HomeMy WebLinkAbout008 - Appendix G - Water Sewer Storm Design Report
MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
406.586.0277
tdhengineering.com
234 East Babcock Street
Suite 3
Bozeman, MT 59715
March 11, 2026
re: BOUTIQUE HOTEL MENDENHALL
7-STORY SITE PLAN MODIFICATION
WATER & SEWER DEMAND UPDATES
The purpose of this letter is to provide updated water and sewer demand estimates for the
Boutique Hotel Mendehall project as part of a proposed Modification to add a 7 th floor and
increase the occupancy from 71 to 91 rooms.
The original domestic water and sewer demands for the 71-room hotel were estimated
using actual water meter data from four comparable hotel facilities within the City of
Bozeman. Based on this data, a conservative estimate of 80 Gal/Day/Room was assumed
for a modern hotel building inclusive of restaurant & bar amenities. The previous 71 -room
domestic water and sewer demand estimates are provided below for reference as
presented in the engineering design report for CCOA/SP 24147:
Table 1:
Previous Estimated Water Demands – 71 Room Hotel
Average Day Max. Day Peak Hour
New Building
Demand 5,680 gpd 9.1 gpm 11.8 gpm
Table 2:
Previous Estimated Sewer Demands – 71 Room Hotel
Average Day (gpd) Peak Hour (gpm)
New Building Demand 5,680 -
Lot Infiltration 62 -
Total Sewer Demand 5,742 16.84
Updated domestic water and sewer demand estimates for the proposed 7-story 91-room
are summarized in the following tables with supporting calculations attached. These
estimates also assume 80 Gal/Day/Room based on the same Downtown Bozeman hotel
water meter data that was presented with the original site plan application.
March 11, 2026 PAGE NO. 2
tdhengineering.com
Table 3:
Updated Estimated Water Demands – 91 Room Hotel
Average Day Max. Day Peak Hour
New Building
Demand 7,280 gpd 11.6 gpm 15.2 gpm
Table 4:
Updated Estimated Sewer Demands – 91 Room Hotel
Average Day (gpd) Peak Hour (gpm)
New Building Demand 7,280 -
Lot Infiltration 62 -
Total Sewer Demand 7,342 21.4
Water System Capacity:
New domestic water and fire service lines for the hotel will be connected to the existing 8”
ductile iron water main in E. Mendenhall Street. The fire flow requirement for the new
building is 1,000 gpm based on building size and construction type as determined following
International Fire Code Appendix B criteria, and the max day + fire flow demand for the 91-
room hotel = 1,012 gpm. Fire hydrant flow data indicates 12,000 to 13,200 gpm will be
available in the adjacent water main before dropping below a residual pressure of 20 psi.
Therefore, adequate capacity is expected to be available in the City’s water system to
support the proposed increase to 91 hotel rooms.
Sewer System Capacity:
The existing 6” clay sewer main in E. Mendenhall Street is being replaced and upsized with
8” PVC as required by the previous site plan application. The updated peak hour domestic
sewer demand for the hotel is 21.4 gpm and the minimum carrying capacity of an 8” sewer
flowing at 75% full at minimum 0.4% slope is 313.6 gpm. Therefore, adequate capacity is
expected to be available in the upgraded sewer main to support the proposed increase to
91 hotel rooms.
Please let me know if you have any questions or require additional information.
Sincerely,
Cody Croskey PE
Civil Engineer
TD&H ENGINEERING
I:\2024\BOZ\B24-005 BHM Mendenhall\05_DESIGN\DESIGN REPORT\7-STORY MOD UPDATE\PARTS\BHM - 7 STORY MOD W&S
DEMAND LTR.DOC
Comparable Hotel Water & Sewer Demand Analysis
(Data through April 2023)
Summary
Notes:
1. Downtown Bozeman Hotels were used as a comparison because they were recently constructed, have high occupancy rates
and exhibit similar uses as the proposed Boutique Hotel Mendenhall.
2. Because irrigation is minimal Downtown, average day sewer demands are assumed to be
approximately equal to average day water demands.
