HomeMy WebLinkAbout023 WATER SYSTEM REPORTWATER SYSTEM REPORT
The Cottonwood Apartments – BLOCK 1, LOTS 1 & 2
The Cottonwood Apartments – Phase 2, Bozeman, Montana 59718
Block 1 – Lots 1 and 2, Cottonwood Subdivision (Site Plan Packages F & G)
Prepared For:
Roundhouse
Attn: Patrick Boel
Director of Development & Construction
1100 West Idaho Street, Ste 630
Boise, ID 83702
Prepared By:
Cushing Terrell
411 E. Main Street, Ste. 101
Bozeman, MT 59715
www.cushingterrell.com
Cushing Terrell Project No. Cottonwood_P2
December 18, 2024
Adam Schlegel, PE
Water System Report
The Cottonwood Apartments – Block 1, Lots 1 & 2 and Block 2, Lot 1
Project No.
Cottonwood_P2
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TABLE OF CONTENTS
1.0 INTRODUCTION ................................................................................................................................................. 2
1.1 Zoning ............................................................................................................................................................... 4
1.2 Existing Ground Cover and Vegetation ................................................................................................ 4
1.3 Topographic Features, and Slopes ......................................................................................................... 5
1.4 FEMA Floodplain Classification................................................................................................................ 5
1.5 Wetlands .......................................................................................................................................................... 5
1.6 Geologic Features and Geotechnical Data .......................................................................................... 5
2.0 WATER MAIN DESIGN ..................................................................................................................................... 5
2.1 Existing Water Supply ................................................................................................................................. 5
2.2 Proposed Water System ............................................................................................................................. 6
2.3 Capacity Analysis........................................................................................................................................... 6
2.4 Results ............................................................................................................................................................... 8
3.0 CONCLUSION ..................................................................................................................................................... 8
LIST OF FIGURES
FIGURE 1.1: Overall Location Map ............................................................................................................................ 3
Figure 1.2: Project Map ................................................................................................................................................. 4
LIST OF TABLES
TABLE 2.1: Water Main Extension Demands ......................................................................................................... 7
Table 2.2: Package E ....................................................................................................................................................... 7
APPENDICES
Appendix A: Geotechnical Report Excerpts
Appendix B: Cottonwood Subdivision Water Main Report Excerpts
Appendix C: Phase 1 Water Main Design Report
Appendix D: Calculations and Back-up Data
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1.0 INTRODUCTION
Roundhouse Development Group proposes a multifamily housing development on Lots 1 and 2
of Block 1 and Lot 1 of Block 2 of the Cottonwood Subdivision, Phase 2, generally located east
of Cottonwood Road and south of Huffine Lane. The housing development will utilize the
previously approved and installed public water and sewer utilities (EQ#20-1840). Additionally,
the housing development will utilize the existing subdivision stormwater detention facilities and
connect to the existing stormwater infrastructure in Stafford Avenue and along the north side of
the property boundary. The development has been separated into three different site plan
packages (E, F, and G). Site plan package E covers Lots 1, Block 2. Package F covers Lot 1, Block
1. Package G covers Lot 2, Block 1. The following figure shows the boundaries of the different
site plan packages and project location.
The intent and purpose of this report is to request a public water main extension to service
Buildings #19 - #23 within Block 1 (Packages F and G) as it is not practical to service the
buildings from the adjacent streets with traditional services. Additionally, the report will provide
an update to the overall water demands for the subdivision to account for the actual proposed
development. See Appendix C for project map.
It is important to note that buildings 15 and 18 within Package E will be served by existing water
service stubs from Stafford Ave. Buildings 16 and 17 within Package E will not contain
water/wastewater facilities.
This report will reference the previously approved subdivision engineering reports prepared by
Madison Engineering titled “WATER MAIN DESIGN REPORT FOR: COTTONWOOD SUBDIVISION
BOZEMAN, MT” dated March 2020 and Prepared by Cushing Terrell titled “WATER SYSTEM
REPORT The Cottonwood Apartments -Block 3, Lots 1& 2 & Block 6 Lot 1” revised April 15,
2021. See Appendix B and C for original report excerpts.
The following references were used in the design of the water main extension.
• EQ# 20 -1840
• Water Main Design Report – For: Cottonwood Subdivision, Bozeman, MT. Prepared by:
Madison Engineering. Dated: March 2020. See Appendix B.
