HomeMy WebLinkAbout015_PreliminarySewerEngineeringReportBlock4Engineering Report
Sewer Main Extension
South University District
Phase 3 - Block 4
Site Plan Submittal
Updated May 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 5/19/2023
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. C3.0 - Sewer Plan
Table 1. Block 4 Sewer Flow Estimates
Table 2. Capacity of 8” SDR 35 PVC Sewer Main
Table 3. Capacity of Estimated Sewer Flows
Appendices
SUD Phase 3 Sewer Engineering Report
Sewer Mains 2 5/19/2023
11.1 Engineering Report – General Information
The proposed South University District (SUD) Phase 3 Block 4
Development is located southwest of the intersection of South 11th Avenue
and Student Drive. This development will consist of 243 residential units
with 655 bedrooms on an 11.89-acre lot.
Six different building types consisting of 20 unique unit configurations within
the buildings is proposed with this development. The intent of this project is
to create a variety of building types to create a diverse neighborhood in a
growing part of town adjacent to the Montana State University Campus.
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 and sewer mains currently exist
along the North side of the project site along Student Drive.
The developer’s contact information is:
Capstone Builders
Davis Maxwell
431 Office Park Drive
Birmingham, AL 35223
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 Block 4 Development is shown on the Vicinity Map in Figure 1.
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Figure 1. Vicinity Map, Bozeman, Montana
11.11 Problem Defined
Sanitary sewer service will be provided by an existing 8” sewer main
running along Student Drive and an existing 10” sewer main along the west
side of the project going down S 14th Ave. The proposed sewer system
improvements are shown on the Sewer Plan (Figure 2) at the end of this
report.
New sewer mains will be within combined water and sewer easements and
street rights-of-way running through the property. The easements are 30’
wide. No trees are proposed within the water and sewer easements or
within 10’ of water and sewer mains.
Each building will have an individual sewer service from the building to the
main through parking areas and internal streets. Sewer service sizes are
anticipated to be 6” to the building but will be finalized during infrastructure
design.
Sewer Mains 4 5/19/2023
To avoid conflicts with water and sewer services, power and communication
lines are typically placed in easements on the backs or sides of the
buildings.
11.12 Design Conditions
Estimated wastewater generation for Block 4 has been determined utilizing
values provided in City Design Standards and Specifications Policy and is
shown in Table 1. However, for sewer main sizing, typical City design flows
are utilized.
The estimated residential wastewater generation is based on the City of
Bozeman Design Standards. Typical design flow is 89 gallons per day (gpd)
per capita, with an average population of 2.11 people per home. In
accordance with DEQ-2 a peaking factor of 3.91 was used to determine the
peak hour flow rate.
In accordance with City design standards, infiltration and inflow of 150
gpd/acre is added to the domestic wastewater generation. The total design
flow from the Block 4 development is approximately 60,079 gpd, with a peak
hour flow of 163.17 gpm.
Table 1 – SUD Ph3 – Block 4 Estimated Sewer Use
An 8” sewer main at minimum slope (0.4%) has sufficient capacity to
provide sewer service for Block 4 at the estimated flow of 163.17 gpm.
Table 2 shows that an 8” main has a 75% flow depth capacity of 313 gpm
installed at a minimum slope of 0.4%.
Site Area (acres)11.89
Bedrooms 655
Residential Occupants 655
Per Capita Use (gpd)89
Residential Flow (gpd)58,295
Commercial Area (sf)0
Commercial Use (gpd/1000 sf)0
Commercial Flow (gpd)0
Commercial and Residential Flows (gpd)58,295
Commercial and Residential Flows (gpm)40
Inflow & Infiltration (gal/ac/day)150
Inflow & Infiltration (gpd)1,784
Design Sewer Use + Inflow & Infiltration (gpd)60,079
Peaking Factor (PF)3.91
Design Sewer Peak Hour Flow 163.17
Sewer Mains 5 5/19/2023
Table 2 Capacity of 8" SDR 35 PVC Sewer Main
11.13 Impact on Existing Wastewater Facilities
Off-site sewer impacts were evaluated as part of the phase 3 Subdivision
infrastructure review process.
