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STANFORD SENIOR LIVING - PDP200022 - DOCUMENT MARKUPS - ROUND 2 - DRAINAGE REPORT
PRLIMINARY DRAINAGE REPORT STANFORD SENIOR LIVING Fort Collins, Colorado December 23, 2020 Prepared for: United Properties 1331 17th Street Denver, CO 80202 Prepared by: 301 North Howes Street, Suite 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 Fax: 970.221.4159 www.northernengineering.com Project Number: 1530-002 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 absolutely necessary, we recommend double-sided printing. December 23, 2020 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Preliminary Drainage Report for Stanford Senior Living Dear Staff: Northern Engineering is pleased to submit this Preliminary Drainage Report for your review. This report accompanies the Preliminary Development Review submittal for the proposed Stanford Senior Living. This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM) and Urban Storm Drainage Criteria Manual. This report serves to document the stormwater impacts associated with the proposed Stanford Senior Living project. We understand that review by the City 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. Blaine Mathisen, EI Stephanie Thomas, PE Project Engineer Project Manager Stanford Senior Living Final Drainage Report TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1 A. Location ............................................................................................................................................. 1 B. Description of Property ..................................................................................................................... 2 C. Floodplain.......................................................................................................................................... 3 II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4 A. Major Basin Description .................................................................................................................... 4 B. Sub-Basin Description ....................................................................................................................... 4 III. DRAINAGE DESIGN CRITERIA ................................................................................... 5 A. Regulations........................................................................................................................................ 5 B. Four Step Process .............................................................................................................................. 5 C. Development Criteria Reference and Constraints ............................................................................ 6 D. Hydrological Criteria ......................................................................................................................... 6 E. Hydraulic Criteria .............................................................................................................................. 7 F. Floodplain Regulations Compliance .................................................................................................. 7 G. Modifications of Criteria ................................................................................................................... 7 IV. DRAINAGE FACILITY DESIGN .................................................................................... 7 A. General Concept ............................................................................................................................... 7 B. Specific Details .................................................................................................................................. 9 V. CONCLUSIONS ...................................................................................................... 10 A. Compliance with Standards ............................................................................................................ 10 B. Drainage Concept ............................................................................................................................ 10 References ....................................................................................................................... 11 APPENDICES: APPENDIX A – Hydrologic Computations APPENDIX B – Hydraulic Computations B.1 – Storm Sewers (For Future Use) B.2 – Inlets (For Future Use) B.3 – Detention Facilities APPENDIX C – Water Quality Design Computations APPENDIX D – Erosion Control Report APPENDIX E – Additional References Stanford Senior Living Final Drainage Report LIST OF TABLES AND FIGURES: Figure 1 - Vicinity Map ........................................................................................................ 1 Figure 2 – Aerial Photograph ................................................................................................ 3 Figure 3 – Existing FEMA Floodplains .................................................................................... 3 Figure 4 – Existing City Floodplains ....................................................................................... 4 Table 1 - Pond Summary ................................................................................................... 10 Table 2 - Chamber Count Summary ..................................................................................... 10 MAP POCKET: Existing Drainage Exhibit DR1 - Drainage Exhibit Stanford Senior Living Preliminary Drainage Report 1 I. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map Figure 1 - Vicinity Map 2. Stanford Senior Living project is located in the southwest quarter of Section 25, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. 3. The project site is located at the southwest corner of the Stanford Road and Monroe Drive intersection. 