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HomeMy WebLinkAbout04 Concept Review Response REF #6, #9 112 S Church - Storm ReportSTORMWATER DESIGN REPORT FOR THE DEPOT ON CHURCH BOZEMAN, MONTANA 1/16/2026 Prepared By: Morrison-Maierle, Inc. 2880 Technology Blvd. West P.O. Box 1113 Bozeman, Montana 59771-1113 Engineer: Celine Saucier, P.E. Date: November 14, 2025 File: 10758.002 THE DEPOT ON CHURCH STORMWATER DESIGN REPORT 2 The Depot on Church STORMWATER DESIGN REPORT 1.0 Introduction The purpose of this drainage report is to present a summary of calculations to quantify the stormwater runoff for the new Depot on Church project located in Bozeman, Montana. The project site is located at 112 South Church Avenue and was previously a residential home. The site is approximately 0.304 acres. Improvements associated with the new building include new storm drainage improvements, concrete flatwork, curb and gutter, asphalt paving, and other miscellaneous items and appurtenances. All storm drain runoff generated from the site will be captured with roof drains and routed to an underground detention vault beneath the building. All design criteria and calculations are in accordance with the City of Bozeman Design Standards and Specifications Policy, dated October 2024. 2.0 Hydrology & Hydrogeology The hydrology calculations included in this report use precipitation data from Chapter 6 of the City of Bozeman Design and Construction Standards. Per the attached site specific geotechnical investigation conducted by Rawhide Engineering Inc. dated November 13, 2025, groundwater was not encountered at the depths explored of 9.5 feet below existing grades. The runoff generated from the site and directed to the detention system will have no effect on the ground water levels in the area. The system is a closed vault with an overflow directed to the existing storm drain main in South Church Avenue. 3.0 Existing Stormwater Drainage Conditions The existing house and associated out buildings on the project site have been previously demolished. The existing site is now undeveloped land with no impervious areas remaining. Pre-development stormwater runoff currently is described as sheet flow and pools in closed depressions (low spots) and is ascribed by infiltration as well as evaporation. The existing site generally grades so that the runoff on the west half of the site goes towards South Church Avenue and the runoff on the east half of the site goes towards the alley. The alleyway from Olive to Babcock is extremely compacted gravel base that drains north to Babcock street where it flows into curb inlets. See Appendix A for the pre-development exhibit outlining the existing drainage. Calculations are provided in Appendix C. Table 1 below provides a summary of the existing site drainage. THE DEPOT ON CHURCH STORMWATER DESIGN REPORT 3 Table 1: Existing Site Drainage Summary – Pre-Development Basin Name Runoff Coefficient (C) Total Area (SF) 2-yr Pre- Development Peak Runoff (cfs) 10-yr Pre- Development Peak Runoff (cfs) 100-yr Pre- Development Peak Runoff (cfs) Existing Basin #1 0.15 13,312 SF 0.10 0.18 0.35 4.0 Proposed Stormwater Drainage Conditions Stormwater runoff from the site will be conveyed to an underground detention vault via roof drains and a trench drain system in the garage. Runoff will be captured in an underground vault providing on-site storage. See Appendix B for the post- development exhibit outlining the proposed basin and drainage system. The 100- year storm event was used to evaluate the size of the retention system. Calculations are provided in Appendix C. Table 2 below provides a summary of the proposed site drainage. As a part of the project, the fire department is requesting the alley between the adjacent property to the north to be paved 25’ wide up until the southern property boundary where it will become 16’ wide until Olive Street. Because the existing compacted gravel base is for the most part