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Home My WebLink About1_Storm_Drainage_Plan_pg 1-55_03-07-2018 STORM DRAINAGE PLAN For Icon Apartment Homes at Ferguson Farm Bozeman, Montana prepared for: Braxton & Klein Capital Partners, LLC PO Box 11890 Bozeman, Montana prepared by: Sanderson Stewart 106 E. Babcock Bozeman, MT 59715 March 2018 July 25, 2017 Updated March 7, 2018 Project No. 17007.02 STORM DRAINAGE PLAN FOR ICON APARTMENT HOMES AT FERGUSON FARM BOZEMAN, MONTANA OVERVIEW NARRATIVE The purpose of this drainage plan is to quantify storm drainage improvements required for the proposed Icon Apartment Homes at Ferguson Farm at 4605 West Babcock Road in Bozeman, Montana. The site is located south of W. Babcock Street, west of Resort Drive, north of Fallon Street and east of South Cottonwood Road. The approximately 20-acre lot will include 18 apartment buildings, one clubhouse and pool and one maintenance building with a dog washing station. The 18 apartment buildings include a total of 336 units made up of one, two and three bedroom apartments. Site improvements for the buildings will include drive aisles, sidewalks, parking lots and open space. Two public easement access roads, Stafford Avenue and Palisade Drive, and one public city park will be constructed as part of the proposed apartment community project. Generally, the stormwater runoff within the apartment complex will be mitigated using pervious pavers, manufactured ADS chamber systems and dry wells. The pervious pavers will treat the water quality (the first 0.5-inch of runoff) and the water quantity volume (25-year storm event for all durations). All infiltration systems for the apartment complex have been designed to infiltrate and retain the 25-year storm event. The site currently retains 6,037 CF in an existing detention pond near the southwest corner of the site. The 6,037 CF is the cumulative volume of the runoff from the northern side of Fallon’s roadway crown and the deficient runoff from the Ferguson Farm subdivision from the south. Fallon Street, North of the roadway crown = 10-year, 2-hour runoff volume = 1,350 CF Ferguson Farm’s Deficient volume = 4,687 CF Total Runoff Volume = 6,037 CF V:17007_02_Storm_Drainage_Plan_030716_SC 2 (03/07/18) SN/jil This deficient runoff will be retained in an ADS chamber system (Chamber E) near the southwest corner of the site that is detached from the Icon Apartment Homes stormwater system. And the runoff from Fallon Street will be in Chamber A located at the northeast corner of the Stafford Avenue and Palisades Drive intersection. Runoff from Fallon Street and the portion of Stafford Avenue south of Palisade Drive and Palisade Drive west of the crosswalk and south of the center roadway crown will be captured in storm drain inlets and conveyed into an underground ADS chamber system (Chamber A) located at the northeast corner of the Stafford Avenue and Palisade Drive intersection. Runoff from a portion of Stafford Avenue north of Palisade Drive and Palisade Drive west of the crosswalk and north of the center roadway crown is captured in inlets and conveyed to a chamber system (Chamber F) in the southwest corner of the intersection of Stafford Avenue and West Babcock Street. Runoff from the east portion Palisade Drive will be captured in storm drain inlets and retained in an underground ADS chamber system (Chamber C) under Palisade Drive. Runoff from the northern portion of Resort Drive will be captured and retained in an underground ADS chamber system. The southern portion Resort Drive is captured in an existing inlet and conveyed to the development to the east. There is not an increase in impervious cover or runoff to this existing inlet. The stormwater system is designed to convey and infiltrate the peak flows from the 25-year storm event. This is done in order to meet both the water quality and conveyance storm events described in The City of Bozeman Design Standards and Specifications Policy , dated March 2004. In the scenario where the area receives a larger storm event, the site has been designed to allow for large flows to spill over into the adjacent roadways. This report presents a summary of calculations performed to quantify the stormwater runoff for the improved site. All design criteria and calculations are in accordance with The City of Bozeman Design Standards and Specifications Policy , dated March 2004. The site stormwater improvements have been designed with the intent to meet the current City of Bozeman drainage regulations for the entire site to the extent feasible. Specific site information and criteria are described below: I. Project Information A. Address: The physical address for the site is 4605 West Babcock St, Bozeman, MT 59718 B. Legal Description: The site is located on Lot 3A of Minor Subdivision 365 C. Total Area: The area of the site is approximately 19.87 acres including public access easement area. Street Easement: 2.70 acres Park Easement: 1.61 acres Apartment Community: 15.56 acres V:17007_02_Storm_Drainage_Plan_030716_SC 3 (03/07/18) SN/jil D. Existing Impervious Area: Impervious Area – 0.00 acres Pervious Area – 19.87 acres E. Post-Development Impervious Area: As a result of the development, the site will exhibit the following qualities: Impervious Area – 14.27 acres Pervious Area – 5.60 acres F. Type of Development: The development will be high density apartment homes. II. Storm Drain Design Methodology Due to the large and compartmentalized site, 41 watersheds were delineated with individual discharge locations in order to quantify the required detention volume and peak runoff volumes. The individual watershed delineations are provided in a watershed figure in Appendix A. Discharge locations are either ADS chamber systems, pervious pavers or dry wells, and referred to as stormwater units for the remainder of the report. Individual calculation spreadsheets for each watershed and stormwater unit combination is provided in Appendix B, which calculates the required retention volume after infiltration and peak runoff rate. Also in Appendix B is Table 1 which summarizes the inputs and results from each watershed. The spreadsheets use the surface area calculations from the watershed delineations to calculate the runoff coefficient and adjusted runoff coefficient based on a frequency factor of 1.1. The adjusted runoff coefficient, area, intensity and rainfall duration is used to determine the runoff volume. The discharge volume is calculated from the storm duration and the discharge rate. A discharge rate for each stormwater unit was calculated to help determine the required detention volume. The discharge rate is a function of the infiltration rate and square footage of the stormwater unit, it calculates the rate that runoff exits the stormwater unit into the natural gravels. ℎ × ℎ ∗× ℎ × 1 12 × 1 ℎ 60 × 1 60 = ℎ The natural gravels are located 3-feet below the existing surface and have high infiltration rates and will be discussed in more detail later in this report. Tying the stormwater units into the natural gravels allows the stormwater to infiltrate into the soils and restores the natural hydrology of the site. It also allows for the detention volume to be reduced. The detention volume is the difference between the runoff volume to the stormwater unit and the discharge volume from the stormwater unit via infiltration. In many cases, the stormwater units are infiltrating runoff quicker than runoff flow rate to the stormwater unit. A detention volume is calculated when the stormwater unit cannot infiltrate at the rate of the incoming flow rate. The size of the stormwater unit was determined through an iterative process. The length and width of the stormwater unit was adjusted until the provided detention volume was greater V:17007_02_Storm_Drainage_Plan_030716_SC 4 (03/07/18) SN/jil than the required detention volume. That length and width was then used to design the stormwater system. A. Runoff Calculations: The modified rational method was used to determine peak runoff rates and volumes. It was assumed the rainfall is uniformly distributed over the area for the entire duration of the storm. The rational formula provided in The City of Bozeman Standard Specifications and Policy was used to calculate the peak runoff rates on site. The rainfall intensity for the site was calculated in part by using Figure I-2 and I-3. The peak runoff rate occurs when the duration of the storm equals the time of concentration. The provided time of concentration tools, Table I-2, Table I-3 and Figure I-1, in The City of Bozeman’s Design Standard and Specifications Policy were used to calculate the time of concentration for each of the major watersheds. However, since most watersheds are predominately impervious cover, all watersheds used a conservative time of concentration of 1-minute. The time of concentration was only relevant to the traditional (inlet and piping) stormwater infrastructure systems since the pervious paver systems meet the requirements for each rainfall duration. The runoff coefficient for a particular