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HomeMy WebLinkAbout008 Water and Wastewater Analysis WATER AND WASTEWATER ANALYSIS Technical Memorandum FOR: Gallatin Center Phase 5 ZMA Bozeman, MT Prepared By: WWC Engineering 895 Technology Drive, Suite 203 Bozeman, MT 59718 (406) 586-0262 March 2025 Gallatin Center Phase 5 ZMA - Technical Memorandum Page 1 of 2 895 Technology Boulevard, Suite 203, Bozeman, MT 59718 | 406.586.0262 TO: City of Bozeman Engineering Department (Attn: Cody Flammond) 20 East Olive St. Bozeman, MT 57915 FROM: WWC Engineering/Madison DATE: March 19th, 2025 SUBJECT: Gallatin Center Phase 5 ZMA (24626) – Water and Wastewater Analysis The City of Bozeman has requested an analysis of the potential effects on water and sewer demands associated with the proposed zoning change from B-2 and B-P zoning to B-2M zoning on the property located just north of Baxter Lane and just west of North 19th Avenue. This memorandum outlines the change in design of water and sewer demands associated with the zone map amendment. Water Demand Impacts: Development plans for the subdivision have not been formulated at this time; therefore, the average daily water demands were analyzed using the planning values in the City of Bozeman Standards and Specifications Table 4.2.2 per Section 4.2.4. Because the property has two different zoning areas, the approximate area of each zoning was used to create a weighted daily usage demand based on the area of each zoning on the property. Appendix A shows the existing zoning areas. This average daily demand was then multiplied by the peaking factor specified in COB DSSP Table 4.2.3. The fire flow demand outlined in COB DSSP Table 4.2.4 was then added to calculate the total demand. Using this method, the total design water demand for the existing B-P and B-2 zoning would amount to 3,059.6 gallons per minute. Using the same methods to analyze the daily water usage demands for the property with the proposed B-2M zoning, the daily water usage would be 3,649.1 gallons per minute. The water demand calculations for existing and proposed zoning are outlined in Appendix B. Wastewater Demand Impacts: Wastewater demands were analyzed in accordance with City of Bozeman Standards and Specifications Section 5.2.6, utilizing the values in Table 5.2.1. Similar to the water analysis, this analysis used the approximate area of each zoning (B-2 and B-P) on the property to create a weighted demand. Using the tabled values for domestic flow, including the infiltration rate, and the acreage of the property, along with the peak hour factor, the average wastewater flow rate with the existing zoning is 92 gallons per minute. Using the same method, the proposed zoning of B-2M would increase the design average daily usage demand to 510 gallons per minute. The wastewater demand calculations for the existing and proposed zoning can be found in Appendix C. Conclusion: Table 1 below outlines the changes in calculated water and sewer demands based on existing and proposed zoning. Gallatin Center Phase 5 ZMA - Technical Memorandum Page 2 of 2 Table 1: Design Water and Wastewater Demands Based on Zoning Zoning B-P/B-2 (Existing) B-2M (Proposed) Design Water Demand 3,059.59 gpm (6.82 cfs) 3,649.14 gpm (8.13 cfs) Design Wastewater Demand 92 gpm (0.21 cfs) 510 gpm (1.14cfs) In summary, while the property is currently undeveloped and has no active development plans, the proposed zoning change will