impervious, the additional paving will have a negligible impact on runoff to Babcock Street while significantly improving the alley’s overall condition and drivability. Table 2: Proposed Site Drainage Summary – Post-Development Basin Name Runoff Coefficient (C) Total Area (SF) 2-yr Post- Development Peak Runoff (cfs) 10-yr Post- Development Peak Runoff (cfs) 100-yr Post- Development Peak Runoff (cfs) Major Basin #1 0.89 13,312 SF 0.56 1.05 1.86 5.0 Evaluation of Major Storm Flood Risks The proposed site is adjacent to a Zone AE Regulatory Floodway per the City of Bozeman Infrastructure Viewer. The Base Flood Elevation for the site is 4816.20, so the building will be dry-proofed below an elevation of 2-feet above the base flood elevation. 6.0 Underground Retention System Calculations Storm drainage analysis and design is per the City of Bozeman Design Standards. The rational method was utilized for sizing the underground detention vault based on the 100-year, 24-hour storm event and to model and calculate flowrates and runoff volumes. All calculations are included in Appendix C. THE DEPOT ON CHURCH STORMWATER DESIGN REPORT 4 The proposed development site has been designed with one underground detention vault system. There is a proposed off-site connection to the existing 15-inch PVC City of Bozeman storm drain proposed for this site. Drainage from the new building will be routed to the underground detention vault system located on the west side of the site. The underground detention system will utilize a sealed vault to store runoff on site, and it will be equipped with a triplex redundant pump system to release stormwater from the vault at the pre-development rates for the 2-year, 10-year, and 100-year storm (See Table 1) to match historic discharge rates. The triplex pump system is designed to release flows based on the depth of stormwater in the tank. The 2-year pre-development rate will discharge until the depth of stormwater reaches the 10-year event, at which time the pump system will increase the discharge rate to the 10-year pre-development rate. When the vault depth reaches the 100-year level, the pump system will then increase to the 100- year pre-development rate. The pump system will connect to backup generators to ensure the system is still running during a power outage. Emergency alarms will also be implemented in the event of pump failure so that maintenance and replacement can be completed immediately. Flows will be pumped directly to the existing 15-inch storm drain main in South Church Avenue, and a backflow preventer will be installed on the outfall pipe to ensure stormwater does not back up into the building. Table 3: Basin Summary Basin Runoff Coefficient (C) Intensity, i (in/hr) Total Area (acres) 100-yr Post- development Peak Runoff (cfs) Water Quality Volume Required (CF) 100-yr Required Storage with 1.25 Correction (CF) Proposed Storage (CF) See Below 1 0.89 6.09 0.306 1.86 512 2,588 2,600 7.0 Water Quality & Treatment Water Quality Volume = 0.5-in * (1 ft / 12-in) * 12,276 SF Impervious = 512 CF The proposed detention vault facility provides adequate storage for the first 0.5-inch of runoff (see Table 3). Runoff will be routed to the proposed storm drain inlet in the parking lot. The structure will consist of a 2-foot deep sump to allow for sedimentation, and a 12x12x12-inch tee will be placed on the outlet pipe inside the manhole with a cap and vent hole to allow for separation of oils and trash prior to routing to the vault. 8.0 Storm Pipe Calculations THE DEPOT ON CHURCH STORMWATER DESIGN REPORT 5 Storm piping is sized per the City of Bozeman standards. 