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HomeMy WebLinkAbout007_Thriftway Stormwater Design Report THRIFTWAY SITE PLAN – STORMWATER DESIGN REPORT October, 2022 #201104 1 TABLE OF CONTENTS REPORT Introduction..........................................................................................................................2 Existing Site & Stormwater.................................................................................................2 Groundwater Considerations ...............................................................................................2 Stormwater Design...............................................................................................................3 Drainage Areas.................................................................................................................3-5 Stormwater Conveyance......................................................................................................5 APPENDICES Appendix A: Drainage Area Map Appendix B: Storm Sewer Facilities Calculations Appendix C: Stormwater Maintenance Plan THRIFTWAY SITE PLAN – STORMWATER DESIGN REPORT October, 2022 #201104 2 INTRODUCTION The proposed Thriftway site plan is located on a 5.036 acre parcel located on the northeast corner of Davis Lane and Baxter Lane in the City of Bozeman. The lot is legally described as the S. 1/2, SW ¼, SW ¼, SW ¼ of Section 35, Certificate of Survey No. 2970, T. 1 S., R. 5 E. of P.M.M.. The site plan consists of a proposed retail space and office building, gas pumps, and associated parking. Stormwater runoff for the site will be directed via site grading, downspouts, storm sewer piping, and curb and gutter to drywells, underground retention chambers and a retention pond. Additionally, an underground detention chamber will receive and treat stormwater runoff in the northwest corner of the site and discharge the runoff to the existing culvert that runs along the west side of the property. EXISTING SITE CONDITIONS The site is currently vacant with natural grass vegetation. The site slopes downhill to the north at approximately 2%. The parcel includes a portion of the Davis Lane right-of-way to the west and a portion of the Baxter Lane right-of-way along the southern boundary. Stormwater from the east portion of the Davis Lane right-of-way currently drains to existing curb and gutter along the east side of Davis Lane. This stormwater then flows to a swale and north to Section Line Ditch, located north of the site. The portion of the Baxter Lane right-of-way along the south side of the property drains to two existing stormwater inlets along the north curb line of Baxter Lane. GROUNDWATER CONSIDERATIONS Three groundwater (GW) monitoring wells were installed across the parcel and have been regularly inspected this past spring to record fluctuations in the groundwater elevation during the typical peak season for groundwater. The GW monitoring results and map are included in Appendix E for reference. The GW depths from the three wells found the seasonal high ground water to be approximately 4.75’ below ground surface. THRIFTWAY SITE PLAN – STORMWATER DESIGN REPORT October, 2022 #201104 3 STORMWATER DESIGN The stormwater facilities have been designed according the City of Bozeman Design Standards and Specifications. The site uses a combination of retention and detention facilities. The stormwater will be conveyed via a combination of site grading, curb and gutter, and storm sewers to the proposed facilities. Retention Facilities The retention facilities for the project were designed to meet the City of Bozeman Design Standards and Specifications. The standards require that retention facilities be required to retain the runoff generated by the 10-year, 2-hour storm. The design storm has an intensity of 0.41 in/hour. Calculations for the drainage area and required retention facilities are included in Appendix B. DRAINAGE AREAS Drainage Area #1 Drainage Area #1 consists of the eastern portion of the Davis Lane right-of-way fronting the property, including the proposed 10’ shared use path and pedestrian ramps at the northeast corner of the Davis Lane and Baxter Lane intersection. A portion of the north drive access and parking lot for the proposed site plan are also