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HomeMy WebLinkAbout023 Water, Sewer, & Stormwater Design Report JOB NO. B23-026 MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA REV. NOVEM BER 2023 406.586.0277 tdhengineering.com 234 East Babcock Street Suite 3 Bozeman, MT 59715 CLIENT ENGINEER SMA Architecture & Design 428 E Mendenhall Street Bozeman, MT 59715 TD&H Engineering 234 East Babcock Street, Suite 3 Bozeman, MT 59715 Engineer: Cody Croskey, PE 811 WEST MENDENHALL APARTMENTS BOZEMAN, MONTANA BASIS OF DESIGN REPORT Image courtesy of SMA Architecture 11/15/2023 B23-026 811 West Mendenhall Apartments Page 1 of 4 811 WEST MENDENHALL APARTMENTS ENGINEERING DESIGN REPORT REV. NOVEMBER 2023 Purpose and Introduction The purpose of this report is to explain how water, sanitary sewer, and storm drainage improvements will be designed to meet the City of Bozeman requirements and Montana Public Works Standard Specifications (MPWSS) to provide service to a new residential building in downtown Bozeman, Montana. The project is located at the NW corner of N. 8th Avenue and W. Mendenhall Street. The parcel is comprised of lots 4-12 in Block 7 of the Springbrook Addition to the City of Bozeman totaling 0.72 acres in size. The property is split between the (B-2M) Community Business District-Mixed and recently re-zoned (R-5) Residential Mixed-Use High Density District and is currently partially developed with an existing sign manufacturing shop and single-family residence. Proposed redevelopment includes the demolition of the existing buildings and new site improvements and construction of a new multi-story residential building with internal parking garage and a small cowork office space. The lot will be nearly 100% covered by the new building with rooftop landscaping features. The need for water and sewer main upgrades has been identified through initial pre- application and site plan reviews. New upsized 8-inch minimum diameter water & sewer mains will be installed in N. 8th Avenue to serve this property and are expected to follow the off-site concurrent construction process. Design Report Water The property has multiple existing live water services connected to the existing business and residence. These services are proposed to be abandoned at their connection points with the water mains in conjunction with demolition activities at the site. The estimated existing domestic water demands being removed with the existing buildings are summarized in Table 1 below with supporting assumptions and calculations provided in Appendix A in accordance with C.O.B. DSSP Section V.A.4 and the 2017 Water Facility Plan. Table 1: Estimated Existing Water Demands (Being Removed) Average Day Max. Day Peak Hour Existing Businesses Demands -(395) gpd -(0.6) gpm -(0.8) gpm The new residential mixed-use building will replace the existing uses with 93 new dwelling units and 1,711 S.F of cowork office space. The new estimated domestic water demands for the project are summarized in Table 2 below with supporting assumptions and calculations provided in Appendix A in accordance with C.O.B. DSSP B23-026 811 West Mendenhall Apartments Page 2 of 4 Section V.A.4 and the 2017 Water Facility Plan. Table 2: Estimated New Water Demands Average Day Max. Day Peak Hour New Building Demand 34,358 gpd 54.9 gpm 71.6 gpm Irrigation at the site will be limited to roof-top planter & garden features and landscaped lot frontage areas that will also be supplied from the building’s public water supply. The new building will be equipped with fire sprinklers and the fire flow requirement for the new building is 1,500 gpm based on building size and construction type as determined following International Fire Code Appendix B criteria. A new 4-inch domestic water service and 6-inch fire service line will be extended to the new building from the water main in N. 8th Avenue. Final service sizing will be verified by the mechanical engineer in accordance with the Uniform Plumbing Code, actual fixture