HomeMy WebLinkAboutAppendix 7 - Sewer Main Extension Engineer's Report
Cannery District Planned Unit Development
Preliminary PUD Application
Cannery District Partners, llc
Appendix 7
Sewer Main Extension
Engineer’s Report
Sewer Main Extension Engineer’s Report
Cannery District PUD
February, 2015
For Submittal to:
City of Bozeman Engineering Department
20 East Olive
Bozeman, MT 59715
Montana Department of Environmental Quality Permitting and Compliance Division
Public Water and Subdivisions Bureau
PO Box 200901
Helena, MT 59620-0901
Prepared by:
Stahly Engineering and Associates 851 Bridger Drive, Suite 1
Bozeman, MT 59715
(406) 522-9526
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Engineer’s Report
Contents
Note: The Engineer’s Report format for the Cannery District PUD Sewer Main
Extension 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
11.11 Problem Defined
11.12 Design Conditions
11.13 Impact on Existing Wastewater Facilities
11.14 Project Description 11.15 Design Criteria
11.16 Site Information
11.17 Environmental Impacts
Figures and Tables
Figure 1. Vicinity Map
Figure 2. Sewer Site Plan (C3.0 – included separately)
Table 1. Cannery District Sewer Flow Estimates
Table 2. Capacity of 8” and 10” SDR 35 PVC Sewer Main
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11.1 Engineering Report
The Cannery District is a multi-phase development located on the north
side of East Oak Street and Rouse Avenue, north of the Gallatin County
Fairgrounds. The existing property consists of several parcels of land within the City and County, with 3.30 acres within the City and 8.94 acres
within the county.
The development consists of four phases. The first phase was approved
by the City of Bozeman and MDEQ in November 2014. This phase consists of remodeling four existing buildings originally constructed as part
of the original pea canning operation in 1917. During this phase, the
existing water and sewer infrastructure will be replaced and upgraded to
current City standards.
Phases 2, 3 and 4 involve the construction of six new buildings on the
Cannery District property. The wastewater flows from these future phases
were accounted for in the design of the approved Phase 1 system. These
future phases will be annexed prior to development in order to receive
municipal services for new buildings.
The developer’s contact information is:
Cannery District Partners, LLC
1006 W Main Street Bozeman, MT 59715
Water supply and wastewater treatment will continue to 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 Cannery District is shown on the Vicinity Map in Figure
1. See C3.0 for the overall sewer system plan.
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Figure 1. Vicinity Map, Bozeman, Montana
11.11 Problem Defined
City of Bozeman sewer mains were constructed in 1917 to serve the
existing buildings. Nearing 100 years in age, these existing 15” sewer mains have reached the end of their useful life. In addition, the existing sewer network is not configured to support future phases within the
development. The approved Phase 1 sewer upgrades will replace the
existing mains, however, additional sewer mains and services require
extensions in order to serve the future phases. The location of the existing mains, approved Phase 1 sewer mains, and proposed extensions to the sewer system are shown in C3.0, a large map included separately.
11.12 Design Conditions
The sewer flow contributed by the Cannery District was determined using wastewater flow rates for zoned undeveloped areas from the City of Bozeman Design Standards and Specifications Policy, Table V-1. For the
Northside PUD and the portion of the Cannery District that is currently
within city limits, the zoning designation is B-2. The rest of the Cannery
district currently outside of city limits must be annexed prior to development, with the plan being to maintain the same zoning designation of B-2. Table V-1 shows a flow rate of 2000 Gal./Acre/Day for zoning
designation B-2.
To evaluate the overall sewer network, all four phases of the Cannery District and the Northside PUD were evaluated. The Northside PUD has three existing sewer services that connect to the existing sewer main that
serves the Cannery District. As this sewer main will be abandoned, the
Northside sewer services will be connected to the approved Phase 1
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sewer main, and are accounted for in the wastewater flow estimates shown in Table 1, below.