included in Drainage Area #1. The stormwater runoff generated by this drainage area will flow to a proposed inlet located at the north end of the northwesterly drive entrance from Davis Lane. This inlet will flow to a proposed underground retention chamber located at the northwest corner of the site. The sizing of proposed Retention Chamber #1 is in Appendix B. Drainage Area #2 Drainage Area #2 consists of a portion of the proposed Thriftway building, a portion of the proposed patio along the southern exposure of the building and a landscaped area to the west of the building. Runoff generated from the drainage area will flow via surface grading and stormwater piping to Drywell #1 located west of the building. The required retention volume for Drainage Area #2 is 228 cf. The proposed drywell has a volume of 259 cf. See Appendix B. THRIFTWAY SITE PLAN – STORMWATER DESIGN REPORT October, 2022 #201104 4 Drainage Area #3 Drainage Area #3 consists of the southeast corner of the proposed Thriftway building and a portion of the landscaping and sidewalks south of the building. The runoff generated by this drainage area be routed to proposed Drywell #2 via site grading and storm sewers tied to the roof downspouts. The required retention volume for Drywell #2 is 204 cf. The proposed volume for the drywell is 259 cf. See Appendix B. Drainage Area #4 Drainage Area #4 consists of the northwest corner of the proposed Thriftway building, and landscaping and sidewalks along the western side of the building. The runoff generated by this area will be routed to proposed Drywell #3 via site grading and storm sewers tied to the roof’s downspouts. The required volume for Drywell #3 is 167 cf. The proposed volume of the drywell is 206 cf. See Appendix B. Drainage Area #5 Drainage Area #5 consists of a portion of the proposed parking lot, sidewalk and adjacent landscaping. The runoff generated by this drainage area will be directed via surface grading to an inlet and StormTech chamber located in the parking lot. The required volume for Retention Chamber #2 is 809 cf. The proposed volume of Retention Chamber #2 is 1,000 cf. Drainage Area #6 Drainage Area #6 consists of the majority of the proposed parking lot and gas pumps, as well as the northeast corner of the proposed Thriftway building. The runoff generated by this drainage area will be directed to an inlet on the east side of Retention Chamber #1 via grading, and curb and gutter. The required volume for Retention Chamber #1 is 4,167 cf. The proposed volume of Retention Chamber #1 is 4,500 cf. THRIFTWAY SITE PLAN – STORMWATER DESIGN REPORT October, 2022 #201104 5 Drainage Area #7 Drainage Area #7 includes the easterly drive access and parking lot. The runoff from the drainage area will sheet flow northerly to a curb cut at the northeast corner of the paving. The runoff will then be directed to proposed Retention Pond #1, located at the north end of the adjacent vacant landscaped area to the east. The proposed pond is 1.5’ deep with 4:1 side slopes. The required volume of the pond is 1,120 cf. The proposed volume is 1,531 cf. See Appendix B. Drainage Area #8 Drainage Area #8 consists of the Baxter Lane right-of-way up to the back of the sidewalk. This area will maintain current drainage patterns by draining at approximately 2% back towards the north curb line of Baxter Lane. Adding the new proposed drive access, and the removal of the existing south drive access will have minimal affect on the runoff generated from this drainage area. Runoff from this area will flow to the two existing storm inlets in the north curb line of Baxter Lane. Drainage Area #9 Drainage Area #9 consists of the small north and eastern portions of the property that will not be contained on site. This area will remain undeveloped and naturally vegetated. No increase in impervious area is proposed for Drainage Area #9. Storm runoff generated by this area will flow north off-site, maintaining current drainage patterns. STORMWATER CONVEYANCE Per the City of Bozeman Design Standards all stormwater conveyance facilities were designed to have capacity for flow rates associated with the 25-year storm event. Time of concentration calculations are included with each drainage area. For smaller drainage areas, the minimum time