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HomeMy WebLinkAboutStormwater Design Report complete INTRODUCTION The proposed Westside Flats project is a residential multi-family development within an existing subdivision. The project will include the extensions of May Fly Street and Dragon Fly Street east into the project to tie into a proposed center drive aisle running north-south, which functions as a drive access and parking area for the site. Nine buildings are proposed for construction along the center drive aisle to create 132 – 2 bedroom apartments in a series of 12-plex and 18-plex buildings. The center drive aisle has proposed perpendicular parking along both sides and has been designed with a 1.5% cross slope (to the east) instead of a standard crowned design. The center drive aisle also generally slopes from south to north at the two east-west connection aisles. The stormwater will be collected in catch curb on the east side of the center drive aisle and perpendicular parking. The stormwater will flow to a series of inlet curb chases. The curb chases will run to storm swales that convey water to a set of retention ponds on the east side of the project. Additional parking areas are also provided along the west side of the property. Generally, these parking areas are graded to a curb chase on the north side of the parking area, where it is conveyed to a stormwater retention pond. Stormwater from the parking area at the north end of the project, in Phase 3, is graded to the north, where it will be conveyed through curb cuts to grass lined storm swales. The stormwater is then conveyed to Retention Pond #4 and Retention Pond #11, which are separated from the existing detention pond on the south side of West Babcock Street. The existing detention pond on the north end of the site is not functioning properly and retains water permanently. The existing detention pond will not be changed with construction of this project. A portion of the site to the north will remain landscaped and not contribute any additional runoff to the existing stormwater infrastructure. STORM SEWER FACILITIES DESIGN Storm sewer facilities were sized for the 25-yr storm using Manning’s Equation. For each inlet, the contributing area, weighted C factor, and time of concentration were calculated. These values were input into Manning’s Equation to check capacity and flow characteristics for curbs chases, storm swales, and curb gutters. All curbs are designed to maintain 0.15’ freeboard per C.O.B. Design Manual Section IV.C.5. For the purposes of this report, each curb chase and swale was named for the associated drainage areas. Curb chase and storm swale sizing calculations are included in Appendix C. RETENTION POND DESIGN All ponds have been sized according to City of Bozeman Design Standards. The proposed retention ponds are sized to capture the entire volume of the 10-year, 2-hour storm event. The site lies in an area of known high groundwater. Appendix D contains groundwater monitoring data from the Norton Ranch Phase 4 Subdivision. Groundwater Monitoring Well #2 from Norton Ranch Phase 4 is approximately 700 feet from the project site and had minimum groundwater depths of approximately 3 feet. This information was used to make the assumption that the Seasonal High Ground Water Level (SHGWL) is greater than 5 feet below existing grade on the site. The stormwater industry guidance recommends 3 feet minimum separation between stormwater facilities and the groundwater table. The proposed retention ponds are conservatively designed to be less than 1.5’ below existing grade to provide approximately 3’ of separation between retention facilities and the groundwater table. Calculations used for sizing each pond can be found in Appendix c. Design pond capacities were calculated using volume surfaces in AutoCAD Civil 3D. Proposed Retention Pond 1 Retention Pond 1 is located along the western edge of the property in Phase 1 of the project. The pond receives runoff from the proposed parking lot north of May Fly Street. The runoff is conveyed via sheet flow and curb and gutter to an outlet chase in the northwest corner of the parking lot. The required pond volume is 394 cubic feet, and the proposed pond volume is 403 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 1 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 2 Retention Pond 2 is located along the western edge of the property in Phase 3 of the project. The pond receives runoff from the proposed parking lot in the northwest corner of Phase 2 of the project and proposed landscaped areas in Phase 3. The runoff is conveyed via sheet flow and curb and gutter to an outlet chase in the northwest corner of the parking lot. The required pond volume is 673 cubic feet, and the proposed pond volume is 843 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 