HomeMy WebLinkAboutB_Bozeman East Sewer Eng Report Signed 12-18-2020
BOZEMAN EAST MIXED-USE
SEWER SYSTEM IMPROVEMENTS
SANITARY SEWER EXTENSION BASIS OF DESIGN REPORT
March, 2019
PREPARED BY:
MMI #: 3959.022
Table of Contents
1 EXECUTIVE SUMMARY ...................................................................................................................... 1
2 PROBLEM DEFINED (DEQ 11.11) ...................................................................................................... 1
3 DESIGN CONDITIONS (DEQ 11.12) ................................................................................................... 1
4 IMPACT ON EXISTING WASTEWATER FACILITIES (11.13) ............................................................ 2
5 PROJECT DESCRIPTION (11.14) ....................................................................................................... 6
6 DRAWINGS (11.15) .............................................................................................................................. 6
7 DESIGN CRITERIA (11.16) .................................................................................................................. 6
8 SITE INFORMATION (11.17) ............................................................................................................... 6
9 ALTERNATIVE SELECTION/ANALYSIS (11.18) ................................................................................ 6
10 ENVIRONMENTAL IMPACTS (11.19) ............................................................................................. 6
APPENDICES
Appendix A Location Map
Appendix B Existing Bridger Peak Subdivision Flows
Prepared by:
Morrison-Maierle, Inc.
2880 Technology Blvd. W.
Bozeman, Montana 59771
Phone: (406) 587-0721
Fax: (406) 922-6702
Written By: CMS Checked By: JRN
Approved By: MEE
PROJECT NO.: 3959.022
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Bozeman East Mixed-Use
Sewer Distribution Design Report
1 EXECUTIVE SUMMARY
This design report provides a basis of design for the Bozeman East Mixed-Use development
sewer main extension improvements project and is submitted in conjunction with the completed
plans and specifications. The sewer distribution system serving the Bozeman East
development will be designed and installed in accordance with the Montana Department of
Environmental Quality (MDEQ) Circular No. 2; Montana Public Works Standard Specifications
(MPWSS); The City of Bozeman Modifications to MPWSS; and the City of Bozeman
Wastewater Facility Plan.
The design report is to verify that there is an adequate capacity to receive wastewater flows
from the Bozeman East development. An analysis of the capacity of the 8” line in Tschache as
well as further downstream in Simmental Way will be provided. The following design report
follows the section numbering of the Circular DEQ-2 Standards for Public Sewage Systems,
June 3, 2016.
2 PROBLEM DEFINED (DEQ 11.11)
a. The Bozeman East Mixed-Used Development is located off Tschache Lane on Lot 5 of
the Bridger Peaks Village Subdivision. The development is bounded by Tschache Lane
to the north, vacant lot and North 15th Ave to the east, and existing development to the
south and west. This project is located within the City of Bozeman, Montana. See the
vicinity map for location details.
Farran Realty Partners LLC has planned to construct (4) apartment buildings, a
clubhouse, commercial retail space, and outdoor recreation space as a part of this
project. This project involves extending approximately 737 feet of a new 8-inch sewer
main extension and 5 sewer manholes to serve the proposed development.
Sewer facilities included in this project will be designed in accordance with Montana
Department of Environmental Quality (MDEQ) regulations. Flow and population data for
the project will be consistent with the City’s approved Facilities Plan, where applicable.