9.0 Boulder Pit Drain-Down Time The vault provides 2,600 CF of storage. Utilizing the 100-year pre-development rate for the pump system, the drain-down time for the proposed vault is as follows: Drain-Down Time = 2,600 cf / 1.86 cf/s / (1 min/60 s) / (1 hr/60 m) = 0.39 hours (less than the required 72 hours) 10.0 Operation, Inspection, and Maintenance Considerations Duties shall include routine inspection to ensure that sediment, debris, yard waste, and seasonal ice does not impede operation of the storm drain facilities. It is recommended that these inspections occur after major runoff events and monthly throughout the year. 11.0 Summary The stormwater analysis for the proposed Depot on Church was completed using applicable state and local regulations/standards as well as sound engineering practices. The result is a stormwater plan that provides for the conveyance and storage of stormwater runoff while protecting private property, and promoting public safety. 12.0 Appendices Appendix A – Exhibit A – Pre-Development Stormwater Exhibit Appendix B – Exhibit B - Post-Development Stormwater Exhibit Appendix C – Hydraulic Calculations Appendix D – Stormwater Operation and Maintenance Manual Appendix E – Geotechnical Investigation APPENDIX A EXHIBIT A - PRE-DEVELOPMENT STORMWATER EXHIBIT PTVFXXXXXX W W W W W W W W W W W W W W W W W W BFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBPBP BP BP BP BP NGNGNGNGNGNGNGNGNGNGNGNGNGSSSSSSSSSSSSSSSSWSWSWSWSWSBF BF BF BF BF BF BF BF BP BP BP BP BP BP BPBPBTV BTV BTV BTV BTV BTVBTVBTVBTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV NGNGNGNGNGNGNGNGNGS S S S S S S S S S S S S S S S S S SSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSD TWXXXXXXXXOHPOHPOHPOHPOHPEX. 8" PVC SANITARY SEWER MAINEX. 15" PVC STORM DRAIN MAINEX. 8" DUCTILE IRON WATER MAIN 48 1 6 4816 4817481748 1 7 4 8 1 7 4815 48 1 8 4817 48174818 4816 FIGURE NUMBER©PROJECT NO.DRAWN BY:DSGN. BY:APPR. BY:DATE:COPYRIGHT MORRISON-MAIERLE,2025Plotted by jacob zwemke on Nov/14/2025engineers surveyors planners scientistsMorrisonMaierle2880 Technology Blvd WestBozeman, MT 59718406.587.0721www.m-m.netP:\10758 - JBBArch\001 - 112 S.Church\ACAD\Civil\10758.001 - PRE-DEVELOPMENT STORM.dwg 10758.002ATHE DEPOT ON CHURCH112 SOUTH CHURCH AVENUEBOZEMANMONTANAPRE-DEVELOPMENT STORMWATER EXHIBITJAZJAZCMS11/14/2510205100SCALE IN FEETPERVIOUS AREASS. CHURCH AVENUE ALLEY EXISTING BASIN #1TOTAL BASIN AREA = 13,312 SFPERVIOUS AREA = 13,312 SFIMPERVIOUS AREA = 0 SFPROPERTY LINE APPENDIX B EXHIBIT B - POST-DEVELOPMENT STORMWATER EXHIBIT UPDNUPDNUPWSWSWSWSWSWSWSWSWSWSSSSSSSSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSD6W6W6WPTVFXXXXXX W W W W W W W W W W W W W W W W W W BFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBPBP BP BP BP BP NGNGNGNGNGNGNGNGNGNGNGNGNGSSSSSSSSSSSSSSSSWSWSWSWSWSBF BF BF BF BF BF BF BF BP BP BP BP BP BP BPBPBTV BTV BTV BTV BTV BTVBTVBTVBTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV BTV NGNGNGNGNGNGNGNGNGS S S S S S S S S S S S S S S S S S SSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSDSD TWXXXXXXXXOHPOHPOHPOHPOHPEX. 8" PVC SANITARY SEWER MAINEX. 15" PVC STORM DRAIN MAINEX. 8" DUCTILE IRON WATER MAIN CONNECT TO EXISTING15" STORM MAIN4816.50 4816.60 4816.70 4816.80 4816.90 4817.00 4817.10 4817.20 4817.30 4817.40 4817.50 4817.60 4 8 1 6 . 6 0 4 8 1 7 . 0 0 4815.40 4815.30 4817.904817.704817.504817.304817.10FIGURE NUMBER©PROJECT NO.DRAWN BY:DSGN. BY:APPR. BY:DATE:COPYRIGHT MORRISON-MAIERLE,2025Plotted by jacob zwemke on Nov/14/2025engineers surveyors planners scientistsMorrisonMaierle2880 Technology Blvd WestBozeman, MT 59718406.587.0721www.m-m.netP:\10758 - JBBArch\001 - 112 S.Church\ACAD\Civil\10758.001 - POST-DEVELOPMENT STORM.dwg 10758.002BTHE DEPOT ON CHURCH112 SOUTH CHURCH AVENUEBOZEMANMONTANAPOST-DEVELOPMENT STORMWATER EXHIBITJAZJAZCMS11/14/2510205100SCALE IN FEETPERVIOUS AREASS. CHURCH AVENUE ALLEY MAJOR BASIN #1TOTAL BASIN AREA = 13,312 SFPERVIOUS AREA = 1,036 SFIMPERVIOUS AREA = 12,276 SFPROPOSED STORMWATERDETENTION VAULTVOLUME PROVIDED = 2,600 CFVOLUME REQUIRED = 2,588 CFPROPERTY LINEPROPOSED OUTFALL TOEXISTING CITY OFBOZEMAN STORM DRAINPROPOSED TRENCHDRAIN ENTIRE LENGTHOF GARAGE FLOORPROPOSED TRENCHDRAIN CONNECTIONTO UNDERGROUNDDETENTION VAULTPROPOSEDAREA INLETPROPOSEDTRENCH DRAINPROPOSEDSTORM