• Water System Report The Cottonwood Apartments – Block 3, Lots 1 & 2 & Block 6 Lot 1.”
Dated: December 23, 2020. See Appendix C
• COB Design Standards and Specifications Policy, 2004. Addendum #6 (DSSP)
• COB Modifications to Montana Public Works Standard Specifications (MPWSS),
Addendum #3
• City adopted MPWSS and Adopted Addenda
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• COB Wastewater Facility Plan, 2015
• WQB Circular No. 2
• City of Bozeman Zoning Map
FIGURE 1.1: Overall Location Map
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Figure 1.2: Project Map
1.1 Zoning
The subject properties are zoned R5: Residential Mixed-Use High Density District. This zoning
matches the zoning assumed in the original engineering report.
1.2 Existing Ground Cover and Vegetation
The subject properties are serviced by the existing subdivision streets and City utilities (water,
sewer, and storm). Internal lot areas are stripped of topsoil and have various stockpile locations
as a result of the construction of the offsite infrastructure and developments.
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1.3 Topographic Features, and Slopes
Blocks 1 & 2 slope from the east to the west towards S Cottonwood Rd. Significant topographic
features on site include stockpiles reaching heights of 15’ as a result of construction during phase
1 of this development. Stockpiles and excess dirt in these lots will be removed during the
construction of phase 2.
1.4 FEMA Floodplain Classification
Per FEMA FIRM Panel #30031C0811D, there are no FEMA determined floodplains on or near the
subject property.
1.5 Wetlands
Wetlands were previously located within the subdivision, but have since been mitigated as part
of the subdivision infrastructure work (Corps No. NWO-2017-02234-MTH, Type: NWP 29).
1.6 Geologic Features and Geotechnical Data
See Appendix A for the geotechnical investigation excerpts from the report prepared by Allied
Engineering Services, Inc. titled, “Cottonwood Subdivision Southeast Side of Huffine Ln/Cottonwood
Rd Bozeman MT” dated January 2019. The full report can be provided upon request.
1.6.1 Soils
Overall, the report indicates the soils in the area consist of topsoil in the upper ten inches,
underlain by eight inches of native silt/clay, underlain by approximately ten feet of a native
sandy gravel. Borehole logs and an excerpt on subsurface conditions are located in Appendix
A.
1.6.2 Groundwater
The report does indicate the presence of groundwater in the project area. The borehole logs
indicate varying levels throughout the site from 3.7’ to 5.1’ below the ground surface. See
Appendix A for excerpts.
2.0 WATER MAIN DESIGN
2.1 Existing Water Supply
Proposed water main extension #1 (Site Plan Package – F & G) will be connected between two
existing 8” stubs provided off of W Garfield Street and Stafford Avenue.
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2.2 Proposed Water System
The proposed public water main extension will provide additional branching to the recently
installed public water main network extensions for Cottonwood Subdivision. Water main
extension #1 will connect between to previously planned and now installed stubs in Block 1
Buildings #19 - #23.
The layout of the proposed public water main meets the City of Bozeman design criteria and will
be located within proposed 30’ wide easements. The public water main will be separated from
the proposed sanitary sewer main by a minimum distance of 10 feet. The layout of the
proposed public water main meets the COB design criteria. Fire hydrants will be installed so not
to exceed 600’ spacing, fulfilling the distance requirement for fire hydrant spacing, as well as
assisting in flushing of the main. Gate valves will be installed at the connection point to the
existing mains as well as on property lines, per City standards.
If any extensions are required in the future, that developer will be required to analyze and
submit a report to the City of Bozeman and the MDEQ for review (DEQ 1.1.2.c. and d., and
1.1.14).
2.3 Capacity Analysis
Refer to Section D of the original subdivision water main report for capacity analysis details
located in Appendix B. The original capacity analysis only assumed residential flows. The
following is a summary of the previously calculated flows, assuming 400 residential units.
• Average Day Demand (ADD): 103 GPM
• Maximum Day Demand (MDD): 237 GPM, (Peaking Factor = 2.3)
• Peak Hour Demand (PHD): 309 GPM, (Peaking Factor = 3)
The following table shows the estimated demands, Average Daily Demand (ADD), Peak Hour
Demand (PHD), and Maximum Daily Demand (MDD), for the phase 2 units that will be serviced
by this extension.
