HomeMy WebLinkAbout19 - Appendix N - Water Main Extension ReportEngineering Report
Water Main Extension
South University District
Phase 3 - Block 1
Updated August 2024
Submitted to:
City of Bozeman Engineering Department
20 East Olive
Bozeman, MT 59715
Prepared by:
Stahly Engineering and Associates
851 Bridger Drive, Suite 1
Bozeman, MT 59715
(406) 522-8594
Water Mains 1 8/5/2024
Engineering Report
Contents
Note: The Engineering Report format follows DEQ-1 organization. Additional
information required by the City of Bozeman Design Standards is added where
required.
Report Narrative
1.1.1 General Information
1.1.2 Extent of water works system
1.1.3 Alternate plans
1.1.4 Site conditions
1.1.5 Water use data
1.1.6 Flow requirements
1.1.7 Sources of water supply
1.1.8 Proposed treatment processes
1.1.9 Sewage system available
1.1.10 Waste disposal
1.1.11 Automation
1.1.12 Project Sites
1.1.13 Financing
1.1.14 Future Extensions
Figures and Tables
Figure 1. Vicinity Map
Figure 2. C2.0 - Water Plan
Table 1. SUD Phase 3 Block 1 Estimated Water Design Flows
Appendices
Hydraulic Analysis Exhibit – to be submitted with infrastructure
DIPRA Analysis
Water Mains 2 8/5/2024
1.1.1 General Information
The proposed South University District Phase 3 Block 1 Development is
located southeast of the intersection of 19th Avenue and Kagy Blvd. This
development will consist of 273 residential units on an 8.3-acre lot.
This project consists of 3 different building types including three flat-style
apartments, one clubhouse and one commercial building. The intent of
this project is to bring 273 high-quality residential units and a commercial
building to a growing part of town adjacent to the university. This
application seeks feedback on the conceptual design and associated site
improvements.
The project will be served by extension of City of Bozeman water and
sewer mains throughout the project. Individual service lines will be
provided to each block of units. City of Bozeman water currently exist
along all four sides of the project site. City of Bozeman sewer currently
exists on the eastern half of the site.
The developer’s contact information is:
Alpenglow of Bozeman LLC
Jim Rooney
13167 County Hwy 00
Chippewa Falls, WI 54729
Water supply and wastewater treatment will be provided by the City of
Bozeman’s municipal systems. The system owner’s contact information is:
City of Bozeman Public Service Department
PO Box 1230
Bozeman, MT 59771-1230
The location of the SUD Phase 3 Block 1 development is shown on the
Vicinity Map in Figure 1.
Water Mains 3 8/5/2024
Figure 1. Vicinity Map, Bozeman, Montana
1.1.2 Extent of Water Works System
Water supply to the area is from an existing 8” diameter water main in S
17th Ave, an existing 8” main in State Street, an existing 12” main in Kagy
Blvd and an existing 24” diameter water main in South 19th Avenue.
New water mains will be in a combined 30-foot-wide water and sewer
easement. New on-site 8” water mains will be looped.
Each structure will have a single water service and fire service from the
main to the riser room, with a curb stop located on the easement or right-
of-way line. Preliminary service sizing indicates a range of 2 to 8” services.
The Block 1 water main extensions have been designed in accordance
with Montana Department of Environmental Quality Circular 1, and the
City of Bozeman Design Standards and Specifications Policy.
Construction specifications will be Montana Public Works Standards and
Specifications (MPWSS), and the City of Bozeman Modifications to
MPWSS.
Water Mains 4 8/5/2024
1.1.3 Alternate Plans
Due to the project’s location within the City of Bozeman, the extension of
public mains was the only water supply alternative. Distribution
alternatives were explored, and the proposed design was selected to
increase looping and minimize dead ends. The use of an on-site well as a
source for irrigation usage is not feasible due to the previously allocated
water rights in the Phase 2 subdivision park.
1.1.4. Site Conditions
The SUD Phase 3 Block 1 site is typical of Bozeman with fine-grained
soils overlying gravel deposits. Geotechnical borings have determined the
depth to gravel ranges from 3.5 to 5 feet. Estimated depth to groundwater
obtained from the geotechnical borings is 9 to 12 feet. If mains are
installed during periods of high groundwater, dewatering may be required.
High groundwater and soil conditions in the area indicate potential for
corrosion of ductile iron pipes. Composite soil samples were collected at
typical depths of water main to test for corrosive soil conditions and found
to be at low risk of corrosion. The full DIPRA Decision Model results and
summary are included as an appendix of this report.
1.1.5. Water Use Data
Domestic and site irrigation water will be provided by the City of Bozeman
Municipal system. This project is located within the planned service area
of the City’s system.
Estimated water use for SUD PH3 Block 1 has been determined utilizing
values provided in City design standards and Facility Plans and is shown
below in Table 1. For water main sizing, typical City design flows are
utilized.
Water Mains 5 8/5/2024
Table 1: SUD Phase 3 Block 2 Estimated Water Design Flows (Need to update
irrigation)
The estimation of the domestic water demand for the project is based on
proposed use and planned density, utilizing standard City of Bozeman
design values for most calculations. Because the proposed development
is multifamily or mixed use, the domestic water use, and irrigation are
calculated separately. The domestic water use is assumed to be the same
as the wastewater generation at 89 gpd per capita. Site irrigation use was
estimated based 25% of the lot and street area being irrigated, at typical
irrigation rates of about 1” per week.
Water rights are provided by payment of cash-in-lieu of water rights, at the
time of lot development as determined during site plan review.
Pool Facilities Maintenance
WATER SUPPLY and MAKING UP WATER:
Replenishing water lost via evaporation or filter cleaning will be “made-up”
through an automated system of 20 gpm, which will have cross-
connection control. There are two options for backflow prevention:
1. A backflow prevention devise on plumbing-trades scope. These
require annual testing.
