HomeMy WebLinkAboutDesignReportValleyWestSewerTrunkLine DESIGN REPORT
FOR
VALLEY WEST SEWER TRUNK LINE
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BOZEMAN, MONTANA
Prepared By: Morrison-Maierle, Inc.
901 Technology Boulevard
P.O. Box 1113 <$
Bozeman, Montana 59771-1113
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Prepared by: Jack R. Schunke
Glenn A. Wood
Morrison-Maierle, Inc. No. 2885.004.040.0310
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' C" 7.4 : FL ar 0 9 1998,
VALLEY WEST TRUNK LINE
TABLE OF CONTENTS
1.0 Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pagel
2.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pagel
3.0 Existing Valley Unit Sewer Trunk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
4.0 Proposed Service Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
5.0 Predicted Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 3
6.0 Predicted Wastewater Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4
7.0 Peaking Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 5
8.0 Sewer Trunk Line Sizing by Drainage Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 6
9.0 Valley West Trunk Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9
10.0 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page10
LIST OF TABLES
Table 4.1 Proposed Service Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 3
Table 5.1 Predicted Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4
Table 6.1 Predicted Wastewater Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 5
Table 8.1 Trunk Line Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 7
Table 9.1 Valley West Project Percent of Total Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 9
Table 9.2 Required Line Size for Valley West Project Only . . . . . . . . . . . . . . . . . . . . . . . Page 10
LIST OF FIGURES
Figure
1.1 Service Area
1.2 Valley West Sewer Trunk
8.1 Valley West Sewer Trunk Drainage Zones
Page 1
LIST OF APPENDICES
Appendix
A Line Calculations
LIST OF REFERENCES
Wastewater Facility Plan
Bozeman, Montana -May 1997 -pp 83-87.
Metcalf and Eddy 3`d Edition
Wastewater Engineering, Table 2-5 pp 20, Table 2-11 pp 28.
Page 2
VALLEY WEST SEWER TRUNK
DESIGN REPORT
1.0 Executive Summary
The 360 Ranch Corporation proposes to develop a 404 acre tract west of Ferguson
Avenue and south of Durston Road to be called Valley West. At this time, this area is
without sewer service, therefore the Valley West Sewer Trunk Line will be built and will
serve those areas included in the Valley West Annexation, which includes the Valley West
Project, Bozeman Athletic Club West Annexation and that area 300 feet north of Durston
Road beginning 1,320 feet west of the proposed alignment for Cottonwood Road eastward
along Durston to Flanders Mill Road and that area between Flanders Mill Road, from 400
feet north of the proposed trunk line south to Durston Road, and the connection to the City's
existing wastewater system. Total area to be served is 726 acres. (See Service Area Figure
1.1).
The proposed trunk line will consist of approximately 16,500 feet of eight inch,ten
inch, twelve inch, eighteen inch and twenty-one inch PVC pipe. (See Valley West Trunk
Line Figure 1.2).
Predicted wastewater generation for the 726 acres to be served by the trunk line is
1,031,160 gpd. The entire area is subject to high groundwater therefore infiltration(I/I)will
be included with the wastewater flows predicted. (I/1) into the new line is based on
Bozeman's May 1997 Wastewater Facilities Plan suggestion, (150 gpd per acre), for newly
constructed sewer mains or 108,900 gpd for this project.
Due to the topography of the area,the trunk line will be laid at nearly minimum grade
from the connection to Bozeman's sewer system westward to the future intersection of
Durston Road and Cottonwood Road. Hydraulic analysis completed during the design of the
trunk line indicates that each line will flow the predicted peak flows with used capacity
ranging from 13%to 98%of full flow capacity.
2.0 Introduction
The proposed Valley West Sewer Trunk will connect to the City's existing
wastewater system's Valley Unit Trunk Line at Manhole #946, approximately 3,850 feet
northeast of the intersection of Durston Road and Flanders Mill Road, and extend west and
south along the future extension of Cottonwood Road to a point approximately 400 feet north
of Huffine Lane. The trunk line will follow the alignment of Cottonwood Road, Durston
Road and Flanders Mill Road where possible and will be centered in a 30 foot utility
easement in those areas where the trunk line crosses private property.