Hotel
ADF
Consumption
(Hundred Cubic
Feet)
ADF
Consumption
(Gallons)
ADF
Consumption
(Hundred Cubic
Feet)
ADF
Consumption
(Gallons)
ADF
Consumption
(Hundred Cubic
Feet)
ADF
Consumption
(Gallons)
ADF
Consumption
(Hundred Cubic
Feet)
ADF
Consumption
(Gallons)
Armory 4.22 3,155.27 11.94 8,929.52 12.48 9,333.03 12.49 9,340.78
Element 7.93 5,928.34 9.72 7,269.99 9.05 6,767.43 8.72 6,522.70
Residence Inn ND ND 7.10 5,310.10 11.03 8,250.19 10.62 7,944.42
AC Marriott ND ND ND ND 9.47 7,081.12 11.53 8,628.03
Hotel Year with Largest
ADF
ADF
Consumption
(Gallons)
# Rooms ADF per Room
(Gallons)
Armory Last 12 Months 9,340.78 122 76.56
Element 2021 7,269.99 104 69.90
Residence Inn 2022 8,250.19 104 79.33
AC Marriott Last 12 Months 8,628.03 143 60.34
Use: 80 Gal./Day/Room
Avg. Day Flow (ADF)
Last 12 Months
Summary of Average Day Water Meter Consumption for Downtown Bozeman Hotels
Summary of Per Room Average Day Consumption for Downtown
Bozeman Hotels
Avg. Day Flow (ADF)
2020
Avg. Day Flow (ADF)
2021
Avg. Day Flow (ADF)
2022
1 OF 8
Boutique Hotel Mendenhall
302 E. Mendenhall Street
Date: 03.11.26
Water Demand Calculation - 91 Room MOD
Domestic Water Demand:
Hotel Use:
Rooms =91
Average Demand per Room =80.0 Gal./Day/Room (See Comparable Facility Data)
Average Day Demand =7,280 GPD
Peak Hour Demand:
Average Day Demand =7,280 GPD
Average Day Demand =5.1 gpm (GPD / 1,440 minutes)
Maximum Day Demand =11.6 gpm (Ave. Day x Peaking Factor = 2.3)
Peak Hour Demand =15.2 gpm (Ave. Day x Peaking Factor = 3)
Fire Flow Requirement - New Building:
IBC Construction Type =1B
Fire Flow Calculation Area =67,107 GSF
Fire Flow Requirement =2,750 GPM (per IFC Table B105.1(2) for total building area)
Automatic Fire Sprinkler System =Yes
Fire Sprinkler System Type =NFPA 13
Reduced Fire Flow Requirement =1,000 gpm (25% of Total/1,000 GPM min. per IFC Table B105.2)
CITY OF BOZEMAN
Fire Flow Request Form
PHONE (406) 582-3200 FAX (406) 582-3201
Date March 27, 2024
Location 302 E Mendenhall (FFR-5896)
Pressure Zone HGL 5125 (S)
GIS Hydrant ID# 72 and 74
Adjacent Main Size 8-inch DI
Model Scenario Maximum Day Demand, Steady State, Fire Flow
Reference 2017 Water Facility Plan Update1
Hydrant Curves An Excel Spreadsheet with hydrant curves has been provided for the
requested location
Requested Location via the Bozeman Infrastructure Viewer2
If you have questions or need further information feel free to email.
Data 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 such damages arise under contract, tort, strict liability or
inequity.
HOME OF MONTANA STATE UNIVERSITY
GATEWAY TO YELLOWSTONE PARK
1 https://www.bozeman.net/home/showpublisheddocument/4977/636420174896170000
2 https://gisweb.bozeman.net/Html5Viewer/?viewer=infrastructure
GIS Hydrant #
Available Flow
(gpm)
Residual
Pressure (psi)72
0 131.35
200 131.04
400 130.69
600 130.29
800 129.83
1,000.00 129.33
1,200.00 128.79
1,400.00 128.2
1,600.00 127.57
1,800.00 126.89
2,000.00 126.18
2,200.00 125.43
2,400.00 124.63
2,600.00 123.79
2,800.00 122.92
3,000.00 122
3,200.00 121.04
3,400.00 120.05
3,600.00 119.01
3,800.00 117.93
4,000.00 116.8
4,200.00 115.64
4,400.00 114.44
4,600.00 113.2
4,800.00 111.92
5,000.00 110.6
5,200.00 109.25
5,400.00 107.86
5,600.00 106.42
5,800.00 104.91
6,000.00 103.35
6,200.00 101.75
6,400.00 100.13
6,600.00 98.46
6,800.00 96.75
7,000.00 94.99
7,200.00 93.2
7,400.00 91.37
7,600.00 89.5
7,800.00 87.6
8,000.00 85.65
8,200.00 83.66
8,400.00 81.64
8,600.00 79.58
8,800.00 77.49
9,000.00 75.34
9,200.00 73.17
9,400.00 70.95
9,600.00 68.7
9,800.00 66.41
10,000.00 64.08
10,200.00 61.71
10,400.00 59.31
10,600.00 56.87
10,800.00 54.39
11,000.00 51.88
11,200.00 49.33
11,400.00 46.75
11,600.00 44.12
11,800.00 41.46
12,000.00 38.77
12,200.00 36.04
12,400.00 33.23
12,600.00 30.43
12,800.00 27.61
13,000.00 24.72
13,200.00 21.66
13,400.00 19.02
13,600.00 16.34
13,800.00 13.63
14,000.00 10.89
14,200.00 8.13
14,400.00 5.34
14,600.00 2.53
Hydrant Curve
0
20
40
60
80
100
120
140
0 2000 4000 6000 8000 10000 12000 14000 16000Residual Pressure (psi)Available Flow (gpm)
Hydrant Curve
72
Data 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
such damages arise under contract, tort, strict liability or inequity.
