HomeMy WebLinkAbout11 Preliminary Water Engineer's Report 03122021Preliminary Engineering Report
Water Main Extension
Community First Griffin Place
March 2021
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
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Preliminary 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. Water Plan
Table 1. Estimated Domestic Water Demand of North and South Buildings
Appendices
Hydraulic Analysis Exhibit (to be provided with final design)
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1.1.1 General Information
The proposed Community First Griffin Place is located southeast of the
intersection of Manley Road and Griffin Drive. Community First Griffin
Place is a planned two building development designed to provide a
plethora of community-focused programs and services focused on
members of the community facing challenges with housing, hunger, and
other hardships. The project is located on an undeveloped 5.24-acre lot.
The proposed development includes two buildings, referred to as the
North Building and the South Building. The North Building will function as
a Food Resource Center providing a new home for both the Gallatin
Valley Food Bank as well as the Fork and Spoon, a “pay what you can”
restaurant, while the South Building will provide emergency housing. Both
buildings will contain additional office space for staff members.
The project will be served by an 8” looped extension of an existing City of
Bozeman water main in East Griffin Drive. The loop will run in a 30’
combined water and sewer easement and generally run along the drive
access of the site. 2 new fire hydrants are proposed as part of this project.
The developer’s contact information is:
HRDC
Heather Grenier
32 South Tracy Ave.
Bozeman, MT 59715
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 Community First Griffin Place is shown on the Vicinity
Map in Figure 1.
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Figure 1. Vicinity Map, Bozeman, Montana
1.1.2 Extent of Water Works System
Water supply to the area is from an existing 12” diameter cast iron water
main running along the south side of East Griffin Drive. This project will
provide approximately 870 linear feet of 8” water main looping from and
back to the existing 12” main in Griffin Drive. Individual fire and domestic
service connections will be made for each of the two buildings, with a curb
stop installed on the easement line. 4 fire hydrants are proposed to serve
the development. A fire hydrant will be installed at each of the 2
intersections of the proposed drive accesses and Griffin Drive as portion
of the currently-underway Griffin Drive Improvements project widening
Griffin Drive in the area. 2 more fire hydrants will be installed along the
drive access on the site. Irrigation will be supplied by a well to be drilled on
the southern portion of the site. The proposed water system improvements
are shown on the Water Plan (Figure 2) at the end of this report.
The Community First Griffin Place 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.
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Construction specifications will be Montana Public Works Standards and
Specifications (MPWSS), and the City of Bozeman Modifications to
MPWSS.
New water mains will be in 30’ wide water and sewer easements and
street rights-of-way running through the property.
1.1.3 Alternate Plans
Due to the project’s location within the City of Bozeman, extension of
public mains was the only water supply alternative. Distribution
alternatives were explored, and the proposed design was selected to
provide main looping and eliminate dead ends.
1.1.4. Site Conditions
The Community First Griffin Place project is located on the south side of
East Griffin Drive at the intersection of Griffin Drive and Manley Road. The
site is primarily undeveloped. The site was previously occupied by a
single-family residence and associated outbuildings. They have since
been demolished. The site is generally flat within the project limits, with
some moderately sloped terrain around drainage ditches in the northeast
of the site and along a tree stand running north and south across the
property.
A geotechnical evaluation was conducted and is provided in a separate
appendix of this submittal. The soils on the site are variable. Geotechnical
investigation revealed that the central and western thirds of the site were
historically used for ponds that have since been filled. Boring logs reveal
encountering this highly variable fill material to a depth of approximately
19’. The eastern third of the site is predominantly native soils, with some
limited fill encountered that is typically associated with demolition of
historic structures. Full geotechnical evaluation results are available in the
attached appendix.
Groundwater monitoring was conducted throughout the 2020 groundwater
season. During the initial site evaluation and monitoring well installation,
groundwater depths ranged from 7.3’ to 13.3’ below grade in the areas of
the site proposed for development. Long term monitoring results found
groundwater wells dry in all visits, to a depth of approximately 9’ below
grade. Based on these results, seasonally high groundwater is assumed
to be at least 9’ below grade. Full groundwater monitoring results are
available in the attached appendix.
Preliminary investigation of the onsite soils indicates the possible
presence of corrosive soils. Soil corrosivity sampling and testing will be
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conducted prior to infrastructure plan submittal to determine if the on-site
soils are corrosive to the proposed water main pipe.
The site is not located within a 100-year floodplain.