unit counts, and fire protection system requirements. The services will be Class 51 ductile iron and be installed per the City of Bozeman Design Standards and Modifications to Montana Public Works Standard Specifications (MPWSS). A 6” water main is currently looped around the development within N. 8th Avenue and W. Mendenhall Street. The 6” water main in N. 8th Avenue, however, will be replaced and upsized to meet the City’s minimum standard of 8” due to concerns with the age and durability of the existing pipe material to make the new large service connections required for this project. Fire hydrant flow reports were provided by the City Engineering Department for the nearest existing fire hydrants to confirm the existing water main has adequate capacity to convey the maximum day plus fire flow demand for the proposed development in accordance with C.O.B. DSSP Section V.A.4. The existing water distribution system for this area was modeled using Bentley’s WaterCAD software. The water modeling indicates that the maximum day domestic demand of 54.9 gpm plus 1,500 gpm fire flow is more than available in the 6” water main adjacent to the project without dropping below a 20 psi residual pressure or exceeding 15 ft per second velocities in the water mains. The water main capacity in N. 8th Avenue is only expected to increase when upsized to 8” with this project, and updated pipe capacity calculations will be provided with the public infrastructure plan submittal. The results from the current system water modeling analysis are provided in Appendix A. A new fire hydrant will be installed at the intersection of N. 8th Avenue and W. Mendenhall Street to provide additional fire protection coverage and adjacency to the new building’s Fire Department Connection (FDC). Sewer The property has multiple existing live sewer services connected to the existing business and residence. These services are proposed to be abandoned in conjunction with demolition activities at the site. The estimated sewer demands being removed with the existing building are summarized in Table 3 below with supporting assumptions and calculations provided in Appendix B in accordance with C.O.B. DSSP Section V.B and B23-026 811 West Mendenhall Apartments Page 3 of 4 the 2015 Wastewater Facilities Plan. Table 3: Estimated Existing Sewer Demands (Being Removed) Average Day (gpd) Peak Hour (gpm) Existing Building Demand -(192) - Lot Infiltration -(108) - Total Sewer Demand -(300) -(1.00) The new residential mixed-use building will replace the existing uses with 93 new dwelling units and 1,711 S.F of cowork office space. The new estimated domestic sewer demands for the project are summarized in Table 4 below with supporting assumptions and calculations provided in Appendix B in accordance with C.O.B. DSSP Section V.B and the 2015 Wastewater Facilities Plan. Table 4: Estimated New Sewer Demands Average Day (gpd) Peak Hour (gpm) New Building Demand 13,075 - Lot Infiltration 108 - Total Sewer Demand 13,183 37.73 A new 8-inch sewer service is proposed to extend from the new building to the new upsized sewer main in N. 8th Avenue. Final service sizing for this project will be verified by the mechanical engineer in accordance with the Uniform Plumbing Code and actual fixture unit counts. The new sewer service line will be SDR-26 PVC and will be installed per the City of Bozeman Design Standards and Modifications to Montana Public Works Standard Specifications (MPWSS). It is expected to require a manhole connection to the new sewer main in N. 8th Avenue due to its size. Storm Drainage Existing Conditions: The existing project site consists of a single-family residence and small sign manufacturing facility with multiple buildings, outbuildings, concrete paved areas, gravel parking areas, and lawn spaces. The entire site slopes to the northwest with most of the runoff being directed to the alley on the west side of the property. No existing stormwater management controls are evident at the site. The