The sewer flow contributions for the proposed development were
determined using the City of Bozeman Design Standards. The proposed
sanitary sewer main extensions that will serve the proposed development
will connect to the existing 8” sewer mains in Student Dr. and 10” main on S
14th Ave at the north end of the site. All the sewer is then conveyed by the
10” sewer running in S 14th Avenue to the 10” main in Stucky Rd. then going
north to Kagy Boulevard and down Willow Way. During the Subdivision
planning phase of Phase 3, it was determined that the 10” main has
adequate capacity to serve future development of SUD Phase 3, annexation
of county properties along Willow Way, future development along Kagy
Boulevard.
Sewer flows generated in Phase 3 of the SUD development will be collected
in the ‘Farmer’s Canal Drainage Basin’ as identified by the City. The new
mains within the SUD Phase 3 subdivision were 8” and 10” and connect to
the 10” sewer main in Willow Way that continues north to the 15” main in
Lincoln Street west through 19th Avenue eventually ending up in the 18”
main in Garfield Street near the Bozeman Gateway Subdivision.
Flows generated by the SUD Phase 3 development were combined with the
estimated flows from currently undeveloped parcels, as well as existing
Sewer Main
Location On-Site
Pipe Diameter (in)8
Minimum Pipe Slope (ft/ft)0.004
Coefficient of Roughness (n)0.013
Depth in Pipe at 75% Full (in)6
Depth of Flow (ft)0.5
Pipe Radius (in)4
Pipe Radius (ft)0.33
Wetted Perimeter 1.40
Area of Flow (ft2)0.28
Hydraulic Radius 0.20
Velocity (ft/sec)2.48
Maximum Pipe Flowrate (gpm)312.8
Peak Hour Flow (gpm)163.2
Peak Flow % of Max Capacity 52%
Sewer Mains 6 5/19/2023
developments (see Fig 3 in Appendix) to determine the impact of capacity
within the downstream mains. The estimates for SUD Phase 3 Block 1, 2,
3, and 4 have been updated based on current proposed development
programming and included in the calculations below in Table 3.
Table 3 shows the combined flows of the Willow Way and Tai Lane
subbasins, -- in addition to anticipated development of un-incorporated
properties in the area -- and evaluates the capacity within the adjacent
sewer collection system. The combined peak flows that eventually end up
in the 15” Lincoln Street main are estimated to be 1,026 gpm; this includes a
90 gpm peak for MSU home football games (established from monitoring),
plus an additional 23 gpm for infiltration within the sewer drainage sub-
basins. The anticipated peak flow of 1,026 gpm is under the capacity of a
15” main at minimum slope (0.21%) flowing 75% full (1,212 gpm).
The approximate 850 LF of sewer main installed within Kagy Blvd
(extending west from the intersection of Willow Way) was conservatively
sized as a 10” main flowing at only 70% Q/Q75.
Table 3: Capacity of Estimated Sewer Flows
1 Slopes either proposed or as-built
2 150 gal/ac/day from COB Design Standards
11.14 Project Description
The project description is provided at the beginning of the Engineering
Report.
11.15 Drawings
Please see sheet C3.0 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 Block 4 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.
(in)(%)(gpd)(unitless)(gpm)(gpm)(gpm)(in)(gpm)(%)
Lincoln 15 0.21%419,685 3.14 1,004 22 1,026 11.25 1,212 85%
Willow 10 0.97%258,238 3.33 598 10 608 7.5 883 69%
Kagy 10 0.28%130,345 3.58 324 10 334 7.5 475 70%
Sewer Main Pipe Size Slope1 Avg Daily
Flow
Peaking
Factor
Peak
Flow Infiltration2 Peak Flow +
Infiltration
Depth of
Flow
75% Depth
Capacity
Flowrate
Capacity
Q/Q₇₅
Sewer Mains 7 5/19/2023
Construction specifications will be Montana Public Works Standards and
Specifications (MPWSS), and the City of Bozeman Modifications to
MPWSS.
11.17 Site Information
The SUD Phase 3 Block 4 site is typical of Bozeman with fine-grained soils
overlying gravel deposits. Geotechnical borings have determined the depth
to gravel ranges from 7.5 to 11 feet. Estimated depth to groundwater
obtained from the geotechnical borings is 8 to 9 feet. If mains are installed
during periods of high groundwater, dewatering may be required.
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.
