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NORTHWEST CROSSING
WATER SYSTEM IMPROVEMENTS
DESIGN REPORT
February, 2020
PREPARED BY:
MMI #: 5659.005
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Table of Contents
1 EXECUTIVE SUMMARY ...................................................................................................................... 2
2 GENERAL INFORMATION (DEQ 1.1.1) .............................................................................................. 2
3 EXTENT OF WATER WORKS SYSTEM, INCLUDING (DEQ 1.1.2): ................................................. 3
4 ALTERNATE PLANS (1.1.3) ................................................................................................................ 3
5 SITE CONDITIONS (1.1.4) ................................................................................................................... 3
6 WATER USE DATA, INCLUDING (1.1.5): ........................................................................................... 3
7 FLOW REQUIREMENTS (1.1.6) .......................................................................................................... 4
8 SOURCES OF WATER SUPPLY (1.1.7) ............................................................................................. 5
9 PROPOSED TREATMENT PROCESSES (1.1.8) ................................................................................ 5
10 SEWAGE SYSTEM AVAILABLE (1.1.9) ......................................................................................... 5
11 WASTE DISPOSAL (1.1.10) ............................................................................................................ 6
12 AUTOMATION (1.1.11) .................................................................................................................... 6
13 PROJECT SITES (1.1.12) ................................................................................................................ 6
14 FINANCING (1.1.13) ......................................................................................................................... 6
15 FUTURE EXTENSIONS (1.1.14) ...................................................................................................... 6
EXHIBITS
Exhibit A Vicinity Map
Exhibit B Framework Plan- by Norris Design
Exhibit C WaterCAD Model- Phase 1
Exhibit D Northwest Crossing Subdivision Preliminary Plat- Sheet 4
APPENDICES
Appendix A WaterCAD Results
Appendix B NRCS Soil Report
Prepared by:
Morrison-Maierle, Inc.
2880 Technology Blvd. W.
Bozeman, Montana 59771
Phone: (406) 587-0721
Fax: (406) 922-6702
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Northwest Crossing Subdivision: Phase 1
Water Distribution Design Report
1 EXECUTIVE SUMMARY
This report provides a basis for design for Phase 1 of the Northwest Crossing subdivision water
distribution system. The water distribution system serving the Northwest Crossing development
will be designed and installed in accordance with the Montana Department of Environmental
Quality (MDEQ) Circular No. 1; Montana Public Works Standard Specifications (MPWSS); The
City of Bozeman Modifications to MPWSS; City of Bozeman Water Facility Plan; and the City of
Bozeman Fire Service Line Standard.
The design report is to verify that there is adequate volume and pressure to supply domestic
and fire service for Phase 1 of the Northwest Crossing development. The following design report
follows the section numbering of Circular DEQ-1-Standards for Water Works, August 8, 2014
Section 1.1, Engineer’s Report.
2 GENERAL INFORMATION (DEQ 1.1.1)
a. The proposed Northwest Crossing Subdivision encompasses a total of 160.5 acres and
is generally located at the northwest corner of West Oak Street and Cottonwood Road.
The property is within the boundaries of the City of Bozeman, Montana and was
annexed and zoned REMU (130.994 acres) and B2-M (29.513 acres) in January of
2019. See the vicinity map on Exhibit A for location details. Phase 1 consists of
development tracts A-E for a total of 32.9 acres as detailed in the Master Plan
Framework developed by Norris Design (Exhibit B). Also see the Preliminary Plat
(Exhibit D) for the proposed lot breakdown.
The following is the legal description for the property.
Tract 5 of Certificate of Survey No. 2552, located in the NE1/4 of Section 4, Township 2
South, Range 5 East, Principal Meridian, Gallatin County, Montana.
b. The proposed water main infrastructure will be served by the City of Bozeman. The
subdivision will also be served by an extension of the City of Bozeman’s sanitary sewer
collection system.
c. Project Developer
NWX, LLC
PO Box 11890
Bozeman, MT 59719
System Owner
City of Bozeman
PO Box 1230
Bozeman, MT
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3 EXTENT OF WATER WORKS SYSTEM, INCLUDING (DEQ 1.1.2):
The proposed water main is an extension of the City of Bozeman water infrastructure. The new
internal 8-inch lines for Phase 1 will tie into the existing 10-inch main located at the south
boundary along West Oak and a new 16-inch main in Cottonwood Road. Upon full buildout of
the subdivision, there will also be connections to a 12-inch main in Laurel Parkway and a 36-
inch main in Baxter Lane.