4. Currently the site is vacant on the north side of the lot with native grasses and patches of gravel. The south half of the project site is currently an asphalt parking lot with landscaped medians that the Marriot Hotel is currently utilizing for guest parking. The undeveloped portion of the site drains via overland flow at an average grade of 3.50% to the south towards the existing parking lot. In general, the site conveys stormwater runoff from the north to the south where it is collected by a customized inlet in the southeast corner of the existing parking lot. 5. In the existing condition most of the site is being captured by a custom inlet in the southeast corner of the parking lot that was designed per Strachan Subdivision 3rd Filing. A small portion of the existing drive entrance aisle is being conveyed via curb and gutter to existing inlets at the northwest corner of the Stanford rOAD and Horsetooth Road intersection. Both the custom inlet in the parking lot and inlets at Stanford Senior Living Preliminary Drainage Report 2 the intersection tie into existing 30”x36” HERCP pipes. From there the runoff is routed via the HERCP pipes into Warren Lake which is located at the southeast corner of the Stanford Road and Horsetooth Road intersection. 6. “Stanford Senior Living is in the Foothills Drainage Basin Master Plan that was prepared by Resource Consultants, Inc. and dated July 1980. The Strachan Subdivision Third Filing was developed in 1980 and was divided into two basins. The Southerly Basin, which contains 17.9 acres and drains to the corner of Horsetooth Road and Stanford Road. Mitchell and Co. were the developers, and they paid the Warren Lake Company for storm water detention rights in Warren Lake for Strachan Subdivision 1st, 2nd, and 3rd Filings. These filings correspond to the area between Monroe Drive and Horsetooth Road and between College Avenue and Stanford Road. They also developed the Strachan Continental Subdivision at the southwest corner of Horsetooth Road and J.F.K Parkway. Its detention was also paid for in Warren Lake.” – Final Drainage Report for J.F.K. Office P.U.D 7. According to the Final Drainage Report for J.F.K. Office P.U.D the HERCP pipes in the southeast corner of the parking lot were sized to carry the 10-year event (48 cfs) for the Strachan Subdivision while the 100-year event overtopped Horsetooth Road and sheet flowed to Warren Lake. Due to the report being 40 years old it is important that the Stanford Senior Living project does not adversely impact downstream infrastructure but is still allowed to utilize the Warren Lake Company agreement to some degree. Therefore, the Stanford Senior Living project will detain the difference between the historic 10-year runoff and the proposed 100-year runoff. This will ensure that the downstream infrastructure remains functional while also reducing the runoff that was supposed to overtop Horsetooth Road during the major event. B. Description of Property 1. The Stanford Senior Living project has a total acreage of 3.28 acres. However, the Stanford Senior Living project only plans on developing 2.33 acres and leaving the existing parking lot in place. The existing parking lot historically sheet flows to the southeast to the custom inlet box as previously described. Therefore, Stanford Senior Living will only be detaining and treating 2.33 acres. Stanford Senior Living Preliminary Drainage Report 3 Figure 2 – Aerial Photograph 2. The Stanford Senior Living project will consist of a new assisted living and memory care center. It will be a four-story building with underground parking. There is an existing parking lot that is currently being used by the Marriot Hotel for guest parking which will now serve as the Stanford Senior Living parking lot. 3. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Nunn clay loam, which fails into Hydrologic Soil Group C 4. No irrigation facilities or major drainageways are within the property limits. 5. The project site is within a General Commercial District (C-G) Zoning District. The proposed use is permitted within the zone district. C. Floodplain 1. The subject property is not located in a FEMA or City regulatory floodplain. 2. The FEMA Panel 08069C0987G illustrates that this project site is not near any FEMA delineated regulatory floodplain. Figure 3 – Existing FEMA Floodplains Stanford Senior Living Preliminary Drainage Report 4 Figure 4 – Existing City Floodplains II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description 1. The Stanford Senior Living project is in the Foothills Basin which is centrally located in Fort Collins. The basin is mostly developed with commercial development along College Avenue and mixed-use residential in the remainder of the basin. The basin drains from west to east through open channels or a storm sewer system to the Fossil Creek Reservoir. B. Sub-Basin Description 1. The property historically drains from the northwest to the southeast corner of the existing parking lot via overland flow. The existing parking lot was developed as a part of the Strachan Subdivision 3rd Filing and is currently being used by the Marriot Hotel and Merrill Lynch Wealth Management. As previously described, there is a custom inlet in the southeast corner of the parking lot that has three 30”x36” HERCP that currently routes the 10-year storm event east across Stanford Road to a junction box that then routes the runoff south across Horsetooth Road where it is ultimately discharged into Warren Lake. The 100-year event has historically overtopped Horsetooth Road and overland flowed south to Warren Lake. There are two on-grade inlets at the northwest corner of the intersection of Horsetooth Road and Stanford Road that collects additional flows. These additional flows are then routed to the existing 30”x36” HERCP pipes crossing Stanford Road. Stanford Senior Living Preliminary Drainage Report 5 2. A historic rational calculation was performed for the 2.33 acres of the 3.79 acres that are being platted for the Stanford Senior Living project. According the FCSCM Chapter 6 developments are only responsible for detaining any newly installed impervious areas. Since the parking lot is existing, and downstream of the new development, the Stanford Senior Living project will not be detaining or treating any runoff that has historically drained to the custom inlet at the southeast corner of the parking lot. Additionally, the Stanford Senior Living project is maintaining the existing drainage patterns within Stanford Road and Monroe Drive. Therefore, no runoff generated on the adjacent streets will be routed through the proposed detention and water quality facility. 