2 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 3 Retention Pond 3 is located along the western edge of the property in Phase 2 of the project. The pond receives runoff from the proposed Building #6 and the landscaped area behind it. The runoff will be conveyed via gutters, downspouts and landscaping swales to the pond. The required pond volume is 339 cubic feet, and the proposed pond volume is 463 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 3 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 4 Retention Pond 4 is located on the northwestern part of the project in Phase 3 of the project. The pond receives runoff from the proposed Building #9, the large parking lot in front of Building 9 and associated landscaping areas. The runoff will be conveyed via gutters, downspouts and curb chases to the pond. The required pond volume is 2,162 cubic feet, and the proposed pond volume is 2,487 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 4 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 5 Retention Pond 5 is located along the eastern side of the property in Phase 3 of the project. The pond receives runoff from the proposed drive aisle, proposed Building #7 and Building #8 and the landscaped area behind it. The runoff will be conveyed via curb and gutter, a curb chase and a storm swale to the retention pond. The required pond volume is 2,153 cubic feet, and the proposed pond volume is 2,259 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 5 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 6 Retention Pond 6 is located along the eastern side of the property in Phase 2 of the project. The pond receives runoff from the proposed drive aisle, proposed Building #4 and the landscaped area behind it, as well as a portion of Building #5. The runoff will be conveyed via curb and gutter, a curb chase and a storm swale to the retention pond. The required pond volume is 1658 cubic feet, and the proposed pond volume is 1,939 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 6 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 7 Retention Pond 7 is located along the eastern side of the property in Phase 1 of the project. The pond receives runoff from the proposed drive aisle, proposed Building #2 and the landscaped area behind it, as well as a portion of Building #3. The runoff will be conveyed via curb and gutter, a curb chase and a storm swale to the retention pond. The required pond volume is 1,686 cubic feet, and the proposed pond volume is 2,079 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 7 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 8 Retention Pond 8 is located along the western side of the property in Phase 1 of the project. The pond receives runoff from the proposed drive access from May Fly Street, portion of proposed Building #3 and the landscaped area behind it. The runoff will be conveyed via gutter, landscaping swales to the retention pond. The required pond volume is 607 cubic feet, and the proposed pond volume is 639 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 8 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 9 Retention Pond 9 is located along the western side of the property in Phase 1 of the project. The pond receives runoff from the proposed main drive aisle, the southernmost parking lot, proposed Building #1 and the landscaped area behind it. The runoff will be conveyed via gutter, landscaping swales to the retention pond. The required pond volume is 2,024 cubic feet, and the proposed pond volume is 2,111 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 9 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 10 Retention Pond 10 is located along the eastern side of the property in Phase 2 of the project. The pond receives runoff from the proposed main drive aisle, the southernmost parking lot, proposed Building #5 and the landscaped area behind it. The runoff will be conveyed via gutter, landscaping swales to the retention pond. The required pond volume is 1,391 cubic feet, and the proposed pond volume is 1,532 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 10 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Proposed Retention Pond 11 Retention Pond 11 is located along the northern side of the main parking Aisle in Phase 3 of the project. The pond receives runoff from the main parking aisle. The runoff will be conveyed via gutter to the retention pond. The required pond volume is 418 cubic feet, and the proposed pond volume is 593 cubic feet. The proposed pond is 1.5’ deep with 4:1 side slopes. The bottom of Retention Pond 11 is less than 1.5’ below existing grade to avoid the Seasonal High Groundwater Level (SHGWL). Retention Pond Summary Pond Drainage Area Pond Depth (ft) Required Storage Volume (cf) Provided Storage Volume (cf) 1 1A & 1B 1.5 394 403 2 2A & 2B 1.5 673 843 