DRAINPIPING (TYP.) APPENDIX C HYDRAULIC CALCULATIONS Design Storm Frequency =2 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 0 0.000 0.95 1 0.95 0.95 0.00 13312 0.306 0.15 1 0.15 0.15 0.05 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 13312 0.3056 0.0458 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.05 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 2.08 0.10 10 1.53 0.07 15 1.24 0.06 20 0.99 0.05 25 0.84 0.04 30 0.75 0.03 35 0.66 0.03 40 0.59 0.03 45 0.54 0.02 50 0.49 0.02 55 0.45 0.02 60 0.42 0.02 120 0.24 0.01 180 0.19 0.01 360 0.12 0.01 720 0.08 0.00 1440 0.049 0.00 194.07 ft3 0.10 (ft3/s) 194.07 0.00 194.07 118.82 0.00 118.82 158.42 0.00 158.42 79.21 0.00 79.21 94.06 0.00 94.06 68.07 0.00 68.07 69.31 0.00 69.31 66.84 0.00 66.84 67.39 0.00 67.39 63.53 0.00 63.53 64.91 0.00 64.91 57.76 0.00 57.76 61.88 0.00 61.88 51.16 0.00 51.16 54.46 0.00 54.46 28.60 0.00 28.60 42.08 0.00 42.08 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) = = 0.1500 Cwd x Cf =0.15 Runoff Volume Discharge Volume Site Detention Impervious Pervious Totals Manhole Storage Storage Provided (CF) 0.00 Surface Type RATIONAL METHOD FOR RUNOFF CALCULATIONS PRE-IMPROVEMENT CONDITIONS (2-Year) Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 = Design Storm Frequency =10 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 0 0.000 0.95 1 0.95 0.95 0.00 13312 0.306 0.15 1 0.15 0.15 0.05 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 13312 0.3056 0.0458 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.05 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 3.87 0.18 10 2.83 0.13 15 2.29 0.10 20 1.84 0.08 25 1.56 0.07 30 1.38 0.06 35 1.22 0.06 40 1.09 0.05 45 1.00 0.05 50 0.91 0.04 55 0.84 0.04 60 0.79 0.04 120 0.41 0.02 180 0.29 0.01 360 0.17 0.01 720 0.10 0.00 1440 0.071 0.00 281.20 ft3 0.18 (ft3/s) 281.20 0.00 281.20 168.33 0.00 168.33 198.03 0.00 198.03 135.32 0.00 135.32 143.57 0.00 143.57 127.07 0.00 127.07 130.37 0.00 130.37 123.77 0.00 123.77 125.14 0.00 125.14 117.44 0.00 117.44 119.92 0.00 119.92 107.27 0.00 107.27 113.87 0.00 113.87 94.48 0.00 94.48 101.22 0.00 101.22 53.22 0.00 53.22 77.84 0.00 77.84 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) = = 0.1500 Cwd x Cf =0.15 Runoff Volume Discharge Volume Site Detention Impervious Pervious Totals Manhole Storage Storage Provided (CF) 0.00 Surface Type RATIONAL METHOD FOR RUNOFF CALCULATIONS PRE-IMPROVEMENT CONDITIONS (10-Year) Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 = Design Storm Frequency =100 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 0 0.000 0.95 1.25 1.19 1.00 0.00 13312 0.306 0.15 1.25 0.19 0.19 0.06 1.25 0.00 0.00 0 1.25 0.00 0.00 0 1.25 0.00 0.00 0 13312 0.3056 0.0573 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.06 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 6.09 0.35 10 4.45 0.25 15 3.61 0.21 20 2.89 0.17 25 2.46 0.14 30 2.18 0.12 35 1.92 0.11 40 1.72 0.10 45 1.57 0.09 50 1.44 0.08 55 1.33 0.08 60 1.24 0.07 120 0.61 0.03 180 0.41 0.02 360 0.22 0.01 720 0.14 0.01 1440 0.098 0.01 485.17 ft3 0.35 (ft3/s) Surface Type RATIONAL METHOD FOR RUNOFF CALCULATIONS PRE-IMPROVEMENT CONDITIONS (100-Year) Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 Manhole Storage Storage Provided (CF) 0.00 Runoff Volume Discharge Volume Site Detention Impervious Pervious Totals = = 0.1500 Cwd x Cf =0.19 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) 104.69 0.00 104.69 152.99 0.00 152.99 186.17 0.00 186.17 198.72 0.00 198.72 211.44 0.00 211.44 224.85 0.00 224.85 231.03 0.00 231.03 236.54 0.00 236.54 242.90 0.00 242.90 247.54 0.00 247.54 251.49 0.00 251.49 255.79 0.00 255.79 251.66 0.00 251.66 253.73 0.00 253.73 485.17 0.00 485.17 272.29 0.00 272.29 346.55 0.00 346.55 = Design Storm Frequency =2 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 12276 0.282 0.95 1 0.95 0.95 0.27 1036 0.024 0.15 1 0.15 0.15 0.00 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 13312 0.3056 0.2713 