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895 Technology Blvd Suite 203 Bozeman, MT 59718 (406) 586-0262
895 Technology Boulevard, Suite 203, Bozeman, MT 59718 | 406.586.0262
January 31st, 2025
City of Bozeman Planning Department
20 East Olive
Bozeman, MT 59715
RE: Blackwood Groves Water & Sewer Design Report Addendum
Dear Alicia:
We have prepared this addendum to the Blackwood Groves Water & Sewer Design Report to address the
comment provided on December 16th, 2024 relating to the Blackwood Groves Site Plan Resubmittal. The
comment is provided below:
“Please confirm this development is within what was allotted in the Blackwood Groves Subdivision Water
& Sewer Design Report.”
Our response to this comment is stated below:
This addendum to the Blackwood Groves Water & Sewer Design Report was created to outline the
discrepancies between the Blackwood Groves Subdivision Water and Sanitary Sewer Design Reports
completed in 2021 and the Water and Sewer Design Reports recently submitted for the residential
development on Block 1, Lot 1 and Block 13, Lot 1.
Water:
The C&H Water Design Report identifies the two lots in this development as “Demand Junction 1” and
classifies them as commercial REMU lots. The report references Table 3.8 in the City of Bozeman’s Water
Facility Plan Update (2017). Table 3.8 of this plan identifies the average day flow for community commercial
mixed-use land as 1,285 gal/acre/day. While the actual lot area for the development is 7.84 acres, the report
used a total lot area of 7.7 acres which resulted in a calculated average daily flow of 9,985 gpd, or 6.9 gpm.
This table identifies the average day flow for a REMU zoned lot as 805 gal/acre/day. Using this value with a
total lot area of 7.7 acres, the average daily flow for the project comes out to 6,199 gpd, or 4.3 gpm. Following
the methods used by C&H, the proposed daily water usage for the residential development at Blackwood
Groves would fall well under what was allotted in the Blackwood Groves Subdivision Water & Sewer Design
Report completed by C&H.
In our daily water usage analysis, we used values found in the City of Bozeman Standards and Specifications
Policy, Addendum 7 (2020). These standards call for a proposed average daily water usage of 170-gallons
per day per person for residential development, with an average of 2.11 residents per dwelling unit. Using
these calculations, with 216 units proposed for the project, we determined the average daily flow to be 77,479
gpd, or 53.8 gpm. This value is greater than the demand allotted in the Blackwood Groves Subdivision Water
Design Report, however this is a much more accurate estimate for the daily water demand of the proposed
subdivision.
Project: Blackwood Groves
Page 2 of 2
895 Technology Blvd Suite 203 Bozeman, MT 59718 (406) 586-0262
Sewer:
The C&H Blackwood Groves Subdivision Sanitary Sewer Design Report identifies the two lots in this
development as “Phase 9” and classifies them as commercial lots. The report references Table V-1 from the
City of Bozeman Design Standards and Specifications (2020). Table V-1 identifies a wastewater flow rate of
3,000 gal/acre/day for the zoning designation B-3. The original subdivision report used this flow rate along
a lot area of 7.73 acres which resulted in a calculated average flow rate of 23,190 gpd. Table V-2 from the
City of Bozeman Design Standards and Specifications identifies a wastewater flow rate of 1,030 gal/acre/day
for residential land use. Using this value with a total lot area of 7.73 acres, the average flow rate for the
project calculates to 7,962 gpd. Following the methods used by C&H, the daily sanitary sewer demand for
the proposed residential development at Blackwood Groves would fall well under what was allotted in the
Blackwood Groves Subdivision Sanitary Sewer Design Report.
In our daily wastewater flow analysis submitted with the Site Plan, we used values found in the City of
Bozeman 2015 Wastewater Facility Plan. These standards call for an average daily wastewater usage of 64.4
gallons per capita/day, with an average of 2.17 residents per dwelling unit. Using these calculations, with
216 units proposed for the project, we determined the average daily flow to be 30,186 gpd. This value is
greater than the demand allotted in the Blackwood Groves Subdivision Sanitary Sewer Design Report,
however this is a much more accurate estimate for the daily wastewater flow of the proposed residential
subdivision.
Attached is the Daily Water Usage Analysis and Wastewater Daily Flow Analysis submitted with the Site
Plan using the City of Bozeman Standards and Specifications Policy, Addendum 7 (2020) and 2015
Wastewater Facility Plan, as well as excel sheets using the methods from the Blackwood Groves
Subdivision Water & Sewer Reports by C&H for comparison. Also attached is a figure of the lots
referenced with this addendum. Given the inaccuracy of the land use and differing flow rates outlined in the
Blackwood Groves Subdivision Water & Sewer Design Reports completed by C&H, we believe our
updated water and sewer demands provide more accurate values for the proposed subdivision.
Sincerely,
WWC/Madison Engineering
Josh Wolfram
Associate Civil Engineer, E.I.