watershed is constant for a similar land use. The runoff coefficients provided in Table I-1 were used in calculating the peak runoff rates. B. Infiltration Rates: Five test pits were excavated in May of 2017. Groundwater was present at 6-feet below existing ground surface and native gravels were present at 3-feet below ground surface. It is assumed that seasonal high ground water is located at 6-feet below existing ground surface since the test pits were excavated during the typical seasonal high ground water season. It is also important to note that detention storage within the paver systems, chamber systems and drywells is only accounted for in the first 3 feet, 5 feet and 5 feet below existing ground surface elevation, respectively. Therefore, no required detention volume is accounted for below season high ground water. A geotechnical report has also been completed for the project in August 2017 and groundwater was generally found at 6-feet below the existing surface. At one boring, located at the very southwest corner of the site one boring showed groundwater at 2.2-feet deep. Besides the 2.2- foot deep water level at one boring, the next highest groundwater level was at 5.8 feet deep. A falling head infiltration test was completed at three of the five test pits and the average infiltration rate was found to be 160 inches/hour. The data of the tests is included in Appendix E. The design of the stormwater unit used an infiltration rate of 80 inches/hour to provide a factor of safety of two. C. Stormwater Unit Volumes Paver System: 1 square foot of pave drain = 1 cubic foot of storage. The project is proposing to use a 3-ft pervious paver section. The section, as shown on sheet C9.1, is made up of 6-inch as paver, and 30 inches as stone base. Native gravels are located at V:17007_02_Storm_Drainage_Plan_030716_SC 5 (03/07/18) SN/jil 3-feet below existing ground surface. This paver section was designed to ensure that the pavers are tied into native gravels. As shown in Appendix C, the ACF environmental storage capacity determination of PaveDrain spreadsheet shows that the proposed section of pave drain has the capacity to hold 1 cubic of runoff per 1 square foot of pave drain section. In most cases, the paver units were oversized in order to allow for the use of the mechanical installer because cost of the additional pavers is less than the cost to hand install the smaller paver units. The infiltration rate considered the entire area of the pervious paver unit. " # $ % = " # & ℎ ×" # ℎ ' 1 () 1 ) Chamber System: The online ADS StormTech Design Tool was used to calculate the detention volume in conjunction with the Appendix C spreadsheets to calculate the volume after infiltration. A general detail of the ADS StormTech Chamber system is provided on sheet C9.0. A trial and error method was used between the Appendix B spreadsheets and the ADS StormTech Design Tool to ensure that the length and width between the spreadsheet and the design tool match and that the provided volume from the design tool was larger than the required volume from the spreadsheet. The infiltration rate leaving the ADS system used the entire area of the chamber system. Dry Well: The detention volumes of dry wells were calculated by using the radius and depth of the dry well barrel. * + $ % = ,× -×* . ℎ The dry well barrels proposed have a 15-inch radius and are 5-feet in depth. The infiltration rate leaving the dry well system was assumed to be the surface area of the bottom of the barrel. Most of the dry wells are located in shallow depressions. The storage provided in the depressions is included in the storage capacity calculations for the dry wells. The volume calculations for the depression areas are provided in Appendix C. D. Water Quality The development project is greater than one acre and therefore will infiltrate runoff generated from the first 0.5-inches of rainfall from a 24-hour storm. Table 1 and Figure 1 in Appendix A, show the locations of the watersheds on site. Table 1 shows the required storage volume for each watershed calculated. The runoff calculations are in Appendix B. Table 2 outlines the provided storage and type of stormwater unit for each watershed. Each stormwater unit retains the 25-year storm and infiltrates the 25-year runoff volume in under 72 hours. V:17007_02_Storm_Drainage_Plan_030716_SC 6 (03/07/18) SN/jil The stormwater storage facilities are designed to remove pollutants such as solids, silts, oils, and greases. There is no oil/water separator required on site. The media below the pavers and chambers will filter any solids, silts, oils and greases. All inlets and manholes are designed in accordance with the City of Bozeman standard details. However, a larger 18-inch sump has been design in the manholes upstream of the ADS chamber systems. Alignment between manholes is straight. However, there are limited manholes onsite due to the use of pervious paver. Storm sewer systems are designed with a slope and pipe diameter as to ensure a velocity of 3-fps. The storm sewers within the public access easement are public and will be maintained by the City of Bozeman. A minimum pipe size of 12-inch for inlet structures and 15-inch for all other structures has been used for design. E. Outlet Structures There are no offsite discharge locations as part of this project. As previously mentioned, the runoff from the southern portion of Resort Drive (Watershed 6) is captured in an existing inlet which discharges off site. Since the impervious cover draining to this inlet is not increasing, the inlet was left as is. The stormwater management plan on site is designed to infiltrate the 25-year storm event. The ultimate destination of the stormwater runoff within the apartment community is the groundwater table. III. Stormwater Design A. Pavers: Pervious pavers were proposed within the parking lot areas of the apartment complex. Specifically, the pavers are located within the first couple of feet at the beginning of the parking stalls. The area surrounding the pavers are graded towards the pavers to allow runoff to sheet flow and infiltrate into the paver section. The pavers have a flat cross slope but have a slight longitudinal grade. Since the infiltration rate is so high, pavers did not have to cover the entire parking area, only small sections were needed. The parking stalls were chosen as a desirable area for pavers because they would be susceptible to lower traffic speeds. It also seemed more practical to divert flow to parking areas rather than drive aisle. Additionally, the pervious pavers needed to remain 30 feet away and have at least 18-inches of vertical separation for perpendicular crossings from all water mains in order to meet DEQ regulations. This, in many cases, limited the potential paver areas to the parking stalls. In areas where the pavers are relatively close to buildings, the paver section will have an impermeable fabric layer on the sides of the paver section that are within 20 feet of a building. The intent of the impermeable fabric layer is to protect the building foundations from saturated soils. In the event of a storm larger than the 50-year event, the site has been graded to allow for any excess flow to overtop into the adjacent public roadways to reduce the potential for flooding at the buildings. V:17007_02_Storm_Drainage_Plan_030716_SC 7 (03/07/18) SN/jil B. Chambers: Four out of the six chamber systems are designed to retain the 25-year runoff volume from the new and existing public roads (Chamber A, C, D, F). One chamber system, Chamber E, is used to retain runoff from the deficient volume from the Ferguson Farms subdivision south of Fallon Street. The other chamber system, Chamber B, is used to retain runoff from the pool area. Chamber system A is designed to retain the runoff from Fallon Drive, the portion of Stafford Avenue south of Palisades Drive and a portion Palisades Drive west of the crosswalk. The chamber system is located within the pervious area adjacent to Building 17. The system is accessible for maintenance by Palisade Drive or the parking lot south of Building 17. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5-feet. Chamber system B is located within the pervious area southwest of the pool area. Chamber system B is design to retain runoff from the pool patio, sidewalk and landscaped area. Chamber system B is accessible for maintenance from the parking area to the west. The chamber system is located here in order to comply with landscape requirements and water easement regulations. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5-feet. Chamber system C is located within Palisade Drive. This chamber system will retain runoff from the portion of Palisades Drive east of the crosswalk. The chamber system location was chosen to avoid the required landscape area in the boulevard and park area. The Chamber system also need to be located in an area that is easily accessible for maintenance purposes. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5-feet. Chamber system D is located at the northeast corner of the site and is used to retain runoff from a portion of Resort Drive. The chamber system is accessible for maintenance from Resort Drive and the parking lot east of Building 13. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5-feet. Chamber system E is located at the southwest corner of the site and is used to retain the deficient volume from the Ferguson Farms subdivision to the south. The system will consist of a single row of chambers. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5- feet. The chamber system is accessible for maintenance from Stafford Avenue. Chamber system F is located at the northwest corner of the site and retains the volume from a portion of Stafford Avenue north of its intersection with Palisade Drive. The chamber system is accessible for maintenance from Stafford Avenue. The chamber system will not be deeper than 5-feet below the existing ground surface and does not account for volume below 5-feet. V:17007_02_Storm_Drainage_Plan_030716_SC 8 (03/07/18) SN/jil In the event of a storm larger than the 50-year event, the site has been graded to allow for any excess flow to overtop into the adjacent public roadways to reduce the potential for flooding at the buildings. C. Dry Wells: The drywells on site are designed to retain runoff from sidewalk and landscape area. The flows to the drywells are relatively small compared to the other flows on site do to the large amount of pervious area in their watersheds. Flow to the dry well will sheet flow over grassed area, which will slow down peak flows and provide some pretreatment as filtration. In the event of a storm larger than the 50-year event, the site has been graded to allow for any excess flow to overtop into the adjacent public roadways to reduce the potential for flooding at the buildings. V:17007_02_Storm_Drainage_Plan_030716_SC 9 (03/07/18) SN/jil Appendix A WATERSHED MAP V:17007_02_Storm_Drainage_Plan_030716_SC 10 (03/07/18) SN/jil Appendix B HYDROLOGY CALCULATIONS Table 1: Watershed Properties Watershed SW Unit # Total Area (SF)Impervious Area (SF) Pervious Area (SF) 25-year Runoff Volume After Infiltration (CF)Provided Storage (CF) 1 Unit 1 27535 20625 6910 1577.01 1814.00 2 Unit 1 25809 20969 4840 3 Unit 2 13165 7564 5601 373.66 571.10 4 Unit 3 10721 5471 5250 57.01 320.40 5 Unit 4 14287 7631 6656 394.40 635.10 6 Offsite 34525 27699 6826 5853.82 N/A 7 Unit 5 30217 23129 7088 392.81 403.17 8 Unit 6 10781 10715 66 103.48 427.20 9 Unit 7 28062 24752 3310 409.36 409.40 10 Unit 8 14374 12570 1804 207.83 209.15 11 Unit 9 7196 6910 286 154.50 213.60 12 Unit 10 51919 29513 22406 557.60 606.00 13 Drain 5188 5188 0 1039.49 #N/A 14 Unit 11 12804 7336 5468 357.22 402.12 15 Unit 12 10173 10016 157 154.50 172.55 16 Unit 13 25059 19677 5382 329.20 344.96 17 Unit 14 17267 16355 912 188.66 427.20 18 Unit 1 34625 26288 8337 19 Unit 16 4825 4820 5 39.35 249.20 20 Unit 17 20512 19013 1499 223.86 471.70 21 Unit 18 27598 27598 0 230.02 1388.40 22 Unit 19 63397 49197 14200 571.26 1553.05 23 Unit 20 19238 13403 5835 342.26 440.00 24 Unit 1 27576 19950 7626 25 Unit 15 6820 2746 4074 1206.36 1350.00 26 Unit 15 12464 9650 2814 27 Unit 20 8647 6039 2608 28 Unit 22 63920 21205 42715 29 Unit 21 23767 13603 10164 242.69 318.00 30 Unit 22 59707 53228 6479 1207.55 1633.15 31 Unit 26 9694 9307 387 83.95 319.19 32 Unit 15 29542 19415 10127 33 Unit 24 25936 14315 11621 185.30 493.95 34 Unit 26 12044 9803 2241 323.72 319.19 35 Unit 28 15733 15733 0 157.72 578.50 36 Unit 29 66946 63080 3866 904.15 1223.75 37 Unit 27 8196 6891 1305 76.62 226.95 38 Unit 30 3972 3567 405 30.12 186.90 39 Unit 15 17229 7088 10141 40 Unit 23 - Future 27382 13184 14198 991.35 Future 41 Unit 25 - Future 31854 31854 0 153.67 481.00 Included in WS 30 Calculations Included in WS 25 Calculations Included in WS 25 Calculations Included in WS 41 Calculations Ferguson Farms Deficent Volume Included in WS 1 Calculations Included in WS 1 Calculations Included in WS 1 Calculations Included in WS 25 Calculations Included in WS 23 Calculations Table 2: Stormwater Unit Properties Watershed SW Unit # Type Width (FT) Length (FT) Depth (FT)*Storage (CF) 1 & 2 & 18 & 24 Unit 1 Chamber A 1814.00 3 Unit 2 Dry Well 28.27 4 571.10 4 Unit 3 PaveDrain 6 60 320.40 5 Unit 4 Dry Well 28.27 4 635.10 6 Offiste 7 Unit 5 PaveDrain 6 75.5 403.17 8 Unit 6 PaveDrain 5 96 427.20 9 Unit 7 PaveDrain 5 92 409.40 10 Unit 8 PaveDrain 10 23.5 209.15 11 Unit 9 PaveDrain 10 24 213.60 12 Unit 10 Chamber B 606.00 13 Drain to Sewer 14 Unit 11 Dry Well 100.53 4 402.12 15 Unit 12 PaveDrain 4 48.47 172.55 16 Unit 13 PaveDrain 8 48.45 344.96 17 Unit 14 PaveDrain 5 96 427.20 19 Unit 16 PaveDrain 5 56 249.20 20 Unit 17 PaveDrain 5 106 471.70 21 Unit 18 PaveDrain 5 312 1388.40 22 Unit 19 PaveDrain 5 349 1553.05 23 & 27 Unit 20 Chamber C 440.00 25 & 26 & 32 & 39 Unit 15 Chamber F 1350.00 29 Unit 21 Chamber D 318.00 30&28 Unit 22 PaveDrain 5 367 1633.15 31 Unit 23 PaveDrain 5 96 427.20 33 Unit 24 PaveDrain 5 111 493.95 34 Unit 26 Dry Well 56.55 4 319.19 35 Unit 28 PaveDrain 5 130 578.50 36 Unit 29 PaveDrain 5 275 1223.75 37 Unit 27 PaveDrain 5 51 226.95 38 Unit 30 PaveDrain 5 42 186.90 40&41 Future Chambers Ferguson Farms Chamber E Chamber E 481.00 See Appendix C See Appendix C See Appendix C See Appendix C See Appendix C See Appendix C Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =2.92 cfs 21 75 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 87832 2.016 0.9 1.1 0.99 0.99 1.996181818 27713 0.636 0.2 1.1 0.22 0.22 0.139964646 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 115545 2.6525 2.1361 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =2.14 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 22.90 5 3.83 8.17 10 2.46 5.24 15 1.89 4.05 20 1.58 3.37 25 1.37 2.92 30 1.22 2.60 35 1.10 2.35 40 1.01 2.16 45 0.94 2.00 50 0.88 1.87 55 0.82 1.76 60 0.78 1.67 75 0.68 1.44 90 0.60 1.29 105 0.55 1.16 120 0.50 1.07 150 0.43 0.93 180 0.39 0.82 360 0.25 0.53 720 0.16 0.34 1440 0.10 1,577.01 ft3 22.90 (ft3/s) 14673.49 126000.00 ----- 18832.34 252000.00 ----- 8908.24 31500.00 ----- 11433.06 63000.00 ----- 7698.37 21000.00 ----- 8342.31 26250.00 ----- 6940.98 15750.00 ----- 7337.06 18375.00 ----- 5998.30 10500.00 ----- 6500.04 13125.00 ----- 5617.24 8750.00 ----- 5813.32 9625.00 ----- 5183.65 7000.00 ----- 5408.17 7875.00 ----- 4673.66 5250.00 ----- 4940.36 6125.00 ----- 4038.91 3500.00 538.91 4376.75 4375.00 1.75 3146.98 1750.00 1396.98 3641.55 2625.00 1016.55 1373.71 175.00 1198.71 2452.01 875.00 1577.01 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7321 Cwd x Cf =0.81 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 1, 2, 18, 24 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Area (sq.ft.)Infiltration Rate (in/hr) Discharge Rate, d =0.05 cfs 28.27 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 7564 0.174 0.9 1.1 0.99 0.99 0.171909091 5601 0.129 0.2 1.1 0.22 0.22 0.028287879 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 13165 0.3022 0.2002 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.20 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.15 5 3.83 0.77 10 2.46 0.49 15 1.89 0.38 20 1.58 0.32 25 1.37 0.27 30 1.22 0.24 35 1.10 0.22 40 1.01 0.20 45 0.94 0.19 50 0.88 0.18 55 0.82 0.17 60 0.78 0.16 75 0.68 0.14 90 0.60 0.12 105 0.55 0.11 120 0.50 0.10 150 0.43 0.09 180 0.39 0.08 360 0.25 0.05 720 0.16 0.03 1440 0.10 373.66 ft3 2.15 (ft3/s) 1375.18 2261.95 ----- 1764.94 4523.89 ----- 834.87 565.49 269.38 1071.49 1130.97 ----- 721.48 376.99 344.49 781.83 471.24 310.59 650.50 282.74 367.76 687.62 329.87 357.75 562.15 188.50 373.66 609.18 235.62 373.56 526.44 157.08 369.36 544.82 172.79 372.03 485.80 125.66 360.14 506.85 141.37 365.48 438.01 94.25 343.76 463.00 109.96 353.05 378.52 62.83 315.69 410.18 78.54 331.64 294.93 31.42 263.51 341.28 47.12 294.16 128.74 3.14 125.60 229.80 15.71 214.09 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6022 Cwd x Cf =0.66 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 3 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.67 cfs 6 60 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 5471 0.126 0.9 1.1 0.99 0.99 0.124340909 5250 0.121 0.2 1.1 0.22 0.22 0.026515152 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 10721 0.2461 0.1509 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.15 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 1.62 5 3.83 0.58 10 2.46 0.37 15 1.89 0.29 20 1.58 0.24 25 1.37 0.21 30 1.22 0.18 35 1.10 0.17 40 1.01 0.15 45 0.94 0.14 50 0.88 0.13 55 0.82 0.12 60 0.78 0.12 75 0.68 0.10 90 0.60 0.09 105 0.55 0.08 120 0.50 0.08 150 0.43 0.07 180 0.39 0.06 360 0.25 0.04 720 0.16 0.02 1440 0.10 57.01 ft3 1.62 (ft3/s) 1036.25 28800.00 ----- 1329.95 57600.00 ----- 629.11 7200.00 ----- 807.41 14400.00 ----- 543.66 4800.00 ----- 589.14 6000.00 ----- 490.18 3600.00 ----- 518.15 4200.00 ----- 423.60 2400.00 ----- 459.04 3000.00 ----- 396.69 2000.00 ----- 410.54 2200.00 ----- 366.07 1600.00 ----- 381.93 1800.00 ----- 330.06 1200.00 ----- 348.89 1400.00 ----- 285.23 800.00 ----- 309.09 1000.00 ----- 222.24 400.00 ----- 257.17 600.00 ----- 97.01 40.00 57.01 173.16 200.00 ----- = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.5572 Cwd x Cf =0.61 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 4 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Area (sq.ft.)Infiltration Rate (in/hr) Discharge Rate, d =0.05 cfs 28.27 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 7631 0.175 0.9 1.1 0.99 0.99 0.173431818 6656 0.153 0.2 1.1 0.22 0.22 0.033616162 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 14287 0.3280 0.2070 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.21 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.22 5 3.83 0.79 10 2.46 0.51 15 1.89 0.39 20 1.58 0.33 25 1.37 0.28 30 1.22 0.25 35 1.10 0.23 40 1.01 0.21 45 0.94 0.19 50 0.88 0.18 55 0.82 0.17 60 0.78 0.16 75 0.68 0.14 90 0.60 0.12 105 0.55 0.11 120 0.50 0.10 150 0.43 0.09 180 0.39 0.08 360 0.25 0.05 720 0.16 0.03 1440 0.10 394.40 ft3 2.22 (ft3/s) 1422.24 2261.95 ----- 1825.34 4523.89 ----- 863.44 565.49 297.95 1108.16 1130.97 ----- 746.17 376.99 369.18 808.59 471.24 337.35 672.76 282.74 390.02 711.15 329.87 381.28 581.39 188.50 392.90 630.02 235.62 394.40 544.46 157.08 387.38 563.46 172.79 390.67 502.43 125.66 376.77 524.19 141.37 382.82 453.00 94.25 358.75 478.85 109.96 368.89 391.48 62.83 328.64 424.22 78.54 345.68 305.02 31.42 273.61 352.96 47.12 305.84 133.15 3.14 130.01 237.66 15.71 221.96 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.5739 Cwd x Cf =0.63 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 5 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Discharge Rate, d =0.00 cfs Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 27699 0.636 0.9 1.1 0.99 0.99 0.629522727 6826 0.157 0.2 1.1 0.22 0.22 0.034474747 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 34525 0.7926 0.6640 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.66 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 7.12 5 3.83 2.54 10 2.46 1.63 15 1.89 1.26 20 1.58 1.05 25 1.37 0.91 30 1.22 0.81 35 1.10 0.73 40 1.01 0.67 45 0.94 0.62 50 0.88 0.58 55 0.82 0.55 60 0.78 0.52 75 0.68 0.45 90 0.60 0.40 105 0.55 0.36 120 0.50 0.33 150 0.43 0.29 180 0.39 0.26 360 0.25 0.16 720 0.16 0.11 1440 0.10 5,853.82 ft3 7.12 (ft3/s) 4561.09 0.00 4561.09 5853.82 0.00 5853.82 2769.03 0.00 2769.03 3553.84 0.00 3553.84 2392.95 0.00 2392.95 2593.12 0.00 2593.12 2157.53 0.00 2157.53 2280.64 0.00 2280.64 1864.50 0.00 1864.50 2020.46 0.00 2020.46 1746.06 0.00 1746.06 1807.01 0.00 1807.01 1611.28 0.00 1611.28 1681.07 0.00 1681.07 1452.76 0.00 1452.76 1535.65 0.00 1535.65 1255.45 0.00 1255.45 1360.47 0.00 1360.47 978.20 0.00 978.20 1131.94 0.00 1131.94 427.00 0.00 427.00 762.18 0.00 762.18 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7616 Cwd x Cf =0.84 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 6 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.84 cfs 6 75.5 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 23129 0.531 0.9 1.1 0.99 0.99 0.525659091 7088 0.163 0.2 1.1 0.22 0.22 0.03579798 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 30217 0.6937 0.5615 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.56 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 6.02 5 3.83 2.15 10 2.46 1.38 15 1.89 1.06 20 1.58 0.88 25 1.37 0.77 30 1.22 0.68 35 1.10 0.62 40 1.01 0.57 45 0.94 0.53 50 0.88 0.49 55 0.82 0.46 60 0.78 0.44 75 0.68 0.38 90 0.60 0.34 105 0.55 0.31 120 0.50 0.28 150 0.43 0.24 180 0.39 0.22 360 0.25 0.14 720 0.16 0.09 1440 0.10 392.81 ft3 6.02 (ft3/s) 3856.73 36240.00 ----- 4949.82 72480.00 ----- 2341.41 9060.00 ----- 3005.03 18120.00 ----- 2023.41 6040.00 ----- 2192.66 7550.00 ----- 1824.34 4530.00 ----- 1928.45 5285.00 ----- 1576.57 3020.00 ----- 1708.45 3775.00 ----- 1476.41 2516.67 ----- 1527.95 2768.33 ----- 1362.45 2013.33 ----- 1421.46 2265.00 ----- 1228.41 1510.00 ----- 1298.51 1761.67 ----- 1061.57 1006.67 54.91 1150.37 1258.33 ----- 827.14 503.33 323.81 957.13 755.00 202.13 361.06 50.33 310.73 644.48 251.67 392.81 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7358 Cwd x Cf =0.81 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 7 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.89 cfs 5 96 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 10715 0.246 0.9 1.1 0.99 0.99 0.243522727 66 0.002 0.2 1.1 0.22 0.22 0.000333333 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 10781 0.2475 0.2439 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.24 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.61 5 3.83 0.93 10 2.46 0.60 15 1.89 0.46 20 1.58 0.38 25 1.37 0.33 30 1.22 0.30 35 1.10 0.27 40 1.01 0.25 45 0.94 0.23 50 0.88 0.21 55 0.82 0.20 60 0.78 0.19 75 0.68 0.16 90 0.60 0.15 105 0.55 0.13 120 0.50 0.12 150 0.43 0.11 180 0.39 0.09 360 0.25 0.06 720 0.16 0.04 1440 0.10 103.48 ft3 2.61 (ft3/s) 1675.08 38400.00 ----- 2149.84 76800.00 ----- 1016.94 9600.00 ----- 1305.16 19200.00 ----- 878.82 6400.00 ----- 952.33 8000.00 ----- 792.36 4800.00 ----- 837.58 5600.00 ----- 684.75 3200.00 ----- 742.02 4000.00 ----- 641.25 2666.67 ----- 663.63 2933.33 ----- 591.75 2133.33 ----- 617.38 2400.00 ----- 533.53 1600.00 ----- 563.98 1866.67 ----- 461.07 1066.67 ----- 499.64 1333.33 ----- 359.25 533.33 ----- 415.71 800.00 ----- 156.82 53.33 103.48 279.91 266.67 13.25 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8957 Cwd x Cf =0.99 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 8 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.85 cfs 5 92 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 24757 0.568 0.9 1.1 0.99 0.99 0.562659091 3305 0.076 0.2 1.1 0.22 0.22 0.016691919 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 28062 0.6442 0.5794 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.58 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 6.21 5 3.83 2.22 10 2.46 1.42 15 1.89 1.10 20 1.58 0.91 25 1.37 0.79 30 1.22 0.70 35 1.10 0.64 40 1.01 0.59 45 0.94 0.54 50 0.88 0.51 55 0.82 0.48 60 0.78 0.45 75 0.68 0.39 90 0.60 0.35 105 0.55 0.32 120 0.50 0.29 150 0.43 0.25 180 0.39 0.22 360 0.25 0.14 720 0.16 0.09 1440 0.10 409.46 ft3 6.21 (ft3/s) 3979.64 36800.00 ----- 5107.58 73600.00 ----- 2416.03 9200.00 ----- 3100.80 18400.00 ----- 2087.90 6133.33 ----- 2262.55 7666.67 ----- 1882.49 4600.00 ----- 1989.91 5366.67 ----- 1626.82 3066.67 ----- 1762.90 3833.33 ----- 1523.47 2555.56 ----- 1576.65 2811.11 ----- 1405.87 2044.44 ----- 1466.77 2300.00 ----- 1267.56 1533.33 ----- 1339.89 1788.89 ----- 1095.41 1022.22 73.18 1187.03 1277.78 ----- 853.50 511.11 342.39 987.64 766.67 220.97 372.57 51.11 321.46 665.02 255.56 409.46 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8176 Cwd x Cf =0.90 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 9 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.44 cfs 10 23.5 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 12570 0.289 0.9 1.1 0.99 0.99 0.285681818 1804 0.041 0.2 1.1 0.22 0.22 0.009111111 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 14374 0.3300 0.2948 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.29 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 3.16 5 3.83 1.13 10 2.46 0.72 15 1.89 0.56 20 1.58 0.46 25 1.37 0.40 30 1.22 0.36 35 1.10 0.32 40 1.01 0.30 45 0.94 0.28 50 0.88 0.26 55 0.82 0.24 60 0.78 0.23 75 0.68 0.20 90 0.60 0.18 105 0.55 0.16 120 0.50 0.15 150 0.43 0.13 180 0.39 0.11 360 0.25 0.07 720 0.16 0.05 1440 0.10 207.83 ft3 3.16 (ft3/s) 2024.97 18800.00 ----- 2598.90 37600.00 ----- 1229.36 4700.00 ----- 1577.79 9400.00 ----- 1062.39 3133.33 ----- 1151.26 3916.67 ----- 957.87 2350.00 ----- 1012.53 2741.67 ----- 827.78 1566.67 ----- 897.02 1958.33 ----- 775.19 1305.56 ----- 802.25 1436.11 ----- 715.35 1044.44 ----- 746.34 1175.00 ----- 644.98 783.33 ----- 681.78 913.89 ----- 557.38 522.22 35.16 604.00 652.78 ----- 434.29 261.11 173.18 502.54 391.67 110.88 189.57 26.11 163.46 338.38 130.56 207.83 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8121 Cwd x Cf =0.89 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 10 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.44 cfs 10 24 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 6910 0.159 0.9 1.1 0.99 0.99 0.157045455 286 0.007 0.2 1.1 0.22 0.22 0.001444444 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 7196 0.1652 0.1585 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.16 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 1.70 5 3.83 0.61 10 2.46 0.39 15 1.89 0.30 20 1.58 0.25 25 1.37 0.22 30 1.22 0.19 35 1.10 0.17 40 1.01 0.16 45 0.94 0.15 50 0.88 0.14 55 0.82 0.13 60 0.78 0.12 75 0.68 0.11 90 0.60 0.10 105 0.55 0.09 120 0.50 0.08 150 0.43 0.07 180 0.39 0.06 360 0.25 0.04 720 0.16 0.03 1440 0.10 75.25 ft3 1.70 (ft3/s) Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 11 Surface Type Landscape Totals = 0.8722 Cwd x Cf =0.96 Runoff Volume Discharge Volume Site Detention = = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) 101.92 26.67 75.25 181.93 133.33 48.59 233.49 266.67 ----- 270.18 400.00 ----- 299.66 533.33 ----- 324.73 666.67 ----- 346.76 800.00 ----- 366.55 933.33 ----- 384.60 1066.67 ----- 401.26 1200.00 ----- 416.77 1333.33 ----- 431.32 1466.67 ----- 445.04 1600.00 ----- 482.27 2000.00 ----- 