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TABLE 2.1: Water Main Extension Demands
Table 2.2: Package E
The required fire flow for the proposed Type V-A structures, while assuming 8,900 sf floor plans,
is 1,750 gpm without an automatic sprinkler system. With an automatic sprinkler system a 50%
flow reduction is allowed. For the purposes of this analysis and to provide a conservative
estimate a fire flow demand of 1,500 gpm has been assumed. With the fire flow demand of
1,500 gpm and the MDD demand of 49 gpm, the total required MDD demand plus fire flow is
1,549 gpm (3.45 cfs). A Hazen-Williams “C” Factor of 130 was used in the pipe evaluation. The
working residual water pressure shall not be less than 20 psi at any point in the water
distribution system under maximum day plus fire flow. The velocity shall not exceed 15 feet per
second through the main line.
CONTRIBUTING BUILDINGS # OF UNITS
DENSITY
(PERSONS
/UNIT)
POPULATION
(PERSONS)
AVG. DAILY
DEMAND
(GPD PER
PERSON)
ADD
(GPD)
ADD
(GPM)
1BUILDING #19 - TYPE C 24 2.17 52 170 8,854 6.15
1BUILDING #20 - TYPE A 12 2.17 26 170 4,427 3.07
1BUILDING #21 - TYPE C 24 2.17 52 170 8,854 6.15
1BUILDING #22 - TYPE A 12 2.17 26 170 4,427 3.07
1BUILDING #23 - TYPE C 24 2.17 52 170 8,854 6.15
96 208 TOTAL ADD =35,414 25
TOTAL MDD =81,453 49
TOTAL PHD =106,243 98
COTTONWOOD APARTMENTS | WATER USAGE - SITE PLAN PACKAGES F & G
1AVERAGE DAILY DEMAND IS BASED ON THE UNIT DEMAND OF 170 GAL./PERSON/DAY AND 2.17 PERSONS PER HOUSEHOLD OR 368.9 GPD PER UNIT.
CONTRIBUTING BUILDINGS # OF UNITS
DENSITY
(PERSONS
/UNIT)
POPULATION
(PERSONS)
AVG. DAILY
DEMAND
(GPD PER
PERSON)
ADD
(GPD)
ADD
(GPM)
1BUILDING #15 - TYPE C 24 2.17 52 170 8,854 6.15
1BUILDING #18 - TYPE A 12 2.17 26 170 4,427 3.07
36 78 TOTAL ADD =13,280 9
TOTAL MDD =30,545 18
TOTAL PHD =39,841 37
COTTONWOOD APARTMENTS | WATER USAGE - SITE PLAN PACKAGES F & G
1AVERAGE DAILY DEMAND IS BASED ON THE UNIT DEMAND OF 170 GAL./PERSON/DAY AND 2.17 PERSONS PER HOUSEHOLD OR 368.9 GPD PER UNIT.
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2.4 Results
Flow analysis of the 8-inch D.I. pipe with a C value of 130 can provide the required 1,549 gpm
during the MDD plus fire flow scenario for Phase 1. The maximum pipe velocity will not exceed
15 ft/s, as illustrated in the attached WaterCad Automated Fire Flow Analysis, during the MDD
plus fire flow scenario. Using the previously provided hydrant flow data, a three-point pump
curve was generated to simulate existing conditions within the City of Bozeman water system.
The residual pressure is typically used to model the low point on the pump curve. For this
simulation however, and similar to the previous subdivision analysis the pitot pressure was used
as the low point on the pump curve to ensure a conservative design (residual pressure = 100 psi,
pitot pressure = 84 psi). Pressures within the system never fall below 73 psi during the MDD plus
fire flow event, which exceeds the minimum required pressure of 20 psi. See Appendix D for
WaterCad analysis data.
It should be noted that current calculations in this report are approximated based on hydrant
test results and data from phase 1. Phase 2 of this subdivision will have additional hydrant tests
performed in the project area, providing more accurate data and calculations for this water main
extension.
3.0 CONCLUSION
The proposed public water main extensions have adequate capacity to provide the MDD plus
fire flow for the future developments. See Appendix D for calculations.
As previously mentioned, the original subdivision report assumed 400 units to be developed in
Cottonwood Subdivision. Buildings #19 - #23 equate to approximately 96 units. Package E will
contain 36 units and in phase one a total of 256 units were developed resulting in a total of 388
developed units. This proposed project does not exceed the previously approved 400 units.