GIS Hydrant #
Available Flow
(gpm)
Residual
Pressure (psi)74
0 129.57
200 129.26
400 128.89
600 128.45
800 127.96
1,000.00 127.4
1,200.00 126.79
1,400.00 126.13
1,600.00 125.41
1,800.00 124.64
2,000.00 123.82
2,200.00 122.94
2,400.00 122.02
2,600.00 121.05
2,800.00 120.03
3,000.00 118.96
3,200.00 117.84
3,400.00 116.67
3,600.00 115.45
3,800.00 114.18
4,000.00 112.85
4,200.00 111.48
4,400.00 110.07
4,600.00 108.6
4,800.00 107.08
5,000.00 105.52
5,200.00 103.92
5,400.00 102.27
5,600.00 100.57
5,800.00 98.81
6,000.00 96.98
6,200.00 95.1
6,400.00 93.18
6,600.00 91.22
6,800.00 89.2
7,000.00 87.14
7,200.00 85.02
7,400.00 82.87
7,600.00 80.67
7,800.00 78.41
8,000.00 76.12
8,200.00 73.77
8,400.00 71.38
8,600.00 68.95
8,800.00 66.47
9,000.00 63.94
9,200.00 61.38
9,400.00 58.76
9,600.00 56.1
9,800.00 53.39
10,000.00 50.64
10,200.00 47.8
10,400.00 45
10,600.00 42.11
10,800.00 39.18
11,000.00 36.21
11,200.00 33.19
11,400.00 30.13
11,600.00 27.02
11,800.00 23.88
12,000.00 20.68
12,200.00 17.45
12,400.00 14.14
12,600.00 10.81
12,800.00 7.45
13,000.00 4.05
13,200.00 0.61
Hydrant Curve
0
20
40
60
80
100
120
140
0 2000 4000 6000 8000 10000 12000 14000Residual Pressure (psi)Available Flow (gpm)
Hydrant Curve
74
Data 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
such damages arise under contract, tort, strict liability or inequity.
Boutique Hotel Mendenhall
302 E. Mendenhall Street
Date: 03.11.26
Sewer Demand Calculation - 91 Room MOD
Average Day Sewer Demand :
Hotel Use:
Rooms =91
Average Demand per Room =80.0 Gal./Day/Room (See Comparable Facility Data)
Average Day Demand =7,280 GPD
Infiltration:
Property Size =0.41 acres
Infiltration Flow =62 GPD (150 gpd/acre per COB Design Standards)
Total Development Average Day Demand:
7,342 GPD (domestic + infiltration)
Total Development Peak Sewer Flow:
Average Day Demand =7,280 GPD (domestic only)
Equivalent Population =113 People (GPD / 64.4gpcd - 2015 Wastewater Facilities Plan)
P =0.1130 (population/1,000)
Peaking Factor =4.23
Peak Sewer Demand =30,784 GPD (avg. day demand)*(peaking factor)
+ Infiltration Flow =62 GPD (not peaked)
Total Peak Flow =30,846 GPD (peaked domestic + infiltration)
Peak Sewer Flow =21.42 GPM (peak flow)/(24 hrs/day)/(60 min/hr)
𝑄𝑚𝑎𝑥
𝑄𝑎𝑣𝑔
=18 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠𝑛𝑑𝑛𝑑𝑛𝑛𝑙𝑑1/2
4 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠𝑛𝑑𝑛𝑑𝑛𝑛𝑙𝑑1/2
Boutique Hotel Mendenhall
Offsite Sewer Main Replacement
Date: 10.07.2025
8" Sewer Main Pipe Capacity
Input Values
d =0.67 ft =8"
y =0.500 ft =75%
Calculated Values (Equations from Fluid Mechanics by Chow)
Theta (Θ)4.19 rad 2*arccos(1-y/(d/2))
Area (A)0.28 ft2 (1/8)*(Θ-sinΘ)d2
Wetted Perimeter (P)1.40 ft 0.5Θd
Hydraulic Radius (R )0.20 ft (.25)*(1-(sinΘ)/Θ)d
Top Width (T)0.58 ft (sin 0.5Θ)d
Mannings Equation (Equation from Fundamentals of Mechanics by Munson)
n =0.013 (per COB Design Standards)
S0 =0.0040 ft/ft (0.4% Min. Slope)
Q =0.70 cfs Q = 1.49/n*A*R2/3*S00.5
Q =313.6 gpm Q gpm = (Q cfs)(7.48 gal/ft3)(60 sec/min)
V =2.49 ft/s V = Q/A
Results An 8" diameter sewer main flowing 75% full at a min. slope of 0.4%
has a carrying capacity of 313.6 gpm.
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