514.98 2400.00 ----- 544.37 2800.00 ----- 571.18 3200.00 ----- 618.95 4000.00 ----- 660.94 4800.00 ----- 848.27 9600.00 ----- 1088.69 19200.00 ----- 1397.25 38400.00 ----- = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =1.14 cfs 11 56 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 29513 0.678 0.9 1.1 0.99 0.99 0.67075 22406 0.514 0.2 1.1 0.22 0.22 0.113161616 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 51919 1.1919 0.7839 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.78 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 8.40 5 3.83 3.00 10 2.46 1.92 15 1.89 1.48 20 1.58 1.24 25 1.37 1.07 30 1.22 0.95 35 1.10 0.86 40 1.01 0.79 45 0.94 0.74 50 0.88 0.69 55 0.82 0.65 60 0.78 0.61 75 0.68 0.53 90 0.60 0.47 105 0.55 0.43 120 0.50 0.39 150 0.43 0.34 180 0.39 0.30 360 0.25 0.19 720 0.16 0.12 1440 0.10 557.60 ft3 8.40 (ft3/s) 5384.80 49280.00 ----- 6910.99 98560.00 ----- 3269.10 12320.00 ----- 4195.64 24640.00 ----- 2825.11 8213.33 ----- 3061.42 10266.67 ----- 2547.16 6160.00 ----- 2692.51 7186.67 ----- 2201.22 4106.67 ----- 2385.35 5133.33 ----- 2061.38 3422.22 ----- 2133.34 3764.44 ----- 1902.27 2737.78 ----- 1984.66 3080.00 ----- 1715.12 2053.33 ----- 1812.99 2395.56 ----- 1482.18 1368.89 113.29 1606.16 1711.11 ----- 1154.86 684.44 470.42 1336.36 1026.67 309.69 504.12 68.44 435.67 899.83 342.22 557.60 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.5979 Cwd x Cf =0.66 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 12 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.00 cfs Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 5188 0.119 0.9 1.1 0.99 0.99 0.117909091 0 0.000 0.2 1.1 0.22 0.22 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 5188 0.1191 0.1179 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.12 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 1.26 5 3.83 0.45 10 2.46 0.29 15 1.89 0.22 20 1.58 0.19 25 1.37 0.16 30 1.22 0.14 35 1.10 0.13 40 1.01 0.12 45 0.94 0.11 50 0.88 0.10 55 0.82 0.10 60 0.78 0.09 75 0.68 0.08 90 0.60 0.07 105 0.55 0.06 120 0.50 0.06 150 0.43 0.05 180 0.39 0.05 360 0.25 0.03 720 0.16 0.02 1440 0.10 1,039.49 ft3 1.26 (ft3/s) 809.93 0.00 809.93 1039.49 0.00 1039.49 491.71 0.00 491.71 631.07 0.00 631.07 424.93 0.00 424.93 460.47 0.00 460.47 383.12 0.00 383.12 404.98 0.00 404.98 331.09 0.00 331.09 358.78 0.00 358.78 310.06 0.00 310.06 320.88 0.00 320.88 286.12 0.00 286.12 298.52 0.00 298.52 257.97 0.00 257.97 272.69 0.00 272.69 222.94 0.00 222.94 241.58 0.00 241.58 173.70 0.00 173.70 201.00 0.00 201.00 75.82 0.00 75.82 135.34 0.00 135.34 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.9000 Cwd x Cf =0.99 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 13 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Area (sq.ft.)Infiltration Rate (in/hr) Discharge Rate, d =0.05 cfs 28.27433388 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 7336 0.168 0.9 1.1 0.99 0.99 0.166727273 5468 0.126 0.2 1.1 0.22 0.22 0.027616162 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 12804 0.2939 0.1943 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.19 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.08 5 3.83 0.74 10 2.46 0.48 15 1.89 0.37 20 1.58 0.31 25 1.37 0.27 30 1.22 0.24 35 1.10 0.21 40 1.01 0.20 45 0.94 0.18 50 0.88 0.17 55 0.82 0.16 60 0.78 0.15 75 0.68 0.13 90 0.60 0.12 105 0.55 0.11 120 0.50 0.10 150 0.43 0.08 180 0.39 0.08 360 0.25 0.05 720 0.16 0.03 1440 0.10 357.22 ft3 2.08 (ft3/s) 1334.97 2261.95 ----- 1713.34 4523.89 ----- 810.46 565.49 244.97 1040.16 1130.97 ----- 700.39 376.99 323.40 758.97 471.24 287.73 631.48 282.74 348.74 667.51 329.87 337.65 545.72 188.50 357.22 591.36 235.62 355.74 511.05 157.08 353.97 528.89 172.79 356.10 471.60 125.66 345.94 492.03 141.37 350.66 425.20 94.25 330.96 449.47 109.96 339.51 367.45 62.83 304.62 398.19 78.54 319.65 286.31 31.42 254.89 331.30 47.12 284.18 124.98 3.14 121.84 223.08 15.71 207.37 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6011 Cwd x Cf =0.66 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 14 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.36 cfs 4 48.47 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 10016 0.230 0.9 1.1 0.99 0.99 0.227636364 157 0.004 0.2 1.1 0.22 0.22 0.000792929 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 10173 0.2335 0.2284 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.23 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.45 5 3.83 0.87 10 2.46 0.56 15 1.89 0.43 20 1.58 0.36 25 1.37 0.31 30 1.22 0.28 35 1.10 0.25 40 1.01 0.23 45 0.94 0.21 50 0.88 0.20 55 0.82 0.19 60 0.78 0.18 75 0.68 0.15 90 0.60 0.14 105 0.55 0.12 120 0.50 0.11 150 0.43 0.10 180 0.39 0.09 360 0.25 0.06 720 0.16 0.04 1440 0.10 154.50 ft3 2.45 (ft3/s) 1569.11 15510.40 ----- 2013.84 31020.80 ----- 952.60 3877.60 ----- 1222.60 7755.20 ----- 823.23 2585.07 ----- 892.09 3231.33 ----- 742.24 1938.80 ----- 784.59 2261.93 ----- 641.43 1292.53 ----- 695.08 1615.67 ----- 600.68 1077.11 ----- 621.65 1184.82 ----- 554.31 861.69 ----- 578.32 969.40 ----- 499.78 646.27 ----- 528.30 753.98 ----- 431.90 430.84 1.06 468.03 538.56 ----- 336.52 215.42 121.10 389.41 323.13 66.28 146.90 21.54 125.36 262.21 107.71 154.50 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8892 Cwd x Cf =0.98 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 15 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.72 cfs 8 48.45 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 19677 0.452 0.9 1.1 0.99 0.99 0.447204545 5382 0.124 0.2 1.1 0.22 0.22 0.027181818 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 25059 0.5753 0.4744 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.47 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 5.08 5 3.83 1.82 10 2.46 1.16 15 1.89 0.90 20 1.58 0.75 25 1.37 0.65 30 1.22 0.58 35 1.10 0.52 40 1.01 0.48 45 0.94 0.44 50 0.88 0.42 55 0.82 0.39 60 0.78 0.37 75 0.68 0.32 90 0.60 0.29 105 0.55 0.26 120 0.50 0.24 150 0.43 0.21 180 0.39 0.18 360 0.25 0.12 720 0.16 0.08 1440 0.10 329.20 ft3 5.08 (ft3/s) 3258.63 31008.00 ----- 4182.21 62016.00 ----- 1978.30 7752.00 ----- 2539.01 15504.00 ----- 1709.62 5168.00 ----- 1852.63 6460.00 ----- 1541.42 3876.00 ----- 1629.38 4522.00 ----- 1332.08 2584.00 ----- 1443.50 3230.00 ----- 1247.45 2153.33 ----- 1291.00 2368.67 ----- 1151.16 1722.67 ----- 1201.02 1938.00 ----- 1037.91 1292.00 ----- 1097.13 1507.33 ----- 896.94 861.33 35.61 971.97 1076.67 ----- 698.87 430.67 268.20 808.70 646.00 162.70 305.07 43.07 262.00 544.53 215.33 329.20 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7497 Cwd x Cf =0.82 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 16 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.89 cfs 5 96 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 16355 0.375 0.9 1.1 0.99 0.99 0.371704545 912 0.021 0.2 1.1 0.22 0.22 0.004606061 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 17267 0.3964 0.3763 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.38 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 4.03 5 3.83 1.44 10 2.46 0.92 15 1.89 0.71 20 1.58 0.59 25 1.37 0.51 30 1.22 0.46 35 1.10 0.41 40 1.01 0.38 45 0.94 0.35 50 0.88 0.33 55 0.82 0.31 60 0.78 0.29 75 0.68 0.25 90 0.60 0.23 105 0.55 0.21 120 0.50 0.19 150 0.43 0.16 180 0.39 0.15 360 0.25 0.09 720 0.16 0.06 1440 0.10 188.66 ft3 4.03 (ft3/s) 2584.93 38400.00 ----- 3317.57 76800.00 ----- 1569.30 9600.00 ----- 2014.09 19200.00 ----- 1356.17 6400.00 ----- 1469.61 8000.00 ----- 1222.75 4800.00 ----- 1292.52 5600.00 ----- 1056.68 3200.00 ----- 1145.07 4000.00 ----- 989.55 2666.67 ----- 1024.09 2933.33 ----- 913.17 2133.33 ----- 952.72 2400.00 ----- 823.33 1600.00 ----- 870.31 1866.67 ----- 711.51 1066.67 ----- 771.02 1333.33 ----- 554.38 533.33 21.05 641.51 800.00 ----- 242.00 53.33 188.66 431.95 266.67 165.29 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8630 Cwd x Cf =0.95 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 17 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.52 cfs 5 56 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 4820 0.111 0.9 1.1 0.99 0.99 0.109545455 5 0.000 0.2 1.1 0.22 0.22 2.52525E-05 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 4825 0.1108 0.1096 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.11 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 1.17 5 3.83 0.42 10 2.46 0.27 15 1.89 0.21 20 1.58 0.17 25 1.37 0.15 30 1.22 0.13 35 1.10 0.12 40 1.01 0.11 45 0.94 0.10 50 0.88 0.10 55 0.82 0.09 60 0.78 0.09 75 0.68 0.07 90 0.60 0.07 105 0.55 0.06 120 0.50 0.05 150 0.43 0.05 180 0.39 0.04 360 0.25 0.03 720 0.16 0.02 1440 0.10 39.35 ft3 1.17 (ft3/s) 752.66 22400.00 ----- 965.98 44800.00 ----- 456.94 5600.00 ----- 586.44 11200.00 ----- 394.88 3733.33 ----- 427.91 4666.67 ----- 356.03 2800.00 ----- 376.34 3266.67 ----- 307.67 1866.67 ----- 333.41 2333.33 ----- 288.13 1555.56 ----- 298.19 1711.11 ----- 265.89 1244.44 ----- 277.40 1400.00 ----- 239.73 933.33 ----- 253.41 1088.89 ----- 207.17 622.22 ----- 224.50 777.78 ----- 161.42 311.11 ----- 186.79 466.67 ----- 70.46 31.11 39.35 125.77 155.56 ----- = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8993 Cwd