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Home My WebLink AboutSewer and Water Design Report Sewer and Water Design Report Lots 4 & 5, Block 18, Baxter Meadows Subdivision, Phase IIA Located in the S 1/2 of Section 34, T. 1S., R. 5E., P.M.M. City of Bozeman, Gallatin County, Montana Prepared By: •�O: A e �a o o Cotterman w n 15873ES �/CENS � �J� Revised 12/8/22 �FER-LPN� SANITARY SEWER Proposed construction on Lots 4 and 5, Block 18 of Baxter Meadows Subdivision includes one structure per Lot each containing 3,058 square feet of ground floor office space and 1, 3-bedroom apartment and 2, 1-bedroom apartments on the second level. Sanitary sewer service for each structure will be provided by extending the existing 4-inch sewer service stub that was provided to each Lot with the original subdivision infrastructure. Average daily flows from each building were estimated based on number of employees and average daily residential flows from the City of Bozeman Design Standards and DEQ Circular WQB 4. It was estimated that each unit would have 10 employees, each 1-bedroom apartment would house 1 person, and the 3-bedroom apartment would house 2 people. Total Lot Infiltration Rate 150 gallons/acre/day infiltration Lot area: 11,814 ft2 (0.271 acres) (150 gauons/day)(0.271 acres) = 40.68 gallons/day Infiltration acre Estimated Average Daily Sewer Flow per Lot 3,058 sq ft of office space = 10 employees @ 13 gpd/employee = 130 gallons per day 1 Bedroom Apt = 2.17 person/br @ 64.5 gallons per capita per day = 140 gallons per day 1 Bedroom Apt = 2.17 person/br @ 64.5 gallons per capita per day = 140 gallons per day 3 Br Apt=2 17 people per dwelling unit (cr, 64.5 gallons per capita/day=140 gallons per day Total Lot Wastewater Generation Rate = 550 gallons/day/Lot Total Average Daily Wastewater Flow = 2 Lots(550 gallons/day/Lot) = 1,100 gallons/day (0.0017 cfs) Peaking Factor 2 structures(10 employees + 7 residents) people/structure = 34 people Qmax 18+P1/2 Qave — 4+P1/2 (P = Population in thousands) 034)1/2 = Peaking Factor = 18+(0. 4.35 1 4+(0.034) /2 Maximum Daily Flow Peaking Factor x Average Daily Flow + Infiltration = Maximum Daily Flow 4.35(1,100 gallons/day) + 40.68 gallons/day = 4,826 gallons/day Maximum Daily Flow= 4,826 gallons/day (0.0075 cfs) The original Baxter Meadows sewer system was sized using an average daily flow of 3,495 gallons per day per acre. Extrapolating this flowrate for the area of Lots 4 & 5 plus '/z of the adjoining right-of-ways (18,467 sq ft), plus assumed infiltration rate of 150 gallon/acre/day equates to a average daily flow of 1,545 gallons/day. This design capacity is 140 percent greater than the estimated flowrate calculated for the development of Lots 4 and 5. WATER SYSTEM Water service for the project will be provided by branching 2 1-inch water lines off the existing 4- inch water service line provided with the original subdivision infrastructure. Attached in Appendix A is a copy of the City of Bozeman Water Service Calculation Worksheet showing that the 1-inch meter and service are adequately sized to supply the proposed structures. Estimated Average Daily Water Flow per Structure Residential Flows 1 dwelling unit @ 2.11 persons per dwelling unit 170 gallons/day/capita water flow 3 dwelling2.11 persons 170 gallons ( units)( dwelling)( capita /day) = 1,076.10 gallons/day Residential Industrial/Office Flows 10 employees @ 15 gallons/day/employee = 150 gallons/day Industrial/Office Total Average Daily Water Flow 2 structures((1,076.10 + 150)2- s/unit) = 1,226.10 gallons/day Average (1.89 gpm) day Maximum Day and Peak Hour Demands Peaking Factors (from City of Bozeman Design Standards, dated July 2017): -Maximum Day Demand (Peaking Factor= 2.31) -Peak Hour Demand (Peaking Factor = 3.00) Maximum Day Demand = 1,226.10 gpd x 2.31 = 2,832.29 gpd (1.97 gpm) Peak Hour Demand = 1,226.10 gpd x 3.00 = 3,678.30 gpd (2.55 gpm) The Baxter Meadows subdivision was designed using the Bozeman Water Facility Plan and the Bozeman Design Standards in 2004. Applying the same design method to Lots 4 and 5, the average daily water flow, maximum daily demand, and peak hour demand would be calculated as follows: Total Average Daily Water Flow 8 units(2.54 occupants/unit)200 gallons/day = 4,064 gallons/day Average (2.82 gpm) Maximum Day and Peak Hour Demands Peaking Factors (from City of Bozeman Design Standards 2004): -Maximum Day Demand (Peaking Factor = 2.50) -Peak Hour Demand (Peaking Factor = 3.00) Maximum Day Demand = 4,064 gpd x 2.50 = 10,160 gpd (7.06 gpm) Peak Hour Demand = 4,064 gpd x 3.00 = 12,192 gpd (8.47 gpm) Therefore, the proposed construction is within the original Baxter Meadows Subdivision design water demands. Appendix A 1. City of Bozeman Water Service Calculation Worksheets Commercial(2018120 City of Bozeman rater Service Calculation Worksheet Project Address: property Owner: Paradigm Development LLC General Contractor: J and K Contractors Permit Number:_ Proposed Water?deter Size:--_-- UPC Table 610Standard Design Water Sun»ly Fixture Units Annhanres and Fixtures Fixture Units r of Fixtures Total Bathtub/Combination Tub/Shower 4.0 X 4 16 Soaker Tub 10.0 X — _ — Shower(per head) 2.0 X — _ — Clothes washer 4.0 X 3 = 12 Dishwasher 1.5 X 3 = 4S Hose Bibb 2.5 X 1 = 2.5 Additional Hose Bibb(each) 1.0 X — _ — Drinking Fountain 0.5 X — _ — Service/Mop Basin 3.0 X _ — Lavatory Sink 1.0 X 6 = 6 Kitchen Sink 1.5 X 3 = 4.5 Laundry Sink 1.5 X 1 = 1.5 Water closet(1.6 GPF) 2.5 X 6 = 15 Water closet(1.6 GPF-Flushometer tank) 2.5 X — _ — Water closet(fiushometer valve) Table Values — Urinal(flushometer valve) Table Values M — Total Number of Fixture Units Fixture Unit Tables for Determining Water Pipe&Meter Size Pressure Range-46-60 PSI Circle the length in feet to the farthest fixture&applicable service,meter&branch sizes below based on the total number of fixture units detailed above_ i1pC Table 610.4 Maximum Allowable Length in feet Meter& Supply& 60, 80' 100, 150, 209 Sense Branches %11 %11 20 19 17 14 11 %. 1" 39 36 33 28 23 1" 1" 39 39 36 30 25 i4" 1%11 39 39 39 39 39 V. 1%" 78 76 67 52 44 1%" 1%, 78 78 78 66 52 1" 135"/2' 85 85 85 85 85 lf4" 1%, 151 151 151 128 105 2" 135" 151 151 151 150 117 1%" 2" 370 340 318 272 240 2" 2" 370 370 370 368 318 If count is over 370 fixtures,crater demand does not meet table 610.4 submitted by a registered Montana mechanical engineers design,signed and stamped. 04.29.20