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.27 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 2.08 0.56 10 1.53 0.42 15 1.24 0.34 20 0.99 0.27 25 0.84 0.23 30 0.75 0.20 35 0.66 0.18 40 0.59 0.16 45 0.54 0.15 50 0.49 0.13 55 0.45 0.12 60 0.42 0.11 1148.55 120 0.24 0.07 180 0.19 0.05 360 0.12 0.03 720 0.08 0.02 1440 0.049 0.01 1,148.55 ft3 0.56 (ft3/s) 1148.55 0.00 1148.55 703.20 0.00 703.20 937.59 0.00 937.59 468.80 0.00 468.80 556.70 0.00 556.70 402.87 0.00 402.87 410.20 0.00 410.20 395.55 0.00 395.55 398.80 0.00 398.80 376.01 0.00 376.01 384.15 0.00 384.15 341.83 0.00 341.83 366.25 0.00 366.25 302.76 0.00 302.76 322.30 0.00 322.30 169.29 0.00 169.29 249.05 0.00 249.05 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) = = 0.8877 Cwd x Cf =0.89 Runoff Volume Discharge Volume Site Detention Impervious Pervious Totals Manhole Storage Storage Provided (CF) 0.00 Surface Type RATIONAL METHOD FOR RUNOFF CALCULATIONS POST-IMPROVEMENT CONDITIONS (2-Year) Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 = Design Storm Frequency =10 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 12276 0.282 0.95 1 0.95 0.95 0.27 1036 0.024 0.15 1 0.15 0.15 0.00 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 13312 0.3056 0.2713 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.27 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 3.87 1.05 10 2.83 0.77 15 2.29 0.62 20 1.84 0.50 25 1.56 0.42 30 1.38 0.37 35 1.22 0.33 40 1.09 0.30 45 1.00 0.27 50 0.91 0.25 55 0.84 0.23 60 0.79 0.21 1664.23 120 0.41 0.11 180 0.29 0.08 360 0.17 0.05 720 0.10 0.03 1440 0.071 0.02 1,664.23 ft3 1.05 (ft3/s) 1664.23 0.00 1664.23 996.19 0.00 996.19 1171.99 0.00 1171.99 800.86 0.00 800.86 849.70 0.00 849.70 752.03 0.00 752.03 771.56 0.00 771.56 732.50 0.00 732.50 740.63 0.00 740.63 695.06 0.00 695.06 709.71 0.00 709.71 634.83 0.00 634.83 673.90 0.00 673.90 559.14 0.00 559.14 599.02 0.00 599.02 314.97 0.00 314.97 460.66 0.00 460.66 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) = = 0.8877 Cwd x Cf =0.89 Runoff Volume Discharge Volume Site Detention Impervious Pervious Totals Manhole Storage Storage Provided (CF) 0.00 Surface Type RATIONAL METHOD FOR RUNOFF CALCULATIONS POST-IMPROVEMENT CONDITIONS (10-Year) Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 = Design Storm Frequency =100 years Length (ft) Width (ft) Depth (ft)Voids Storage Provided (CF)Infiltration Rate (in/hr) Discharge Rate, d =0.0000 cfs 0.00 0.00 0.00 0.00 0.00 0.00 Input values for runoff coefficients from appropriate tables. Length (ft) Diameter (ft) 0.00 0.00 Height (ft) Diameter (ft)Total Storage Provided 0.00 0.00 0.00 Area Area Runoff Coefficie nt Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 12276 0.282 0.95 1.25 1.19 1.00 0.28 1036 0.024 0.15 1.25 0.19 0.19 0.00 1.25 0.00 0.00 0 1.25 0.00 0.00 0 1.25 0.00 0.00 0 13312 0.3056 0.2863 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.31 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr) (ft 3/s) 5 6.09 1.86 10 4.45 1.36 15 3.61 1.10 20 2.89 0.88 25 2.46 0.75 30 2.18 0.67 35 1.92 0.59 40 1.72 0.53 45 1.57 0.48 50 1.44 0.44 55 1.33 0.41 60 1.24 0.38 2587.59 120 0.61 0.19 180 0.41 0.13 360 0.22 0.07 720 0.14 0.04 1440 0.098 0.03 2,587.59 ft3 1.86 (ft3/s) Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS POST-IMPROVEMENT CONDITIONS (100-Year) Surface Type Gravel Voids Storage Pipe Storage Storage Provided (CF) 0.00 Manhole Storage Storage Provided (CF) 0.00 Pervious Totals = 0.8877 Cwd x Cf =1.00 Runoff Volume Discharge Volume Site Detention = 558.33 0.00 558.33 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) 815.96 0.00 815.96 992.90 0.00 992.90 1059.83 0.00 1059.83 1127.67 0.00 1127.67 1199.18 0.00 1199.18 1232.19 0.00 1232.19 1261.52 0.00 1261.52 1295.44 0.00 1295.44 1320.20 0.00 1320.20 1341.28 0.00 1341.28 1342.20 0.00 1342.20 1364.20 0.00 1364.20 1353.20 0.00 1353.20 1452.22 0.00 1452.22 1848.28 0.00 1848.28 2587.59 0.00 2587.59 = Design Standards and Specifications