3. Following FCSCM requirements for rational calculations the 10-year runoff generated by the existing 2.33 acres is 2.33 cfs. Therefore, Stanford Senior Living can have a max release rate of 2.33 cfs. Traditionally, Fort Collins requires the 2-year event dictate the max release rate but since there is a historic agreement in place with Warren Lake Company to detain all runoff from Strachan Subdivision Third Filing this new development can release at a higher release rate than current FCSCM requirements. By releasing at the historic 10-year event it ensures that downstream infrastructure is not adversely impacted while also allowing the developers to use their agreement with Warren Lake Company to some extent. See Section IV.A.4 below for a more detailed description of the project’s proposed drainage patterns. 4. No offsite drainage is being routed through the property. 5. Please refer to the Appendix for additional information about the existing conditions. III. DRAINAGE DESIGN CRITERIA A. Regulations There are optional provisions outside of the FCSCM proposed with the Stanford Senior Living project. Stanford Senior Living project will be detaining the difference between the existing 10-year event and proposed 100-year event. This deviates from the standard existing 2-year and proposed 100-year difference for detention requirements set forth in the FCSCM. B. Four Step Process The overall stormwater management strategy employed with Stanford Senior Living project 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 Several techniques have been utilized with the proposed development to facilitate the reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the current use by implementing multiple Low-Impact Development (LID) strategies including: Providing vegetated open areas along the north, south, east and west portion of the site to reduce the overall impervious area and to minimize directly connected impervious areas (MDCIA). Routing runoff through the drain rock within the underground detention facility to increase time of concentration, promote infiltration and provide water quality. Stanford Senior Living Preliminary Drainage Report 6 Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release The efforts taken in Step 1 will facilitate the reduction of runoff and provide the necessary BMPs required for water quality. All runoff that is captured on site will be routed through isolator rows within Stormtech chambers. The isolator rows will remove sediment and other pollutants through infiltration. Step 3 – Stabilize Drainageways As stated in Section I.B.4, above, there are no major drainageways in or near the subject site. While this step may not seem applicable to Stanford Senior Living, the proposed project indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection has a positive effect on stream stabilization. By detaining the difference between the 10-year and 100-year events there will be less stress on the downstream infrastructure. Combining detention with LID it reduces the likelihood of bed and bank erosion within Warren Lake. 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 and is not necessarily applicable for this project. However, a localized trash collection system that is stored internally to the building will reduce the potential impacts of garbage making its way downstream. C. Development Criteria Reference and Constraints 1. There are existing drainage studies for this area. They were completed as part of the Strachan Continental Subdivision as well as the J.F.K Office P.U.D. These reports can be found in the Appendix and serve as the basis for the 10-year release rate. 2. The subject property is an "in-fill" development project as the property is surrounded by currently developed properties. As such, several constraints have been identified during the course of this analysis that will impact the proposed drainage system including: Existing elevations along the northern and eastern right-of-way lines make it difficult to capture all the flow along these edges. However, it should be noted that the areas that are freely discharging to either Monroe Drive or Stanford Road are associated with the vegetated parkways. Therefore, runoff impacts are minor, and it still maintains the existing conveyance path for these areas. As previously mentioned, overall drainage patterns within the Master Drainage Plan for Strachan Continental Subdivision will be maintained to some degree. There are issues with the Strachan Continental master plan as it is no longer compliant with code. However, at the time of this report there are no known issues with this existing master drainage plan. The city has not identified the intersection of Horsetooth Road and Stanford Road as a problem intersection and there is no future plans to revitalize this intersection. D. Hydrological Criteria 1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations associated with this development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. Stanford Senior Living Preliminary Drainage Report 7 2. The Rational Method has been employed to compute stormwater runoff utilizing coefficients contained in Tables RO-11 and RO-12 of the FCSCM. 3. The Rational Formula-based Modified Federal Aviation Administration (FAA) procedure has been utilized for detention storage calculations. 4. Three 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. The third storm computed, for detention requirements, is the 10-year recurrence interval. 5. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. E. Hydraulic Criteria 1. As previously noted, the subject property historically drains into the custom inlet at the southeast corner of the existing parking lot. From there, the runoff is routed via a series of elliptical pipes to Warren Lake where it has been historically detained and treated for water quality. 