Valley West Sewer Trunk Line
Design Report Page 1
3.0 Existing Valley Unit Sewer Trunk
The Valley Unit Sewer Trunk,an existing 18-inch line,extends 2,640 feet north from
Durston Road, approximately 2,800 feet east of Ferguson Road, to Manhole #946, the
proposed point of connection. At Manhole #946, the existing trunk line increases in size
from an 18-inch line to a 20-inch line.
4.0 Proposed Service Area
The service are for the proposed trunk line will consist of the Valley West
Annexation, the Bozeman Athletic Club West Annexation, and those properties lying 300
feet north of Durston Road beginning 1,320 feet west of the proposed alignment for
Cottonwood Road, eastward along Durston to Flanders Mill Road, and that area between
Flanders Mill Road from 400 feet north of the proposed trunk line south to Durston Road,
and the connection to the City's existing wastewater system. (See Table 4.1).
Valley West Sewer Trunk Line
Design Report Page 2
Table 4.1 Proposed Service Area
Area Served Area(Ac)
Valley West Annexation
0 Valley West 344.5
® Billion Auto Plaza Subdivision 19.5
e Norton Ranch Inc. 40.0
Bozeman Athletic Club West Annexation 135.0
Christian Heritage School 13.0
Area North of Durston Road
• Cannon/White 6.0
• Swenson 10.0
• Tom Lane 0.5
6 Mengel Trust 4.0
® Hanson Trust 4.5
6 Anderson/Nelson 10.0
• Metcalf 2.0
i Douglas Smith 72.0
• Douglas Smith 20.0
• Joan Lewis/MacDonald 45.0
Total 726.0
5.0 Predicted Population
Population density for this report will be based on findings detailed in the Bozeman
May 1997 Wastewater Facility Plan, page 87. The plan indicates that an overall density
prediction of 13.3 persons per acre should be used for new development.
Valley West Sewer Trunk Line
Design Report Page 3
Exceptions to the plan's recommendations are: the Christian Heritage School in
which the population is known. Bronken Park in which it is assumed maximum event
attendance would be 1500 people. The exclusion of the 10 acre lake being constructed in the
western section of Valley West.
Infiltration (I/I) allowance of 150 gallons per acre per day will be assumed
corresponding to the City of Bozeman's "Wastewater Facility Plan" page 87. This is
equivalent to 1.3 persons per acre of wastewater generation. (See Table 5.1)
Table 5.1 Predicted Population
Service Area Area(Ac) Population (I/1)
(Person) Persons
Valley West Annexation
• Valley West 292.5* 3891 381
• Billion Auto Plaza Sub. 19.5 260 25
• Norton Ranch Inc. 40.0 532 52
Bozeman Athletic Club Annexation 135.0 1796 176
Area North of Durston Road 174.0 2315 227
Christian Heritage School 13 98 students 17
8 staff
Total 674 Acres F 8898 1 878
* Less area for Bronken Park and proposed lake in western part of project.
6.0 Predicted Wastewater Generation
Wastewater generation predicted in this report is based on findings detailed in the
Bozeman May 1997, Wastewater Facility Plan, page 87. The plan indicates that an overall
wastewater flow of 117 gpd per person should be used for new development.
Wastewater generation for Bronken Park is based on 8 gpd/visitor. This information
is based on Metcalf and Eddy 3`a Edition, Wastewater Engineering Table 2.5, page 20.
Wastewater generation for the Christian Heritage School is 16 gpd/staff and 25
Valley West Sewer Trunk Line
Design Report Page 4
gpd/student. This information is based on Metcalf and Eddy, 311 Edition, "Wastewater
Engineering", Table 2-11,page 28 (See Table 6.1 for predicted wastewater generation).
