.71.12.8b5B50.4807.727.726.240.630.630.792.464.219.310.71.33.5b6B61.1479.069.066.920.850.851.002.303.939.062.23.810.4b7B70.49111.8411.8411.040.620.620.782.093.577.420.61.12.8c1C10.10611.1311.1311.130.200.200.252.133.637.420.00.10.2c2C20.1625.005.005.000.600.600.752.854.879.950.30.51.2d1D10.97910.8110.8110.510.250.250.312.173.717.570.50.92.3d2D20.21910.5610.5610.560.200.200.252.173.717.570.10.20.4d3D30.2146.546.545.200.840.841.002.604.449.950.50.82.1d4D40.76811.4811.4811.480.910.911.002.133.637.421.52.55.7d5D51.16111.7611.7611.760.830.831.002.093.577.292.03.48.5d6D60.0685.005.005.000.670.670.832.854.879.950.10.20.6d7D70.63911.7811.7811.260.600.600.742.093.577.420.81.43.5e1E13.38417.4317.4317.430.270.270.331.752.996.101.62.76.9e2E21.38414.3114.3114.310.280.280.351.923.296.710.71.33.2f1F10.04511.0911.0911.090.670.670.842.133.637.420.10.10.3f2F20.17713.3913.3913.390.600.600.751.983.396.920.20.40.9os1OS10.48412.5012.5012.500.830.831.002.023.457.040.81.43.4os2OS21.80019.8019.8019.800.910.911.001.632.785.682.74.610.2os3OS30.87313.5213.5213.520.920.921.001.953.346.821.62.75.9totalTotal19.4155.005.005.002.252.251.002.854.879.95124.5212.7193.2DEVELOPED DIRECT RUNOFF COMPUTATIONSIntensity FlowThe Quarry by WatermarkM. RuebelMarch 1, 2021Project:Calculations By:Date:Rational Equation: Q = CiA (Equation 6-1 per MHFD)DesignPointBasinArea(acres)Runoff CIntensity, I from Fig. 3.4.1 Fort Collins Stormwater ManualTc (Min)Combined BasinsPage 3 of 11 Project Number:Project: Project Location: Calculations By:Date: Sq. Ft. Acres A1 57,578 1.32 5%n/a n/a 0 3,033 A2 76,238 1.75 77%Stormtech 1 Stormtech 2,448 58,703 B1 26,648 0.61 32% Rain Garden A Rain Garden 6,745 8,513 B2 23,356 0.54 79% Rain Garden A Rain Garden 6,745 18,355 B3 151,782 3.48 76% Rain Garden A Rain Garden 6,745 115,150 B4 12,548 0.29 91% Rain Garden A Rain Garden 6,745 11,386 B5 20,910 0.48 53% Rain Garden A Rain Garden 6,745 11,008 B6 49,947 1.15 84% Rain Garden A Rain Garden 6,745 41,739 B7 21,377 0.49 53% Rain Garden A Rain Garden 6,745 11,236 C1 4,634 0.11 2% n/a n/a 0 93 C2 7,076 0.16 50% n/a n/a 0 3,507 D1 42,626 0.98 8% n/a n/a 0 3,414 D2 9,531 0.22 2% n/a n/a 0 191 D3 9,336 0.21 82% n/a n/a 0 7,693 D4 33,439 0.77 93% n/a n/a 0 31,265 D5 50,568 1.16 81% Stormtech 2 Stormtech 2,616 41,113 D6 2,943 0.07 58% Stormtech 2 Stormtech 2,616 1,708 D7 27,830 0.64 49% Stormtech 2 Stormtech 2,616 13,767 F1 1,947 0.04 64% n/a n/a 0 1,241 F2 7,690 0.18 54% n/a n/a 0 4,174 Total 638,004 13.32 387,288 Project Number:Project: Project Location: Calculations By:Date: Sq. Ft. Acres Rain Garden A 306,568 7.04 71% B1-7 Rain Garden 5,621 6,745 217,387 Stormtech 1 76,238 1.75 77% A2 Stormtech 2,040 2,448 58,703 Stormtech 2 81,341 1.87 70% D5,6,7 Stormtech 2,180 2,616 56,587 Total 464,147 10.66 11,809 332,677 638,004 ft2 387,288 ft2 54,610 ft2 290,466 ft3 332,677 ft2 85.90% Total Treated Area Percent