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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2 10/17/2022 COB SITE PLAN SUBMITTAL ZWL CDP
3 5/19/2023 COB RC SITE PLAN SUBMIT ZWL CDP PROFESSIONALENGINEERS &SURVEYORSSTAHLYENGINEERING& ASSOCIATESTHE FLATS AT
BOZEMAN
CAPSTONE COLLEGIATE
COMMUNITIES LLC
Sewer Mains 1 6/23/2020
Engineer’s Report
Contents
Note: The Engineer’s 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
Table 1. SUD Phase 3 Sewer Flow Estimates
Table 2. Capacity of 8” SDR 35 PVC Sewer Main
Appendices
Sewer Site Plan
Sewer Capacity Analysis Map
Sewer Mains 2 6/23/2020
11.1 Engineering Report
The South University District Phase 3 subdivision is located within the City
of Bozeman at the south-east corner of South 19th Avenue and Kagy
Boulevard. This project will provide right of way dedications for South 17th
Avenue, State Street and Stucky Rd (f/k/a Campus Blvd) and will create 4
developable lots—three of which will be restricted lots. The initial lot for
development is Block 1 Lot 1 which is an approximate net 8.2-acre lot for
subsequent site development. Site development for this subdivision phase
is anticipated to be a commercial emphasis according to the Master Plan.
The restricted, future development blocks (Blocks 2-4) are also included, but
are not proposed for development at this time.
The developer’s contact information is:
RTR Holdings II, LLC.
22 Turtle Rock Court
Tiburon, CA 94920-1300
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 South University District - Phase 3 is shown on the
Vicinity Map in Figure 1.
Sewer Mains 3 6/23/2020
Figure 1. Vicinity Map, Bozeman, Montana
11.11 Problem Defined
The proposed sewer main extensions to serve the SUD Phase 3 Major
Subdivision are shown in Figure 2 Sewer Site Plan. Sanitary sewer service
will be provided by extending the existing 10” trunk main in Kagy Boulevard,
installed during Phase 2 construction to the S 17th Ave mid-block access;
from there, existing mains, 8” mains are proposed to extend through the
new streets, S. 17th Avenue, State Street, and Stucky Rd. The new 8”
mains will be stubbed into the lots for future extensions. This proposed
sewer main size and configuration is in accordance with the 2015 Bozeman
Wastewater Collection Facilities Plan Update.
11.12 Design Conditions
The sewer flow contributed by the proposed South University District Phase
3 was determined using wastewater flow rates by zoned undeveloped areas
per City of Bozeman Design Standards and Specifications Policy, Table V-
1.
The site for Phase 3 Block 1, Lot 1 consists of a net lot area of
approximately 8.2-acres. The commercial flow was estimated by applying
the value from Table V-1 for Community Commercial of 2,400 gal/acre/day
to this acreage.
Sewer Mains 4 6/23/2020
For residential flow, the estimated flow is determined using an average daily
flow rate of 89 gpd/person with 2.11 people per dwelling unit in accordance
with the City of Bozeman Design Standards Utility Design Criteria. It was
assumed that 60 residential units could be developed within future
developments of Block 1.
All analyses include an infiltration rate of 150-gallons/acre/day, and a
peaking factor depending on population served in accordance with the City
of Bozeman Sanitary Sewer System Design Criteria and MDEQ Design
Standards.
In Tables 1a and 1b, the on-site design sewer flow estimates for Phase 3
Block 1 and the entire Phase 3 subdivision are calculated using
recommended flow rates for zoned undeveloped areas in Table V-1 of the
City of Bozeman Design Standards and Specifications Policy.
Table 1a: SUD Phase 3 Block 1 Sewer Flow Estimates
Block 1 (acres)8.2
Estimated Flow (gpd/acre)2400
Lot 1 Commercial Flow (gpd)19,680
Residential Units 60
Residential Occupants (2.11/unit)126.6
Per Capity Use (gpd)89
Lot 1 Residential Flow (gpd)11,267
Commercial and Residential Flows (gpd)30,947
Commercial and Residential Flows (gpm)21
Peaking Factor 3.98
Peak Flow (gpm)85.60
I&I Rate (gal/acre/day)150
I&I Flow (gpd)1,230
I&I Flow (gpm)0.85
Total Daily Flow (gpm)86.45
An 8” sewer main at minimum slope (0.4%) has sufficient capacity to
provide sewer service for Phase 3 Block 1 at the estimated flow of 86.45
gpm. Table 2 shows that an 8” main has a 75% flow depth capacity of 313
gpm installed at a minimum slope of 0.4%.