*Using method from Blackwood Groves Subdivision Water Design Report by C&H
Average Daily Flow (Residential)
Gal/acre/day 805
Lot Area (acres)7.7
Average Daily Flow 6,199 gpd
Peaking Factor Calculations
Peak Hour Water Usage
Average Daily Usage 6,199 gpd 9,985 gpd
Maximum Hour Usage 18,596 gpd 29955 gpd
Maximum Hour Usage 774.8 gph 1248.1 gph
Maximum Hour Usage 12.9 gpm 20.8 gpm
Minimum Fire Flow Usage 1500.0 gpm 1500 gpm
Total Max. Hour Usage 1512.9 gpm 1520.8 gpm
REMU Commercial Mixed Use
Daily Water Usage Analysis
Blackwood Groves
Block 1, Lot 1 & Block 13, Lot 1
(*Value from Table 3.8 of the City of
Bozeman's Water Facility Plan
(*Value used in original report)
*Peaking factors of 1, 2.3, and 3.0 used in original subdivision report.
(*Values from original report)
Residential Flow:*Using method from Blackwood Groves Subdivision Sanitary Sewer Design Report by C&H
Average Daily Flow
Gal/acre/day 1030
Lot Area 7.73
Average Daily Flow 7,962 gpd
Peaking Factor Calculations
I & I Calculations
I & I
(gal/ac/day
Total. I & I
(gal/hr)
150 68.58
Peak Hour Sewer Demand
Commercial
Average Daily Flow 7,962 gpd 23,190 gpd
331.7 gph 966.3 gph
5.5 gpm 16.1 gpm
Peaking Factor 4.50 4.5
Peak Hour Sewer Demand 1561.4 gph 4422 gph
26.0 gpm 73.7 gpm
208.75 cfh 591.2 cfh
3.48 cfm 9.85 cfm
0.058 cfs 0.164 cfs
0.058 cfs 0.164 cfs
Wastewater Daily Flow Analysis
Blackwood Groves
Block 1, Lot 1 & Block 13, Lot 1
Area
(Ac)Total I & I (gal/day)
Total Peak Hour Demand:
Residential
7.73 1646.00
(*Value from Table V-2 in City of Bozeman Design
(*Value used in original report)
*Peaking factor of 4.5 used in original subdivision report.
(*Values from original report)
(*Values from original report)
Page 1 of 1
Water & Sewer Design Report Addendum Narrative
Blackwood Groves
February 2nd, 2025
Introduction
This narrative has been prepared to accompany the Blackwood Groves Water & Sewer Design
Report Addendum by request of the City of Bozeman Engineering Department. Included in this
narrative is information on connection points of the proposed infrastructure to the existing
conveyance system, as well as pipe sizing. Please reference the Blackwood Groves Water and
Sewer Design Reports for additional details.
Proposed Water and Wastewater Systems
The proposed water main extensions will consist of approximately 1,244 linear feet of 8” ductile
iron pipe and will be looped into the existing City of Bozeman water distribution system. The
four connection locations are two existing stubs on Canter Avenue, an existing stub on Victoria
Street, and a hot tap of the main on Victoria Street. These connections create two water main
loops to serve the north and south lots.
The proposed wastewater collection system will consist of approximately 1,088 linear feet of
new 8” PVC sewer main. Effluent generated will ultimately flow north and east into existing
manholes located on Canter Avenue, and then into an existing 10” PVC sewer main.
Please reference the attached site overview showing the existing and proposed infrastructure as
well as the vicinity map showing the referenced lots.
GIS Hydrant #Available Flow (gpm)Residual Pressure (psi)2680048.5520048.2240047.6860046.9580046.031,000.0044.941,200.0043.681,400.0042.271,600.0040.71,800.0038.972,000.0037.12,200.0035.12,400.0032.952,600.0030.652,800.0028.23,000.0025.63,200.0022.843,400.0019.953,600.0016.913,800.0013.724,000.0010.44,200.006.944,400.003.33Hydrant Curve 01020304050600 500 1000 1500 2000 2500 3000 3500 4000 4500 5000Residual Pressure (psi)Available Flow (gpm)Hydrant Curve 2680Data Disclaimer: Water distribution information is calculated using hydraulic modeling software and is subject to variation. Actual field conditions may vary. This information is provided to the requestor for evaluation purposes only, without warranty of any kind, including, but not limited to any expressed or implied warranty arising by contract, stature, or law. In no event regardless of cause, shall the City be liable for any direct, indirect, special, punitive or consequential damages of any kind whether suchdamages arise under contract, tort, strict liability or inequity.
K:\Bozeman\Fourth Avenue Capital\2023531 Blackwood Grove Blk 1 & 13 Site Plan\05CAD\Sheets\Exhibit\Water & Sewer Report Addendum Exhibit.dwg Utility Plan 2/3/2025 1:26:31 PM
PREPARED BY
VICINITY MAP
FAC BLACKWOOD, LLC
BOZEMAN, MT
BLACKWOOD GROVES ENGINEERING
895 TECHNOLOGY BLVD., SUITE 203
BOZEMAN, MT 59718
(406) 624-3910
www.wwcengineering.com
N 19TH AVE
CANTER AVE VICTORIA STBLACKWOOD RDWINTERTHUR AVE SCOTCH PINE LNCAMBRIDGE DRBLACKWOOD GROVESUB PH 1 & 9, S24, T02 S,R05 E, BLOCK 1, LOT 1,ACRES 4.85BLACKWOOD GROVESUB PH 1 & 9, S24, T02 S,R05 E, BLOCK 13, LOT 1,ACRES 2.998PROJECT BOUNDARYPROJECT BOUNDARYN.T.S.VICINITY MAPN.T.S.