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TRADITIONS
5-PLEX
July 2021
Water and Wastewater Engineering Report
Prepared For:
The City of Bozeman
121 N Rouse Ave
Bozeman, MT 59715
Prepared By:
Woith Engineering, Inc.
405 3rd Street NW, Suite 206
Great Falls, Montana 59404
Traditions 5-Plex
Water and Wastewater Engineering Report
Page 3
ENGINEER’S REPORT
GENERAL INFORMATION
a. The proposed 5-plex development is in Traditions subdivision, phase 1 in the
southeast 1/4 of Section 4, Township 2 South, Range 5 East, P.M.M. City of
Bozeman, Gallatin County, Montana. The 5-plex will span from 4390 Brookside
Ln to 4398 Brookside Ln. As per Bozeman municipal code, the homes will be
oriented to face Durston Rd.
Existing sewer and water infrastructure includes a sewer main, and a domestic
water main located in the Brookside Ln right-of-way. Existing sewer and water
service lines link each lot to the mains and are currently stubbed.
The 5-plex will include two 4-bedroom residences and three 3-bedroom
residences. Each have a dishwasher, a clothes washer, a kitchen sink, three
lavatory faucets, three toilets, and three shower heads.
b. Owner contact information: Montana Land Project, LLC
PO Box 2163
Great Falls, MT 59403
c. Stamp included on Cover Page.
1.1 AVERAGE DOMESTIC WATER USE
a. The estimated population served by the system will be assumed to be that determined
by C & H Engineering and Surveying, Inc. in their Water, Sewer, and Roads Design
Report for the Flanders Creek and Rosa Subdivision, which is 12.7 residents (2.54
persons per lot). This number is not expected to change dramatically in the next 20
years or during the life of the development on the lot.
b. Water usage for the proposed development includes domestic water demands
and irrigation demands. The average daily demand during the summer months,
when landscaping requires irrigation, is calculated in this section.
Average Daily Demand
The average daily demand, including domestic demands and irrigation demands,
was calculated based on the following assumptions:
Domestic: 72 gallons per capita per day (C & H Design Report)
Traditions 5-Plex
Water and Wastewater Engineering Report
Page 4
Irrigation: two inches per week during the summer months (June-August).
Assuming approx. 50% of lot area is irrigated.
The average daily domestic demand is calculated as follows:
DDOM = 72 gpcpd(12.7 persons)=914.4 gpd
The average daily irrigation demand during the summer months is calculated as
follows (assuming 50% of total area is landscaped):
DIRR =(2"
week)(1′
12")(7.48 gal
ft3 )(week
7 days)(8955 ft2 landscaping)=1,595 gpd
Thus, the total average daily demand during the summer months, when water usage will be at
its most severe, is 2,509.4 gallons per day. The maximum average daily demand described in
the subdivision water design report is 2,540 gallons per day (200 gpd per person), therefore the
calculated average daily demand of 2,509.4 gpd will not exceed the maximum flow rate.
1.2 PEAK DOMESTIC FLOW DEMAND
The peak instantaneous demand, the theoretical maximum amount of water that is likely
to be used at any given time, was estimated for the project using the AWWA Modified
Fixture Value Method for Domestic and the Required Maximum Flow Rate Calculator for
Irrigation in the Pacific Northwest created by Washington State University.
For the purposes of the analysis, it is assumed that both the 3-bedroom and 4-bedroom
units will have one kitchen sink faucet, three toilets with flush tanks, three lavatory
faucets, one vertical axis clothes washer, two single head showers, and one
dishwasher.
Table 1. Combined fixture value calculation.
Fixture or Appliance Number
Fixture
Value
Pressure-
adjusted
Fixture
Value
Total Fixture
Value
(gpm) (gpm) (gpm)
Faucet (Kitchen Sink) 5 1.8 1.8 9
Toilet (Flush Tank) 15 6 6 90
Faucet (Lavatory) 15 1.5 1.5 22.5
Bathtub 0 8 8 0
Clothes Washer (Vertical Axis) 5 6 6 30
Shower (Single Head) 10 2.5 2.5 25
Dishwasher 5 1.3 1.3 6.5
Combined Fixture Value: 183
Traditions 5-Plex
Water and Wastewater Engineering Report
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The combined fixture value of 183 gallons per minute was applied to the demand
curve shown in Figure 1.
Figure 1. Demand curve for AWWA Modified Fixture Value
Method.
The combined probable peak demand for domestic use is 28 gallons per minute, per
building. Additional irrigation flows must be considered. To estimate the peak irrigation
flow rate, the “Required Maximum Flow Rate” calculator for irrigation in the Pacific
Northwest, developed by Washington State University, was used. Assuming a
maximum use rate of two inches per week, applied to 8955 square feet of landscaping
with an efficiency of 75%, the maximum irrigation flow rate for the development is 1
gallon per minute. Therefore, the total peak instantaneous demand for the development
is 29 gallons per minute.
The acceptable domestic water volume demand outlined in the subdivision water design
report is 34.94 gpm, therefore the peak instantaneous demand of 29 gpm for the
development does not exceed maximum acceptable volume.
2.1 PEAK SANITARY SEWER DESIGN FLOW
Peak Design Flow:
The peak sanitary sewer design flow for the development was estimated using the
wastewater flow rates outlined in Section 3.1 of Montana Department of Environmental
Quality Circular 4 (Section 3.1.2). The proposed 5-plex will produce 914.4 gallons per
day of wastewater flow assuming a daily flow rate of 72 gpm and a population of 12.7
people. The proposed residential units have been assumed to each have 2 residents
Traditions 5-Plex
Water and Wastewater Engineering Report
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for the first bedroom and 1 more resident for each additional bedroom, for a total
estimated population of 22 residents.
A peaking factor, as taken from the C & H design report for the entire subdivision, is applied to
the total daily flow to determine the design flow rate:
Peaking Factor =18 +√P
4 +√P =18 +√0.832
4 +√0.832 =3.85
Therefore, the peak design flow rate for this phase of development is calculated as follows:
Qmax =914.4 ∗(0.13 cf
gal )∗(day
86,400 sec.)∗3.85 =0.0053 cfs
C & H Engineering and Surveying, Inc. determined peak sanitary sewer flow for the entire
Flanders Creek and Rosa Subdivision to be 0.3754 cfs in their Water, Sewer, and Roads
Design Report. The population of the lots of interest, as determined by the C & H Design Report
is 12.7 individuals (2.54 persons per lot). This population is roughly 1.5% of the total number of
residents, which is 831.50. Therefore, the peak sanitary sewer flow demand for the lots of
interest can be determined as follows:
12.7 residents
831.50 residents ∗0.3754 cfs =0.0057 cfs
Therefore, a Qmax of 0.0053 cfs does not exceed the peak acceptable volume of 0.0057 cfs.
REFERENCES
Montana Department of Environmental Quality, “Standards for Water Works”, Circular
DEQ-1
C & H Engineering and Surveying, Inc., “Water System Layout” Water, Sewer, Roads
Design Report – Flanders Creek & Rosa Subdivision
American Water Works Association, “Sizing Water Services Lines and Meters” M22
Third Edition
Washington State University, “System Pumping Requirements” Irrigation in the Pacific
Northwest