Impervious Treated by LID A1,C,D1-4,E,F 75% Requried Minium Area to be Treated LID Site Summary - New Impervious Area Total Area of Current Development Total Impervious Area Total Impervious Area without LID Treatment Subbasin ID Treatment TypeLID ID Volume per UD-BMP (ft3) Area Weighted % Impervious 1079-001 The Quarry Fort Collins, Colorado M. Ruebel 2/28/2021 LID Summary LID Summary per LID Structure Impervious Area (ft2) Vol. w/20% Increase per Fort Collins Manual (ft3) LID Summary AreaBasin ID Treatment TypePercent Impervious LID ID The Quarry 2/28/2021 1079-001 Fort Collins, Colorado M. Ruebel Total Impervious Area (ft2) Required Volume (ft3) LID Summary per Basin Project Title Date: Project Number Calcs By: Client Basins 0.8 WQCV = Watershed inches of Runoff (inches)90% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100)0.321 in A =1.75 ac V = 0.0468 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) The Quarry March 3, 2021 1791-001 M. Ruebel Basin A2 2040 cu. ft. Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event 0.231 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 00.10.20.30.40.50.60.70.80.91WQCV (watershed inches)Total Imperviousness Ratio (i = Iwq/100) Water Quality Capture Volume 6 hr 12 hr 24 hr 40 hr ()iii78.019.10.91aWQCV 23 +-= ()iii78.019.10.91aWQCV 23 +-= AV* 12 WQCV   = 12 hr Project Title Date: Project Number Calcs By: Client Basins 0.8 WQCV = Watershed inches of Runoff (inches)90% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100)0.321 in A =1.87 ac V = 0.0501 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 2180 cu. ft. Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event The Quarry March 3, 2021 1791-001 M. Ruebel Basin D5,6,7 0.231 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 00.10.20.30.40.50.60.70.80.91WQCV (watershed inches)Total Imperviousness Ratio (i = Iwq/100) Water Quality Capture Volume 6 hr 12 hr 24 hr 40 hr ()iii78.019.10.91aWQCV 23 +-= ()iii78.019.10.91aWQCV 23 +-= AV* 12 WQCV   = 12 hr Vault ID Total Required WQ Volume (cf) Flow, WQ (cfs) Chamber Type Chamber Release Ratea (cfs) Chamber Volumeb (cf) Installed Camber w/ Aggregatec (cf) Mimimum No. of Chambersd Total Release Ratee (cfs) Required Storage Volume by FAA Method (cf) Mimimum No. of Chambersf Storage Provided within the Chambersg (cf) Total Installed System Volumeh (cf) Storm Chamber 1 2040 0.01 SC-740 0.024 45.90 74.90 28 0.66 0 0 1285 2097 Storm Chamber 2 2180 0.02 SC-740 0.024 45.90 74.90 30 0.71 0 0 1377 2247 SC-740 *No Detention provided in chambers a. Release rate per chamber, limited by flow through geotextile with accumulated sediment. b. Volume within chamber only, not accounting for void spaces in surrounding aggregate. c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit. d. Number of chambers required to provide full WQCV within total installed system, including