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CATRON CROSSING SUBDIVISION
SEWER IMPROVEMENTS
SANITARY SEWER EXTENSION BASIS OF DESIGN REPORT
August, 2018
PREPARED BY:
MMI #: 2605.025
memo
Page 1
TO: Matt Ekstrom, PE
FROM: Celine Saucier, PE
DATE: June 6, 2021
JOB NO.: 1552.089
RE: Sewer Improvement – Vance Thompson Vision
CC:
Urgent For Review Please Comment Please Reply For Your Use
This memo presents the sewer improvements done for the construction of the Catron Crossing
Subdivision as it pertains to the proposed Vance Thompson Vision building on Los 1 & 2. Lots 1
& 2 is included within the previously approved Catron Crossing Subdivision Sewer
Improvements Sanitary Sewer Extension Basis of Design Report, August 2018. This report
attached and has been highlighted reflect the information relevant to Lot 1 & 2.
Since Lots 1 & 2 will be aggregated, the proposed building will be serviced by the existing
service stub into Lot 2. The report calculated that the total peak flows allocated for Lot 1
(6.29gpm) will now also be routed through the 8” main that services Lots 2 & 3 (25.52gpm).
Therefore, the total peak flows into the 8” main will be 31.81gpm with the maximum conveyance
of the main being 520gpm.
For this reason, the sewer mains in the vicinity of this project can handle the increase in flows
from the proposed building on Lots 1 & 2. Refer to the attached Catron Crossing Sewer Report
for additional information.
Table of Contents
INTRODUCTION ........................................................................................................................................... 1
1 PROBLEM DEFINED ........................................................................................................................... 1
2 DESIGN CONDITIONS ......................................................................................................................... 1
3 IMPACT ON EXISTING WASTEWATER FACILITIES ........................................................................ 5
4 PROJECT DESCRIPTION .................................................................................................................... 5
5 DESIGN CRITERIA .............................................................................................................................. 5
6 SITE INFORMATION ............................................................................................................................ 6
7 ENVIRONMENTAL IMPACTS .............................................................................................................. 6
8 OPERATION AND MAINTENANCE .................................................................................................... 6
APPENDICES
None
Prepared by:
Morrison-Maierle, Inc.
2880 Technology Blvd. W.
Bozeman, Montana 59771
Phone: (406) 587-0721
Fax: (406) 922-6702
Written By: DDK Checked By: MEE
Approved By: MEE
PROJECT NO.: 2605.025
1
INTRODUCTION
This design report provides the criteria used as a basis of design for the Catron Crossing
Subdivision sewer main extension improvements project and is submitted in conjunction with
the completed plans and specifications. This report is organized following the outline
recommended in DEQ-2, Section 32.
This project involves the installation of approximately 778 feet of a new 8-inch sewer main
extensions, and approximately five sewer manholes for the remaining development (zoned B-2)
at the Catron Crossing Subdivision (for Lots 2, 3, 4, 5, 8, 9 and 10) located off of Catamount
Street of the portion of the property contained in C.O.S. 1827A. Lot 1 will be served by a future
sewer main to the north that will eventually drain to the proposed Davis Lift Station
(CIP#WWIF24). This project is located within the City of Bozeman, Montana. See the vicinity
map for location details.
1 PROBLEM DEFINED
Future Commercial development is planned for the remaining lots within the Catron Crossing
Subdivision. The project is proposing two 8-inch mains to convey sewer from the proposed
development. This development will connect to the existing 27-inch sewer main that bisects the
property to be extended for Lots 2, 3, 4, 5, 8, 9 and 10. Lot 1 will be served by a future sewer
connection to the north. Comfort Suites on Lot 7 and Taco Bell on Lot 6 is already being served
by existing sewer mains and services (constructed as part of EQ#13-1091).
Sewer facilities included in this project will be designed in accordance with Montana Department
of Environmental Quality (MDEQ) regulations. Adequate capacity will be provided to allow for
growth in areas adjacent to the actual project areas. Flow and population data for the project
will be consistent with the City’s approved Facilities Plan, where applicable.