Impacts of the entire subdivision on the sewer basin are addressed in
Section 11.13.
Sewer Mains 5 6/23/2020
Table 1b: SUD Phase 3 Block 1 Sewer Flow Estimates
SUD Phase
3
Lot Area Average Water Usage Rates
(sf) (ac) *(gal/ac/day) (gpd) (gpm)
BLOCK 1** 458,500 10.5 30,947 21.49
BLOCK 2 495,062 11.4 1,456 16,548 11.49
BLOCK 3 932,671 21.4 1,456 31,175 21.65
BLOCK 4 615,844 14.1 1,950 27,569 19.14
Infiltration 2,502,077 57.4 150 8,616 5.98
Total Estimated Average Ph 3 Flows 114,854 79.76
Table 2 Capacity of 8" SDR 35 PVC Sewer Main
Status Proposed
Location Phase 3
Pipe Material 8” SDR 35 PVC
Pipe Diameter (in) 8
Minimum Pipe Slope (ft/ft) 0.005
Coefficient of Roughness (n) 0.013
Depth in Pipe at 75% Full (in) 6
Depth of Flow (ft) 0.5
Pipe Radius (in) 4
Pipe Radius (ft) 0.33
Wetted Perimeter 1.40
Area of Flow (ft2) 0.28
Hydraulic Radius 0.20
Velocity (ft/sec) 2.50
Flowrate (cfs) 0.70
Maximum Pipe Flowrate (gpm) 313
Peak Flow % of 75% Max Capacity 32.9%
The sewer services have not been sized yet, but will likely be 4” and 6”
depending upon the building fixture units. Services will be sized in
accordance with the Uniform Plumbing Code.
11.13 Impact on Existing Wastewater Facilities
The sewer flow contributions for the proposed development were
determined using the City of Bozeman Design Standards. The proposed
sanitary sewer main extensions that will serve the proposed development
will connect to the existing 10” main in Kagy Boulevard and Willow Way,
constructed during SUD Phase 2. During the development of Phase 2, it
was determined that the 10” main has adequate capacity to serve future
development along Willow Way, future development along Kagy Boulevard,
and undeveloped property to the south of the project.
Sewer Mains 6 6/23/2020
Sewer flows generated in Phase 3 of the SUD development will be collected
in the ‘Farmer’s Canal Drainage Basin’ as identified by the City. The
proposed new mains within the subdivision are 8” and 10” and connect to
the recently-constructed 10” sewer main in Willow Way that continues north
to the 15” main in Lincoln Street west through 19th Avenue eventually
ending up in the 18” main in Garfield Street near the Bozeman Gateway
Subdivision.
Flows generated by the proposed Phase 3 development were combined
with the estimated flows from currently undeveloped parcels, as well as
existing developments (see Fig 3 in Appendix) to determine the impact of
capacity within the downstream mains.
Table 3 shows the combined flows of the Willow Way and Tai Lane
subbasins, in addition to anticipated development of un-incorporated
properties in the area, and evaluates the capacity within the adjacent sewer
collection system. The combined peak flows that eventually end up in the
15” Lincoln Street main are estimated to be 886 gpm; this includes a 90
gpm peak for MSU home football games (established from monitoring), plus
an additional 23 gpm for infiltration within the sewer drainage sub-basins.
The anticipated peak flow of 886 gpm is under the capacity of a 15” main at
minimum slope (0.21%) flowing 75% full (1,212 gpm).
The approximate 850 LF of proposed sewer main extension within Kagy
Blvd (extending west from the intersection of Willow Way) was
conservatively sized as a 10” main flowing at only 48% Q/Q75, because an
8” main neared 75% capacity with estimated peak flows.