aggregate. e. Release rate per chamber times number of chambers. f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage). g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume. h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV. Chamber Configuration Summary P:\1791-001\Drainage\LID\1791-001 Chamber Summary Chamber Dimensions SC-160 SC-310 SC-740 MC-3500 MC-4500 Width (in) 34.0 34.0 51.0 77.0 100.0 Length (in)85.4 85.4 85.4 90.0 52.0 Height (in)16.0 16.0 30.0 45.0 60.0 Floor Area (sf)20.2 20.2 30.2 48.1 36.1 Chamber Volume (cf)6.9 14.7 45.9 109.9 106.5 Chamber/Aggregate Volume (cf)29.3 29.3 74.9 175.0 162.6 Flow Rate* 0.35 gpm/sf 1 cf =7.48052 gal 1 gallon =0.133681 cf 1 GPM = 0.002228 cfs *Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report SC-160 SC-310 SC-740 MC-3500 MC-4500 Flow Rate/chamber (cfs)0.015724 0.015724 0.023586 0.037528 0.028159 end caps have a volume of 108.7 cu. ft. StormTech Chamber Data Chamber Flow Rate Chamber Flow Rate Conversion (gpm/sf to cfs) end caps have a volume of 45.1 cu. ft. P:\1791-001\Drainage\LID\1791-001 Chamber Summary UDCABLEF.O. T MHTTTSS S D F.O. D MH MM MH / / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / /STSTSSSSSBBBBBBBB BB BB B B BBB BB BBBBBBBBBBBBBBBBBBBB B BB B BBB B BBB BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBXXTRACT B DETENTION POND 2 d7 d1 a1 b1 b2 b4 b5b6 b7 b3 c1 d2 os2 os3 e1 e2 os1 c2 S SHIELDS ST.HOBBIT ST.WALLENBERG DR . SPRI N G C R E E K CANAL IMPORTATIONMCCOY JOHN H/SHERRY P 1900 S SHIELDS ST HILL POND CONDOMINIUMS f2 f1 DETENTION POND 1 d4 d3 d5 d6 1.32 ac. A1 0.98 ac. D1 0.22 ac. D2 0.61 ac. B1 1.75 ac. A2 0.54 ac. B2 0.64 ac. D7 1.15 ac. B6 0.48 ac. B5 0.29 ac. B4 3.48 ac. B3 0.11 ac. C1 0.16 ac. C20.49 ac. B7 0.47 ac. OS3 3.38 ac. E1 1.38 ac. E2 0.48 ac. OS1 1.80 ac. OS2 0.18 ac. F2 0.05 ac. F1 1.16 ac. D5 0.21 ac. D3 0.77 ac. D4 0.07 ac. D6 TRACT A RAIN GARDEN A a2 PROPOSED STORMTECH CHAMBERS 2 PROPOSED STORMTECH CHAMBERS 1 PROPOSED STORM SEWER PROPOSED CURB & GUTTER PROPERTY BOUNDARY PROPOSED INLET ADESIGN POINT DRAINAGE BASIN LABEL DRAINAGE BASIN BOUNDARY A LEGEND: FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION DRAWN BY: SCALE: ISSUED: THE QUARRY BY WATERMARK SHEET NO: FORT COLLINS: 301 North Howes Street, Suite 100, 80521 GREELEY: 820 8th Street, 80631 E N G I N E E R N GI EHTRON R N 970.221.4158 northernengineering.com P:\1791-001\DWG\DRNG\1791-001_LID.DWGLID EXHIBIT M. Ruebel 1in=150ft 3.1.2021 ( IN FEET ) 1 inch = ft. Feet0150150 150 RAID GARDEN LIMITS STORMTECH CHAMBERS LID Summary per LID Structure LID ID Area Weighted % Impervious Subbasin ID Treatment Type Volume per UD-BMP (ft3) Vol. w/20% Increase per Fort Collins Manual (ft3) Impervious Area (ft2) Sq. Ft.Acres Rain Garden A 306,568 7.04 71%B1-7 Rain Garden 5,621 6,745 217,387 Stormtech 1 76,238 1.75 77%A2 Stormtech 2,040 2,448 58,703 Stormtech 2 