Phase 1 of this project involves extending approximately 7,100 feet of a new internal 8-inch
Class 51 DIP water pipe, new fire hydrants, new fire service lines and new domestic water
services. Services will range in size from 1-inch to 6-inches, depending on projected future
building design. Phase 1 infrastructure will include stubs to the west and north for future tie on
locations. See Exhibit C for proposed water main layout.
4 ALTERNATE PLANS (1.1.3)
No alternate plans were considered.
5 SITE CONDITIONS (1.1.4)
The proposed Northwest Crossing subdivision is currently undeveloped agricultural land which
gently slopes from south to north with existing grades of less than 4% and mostly Amsterdam
silt loam, Hyalite-Beaverton complex and Turner loam soil deposits (USDA, Natural Resources
Conservation Service, Web Soil Survey). Seasonal high ground water ranges from 1 foot to
three feet below existing grade and generally flows to the north, northwest.
6 WATER USE DATA, INCLUDING (1.1.5):
The water distribution system serving the proposed project will be designed and installed in
accordance with the Montana Department of Environmental Quality (MDEQ) Circular No. 1;
Montana Public Works Standard Specifications (MPWSS); the City of Bozeman Modifications to
MPWSS; City of Bozeman Water Facility Plan; and the City of Bozeman Design Standards and
Specifications Policy. The following section addresses the design capacity and flow
requirements discussed in Section 8 of DEQ – 1.
The water main extension for Phase 1 of the Northwest Crossing development will service five
parcels of varying land uses, as defined by the Framework Plan by Norris Design (Exhibit B).
The capacity requirement for the water main extension is calculated as follows:
Phase 1 consists of parcels with two different zoning designations. For the purpose of this
report, we will use the areas associated with the Master Site Plan (See the Framework Plan by
Norris Design in Exhibit B). Parcels A, B and C are zoned B2-M and D, and E are zoned REMU.
At this point in the design, A and B are planned to be used as commercial centers while C, D
and E will be multifamily housing. Average and maximum daily demands for the commercial
developments are pulled from Table 3.9 of the City of Bozeman Water Facility Plan prepared by
AE2S in 2017.
For the parcels zoned REMU, the 2017 Bozeman Water Facility Plan lists an average day
demand of 684 gallons per acre per day. While this value may be appropriate for master
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planning, it does not reflect the uses envisioned for this specific project as it appears
significantly low based on a gallon per capita or dwelling unit basis. In order to review the
validity of the 684 gallons per acre per day, we reviewed City of Bozeman plans and documents
and found the latest data for detailed per capita water use in a technical memorandum that was
completed as part of the City of Bozeman 2014 Water Conservation Plan. The average per
capita per day use for residential units was extrapolated from this information to be 87 gallons
per capita per day. Using an estimated 2.17 people per dwelling unit, 87 gallons per capita per
day, and 684 gallons per acre per day results in 3.6 dwelling units per acre. This value is lower
than the expected density for this development. The Unified Development Code and the City of
Bozeman Design Standards were utilized to develop a more accurate estimate of water use.
Unlike other residential zoning districts, the REMU zoning district does not have a minimum
density requirement; however, the form and intensity standards suggest a relative high density.
For comparison purposes, the R-4 zoning district has a minimum density of 8 units per acre.
The design standards identify a density of 10.4 dwelling units per acre for REMU zoned
property. Based on this information, the water use is estimated to be 1,963 gallons per acre per
day (10.4 dwelling units x 2.17 people per unit x 87 gallons per capita per day).
Table 1 – Parcel Demand
Development
Parcel Area (acres)Zoning
Average Day Demand (gal/
acre/day)
Average Daily Flow
(gpm)
Maximum Day
(Gal/acre/day)Max Day Flow (gpm)
A 9.03 B2-M 1285 8.06 2372 14.87
B 8.51 B2-M 1285 7.59 2372 14.02
TOTAL 17.54 -2570 15.65 4744 28.89
Development
Parcel Area (acres)Zoning
Max Number of Units
(10.4 Dwelling Units Per Acre)
Average Daily
Demand (gpm)
Max Day Demand
(gpm)
C*7.58 B2-M 78.83 10.34 23.77
D 3.36 REMU 34.94 4.58 10.54
E 4.42 REMU 45.97 6.03 13.86
TOTAL 15.36 -159.74 20.94 48.17
*Current plan is to develop Parcel C with multi-family residential buildings, not commercial.