site runoff ultimately enters the City’s storm sewer system via curb inlet at the intersection of N. 9th Avenue and W. Lamme Street. Stormwater Quantity: The proposed site development includes a new multi-story building with a footprint and roof that will cover nearly 100% of the property. A new parking garage will be constructed internally to the building and accessed from the alley and limited landscaping consisting of planting beds and turf will be established around edges of the site. All of the stormwater from the building roof areas, parking garage entry, and east lawn spaces will be collected and conveyed via piping to an underground chamber designed B23-026 811 West Mendenhall Apartments Page 4 of 4 to retain & infiltrate the 10-yr, 2-hr design storm. Therefore, the only drainage areas contributing post-development runoff flows during the design storm event will be the landscaping beds on the west and north sides of the building. With most of the site being retained, the post-development runoff flow rates will be far less than existing conditions during the design storm event as shown in the stormwater runoff calculations provided in Appendix C. Stormwater Quality: As mentioned previously, stormwater runoff from the building roof areas, parking garage entry, and east lawn spaces will be collected and routed to a sub- surface chamber facility designed to capture and fully retain/infiltrate the flow from the 10-yr, 2-hr storm event. The design retention volume has also been confirmed to have enough storage capacity to capture the first half inch of rainfall from the building and associated impervious areas on the property as shown in the stormwater runoff calculations provided in Appendix C. Conveyance: The overflow route from the sub-surface stormwater chamber facility will consist of a new sidewalk drainage chase designed to discharge to N. 8th Avenue during larger storm events. From this location it will flow via curb & gutter to the same street inlet where it currently enters the City’s storm sewer system. A hydraulic channel calculation demonstrating the drainage chase’s capacity to convey the 25-yr storm event is provided in Appendix C. Infiltration: Geotechnical drilling investigations were conducted at the site on October 20, 2020 and July 24, 2023. Groundwater was observed in all 5 bore holes ranging in depths of 7.5 to 15-feet below the ground surface. A groundwater monitoring pipe was also installed near the center of the site and was monitored through June and July of 2023 with groundwater being observed at 9 to 9.2-feet below the ground surface. The bottom of the proposed chambers will be approximately 5.5-feet below existing ground and will be over-excavated to tie into native gravels which were encountered at depths ranging from 6.5 to 9.5-feet below the ground surface. Therefore, it is anticipated that the underlying soils will be conducive to infiltration and groundwater will be sufficiently deep to allow for a subsurface retention/infiltration strategy to be successful at this site. The geotechnical investigation logs and on-site groundwater monitoring results are provided in Appendix C. APPENDIX A Water Calculations 811 West Mendeanhall Apartments 811 W. Mendenhall Street Date: 07.26.23 Existing Water Demand Calculation Domestic Water Demand - Existing Buildings: Residential Use: Residential Units =1 units People =2.17 people (2.17 people/unit) Residential Flow =369 GPD (170 gpcd)(Per COB Design Standards) Commercial Use: Light Manufacturing =2,832 sf 0.065 acres Commercial Flow =26 GPD 400 gal/acre/day per Table 3.5, 2017 Water Facility Plan Peak Hour Demand: Average Day Demand =395 GPD (All Uses) Average Day Demand =0.3 gpm (GPD / 1,440 minutes) Maximum Day Demand =0.6 gpm (Ave. Day x Peaking Factor = 2.3) Peak Hour Demand =0.8 gpm (Ave. Day x Peaking Factor = 3) (Per COB 2015 Wastewater Facilities Plan) 811 West Mendeanhall Apartments 811 W. Mendenhall Street Date: 07.26.23 New Water Demand Calculation Domestic Water