2. All drainage facilities proposed with Stanford Senior Living project are designed in accordance with criteria outlined in the FCSCM and/or the Mile High Flood Control District’s Urban Storm Drainage Criteria Manual. 3. As stated in Section I.C.1, above, the subject property is not located within any regulatory floodplain. 4. Stanford Senior Living project does not propose to modify any natural drainageways. F. Floodplain Regulations Compliance 1. As previously mentioned, all structures are located outside of any FEMA 100-year or City floodplain, and thus are not subject to any floodplain regulations. G. Modifications of Criteria 1. The proposed Stanford Senior Living development is requesting a modification at this time. As previously stated, the original Strachan Thrid Filing included this area as part of the agreement with Warren Lake Company to detain and provide water quality treatment for developed stormwater runoff. However, to meet current FCSCM requirements Stanford Senior Living can no longer allow the 100-year event to overtop Horsetooth Road. Therefore, to meet current FCSCM criteria while also utilizing the Warren Lake agreement to the fullest extent possible Stanford Senior Living will be detaining the difference between the existing 10-year event and proposed 100-year event. IV. DRAINAGE FACILITY DESIGN A. General Concept 1. The main objectives of Stanford Senior Living drainage design is to improve the surrounding stormwater infrastructure while also maintain existing drainage patterns. 2. As previously mentioned, there are no off-site flows draining onto the existing property. Stanford Senior Living Preliminary Drainage Report 8 3. 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. 4. The Stanford Senior Living project is composed of five minor drainage basins, designated as Basins A, B, C, D, E, and F. The drainage patterns for each major basin are further described below. Basin A Basin A represents the area in the northwest corner of the site. It consists of a small portion of concrete walk but most of the area is landscaping. Runoff from this basin will enter the storm drain system and be conveyed to the Stormtech chambers. Basin B Basin B encompasses the entire building. Most of the runoff from Basin B will be collected in roof leaders and conveyed to the Stormtech chambers via storm drain. There is also an internal courtyard in the center of the building which will generate a small amount of runoff. Runoff from the courtyard will be collected by area inlets which will convey the stormwater to a storm drain that runs through the building. This run of storm drain will connect to the outside storm drain system where the runoff will then be conveyed to the Stormtech chambers. Basin C Basin C is associated with the memory care garden near the northeast corner of the site. Runoff in Basin C will be collected via area inlets and be routed via storm drain system to the Stormtech chambers. Basin D Basin D consists of a small amount of concrete walk and the rest being landscaping with a swale conveying stormwater runoff to an area drain near the drive entrance to the site. Runoff from Basin D will be conveyed to the Stormtech chambers via a storm drain system. Basin E Basin E shown as the area in front of the building. This area consists of concrete walks, asphalt drive aisles, and landscaped islands. Runoff from Basin E is collected via a series of area drains. Once runoff is collected in the area drains the runoff is routed to the Stormtech chambers via the storm drain system. Basin F Basin F is associated with the drive entrance that will flow east and be captured by an on-grade inlet. Runoff will then be routed to the Stormtech chambers via the storm drain system. A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report. Stanford Senior Living Preliminary Drainage Report 9 B. Specific Details 1. The release rate for the proposed development was established by calculating the 10- year existing runoff rate of the area proposed for development. As mentioned in section III.G this is a modification to the FCSCM. By utilizing the existing 10-year peak runoff the Stanford Senior Living project will maintain downstream infrastructure while also utilizing their agreement with Warren Lake Company to detain this site’s runoff. 2. These release rates were utilized in the FAA method for design of Pond 1. (Refer to Appendix B for these calculations). 3. Detention Pond Calculations Pond 1 Calculations were completed for Pond N1, based on the proposed land use characteristics of Basins A, B, C, D, E, and F with a release rate of 2.33 cfs, indicate a detention volume of 21,513 cu. ft. Based on Stormtech specifications in order to achieve 21,513 cu. ft. of detention it will require 109 MC-3500 chambers. However, based on the Stormtech system layout Stanford Senior Living will be providing 21,619 cu. ft. of detention. 4. Water Quality Pond Calculations Pond 1 The Stanford Senior Living project will be providing 100% of their water quality capture volume in the form of isolator rows within the Stormtech system. Isolator rows qualify as a BMP measure and therefore 100% of the water quality capture volume will be provided in the form of low impact development (LID). Isolator rows are designed to retain sediment and filter out the first flush of any storm event. At the end of each isolator row is a Nyloplast Basin that allows for routine and easy maintenance so that the entire system can be maintained for its design life. Following FCSCM requirements yields a WQCV of 2,584 cu. ft. Utilizing available chamber sizing and infiltration data provided by Stormtech requires 24 additional MC-3500 chambers to meet the required WQCV. However, due to the layout of the Stormtech system at Stanford Senior Living 33 chambers will be apart of the isolator rows. The additional 9 (33-24=9) chambers will still be counted towards the detention requirements. 