3 3A 1.5 339 463 4 4A & 4B 1.5 2,162 2,487 5 5A & 5B 1.5 2,153 2,259 6 6A & 6B 1.5 1,658 1,939 7 7A, 7B, & 7C 1.5 1,686 2,079 8 8A & 8B 1.5 607 639 9 9A & 9C 1.5 2,024 2,111 10 10A & 10B 1.5 1,391 1,532 11 11A 1.5 418 593 G:\C&H\18\180820\Design Reports\Stormwater\Westside Flats Master Stormwater Plan\180820_ Westside Flats Stormwater Design Report R1.Docx APPENDIX A DRAINAGE AREA MAP APPENDIX B DRAINAGE AREA CALULATIONS DRAINAGE AREA # 1A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 1626 325 Hardscape 0.95 0 0 Total 1626 325 A = Area (acres) 0.04 C = Weighted C Factor 0.20 DRAINAGE AREA # 1B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 205 41 Hardscape 0.95 5732 5445 Total 5937 5486 A = Area (acres) 0.14 C = Weighted C Factor 0.92 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.94 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 99 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.30 Tc Total = 5.00 (5 mimimum) DRAINAGE AREA # 2A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 2909 582 Hardscape 0.95 326 310 Total 3235 892 A = Area (acres) 0.07 C = Weighted C Factor 0.28 DRAINAGE AREA # 2B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 4219 844 Hardscape 0.95 8631 8200 Total 8631 8200 A = Area (acres) 0.20 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.44 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 70 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.16 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.64% L = length of gutter (ft) 64 V = mean velocity (ft/s) 2.40 Tc Gutter Flow (minutes) =0.44 Tc Total = 5.00 (5 minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.95 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.20 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 0.72 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0064 Q = PROVIDED GUTTER CAPACITY (cfs) 2.97 DRAINAGE AREA # 3A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 7828 1566 Hardscape 0.95 3611 3430 Total 11439 4996 A = Area (acres) 0.26 C = Weighted C Factor 0.44 DRAINAGE AREA # 4A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 10588 2118 Hardscape 0.95 3612 3431 Total 14200 5549 A = Area (acres) 0.33 C = Weighted C Factor 0.39 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.6 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 54 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.17 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0100 L = length of gutter (ft) 184 V = mean velocity (ft/s) 3.00 Tc Gutter Flow (minutes) =1.02 Tc Total = 5.00 (5 minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.39 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.33 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 0.49 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0100 Q = PROVIDED GUTTER CAPACITY (cfs) 3.72 DRAINAGE AREA #4B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 1951 390 Hardscape 0.95 27322 25956 Total 29273 26346 A = Area (acres) 0.67 C = Weighted C Factor 0.90 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 25 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 20 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)0.29 Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 5.11 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.20 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 12 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)3.31 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0130 L = length of gutter (ft) 145 V = mean velocity (ft/s) 3.42 Tc Gutter Flow (minutes) =0.71 Tc Total = 5.00 (5 minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.90 (calculated above) I = 0.78 Tc-0.64 (in/hr)5.75 (25-yr storm) A = area (acres) 0.67 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 3.48 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0130 Q = PROVIDED GUTTER CAPACITY (cfs) 4.24 DRAINAGE AREA # 5A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 21137 4227 Hardscape 0.95 4815 4574 Total 25952 8801 A = Area (acres) 0.60 C = Weighted C Factor 0.34 DRAINAGE AREA #5B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 3690 738 Hardscape 0.95 23405 22235 Total 27095 22973 A = Area (acres) 0.62 C = Weighted C Factor 0.85 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 25 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 19 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)0.28 Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.3 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 75 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.23 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0170 L = length of gutter (ft) 449 V = mean velocity (ft/s) 3.91 Tc Gutter Flow (minutes) =1.91 Tc Total = 5.00 (5 Minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.85 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.62 