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Appendix A: Geotechnical Report Excerpts
Cottonwood Subdivision
Huffine Lane / Cottonwood Road – Bozeman, MT
Project: 17-170
January 9, 2019
Allied Engineering Services, Inc. Page 6
Soil Conditions
The site can simply be characterized as being underlain by good, dense, clean sandy gravel beginning at
depths of 1.5 to 2.5 feet across the entire property. The gravels in this part of Bozeman are expected to
extend at least 100 feet deep and were confirmed to the 50-foot depth during the borehole drilling that
was conducted at the Bozeman Health Ambulatory Care Facility. The presence of the shallow gravel is
not surprising and has been pretty consistent in the other nearby areas we have recently investigated,
including the Town Pump site to the north, the Bozeman Health ACF to the northwest, and the
Cottonwood Road corridor to the north of Huffine Lane. Based on the eight test pits, the gravels have a
“clean” and sandy composition and are relatively small in size. Most of the gravel is a 3” to 4”-minus
material, but it does contain scattered cobbles up to 6 to 8 inches. The gravels were uniform through-
out the 10 to 11-foot test pit depths. See Figure 4 for the distribution of gravel depth across the site.
No random/foreign surface fill material was found in any of the test pits. All soils were native and in-
place. The site is blanketed by 9 to 12 inches of organic topsoil. Underlying the topsoil and overlying
the sandy gravel is a thin, intermediate layer of silt/clay. In most locations, the silt/clay was stiff to very
stiff and the lowermost 0.5-foot of the silt/clay contained some scattered small gravels (as the interface
with the alluvial sandy gravel was neared). Really, the only anomalies were found in TP-7, which was
located on the south side of the site. At this location, the same soil stratigraphy is present, but the
topsoil was more gravelly and the silt/clay was not only more gravelly, but very moist and much less
stiff. Provided in Table 3 is a summary of the soil conditions that were observed in the eight test pits.
The material descriptions and soil depths in the table match the data shown on the logs.
Table 3. Summary of Soil Conditions in Test Pits 1 - 8
TP # TP LOCATION NATIVE
TOPSOIL
NATIVE
SILT/CLAY
NATIVE
SANDY GRAVEL
1 N1/2 of Site, NW Corner 0.0’ - 1.0’ 1.0’ - 1.7’ 1.7’ - 10.0’
2 N1/2 of Site, NE Corner 0.0’ - 0.8’ 0.8’ - 2.0’ 2.0’ - 11.0’
3 N1/2 of Site, Center 0.0’ - 0.8’ 0.8’ - 1.8’ 1.8’ - 11.0’
4 Middle of Site, Center 0.0’ - 0.8’ 0.8’ - 1.5’ 1.5’ - 11.0’
5 Middle of Site, East Side 0.0’ - 0.8’ 0.8’ - 2.2’ 2.2’ - 11.0’
6 S1/2 of Site, SE Corner 0.0’ - 1.0’ 1.0’ - 2.3’ 2.3’ - 10.0’
7 S1/2 of Site, South Side 0.0’ - 1.0’ 1.0’ - 2.0’ 2.0’ - 10.0’
8 S1/2 of Site, West Side 0.0’ - 0.8’ 0.8’ - 2.2’ 2.2’ - 10.0’
Notes: 1) All soil measurements are depths below existing ground. 2) The native silt/clay is an unsuitable bearing material and shall be removed from under all footing locations.
3) The “target” bearing material for all foundation elements is the dense, native sandy gravel starting at 1.5’ to 2.5’.
4) Generally, the lower 0.5-foot of silt/clay (in all test pits) contained some scattered, small gravels. 5) In TP-7, the silt/clay was more gravelly, more moist, and less stiff (as compared to the other seven pits).
6) PVC monitoring wells were installed in TP-1 through TP-8 for future groundwater monitoring purposes.
Cottonwood Subdivision
Huffine Lane / Cottonwood Road – Bozeman, MT
Project: 17-170
January 9, 2019
Allied Engineering Services, Inc. Page 7
Provided below is a general description of the soil conditions encountered in the test pits. Following
each soil description is a statement regarding foundation bearing potential for the particular soil type.
• Native Topsoil: Generally consists of moist; medium stiff; black to dark brown; organic clayey
SILT with abundant roots.
The native topsoil is an unsuitable foundation bearing material that must be removed
from under all footings. In addition, all organic topsoil must be stripped/removed from
building footprints, utility trench locations, and under exterior slabs and asphalt areas.