of concentration of 5-minute was used to calculate flow rates. Manning’s equation for open channel flow was then used to calculate pipe and channel flow for these conveyance facilities. For inlet capacity, the manufacturer’s flow rate calculations using weir analysis was used, with the assumption that 0.25’ of ponding was acceptable at the inlet locations. Calculations for stormwater conveyance are included in Appendix B. APPENDIX A Drainage Area Maps UP APPENDIX B Storm Sewer Facilities Calculations REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft 2 )C * Area Hardscape EX 1 0.95 32353 30735.5495 Landscape EX 1 0.20 187005 37401 Total 219358 68137 A = Area (acres) 5.04 Storm C = Weighted C Factor 0.31 Return (yrs)Cf 2 to 10 1 2. Calculate T c (Pre-Development)11 to 25 1.1 Tc Overland Flow 26 to 50 1.2 Tc = 1.87 (1.1-CCf)D1/2/S1/3 51 to 100 1.25 S = Slope of Basin (%) 1.940 C = Rational Method Runoff Coefficient 0.20 Cf = Frequency Adjustment Factor 1 D = Length of Basin (ft) 324 Tc (Pre-Development) (minutes) 24 3. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.40 (Tc Pre-Development) i = rainfall intensity (in./hr.) 1.15 4. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.) 1.15 (calculated above) A = Area (acres) 5.04 (calculated above) Q = Runoff Rate (Pre-Development) (cfs) 1.16 EXISTING DRAINAGE AREA #1 RUNOFF FROM DA#1 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 2254 451 Hardscape 0.95 16499 15674 Total 18753 16125 A = Area (acres)0.43 C = Weighted C Factor 0.86 2. Calculate Tc (Time to Concentration) of DA 1 Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm Return (yrs)Cf S = Slope of Basin (%) 1.74% 2 to 10 1 C = Rational Method Runoff Coefficient 0.95 11 to 25 1.1 Cf = Frequency Adjustment Factor 1 26 to 50 1.2 D = Length of Basin (ft) 331 51 to 100 1.25 Tc Overland Flow (minutes)4.2 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 (%) 1.74% L = length of gutter (ft) 331 V = mean velocity (ft/s) 3.96 Tc Gutter Flow (minutes) =1.4 Tc Total = 5.6 (5 minute minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.86 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.54 (25-yr storm) A = area (acres) 0.43 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 1.31 (assuming no carry flow) DRAINAGE AREA # 1 RUNOFF VOLUME FROM DA#2 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 1127 225 Hardscape 0.95 3328 3161 Total 4455 3387 A = Area (acres)0.10 C = Weighted C Factor 0.76 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.76 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.10 Q = RUNOFF (cfs)0.03 Vr= REQUIRED VOL (ft3)228 3. Calculate Drywell Volume Void Ratio of Media 30.00% Gravel Offset Dist. From Drywell (ft) 5 Gravel Void Volume Gravel Bed Depth (below MH) 0.00 Gravel Volume (ft3)617.64 Gravel Storage Volume (ft3)185.29 Manhole Volume Manhole Depth (ft) 4.00 Manhole Volume (ft3)73.29 Provided Volume (ft3)259 Drywell #1 4. Calculate Tc (Time to Concentration) of DA 2 Tc Total = 5.0 (Assume 5 minute minimum) 5. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.76 (calculated above) I = .78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.10 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 0.30 (assuming no carry flow) DRAINAGE AREA # 2 RUNOFF VOLUME FROM DA#3 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 1349 270 Hardscape 0.95 2901 2755 Total 4250 3025 A = Area (acres)0.10 C = Weighted C Factor 0.71 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.71 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.10 Q = RUNOFF (cfs)0.03 Vr= REQUIRED VOL (ft3)204 3. Calculate Drywell Volume Void Ratio of Media 30.00% Gravel Offset Dist. From Drywell (ft) 5 Gravel Void Volume Gravel Bed Depth (below MH) 0.00 Gravel Volume (ft3)617.64 Gravel Storage Volume (ft3)185.29 Manhole Volume Manhole Depth (ft) 4.00 Manhole Volume (ft3)73.29 Provided Volume (ft3)259 Drywell #2 4. Calculate Tc (Time to Concentration) of DA 3 Tc Total = 5.0 (Assume 5 minute minimum) 5. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.71 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.10 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 0.27 (assuming no carry flow) DRAINAGE AREA # 3 RUNOFF VOLUME FROM DA#4 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 1456 291 Hardscape 0.95 2306 2191 Total 3762 2482 A = Area (acres)0.09 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) 0.09 Q = RUNOFF (cfs)0.02 Vr= REQUIRED VOL (ft3)167 3. Calculate Drywell Volume Void Ratio of Media 30.00% Gravel Offset Dist. From Drywell (ft) 4 Gravel Void Volume Gravel Bed Depth (below MH) 0.00 Gravel Volume (ft3)443.84 Gravel Storage Volume (ft3)133.15 Manhole Volume Manhole Depth (ft) 4.00 Manhole Volume (ft3)73.29 Provided Volume (ft3)206 Drywell #3 4. Calculate Tc (Time to Concentration) of DA 4 Tc Total = 5.0 (5 minute minimum) 5. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.66 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.09 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 0.22 (assuming no carry flow) DRAINAGE AREA # 4 RUNOFF VOLUME FROM DA#5 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 1512 302 Hardscape 0.95 12315 11699 Total 13828 12002 A = Area (acres)0.32 C = Weighted C Factor 0.87 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.87 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.32 Q = RUNOFF (cfs)0.11 Vr= REQUIRED VOL (ft3)809 Vp = POVIDED VOL (ft3)1000 3. Calculate Tc (Time to Concentration) of DA 5 Tc Total = 5.0 (Assume 5 minute minimum) 4. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.87 (calculated above) I = 0.78Tc-0.64 (in/hr)3.83 (25-yr storm) A = area (acres) 0.32 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 1.05 (assuming no carry flow) DRAINAGE AREA # 5 RUNOFF VOLUME FROM DA#6 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft2 )C * Area Landscape 0.2 10820 2164 Hardscape 0.95 62793 59653 Total 73613 61817 A = Area (acres)1.69 C = Weighted C Factor 0.84 2. Calculate Required Retention Volume Q = CIA V=7200Q C = Weighted C Factor 0.84 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 1.69 Q = RUNOFF (cfs)0.58 Vr= REQUIRED VOL (ft3)4167 Vp = POVIDED VOL (ft3)4500 3. Calculate Tc (Time to Concentration) of DA 6 Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm Return (yrs)Cf S = Slope of Basin (%) 1.44% 2 to 10 1 C = Rational Method Runoff Coefficient 0.95 11 to 25 1.1 Cf = Frequency Adjustment Factor 1 26 to 50 1.2 D = Length of Basin (ft) 509 51 to 100 1.25 Tc Overland Flow (minutes)5.6 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 (%) 1.44% L = length of gutter (ft) 0 V = mean velocity (ft/s) 3.60 Tc Gutter Flow (minutes) =0.0 Tc Total = 5.6 (5 minute minimum) 4. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.84 (calculated above) I = 0.78 Tc-0.64 (in/hr)2.92 (25-yr storm) A = area (acres) 1.69 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 4.14 (assuming no carry flow) DRAINAGE AREA # 6 RUNOFF VOLUME FROM DA#7 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft2 )C * Area Landscape 0.2 49024 9805 Hardscape 0.95 7172 6814 Total 56196 16619 A = Area (acres)1.29 C = Weighted C Factor 0.30 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.30 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 1.29 Q = RUNOFF (cfs)0.16 Vr= REQUIRED VOL (ft3)1120 Vp = POVIDED VOL (ft3)1531 1. Calculate Tc (Time to Concentration) of DA 7 Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm Return (yrs)Cf S = Slope of Basin (%) 2.77% 2 to 10 1 C = Rational Method Runoff Coefficient 0.95 11 to 25 1.1 Cf = Frequency Adjustment Factor 1 26 to 50 1.2 D = Length of Basin (ft) 257 51 to 100 1.25 Tc Overland Flow (minutes)3.2 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 (%) 2.77% L = length of gutter (ft) 0 V = mean velocity (ft/s) 4.99 Tc Gutter Flow (minutes) =0.0 Tc Total = 5.0 (5 minute minimum) 2. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.30 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.14 (25-yr storm) A = area (acres) 1.29 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 1.20 (assuming no carry flow) DRAINAGE AREA # 7 RUNOFF FROM DA#8 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 8729 1746 Hardscape 0.95 18189 17280 Total 26918 19025 A = Area (acres)0.62 C = Weighted C Factor 0.71 2. Calculate Tc (Time to Concentration) of DA 8 Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm Return (yrs)Cf S = Slope of Basin (%) 0.29% 2 to 10 1 C = Rational Method Runoff Coefficient 0.95 11 to 25 1.1 Cf = Frequency Adjustment Factor 1 26 to 50 1.2 D = Length