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 2.02 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0170 Q = PROVIDED GUTTER CAPACITY (cfs) 4.85 DRAINAGE AREA # 6A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 15808 3162 Hardscape 0.95 2337 2220 Total 18145 5381 A = Area (acres) 0.42 C = Weighted C Factor 0.30 DRAINAGE AREA # 6B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 3195 639 Hardscape 0.95 19422 18451 Total 22617 19090 A = Area (acres) 0.52 C = Weighted C Factor 0.84 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.03 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 84 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.35 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0150 L = length of gutter (ft) 133 V = mean velocity (ft/s) 3.67 Tc Gutter Flow (minutes) =0.60 Tc Total = 5.00 (5 Minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.84 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.52 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 1.68 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0150 Q = PROVIDED GUTTER CAPACITY (cfs) 4.55 DRAINAGE AREA # 7A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 3611 3430 Landscape 0.2 11719 2344 Total 15330 5774 A = Area (acres) 0.35 C = Weighted C Factor 0.38 DRAINAGE AREA # 7B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 19357 18389 Landscape 0.2 3609 722 Total 22965 19111 A = Area (acres) 0.53 C = Weighted C Factor 0.83 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.3 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 137 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.66 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0156 L = length of gutter (ft) 57 V = mean velocity (ft/s) 3.74 Tc Gutter Flow (minutes) =0.25 Tc Total = 5.00 (5 Minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.83 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.53 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 1.68 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0156 Q = PROVIDED GUTTER CAPACITY (cfs) 4.64 DRAINAGE AREA # 7C 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 2305 2190 Landscape 0.2 594 119 Total 2899 2309 A = Area (acres) 0.07 C = Weighted C Factor 0.80 DRAINAGE AREA # 8A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 6301 1260 Hardscape 0.95 3611 3430 Total 9912 4691 A = Area (acres) 0.23 C = Weighted C Factor 0.47 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.76 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.29 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 277 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)20.13 Tc Total = 20.13 DRAINAGE AREA # 8B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Landscape 0.2 1769 354 Hardscape 0.95 4123 3917 Total 5892 4271 A = Area (acres) 0.14 C = Weighted C Factor 0.72 DRAINAGE AREA # 9A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area LANDSCAPE 0.2 9760 1952 HARDSCAPE 0.95 2407 2287 Total 12167 4239 A = Area (acres) 0.28 C = Weighted C Factor 0.35 DRAINAGE AREA # 9B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area LANDSCAPE 0.2 6609 1322 HARDSCAPE 0.95 24215 23004 Total 30824 24326 A = Area (acres) 0.71 C = Weighted C Factor 0.79 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.4 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 119 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.52 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0178 L = length of gutter (ft) 74 V = mean velocity (ft/s) 4.00 Tc Gutter Flow (minutes) =0.31 Tc Total = 5.00 (5 Minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.79 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.71 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 2.14 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0178 Q = PROVIDED GUTTER CAPACITY (cfs) 4.96 DRAINAGE AREA # 10A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area LANDSCAPE 0.2 2602 520 HARDSCAPE 0.95 15287 14522 Total 17888 15043 A = Area (acres) 0.41 C = Weighted C Factor 0.84 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.7 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 120 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.72 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0100 L = length of gutter (ft) 119 V = mean velocity (ft/s) 3.00 Tc Gutter Flow (minutes) =0.66 Tc Total = 5.00 (5 Minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.84 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.41 (calculated above) Q = REQUIRED GUTTER CAPACITY (cfs) 1.32 (assuming no carry flow) PROVIDED GUTTER CAPACITY 1. Calculate Gutter Capacity @ 0.15' Below Top of Curb Q = (1.486/n)AR2/3 S1/2 n = Mannings Coefficient 0.013 A = Area (ft2)1.24 (0.15' below top of curb) P = Wetted perimeter (ft) 9.23 (0.15' below top of curb) R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0100 