Demand - New Building: Residential Use: Residential Units =93 units People =201.8 people (2.17 people/unit) Residential Flow =34,308 GPD (170 gpcd)(Per COB Design Standards) Commercial Use: Cowork Office =1,711 sf 0.039 acres Commercial Flow =50 GPD 1,285 gal/acre/day per Table 3.9, 2017 Water Facility Plan Peak Hour Demand: Average Day Demand =34,358 GPD (All Uses) Average Day Demand =23.9 gpm (GPD / 1,440 minutes) Maximum Day Demand =54.9 gpm (Ave. Day x Peaking Factor = 2.3) Peak Hour Demand =71.6 gpm (Ave. Day x Peaking Factor = 3) Fire Flow Requirement - New Building: IBC Construction Type =IIIA Fire Flow Calculation Area =103,772 sf Automatic Fire Sprinkler System =Yes Fire Sprinkler System Type =NFPA 13R Required Fire Flow =1,500 gpm (per IFC Appendix B) (Per COB 2015 Wastewater Facilities Plan) Scenario: Base ©2017 HERE © 2017 Microsoft Corporation Page 1 of 176 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203-755-16667/10/2023 WaterCAD [10.04.00.108]Bentley Systems, Inc. Haestad Methods Solution CenterB23-026 FIRE FLOW.wtg Fire Flow Node FlexTable: Fire Flow Results Table Pipe w/ Maximum Velocity Velocity of Maximum Pipe (ft/s) Junction w/ Minimum Pressure (System) Pressure (Calculated System Lower Limit) (psi) Pressure (System Lower Limit) (psi) Junction w/ Minimum Pressure (Zone) Pressure (Calculated Residual) (psi) Pressure (Residual Lower Limit) (psi) Flow (Total Available) (gpm) Fire Flow (Available) (gpm) Label P-915.00J-122220J-1221203,5263,526J-2 P-1115.00J-144820J-1450202,6342,634J-4 P-1115.00J-143620J-1433202,4672,466811 W MENDENHALL P-1615.00J-143220J-1432202,3832,383J-6 P-315.00J-124020J-1240203,0593,059J-8 P-415.00J-154720J-1546202,3502,350J-9 P-1315.00J-145020J-1451202,3502,350J-10 P-1215.00J-145020J-1452202,3502,350J-11 P-615.00J-174120J-1740202,3502,350J-12 P-515.00J-124120J-1240202,3502,350J-13 P-715.00J-154720J-1546201,3221,322J-14 P-815.00J-144720J-1446201,3221,322J-15 P-915.00J-122220J-1222203,4813,481J-17 P-1115.00J-144920J-1452202,5112,511J-20 Page 1 of 176 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203-755-16667/10/2023 WaterCAD [10.04.00.108]Bentley Systems, Inc. Haestad Methods Solution CenterB23-026 FIRE FLOW.wtg CITY OF BOZEMAN Fire Flow Request Form PHONE (406) 582-3200 FAX (406) 582-3201 Date June 26, 2023 Location 811 West Mendenhall Street Pressure Zone South (HGL 5125) GIS Hydrant ID# 113, 114, 2431 and 2748 Adjacent Main Size 8-inch DI, 6-inch Cast Iron, 8-inch DI, 8-inch DI Model Scenario Maximum Day Demand, Steady State, Fire Flow Reference 2017 Water Facility Plan Update1 Hydrant Curves An Excel Spreadsheet with hydrant curves has been provided for the requested location Requested Location via the Bozeman Infrastructure Viewer2 If you have questions or need further information feel free to email. Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information is provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether such damages arise under contract, tort, strict liability or inequity. HOME OF MONTANA STATE UNIVERSITY GATEWAY TO YELLOWSTONE PARK 1 https://www.bozeman.net/home/showpublisheddocument/4977/636420174896170000 2 https://gisweb.bozeman.net/Html5Viewer/?viewer=infrastructure GIS Hydrant # Available Flow (gpm)Residual Pressure (psi)113 0 128.54 200 128.13 400 127.67 600 127.12 800 126.47 1,000.00 125.72 1,200.00 124.89 1,400.00 123.97 1,600.00 122.96 1,800.00 121.87 2,000.00 120.69 2,200.00 119.43 2,400.00 118.09 2,600.00 116.66 2,800.00 115.16 3,000.00 113.57 3,200.00 111.91 3,400.00 110.17 3,600.00 108.35 3,800.00 106.46 4,000.00 104.49 4,200.00 102.44 4,400.00 100.32 4,600.00 98.13 4,800.00 95.86 5,000.00 93.51 5,200.00 91.09 5,400.00 88.6 5,600.00 86.04 5,800.00 83.41 6,000.00 80.7 6,200.00 77.93 6,400.00 75.08 6,600.00 72.16 6,800.00 69.18 7,000.00 66.09 7,200.00 62.93 7,400.00 59.71 7,600.00 56.42 7,800.00 53.06 8,000.00 49.62 8,200.00 46.12 8,400.00 42.55 8,600.00 38.91 8,800.00 35.2 9,000.00 31.42 9,200.00 27.58 9,400.00 23.66 9,600.00 19.68 9,800.00 15.64 10,000.00 