Fire Flow
The total water demand for the system includes the Maximum Daily Demand and the maximum
required fire flow of 1,500gpm which based on the predicted building of Type V-A Construction.
Table B105.1(2) of Appendix B of the International Fire Code requires 5,500gpm fire flow for a
building without sprinklers and allows a reduction for buildings with fire sprinklers. The reduced
flow is 25% of the listed flow which is 1,375gpm. The minimum flow is 1,000gpm or 1,500gpm
dependent on if the fire sprinkler system is designed to meet NFPA 13 or NFPA 13R
requirements. For this report, it is conservatively assumed that 1,500gpm will be required. The
Maximum Daily Demand is calculated by multiplying the Average Daily Demand by a peaking
factor of 2.3.
7 FLOW REQUIREMENTS (1.1.6)
Modeling Procedure
Water modeling using the proposed water main locations has been input into WaterCAD V8i
software to assess expected performance of the new distribution network. Water supply from
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the existing City water system has been modeled by a a reservoir and pump along West Oak to
mimic distribution system output. Use of fire hydrant flow data and a reservoir/pump supply is a
commonly used method to build a stand-alone model without reproducing the complete
distribution system. The nearest tests were done by City Water Department staff on the
following hydrants:
Andalusian/Baxter (8/22/18)
Static of 86psi, Residual of 77psi, Pitot of 70psi flowing 1405gpm on a 2.5” nozzle
Abagail Ln/West Oak (8/16/18)
Static of 94psi, Residual of 88psi, Pitot of 82psi flowing 1520gpm on a 2.5” nozzle
The city adjusted pressure downwards 5 feet in this zone in the fall of 2018 after the flow tests
were completed. This results in the pressures listed being 2 psi too high, thus they have been
reduced as follows:
Andalusian/Baxter (8/22/18)
Static of 84psi, Residual of 75psi, Pitot of 68psi flowing 1405gpm on a 2.5” nozzle
Abagail Ln/West Oak (8/16/18)
Static of 92psi, Residual of 86psi, Pitot of 80psi flowing 1520gpm on a 2.5” nozzle
The total water demand for the system includes the maximum daily demand and the required
fire flow of 1,500gpm as determined by the Insurance Services Office (ISO) criteria. The
maximum daily demand is calculated by multiplying the average daily demand by a peaking
factor of 2.3. The minimum pressure used for pipe main sizing was 35-psi during normal uses
and no less than 20-psi residual pressure during fire hydrant full flow condition at any supply
node. A “C” of 130 is used for the Hazen Williams pipe roughness factor.
Modeling Results
The model’s results indicate that 8-inch distribution mains for the Northwest Crossing
development will supply the needed maximum daily flow with fire flow while maintaining the
required 20-psi residual pressure at all points within the modeled area. Pressure during max
day ranges from 59 to 89psi. The available fire flow is 3,500gpm for the development. (See the
WaterCAD model flow results located in the appendix at the end of this report for additional
information).
8 SOURCES OF WATER SUPPLY (1.1.7)
Water is supplied from City of Bozeman
9 PROPOSED TREATMENT PROCESSES (1.1.8)
Not applicable
10 SEWAGE SYSTEM AVAILABLE (1.1.9)
The area is served by the City of Bozeman wastewater treatment facility
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11 WASTE DISPOSAL (1.1.10)
Not applicable
12 AUTOMATION (1.1.11)
Not applicable
13 PROJECT SITES (1.1.12)
The development is bounded by Baxter Lane to the north, Cottonwood Street to the east, Laurel
Parkway to the west and West Oak Street to the south. The wastewater at the site will be
conveyed to the City of Bozeman wastewater treatment facility.
14 FINANCING (1.1.13)
Not applicable
15 FUTURE EXTENSIONS (1.1.14)
Future extension to the remainder of the Northwest Crossing subdivision will occur as the
property is developed. Stubs will be provided at appropriate locations for future expansion.