81,341 1.87 70%D5,6,7 Stormtech 2,180 2,616 56,587 Total 464,147 10.66 11,809 332,677 LID Site Summary - New Impervious Area Total Area of Current Development 638,004 ft2 Total Impervious Area 387,288 ft2 Total Impervious Area without LID Treatment 54,610 ft2 A1,C,D1-4,E,F 75% Requried Minium Area to be Treated 290,466 Total Treated Area 332,677 ft2 Percent Impervious Treated by LID 85.90% NORTHERNENGINEERING.COM | 970.221.4158 FINAL DRAINAGE REPORT: THORNBURG HAMILTON FIFTH SUBDIVISION FORT COLLINS | GREELEY APPENDIX APPENDIX D DETENTION POND & SWMM 1S 1S B2B2B1B1 B1B1B B B B B B B B B BBBBBB B BB B B B B B B B B B B B B B B B B B B B B B BBBB B B B B B B B B B B B B B B B B B B B B B B B BB B B B B B B B B B B B B BB B B B B B B B B B B B B B B B B B BBB B BB B B B BBB B B B B B B B B BB B B B B BB B B B B UD SM1 SM2 SM2 SM1 POND 1 POND 2 S. SHIELDS ST. SWMM EXHIBIT FORT COLLINS, CO THE QUARRY BY WATERMARK E N G I N E E R N GI EHTRON R N 03.02.21 P:\1791-001\DWG\DRNG\1791-001_SWMM.DWG Project: 1791-001 By: ATC Date: 03/01/21 Pond ID 100-Yr. Detention Vol. (Ac-Ft) Peak Release (cfs) Pond 1 1.99 5.10 Pond 2 0.89 5.60 POND SUMMARY TABLE Pond Stage-Storage Curve Pond: 1 Project: 1791-001 By: ATC Date: 3/1/21 Stage (FT) Contour Area (SF) Volume (CU.FT.) Volume (AC-FT) 5006.80 2.47 0.00 0.00 5007.00 540.42 38.63 0.00 5007.20 1682.33 250.38 0.01 5007.40 3357.73 744.83 0.02 5007.60 5668.22 1637.40 0.04 5007.80 8663.48 3060.02 0.07 5008.00 12229.92 5139.14 0.12 5008.20 15000.13 7857.43 0.18 5008.40 17067.89 11062.01 0.25 5008.60 18482.35 14616.10 0.34 5008.80 19183.36 18382.45 0.42 5009.00 19807.07 22281.33 0.51 5009.20 20413.20 26303.20 0.60 5009.40 20996.32 30444.02 0.70 5009.60 21565.35 34700.06 0.80 5009.80 22114.54 39067.93 0.90 5010.00 22630.95 43542.38 1.00 5010.20 23367.81 48142.06 1.11 5010.40 24489.98 52927.40 1.22 5010.60 25657.31 57941.67 1.33 5010.80 26634.08 63170.51 1.45 5011.00 27443.71 68578.09 1.57 5011.20 27992.41 74121.61 1.70 5011.40 28545.43 79775.30 1.83 5011.60 29101.90 85539.94 1.96 5011.80 29662.54 91416.30 2.10 Pond Stage-Storage Curve Pond: 2 Project: 1791-001 By: ATC Date: 3/1/21 Stage (FT) Contour Area (SF) Volume (CU.FT.) Volume (AC-FT) 5011.00 13.48 0.00 0.00 5011.20 266.06 22.63 0.00 5011.40 722.70 117.78 0.00 5011.60 1641.13 347.97 0.01 5011.80 2919.21 797.91 0.02 5012.00 4473.39 1531.67 0.04 5012.20 5816.26 2557.70 0.06 5012.40 6984.68 3836.01 0.09 5012.60 8060.75 5339.27 0.12 5012.80 9055.19 7049.90 0.16 5013.00 10006.64 8955.29 0.21 5013.20 10893.75 11044.70 0.25 5013.40 11658.44 13299.48 0.31 5013.60 12380.18 15702.99 0.36 5013.80 13121.41 18252.79 0.42 5014.00 13883.39 20952.91 0.48 5014.20 14668.97 23807.78 0.55 5014.40 15484.34 26822.75 0.62 5014.60 16402.04 30010.94 0.69 5014.80 17338.60 33384.57 0.77 5015.00 18403.47 36958.20 0.85 5015.20 20897.84 40885.74 0.94 5015.40 23715.17 45344.08 1.04