Q = PROVIDED GUTTER CAPACITY (cfs) 3.72 DRAINAGE AREA # 10B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area LANDSCAPE 0.2 16010 3202 HARDSCAPE 0.95 2407 2287 Total 18418 5489 A = Area (acres) 0.42 C = Weighted C Factor 0.30 DRAINAGE AREA # 11A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area LANDSCAPE 0.2 1647 329 HARDSCAPE 0.95 6151 5844 Total 7798 6173 A = Area (acres) 0.18 C = Weighted C Factor 0.79 APPENDIX C POND SIZING AND STORM SEWER FACILITIES CALCULATIONS RETENTION POND #1 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 1A 0.20 1626 325 Hardscape 1A 0.95 0 0 Landscape 1B 0.20 205 41 Hardscape 1B 0.95 5732 5445 Total 7562 5811 C=Weighted C Factor 0.77 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.77 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.17 Q = runoff (cfs) 0.05 V = REQUIRED VOL (ft3)394 Pond Storage Volume (ft3)403 CHASE 1 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 1A 0.20 1626 325 Hardscape 1A 0.95 0 0 Landscape 1B 0.20 205 41 Hardscape 1B 0.95 5732 5445 Total 7562 5811 A = Area (acres) 0.17 C = Weighted C Factor 0.77 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #1B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.77 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.17 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 0.51 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #1 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #2 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 2A 0.20 2909 582 Hardscape 2A 0.95 326 310 Landscape 2B 0.20 4218.70 843.74 Hardscape 2B 0.95 8631 8200 Total 16085 9935 C=Weighted C Factor 0.62 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.62 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.37 Q = runoff (cfs) 0.09 V = REQUIRED VOL (ft3)673 Pond Storage Volume (ft3)843 CHASE 2 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 2A 0.20 2909 582 Hardscape 2A 0.95 326 310 Landscape 2B 0.20 4219 844 Hardscape 2B 0.95 8631 8200 Total 16085 9935 A = Area (acres) 0.37 C = Weighted C Factor 0.62 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #2B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.62 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.37 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 0.87 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #2 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #3 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 3A 0.20 7828 1566 Hardscape 3A 0.95 3611 3430 Total 11439 4996 C=Weighted C Factor 0.44 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.44 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.26 Q = runoff (cfs) 0.05 V = REQUIRED VOL (ft3)339 Pond Storage Volume (ft3)463 RETENTION POND #4 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft2 )C * Area Landscape 4A 0.20 10588 2118 Hardscape 4A 0.95 12393 11773 Landscape 4A 0.20 1951 390 Hardscape 4A 0.95 18541 17614 Total 43474 31895 C=Weighted C Factor 0.73 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.73 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 1.00 Q = runoff (cfs) 0.30 V = REQUIRED VOL (ft3)2162 Pond Storage Volume (ft3)2,487 CHASE 4A 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 4A 0.20 10588 2118 Hardscape 4A 0.95 12393 11773 Landscape 4B 0.20 1951 390 Hardscape 4B 0.95 18541 17614 Total 43474 31895 A = Area (acres) 1.00 C = Weighted C Factor 0.73 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #4A) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.73 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 1.00 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 2.80 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #4A Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1.5 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.75 2.50 0.30 6.27 4.71 6.27 4.71 T = 1.50 Low N High N d w z 11 z T Clear Data Entry Cells MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Swale #4A Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 4 Mannings Formula z (sideslope)= 4 w (btm width, ft)= 0 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.75 R = A/P S (slope, ft/ft) 0.08 A = cross sectional area n low =0.035 P= wetted perimeter n high =0.035 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.75 2.25 6.18 0.36 6.12 13.77 6.12 13.77 T = 6.00 Low N High N d w z 11 z T Clear Data Entry Cells CHASE 4B 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 4B 0.20 1951 390 Hardscape 4B 0.95 18541 17614 Total 20492 18005 A = Area (acres) 0.47 C = Weighted C Factor 0.88 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #4B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.88 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.47 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 1.58 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #4B Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #5 