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Home My WebLink AboutCC - Storm Drainage Calcs McKay Farm Subdivision Meridian, ID March 13, 2025 Stormwater Drainage Report 110 u �' y 0 OF 7• 0 v;' TREASURE VALLEY CIVIL AND DESIGN SITE LOCATION The project site is located along the west side of S. Eagle Road and 350 feet south of E. Taconic Drive in the City of Meridian, in the SE 1/4 of Section 32, Township 3 North, Range 1 East, Boise Meridian. EXISTING CONDITIONS The approximately 9.5 acre project site is partially developed as part of the adjacent subdivision to the north. The area has been rough graded and slopes down-gradient to the north at slopes less than 2%. PROPOSED SITE IMPROVEMENTS The proposed improvements include the construction of 36 residential lots, 8 common lots, and associated streets, sidewalks, and infrastructure. DRAINAGE DESIGN CONCEPT The project consists of 10 catchments, labeled Al, A2, B1, B2, B3, 134, C, D, E, and F. Stormwater collected in catchment Al, A2, 131, 132, B3, and B4 are public storm drain systems. Stormwater collected in catchments C, D, E, and F are private storm drain systems. CALCULATION METHODS The site was divided into catchment areas based on the proposed grading design. These catchment areas were analyzed using the rational method to estimate the peak runoff rates in accordance with ACHD Policy Manual Sections 8000 and 8200. Peak storage volumes were based on the 100-year, 1-hour design storm event of 0.96 inches per hour. Peak flow rates and stormwater quality flow rates were calculated for each basin based on the 100-year and 25-year design storms, respectively. The time of concentration for each basin was used as the design storm duration to calculate both the peak flow and stormwater quality flow rates. Time of concentration values were calculated as a combination of sheet flow from the lots to the road section and gutter flow along the road. Specific equations are shown in the attached drainage calculations. The catchment areas are shown on the Drainage Plan. Calculations are included with this report for all catchment areas. SOIL CONDITIONS The Final Geotechnical Engineering Report prepared by Materials Testing & Inspection (MTI) for this site was done on September 4, 2019. Recommendations for street sections are included in the report as well as reported groundwater for all test pits. MTI estimates groundwater to be greater than 4 ft throughout the year. In the event that either groundwater or rock is encountered other than expected during subsurface investigation or construction, the engineer shall be contacted to revise the design based upon field conditions. An infiltration rate of 1.5 in/hr was used for design as required by ACHD Policy Manual. Dry Creek Phase 10 Drainage Study i Treasure Valley Civil and Design ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment Area A 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 34,841 26,056 Acres 1.40 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpe.k 1.80 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 2,416 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 1,510 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 242 ft' concrete 0.95 Primary Treatment/StorageBasin V 2,174 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 2,416 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_A-ACHD_SD_CALCS 3/20/2025,3:13 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment Area A 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 1.40 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 2,416 ft3 0%Sediment 8 Set Total Design Width of All Drain Rock W 29.0 ft 9 Set Total Design Depth of All Drain Rock D 4.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 51.4 Oft 15 Calculate Design Length L 47 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 47 ft 17 Variable Infiltration Window W SWW 29.0 ft 18 Time to Drain 9.97 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 47 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_A-ACHD_SD_CALCS 4/2/2025,9:43 AM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchments BS&B2 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 77,089 27,092 Acres 2.39 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 1 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpe.k 3.09 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 4,133 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 2,583 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 413 ft' concrete 0.95 Primary Treatment/StorageBasin V 3,720 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 4,133 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_B-ACHD_SD_CALCS 3/20/2025,3:23 PM Version 10.5,November 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchments B3&B4 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 5,761 24,559 Acres 0.70 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpe.k 0.90 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 1,203 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 752 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 120 ft' concrete 0.95 Primary Treatment/StorageBasin V 1,082 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 1,203 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_B3&B4-ACHD_SD_CALCS 3/20/2025,3:34 PM Version 10.5,November 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchments Bl,B2,B3,&B4 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 34,841 26,056 77,089 27,092 5,761 24,559 Acres 4.49 6 Determine the Weighted Runoff Coefficient(C) 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.09 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User calculate min 10 Min. Estimated Runoff Coefficients for Various Surface - Type of Surface Runoff Coefficients N 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in/hr Business Downtown areas 0.70-0.95 y Calculate the Post-Development peak discharge(QPeak) Qpe.k 1.03 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 1,382 ft Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 864 ft' Heavy areas 0.90 Parks,Cemeteries 0.10-0.25 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 138 ft' Concrete 0.95 Primary Treatment/StorageBasin V 1,244 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 1,382 ft' Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 0. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\ACHD_SD_CALCS_032025 3/20/2025,12:56 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchments B1,B2,B3,&B4 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 3.09 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 5,336 ft3 o%Sediment 8 Set Total Design Width of All Drain Rock W 27.0 ft 9 Set Total Design Depth of All Drain Rock D 4.