Policy City of Bozeman, October 2024 as Amended RAINFALL INTENSITY-DURATION CURVES (Figures I-2, I-3) Time 2 5 10 25 50 100 (min)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr)(in/hr) 5 2.08 3.16 3.87 4.76 5.43 6.09 10 1.53 2.31 2.83 3.48 3.97 4.45 15 1.24 1.87 2.29 2.83 3.22 3.61 20 0.99 1.50 1.84 2.26 2.58 2.89 25 0.84 1.28 1.56 1.93 2.20 2.46 30 0.75 1.13 1.38 1.70 1.94 2.18 35 0.66 0.99 1.22 1.50 1.71 1.92 40 0.59 0.89 1.09 1.35 1.53 1.72 45 0.54 0.81 1.00 1.23 1.40 1.57 50 0.49 0.74 0.91 1.12 1.28 1.44 55 0.45 0.69 0.84 1.04 1.18 1.33 60 0.42 0.64 0.79 0.97 1.10 1.24 120 0.24 0.34 0.41 0.49 0.55 0.61 180 0.19 0.25 0.29 0.34 0.37 0.41 360 0.12 0.15 0.17 0.19 0.21 0.22 720 0.08 0.09 0.10 0.12 0.13 0.14 1440 0.049 0.062 0.071 0.082 0.090 0.098 Storm Recurrence Interval STORMWATER MANAGEMENT MANUAL FREQUENCY FACTORS FOR THE RATIONAL FORMULA Recurrence Interval Adjustment Factor (Years)Cf 2 1.00 5 1.00 10 1.00 25 1.10 50 1.20 100 1.25 * C X Cf should not exceed 1.0 APPENDIX D STORM WATER OPERATIONS AND MAINTENANCE MANUAL Storm Water Management System Operation & Maintenance Manual The Depot on Church 112 South Church Avenue Bozeman, Montana Prepared For: JBB Architecture Prepared By: 2880 Technology Blvd. W. • PO Box 1113 • Bozeman, MT 59771 (406) 587-0721 • www.m-m.net The Depot on Church Storm Water Operation & Maintenance Manual 1 Site Data Location: Depot on Church 112 South Church Avenue Bozeman, MT Responsible Party for Maintenance: The owner of the property shall be required to keep a log of all required inspections and maintenance required. The log shall be made available to the City of Bozeman Public Works Department for review as requested. Land Use & Site Area: The project site is located at 112 South Church Avenue and zoned B-3. The site consists of one building with associated hardscaping. The site will be landscaped according to approved landscaping plans and must meet the City of Bozeman Unified Development Code. Storm Water Management Systems: The storm water management system includes an underground detention vault below the building. Storm runoff will be captured via roof drains and routed to the vault. The vault will include a pump system that releases stormwater into the existing storm main in South Church Avenue at controlled rates. The surface level parking garage includes a trench drain and inlet system to capture any additional runoff in the garage. This runoff is also routed to the vault. Inspection & Maintenance Storm water facilities and permanent Best Management Practices (BMPs) must be inspected in accordance with this document. All documentation on scheduled inspections, times of inspections, maintenance completed, remedial actions taken to make repairs, and any modifications or reconstruction of the storm system shall be maintained on-site. Disposal of the accumulated sediment must be in accordance with all applicable local, state, and federal guidelines and regulations. If any drainage structure or outfall indicates the presence of petroleum, the petroleum material shall be removed and disposed of immediately in accordance with applicable regulations. All estimated costs are based on labor rates assumed in 2025. The Depot on Church Storm Water Operation & Maintenance Manual 2 Pavement Sweeping & Vacuuming: All hardscaped areas shall be swept twice a year, scheduled in spring and fall. Estimated Annual Cost: $500 Strom Drain Inlet/ Sump The inlet shall be inspected to ensure it has adequate sump capacity, the grate is in place, secure and free of debris, the frame and grate are not damaged, and internal concrete and grout is intact.  Inspect the inlet four times per year and following large storm events.  Clean sump annually or whenever sump becomes filled with sediment to half its depth (1’-0”).  