• Native Silt/Clay: Generally consists of moist; stiff to very stiff; brown to orangish brown; sandy
SILT to sandy lean CLAY. The lower six inches (+/-) of silt/clay directly above the underlying
sandy gravel contains some scattered gravels. This transitional zone does not constitute clean
sandy gravel. In most pits, the silt/clay was on the dry side (due to relatively deep groundwater)
and consequently these soils were in a stiff to very stiff condition. Really the only exception was
in TP-7, which is located on the south side of the property and closest to the Farmers Canal. At
this location, the silt/clay was very moist and hence less stiff (ie. little softer than other areas).
The native silt/clay is an unsuitable foundation bearing material that must be removed
from under all footings.
• Native Sandy Gravel: Generally consists of slightly moist to wet; dense; brown; clean sandy
GRAVEL with abundant 3” to 4”-minus gravels and scattered 6” to 8”-minus cobbles. The on-site
gravel is a very good reserve of high-quality, sandy pitrun gravel and can be re-used as granular
structural fill under buildings or as sub-base gravel under asphalt areas.
The native, clean sandy gravel is the “target” foundation bearing material for all footings,
including perimeter, interior, and exterior footings.
Groundwater Conditions
During our test pits in January, groundwater was encountered at depths of 7.0 to 9.0 feet in the north,
central, and eastern parts of the site. Two pits (TP-7 and TP-8) were dug in the southwest portion of the
property where the surface terrain appeared to be a little lower. In both of these pits, the groundwater
table was shallower and found at 5.0 feet. The depth of the water relative to the top of the native sandy
gravel was generally 5.0 to 7.0 feet below the gravel in most areas, but decreased to 2.8 to 3.0 feet in
the southwest corner. See Figure 5 for the distribution of groundwater depth across the site.
Provided in Table 4 (on the following page) is a summary of the groundwater measurements in each of
the test pits, along with its positon relative to the top of the sandy gravel. As stated previously, all test
pits were backfilled with PVC monitoring wells. The approximate casing height of each well is also listed
in the table.
DEPARTMENT OF THE ARMY CORPS OF ENGINEERS, OMAHA DISTRICT HELENA REGULATORY OFFICE 10 WEST 15TH STREET, SUITE 2200 HELENA, MONTANA 59626 REPLY TO ATTENTION OF
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January 19, 2018 Regulatory Branch
Montana State Program Corps No. NWO-2017-02234-MTH
Subject: TKO Enterprises (Vaughn Environmental Services) - Cottonwood Subdivision - Farmer's Canal - (Gallatin County)
Tyson Olsen TKO Enterprises Po Box 10303 Bozeman, Montana 59719 Dear Mr. Olsen: We are responding to your request for Nationwide Permit (NWP) verification for the above-mentioned project. The project is located at Latitude 45.665522°, Longitude -111.101588°, on or near Farmers Canal, within Section 15, Township 2 S, Range 5 E, Gallatin County, Montana.
Specifically, you requested authorization for the following work in waters of the U.S.:
Work Item Description
a.
Approximately 1,095 cubic yards (cy3) of native fill, 361 cy3 of 6-inch minus of uncrushed subbase course, 123 cy3 of 1.5-inch crushed gravel and 96 cy3 of
asphalt will be used to fill 0.307 acre of jurisdictional wetland in preparation to develop are for a residential subdivision. In addition, a 30-inch reinforced concrete culvert will be placed across Cottonwood road and will be extended 22 linear feet.
Based on the information you provided, the proposed activity, permanently affecting approximately 0.307 acre of jurisdictional Wetlands, is authorized by NWP 29, found in the
January 6, 2017, Federal Register (82 FR 1860), Reissuance of Nationwide Permits. Enclosed is a fact sheet that fully describes this NWP and lists the General and Regional Conditions that must be adhered to for this authorization to remain valid. Please note that deviations from the
original plans and specifications of your project could require additional authorization from this office.
In addition to conditions referenced above, the following special conditions apply: Condition Description
1.