x Cf =0.99 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 19 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.98 cfs 5 106 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 19013 0.436 0.9 1.1 0.99 0.99 0.432113636 1499 0.034 0.2 1.1 0.22 0.22 0.007570707 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 20512 0.4709 0.4397 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.44 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 4.71 5 3.83 1.68 10 2.46 1.08 15 1.89 0.83 20 1.58 0.69 25 1.37 0.60 30 1.22 0.53 35 1.10 0.48 40 1.01 0.44 45 0.94 0.41 50 0.88 0.39 55 0.82 0.36 60 0.78 0.34 75 0.68 0.30 90 0.60 0.26 105 0.55 0.24 120 0.50 0.22 150 0.43 0.19 180 0.39 0.17 360 0.25 0.11 720 0.16 0.07 1440 0.10 223.86 ft3 4.71 (ft3/s) 3020.25 42400.00 ----- 3876.27 84800.00 ----- 1833.59 10600.00 ----- 2353.27 21200.00 ----- 1584.56 7066.67 ----- 1717.10 8833.33 ----- 1428.67 5300.00 ----- 1510.19 6183.33 ----- 1234.63 3533.33 ----- 1337.91 4416.67 ----- 1156.20 2944.44 ----- 1196.56 3238.89 ----- 1066.95 2355.56 ----- 1113.17 2650.00 ----- 961.98 1766.67 ----- 1016.88 2061.11 ----- 831.33 1177.78 ----- 900.87 1472.22 ----- 647.74 588.89 58.86 749.54 883.33 ----- 282.75 58.89 223.86 504.70 294.44 210.26 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8488 Cwd x Cf =0.93 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 20 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =2.89 cfs 5 312 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 27598 0.634 0.9 1.1 0.99 0.99 0.627227273 0 0.000 0.2 1.1 0.22 0.22 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 27598 0.6336 0.6272 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.63 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 6.72 5 3.83 2.40 10 2.46 1.54 15 1.89 1.19 20 1.58 0.99 25 1.37 0.86 30 1.22 0.76 35 1.10 0.69 40 1.01 0.63 45 0.94 0.59 50 0.88 0.55 55 0.82 0.52 60 0.78 0.49 75 0.68 0.42 90 0.60 0.38 105 0.55 0.34 120 0.50 0.31 150 0.43 0.27 180 0.39 0.24 360 0.25 0.16 720 0.16 0.10 1440 0.10 230.02 ft3 6.72 (ft3/s) 4308.51 124800.00 ----- 5529.66 249600.00 ----- 2615.69 31200.00 ----- 3357.04 62400.00 ----- 2260.44 20800.00 ----- 2449.52 26000.00 ----- 2038.05 15600.00 ----- 2154.35 18200.00 ----- 1761.25 10400.00 ----- 1908.58 13000.00 ----- 1649.37 8666.67 ----- 1706.94 9533.33 ----- 1522.05 6933.33 ----- 1587.98 7800.00 ----- 1372.31 5200.00 ----- 1450.61 6066.67 ----- 1185.93 3466.67 ----- 1285.13 4333.33 ----- 924.03 1733.33 ----- 1069.25 2600.00 ----- 403.36 173.33 230.02 719.97 866.67 ----- = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.9000 Cwd x Cf =0.99 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 21 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =3.23 cfs 5 349 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 49197 1.129 0.9 1.1 0.99 0.99 1.118113636 14200 0.326 0.2 1.1 0.22 0.22 0.071717172 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 63397 1.4554 1.1898 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.19 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 12.75 5 3.83 4.55 10 2.46 2.92 15 1.89 2.25 20 1.58 1.87 25 1.37 1.63 30 1.22 1.45 35 1.10 1.31 40 1.01 1.20 45 0.94 1.12 50 0.88 1.04 55 0.82 0.98 60 0.78 0.93 75 0.68 0.80 90 0.60 0.72 105 0.55 0.65 120 0.50 0.60 150 0.43 0.52 180 0.39 0.46 360 0.25 0.29 720 0.16 0.19 1440 0.10 571.26 ft3 12.75 (ft3/s) 8173.11 139600.00 ----- 10489.59 279200.00 ----- 4961.88 34900.00 ----- 6368.20 69800.00 ----- 4287.98 23266.67 ----- 4646.66 29083.33 ----- 3866.12 17450.00 ----- 4086.73 20358.33 ----- 3341.04 11633.33 ----- 3620.51 14541.67 ----- 3128.79 9694.44 ----- 3238.01 10663.89 ----- 2887.28 7755.56 ----- 3012.34 8725.00 ----- 2603.22 5816.67 ----- 2751.77 6786.11 ----- 2249.67 3877.78 ----- 2437.85 4847.22 ----- 1752.86 1938.89 ----- 2028.34 2908.33 ----- 765.15 193.89 571.26 1365.77 969.44 396.32 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7432 Cwd x Cf =0.82 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 22 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.71 cfs 5 77 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 19442 0.446 0.9 1.1 0.99 0.99 0.441863636 8443 0.194 0.2 1.1 0.22 0.22 0.042641414 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 27885 0.6402 0.4845 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.48 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 5.19 5 3.83 1.85 10 2.46 1.19 15 1.89 0.92 20 1.58 0.76 25 1.37 0.66 30 1.22 0.59 35 1.10 0.53 40 1.01 0.49 45 0.94 0.45 50 0.88 0.42 55 0.82 0.40 60 0.78 0.38 75 0.68 0.33 90 0.60 0.29 105 0.55 0.26 120 0.50 0.24 150 0.43 0.21 180 0.39 0.19 360 0.25 0.12 720 0.16 0.08 1440 0.10 342.26 ft3 5.19 (ft3/s) 3328.13 30800.00 ----- 4271.41 61600.00 ----- 2020.50 7700.00 ----- 2593.16 15400.00 ----- 1746.09 5133.33 ----- 1892.14 6416.67 ----- 1574.30 3850.00 ----- 1664.14 4491.67 ----- 1360.49 2566.67 ----- 1474.29 3208.33 ----- 1274.06 2138.89 ----- 1318.53 2352.78 ----- 1175.72 1711.11 ----- 1226.64 1925.00 ----- 1060.05 1283.33 ----- 1120.54 1497.22 ----- 916.08 855.56 60.52 992.70 1069.44 ----- 713.77 427.78 286.00 825.95 641.67 184.28 311.57 42.78 268.80 556.15 213.89 342.26 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6881 Cwd x Cf =0.76 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 23 & 27 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.57 cfs 11 28 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 13603 0.312 0.9 1.1 0.99 0.99 0.309159091 10164 0.233 0.2 1.1 0.22 0.22 0.051333333 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 23767 0.5456 0.3605 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.36 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 3.86 5 3.83 1.38 10 2.46 0.89 15 1.89 0.68 20 1.58 0.57 25 1.37 0.49 30 1.22 0.44 35 1.10 0.40 40 1.01 0.36 45 0.94 0.34 50 0.88 0.32 55 0.82 0.30 60 0.78 0.28 75 0.68 0.24 90 0.60 0.22 105 0.55 0.20 120 0.50 0.18 150 0.43 0.16 180 0.39 0.14 360 0.25 0.09 720 0.16 0.06 1440 0.10 242.69 ft3 3.86 (ft3/s) 2476.27 24640.00 ----- 3178.11 49280.00 ----- 1503.34 6160.00 ----- 1929.42 12320.00 ----- 1299.16 4106.67 ----- 1407.83 5133.33 ----- 1171.35 3080.00 ----- 1238.19 3593.33 ----- 1012.26 2053.33 ----- 1096.93 2566.67 ----- 947.96 1711.11 ----- 981.05 1882.22 ----- 874.78 1368.89 ----- 912.67 1540.00 ----- 788.72 1026.67 ----- 833.73 1197.78 ----- 681.60 684.44 ----- 738.61 855.56 ----- 531.08 342.22 188.86 614.54 513.33 101.21 231.82 34.22 197.60 413.80 171.11 242.69 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6006 Cwd x Cf =0.66 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 29 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =3.40 cfs 5 367 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 74433 1.709 0.9 1.1 0.99 0.99 1.691659091 49194 1.129 0.2 1.1 0.22 0.22 0.248454545 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 123627 2.8381 1.9401 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.94 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 20.79 5 3.83 7.42 10 2.46 4.76 15 1.89 3.67 20 1.58 3.06 25 1.37 2.65 30 1.22 2.36 35 1.10 2.14 40 1.01 1.96 45 0.94 1.82 50 0.88 1.70 55 0.82 1.60 60 0.78 1.51 75 0.68 1.31 90 0.60 1.17 105 0.55 1.06 120 0.50 0.97 150 0.43 0.84 180 0.39 0.75 360 0.25 0.48 720 0.16 0.31 1440 0.10 1,207.55 ft3 20.79 (ft3/s) 13326.91 146800.00 ----- 17104.10 293600.00 ----- 8090.73 36700.00 ----- 10383.86 73400.00 ----- 6991.90 24466.67 ----- 7576.75 30583.33 ----- 6304.01 18350.00 ----- 6663.74 21408.33 ----- 5447.84 12233.33 ----- 5903.53 15291.67 ----- 5101.75 10194.44 ----- 5279.84 11213.89 ----- 4707.95 8155.56 ----- 4911.86 9175.00 ----- 4244.76 6116.67 ----- 4486.98 7136.11 ----- 3668.26 4077.78 ----- 3975.10 5097.22 ----- 2858.18 2038.89 819.29 3307.37 3058.33 249.04 1247.64 203.89 1043.75 2226.99 1019.44 1207.55 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6215 Cwd x Cf =0.68 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 28 & 30 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.89 cfs 5 96 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 9307 0.214 0.9 1.1 0.99 0.99 0.211522727 387 0.009 0.2 1.1 0.22 0.22 0.001954545 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 9694 0.2225 0.2135 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.21 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.29 5 3.83 0.82 10 2.46 0.52 15 1.89 0.40 20 1.58 0.34 25 1.37 0.29 30 1.22 0.26 35 1.10 0.24 40 1.01 0.22 45 0.94 0.20 50 0.88 0.19 55 0.82 0.18 60 0.78 0.17 75 0.68 0.14 90 0.60 0.13 105 0.55 0.12 120 0.50 0.11 150 0.43 0.09 180 0.39 0.08 360 0.25 0.05 720 0.16 0.03 1440 0.10 83.95 ft3 2.29 (ft3/s) 1466.41 38400.00 ----- 1882.02 76800.00 ----- 890.25 9600.00 ----- 1142.57 19200.00 ----- 769.34 6400.00 ----- 833.69 8000.00 ----- 693.65 4800.00 ----- 733.23 5600.00 ----- 599.44 3200.00 ----- 649.59 4000.00 ----- 561.36 2666.67 ----- 580.96 2933.33 ----- 518.03 2133.33 ----- 540.47 2400.00 ----- 467.07 1600.00 ----- 493.72 1866.67 ----- 403.63 1066.67 ----- 437.39 1333.33 ----- 314.50 533.33 ----- 363.92 800.00 ----- 137.28 53.33 83.95 245.04 266.67 ----- = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8721 