3 DESIGN CONDITIONS (DEQ 11.12)
The proposed development includes four buildings with 305 dwelling units and 18,158 SF of
commercial retail space in the B-2 zoning district. The capacity requirement for the sewer main
extension is calculated as follows:
Tschache Lane Apartments East Flows:
Residential
305 each apartment units (buildings A, B, C , and D) proposed x 2.17 people per
dwelling unit (COB Design Standards V-B4) = 661.85 people
2
661.85 people x 64.4 gallons per capita day (COB Design Standards V-B4)
= 42,623 gallons per day (gpd) = Wastewater Flow Rate
Clubhouse
Assume (4) employees work out of the clubhouse
Assume half of the total population use the clubhouse on a given day = 661.85/2
= 331 people
Average Daily Flow = (4 employees)(13 gpd) + (331 users/day)(3 gpd) = 1,045 gpd
Commercial
12,079 sf and 6,079 sf of ground floor retail space in Buildings A and D respectively
A mixture of 11 spaces, with 36 employees, 388 customers
Average Daily Flow = (36 employees)(13 gpd) + (388 customers)(3 gpd) = 1,632 gpd
Infiltration
11.85 acres x 150 gallons/acre/day (COB Design Standards V-B4) = 1,777.5 gallons/day
Total Average Flow
Total Average Flow = 42,623 gpd +1,045 gpd +1,632 gpd +1,777.5 gpd
= 47,077.5 gpd
= 32.7 gpm
Total Peak flow
Population = Total Flow/64.4gpdc = 47,077.5 gpd/64.4gpdc = 731 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 3.88
Peak Flow = 47,077.5 gpd (avg daily flow) x 3.88 = 182,661 gpd = 127 gpm
For comparison, the maximum flow in an 8-inch pipe at minimum grade (0.4%), with a
roughness coefficient (n) value of 0.013 can be calculated as 498,240 gallons per day (346
gallons per minute). Thus, an 8-inch pipe size is adequate for all sewer mains included within
this development.
4 IMPACT ON EXISTING WASTEWATER FACILITIES (11.13)
Impact on Downstream Flows – 8” Sewer along Tschache
The City of Bozeman has required the examination of the capacity of the existing 8-inch sewer
main on Tschache Lane (east of 19th Street). The existing Bridger Peaks Subdivision is
currently the only contributor to the 8-inch sewer main on Tschache Lane east of 19th street.
The Bridger Peaks Subdivision includes both residential and commercial development. In this
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subdivision, the flows aggregate into an 8-inch onsite sewer main which flows north into the 8-
inch sewer main along Tschache Lane.
The following is an analysis of the existing flows from Bridger Peaks Subdivision to the 8-inch
sewer on Tschache Lane and the effect of the proposed Bozeman East development on that
sewer capacity. Per DEQ 2- 11.242-a which allows actual water use data to estimate flows,
Morrison Maierle contacted the Utility Billing Clerk at the COB and requested the actual billed
usage (please see Appendix A). The COB provided over three years of monthly billing data.
The following calculations utilize actual usage data provided by the COB.
Existing Residential
Data:
112 each apartment units (Bridger Peaks Subdivision Lots 1, 2, and 3)
Average gallons per day (using 3 years of data) = 6,320 gpd
Lot 1, 2, 3 = 4.15 acres
2.11 people per dwelling unit (COB Design Standards V-B4) = 237 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.12
Peak Flow = 6,320 gpd (avg daily flow) x 4.12 = 26,039 gpd
Peak Flow = 26,039 gpd = 18.09 gpm
Existing Commercial
Data:
Lot area = 17.17 acres (Bridger Peaks Subdivision Lots 1A-2, 1A-1, 2A-1, 5A, 8, 11, and
parcel 2B3)
Average gallons per day (using 3 years of data) = 10,461 gpd
Utilizing the existing residential population data, a proportional population for the
commercial development = (10,461 gpd/6,320 gpd)(commercial population/237 people)
= 392 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.03
Peak Flow = 10,461 gpd (avg daily flow) x 4.03 = 42,158 gpd
Peak Flow = 42,158 gpd = 29.28 gpm
Existing Infiltration
Assumptions:
21.39 acres x 150 gallons/acre/day (COB Design Standards V-B4) = 3,208.5 gallons/day
3,208.5 gpd = 2.23 gpm
Total Existing Peak Flow = 18.09 gpm + 29.28 gpm + 2.23 gpm = 49.6 gpm
The total proposed peak flow from the Bozeman East development (127 gpm) and the existing
development (49.6 gpm) is 176.6 gpm. This flow would enter the existing 8-inch sewer main on
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Tschache Lane and then flow west to the 24-inch sewer main on North 19th Avenue. For
comparison, the maximum flow in an 8-inch pipe at minimum grade (0.4%), with a roughness
coefficient (n) value of 0.013 can be calculated as 498,240 gallons per day (346 gallons per
minute). As a conservative estimate, the 8-inch Tschache Lane sewer main is assumed to be
installed at minimum grade.