of Basin (ft) 149 51 to 100 1.25 Tc Overland Flow (minutes)5.2 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 (%) 0.29% L = length of gutter (ft) 149 V = mean velocity (ft/s) 1.61 Tc Gutter Flow (minutes) =1.5 Tc Total = 6.7 (5 minute minimum) 3. Calculate Flow (Rational Formula) Q = CIA C = Weighted C Factor 0.71 (calculated above) I = 0.78 Tc-0.64 (in/hr)3.17 (25-yr storm) A = area (acres) 0.62 (calculated above) Q = 25-YEAR FLOW RATE (cfs) 1.38 (assuming no carry flow) DRAINAGE AREA # 8 MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 12 inches d= 11.25529 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.77 2.64 0.29 7.97 6.10 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #1 - 25- YEAR FLOW 1.31 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 6 inches d= 5.627646 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.19 1.32 0.15 5.02 0.96 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #2 - 25- YEAR FLOW 0.30 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 6 inches d= 5.627646 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.19 1.32 0.15 5.02 0.96 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #3 - 25- YEAR FLOW 0.27 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 6 inches d= 5.627646 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.19 1.32 0.15 5.02 0.96 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #4 - 25- YEAR FLOW 0.22 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 12 inches d= 11.25531 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.77 2.64 0.29 7.97 6.10 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #5 - 25- YEAR FLOW 1.05 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D MANNING'S EQUATION FOR PIPE FLOW Project: 201104 Location: Baxter and Davis Lanes By: D. KIRSCH INPUT D= 6 inches d= 5.627646 inches Mannings Formula n= 0.01 mannings coeff q=57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.01 0.19 1.32 0.15 5.02 0.96 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 DRAINAGE AREA #6A - 25- YEAR FLOW 0.14 (cfs)ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d q D Surface Type Concrete pavement, broom finish Drop DownT (ft) 9 Enter UnitsTS (ft)7.5W (ft) 1.5 Enter UnitsSx (ft/ft)0.030Enter UnitsSW (ft/ft)0.063Enter UnitsSL (ft/ft)0.009Enter Unitsa (in) 0.59d (in) 3.83Gutter Flow (cfs) 3.54Gutter Flow (gpm) 1588.29Gutter Velocity (fps) 2.83Grate Style 2'x3' Curb Inlet High Flow Drop DownIntercepted Flow (cfs) 1.958Intercepted Flow (gpm) 878.68Carryover Flow (cfs) 1.581Carryover Flow (gpm) 709.611DISCLAIMER: SAFETY FACTORS ARE NOT INCLUDED. ACTUAL CALCULATIONS SHOULD BE CARRIED OUT AND VERIFIED BY DESIGN ENGINEER TAKING INTO ACCOUNT ALL LOCAL CONDITIONS. FAA RECOMMENDS USING A SAFETY FACTOR OF 1.25 FOR PAVED AREAS AND 2.0 FOR TURF AREAS.  ADS/NYLOPLAST IS NOT RESPONSIBLE FOR MISUSE OF THIS TOOL.Nyloplast Curb & Gutter Inlet Capacity Calculator ‐ Composite Cross SectionEQUATIONS AND CALCULATIONS ARE BASED OFF USDOT/FHWA URBAN DESIGN MANUAL, HYDRAULIC ENGINEERING CIRCULAR NO. 22, THIRD EDITION, PUBLICATION NO. FHWA‐NHI‐10‐009.Curb & Gutter Design InputsMannings Coeffiecient for Street & Pavement Gutters0.016OutputInlet #1 - Double Inlet Calc. below to meet 25 - year flow rate = 1.70 Input Type of Grate 30" Standard Head (ft)0.1 Properties Orifice Flow Area (in)324.00 Orifice Flow Area (ft)2.24 Weir Flow Perimeter (in)93.53 Weir Flow Perimeter (ft)7.79 Solution Capacity (cfs)0.82 Capacity (gpm)368.37 REV 2.1.21 Nyloplast Inlet Capacity Table DISCLAIMER: SAFETY FACTORS ARE NOT INCLUDED IN THESE CALCULATIONS. ACTUAL CALCULATIONS SHOULD BE CARRIED OUT AND VERIFIED BY THE DESIGN ENGINEER TAKING INTO ACCOUNT ALL LOCAL CONDITIONS. NYLOPLAST RECOMMENDS USING A MINIMUM SAFETY FACTOR OF 1.25 FOR PAVED AREAS AND 2.0 FOR TURF AREAS.  ADS/NYLOPLAST IS NOT RESPONSIBLE FOR MISUSE OF THIS TOOL. Inlet #5 - Standard circular 30" Slotted Inlet to meet 25- year flow rate = 0.68 cfs Input Type of Grate 2'x3' Curb Inlet High Flow Head (ft) 0.25 Properties Orifice Flow Area (in)425.88 Orifice Flow Area (ft)2.96 Weir Flow Perimeter (in)124.32 Weir Flow Perimeter (ft)10.36 Solution Capacity (cfs)4.31 Capacity (gpm)1935.38 REV 2.1.21 Nyloplast Inlet Capacity Table DISCLAIMER: SAFETY FACTORS ARE NOT INCLUDED IN THESE CALCULATIONS. ACTUAL CALCULATIONS SHOULD BE CARRIED OUT AND VERIFIED BY THE DESIGN ENGINEER TAKING INTO ACCOUNT ALL LOCAL CONDITIONS. NYLOPLAST RECOMMENDS USING A MINIMUM SAFETY FACTOR OF 1.25 FOR PAVED AREAS AND 2.0 FOR TURF AREAS.  