Cwd x Cf =0.96 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 31 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =2.33 cfs 18 70 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 65187 1.496 0.9 1.1 0.99 0.99 1.481522727 35493 0.815 0.2 1.1 0.22 0.22 0.179257576 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 100680 2.3113 1.6608 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.66 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 17.80 5 3.83 6.35 10 2.46 4.08 15 1.89 3.15 20 1.58 2.62 25 1.37 2.27 30 1.22 2.02 35 1.10 1.83 40 1.01 1.68 45 0.94 1.56 50 0.88 1.46 55 0.82 1.37 60 0.78 1.30 75 0.68 1.12 90 0.60 1.00 105 0.55 0.91 120 0.50 0.83 150 0.43 0.72 180 0.39 0.64 360 0.25 0.41 720 0.16 0.26 1440 0.10 1,206.36 ft3 17.80 (ft3/s) 11408.13 100800.00 ----- 14641.49 201600.00 ----- 6925.85 25200.00 ----- 8888.81 50400.00 ----- 5985.22 16800.00 ----- 6485.86 21000.00 ----- 5396.38 12600.00 ----- 5704.31 14700.00 ----- 4663.47 8400.00 ----- 5053.55 10500.00 ----- 4367.21 7000.00 ----- 4519.66 7700.00 ----- 4030.11 5600.00 ----- 4204.66 6300.00 ----- 3633.61 4200.00 ----- 3840.96 4900.00 ----- 3140.12 2800.00 340.12 3402.78 3500.00 ----- 2446.67 1400.00 1046.67 2831.18 2100.00 731.18 1068.01 140.00 928.01 1906.36 700.00 1206.36 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.6532 Cwd x Cf =0.72 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 32, 25, 26 & 39 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =1.03 cfs 5 111 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 14315 0.329 0.9 1.1 0.99 0.99 0.325340909 11621 0.267 0.2 1.1 0.22 0.22 0.058691919 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 25936 0.5954 0.3840 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.38 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 4.12 5 3.83 1.47 10 2.46 0.94 15 1.89 0.73 20 1.58 0.61 25 1.37 0.52 30 1.22 0.47 35 1.10 0.42 40 1.01 0.39 45 0.94 0.36 50 0.88 0.34 55 0.82 0.32 60 0.78 0.30 75 0.68 0.26 90 0.60 0.23 105 0.55 0.21 120 0.50 0.19 150 0.43 0.17 180 0.39 0.15 360 0.25 0.10 720 0.16 0.06 1440 0.10 185.30 ft3 4.12 (ft3/s) 2637.98 44400.00 ----- 3385.65 88800.00 ----- 1601.51 11100.00 ----- 2055.42 22200.00 ----- 1384.00 7400.00 ----- 1499.77 9250.00 ----- 1247.84 5550.00 ----- 1319.04 6475.00 ----- 1078.36 3700.00 ----- 1168.57 4625.00 ----- 1009.86 3083.33 ----- 1045.11 3391.67 ----- 931.91 2466.67 ----- 972.27 2775.00 ----- 840.22 1850.00 ----- 888.17 2158.33 ----- 726.11 1233.33 ----- 786.85 1541.67 ----- 565.76 616.67 ----- 654.67 925.00 ----- 246.96 61.67 185.30 440.82 308.33 132.49 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.5864 Cwd x Cf =0.64 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 33 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Area (sq.ft.)Infiltration Rate (in/hr) Discharge Rate, d =0.10 cfs 56.5 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 9803 0.225 0.9 1.1 0.99 0.99 0.222795455 2241 0.051 0.2 1.1 0.22 0.22 0.011318182 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 12044 0.2765 0.2341 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.23 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 2.51 5 3.83 0.90 10 2.46 0.57 15 1.89 0.44 20 1.58 0.37 25 1.37 0.32 30 1.22 0.28 35 1.10 0.26 40 1.01 0.24 45 0.94 0.22 50 0.88 0.21 55 0.82 0.19 60 0.78 0.18 75 0.68 0.16 90 0.60 0.14 105 0.55 0.13 120 0.50 0.12 150 0.43 0.10 180 0.39 0.09 360 0.25 0.06 720 0.16 0.04 1440 0.10 323.72 ft3 2.51 (ft3/s) 1608.16 4523.89 ----- 2063.95 9047.79 ----- 976.31 1130.97 ----- 1253.02 2261.95 ----- 843.71 753.98 89.73 914.29 942.48 ----- 760.71 565.49 195.22 804.11 659.73 144.38 657.39 376.99 280.40 712.38 471.24 241.14 615.63 314.16 301.47 637.12 345.58 291.54 568.11 251.33 316.78 592.71 282.74 309.97 512.22 188.50 323.72 541.44 219.91 321.53 442.65 125.66 316.99 479.68 157.08 322.60 344.90 62.83 282.07 399.10 94.25 304.85 150.55 6.28 144.27 268.73 31.42 237.32 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7698 Cwd x Cf =0.85 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 34 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =1.20 cfs 5 130 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 15733 0.361 0.9 1.1 0.99 0.99 0.357568182 0 0.000 0.2 1.1 0.22 0.22 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 15733 0.3612 0.3576 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.36 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 3.83 5 3.83 1.37 10 2.46 0.88 15 1.89 0.68 20 1.58 0.56 25 1.37 0.49 30 1.22 0.43 35 1.10 0.39 40 1.01 0.36 45 0.94 0.34 50 0.88 0.31 55 0.82 0.29 60 0.78 0.28 75 0.68 0.24 90 0.60 0.22 105 0.55 0.19 120 0.50 0.18 150 0.43 0.16 180 0.39 0.14 360 0.25 0.09 720 0.16 0.06 1440 0.10 157.72 ft3 3.83 (ft3/s) 2456.19 52000.00 ----- 3152.33 104000.00 ----- 1491.14 13000.00 ----- 1913.77 26000.00 ----- 1288.63 8666.67 ----- 1396.41 10833.33 ----- 1161.85 6500.00 ----- 1228.15 7583.33 ----- 1004.05 4333.33 ----- 1088.04 5416.67 ----- 940.27 3611.11 ----- 973.09 3972.22 ----- 867.69 2888.89 ----- 905.27 3250.00 ----- 782.32 2166.67 ----- 826.96 2527.78 ----- 676.07 1444.44 ----- 732.62 1805.56 ----- 526.77 722.22 ----- 609.56 1083.33 ----- 229.94 72.22 157.72 410.44 361.11 49.33 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.9000 Cwd x Cf =0.99 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 35 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =2.55 cfs 5 275 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 63080 1.448 0.9 1.1 0.99 0.99 1.433636364 3866 0.089 0.2 1.1 0.22 0.22 0.019525253 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 66946 1.5369 1.4532 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.45 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 15.57 5 3.83 5.56 10 2.46 3.57 15 1.89 2.75 20 1.58 2.29 25 1.37 1.98 30 1.22 1.77 35 1.10 1.60 40 1.01 1.47 45 0.94 1.36 50 0.88 1.27 55 0.82 1.20 60 0.78 1.13 75 0.68 0.98 90 0.60 0.87 105 0.55 0.79 120 0.50 0.73 150 0.43 0.63 180 0.39 0.56 360 0.25 0.36 720 0.16 0.23 1440 0.10 904.15 ft3 15.57 (ft3/s) 9981.97 110000.00 ----- 12811.12 220000.00 ----- 6060.03 27500.00 ----- 7777.60 55000.00 ----- 5236.99 18333.33 ----- 5675.05 22916.67 ----- 4721.76 13750.00 ----- 4991.20 16041.67 ----- 4080.48 9166.67 ----- 4421.80 11458.33 ----- 3821.25 7638.89 ----- 3954.64 8402.78 ----- 3526.29 6111.11 ----- 3679.03 6875.00 ----- 3179.36 4583.33 ----- 3360.79 5347.22 ----- 2747.56 3055.56 ----- 2977.38 3819.44 ----- 2140.80 1527.78 613.02 2477.25 2291.67 185.58 934.49 152.78 781.72 1668.04 763.89 904.15 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8596 Cwd x Cf =0.95 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 36 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.47 cfs 5 51 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 6891 0.158 0.9 1.1 0.99 0.99 0.156613636 1305 0.030 0.2 1.1 0.22 0.22 0.006590909 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 8196 0.1882 0.1632 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.16 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 1.75 5 3.83 0.62 10 2.46 0.40 15 1.89 0.31 20 1.58 0.26 25 1.37 0.22 30 1.22 0.20 35 1.10 0.18 40 1.01 0.17 45 0.94 0.15 50 0.88 0.14 55 0.82 0.13 60 0.78 0.13 75 0.68 0.11 90 0.60 0.10 105 0.55 0.09 120 0.50 0.08 150 0.43 0.07 180 0.39 0.06 360 0.25 0.04 720 0.16 0.03 1440 0.10 76.62 ft3 1.75 (ft3/s) 1121.07 20400.00 ----- 1438.82 40800.00 ----- 680.60 5100.00 ----- 873.50 10200.00 ----- 588.17 3400.00 ----- 637.36 4250.00 ----- 530.30 2550.00 ----- 560.56 2975.00 ----- 458.28 1700.00 ----- 496.61 2125.00 ----- 429.16 1416.67 ----- 444.15 1558.33 ----- 396.04 1133.33 ----- 413.19 1275.00 ----- 357.07 850.00 ----- 377.45 991.67 ----- 308.58 566.67 ----- 334.39 708.33 ----- 240.43 283.33 ----- 278.22 425.00 ----- 104.95 28.33 76.62 187.34 141.67 45.67 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7885 Cwd x Cf =0.87 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 37 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =25 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.39 cfs 5 42 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 3567 0.082 0.9 1.1 0.99 0.99 0.081068182 405 0.009 0.2 1.1 0.22 0.22 0.002045455 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 0 1.1 0.00 0.00 0 3972 0.0912 0.0831 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.08 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 10.72 0.89 5 3.83 0.32 10 2.46 0.20 15 1.89 0.16 20 1.58 0.13 25 1.37 0.11 30 1.22 0.10 35 1.10 0.09 40 1.01 0.08 45 0.94 0.08 50 0.88 0.07 55 0.82 0.07 60 0.78 0.06 75 0.68 0.06 90 0.60 0.05 105 0.55 0.05 120 0.50 0.04 150 0.43 0.04 180 0.39 0.03 360 0.25 0.02 720 0.16 0.01 1440 0.10 30.12 ft3 0.89 (ft3/s) 570.92 16800.00 ----- 732.73 33600.00 ----- 346.60 4200.00 ----- 444.84 8400.00 ----- 299.53 2800.00 ----- 324.58 3500.00 ----- 270.06 2100.00 ----- 285.47 2450.00 ----- 233.38 1400.00 ----- 252.90 1750.00 ----- 218.56 1166.67 ----- 226.19 1283.33 ----- 201.69 933.33 ----- 210.42 1050.00 ----- 181.84 700.00 ----- 192.22 816.67 ----- 157.15 466.67 ----- 170.29 583.33 ----- 122.44 233.33 ----- 