Given the combined flow from the Bridger Peaks Subdivision and the Bozeman East
development, the existing 8-inch sewer main on Tschache Lane would, at peak flow, be at
approximately 51% capacity.
Impact on Downstream Flows at Simmental Way
2018 Flow Monitoring – Manhole 10107 – Simmental Way
Wastewater flow monitoring and a capacity analysis was required by the City of Bozeman to
determine if there existed potential sewer line capacity issues further downstream of the project.
The City of Bozeman provided equipment and staff to set up a Flow Meter in Manhole 10107.
The meter was set on October 5, 2018 and data was collected through November 29, 2018. The
following summarizes flow and depth readings through this period.
Parameter Average
Reading
High Reading
(1)
Low Reading
(2)
Average Daily
High Reading
Flow (gpm) 1359 2203 447 1985
Depth (inch) 6.33 8.83 3.68 8.07
The flow data (gpm) is presented graphically in Figure 1. Data was collected at 1-minute
intervals and the graph presents the data with this averaged to 15 minute time periods.
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Figure 1 Simmental Way Flow Data Manhole 10107
Figure 2 below shows flow during a typical weekday. Flows begin rising at about 5:00 AM, peak
around 9:00 AM, taper off between from 9:00 AM to 5:00 PM, start rising from 5:00 PM to 9:00
PM and tapering off again between 9:00 PM to 5 AM.
Figure 2 - Flow from November 6, 2018
Total Peak flow through Simmental Manhole 10107
Average Existing Peak Flow = 1,985 gpm
Bozeman East Proposed Peak Flow = 121.23 gpm
Total Peak Flow = 1,985 gpm + 121.23 gpm = 2,106.23 gpm
The Simmental manhole is connected to 24-inch concrete sewer line. The maximum flow in a
24-inch pipe at its existing slope of 0.95%, with a roughness coefficient (n) value of 0.013 is
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calculated to be 14,244,824 gallons per day (9,892 gallons per minute). Given the combined
flow from the Bozeman East development and the existing monitored flows in Simmental, the
24-inch sewer main on Simmental, at peak flow, would be at approximately 21% capacity.
The City’s current standard states that a 75% depth capacity be utilized for new construction,
therefore the existing system has the capacity for the addition flows from the Bozeman East
development.
5 PROJECT DESCRIPTION (11.14)
The sewer main extension for the Bozeman East development will include the construction of
approximately 737 feet of 8-inch SDR 35 PVC sanitary sewer main and (5) 48” diameter
manholes to serve the proposed development. The average sewer depth is approximately 5-
feet.
6 DRAWINGS (11.15)
Drawings identifying the site of the project, including the location and alignment of proposed
facilities are included in this submittal.
7 DESIGN CRITERIA (11.16)
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.
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. 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.
8 SITE INFORMATION (11.17)
The project site has been zoned B-2 by the City of Bozeman. The development is bounded by
Tschache Lane to the north, vacant lot and North 15th Ave to the east, and existing Bridger
Peaks Subdivision to the south and west. The proposed Bozeman East Mixed-Use complex is
currently undeveloped agricultural land which slopes gently to the north and east with existing
grades of less than 4% and mostly Blackdog silt loam soil deposits (USDA, Natural Resources
Conservation Service, Web Soil Survey)
9 ALTERNATIVE SELECTION/ANALYSIS (11.18)
No proposed alternatives were considered
10 ENVIRONMENTAL IMPACTS (11.19)
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.