Table 6.1 Predicted Wastewater Generation
Service Area Wastewater I/I (gpd)
Generation
(gpd)
Valley West Annexation
• Valley West 455,247 44,577
• Bronken Park 12,000
® Billion Auto Plaza Sub. 30,420 2,925
('2124� �3.0 -t (ajp<��,�
A Norton Ranch Inc. 62,244 6,084 q,n r
Bozeman Athletic Club West Annex. 210,132 20,592
Area North of Durston Road 270,855 26,559
Christian Heritage School 2,578 1,989
Subtotal 1,043,476 gpd 102,726 gpd
Total 1,146,202
7.0 Peaking Factor
Peaking factors will be determined using the following formula:
Q (Peak/hourly)/Q (Design ave.) = 18 +IP -
4 +,rP
Where Q =Flow
P =Population in thousands
Note: (Population will consist of predicted residential and commercial population based on
13.3 persons/acre).
Valley West Sewer Trunk Line
Design Report Page 5
8.0 Sewer Trunk Line Sizing by Drainage Zone
Figure 8.1 "Valley West Sewer Trunk Line Drainage Zones", graphically details each
drainage zone and section of sewer trunk line used in the "Trunk Line Computation Table",
Table 8.1. Appendix A, Line Calculations contains the flow calculations for each of the 11
lines which make up the trunk line.
Y
Valley West Server Trunk Line
Design Report Page 6
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9.0 Valley West Trunk Line
The Valley West trunk line is designed with sufficient capacity to serve areas outside
the Valley West project. The flows predicted for the additional areas require that the trunk
line size be increased beyond what is necessary to carry the predicted flows for the Valley
West project in some portions of the trunk line.
Two approaches are used to illustrate the oversizing of the trunk line.
Approach number one compares the overall flow predicted for the Valley West
project as a percentage of the total flow predicted. (See Table 9.1).
Table 9.1 Valley West Project Percent of Total Flow
Service Area Area
Valley West 292.5 acres 455,160 gpd
Subtotal 455,160 gpd
Billion Auto Plaza Sub. 19.5 acres 30,344 gpd
Norton Ranch Inc. 40.0 acres 62,244 gpd
Bozeman Athletic Club West Annexation 135.0 acres 210,074 gpd
Christian Heritage School 13.0 acres 2,578 gpd
Area North of Durston Road 174.0 acres 270,761 gpd
Subtotal 576,001 gpd
Total 1,031,160 gpd
Valley West contribution to the total flout 44.1%.
In approach number two, each line component of the trunk line is sized to carry flow
predicted for Valley West. (See Table 9.2).
Valley West Sewer Trunk Line
Design Report Page 9
Table 9.2 Required Line Size for Valley West Project Only
Line Number Line Size Designed Line Size Designed
for Valley West Trunk for Valley West
Project Only
1 8" 8"
2 8" 8"
3 10" Not Required
4 12" 8"
5 12" 10"
6 18" 15"
7 18" 15"
8 18" 15"
9 18" 15"
10 21" 15"
11 21" 15"
10.0 Conclusion
Using the Bozeman May 1997 Wastewater Facility Plan as a guide,the Valley West
Trunk Line is designed to serve the 726 acres described in this report. At full buildout of the
described area, it is predicted that up to 98% of the full flow capacity of the trunk line in
several areas will be utilized. Construction of the project is expected to begin in the spring
of 1998, and be completed by mid-summer of that year.
The trunk line will be constructed in accordance with Montana Public Works(MPW)
Fourth Edition,January, 1996, Standard Specifications in conjunction with City of Bozeman
Modifications to MPW Standard Specifications prepared May, 1997.
Valley West Sewer Trunk Line
Design Report Page 10
FIGURE 8. 1 VALLEY WEST SEWER TRUNK LINE DRAINAGE ZONES
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