11.52 10,200.00 7.34 10,400.00 3.09 10,543.49 0.01 Hydrant Curve 0 20 40 60 80 100 120 140 0 2000 4000 6000 8000 10000 12000Residual Pressure (psi)Available Flow (gpm) Hydrant Curve 113 Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information is provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether such damages arise under contract, tort, strict liability or inequity. GIS Hydrant # Available Flow (gpm)Residual Pressure (psi)114 0 125.54 200 125.02 400 124.26 600 123.23 800 121.94 1,000.00 120.4 1,200.00 118.61 1,400.00 116.59 1,600.00 114.34 1,800.00 111.87 2,000.00 109.17 2,200.00 106.26 2,400.00 103.13 2,600.00 99.79 2,800.00 96.24 3,000.00 92.49 3,200.00 88.52 3,400.00 84.35 3,600.00 79.98 3,800.00 75.41 4,000.00 70.64 4,200.00 65.67 4,400.00 60.51 4,600.00 55.14 4,800.00 49.59 5,000.00 43.84 5,200.00 37.9 5,400.00 31.76 5,600.00 25.44 5,800.00 18.93 6,000.00 12.24 6,200.00 5.35 6,351.98 0 Hydrant Curve 0 20 40 60 80 100 120 140 0 1000 2000 3000 4000 5000 6000 7000Residual Pressure (psi)Available Flow (gpm) Hydrant Curve 114 Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual GIS Hydrant # Available Flow (gpm)Residual Pressure (psi)2431 0 128.21 200 127.83 400 127.4 600 126.91 800 126.36 1,000.00 125.76 1,200.00 125.09 1,400.00 124.34 1,600.00 123.53 1,800.00 122.65 2,000.00 121.71 2,200.00 120.71 2,400.00 119.64 2,600.00 118.51 2,800.00 117.32 3,000.00 116.07 3,200.00 114.76 3,400.00 113.4 3,600.00 111.97 3,800.00 110.49 4,000.00 108.95 4,200.00 107.35 4,400.00 105.7 4,600.00 103.99 4,800.00 102.23 5,000.00 100.41 5,200.00 98.53 5,400.00 96.6 5,600.00 94.62 5,800.00 92.58 6,000.00 90.48 6,200.00 88.34 6,400.00 86.14 6,600.00 83.89 6,800.00 81.56 7,000.00 79.17 7,200.00 76.73 7,400.00 74.24 7,600.00 71.7 7,800.00 69.1 8,000.00 66.45 8,200.00 63.74 8,400.00 60.98 8,600.00 58.18 8,800.00 55.32 9,000.00 52.41 9,200.00 49.44 9,400.00 46.43 9,600.00 43.36 9,800.00 40.25 10,000.00 37.08 10,200.00 33.86 10,400.00 30.6 10,600.00 27.27 10,800.00 23.9 11,000.00 20.48 11,200.00 17.01 11,400.00 13.49 11,600.00 9.92 11,800.00 6.3 12,000.00 2.63 Hydrant Curve 0 20 40 60 80 100 120 140 0 2000 4000 6000 8000 10000 12000 14000Residual Pressure (psi)Available Flow (gpm) Hydrant Curve 2431 Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information is provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether such damages arise under contract, tort, strict liability or inequity. GIS Hydrant # Available Flow (gpm)Residual Pressure (psi)2748 0 122.84 200 122.36 400 121.83 600 121.14 800 120.3 1,000.00 119.32 1,200.00 118.2 1,400.00 116.96 1,600.00 115.58 1,800.00 114.07 2,000.00 112.43 2,200.00 110.67 2,400.00 108.78 2,600.00 106.77 2,800.00 104.63 3,000.00 102.37 3,200.00 100 3,400.00 97.5 3,600.00 94.89 3,800.00 92.16 4,000.00 89.31 4,200.00 86.36 4,400.00 83.28 4,600.00 80.1 4,800.00 76.8 5,000.00 73.39 5,200.00 69.86 5,400.00 66.23 5,600.00 62.49 5,800.00 58.65 6,000.00 54.69 6,200.00 50.63 6,400.00 46.45 6,600.00 42.14 6,800.00 37.73 7,000.00 33.2 7,200.00 28.58 7,400.00 23.85 7,600.00 19.01 7,800.00 14.06 8,000.00 9.01 8,200.00 3.86 8,345.91 0.03 Hydrant Curve 0 20 40 60 80 100 120 140 0 1000 2000 3000 4000 5000 6000 7000 8000 9000Residual Pressure (psi)Available Flow (gpm) Hydrant Curve 2748 Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information is provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether such damages arise under contract, tort, strict liability or inequity. APPENDIX B Sewer Calculations 811 West Mendeanhall Apartments 811 W. Mendenhall Street Date: 07.26.23 Existing Sewer Demand Calculation Average Day Sewer Demand - Existing Buildings: Residential Use: Residential Units =1 units Population =2.17 people (2.17 people/unit) Residential Flow =140 GPD (64.4 gpcd) Commercial Use: Light Manufacturing =2,832 sf 0.065 acres Commercial Flow =52 GPD 800 gal/acre/day per Table 2-12 2015 Wastewater Facilities Plan Infiltration: Property Size =0.72 acres Infiltration Flow =108 GPD (150 gpd/acre per COB