Table 3: Capacity of Estimated Sewer Flows
(in)(%)(gpd)(unitless)(gpm)(gpm)(gpm)(in)(gpm)(%)
Lincoln 15 0.21%358,185 3.20 886 23 910 11.25 1,212 75%
Willow 10 0.97%196,737 3.44 469 10 479 7.5 883 54%
Kagy 10 0.28%99,571 3.67 254 10 264 7.5 475 56%
Sewer Main
Pipe
Size Slope1 Avg Daily
Flow
Peaking
Factor
Peak
Flow Infiltration2 Peak Flow +
Infiltration
Depth of
Flow
75% Depth
Capacity
Flowrate
Capacity
Q/Q₇₅
1 Slopes either proposed or as-built
2 150 gal/ac/day from COB Design Standards
Table 3 is a summarization of a detailed analysis into the sub-basins in the
vicinity of the project that contribute to the overall Mandeville Drainage
Basin in the City of Bozeman’s sewer collection network. See Table 4 and
the sewer capacity analysis map (Figure 4) included in the appendix for
additional information.
Sewer Mains 7 6/23/2020
11.14 Project Description
Site development for this subdivision phase is anticipated to be a
commercial emphasis according to the Master Plan on a 10.5-acre site.
The project falls within the Master Planned SUD Residential Emphasis
Mixed Use (REMU) zoning district.
11.15 Drawings
Please see Figure 2, the Sewer Site Plan, included in the appendix,
showing the proposed locations of the subdivision sewer mains. Plan and
profile drawings will be submitted with future infrastructure design
submittals.
11.16 Design Criteria
The South University District Phase 3 sewer main extensions were
designed in accordance with Montana Department of Environmental Quality
Circular 2, Montana Public Works Standards and Specifications, City of
Bozeman Modifications to Montana Public Works Standards and
Specifications, the Uniform Plumbing Code, and the City of Bozeman
Wastewater Facility Plan.
11.17 Site Information
The SUD Phase 3 site is typical of Bozeman with fine grained soils overlying
gravel deposits. Geotechnical borings have determined the depth to gravel
ranges from 7 to 8 feet. Estimated depth to groundwater from the
geotechnical borings is 4 to 8 feet. If mains are installed during periods of
high groundwater, dewatering may be required.
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.
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.
Sewer Mains 8 6/23/2020
Table 4: Sewer Flows and Infiltration by Basin/Sub-basin
(sf) (ac) (gal/ac/day)(gpd) (gpd) (ac) (gpm)
1 R4 Mandeville 90,036 2.1 1950 4,031
2 R1 Mandeville 88,716 2.0 730 1,487
3 RS Mandeville 65,449 1.5 1220 1,833
4 R2 Mandeville 181,359 4.2 980 4,080
5 County A Mandeville 834,350 19.2 730 13,982
6 County B Tai Lane 992,386 22.8 1456 33,171
7 B1 Tai Lane 460,873 10.6 1000 10,580
8 R4 Tai Lane 463,928 10.7 1950 20,768
9 RO Tai Lane 676,957 15.5 980 15,230
10 MSU Stadium Tai Lane 799,299 18.3 500 9,175
11 SUD PH 1B Tai Lane 252,977 5.8 2246 13,043
12 SUD PH 1 Tai Lane 557,933 12.8 2660 34,069
13 REMU Willow Way 625,319 14.4 1456 20,901
14 R4 Willow Way 225,119 5.2 1950 10,078
15 SUD PH 2 Willow Way 843,741 19.4 3073 59,520
16 SUD PH 3 - Block 1 Willow Way 458,500 10.5 4 30,947
17 SUD PH 3 - Block 2 Willow Way 495,062 11.4 1456 16,548
18 SUD PH 3 - Block 3 Willow Way 932,671 21.4 1456 31,175
19 SUD PH 3 - Block 4 Willow Way 615,844 14.1 1950 27,569
Totals 221.78 23.10
DescriptionMap #
Designation1 Sub Basin
25,413 28.92
Average Daily
Water Usage Rates2Area Subbasin
Subtotal
Subbasin
Area Infiltration3
358,185
136,035 96.52 10.05
196,737 96.33 10.03
3.01
1 Numbers Correlate with Figure 3
2 Average Daily Water Usage Rates taken from Table 1-V, City of Bozeman Design Standards and Specifications Policy
3 Infiltration calculated at 150 gal/ac/day per City of Bozeman Design Standards and Specifications Policy
4 See Average Daily Water Usage Calculation in Table 1