Appendix A
11THSAVE19THNAVEDURSTON RD
W COLLEGE ST
MAIN STW 191
INTERSTATE
90
PROJECT
LOCATION
W GARFIELD ST
OAK ST
TSCHACHE ST
engineerssurveyorsplannersscientists
2880 Technology Boulevard West
Bozeman, MT 59718
Phone: (406) 587-0721
Fax: (406) 922-6702
VICINITY MAP
SCALE:1" = 3000'
Appendix B
Appendix BSUBDIVISION LOT NAME ADDRESSTotal Flow Collected (35 months of data)Average volume per month (hcf)Average volume per month (gallons)Average volume per year (gallons)Average Flow Rate (gpd)Average Flow Rate (gpm)Bridger Peaks Village 1 Bridger Peaks Village1483 N 15th Ave, Bozeman, MT 597154761.15 136.03 101759.6509 1221115.81 3345.522768 2.3232797Bridger Peaks Village 2 Summer Wood Apartments1441 N 15th Ave, Bozeman, MT 597152697.86 77.08 57661.13053 691933.5664 1895.708401 1.316464167Bridger Peaks Village 3 Spring Run Apartments 1325 N 15th Ave, Bozeman, MT 59715 1534.1662 43.83 32789.60269 393475.2323 1078.014335 0.748621066Bridger Peaks Village 1A-1 Club Pilates 1707 W Oak St, Suite C97 2.77 2073.172686 24878.07223 68.159102 0.04733271Bridger Peaks Village 1A-1 Office Retail 1707 W Oak St, Suite B0 0.00 0 0 0 0Bridger Peaks Village 1A-1 Office Retail 1707 W Oak St, Suite A0 0.00 0 0 0 0Bridger Peaks Village 2A-1 Papa Murphy's 1735 W Oak St, Suite A & B 2412.8 68.94 51568.56759 618822.8111 1695.404962 1.177364557Bridger Peaks Village 2A-1 Off the Cuff Dry Cleaners 1735 W Oak St C0 0.00 0 0 0 0Bridger Peaks Village 2A-1 Mia Bella Salon 1735 W Oak St E0 0.00 0 0 0 0Bridger Peaks Village 2A-1 ilovekickboxing.com 1735 W Oak St. Suite G0 0.00 0 0 0 0Bridger Peaks Village 2A-1 Gadget Fix 1735 W Oak St. F0 0.00 0 0 0 0Bridger Peaks Village 2A-1 Mongolian BBQ 1735 W Oak St.0 0.00 0 0 0 0Bridger Peaks Village 5A Smith's 1400 N 19th Ave5882.9 189.77 141958.552 1703502.624 4667.130475 3.24106283Bridger Peaks Village 8 AAA 1530 N 19th Ave Suite B2100 60.00 44883.12 538597.44 1475.609425 1.024728767Bridger Peaks Village 8 Verizon 1500 N 19th Ave0 0.00 0 0 0 0Bridger Peaks Village 8 White Black House Market 1620 N 19th Ave0 0.00 0 0 0 0Bridger Peaks Village 8 Garden of beadin 1500 N 19th Suite E1994.5 56.99 42628.27754 511539.3305 1401.477618 0.973248346Bridger Peaks Village 8 Jimmy Johns 1500 N 19th Ave0 0.00 0 0 0 0Bridger Peaks Village 8 Sports Clips1500 N 19th Ave G, Bozeman, MT 597180 0.00 0 0 0 0Bridger Peaks Village 8 CryoMT 1500 N 19th Ave, Suite H0 0.00 0 0 0 0Bridger Peaks Village 8 Chico's 1500 N 19th Ave, Suites I-K0 0.00 0 0 0 0Bridger Peaks Village 11 Gap 1620 N 19th Ave44.5 1.27 951.0946857 11413.13623 31.26886638 0.021714491Bridger Peaks Village 11 Famous Footwear 1600 N 19th Ave1153.5 32.96 24653.65663 295843.8795 810.5311768 0.562868873Bridger Peaks Village 11 Sally Beauty Supply 1600 N 19th Ave0 0.00 0 0 0 0Bridger Peaks Village 11 Taco Del Mar 1600 N 19th Ave #F0 0.00 0 0 0 0Bridger Peaks Village 11 TJ Max 1540 N 19th Ave443.3 12.67 9474.612903 113695.3548 311.4941228 0.216315363Average Gal/Year gpd gpmTotal 6,124,817.26 16,780.32 11.65Residential (Lots 1-3) 2306524.61 6319.25 4.39Commercial 3818292.65 10461.08 7.26