Design Standards) Total Existing Average Day Demand: 300 GPD (residential + commercial + infiltration) Total Existing Peak Sewer Flow: Average Day Demand =300 GPD (residential + commercial) P =0.0047 (population/1,000) Peaking Factor =4.44 Peak Sewer Demand =1,331 GPD (avg. day demand)*(peaking factor) + Infiltration Flow =108 GPD (not peaked) Total Peak Flow =1,439 GPD (residential + commercial + infiltration) Peak Sewer Flow =1.00 GPM (peak flow)/(24 hrs/day)/(60 min/hr) Values per C.O.B. 2015 Wastewater Facilities Plan 𝑄𝑚𝑎𝑥 𝑄𝑎𝑣𝑔 =18 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠 𝑛𝑑 𝑛𝑑𝑛𝑛𝑙𝑑1/2 4 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠 𝑛𝑑 𝑛𝑑𝑛𝑛𝑙𝑑1/2 811 West Mendeanhall Apartments 811 W. Mendenhall Street Date: 07.26.23 New Sewer Demand Calculation Average Day Sewer Demand : Residential Use: Residential Units =93 units Population =201.8 people (2.17 people/unit) Residential Flow =12,997 GPD (64.4 gpcd) Commercial Use: Cowork Office =1,711 sf 0.039 acres Commercial Flow =79 GPD 2,000 gal/acre/day per Table 2-13, Zone B2-M, 2015 Wastewater Facilities Plan Infiltration: Property Size =0.72 acres Infiltration Flow =108 GPD (150 gpd/acre per COB Design Standards) Total Development Average Day Demand: 13,183 GPD (residential + commercial + infiltration) Total Development Peak Sewer Flow: Average Day Demand =13,075 GPD (residential + commercial) P =0.2018 (population/1,000) Peaking Factor =4.15 Peak Sewer Demand =54,217 GPD (avg. day demand)*(peaking factor) + Infiltration Flow =108 GPD (not peaked) Total Peak Flow =54,325 GPD (residential + commercial + infiltration) Peak Sewer Flow =37.73 GPM (peak flow)/(24 hrs/day)/(60 min/hr) Values per C.O.B. 2015 Wastewater Facilities Plan 𝑄𝑚𝑎𝑥 𝑄𝑎𝑣𝑔 =18 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠 𝑛𝑑 𝑛𝑑𝑛𝑛𝑙𝑑1/2 4 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠 𝑛𝑑 𝑛𝑑𝑛𝑛𝑙𝑑1/2 811 West Mendeanhall Apartments 811 W. Mendenhall Street Date: 07.26.23 8" Sewer Service Pipe Capacity Input Values d =0.67 ft =8" y =0.500 ft =75% Calculated Values (Equations from Fluid Mechanics by Chow) Theta (Θ)4.19 rad 2*arccos(1-y/(d/2)) Area (A)0.28 ft2 (1/8)*(Θ-sinΘ)d2 Wetted Perimeter (P)1.40 ft 0.5Θd Hydraulic Radius (R )0.20 ft (.25)*(1-(sinΘ)/Θ)d Top Width (T)0.58 ft (sin 0.5Θ)d Mannings Equation (Equation from Fundamentals of Mechanics by Munson) n =0.013 (per COB Design Standards) S0 =0.0104 ft/ft (min. 1/8" per foot for 6" services) Q =1.13 cfs Q = 1.49/n*A*R2/3*S00.5 Q =506.10 gpm Q gpm = (Q cfs)(7.48 gal/ft3)(60 sec/min) V =4.02 ft/s V = Q/A Results An 8" diameter sewer service at the min. 1/8" per foot slope flowing 75% full has the capacity for 506.10 gpm. Appendix C Storm Water Calculations ALLEY W MENDENHALL STREETN 8TH AVENUE REVISIONDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:B23-026 SW BASINSREV DATE 811 WEST MENDENHALL APARTMENTS BOZEMAN, MONTANA STORM DRINAGE BASINS & FACILITY SIZING B23-0267.26.23.DWGFIGURE1CJCEngineering 234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715 406.586.0277 • tdhengineering.comBASIN POST-1:CAVE = 0.87I10 = 0.41A = 0.68 ACV10 = 1,732 CFRRV = 1,121 CFQ25 = 2.47 CFSBASIN POST-2:CAVE = 0.14I10 = 0.41A = 0.04 ACQPRE = 0.51 CFSQ10 = 0.01 CFS 811 W. Mendenhall Apartments Date: 07.26.23 Runoff Calculations "C" 0.9 0.8 0.3 0.1 Pre vs. Post-Development Runoff Coefficient: Total Area (SF)Total Area (Acres) Impervious Area (SF) Gravel Area (SF) Unimproved Area (SF) Landscape Area (SF) Composite "C" Pre 31,377 0.72 5,937 2,062 8,509 14,869 0.35 Post-1 29,461 0.68 28,267 0 0 1,194 0.87 Post-2 1,748 0.04 77 0 0 1,671 0.14 Time of Concentration: Tc* Slope Distance t1 Slope Velocity Distance t2 Velocity Distance t3 Total %ft min %fps ft min fps ft min min Pre 5.64 173 0.35 10.34 0.00 0.491 0.05 0 0.00 3.00 0.00 0.00 10.34 Post-1 5.00 Post-2 4.50 85 0.14 10.07 0.00 0.619 0.06 0 0.00 3.00 0.00 0.00 10.07 * Tc minimum of 5 minutes FHWA HEC 22, Eqn 3-4 Estimate average flow of 3.0 fps K=0.457 Grassed Water Way (Roadside Ditch) K=0.619 Paved Area Cf = 1.0 