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 47.9 Oft 15 Calculate Design Length L 111 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 111 ft 17 Variable Infiltration Window W SWW 27.0 ft 18 Time to Drain 9.97 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 111 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_B1,B2,B3,&B4-ACHD_SD_CALCS 4/2/2025,10:01 AM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment C 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 15,964 Acres 0.37 6 Determine the Weighted Runoff Coefficient(C) 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) QpeA 0.47 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 633 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 396 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 63 ft' concrete 0.95 Primary Treatment/StorageBasin V 570 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 633 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_C-ACHD_SD_CALCS 3/20/2025,3:44 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment C 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 0.37 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 633 ft3 o%Sediment 8 Set Total Design Width of All Drain Rock W 5.0 ft 9 Set Total Design Depth of All Drain Rock D 4.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 9.0 Oft 15 Calculate Design Length L 70 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 70 ft 17 Variable Infiltration Window W SWW 5.0 ft 18 Time to Drain 9.7 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 70 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_C-ACHD_SD_CALCS 4/2/2025,10:03 AM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment D 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 12,681 Acres 0.29 6 Determine the Weighted Runoff Coefficient(C) 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.50 7 User Calculate Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"t Business Downtown areas 0.70-0.95 Hydraulic Urban neighborhoods 0.50-0.70 Radius Flow Residential Intercept A/Wet Velocity V Flow Time Single Family 0.35-0.50 Multi-family 0.60-0.75 ID Pipe Size(in) Slope(ft/ft) Coeff. Length Manning n Perm (fps) (min) Residential(rural) 0.25-0.40 Segment 1:Pipe Flow Apartment Dwelling Areas 0.70 a Industrial and Commercial Light areas 0.80 Heavy areas 0.90 Segment 2:Gutter Shallow Concentrated Flow Parks,Cemeteries 0.1010-0.25 b 0.005 0.619 980 1.4 11.4 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 Segment 3:Overland Sheet Flow By TR-55,<300-ft c 0.003 80 0.240 1.9 41.6 Computed Tc= 53.0 User-Entered Tc= 47.8 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 1.07 in/hr 9 Calculate the Post-Development peak discharge(OPeak) Opeak 0.16 cfs 10 Calculate total runoff vol(V)(for sizing primary storage) V 503 ft V=Ci(Tc=60)Ax3600 11 Calculate Volume of Runoff Reduction Vrr Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 314 ft' 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 50 ft' Concrete 0.95 Primary Treatment/StorageBasin V 453 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 503 ft' Fields:sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0.. Steep:>6% 0.13 0.18 0.23 0.. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_D-ACHD_SD_CALCS 3/20/2025,3:47 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment D 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 0.29 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 503 ft3 0%Sediment 8 Set Total Design Width of All Drain Rock W 5.0 ft 9 Set Total Design Depth of All Drain Rock D 2.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 5.0 Oft 15 Calculate Design Length L 100 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 100 ft 17 Variable Infiltration Window W SWW 5.0 ft 18 Time to Drain 5.4 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 100 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_D-ACHD_SD_CALCS 4/2/2025,10:05 AM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment E 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 12,059 Acres 0.28 6 Determine the Weighted Runoff Coefficient(C) 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) QpeA 0.36 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 478 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 299 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 48 ft' concrete 0.95 Primary Treatment/StorageBasin V 431 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 478 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_E-ACHD_SD_CALCS 3/20/2025,3:50 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment E 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 0.28 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 478 ft3 0%Sediment 8 Set Total Design Width of All Drain Rock W 5.0 ft 9 Set Total Design Depth of All Drain Rock D 3.5 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 8.0 Oft 15 Calculate Design Length L 60 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 60 ft 17 Variable Infiltration Window W SWW 5.0 ft 18 Time to Drain 8.7 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 60 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_E-ACHD_SD_CALCS 4/2/2025,10:07 AM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. arge Rate�ational M�!Slated for Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment F 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 11,771 Acres 0.27 6 Determine the Weighted Runoff Coefficient(C) 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.50 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate to Min. Estimated Runoff Coefficients for Various Surface min - Type of Surface Runoff Coefficients"( 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpe.k 0.35 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 467 ft3 Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 292 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0.20-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 47 ft' concrete 0.95 Primary Treatment/StorageBasin V 420 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel 0.75 Volume Without Sediment Factor(See BMP 20 Tab) V 467 ft3 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_F-ACHD_SD_CALCS 3/20/2025,3:53 PM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Catchment F 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV _ QV TR55 5 Area A(Acres) 0.27 acres 6 Approved discharge rate(if applicable) cfs 7 Is Seepage Bed in Common Lot? Yes V 467 ft3 0%Sediment 8 Set Total Design Width of All Drain Rock W 5.0 ft 9 Set Total Design Depth of All Drain Rock D 3.5 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 8.0 Oft 15 Calculate Design Length L 58 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 58 ft 17 Variable Infiltration Window W SWW 5.0 ft 18 Time to Drain 8.7 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 58 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum U:\McKay Farm\BHH_Engineering\Construction_Drawings\Storm_Drainage\Catchment_F-ACHD_SD_CALCS 4/2/2025,10:08 AM Version 10.0,May 2018 s SKY MESA COMMONS SKY MESA COMMONS 0 60 120 SUBDIVISION SUBDIVISION o NO. 5 NO. 1 SCALE IN FEET N LEGEND IF PROJECT BOUNDARY i ' CATCHMENT BOUNDARY — — — — — — — SUB—CATCHMENT BOUNDARY F FLOW DIRECTION Al CATCHMENT ID E 1.24 CATCHMENT AREA (AC) SKY MESA 0.28 HIGHLANDS SUBDIVISION Al A2 �i 178.00' B4 SKY MESA 0.56 B2 SUBDIVISION 1 } B3 0.62 N0. 4 0.13 i B1 0.37 a 1.77 i 0 D � 0.29 i 9 m 0 z 9 F5 7 —_ EAGLE ROAD Er.— ———Ef'— ———Ef'— ———-.-: ———F ———EP___——EP—_——_EP—————EP——_——EP—————EP—————EP—————EP __ }EP_———_ ——EP ____EP- %Ep__--_Ep—_� C z z a MCKAY FARM SUBDIVISION 9 TREASURE VALLEY CIVIL AND DESIGN STORM DRAIN CATCHMENT MAP > U 3 7