HomeMy WebLinkAbout009_Sewer Engineering Report
Engineering Report
Sewer Main Extension
701 N. Ferguson Avenue
February 2023
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
Sewer Mains 1 2/17/2023
Engineering Report
Contents
Note: The Engineering Report format follows DEQ-2 organization. Additional
information required by the City of Bozeman Design Standards is added where
required.
Report Narrative
Chapter 10 – Engineering Reports & Facility Plans
11.1 Engineering Report - General Information
11.11 Problem Defined
11.12 Design Conditions
11.13 Impact on Existing Wastewater Facilities
11.14 Project Description
11.15 Drawings
11.16 Design Criteria
11.17 Site Information
11.18 Alternate Selection/Analysis
11.19 Environmental Impacts
Figures and Tables
Figure 1. Vicinity Map
Figure 2. Sewer Plan
Table 1. Wastewater Generation
Table 2. Sewer Main Conveyance Capacity
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11.1 Engineering Report – General Information
The proposed Trinity Church Development is located northwest of the intersection
of Durston Road and Ferguson Avenue. The proposed project consists of a 2-
phase site plan to construct a church and related accessory facilities. Phase 1 will
include initial construction of the church’s administrative offices and meeting areas,
with Phase 2 including a large addition to the building primarily consisting of a
formal worship facility. The project is proposed on the currently undeveloped 8.818
acre Lot 1 of Diamond Estates Subdivision Number 2 Phase 1 at 701 N. Ferguson
Ave.
The proposed 2-phase Church building will consist of typical uses for a church of
this size. Phase 1 will consist of 10,100 square feet of floor space containing a
ministry center and offices for church staff. Phase 2 will include 30,565 square feet
of floor space and will include classrooms, a nursery, and a large fellowship hall for
worship services. Each phase will include associated parking, sidewalk, signage,
landscaping, etc. to serve the function of the building.
The project will be served by extension of City of Bozeman sewer mains through
the northern parking area of the project. City of Bozeman sewer mains currently
exist in several locations adjacent to the project; 8” sewer mains exist to the south
in Durston Road, and to the east in Ferguson Avenue. The 8” main to the east in
Ferguson also includes two 8” stubs to the property line at the intersections of
Diamond and Carbon Streets. A sewer main extension is proposed from the
northernmost of these 2 stubs.
The Owner’s contact information is:
Gallatin Valley Presbyterian Church a/k/a “Trinity Church”
4720 Classical Way
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
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The location of the Trinity Church Development is shown on the Vicinity Map in
Figure 1.
Figure 1. Vicinity Map, Bozeman, Montana
11.11 Problem Defined
Sanitary sewer service will be provided by a single new 8” main extension
extended from the northernmost of the 2 existing 8” stubs into the subject
tract from Ferguson Avenue. A single 4” service line will extend to the south
and will service the proposed Phase 1 church building, as well as the future
addition in Phase 2. The main will be extended approximately 215’ west in
alignment with the drive aisle of the parking lot, an extension of the
Diamond Street right-of-way. The main extension will terminate in a single
new manhole at this location.
11.12 Design Conditions
Sanitary sewer service 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 wastewater generation for the Trinity Church development has
been determined utilizing values provided in City design standards and
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Facility Plans and is shown in Table 1. For sewer main sizing, typical City of
Bozeman design flows are utilized. The classroom, office, and community
center are each estimated to generate 30 gpd for each 1000 sf of space.
The sanctuary and fellowship hall are each estimated to use 3 gpd/seat. A
peaking factor of 6 was used to determine the peak hour flow rate. The
estimated total project design flow is 2,955 gpd with a peak hour flow of
12.3 gpm.
Table 1 – Wastewater Generation
Estimated Water and Sewer Use and Demands
Phase One #Units Unit Gpd/1000 sf Gallons/day
Office Space 3600 sf 30 108
Community Center 7500 sf 30 225
Phase Two #Units Unit Gpd/Unit Gallons/day
Classroom 5500 sf 30 165
Sanctuary 648 seat 3 1944
Fellowship Hall 171 seat 3 513
Total Domestic Use 2,955
Average Day Demand (gpm) 2.05
Peaking Factor 6.0
Peak Hour (gpm) 12.3
Table 2 – Sewer Capacity
Sewer Main and Services Capacities
Location Site Main Building Service
Pipe Material 8" SDR 35 PVC 4" SDR 35 PVC
Pipe Diameter (in) 8 4
Minimum Pipe Slope (ft/ft) 0.004 0.02
Coefficient of Roughness (n) 0.013 0.013
Depth in Pipe at 75% Full (in) 6 3
Depth of Flow (ft) 0.5 0.25
Pipe Radius (in) 4 2
Pipe Radius (ft) 0.33 0.17
Wetted Perimeter 1.40 0.70
Area of Flow (ft2) 0.28 0.07
Hydraulic Radius 0.20 0.10
Velocity (ft/sec) 2.48 3.50
Maximum Pipe Flowrate (gpm) 312.8 110.2
Peak Hour Flow (gpm) 12.3 12.3
Peak Flow % of Max Capacity 3.93% 11.16%
Table 2, above, shows that an 8” sewer main has a 75% flow depth capacity
of 313 gpm installed at a minimum slope of 0.4%. A 4” sewer service line at
minimum slope (2%) has a 75% flow depth capacity of 110 gpm. Both the
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proposed sewer main and service line have adequate capacity to serve
Trinity Church.
11.13 Impact on Existing Wastewater Facilities
A review of the City of Bozeman 2015 Wastewater Facility Plan identifies
future capacity limitations in the collection system downstream of this
project impacting a large portion of Bozeman. This limitation is not directly
caused by this project, and upgrades to Bozeman’s collections system to
rectify these limitations have been identified as “future improvements”, the
designation for limitations that are not urgent.
11.14 Project Description
The project description is provided at the beginning of the Engineering
Report.
11.15 Drawings
Please see Figure 2, the Sewer Plan, at the end of this report, which shows
the proposed sewer improvements. Plan and profile drawings will be
submitted with the infrastructure design submittals.
11.16 Design Criteria
The Trinity Church Development sewer main extensions will be designed in
accordance with Montana Department of Environmental Quality Circular 2,
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.
11.17 Site Information
The Trinity Church Development project is located at the northwest
quadrant of Durston Road and Ferguson Avenue. The 8.818-acre lot is
currently undeveloped. Adjacent development consists of single-family
residential developments to the north, east, and south. Immediately to the
west of the site is Christ the King Lutheran Church, which closely resembles
both the proposed type and scope of development of this project. On the
north of the site, a 10’ paved pedestrian path is proposed to facilitate
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pedestrian transportation through the site from the surrounding residential
areas to and from the adjacent Meadowlark Elementary School. Due to the
adjacent residential development, utility connections are readily available for
connection around the site. The Vicinity Map, seen in Figure 1 towards the
beginning of this report, shows the location of the proposed development in
relation to the existing development in the area.
The site is not located within the 100-year floodplain.
11.18 Alternative Selection/ Analysis
Due to the project’s location within the City of Bozeman, extension of public
mains was the only sewer collection alternative. Other configurations of
main extensions were considered during design. The selected design was
chosen as the best fit with the site’s constraints and requirements.
11.19 Environmental Impacts
Continued use and new extensions of City of Bozeman municipal sewer
mains has the least environmental impact. No new environmental impacts
will be caused by these sewer main extensions.
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701 N FERGUSON AVEBOZEMAN, MT 59718FIGURE 2SEWER PLAN