for 10-year storm event K=0.491 Unpaved shallow concentrated flow Tc*Tc*10 yr Flow C Area Total Total i Q ac min hour in/hr cfs Pre 0.35 0.72 10.34 0.172 2.007 0.51 Post-1 0.00 Post-2 0.14 0.04 10.07 0.168 2.041 0.01 * Tc minimum of 5 minutes Tc*Tc*25 yr Flow C(Cf)Area Total Total i Q ac min hour in/hr cfs Post-1 0.95 0.68 5.00 0.083 3.826 2.47 * Tc minimum of 5 minutes 10-Year Runoff Flow Rate: 25-Year Runoff Flow Rate: Building and Site Areas (Retianed) Roof Drain Tc < 5 Minutes 10-yr, 2-hr Storm Fully Retained Onsite Existing Site Planting Beds West & North (Drains to Alley) Overland Flow Shallow Flow/Gutter Flow Pipe Flow C k Rational Formula "C" Values Per MTDEQ 8: Impervious Area Gravel Area Unimproved Area Lawn/landscape Description 31 11871 / f i S D)CC.(.T −= AiCQ= SkV=28.3 𝑖25 =0.78 ⋅𝑇𝑐−.64 𝑖10 =0.64 ⋅𝑇𝑐−.65 AiCQ= 𝐶𝑓= 1.10 (25-yr) 811 W. Mendenhall Apartments Date: 07.26.23 Retention Volume Sizing & RRV (First 0.5") Calculations Runoff Retention Volume (10-yr, 2-hr): Basin #Basin Description Total Area (SF) Total Area (Acres) Composite Cave CCf (Cf = 1.0) 10 yr - 2hr i (in/hr) Flow Q10 (cfs) Volume V10 (cf) Post-1 Building and Site Areas (Retianed)29,461 0.68 0.87 0.87 0.41 0.24 1,732 Post-Development Condition: Basin #Description Total Area (SF) Total Area (AC) Impervious Area (SF) Gravel Area (SF) Unimproved Area (SF) Landscape Area (SF) Post-1 Building and Site Areas (Retianed)29,461 0.68 28,267 0 0 1,194 Runoff Reduction Volume (First 0.5" of Rainfall): P =0.5 Inches (Water Quality Rainfall Depth) Rv =0.91 (Dimensionless Runoff Coefficient, Rv=0.05+0.9(I) I =95.9%(Percent Impervious Area Draining to Facility) A =0.68 AC (Total Drainage Area) RRV =0.026 AC-FT (Runoff Reduction Volume)* 1,121 CF *RRV = PRvA/12 per Montana Post-Construction Storm Water BMP Design Guidance Manual Eq. 3-1 Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Jul 26 2023 811 W. Mendenhall Drainage Chase Rectangular Bottom Width (ft) = 1.25 Total Depth (ft) = 0.50 Invert Elev (ft) = 100.00 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 2.47 Highlighted Depth (ft) = 0.34 Q (cfs) = 2.470 Area (sqft) = 0.42 Velocity (ft/s) = 5.81 Wetted Perim (ft) = 1.93 Crit Depth, Yc (ft) = 0.50 Top Width (ft) = 1.25 EGL (ft) = 0.87 0 .5 1 1.5 2 2.5 Elev (ft)Depth (ft)Section 99.75 -0.25 100.00 0.00 100.25 0.25 100.50 0.50 100.75 0.75 101.00 1.00 Reach (ft) Groundwater Data Project Name:811 W. Mendenhall Project Number:20-166.10 Date Measured By BH-1 BH-2 BH-3 BH-4 BH-5 10/20/2020 EGS 13.2 11.8 15.2 -- 6/12/2023 Other -~ 9.0 --- 6/20/2023 JGE -Dry at ~ 9.2 --- 7/5/2023 JGE -Dry at ~ 9.2 --- 7/12/2023 JGE -Dry at ~ 9.2 --- 7/24/2023 JGE -Dry at ~ 9.2 -11.5 7.5 Slightly wet at very bottom of well Depth to GW Below Existing Grade (ft) FIGURECivil Engineering Geotechnical EngineeringLand Surveying 32 DISCOVERY DRIVE . BOZEMAN, MT 59718PHONE (406) 582-0221 . FAX (406) 582-5770www.alliedengineering.com 811 W. MENDENHALL BOREHOLE LOCATION MAP BOZEMAN, MONTANA 3 BH- # BH-1 N BH-2MW-1 BH-3 BH-4MW-2 BH-5 MW-3 DEPTH (FT)GEOLOGYLOGDESCRIPTIONOF MATERIALS SAMPLESN(UNCOR)BLOWS/FTMOISTURECONTENTOTHER FIELD ORSAMPLEINFORMATION 2.0 Geotechnical Engineering 32 DISCOVERY DRIVE BOZEMAN, MT 59718 FAX (406) 582-5770 PHONE (406) 582-0221Land SurveyingCivil Engineering Structural Engineering LOG OF BORING PROJECT: 811 W. Mendenhall JOB #: 20-166 DATE: 10/20/2020 PAGE:1 of 1 LOCATION: Bozeman, MT ELEVATION: N/A DEPTH: 15.5' GW: 13.2' DRILL TYPE: Mobile B-61 FIELD ENGINEER: EGS BORING: BH-1 DRILLER: Steve w/O'Keefe CASING/HAMMER/SAMPLER: 6"/4"/140 lb. SSS General Notes:1. Borehole conducted on northernportion of project site onundeveloped lot.2. Ground surface covered with tallgrass.3. Coordinates for borehole locationare 45.68080, -111.04789. ·The beginning and endingdepths of the individual soillayers are approximate. End of Boring {0.0' - 1.0'}: TopsoilStiff; dark brown; organic sandy SILT withsmall roots; moist.S1-A @0.0'-1.5' 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 {1.0' - 