5. Pond Summary Pond 1 The Stanford Senior Living project will be utilizing 133 MC-3500 Stormtech chambers to fulfill their stormwater detention and treatment requirements. Stanford Senior Living will be providing 100% WQCV using LID measures. Stanford Senior Living Preliminary Drainage Report 10 Table 1 - Pond Summary Table 2 - Chamber Count Summary V. CONCLUSIONS A. Compliance with Standards 1. The drainage design proposed with Stanford Senior Living project complies with the City of Fort Collins’ Stormwater Criteria Manual. 2. The drainage design proposed with Stanford Senior Living project complies with the City of Fort Collins’ Master Drainage Plan for the Foothills Basin. 3. The drainage design proposed with Stanford Senior Living project complies with the Master Drainage Plan for Strachan Continental Subdivision. 4. There are no regulatory floodplains associated with the Stanford Senior Living development. 5. The drainage plan and stormwater management measures proposed with the Stanford Senior Living development are compliant with all applicable State and Federal regulations governing stormwater discharge. B. Drainage Concept 1. The drainage design proposed with this project will effectively limit potential damage associated with its stormwater runoff. The drainage design proposed with this project will be utilizing the agreement with the Warren Lake Company to some extent. 2. The Stanford Senior Living project will detain the difference between the existing 10- year event and the developed 100-year event. 3. The Stanford Senior Living project will be providing 100% WQCV using an LID measure. Reuired Detention (cu. ft.) Provided Detention (cu. ft.) Required WQCV (cu. ft.) Provided WQCV (cu. ft.) Required Total Volume (cu. ft.) Provided Volume (cu. ft.) 21,513 21,619 2,584 2,638 24,097 24,257 Detention WQCV Total 109 24 133 MC-3500 Chamber Counts Stanford Senior Living Preliminary Drainage Report 11 References 1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services. 2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008. 6. Final Drainage Report For J.F.K Office P.U.D, January 9, 1995, Vaught-Frye Architects 7. Strachan Continental Subdivision Storm Drainage Report, July 3, 1981, James H. Stewart & Associates, INC APPENDIX A HYDROLOGIC COMPUTATIONS CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project:Stanford Senior Living Streets, Parking Lots, Roofs, Alleys, and Drives:Calculations By:B. Mathisen Asphalt ……....……………...……….....…...……………….…………………………………..0.95 100%Date: Concrete …….......……………….….……….………………..….…………………………………0.95 90% Gravel ……….…………………….….…………………………..………………………………..0.50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..……………………………………………..0.40 22% Lawns and Landscaping Sandy Soil (1% - 3%) ……..……………..……………….……………………………………………..0.15 2% Clayey Soil (1% - 3%)….….………….…….…………..……………………………………………….0.25 2%2-year Cf = 1.00 100-year Cf = 1.25 Basin ID Basin Area (s.f.) Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Composite % Imperv. EX 101486 2.33 0.154 0.045 0.000 0.083 0.000 2.05 0.32 0.32 0.40 12% EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3.2-2. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 December 18, 2020 **Soil Classification of site is Clay Loam** Page 1 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Existing.xlsx\C-Values Overland Flow, Time of Concentration: Project:Stanford Senior Living Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S½ Velocity (Swale Flow), V = 15·S½ NOTE: Equations from FCSCM Chapter 3 Is Length >500' ? C*Cf (2-yr Cf=1.00) C*Cf (10-yr Cf=1.00) C*Cf (100-yr Cf=1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) ex EX No 0.32 0.32 0.40 285 4.21% 15.3 15.3 13.7 100 5.07% 4.50 0.4 0 N/A N/A N/A 16 16 14 EXISTING TIME OF CONCENTRATION COMPUTATIONS Gutter/Pipe Flow Swale Flow Design Point Basin Overland Flow B. Mathisen December 18, 2020 Time of Concentration (Equation RO-4) () 3 1 *1.187.1 S LCfCTi -= Page 2 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Existing.xlsx\Tc Rational Method Equation:Project:Stanford Senior Living Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: ex EX 2.33 16 16 14 0.32 0.32 0.40 1.84 3.14 6.71 1.37 2.33 6.23 Area, A (acres) Intensity, i2 (in/hr) 100-yr Tc (min) EXISTING RUNOFF COMPUTATIONS C100 Design Point Flow, Q100 (cfs) Flow, Q2 (cfs) 10-yr Tc (min) 2-yr Tc (min) C2 Flow, Q10 (cfs) Intensity, i100 (in/hr) Basin(s) B. Mathisen December 18, 2020 Intensity, i10 (in/hr) Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 C10 ()()()AiCCQf= Page 3 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Existing.xlsx\Direct-Runoff Stanford Senior Living DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q10 (cfs) Q100 (cfs) ex EX 2.33 0.32 0.40 15.6 14.1 1.37 2.33 6.23 Page 4 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Existing.xlsx\SUMMARY-TABLE CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project:Stanford Senior Living Streets, Parking Lots, Roofs, Alleys, and Drives:Calculations By:B. Mathisen Asphalt ……....……………...……….....…...……………….…………………………………..0.95 100%Date: Concrete …….......……………….….……….………………..….…………………………………0.95 90% Gravel ……….…………………….….…………………………..………………………………..0.50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..……………………………………………..0.40 22% Lawns and Landscaping Sandy Soil (1% - 3%) ……..……………..……………….……………………………………………..0.15 2% Clayey Soil (1% - 3%)….….………….…….…………..……………………………………………….0.25 2%2-year Cf = 1.00 100-year Cf = 1.25 Basin ID Basin Area (s.f.) Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Composite % Imperv. A 9532 0.22 0.000 0.057 0.000 0.000 0.000 0.16 0.43 0.43 0.54 25% B 49425 1.13 0.000 0.000 1.135 0.000 0.000 0.00 0.95 0.95 1.00 90% C 10050 0.23 0.000 0.231 0.000 0.000 0.000 0.00 0.95 0.95 1.00 90% D 13643 0.31 0.000 0.049 0.000 0.000 0.000 0.26 0.36 0.36 0.45 16% E 16667 0.38 0.250 0.026 0.000 0.000 0.000 0.11 0.75 0.75 0.94 72% F 2169 0.05 0.033 0.007 0.000 0.000 0.000 0.01 0.80 0.80 1.00 78% TOTAL 101486 2.33 0.283 0.368 1.135 0.000 0.000 0.54 0.79 0.79 0.98 71% DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3.2-2. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 December 18, 2020 **Soil Classification of site is Clay Loam** Page 1 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Proposed.xlsx\C-Values Overland Flow, Time of Concentration: Project:Stanford Senior Living Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S½ Velocity (Swale Flow), V = 15·S½ NOTE: Equations from FCSCM Chapter 3 Is Length >500' ? C*Cf (2-yr Cf=1.00) C*Cf (10-yr Cf=1.00) C*Cf (100-yr Cf=1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) a A Yes 0.43 0.43 0.54 50 6.00% 4.9 4.9 4.1 0 0.00% N/A N/A N/A N/A N/A 5 5 5 b B Yes 0.95 0.95 1.00 0 N/A N/A N/A N/A 0 0.00% N/A N/A N/A N/A N/A 5 5 5 c C Yes 0.95 0.95 1.00 20 2.25% 1.0 1.0 0.6 0 0.00% N/A N/A N/A N/A N/A 5 5 5 d D Yes 0.36 0.36 0.45 10 4.50% 2.7 2.7 2.3 0 0.00% N/A N/A 230 2.00% 2.12 1.8 5 5 5 e E Yes 0.75 0.75 0.94 30 4.20% 2.2 2.2 1.0 20 2.50% 3.16 0.1 N/A N/A N/A 5 5 5 f F Yes 0.80 0.80 1.00 10 2.00% 1.4 1.4 0.5 83 6.02% 4.91 0.3 N/A N/A N/A 5 5 5 TOTAL Yes 0.79 0.79 0.98 50 3.00% 2.9 2.9 1.1 0 0.00% N/A N/A N/A N/A N/A 5 5 5 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter/Pipe Flow Swale Flow Design Point Basin Overland Flow B. Mathisen December 18, 2020 Time of Concentration (Equation RO-4) () 3 1 *1.187.1 S LCfCTi -= Page 2 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Proposed.xlsx\Tc Rational Method Equation:Project:Stanford Senior Living Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: a A 0.22 5 5 5 0.43 0.43 0.54 2.85 4.87 9.95 0.27 0.46 1.17 b B 1.13 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 3.07 5.25 11.29 c C 0.23 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.62 1.07 2.30 d D 0.31 5 5 5 0.36 0.36 0.45 2.85 4.87 9.95 0.32 0.55 1.40 e E 0.38 5 5 5 0.75 0.75 0.94 2.85 4.87 9.95 0.82 1.41 3.59 f F 0.05 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.11 0.19 0.50 TOTAL 2.33 5 5 5 0.79 0.79 0.98 2.85 4.87 9.95 5.22 8.92 22.79 DEVELOPED RUNOFF COMPUTATIONS C100 Design Point Flow, Q100 (cfs) Flow, Q2 (cfs) 10-yr Tc (min) 2-yr Tc (min) C2 Flow, Q10 (cfs) Intensity, i100 (in/hr) Basin(s) B. Mathisen December 18, 2020 Intensity, i10 (in/hr) Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 C10 Area, A (acres) Intensity, i2 (in/hr) 100-yr Tc (min) ()()()AiCCQf= Page 3 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Proposed.xlsx\Direct-Runoff DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) a A 0.22 0.43 0.54 5.0 5.0 0.27 1.17 b B 1.13 0.95 1.00 5.0 5.0 3.07 11.29 c C 0.23 0.95 1.00 5.0 5.0 0.62 2.30 d D 0.31 0.36 0.45 5.0 5.0 0.32 1.40 e E 0.38 0.75 0.94 5.0 5.0 0.82 3.59 f F 0.05 0.80 1.00 5.0 5.0 0.11 0.50 Page 4 of 20 P:\1530-002\Drainage\Hydrology\1530-002_Rational Calcs - Proposed.xlsx\SUMMARY-TABLE FortCollinsFort Collins Rainfall Intensity DataFIG 3-1Intensities (iph)Time 2-yr 10-yr 100-yrminutes 2 3 45.0 2.85 4.87 9.955.5 2.760 4.715 9.6306.0 2.67 4.56 9.316.5 2.595 4.435 9.0557.0 2.52 4.31 8.80ASPH7.5 2.460 4.205 8.590CONC8.0 2.40 4.10 8.38GRAVEL8.5 2.350 4.015 8.205ROOF9.0 2.30 3.93 8.03 9.5 2.255 3.855 7.875FLAWNSS10.0 2.21 3.78 7.72ALAWNSS10.5 2.170 3.705 7.570SLAWNSS11.0 2.13 3.63 7.42 11.5 2.090 3.565 7.290FLAWNHS12.0 2.05 3.50 7.16ALAWNHS12.5 2.015 3.445 7.040SLAWNHS13.0 1.98 3.39 6.9213.5 1.950 3.340 6.81514.0 1.92 3.29 6.7114.5 1.895 3.240 6.61515.0 1.87 3.19 6.5215.5 1.840 3.135 6.41016.0 1.81 3.08 6.3016.5 1.780 3.035 6.20017.0 1.75 2.99 6.1017.5 1.725 2.945 6.01018.0 1.70 2.90 5.9218.5 1.675 2.860 5.83519.0 1.65 2.82 5.7519.5 1.630 2.780 5.67520.0 1.61 2.74 5.6020.5 1.585 2.705 5.53021.0 1.56 2.67 5.4621.5 1.545 2.640 5.39022.0 1.53 2.61 5.3222.5 1.510 2.580 5.26023.0 1.49 2.55 5.2023.5 1.475 2.520 5.14524.0 1.46 2.49 5.0924.5 1.445 2.465 5.03525.0 1.43 2.44 4.9825.5 1.415 2.415 4.92526.0 1.40 2.39 4.8726.5 1.385 2.365 4.82527.0 1.37 2.34 4.7827.5 1.355 2.315 4.73528.0 1.34 2.29 4.6928.5 1.330 2.270 4.64529.0 1.32 2.25 4.6029.5 1.310 2.230 4.56030.0 1.30 2.21 4.5230.5 1.285 2.185 4.470 31.0 1.27 2.16 4.4231.5 1.255 2.140 4.37532.0 1.24 2.12 4.3332.5 1.230 2.100 4.28533.0 1.22 2.08 4.2433.5 1.205 2.060 4.20034.0 1.19 2.04 4.1634.5 1.180 2.020 4.12035.0 1.17 2.00 4.0835.5 1.160 1.980 4.04536.0 1.15 1.96 4.0136.5 1.140 1.945 3.97037.0 1.13 1.93 3.9337.5 1.120 1.910 3.90038.0 1.11 1.89 3.8738.5 1.100 1.875 3.83539.0 1.09 1.86 3.8039.5 1.080 1.845 3.77040.0 1.07 1.83 3.7440.5 1.060 1.815 3.71041.0 1.05 1.80 3.6841.5 1.045 1.785 3.65042.0 1.04 1.77 3.6242.5 1.030 1.755 3.59043.0 1.02 1.74 3.5643.5 1.015 1.730 3.53544.0 1.01 1.72 3.5144.5 1.000 1.705 3.48545.0 0.99 1.69 3.4645.5 0.985 1.680 3.43546.0 0.98 1.67 3.4146.5 0.970 1.655 3.38547.0 0.96 1.64 3.3647.5 0.955 1.630 3.33548.0 0.95 1.62 3.3148.5 0.945 1.610 3.29049.0 0.94 1.60 3.2749.5 0.930 1.590 3.25050.0 0.92 1.58 3.2350.5 0.915 1.570 3.20551.0 0.91 1.56 3.1851.5 0.905 1.550 3.16052.0 0.90 1.54 3.1452.5 0.895 1.530 3.12053.0 0.89 1.52 3.1053.5 0.885 1.510 3.08554.0 0.88 1.50 3.0754.5 0.875 1.490 3.05055.0 0.87 1.48 3.0355.5 0.865 1.475 3.01056.0 0.86 1.47 2.9956.5 0.855 1.460 2.97557.0 0.85 1.45 2.9657.5 0.845 1.440 2.94058.0 0.84 1.43 2.9258.5 0.835 1.425 2.90559.0 0.83 1.42 2.8959.5 0.825 1.410 2.875 60.0 0.82 1.40 2.8660.5 0.815 1.392 2.84661.0 0.810 1.384 2.83261.5 0.805 1.376 2.81862.0 0.800 1.368 2.80462.5 0.795 1.360 2.79063.0 0.790 1.352 2.77663.5 0.785 1.344 2.76264.0 0.780 1.336 2.74864.5 0.775 1.328 2.73465.0 0.77 1.32 2.7265.5 0.766 1.313 2.70766.0 0.762 1.306 2.69466.5 0.758 1.299 2.68167.0 0.754 1.292 2.66867.5 0.750 1.285 2.65568.0 0.746 1.278 2.64268.5 0.742 1.271 2.62969.0 0.738 1.264 2.61669.5 0.734 1.257 2.60370.0 0.73 1.25 2.5970.5 0.726 1.244 2.57971.0 0.722 1.238 2.56871.5 0.718 1.232 2.55772.0 0.714 1.226 2.54672.5 0.710 1.220 2.53573.0 0.706 1.214 2.52473.5 0.702 1.208 2.51374.0 0.698 1.202 2.50274.5 0.694 1.196 2.49175.0 0.69 1.19 2.4875.5 0.687 1.185 2.47076.0 0.684 1.180 2.46076.5 0.681 1.175 2.45077.0 0.678 1.170 2.44077.5 0.675 1.165 2.43078.0 0.672 1.160 2.42078.5 0.669 1.155 2.41079.0 0.666 1.150 2.40079.5 0.663 1.145 2.39080.0 0.66 1.14 2.3880.5 0.657 1.135 2.37181.0 0.654 1.130 