increase the design water and wastewater demands. The increase in design demand will be considered in future planning to ensure adequate infrastructure. The detailed calculations for both water and wastewater demands are outlined in the accompanying appendices. Appendix: A. Existing Zoning Areas B. Water Demand Calculations C. Wastewater Demand Calculations Appendix A – Existing Zoning Areas Appendix B – Water Demand Calculations Design Water Usage Analysis Gallatin Center Phase 5 ZMA Existing Zoning (BP and B-2) Average Day Demand Zoning B-2 Area 37.64 acres Average Day Demand 614 gpad COB DSSP Table 4.2.2 Average Daily Demand 23,111 gpd Zoning B-P Area 30.69 acres Average Day Demand 179 gpad COB DSSP Table 4.2.2 Average Daily Demand 5,494 gpd Total Design Average Daily Demand 28,604 gpd Fire Flow Demand Design Fire Flow 3,000 gpm COB DSSP Table 4.2.4 (Community and Neighborhood Business) Peak Hour Water Usage Peaking Factor = 3.0 COB DSSP Table 4.2.3 Average Daily Usage 28,604 gpd Maximum Hour Usage 85,813 gpd Maximum Hour Usage 3575.6 gph Maximum Hour Usage 59.6 gpm Total Max. Hour Usage (including Fire Flow)3059.59 gpm Total Max. Hour Usage (including Fire Flow)6.82 cfs x x 23,111𝑔𝑝𝑑+5,494𝑔𝑝𝑑= Design Water Usage Analysis Gallatin Center Phase 5 ZMA Proposed Zoning (B-2M) Average Day Demand Zoning B-2M Area 68.33 acres Average Day Demand 4,560 gpad COB DSSP Table 4.2.2 Average Daily Demand 311,585 gpd Fire Flow Demand Design Fire Flow = 3,000 gpm COB DSSP Table 4.2.4 (Community and Neighborhood Business) Peak Hour Water Usage Peaking Factor = 3.0 COB DSSP Table 4.2.3 Average Daily Usage 311,585 gpd Maximum Hour Usage 934,754 gpd Maximum Hour Usage 38948.1 gph Maximum Hour Usage 649.1 gpm Total Max. Hour Usage (including Fire Flow)3649.14 gpm Total Max. Hour Usage (including Fire Flow)8.13 cfs x Appendix C – Wastewater Demand Calculations Design Wastewater Usage Analysis Gallatin Center Phase 5 ZMA Existing Zoning (BP and B-2) Average Daily Flow Zoning B-2 Area 37.64 acres Domestic Flow + Infiltration Rate 630 gpad COB DSSP Table 5.2.1 Average Daily Flow 23,713 gpd Zoning B-P Area 30.69 acres Domestic Flow + Infiltration Rate 280 gpad COB DSSP Table 5.2.1 Average Daily Flow 8,593 gpd Total Design Average Daily Flow 32,306 gpd Peak Hour Factor: Equivalent Population Total Average Daily Flow 32,306 gpd Per Capita Flow Rate 117 gal/capita COB Wastewater Facility Plan Equivalent Poppulation 276 = (32,306 gpd/117gal per capita) =Q(max)= 18 + P 0.50 P = Population/thousands =254/1000 = 0.276 Q(ave)4 + P 0.50 Peak Hour Factor = 4.09 Peak Hour Demand Average Day Demand 32,306 Peak Hour Demand 132,133 gpd Peak Hour Demand 5,505.55 gph Peak Hour Demand 92 gpm Peak Hour Demand 0.20 cfs Peaking Factor x x 23,713𝑔𝑝𝑑+8,593𝑔𝑝𝑑= Design Wastewater Usage Analysis Gallatin Center Phase 5 ZMA Proposed Zoning (B2-M) Average Daily Flow Zoning B-2M Area 68.33 acres Domestic Flow + Infiltration Rate 2950 gpad COB DSSP Table 5.2.1 Average Daily Flow 201,574 gpd Peak Hour Factor: Equivalent Population Total Average Daily Flow 201,574 gpd Per Capita Flow Rate 117 gal/capita COB Wastewater Facility Plan Equivalent Population 1723 = (201,574 gpd/117gal per capita) =Q(max)= 18 + P 0.50 P = Population/thousands =1723/1000 = 1.723 Q(ave)4 + P 0.50 Peak Hour Factor = 3.64 Peak Hour Demand Average Day Demand 201,574 Peak Hour Demand 733,728 gpd Peak Hour Demand 30,572 gph Peak Hour Demand 510 gpm Peak Hour Demand 1.14 cfs Peaking Factor x