ADS/NYLOPLAST IS NOT RESPONSIBLE FOR MISUSE OF THIS TOOL. Inlet #6 - 2'x3' High Flow Grate to meet 25- year flow rate = 04.49 cfs APPENDIX C Stormwater Maintenance Plan INSPECTION AND MAINTENANCE FOR STORMWATER MANAGEMENT FACILITIES The Property Owner shall be responsible for the maintenance of the stormwater drainage facilities included within S. 1/2, SW 1/4, SW 1/4, SW 1/4 of Sec. 35, Certificate of Survey No. 2970. Storm Water Facilities: 1.Drainage swales slope toward retention and detention ponds to collect storm water runoff and channel it to the retention or detention pond. 2.Pipe Networks convey storm water to different discharge locations underground. 3.Outlets are points where storm water exits a pipe network. 4.Retention Ponds are storm water collection facilities that collect and temporarily store runoff and allow it to infiltrate and evaporate 5.Retention Chambers are underground facilities that collect and temporarily store runoff and allow it to infiltrate 6.Detention Chambers are unground facilities that collect and temporarily store runoff and release stormwater to existing stormwater facilities at a given flow rate 7.Drywells are underground retention facilities that use washed rock to store and infiltrate runoff Post Construction Inspection: 1. Observe that drywells, and catch basins are clear of any material or obstructions in the drainage slots. Inspect these structures to insure proper drainage following a storm event. Immediately identify and remove objects responsible for clogging if not draining properly. Semi-Annual Inspection: 1. Check retention facilities three days following a storm event exceeding ¼ inch of precipitation. Failure for water to percolate within this time period indicates clogging or poor-draining soils. Clear any clogs and replace any poor-draining soils with well- draining gravely soils. 2. Check for grass clippings, litter, and debris in drainage swales, catch basins, dry wells, culverts and retention ponds. Flush and/or vacuum drywells, underground storage chambers or storm water pipes if excessive material is observed in the facilities. Standard Maintenance: 1. Remove sediment and oil/grease from retention facilities. 2. Inspect and remove debris from drainage swales, catch basins, dry wells, and retention ponds. Use a vacuum truck to clean catch basins and dry wells. 3. Monitor health of vegetation and revegetate as necessary to maintain full vegetative cover. 4. Inspect for the following issues: differential accumulation of sediment, drain time, signs of petroleum hydrocarbon contamination (odors, oil sheen in pond water), standing water, trash and debris. Sediment accumulation: In most cases, sediment from a retention pond or underground stormwater chambers does not contain toxins at levels posing a hazardous concern. However, sediments should be tested for toxicants in compliance with current disposal requirements and if land uses in the drainage area include commercial or industrial zones, or if visual or olfactory indications of pollution are noticed. Sediments containing high levels of pollutants should be disposed of in accordance with applicable regulations and the potential sources of contamination should be investigated and contamination practices terminated. Equipment Type/Access: Ponds and underground infiltration systems will be cleaned using vacuum trucks or other equipment. All vacuum trucks will access the site through the proposed drive aisle and parking lot, as well as along Davis Lane and Baxter Lane. Special care should be taken when accessing drywells from Davis Lane and Baxter Lane to prevent damage to existing landscaping and utilities. Cost Estimate: Depending on the amount of rainfall in the given year, the cost to maintain the stormwater infrastructure will vary. It is estimated that the underground stormwater chambers and drywells will need to be have sediment removed once per year, with an estimated cost of $5,000 to do so. The property owner will be responsible for financing the maintenance of the stormwater infrastructure.