141.69 350.00 ----- 53.45 23.33 30.12 95.40 116.67 ----- = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.8286 Cwd x Cf =0.91 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 38 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =10 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.00 cfs 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 45038 1.034 0.9 1 0.90 0.90 0.93053719 14198 0.326 0.2 1 0.20 0.20 0.065188246 0 1 0.00 0.00 0 0 1 0.00 0.00 0 0 1 0.00 0.00 0 59236 1.3599 0.9957 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.00 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 9.16 9.12 5 3.22 3.20 10 2.05 2.04 15 1.58 1.57 20 1.31 1.30 25 1.13 1.13 30 1.00 1.00 35 0.91 0.90 40 0.83 0.83 45 0.77 0.77 50 0.72 0.72 55 0.68 0.67 60 0.64 0.64 75 0.55 0.55 90 0.49 0.49 105 0.44 0.44 120 0.41 0.41 150 0.35 0.35 180 0.31 0.31 360 0.20 0.20 720 0.13 0.13 1440 0.08 2,924.04 ft3 9.12 (ft3/s) 5474.39 0.00 5474.39 6977.44 0.00 6977.44 3369.88 0.00 3369.88 4295.12 0.00 4295.12 2924.04 0.00 2924.04 3161.56 0.00 3161.56 2643.95 0.00 2643.95 2790.52 0.00 2790.52 2294.15 0.00 2294.15 2480.51 0.00 2480.51 2152.33 0.00 2152.33 2225.34 0.00 2225.34 1990.63 0.00 1990.63 2074.40 0.00 2074.40 1799.95 0.00 1799.95 1899.73 0.00 1899.73 1561.82 0.00 1561.82 1688.68 0.00 1688.68 1225.38 0.00 1225.38 1412.22 0.00 1412.22 547.36 0.00 547.36 961.41 0.00 961.41 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.7322 Cwd x Cf =0.73 Runoff Volume Discharge Volume Site Detention = Landscape Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed 40 & 41 Surface Type = Project: Icon Home Apartments Project #: 17007.02 Date: 7/25/2017 Design Storm Frequency =10 years Unit Width (ft)Unit Length (ft)Infiltration Rate (in/hr) Discharge Rate, d =0.63 cfs 4 85 80 Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 0 0.000 0 1 0.00 0.00 0 0 1 0.00 0.00 0 0 1 0.00 0.00 0 0 1 0.00 0.00 0 0 1 0.00 0.00 0 0 0.0000 0.0000 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj = Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 9.16 5 3.22 10 2.05 15 1.58 20 1.31 25 1.13 30 1.00 35 0.91 40 0.83 45 0.77 50 0.72 55 0.68 60 0.64 75 0.55 90 0.49 105 0.44 120 0.41 150 0.35 180 0.31 360 0.20 720 0.13 1440 0.08 153.67 ft3 - (ft3/s) 4687.00 4533.33 153.67 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft3) (ft3) = 0.0000 Cwd x Cf = Runoff Volume Discharge Volume Site Detention = Totals N/A RATIONAL METHOD FOR RUNOFF CALCULATIONS Post-Project Watershed Ferguson Farms Deficient Volume Surface Type = TABLE I-1: Runoff Coefficients for Use in the Rational Method LAND USE RUNOFF COEFFICIENTS, C Open Land 0.2 Low to Medium Density Residential 0.35 Dense Residential 0.5 Commercial Neighborhood 0.6 Commercial Downtown 0.8 Industrial 0.8 Design Standards and Specifications Policy City of Bozeman, March 2004 as Amended RAINFALL INTENSITY-DURATION CURVES (Figures I-2, I-3) Time 2 5 10 25 50 100 (min)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr) 1 4.20 7.15 9.16 10.72 13.72 15.69 5 1.60 2.55 3.22 3.83 4.74 5.34 10 1.05 1.64 2.05 2.46 3.00 3.35 15 0.83 1.26 1.58 1.89 2.30 2.56 20 0.70 1.05 1.31 1.58 1.90 2.11 25 0.61 0.91 1.13 1.37 1.64 1.82 30 0.55 0.81 1.00 1.22 1.45 1.61 35 0.50 0.73 0.91 1.10 1.31 1.45 40 0.46 0.67 0.83 1.01 1.20 1.33 45 0.43 0.63 0.77 0.94 1.11 1.22 50 0.40 0.58 0.72 0.88 1.04 1.14 55 0.38 0.55 0.68 0.82 0.97 1.07 60 0.36 0.52 0.64 0.78 0.92 1.01 75 0.31 0.45 0.55 0.68 0.79 0.87 90 0.28 0.40 0.49 0.60 0.70 0.77 105 0.26 0.36 0.44 0.55 0.64 0.69 120 0.24 0.33 0.41 0.50 0.58 0.63 150 0.21 0.29 0.35 0.43 0.50 0.55 180 0.19 0.26 0.31 0.39 0.45 0.48 360 0.12 0.17 0.20 0.25 0.28 0.30 720 0.08 0.11 0.13 0.16 0.18 0.19 1440 0.05 0.07 0.08 0.10 0.11 0.12 Storm Recurrence Interval Design Standards and Specifications Policy City of Bozeman, March 2004 as Amended Zoning District/Design Storm Requirement Zoning Type Design Rainfall Frequency Open Land 2-year Residential 10-year Commercial 10-year (p. 28, Table I-3) STORMWATER MANAGEMENT MANUAL TABLE 2-5 FREQUENCY FACTORS FOR THE RATIONAL FORMULA Recurrence Interval Adjustment Factor (Years)Cf 2 1.00 5 1.00 10 1.00 25 1.10 50 1.20 100 1.25 * C X Cf should not exceed 1.0 V:17007_02_Storm_Drainage_Plan_030716_SC 11 (03/07/18) SN/jil Appendix C STORMWATER UNIT VOLUMES COST Square Footage of 6" PaveDrain 1 sf 0.09 cf sf $0.00 #57 Stone Base Thickness 30 inches 1.00 cf ton $0.00 Capacity 40% #2 Stone Sub-Base Thickness (Not Required)0 inches 0.00 cf ton $0.00 Capacity 40% Modular Storage System 1 0 0.00 cf cf $0.00 90% TOTAL SYSTEM HEIGHT:36 inches 1.09 cf Total System Capacity 1.09 cf/sf System Efficiency SYSTEM COST:$0 $0.00 cf Cost per Cubic Foot Required System Capacity 0 cf Required PaveDrain Area:0.0 sf 6" PaveDrain 6 inches 0.09 cf/sf #57 Stone Base Thickness 6 inches 0.20 cf/sf Capacity 40% #2 Stone Sub-Base Thickness (Not Required)0 inches 0.00 cf/sf Capacity 40% Modular Storage System Height 1 0 0.00 cf/sf 95% TOTAL SYSTEM HEIGHT:12 inches 0.29 Total cf/sf CAPACITY Determine Storage Capacity of PaveDrain Determine PaveDrain Area Required to Meet Storage Demand CAPACITY ACF Environmental 800-448-3636 www.acfenvironmental.com ACF Environmental 800-448-3636 www.acfenvironmental.com Combined.txt DEPRESSION AREAS ABOVE DRY WELLS - STAGE STORAGE TABLES Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 2A Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,820.60 2 N/A N/A 0.00 N/A 0.00 4,820.70 33 0.10 1.72 1.72 1.40 1.40 4,820.80 102 0.10 6.75 8.47 6.43 7.83 4,820.90 211 0.10 15.66 24.13 15.34 23.17 4,821.00 347 0.10 27.89 52.03 27.61 50.78 4,821.10 487 0.10 41.71 93.73 41.51 92.29 4,821.20 631 0.10 55.89 149.63 55.74 148.03 4,821.30 777 0.10 70.41 220.04 70.28 218.31 4,821.40 928 0.10 85.25 305.29 85.14 303.45 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 2B Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,820.90 18 N/A N/A 0.00 N/A 0.00 4,821.00 76 0.10 4.70 4.70 4.37 4.37 4,821.10 165 0.10 12.01 16.71 11.73 16.10 4,821.20 284 0.10 22.43 39.14 22.16 38.26 4,821.30 435 0.10 35.93 75.07 35.66 73.93 4,821.40 616 0.10 52.52 127.59 52.26 126.18 Stage Storage Tables Project: Icon Home Apartments Basin Description: Unit 2C Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,821.00 7 N/A N/A 0.00 N/A 0.00 4,821.10 103 0.10 5.48 5.48 4.53 4.53 4,821.20 482 0.10 29.25 34.72 26.92 31.45 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 4A Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,822.20 6 N/A N/A 0.00 N/A 0.00 4,822.30 46 0.10 2.58 2.58 2.27 2.27 4,822.40 97 0.10 7.15 9.73 6.99 9.26 4,822.50 154 0.10 12.58 22.31 12.47 21.72 4,822.60 217 0.10 18.58 40.88 18.49 40.21 4,822.70 286 0.10 25.14 66.02 25.06 65.27 Page 1 Combined.txt 4,822.80 360 0.10 32.28 98.30 32.20 97.48 4,822.90 440 0.10 39.98 138.27 39.91 137.39 4,823.00 525 0.10 48.25 186.52 48.18 185.57 4,823.10 616 0.10 57.08 243.60 57.02 242.59 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 4B Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,822.50 20 N/A N/A 0.00 N/A 0.00 4,822.60 82 0.10 5.10 5.10 4.74 4.74 4,822.70 187 0.10 13.43 18.52 13.08 17.82 4,822.80 333 0.10 25.97 44.50 25.62 43.44 4,822.90 497 0.10 41.47 85.97 41.20 84.64 4,823.00 663 0.10 57.99 143.96 57.79 142.43 4,823.10 833 0.10 74.82 218.78 74.66 217.09 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 4C Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,822.80 28 N/A N/A 0.00 N/A 0.00 4,822.90 97 0.10 6.26 6.26 5.91 5.91 4,823.00 192 0.10 14.47 20.73 14.20 20.12 4,823.10 300 0.10 24.62 45.36 24.42 44.54 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 4D Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,823.00 49 N/A N/A 0.00 N/A 0.00 4,823.10 280 0.10 16.44 16.44 14.85 14.85 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 26A Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,808.70 0 N/A N/A 0.00 N/A 0.00 4,808.80 8 0.10 0.41 0.41 0.28 0.28 4,808.90 23 0.10 1.59 2.00 1.52 1.80 4,809.00 44 0.10 3.36 5.37 3.31 5.11 4,809.10 69 0.10 5.64 11.01 5.60 10.71 4,809.20 99 0.10 8.43 19.44 8.38 19.09 4,809.30 135 0.10 11.72 31.16 11.68 30.77 Stage Storage Table Page 2 Combined.txt Project: Icon Home Apartments Basin Description: Unit 26B Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,808.90 8 N/A N/A 0.00 N/A 0.00 4,809.00 34 0.10 2.10 2.10 1.96 1.96 4,809.10 69 0.10 5.15 7.25 5.05 7.00 4,809.20 108 0.10 8.89 16.15 8.82 15.82 4,809.30 151 0.10 12.97 29.12 12.91 28.74 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 26C Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,809.10 12 N/A N/A 0.00 N/A 0.00 4,809.20 30 0.10 2.14 2.14 2.08 2.08 4,809.30 51 0.10 4.05 6.20 4.01 6.09 Stage Storage Table Project: Icon Home Apartments Basin Description: Unit 26D Contour Contour Depth Incremental Cumulative Incremental Cumulative Elevation Area (ft) Volume Volume Volume Volume (sq. ft) Avg. End Avg. End Conic Conic (cu. ft) (cu. ft) (cu. ft) (cu. ft) 4,808.90 8 N/A N/A 0.00 N/A 0.00 4,809.00 31 0.10 1.96 1.96 1.83 1.83 4,809.10 65 0.10 4.81 6.77 4.71 6.54 4,809.20 102 0.10 8.31 15.09 8.24 14.79 4,809.30 142 0.10 12.16 27.25 12.11 26.89 Page 3