2.36281.5 0.651 1.125 2.35382.0 0.648 1.120 2.34482.5 0.645 1.115 2.33583.0 0.642 1.110 2.32683.5 0.639 1.105 2.31784.0 0.636 1.100 2.30884.5 0.633 1.095 2.29985.0 0.63 1.09 2.2985.5 0.628 1.086 2.28286.0 0.626 1.082 2.27486.5 0.624 1.078 2.26687.0 0.622 1.074 2.25887.5 0.620 1.070 2.25088.0 0.618 1.066 2.24288.5 0.616 1.062 2.234 89.0 0.614 1.058 2.22689.5 0.612 1.054 2.21890.0 0.61 1.05 2.2190.5 0.613 1.054 2.21891.0 0.616 1.058 2.22691.5 0.619 1.062 2.23492.0 0.622 1.066 2.24292.5 0.625 1.070 2.25093.0 0.628 1.074 2.25893.5 0.631 1.078 2.26694.0 0.634 1.082 2.27494.5 0.637 1.086 2.28295.0 0.58 1.01 2.1395.5 0.578 1.006 2.12396.0 0.576 1.002 2.11696.5 0.574 0.998 2.10997.0 0.572 0.994 2.10297.5 0.570 0.990 2.09598.0 0.568 0.986 2.08898.5 0.566 0.982 2.08199.0 0.564 0.978 2.07499.5 0.562 0.974 2.067100.0 0.56 0.97 2.06100.5 0.558 0.967 2.054101.0 0.556 0.964 2.048101.5 0.554 0.961 2.042102.0 0.552 0.958 2.036102.5 0.550 0.955 2.030103.0 0.548 0.952 2.024103.5 0.546 0.949 2.018104.0 0.544 0.946 2.012104.5 0.542 0.943 2.006105.0 0.54 0.94 2.00105.5 0.5380 0.9370 1.9940106.0 0.5360 0.9340 1.9880106.5 0.5340 0.9310 1.9820107.0 0.5320 0.9280 1.9760107.5 0.5300 0.9250 1.9700108.0 0.5280 0.9220 1.9640108.5 0.5260 0.9190 1.9580109.0 0.5240 0.9160 1.9520109.5 0.5220 0.9130 1.9460110.0 0.52 0.91 1.94110.5 0.519 0.907 1.935111.0 0.518 0.904 1.930111.5 0.517 0.901 1.925112.0 0.516 0.898 1.920112.5 0.515 0.895 1.915113.0 0.514 0.892 1.910113.5 0.513 0.889 1.905114.0 0.512 0.886 1.900114.5 0.511 0.883 1.895115.0 0.51 0.88 1.89115.5 0.508 0.878 1.885116.0 0.506 0.876 1.880116.5 0.504 0.874 1.875117.0 0.502 0.872 1.870117.5 0.500 0.870 1.865 118.0 0.498 0.868 1.860118.5 0.496 0.866 1.855119.0 0.494 0.864 1.850119.5 0.492 0.862 1.845120.0 0.49 0.86 1.84 Table 3-3 - Fort CollinsRational Method Runoff Coefficientfor Composite AnalysisRunoffSurface CharacteristicsCoef.C2STREETSAsphalt 0.950Concrete 0.950Gravel 0.500Roofs 0.950LAWNS SANDY SOILFlat Sandy Soil Lawns S < 2% 0.100Average Sandy Soil Lawns 2% < S < 7% 0.150Steep Sandy Soil Lawns S> 7% 0.200LAWNS HEAVY SOILFlat Heavy Soil Lawns S< 2% 0.200Average Heavy Soil Lawns 2% < S < 7% 0.250Steep Heavy Soil Lawns S > 7% 0.350 APPENDIX B HYDRAULIC COMPUTATIONS B.1 – Storm Sewers B.2 – Inlets B.3 – Detention Facilities APPENDIX B.1 STORM SEWERS (FOR FUTURE USE) APPENDIX B.2 INLETS (FOR FUTURE USE) APPENDIX B.3 DETENTION FACILITIES Pond No : Pond 1 100-yr 0.98 5.00 min 21513 ft3 2.33 acres 0.494 ac-ft Max Release Rate =2.33 cfs Time (min) Ft Collins 100-yr Intensity (in/hr) Inflow Volume (ft3) Outflow Adjustment Factor Qav (cfs) Outflow Volume (ft3) Storage Volume (ft3) 5 9.950 6816 1.00 2.33 699 6117 10 7.720 10577 0.75 1.75 1049 9528 15 6.520 13399 0.67 1.55 1398 12001 20 5.600 15344 0.63 1.46 1748 13597 25 4.980 17057 0.60 1.40 2097 14960 30 4.520 18578 0.58 1.36 2447 16131 35 4.080 19564 0.57 1.33 2796 16768 40 3.740 20496 0.56 1.31 3146 17350 45 3.460 21332 0.56 1.29 3495 17837 50 3.230 22126 0.55 1.28 3845 18282 55 3.030 22832 0.55 1.27 4194 18638 60 2.860 23510 0.54 1.26 4544 18966 65 2.720 24222 0.54 1.25 4893 19329 70 2.590 24839 0.54 1.25 5243 19596 75 2.480 25483 0.53 1.24 5592 19891 80 2.380 26086 0.53 1.24 5942 20144 85 2.290 26668 0.53 1.23 6291 20377 90 2.210 27250 0.53 1.23 6641 20610 95 2.130 27723 0.53 1.23 6990 20733 100 2.060 28223 0.53 1.22 7340 20883 105 2.000 28771 0.52 1.22 7689 21082 110 1.940 29237 0.52 1.22 8039 21198 115 1.890 29778 0.52 1.22 8388 21390 120 1.840 30250 0.52 1.21 8738 21513 *Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. A = Tc = Project Location : Design Point C = Design Storm DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Input Variables Results Required Detention Volume Fort Collins, Colorado 1530-002 Stanford Senior Living Project Number : Project Name : Pond 1 Page 1 of 1 1530-002_FAAModified Method.xls 12/18/2020 ADS Design Tool Site https://designtool.stormtech.com/index.html 1/1 User Inputs Chamber Model MC-3500 Outlet Control Structure Yes (Outlet) Project Name The Stanford Project Location Fort Collins Project Date 12/02/2020 Engineer Northern Engineering Measurement Type Imperial Required Storage Volume 21513 cubic ft. Stone Porosity 40% Stone Above Chambers 12 in. Stone Foundation Depth 9 in. Average Cover Over Chambers 24 in. Design Constraint Length Design Constraint Dimension 90 ft. Results System Volume and Bed Size Installed Storage Volume 21619 cubic ft. Storage Volume Per Chamber 178.9 cubic ft. Storage Volume Per End Cap 46.9 cubic ft. Number Of Chambers Required 109 each Number Of End Caps Required 20 each Rows/Chambers 9 row(s) of 11 chamber(s) Leftover Rows/Chambers 1 row(s) of 10 chamber(s) Maximum Length 88.42 ft. Maximum Width 73.52 ft. Approx. Bed Size Required 6477 square ft. System Components Amount Of Stone Required 864 cubic yards Volume Of Excavation (Not Including Fill) 1319 cubic yards Non-woven Filter Fabric Required 1639 square yards Length Of Isolator Row 82.53 ft. Woven Isolator Row Fabric 153 square yards © ADS Stormtech 2016 APPENDIX C WATER QUALITY DESIGN COMPUTATIONS Project Title Date: Project Number Calcs By: Client Basins 1 WQCV = Watershed inches of Runoff (inches)71% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100)0.280 in A =2.33 ac V = 0.0543 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) The Stanford December 18, 2020 1530-002 B. Mathisen Pond 1 2365 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 = 40 hr Pond No : Pond 1 WQ 0.98 5.00 min 2584 ft3 2.33 acres 0.06 ac-ft Max Release Rate =0.41 cfs Time (min) Ft Collins WQ Intensity (in/hr) Inflow Volume (ft3) Outflow Adjustmen t Factor Qav (cfs) Outflow Volume (ft3) Storage Volume (ft3) 5 1.425 976 1.00 0.41 124 852 10 1.105 1514 1.00 0.41 248 1266 15 0.935 1921 0.67 0.28 248 1674 20 0.805 2206 0.63 0.26 310 1896 25 0.715 2449 0.60 0.25 372 2077 30 0.650 2672 0.58 0.24 433 2238 35 0.585 2805 0.57 0.24 495 2310 40 0.535 2932 0.56 0.23 557 2375 45 0.495 3052 0.56 0.23 619 2433 50 0.460 3151 0.55 0.23 681 2470 55 0.435 3278 0.55 0.23 743 2535 60 0.410 3370 0.54 0.22 805 2565 65 0.385 3429 0.54 0.22 