2. Water Design can specify and design in an “air gap” so that the
water supply does not need a backflow preventer.
SUD Phase 3 Block 1 Estimated Water and Sewer Usage
Site Area (acres)8.3
Residential Units 273
Residential Occupants (2.11/unit)576.03
Per Capita Use (gpd)89
Residential Flow (gpd)51,267
Commercial Area (sf)10,000
Commercial Use (gpd/1000 sf)100
Commercial Flow (gpd)1000
Commercial and Residential Flows (gpd)52,267
Commercial and Residential Flows (gpm)36
Average Day Water Use [Equal to Commercial & Residential Flows](gpd) 52,267
Irrigated Area (ac) = Site Area * 025 2.1
Irrigation Rate (gla/ac/day)4,000
Irrigation (gpd)8,300
Max Day Water Use [Average Day Use + Irrigation] (gpd)60,567
Peaking Factor (PF)3.94
Design Water Peak Hour Flow 165.79
Water Mains 6 8/5/2024
CERTIFIED POOL OPERATOR:
The pool and spa will require a “certified pool operator” (aka CPO) to
manage the pool, test the water, and ensure safety. There are daily tasks
for CPOs or their assignees, such as the following:
• Checking and cleaning pump strainers
• Checking and backwashing filters
• Checking and adjusting water chemistry (mostly automated) and
keeping log-book records for the health department
• Verifying chemical inventory
• Vacuuming pool and cleaning deck, etc.
FILTER CLEANING BACKWASH:
PROCESS: The filters are backflushed (backwashed) approximately once
a week. The rate of backwash cannot be restricted; hence, the differential
between the backwash flow rate and what the sewer system can handle
will be temporarily retained and slowly released into the sewer system.
o Each filter will backwash for five minutes, once per week on
average. There are multiple filters, and the backwashing must
be sequential (not simultaneous) and staggered to allow the
temporary holding tank to drain.
o The largest filter on the Alpenglow project will be backwashed at
88 gpm for five minutes (usually less), producing 440 gallons.
With 50 gpm released down the drain immediately, a volume of
200 gallons will be retained in a jumbo floor sump or in a tank.
o There are five filters, so an average of 2000 gallons per week
will be lost via backwash.
o Another 2,000 gallons of water per week will be lost to
evaporation (less if pool gets covered at night).
POOL DRAINING:
Water Design specifies a valved, 1-inch “evacuation pipe” for the rare
occasion of emptying the pool (only every few years for the pool and a
little more frequently for the spas). The small, 1-inch-diamter “evacuation”
pipe and its throttle valve will keep the pool-draining discharge rate under
the range specified by the sewer design.
• POOL volume: 47,000 gallons
o Fill time at 20 gpm = 40 hours
o Drain time could be up to a few days
• SPA #1 volume: 2,000 gallons
• SPA #2 volume: 2,000 gallons
Water Mains 7 8/5/2024
1.1.6. Flow Requirements
As stated previously, the peak hour water demand is estimated to be
165.79 gallons per min (gpm). Fire flows have not been determined yet
but will be in accordance with the City of Bozeman adopted Uniform Fire
Code. It is anticipated that a fire flow of 1500 gpm will be required. The fire
flow requirement will be the dominant design constraint for system design.
As part of the Phase 3 Subdivision process, a hydraulic analysis was
completed to determine the available fire flow in this area. According to
this analysis, Phase 3 hydrants – including those in Block 1 – will have
available fire flows ranging from 3,122 gpm to 3,606 gpm, with a system
residual pressure of 20 psi.
Fire flow requirements are based on the Uniform Fire Code. The required
hydrant flow is determined using Table H.5.1 of the Uniform Fire Code.
For example, a 48,000 sq ft Type V-A building requires a fire flow of 4,000
gpm. In consideration of the planned use of sprinkler systems in future
Phase 3 site developments projects, the fire department is allowing a 75%
reduction in required fire flows, reducing the hydrant flow down to the
anticipated minimum required fire flow of 1500 gpm. The fire flow required
will be determined by the fire department at the time of infrastructure
design. The total fire flow available will allow for the use of the hydrant and
the sprinkler while maintaining the required 20 psi residual pressure.
The Phase 3 Subdivision Engineer’s report is available upon request.
1.1.7. Sources of Water Supply
This section is not applicable.
1.1.8. Proposed Treatment Process
This section is not applicable.
1.1.9 Sewage System Available
Sewer service is provided by new City mains extended through the site
from the existing sewer main running along the northern portion of the
property. Sewers will be approximately 8.5 feet deep and primarily cross
below water mains and services.
1.1.10 Waste Disposal
This section is not applicable.
Water Mains 8 8/5/2024
1.1.11 Automation
This section is not applicable.
1.1.12 Project Sites
This section is not applicable.
1.1.13 Financing
This section is not applicable.
1.1.14 Future Extensions
The water system layout accommodates future water main extensions as
required to complete future system improvements in this area.
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2 9/29/2023 SITE PLAN SUBMITTAL ZWL CDP
3 1/12/2024 RC SITE SUBMITTAL ZWL CDP
4 5/31/2024 RC 2 SITE SUBMITTAL ZWL CDP
5 8/1/2024 BUILDING PERMIT
SUBMITTAL ZWL CDP
6 8/9/2024 RC 3 SITE PLAN SUBMITTAL ZWL CDP PROFESSIONALENGINEERS &SURVEYORSSTAHLYENGINEERING& ASSOCIATESALPENGLOW APARTMENTS
SUD PH3 BLOCK 1
ALPENGLOW
OF BOZEMAN, LLC