Estimated Cost: $500 If inspection indicates the presence of petroleum, the petroleum material shall be removed and disposed of immediately in accordance with applicable regulations. Storm Drain Inlet Expected Design Life: If regular maintenance is performed, the storm drain inlet can be expected to last for 50 to 100 years. Expected Replacement Cost: $5,000 Underground Retention System (Vault): All storm drain pipe shall be inspected for any damage and/or blockages.  Inspect piping annually and following large storm events.  If excessive sediment is determined to exist in the pipe, it shall be removed through jetting and flushing.  Estimated cost: $1,000  After major storm events, monitor the system to ensure the pumping system is working properly. If the systems appear to be clogged or malfunctioning, consult with an engineer or other qualified professional to evaluate the system and determine whether it needs to be replaced. Regular maintenance and sedimentation prevention greatly increases the life of the system. Underground Retention Expected Design Life: 50+ years if regular maintenance is performed. Expected Replacement Cost: $20,000 to $30,000 The Depot on Church Storm Water Operation & Maintenance Manual 3 Housekeeping Operations Good housekeeping and material management reduces the risk of spills or other accidental exposure of materials and substances to storm water runoff. Pay special attention to runoff directed towards Bozeman Creek.  All materials stored on-site must be stored in a neat, orderly manner in their appropriate containers and, if possible, under a roof or other enclosure.  Products shall be kept in their original containers with the original manufacturer’s label.  Substances should not be mixed with one another unless recommended by the manufacturer.  Whenever possible, all of a product will be used up before disposing of a container.  Original materials labels and material safety data sheets (MSDS) shall be kept by the Owner.  Petroleum products:  All on-site vehicles and parking areas shall be monitored weekly for leaks and spills. Spills shall be cleaned immediately.  Petroleum products shall be stored under cover and shall be in tightly sealed containers that are clearly labeled.  Fertilizers:  Fertilizers shall only be used in the minimum amounts as recommended by the manufacturer. Avoid applying fertilizer within 15 feet of Bozeman Creek.  The contents of any unused fertilizer shall be transferred to a clearly labeled, sealable plastic bin to avoid spillage.  Paints solvents.  All paints and solvents shall be stored in original manufacturer’s containers in a covered location.  The use of paints and solvents shall, whenever possible, be limited to service or storage bays. Where not possible, the work area shall be protected with impermeable drop clothes or tarps. At no point shall material be used in parking or access ways that are tributaries to the drainage system. Spill Control Practices  Manufacturer's recommended methods shall be clearly posted for spill clean-up and hotel personnel shall be made aware of the procedures and the locations of cleanup information and supplies.  Material and equipment necessary for spill clean-up will be kept on-site in a designated material storage area. Equipment will include, but not be limited to, brooms, dust pans, mops, rags, gloves, goggles, absorbent materials, sand, sawdust, and plastic & metal trash containers specifically kept and labeled for this purpose.  All spills must be cleaned-up immediately after discovery.  Spills of toxic or hazardous material must be reported to the appropriate state, local, or federal agency, as required by-law. The Depot on Church Storm Water Operation & Maintenance Manual 4 Winter Maintenance Activities  Snow plowing operations shall stockpile snow, ice and accumulated materials in areas where snow melt will flow into the on-site drainage systems, including drainage basins.  During winter conditions sand use site-wide shall be applied to the minimum extent possible to maintain safe conditions.  