1.1.5. Water Use Data
Domestic 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 Community First Griffin Place has been
determined utilizing values provided in City design standards and Facility
Plans and is shown in Table 1. For water main sizing, typical City design
flows are utilized.
Table 1 – Estimated Domestic Water Demand of North and South Buildings
Average Daily Flow Annual Use
North Building
Area
(sf)
#
Units gpd/1000 sf Gpd/Unit Gpd AF/yr
Warehouse / Food Processing Kitchen 16867 100 1,687 1.89
Accessory to Warehouse / Food Processing 4326 30 130 0.15
Accessory Retail 3282 30 98 0.11
Restaurant Indoor Seating Area 1297 500 649 0.73
Restaurant Outdoor Seating Area 664 500 332 0.37
Offices 1776 30 53 0.06
Accessory Spaces 6894 30 207 0.23
Subtotal 35106 3,156 3.53
South Building
Area
(sf)
#
Units gpd/1000 sf Gpd/Unit Gpd AF/yr
Emergency Beds 170 27 4,590 5.14
Office Space 3878 30 116 0.13
Common Areas 2729 30 82 0.09
Circulation, mechanical, walls 10319 0 0 0.00
Storage 2175 0 0 0.00
Bathrooms 3534 30 106 0.12
Subtotal 4,894 5.48
Building Summary Water Total
(gpd) 8,050 Annual Total
(AF/yr) 9.02
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The estimation of the domestic water demand of each building is based on
proposed building use, utilizing standard City of Bozeman design values
for the majority of calculations. Additional analysis was required to
determine a design value for the emergency beds, which is the primary
use of the South Building. City-provided meter readings from the former
Skate Palace, which currently operates as emergency housing for the
homeless, has been used to estimate a flow rate per bed. Meter readings
revealed a remarkably low use per emergency bed of 7.3 gpd/unit, though
there is only month of meter readings available. To be conservative, a
value 50 gpd/unit has been applied in the water use estimate.
Irrigation will be provided by a new well located southeast of the South
Building. Irrigation lines will provide water to site landscaping and will be
maintained by the property owner. Drought tolerant plants and high
efficiency drip irrigation systems are proposed to conserve water. Irrigation
flow requirements have not yet been determined and will be provided by
the landscape architect.
Because the water system will not supply irrigation, large summer peaks
are not anticipated. To estimate peak flows, a peaking factor of 6 was
used to determine the peak hour flow rate. The estimated total project
design flow is 11,960 gpd with a peak hour flow of 49.83 gpm.
Payment of cash-in-lieu of water rights will be used to provide water rights
for this project.
1.1.6. Flow Requirements
As stated previously, the peak hour water demand is estimated to be
49.83 gpm. Fire flows have not been determined yet but will be in
accordance with the 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.
No fire hydrant flow tests were conducted in the immediate vicinity of the
site as part of the City’s 2017 Water Facilities Plan. However, there are
two available tests that were conducted approximately equidistant from
the site, with one test performed upgradient and the other downgradient.
The results of these tests, Test Number 15 and 21, are attached with this
report. Test Number 15 (to the east) resulted in a static water pressure of
137.8 psi, with a residual pressure of 86.1 psi at a flowrate of 3000 gpm.
Test Number 21 (to the west) reported a static water pressure of 123.3
psi, with a residual pressure of 89.1 at 3000 gpm. Based on these tests,
the water system in this area can provide fire flows and peak domestic
demand with little impact on the system pressures. A fire hydrant flow test
will be conducted in closer proximity to the site prior to final design.
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The 2017 City of Bozeman Water Facility Plan did not identify any fire flow
capacity limitations in this area.
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 feet deep and primarily cross
below water mains and services.
1.1.10 Waste Disposal
This section is not applicable.
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
No future extensions of this main are anticipated, as surrounding
properties have all been previously developed.
GRIFFIN DRIVEPROJECT SITE5.24 ACRESNORTH BUILDING27,086 SF FOOTPRINT202 E. GRIFFIN DR.SOUTH BUILDING14,500 SF FOOTPRINT206 E. GRIFFIN DR.MONTANA RAIL LINKPHASE 1PHASE 2C2.0WATER PLANPROFESSIONALENGINEERS &SURVEYORSCOMMUNITY FIRST
GRIFFIN PLACE STAHLYENGINEERING& ASSOCIATESHRDC
202 & 206 EAST GRIFFIN DR.
BOZEMAN, MT