867 2562 70 0.365 3500 0.54 0.22 929 2572 75 0.345 3545 0.53 0.22 991 2554 80 0.330 3617 0.53 0.22 1053 2564 85 0.315 3668 0.53 0.22 1115 2554 90 0.305 3761 0.53 0.22 1177 2584 95 0.290 3774 0.53 0.22 1238 2536 100 0.280 3836 0.53 0.22 1300 2536 105 0.270 3884 0.52 0.22 1362 2522 110 0.260 3918 0.52 0.22 1424 2494 115 0.255 4018 0.52 0.22 1486 2532 120 0.245 4028 0.52 0.22 1548 2480 *Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Input Variables Results Required Detention Volume Fort Collins, Colorado 1530-002 The Stanford Project Number : Project Name : Pond 1 A = Tc = Project Location : Design Point C = Design Storm Page 2 of 6 1530-002 Chamber Summary.xlsx Vault IDTotal RequiredWQ Volume(cf)Flow,WQ(cfs)ChamberTypeChamber Release Ratea(cfs)ChamberVolumeb(cf)Installed Camber w/ Aggregatec(cf)Mimimum No. of ChambersdTotal Release Ratee(cfs)Required Storage Volume by FAA Method(cf)Mimimum No. of ChambersfStorage Provided within the Chambersg(cf)Total Installed System Volumeh(cf)Pond1 2365 2.24 MC-3500 0.038 109.90 175.00 14 0.53 2584242638 2450SC-740a. 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 SummaryP:\1530-002\Drainage\WatQual\1530-002 Chamber Summary.xlsx 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:\1530-002\Drainage\WatQual\1530-002 Chamber Summary.xlsx APPENDIX D EROSION CONTROL REPORT Stanford Senior Living Erosion Control Report A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included with the final construction drawings. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. Grading and Erosion Control Notes can be found on Sheet CS2 of the Utility Plans. The Utility Plans at final design will also contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere to, the applicable requirements outlined in any existing Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of the Development Construction Permit. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division – Stormwater Program, before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and document the ongoing activities, inspections, and maintenance of construction BMPs. APPENDIX E ADDITIONAL REFERENCES This unofficial copy was downloaded on Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 MAP PACKET EXISTING DRAINAGE EXHIBIT DR1 – DRAINAGE EXHIBIT D VAULTF.O. D EX ex D D TCONTROLIRR D MONROE DRIVE (PRIVATE ROAD)STANFORD ROADPORTION OF LOT 3 STRACHAN SUBDIVISION THIRD FILING REC. NO. 20190052896 36" RCP 3 6 " R C P EX STRM MH 1 RIM = 5009.54 INV. IN = 5002.30 (W) INV. IN = 5002.55 (N) INV. IN = 5002.77 (NW) INV. OUT = 5022.27 (SE) EXISTING STORM STRUCTURE PER STRACHAN 3RD FILING EXISTING 30"X36" HERCP EX STRM MH 2 RIM = 5005.30 BTM BOX = 5002.21 PORTION OF LOT 3 STRACHAN SUBDIVISION THIRD FILING REC. NO. 20180064205 TRACT J FOOTHILLS MALL REDEVELOPMENT SUB. FILING NO. 3 LOT 6 FOOTHILLS MALL REDEVELOPMENT SUB. LOT 2 PRIVATE ROAD REC.NO. 88042989 & PORTION OF PARCEL 1 EXISTING INLET EXISTING INLET HORSETOOTH ROAD(3.7%)(2 .7% ) (1 . 9% ) (2 .1% ) (4 . 0% )(2.5%)(6.4%)NORTH ( IN FEET ) 0 1 INCH = 80 FEET 80 80 160 240 GRAPHIC SCALE: LEGEND: PROPERTY BOUNDARY EXISTING STORM INLET EXISTING CURB & GUTTER EXISTING SLOPE EXISTING MAJOR CONTOUR RUNOFF SUMMARY: A2 a3DESIGN POINT DRAINAGE BASIN ID DRAINAGE BASIN MINOR/MAJOR COEFF. EXISTING STORM SEWER BASIN DELINEATION 1. REFER TO "PRELIMINARY DRAINAGE REPORT FOR STANFORD SENIOR LIVING" PREPARED BY NORTHERN ENGINEERING ON 12/23/2020 FOR ADDITIONAL INFORMATION. NOTES: GRAVEL CONCRETE ASPHALT EXISTING DRAINAGE EXHIBIT FORT COLLINS, CO STANFORD SENIOR LIVING E N G I N E E R N GI EHTRON R N 12.22.2020 P:\1530-002\DWG\DRNG\1530-001_EX-DRNG.DWG DRAINAGE BASIN AREA (2.0%) DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q10 (cfs) Q100 (cfs) ex EX 2.33 0.32 0.40 15.6 14.1 1.37 2.33 6.23 MONITOR I N G W E L L TRAFFIC R A T E D UDUDUDMONITORING W EL L TRAFF I C R A T E D D VAULT ELEC VAULT ELECELEC T S VAULT F.O. DUD UD UD a C A B E D c d e 133 MC-3500 STORMTECH CHAMBERS EXISTING STORM STRUCTURE BUILT PER STRACHAN SUBDIVISION THIRD FILING EXISTING 36" RCP STORM MH EXISTING 36" RCP EXISTING STORM MH ISOLATOR ROWS (33 MC-3500 STORMTECH CHAMBERS) 100-YR OUTFALL BASIN WQ BASIN WQ BASIN CURB CUT CURB CUT INLET INLET INLET INLET INLET NYLOPLAST BASIN NYLOPLAST BASIN NYLOPLAST BASIN NYLOPLAST BASIN NYLOPLAST BASIN 30"x36" HERCP MONROE DRIVE (PRIVATE ROAD)STANFORD ROADINLET INLET F STORM DRAIN OUTFALL f VAULT ELEC D D TCONTROL IRR D BASIN C WILL BE REDESIGNED TO FULLY CAPTURE FLOWS ONCE THE MEMORY CARE COURTYARD DESIGN IS COMPLETE. PORTION OF LOT 3 STRACHAN SUBDIVISION THIRD FILING REC. NO. 20190052896 PORTION OF LOT 3 STRACHAN SUBDIVISION THIRD FILING REC. NO. 20180064205 UNPLATTED REC. NO. 2015002744 SheetSTANFORD SENIOR LIVINGThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETENGINEERNGIEHTRONRNFORT COLLINS: 301 North Howes Street, Suite 100, 80521GREELEY: 820 8th Street, 80631970.221.4158northernengineering.comof 07 DR1 DRAINAGE EXHIBIT07 CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. CALL UTILITY NOTIFICATION CENTER OF COLORADO Know what'sbelow. before you dig.Call R NORTH ( IN FEET ) 0 1 INCH = 30 FEET 30 30 60 90 PROPOSED CONTOUR EXISTING STORM SEWER PROPOSED STORM SEWER PROPOSED SWALE EXISTING CONTOUR PROPOSED CURB & GUTTER OVERLAND FLOW PROPOSED STORM INLET EXISTING LOT LINE BASIN AREA RUNOFF SUMMARY: A a EXISTING RIGHT OF WAY DESIGN POINT BASIN ID BASIN MINOR AND MAJOR C COEFFICIENTS PROPERTY BOUNDARY LEGEND: 1.REFER TO THE "PRELIMINARY DRAINAGE REPORT FOR STANFORD SENIOR LIVING" BY NORTHERN ENGINEERING DATED 12/23/2020 FOR ADDITIONAL INFORMATION. 2.STANFORD SENIOR LIVING PROJECT WILL BE DETAINING THE DIFFERENCE BETWEEN THE EXISTING 10-YEAR EVENT AND THE DEVELOPED 100-YEAR EVENT. 3.LID MEASURES ARE PROVIDED VIA ISOLATOR ROWS. NOTES: DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) a A 0.22 0.43 0.54 5.0 5.0 0.27 1.17 b B 1.13 0.95 1.00 5.0 5.0 3.07 11.29 c C 0.23 0.95 1.00 5.0 5.0 0.62 2.30 d D 0.31 0.36 0.45 5.0 5.0 0.32 1.40 e E 0.38 0.75 0.94 5.0 5.0 0.82 3.59 f F 0.05 0.80 1.00 5.0 5.0 0.11 0.50 CONCENTRATED FLOW BASIN DELINEATION