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Landscape 5A 0.2 21137 4227 Hardscape 5A 0.95 4815 4574 Landscape 5B 0.2 3690 738 Hardscape 5B 0.95 23405 22235 Total 53046 31774 C=Weighted C Factor 0.60 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.60 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 1.22 Q = runoff (cfs) 0.30 V = REQUIRED VOL (ft3)2153 Pond Storage Volume (ft3)2,259 CHASE 5 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 5A 0.20 21137 4227 Hardscape 5A 0.95 4815 4574 Landscape 5B 0.20 3690 738 Hardscape 5B 0.95 23405 22235 Total 53046 31774 A = Area (acres) 1.22 C = Weighted C Factor 0.60 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #5B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.60 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 1.22 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 2.79 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #5 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Swale #5 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 4 Mannings Formula z (sideslope)= 4 w (btm width, ft)= 0 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.025 A = cross sectional area n low =0.035 P= wetted perimeter n high =0.035 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 1.00 4.12 0.24 2.61 2.61 2.61 2.61 T = 4.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #6 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 6A 0.20 15808 3162 Hardscape 6A 0.95 2337 2220 Landscape 6B 0.20 3195 639 Hardscape 6B 0.95 19422 18451 Total 40761 24471 C=Weighted C Factor 0.60 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.60 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.94 Q = runoff (cfs) 0.23 V = REQUIRED VOL (ft3)1658 Pond Storage Volume (ft3)1,939 CHASE 6 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 6A 0.20 15808 3162 Hardscape 6A 0.95 2337 2220 Landscape 6B 0.20 3195 639 Hardscape 6B 0.95 19422 18451 Total 40761 24471 A = Area (acres) 0.94 C = Weighted C Factor 0.60 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #5B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.60 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.94 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 2.15 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #6 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #7 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft2 )C * Area Hardscape 7A 0.95 3611 3430 Landscape 7A 0.2 11719 2344 Hardscape 7B 0.95 19357 18389 Landscape 7B 0.2 3609 722 Hardscape 7C 0.95 2305 2190 Landscape 7C 0.2 594 119 Total 38295 24885 C=Weighted C Factor 0.65 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.65 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.88 Q = runoff (cfs) 0.23 V = REQUIRED VOL (ft3)1686 Pond Storage Volume (ft3)2,079 CHASE 7 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Hardscape 7A 0.95 3611 3430 Landscape 7A 0.2 11719 2344 Hardscape 7B 0.95 19357 18389 Landscape 7B 0.2 3609 722 Hardscape 7C 0.95 2305 2190 Landscape 7C 0.2 594 119 Total 38295 24885 A = Area (acres) 0.88 C = Weighted C Factor 0.65 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #7B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.65 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.88 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 2.19 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #7 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Swale #7 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 4 Mannings Formula z (sideslope)= 4 w (btm width, ft)= 0.5 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.0097 A = cross sectional area n low =0.035 P= wetted perimeter n high =0.035 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 1.25 4.62 0.27 1.75 2.19 1.75 2.19 T = 4.50 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #8 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 8A 0.20 6301 1260 Hardscape 8A 0.95 3611 3430 Landscape 8B 0.20 1769 354 Hardscape 8B 0.95 4123 3917 Total 15804 8961 C=Weighted C Factor 0.57 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.57 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.36 Q = runoff (cfs) 0.08 V = REQUIRED VOL (ft3)607 Pond Storage Volume (ft3)639 CHASE 8 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area Landscape 8A 0.2 6301 1260 Hardscape 8A 0.95 3611 3430 Landscape 8B 0.2 1769 354 Hardscape 8B 0.95 4123 3917 Total 15804 8961 A = Area (acres) 0.36 C = Weighted C Factor 0.57 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.34 (DA #8A) i = rainfall intensity (in./hr.) 1.57 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.57 (calculated above) i = rainfall intensity (in./hr.) 1.57 (calculated above) A = Area (acres) 0.36 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 0.32 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #8 