Compensatory mitigation will be required for the 0.307 acre of unavoidable impacts to the wetlands adjacent to Farmers Canal. It has been determined that a practicable alternative to compensate for the aquatic resource functions that will be lost as a result of the permitted activity is mitigation by a third party provider. You have selected the Upper Missouri Mitigation Bank (SRI Missouri Headwaters,
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LLC and Eco-Asset Management, LLC) as the party or parties responsible for the implementation, performance, and long-term management of the compensatory
mitigation project (332.3[l][1]) and so the following specific provisions apply: 1. Credits must be secured from a third party provider authorized by the U.S. Army Corps of Engineers to provide the mitigation;
2. Credits must come from the same service area as the permitted impacts, as specified in the authorized third party provider’s mitigation strategy or executed Banking Agreement; and The applicant must use the authorized third party provider’s credit multipliers in determining the amount of credits to be purchased (for Upper Missouri Mitigation Bank the multipliers are the same as for the Omaha District) namely (i) released credits are secured on a 1:1 ratio (1 impact debit to 1 mitigation credit), and (ii) after-the-fact credits are secured on a 1:1.5 ratio. In this case 0.307 acres of wetland mitigation credits will be required prior to working in Waters of the U.S., provide this office with documentation of completion of the transaction for securing credits. This can be a letter from the third party provider stating its acceptance of
responsibility for the specified mitigation.
You are responsible for ensuring that all work is performed in accordance with the terms and conditions of the NWP. If a contractor or other authorized representative will be conducting work on your behalf it is strongly recommended that they be provided a copy of this letter and the enclosed conditions. Failure to comply with the General and Regional Conditions of this NWP, or the project-specific special conditions of this authorization, may result in the suspension or revocation of your authorization and may be subject to appropriate enforcement action. The Montana Department of Environmental Quality has provided the enclosed CWA
Section 401 water quality certification for this NWP which includes General Conditions, all of which must be complied with for that certification to remain valid. This does not eliminate the need to obtain other permits that may be required by that agency. This verification is valid until March 18, 2022, when the existing NWPs are scheduled to be modified, reissued, or revoked. Furthermore, if you commence or are under contract to
commence this activity before the date that the relevant NWP is modified, reissued or revoked, you will have twelve (12) months from the date of the modification, reissuance or revocation of the NWP to complete the activity under the present terms and conditions unless discretionary authority has been exercised on a case-by-case basis to modify, suspend, or revoke the authorization in accordance with 33 CFR 330.4(e) and 33 CFR 330.5 (c) or (d). Project specific special conditions listed in this letter continue to remain in effect after the NWP verification expires, unless the district engineer removes those conditions. Activities completed under the authorization of an NWP which was in effect at the time the activity was completed continue to
be authorized by that NWP. In compliance with General Condition 30, we have enclosed a "compliance certification"
form, which must be signed and returned within 30 days of completion of the project, including
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any required mitigation. Your signature on this form certifies that you have completed the work in accordance with the terms and conditions of the NWP. The Omaha District, Regulatory Branch is committed to providing quality and timely service to our customers. In an effort to improve customer service, please take a moment to complete our Customer Service Survey found on our website at: http://corpsmapu.usace.army.mil/cm_apex/f?p=regulatory_survey. If you do not have Internet access, you may call and request a paper copy of the survey that you can complete and return to us by mail or fax.
Please refer to identification number NWO-2017-02234-MTH in any correspondence concerning this project. If you have any questions, please contact Timothy McNew at Helena
Regulatory Office 10 West 15 Street, Suite 2200 Helena, Montana 59626, by email at
Timothy.M.McNew@usace.army.mil, or telephone at (406) 441-1375.
Sincerely, Todd N. Tillinger P.E. Montana Program Manager Enclosures: Compliance Certification NWP 29 Fact Sheet with Regional Conditions
Montana DEQ CWA Section 401 Water Quality Certification cc:
Barb Vaughn via e-mail: bvaughn@montana.com
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COMPLIANCE CERTIFICATION Corps File Number: NWO-2017-02234-MTH Permit Type: NWP 29
Name of Permittee: Tyson Olsen County: Gallatin County, Montana Date of Issuance: January 18, 2018
Corps Project Manager: Timothy McNew Upon completion of the activity authorized by this permit and any mitigation required by the permit, sign this certification and return it to the following address: US Army Corps of Engineers Omaha District Helena Regulatory Office 10 West 15 Street, Suite 2200 Helena, Montana 59626 Please note that your permitted activity is subject to a compliance inspection by a U.S. Army
Corps of Engineers representative. If you fail to comply with the conditions of this permit, you are subject to permit suspension, modification, or revocation.