2 DESIGN CONDITIONS
The sewer main extensions for the Catron Crossing Subdivision which is zoned B-2 (community
business) per the City of Bozeman’s zoning map. The capacity requirement for the sewer main
extension is calculated as follows:
2
Future Construction in Lot 1 Flows connection to a proposed 8-inch sewer main:
Assumptions:
• COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY (Table V-1 Wastewater Flow Rate for
Zoned Undeveloped Areas), Design Standards and Specification Policy, City of
Bozeman)
• Lot 1 Site = 1.04 ACRES
• Sewer Flow Rate = 33.8 Gallons per Capita per Day (Table 2-11 Bozeman Wastewater
Collection Facilities Plan Update)
Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(1.04 ACRES)
Wastewater Flow Rate = 2,080 gpd
33.8 Gallons per Capita per Day
Population = (2,080 gpd)/(33.8 gallons per Capita per Day) = 62 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.29
Peak Flow = 2,080 gpd (avg daily flow) x 4.29 = 8,902 gpd
Peak Flow = 8,902 gpd = 6.18 gpm
Infiltration at Lot 1 = 150 gpd per Acre = 150 gpd x 1.04 acres = 154.5 gpd
Infiltration = 154.5 gpd = 0.11 gpm
Total Lot 1 flow = 6.18 gpm + 0.11 gpm = 6.29 gpm
Future Construction in Lot 2 and 3 Flows connection to a proposed 8-inch sewer main:
Assumptions:
COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY
Lot 2 and 3 Sites = 4.40 ACRES
Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(4.40 ACRES)
Wastewater Flow Rate = 8,800 gpd
33.8 Gallons per Capita per Day
Population = (8,800 gpd)/(33.8 gallons per Capita per Day) = 260 people
3
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.10
Peak Flow = 8,800 gpd (avg daily flow) x 4.10 = 36,080 gpd
Peak Flow = 36,080 gpd = 25.06 gpm
Infiltration at Lot 2 and 3 = 150 gpd per Acre = 150 gpd x 4.40 acres = 660.0 gpd
Infiltration = 660.0 gpd = 0.46 gpm
Total Lot 2 and 3 flow = 25.06 gpm + 0.46 gpm = 25.52 gpm
Future Construction in Lot 8 Flows connection to an existing 8-inch sewer main:
Assumptions:
COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY
Lot 8 Site = 2.84 ACRES
Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(2.84 ACRES)
Wastewater Flow Rate = 5,680 gpd
33.8 Gallons per Capita per Day
Population = (5,680 gpd)/(33.8 gallons per Capita per Day) = 168 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.17
Peak Flow = 5,680 gpd (avg daily flow) x 4.17 = 23,686 gpd
Peak Flow = 23,686 gpd = 16.45 gpm
Infiltration at Lot 8 = 150 gpd per Acre = 150 gpd x 2.84 acres = 426.0 gpd
Infiltration = 426.0 gpd = 0.30 gpm
Total Lot 8 flow = 16.45 gpm + 0.30 gpm = 16.75 gpm
Future Construction in Lots 4, 5, and 9 Flows connection to a proposed 8-inch sewer
main:
4
Assumptions:
COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY
Lot 4, 5, and 9 Site = 6.08 ACRES
Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(6.08 ACRES)
Wastewater Flow Rate = 12,160 gpd
33.8 Gallons per Capita per Day
Population = (12,160 gpd)/(33.8 gallons per Capita per Day) = 360 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.04
Peak Flow = 12,160 gpd (avg daily flow) x 4.04 = 49,126 gpd
Peak Flow = 49,126 gpd = 34.12 gpm
Infiltration at Lot 4, 5, and 9 = 150 gpd per Acre = 150 gpd x 6.08 acres = 912.0 gpd
Infiltration = 912.0 gpd = 0.63 gpm
Total Lot 4, 5, and 9 flow = 34.12 gpm + 0.63 gpm = 34.75 gpm
Future Construction in Lot 10 Flows connection to an existing 27-inch sewer main:
Assumptions:
COB Planning Zone B-2 = 2,000 GAL./ACRE/DAY
Lot 10 Site = 1.49 ACRES
Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(1.49 ACRES)
Wastewater Flow Rate = 2,980 gpd
33.8 Gallons per Capita per Day
Population = (2,980 gpd)/(33.8 gallons per Capita per Day) = 88 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.26
Peak Flow = 2,980 gpd (avg daily flow) x 4.26 = 12,695 gpd
5
Peak Flow = 12,695 gpd = 8.82 gpm
Infiltration at Lot 10 = 150 gpd per Acre = 150 gpd x 1.49 acres = 223.5 gpd
Infiltration = 223.5 gpd = 0.16 gpm
Total Lot 10 flow = 8.82 gpm + 0.16 gpm = 8.98 gpm
Please refer to the table below for comparisons between maximum flows and proposed flows
and see that that proposed piping is adequate.
LOT
PEAK FLOW
(gpm) PROPOSED CONVEYANCE
MAXIMUM FLOW
FOR PROPOSED CONVEYANCE
(gpm)
1 6.29 Future 8-inch sewer main 346
2 & 3 25.52 Proposed 8-inch sewer main 520
8 16.75 Existing 8-inch sewer main 346
4, 5 & 9 34.75 Proposed 8-inch sewer main 346
10 8.98 Existing 27-inch sewer main 3,599
*8-inch pipe at minimum grade (0.4%) with a roughness coefficient (n) value of 0.013
*27-inch pipe at minimum grade (0.067%) with a roughness coefficient (n) value of 0.013
3 IMPACT ON EXISTING WASTEWATER FACILITIES
The existing sewer mains in the vicinity of this project can handle the increase in flows.
4 PROJECT DESCRIPTION
The sewer main extensions for the Catron Crossing Subdivision will include the construction of
approximately 778 feet of 8-inch SDR 35 PVC sanitary sewer main and approximately five 48”
diameter manholes to serve the proposed Catron Crossing Subdivision and surrounding area.
The average sewer depth is approximately 10-feet.
5 DESIGN CRITERIA
Design criteria including average and peak flows as well as sewer depth information were
provided in previous sections. The proposed sewer mains conform to the State’s minimum
vertical and horizontal separation criteria from water mains.
6
The proposed conventional gravity sewer collection system is to be constructed to City of
Bozeman and the 6th Edition of Montana Public Works (MPW) standard specifications. In
particular, the sewer mains shall be 8-inch diameter SDR 35 Polyvinyl Chloride (PVC) pipe. All
manholes shall be standard concrete manholes spaced no more than 400 feet apart.
6 SITE INFORMATION
The project site has been zoned B-2 by the City of Bozeman. The existing site is bound by
Catamount Street to the South and East Valley Center Road to the North-East and an
undeveloped field to the West. The site has existing grades of less than 4% and Turner loam
soil deposits.
7 ENVIRONMENTAL IMPACTS
There are no expected environmental impacts from this sewer main extension, as the City of
Bozeman Wastewater Treatment Plant has more than adequate capacity for this extension.
8 OPERATION AND MAINTENANCE
These sewer lines will be owned, operated, and maintained by the City of Bozeman.
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