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #9 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area LANDSCAPE 9A 0.20 9760 1952 HARDSCAPE 9A 0.95 2407 2287 LANDSCAPE 9B 0.20 6609 1322 HARDSCAPE 9B 0.95 24215 23004 Total 42991 28565 C=Weighted C Factor 0.66 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.66 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.99 Q = runoff (cfs) 0.27 V = REQUIRED VOL (ft3)1936 Pond Storage Volume (ft3)2,111 CHASE 9 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area LANDSCAPE 9A 0.2 9760 1952 HARDSCAPE 9A 0.95 2407 2287 LANDSCAPE 9B 0.2 6609 1322 HARDSCAPE 9B 0.95 24215 23004 Total 42991 28565 A = Area (acres) 0.99 C = Weighted C Factor 0.66 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #9B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.66 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.99 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 2.51 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Chase #9 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Swale #9 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 4 Mannings Formula z (sideslope)= 4 w (btm width, ft)= 0 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.75 R = A/P S (slope, ft/ft) 0.005 A = cross sectional area n low =0.035 P= wetted perimeter n high =0.035 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.75 2.25 6.18 0.36 1.53 3.44 1.53 3.44 T = 6.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #10 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area LANDSCAPE 10A 0.20 2602 520 HARDSCAPE 10A 0.95 15287 14522 LANDSCAPE 10B 0.20 16010 3202 HARDSCAPE 10B 0.95 2407 2287 Total 36306 20532 C=Weighted C Factor 0.57 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.57 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.83 Q = runoff (cfs) 0.19 V = REQUIRED VOL (ft3)1391 Pond Storage Volume (ft3)1,532 CHASE 10 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2 )C * Area LANDSCAPE 10A 0.2 2602 520 HARDSCAPE 10A 0.95 15287 14522 LANDSCAPE 10B 0.2 16010 3202 HARDSCAPE 10B 0.95 2407 2287 Total 36306 20532 A = Area (acres) 0.83 C = Weighted C Factor 0.57 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #10B) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.57 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.83 (calculated above) Q = 25-yr Pipe Flow Rate (cfs) 1.80 MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Curb #10 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 0 Mannings Formula z (sideslope)= 0 w (btm width, ft)= 1 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.5 R = A/P S (slope, ft/ft) 0.015 A = cross sectional area n low =0.013 P= wetted perimeter n high =0.013 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.5 0.50 2.00 0.25 5.56 2.78 5.56 2.78 T = 1.00 Low N High N d w z 11 z T Clear Data Entry Cells MANNING'S EQUATION for OPEN CHANNEL FLOW Storm Swale #10 Project: Westside Flats Location: Bozeman, MT By: AMK Date: 5/19/2020 Chk By: Date: INPUT z (sideslope)= 4 Mannings Formula z (sideslope)= 4 w (btm width, ft)= 0 Q = (1.486/n)ARh2/3S1/2 d (depth, ft)= 0.75 R = A/P S (slope, ft/ft) 0.0075 A = cross sectional area n low =0.035 P= wetted perimeter n high =0.035 S = slope of channel V = (1.49/n)Rh2/3S1/2 n = Manning's roughness coeffiQ = V x A Depth, ft Area, sf Wetted Perimete r, ft Hydraulic Radius, ft Velocity, fps Flow, cfs Velocity, fps Flow, cfs 0.75 2.25 6.18 0.36 1.87 4.22 1.87 4.22 T = 6.00 Low N High N d w z 11 z T Clear Data Entry Cells RETENTION POND #11 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft2 )C * Area Landscape 11A 0.20 1647 329 Hardscape 11A 0.95 6151 5844 Total 7798 6173 C=Weighted C Factor 0.79 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.79 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.18 Q = runoff (cfs) 0.06 V = REQUIRED VOL (ft3)418 Pond Storage Volume (ft3)593 APPENDIX D GROUNDWATER MONITORING DATA FALLON STREETWATER LILY DRIVEMAY FLY STREETDRAGON FLY STREETWSF SITE Project Engineer:Matt H Project: Well Information:bgs = below ground surface ags = above ground surface MW-1 MW-2 MW-3 MW-4 10'10'10'10' 0.58 1.71 0.71 0.92 Groundwater Information: MW-1 MW-2 MW-3 MW-4 02/14/18 6.81 6.29 4.20 4.38 03/13/18 6.94 6.39 4.20 4.34 04/13/18 6.10 5.10 3.12 3.30 05/11/18 6.87 6.36 4.20 4.35 05/25/18 6.78 6.18 4.14 4.31 06/08/18 6.99 6.62 4.37 4.54 06/22/18 6.30 6.51 4.48 4.60 07/06/18 8.64 8.21 5.91 6.10 07/20/18 7.49 7.32 4.85 5.10 08/03/18 7.47 7.32 4.85 5.21 08/17/18 7.57 7.10 5.00 5.21 08/30/18 7.15 6.82 4.50 4.70 09/14/18 7.25 6.85 4.65 4.80 Monitor Well Data Project Number:161140 Norton East Ranch Subdivision, Phase 4 Project Location:Bozeman Well ID Well Depth (feet-bgs) Top of Well (feet-ags) Date Depth to Ground Water (feet-bgs) BB+z z2:1 Δσ EtBqH DCompressible soil layerRigid soil layer