7.0'}: Flood DepositStiff; light brown; sandy SILT/CLAY; slightly moist to moist. ·Fast/smooth drilling down to 7.0'. {7.0' - 15.5'}: AlluviumVery dense; brown; sandy GRAVEL withrounded cobbles; slightly moist to wet. ·Target bearing layer. ·Becoming denser and moister withdepth. ·2"-minus rounded cobbles observedin drill cuttings. ·Drilling grinding beginning at 7.0 to15.5'. ·Groundwater encountered at 13.2'. S1-B @2.0'-3.5' S1-C @4.0'-5.5' S1-D @7.0'-8.5' S1-E @9.0'-10.5' S1-F @12.0'-13.5' S1-G @14.0'-15.5' 5/6/612 6/6/410 3/4/48 16/34/3670 21/41/2162 10/19/2443 50-5" 10.0% NA 10.5% 3.7% 4.2% 12.9% 10.8% DEPTH (FT)GEOLOGYLOGDESCRIPTIONOF MATERIALS SAMPLESN(UNCOR)BLOWS/FTMOISTURECONTENTOTHER FIELD ORSAMPLEINFORMATION 2.0 Geotechnical Engineering 32 DISCOVERY DRIVE BOZEMAN, MT 59718 FAX (406) 582-5770 PHONE (406) 582-0221Land SurveyingCivil Engineering Structural Engineering LOG OF BORING PROJECT: 811 W. Mendenhall JOB #: 20-166 DATE: 10/20/2020 PAGE:1 of 1 LOCATION: Bozeman, MT ELEVATION: N/A DEPTH: 15.5' GW: 11.8' DRILL TYPE: Mobile B-61 FIELD ENGINEER: EGS BORING: BH-2 DRILLER: Steve w/O'Keefe CASING/HAMMER/SAMPLER: 6"/4"/140 lb. SSS General Notes:1. Borehole conducted on centerportion of project site. (North ofexisting building).2. Ground surface covered withshort grass.3. Coordinates for borehole locationare 45.68067, -111.04788.4. 4"PVC piezometer placed inborehole for future monitoring.Piezometer is 10' long. ·The beginning and endingdepths of the individual soillayers are approximate. End of Boring {0.0' - 1.0'}: TopsoilStiff; dark brown; organic sandy SILT withsmall roots; moist.S2-A @0.0'-1.5' 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 {1.0' - 6.5'}: Flood DepositMedium stiff; light brown; sandy SILT/CLAY; slightly moist to moist. ·Fast/smooth drilling down to 6.5'. Atterberg Limits: S2-C at 4.0 to 5.5'PL = 21.8LL = 31.3PI = 9.5USGS Classification: CL (Lean CLAY) {6.5' - 15.5'}: AlluviumVery dense; brown; sandy GRAVEL withrounded cobbles; slightly moist to wet. ·Target bearing layer. ·Becoming denser and moister withdepth. ·1"-minus rounded cobbles observedin drill cuttings. ·Drilling grinding beginning at 6.5 to15.5'. ·Groundwater encountered at 11.8'. S2-B @2.0'-3.5' S2-C @4.0'-5.5' S2-D @7.0'-8.5' S2-E @9.0'-10.5' S2-F @12.0'-13.5' S2-G @14.0'-15.5' 5/4/48 3/2/35 2/3/36 19/22/2951 12/24/2347 28/38/5088 29/48/4391 15.1% 15.4% 18.4% 3.8% 4.1% 11.1% 11.5% DEPTH (FT)GEOLOGYLOGDESCRIPTIONOF MATERIALS SAMPLESN(UNCOR)BLOWS/FTMOISTURECONTENTOTHER FIELD ORSAMPLEINFORMATION 2.0 Geotechnical Engineering 32 DISCOVERY DRIVE BOZEMAN, MT 59718 FAX (406) 582-5770 PHONE (406) 582-0221Land SurveyingCivil Engineering Structural Engineering LOG OF BORING PROJECT: 811 W. Mendenhall JOB #: 20-166 DATE: 10/20/2020 PAGE:1 of 1 LOCATION: Bozeman, MT ELEVATION: N/A DEPTH: 15.5' GW: 15.2' DRILL TYPE: Mobile B-61 FIELD ENGINEER: EGS BORING: BH-3 DRILLER: Steve w/O'Keefe CASING/HAMMER/SAMPLER: 6"/4"/140 lb. SSS General Notes:1. Borehole conducted on southportion of project site. (South ofexisting building).2. Ground surface covered with sod.3. Coordinates for borehole locationare 45.68051, -111.04783. ·The beginning and endingdepths of the individual soillayers are approximate. End of Boring {0.0' - 1.0'}: TopsoilStiff; dark brown; organic sandy SILT withsmall roots; moist.S3-A @0.0'-1.5' 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 {1.0' - 9.5'}: Flood DepositMedium stiff; light brown; sandy SILT/CLAY; slightly moist to moist. ·Fast/smooth drilling down to 9.5'. {9.5' - 15.5'}: Alluvium Very dense; brown; sandy GRAVEL withrounded cobbles; slightly moist to wet. ·Target bearing layer. ·Becoming denser and moister withdepth. ·3"-minus rounded cobbles observed in drill cuttings. ·Drilling grinding beginning at 9.5 to15.5'. ·Groundwater encountered at 15.2'. S3-B @2.0'-3.5' S3-C @4.0'-5.5' S3-D @7.0'-8.5' S3-E @9.0'-10.5' S3-F @12.0'-13.5' S3-G @14.0'-15.5' 3/4/59 4/4/37 3/3/36 3/3/47 9/34/3468 6/24/3559 50-4" 21.0% 14.2% 13.6% 21.2% 12.6% 8.5% NA