The usage of sodium chloride or chloride containing materials for snow and ice removal is not recommended so as to avoid the introduction of salts to the storm water management system. Repair Procedures  Grass Swales, Dense Weeds or Sparse Grass Cover  Re-seed or sod the area, but first determine and address the source of the problem. Expand irrigation coverage, add soil amendments, fertilize, etc., as needed to improve growth media and grass health.  Grass Swales, Areas of Ponding  Cut sod and re-grade the area for consistent downgradient slope along the swale. Then re-seed or sod the area of disturbance. Emergency Contacts PLEASE CALL 9-1-1 FOR ALL POTENTIAL EMERGENCIES City of Bozeman Fire Department: (406) 582-2350 City of Bozeman Police Department: (406) 582-2000 Chapter 6 - Storm Drainage Design 6-44 City of Bozeman Design and Construction Standards Stormwater Facility Inspection Form Section 1: General Information Facility ID: Facility Type: Choose an item. Date/Time: Click or tap to enter a date. Owner: Contact: Inspector’s Name, contact info: Choose an item. Location/Access info: Type of Inspection: ☐ Routine, Dry Weather ☐ Routine, Wet Weather ☐ Complaint Driven ☐ Other: __________________ Section 2: Weather and Discharge Information Most recent precipitation or melt: Temperature: Is a stormwater discharge occurring? ☐ Yes ☐ No If yes, what is the source and quality of discharge? Is an illegal discharge occurring? ☐ Yes ☐ No If yes, what is the source and quality of discharge? Section 3: Facility Maintenance Priority ☐ Low: Stormwater facility appears to be functioning as designed. Continue scheduled maintenance. ☐ Medium: Stormwater facility requires minor to moderate sediment and vegetation maintenance to mitigate the risk of flooding, waterway pollution, and infrastructure failure. ☐ High: Stormwater facility requires significant sediment dredging, vegetation removal, and/or infrastructure repairs to restore function. Notes, Findings & Recommendations: Inspector’s Signature: ________________________________ Date: ___________________ Chapter 6 - Storm Drainage Design 6-45 City of Bozeman Design and Construction Standards Section 4: Qualitative Analysis Components # Items Conditions Results Notes and Required Actions General Degraded, missing, or inadequate Yes 1.1 Accessibility maintenance access? No ☐☐ Trash, sediment, and waste within 1.2 Debris ☐Yes and around the facility? ☐ No Overgrown or dead cattails, Yes 1.3 Vegetation woody shrubs, weeds, grass, and ☐ trees? ☐ No Infrastructure Damaged inlet pipe, outlet pipe, Yes1.4 ☐ Condition outfall structure, or fencing? ☐ No Facility Condition Pretreatment Bay Clogged, obstructed, or filled 2.1 ☐ Yes or Facility pretreatment forebay or facility? ☐ No 2.2 Storage Bay Clogged or filled storage bay? ☐ Yes ☐ No Stagnant water with infiltration Groundwater or Yes 2.3 greater than 48 hours post-rain ☐ Standing Water event? ☐ No 2.4 Flow Path Clogged or obstructed flow path? ☐ Yes ☐ No Barren or exposed surfaces on Yes 2.5 Side Slopes ☐ Facility’s side slopes and bottom? ☐ No Maintenance Maintenance Plan Is there a written plan specific to ☐ Yes 3.1 or Agreement this facility? ☐ No Yes 3.2 Implementation Is there evidence of maintenance? ☐ ☐ No Chapter 6 - Storm Drainage Design 6-46 City of Bozeman Design and Construction Standards Section 5: Quantitative Analysis Vegetation Cover type % Within facility Notes Bare ground Aquatics Grasses/Herbaceou Trees >3” DBH Shrubs Total 100 Elevation Analysis Location Reading (ft) Elevation (ft) Notes SRV#CP Control Point SRV#1 Inlet SRV#2 Outlet SRV#3 Center SRV#4 North of Center SRV#5 East of Center SRV#6 South of Center SRV#7 West of center SRV#8 Berm or overflow SRV#9 Summary Chapter 6 - Storm Drainage Design 6-47 City of Bozeman Design and Construction Standards Section 6: Facility Maintenance Inspection Exhibit Chapter 6 - Storm Drainage Design 6-48 City of Bozeman Design and Construction Standards Photo 1 description Photo 2 description Section 7: Photo Log APPENDIX E GEOTECHNICAL INVESTIGATION