Table 1 Cannery District Sewer Flow Estimates
The approved Phase 1 sewer network consists of both 8” and 10” SDR 35
PVC sewer mains. 8” SDR 35 PVC sewer mains installed at the minimum slope of 0.4% have a flow capacity of 312.8 gpm using 75% of the flow
depth of the pipe as required by the City of Bozeman Design Standards
and Specifications Policy.
10” SDR 35 PVC sewer mains installed at the slope of 0.3% have a flow capacity of 491.2 gpm using 75% of the flow depth of the pipe. See Table
2 below for the parameters used in the flow calculation.
Table 2. Capacity of 8” and 10” SDR 35 PVC Sewer Main
Status Proposed Proposed
Location Cannery District Cannery District
Pipe Material 8" SDR 35 PVC 10" SDR 35 PVC
Pipe Diameter (in) 8 10
Minimum Pipe Slope (ft/ft) 0.004 0.003
Coefficient of Roughness (n) 0.013 0.013
Depth in Pipe at 75% Full (in) 6 7.5
Depth of Flow (ft) 0.5 0.625
Pipe Radius (in) 4 5
Pipe Radius (ft) 0.33 0.42
Wetted Perimeter 1.40 1.75
Area of Flow (ft2) 0.28 0.44
Hydraulic Radius 0.20 0.25
Velocity (ft/sec) 2.48 2.49
Maximum Pipe Flowrate (gpm) 312.8 491.2
Peak Hour Flow (gpm) 212 212
Peak Flow % of Max Capacity 67.77% 43.16%
The 8” sewer at the minimum allowed slope has sufficient capacity to
convey the peak flow from all four phases of the Cannery District,
Cannery District Water Use Phase 1 Phase 2 Phase 3 Phase 4
Total All
Phases
Total
w/Northside
Acreage (acres) 3.761 3.29 3.237 1.946 12.234 15.254
Design Water Use Rate (gpd/acre) 2000 2000 2000 2000 2000 2000
Design Daily Water Use (gpd) 7522 6580 6474 3892 24468 30508
Design Peaking Factor (Ave Day to
Peak Hour) 10 10 10 10 10 10
Design Peak Hour Flow (gpm) 52 46 45 27 170 212
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including the contributions from the Northside PUD. Although 8” pipe provides capacity for the design flow of 2000 gpd/acre, future
development with potentially higher densities may require a larger sewer
at the downstream portion of the project. By installing a 10” sewer main at
the downstream portion of the sewer collection system, a small increased installation cost will provide future flexibility over the 100+ year design life of the sewer.
11.13 Impact on Existing Wastewater Facilities
As previously described, the existing wastewater facilities onsite will be
abandoned and replaced during Phase 1 construction. As the majority of the sewer network will be completed during Phase 1, only one future main
extension will be necessary for the remaining phases (Phase 2 – indicated
by dashed green line on C3.0). During construction of the future phases,
existing sewer services within Phase 1 and Northside PUD will remain in
service.
The Bozeman Waste Water Facility Plan does not indicate any
improvements will be necessary to serve the Cannery District.
11.14 Project Description
Cannery District Phase 1 is the first of four phases within the development. It consists of remodeling four existing buildings originally
constructed as part of the original pea canning operation in 1917. The
existing sewer infrastructure will be replaced and upgraded to current City
standards prior to the construction of the approved Phase 1 site
improvements. This upgrade will also serve the Northside PUD which currently has three services connecting to the existing 15” sewer main that
is being replaced.
The construction of Phase 1 will provide the majority of the infrastructure
needed to serve the remaining phases. Sewer services will be stubbed into phases 3 and 4 for future use, while phase 2 will require an extension
of the 8” main heading to the south.
11.15 Design Criteria
The Cannery District 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.
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11.16 Site Information
A Geotechnical Report was prepared by Allied Engineering Services, Inc.
for the Cannery District site. The report identified the site to contain fine
grained soils overlying gravel deposits. Geotechnical borings have determined the general soil profile consists of 1.5 to 7.0 feet of fine grain silt and clay overlying alluvial gravel. Estimated depth to groundwater
obtained from the geotechnical borings is 6.5 -11 feet. If mains are
installed during high groundwater times dewatering may be required.
11.17 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.
Figure 2
Sewer Site Plan