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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