- - - - - - - - - - - - - - - - - - - - - - - - - - - I hereby certify that the work authorized by the above referenced permit has been completed in accordance with the terms and conditions of the said permit, and required mitigation was completed in accordance with the permit conditions. _______________________________________ Signature of Permittee
___________________ Date
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Appendix B: Cottonwood Subdivision Water Main Report Excerpts
Cottonwood Subdivision
Water Design Report
Page 1 of 4
COTTONWOOD SUBDIVISION
WATER MAIN DESIGN REPORT
A. General
This design report will give an overview of the proposed 8” water main extensions for the
development of the Cottonwood Subdivision, located at the intersection of Cottonwood Rd and
Loyal Drive in Bozeman. The 28-acre subdivision is zoned R-5 and will consist of multi-
residential units. The proposed improvements are anticipated to be phased, with the first phase
being constructed in 2021.
This report includes a description of the proposed water main extensions and design parameters.
Once the water main is constructed and approved, the main will become a part of the City of
Bozeman (COB) system. The following references were used in the preparation of this report:
a. COB Design Standards and Specifications Policy, 2004. Addendum #5
b. COB Modifications to Montana Public Works Standard Specifications (MPWSS).
c. WQB Circular No. 1
d. City of Bozeman Zoning Map
e. Uniform Plumbing Code
f. City of Bozeman Water Facility Plan Update, July 2017
A.1. Site Conditions
Soil conditions on site consist of a native topsoil to a depth of approximately 12 inches, which is
underlain by a thin, intermediate layer of stiff, silt/clay. Beginning at depths of 1.2 to 2.5 feet is
an alluvial deposit of clean, sandy gravel that underlies much of the Bozeman area at relatively
shallow depths. This clean, sandy gravel extended to the bottom of all 10 to 11 foot test pits.
Groundwater depths on site are, on average, to a depth of 7 to 9 feet in the north, central, and
east sides of the property, but at a shallower 5-foot depth on the south and southwest sides.
Groundwater levels were monitored during the spring and summer of 2018. The highest
groundwater levels were recorded in mid-April and showed shallow water conditions across the
site. Throughout most of the site, the seasonal high water depths ranged from 3 to 4 feet, but
rose to as high as 1.0 to 2.5 feet below the ground surface in the site’s southwest corner. Water
flows on site in a in a northwesterly direction.
No basements are advised on site. Crawl spaces are only recommended if the depth is limited
below existing site grades, in-filling the crawl space up to the top of footings with a clean
crushed rock layer, and installing subsurface drainage measure. Otherwise, at-grade slabs with
perimeter footings and frost walls are recommended.
The site is in an “Area of Minimal Flood Hazard” per the FEMA Panel 30031C0811D.
B. Existing Water Supply
The proposed water main extensions will be connected to the existing COB water distribution
system in Cottonwood Road at Loyal Drive and Alpha Drive as well as in Huffine Road. The
Cottonwood Subdivision
Water Design Report
Page 2 of 4
following information regarding pressures of the existing system was obtained from the City of
Bozeman:
Fire Hydrant – Golden Gate and Advanced Drive. Hydrants 2201 and 2202
Static Pressure: 115 psi
Pitot Pressure: 80 psi
Residual Pressure: 110 psi
Hydrant Discharge During Test: 1,494 gpm
Distribution Main Capacity – Fire flow at minimum residual pressure
Qr = Qt[(Ps – Pr)/(Ps – Pt)]0.54
Qr = 1,494[(115 – 20)/(115 – 80)]0.54
Qr = 2,562 gpm
Qt = Hydrant Discharge During Test (gpm)
Qr = Fire Flow at Minimum Residual Pressure (psi)
Ps = Static Pressure (psi)
Pm = Minimum Residual Pressure (psi)
Pr = Residual Pressure (psi)
Pt = Pitot Pressure (psi)
C. Proposed Water System
The proposed water main extension will consist of approximately 4,030 lf of 8" Class 51 Ductile
Iron Pipe within the subdivision's local streets. The proposed main will connect to an 8-inch stub
in Cottonwood Road and Loyal Drive, and also be connected to the 10" water main in Huffine
Lane. The layout of the proposed water main meets the City of Bozeman design criteria and will
be located both within the right-of way and a proposed 30’ wide easement in which the water
main will be installed from the subdivision north to Huffine. The water main will be separated
from the proposed sanitary sewer main by a minimum distance of 10 feet. The layout of the
proposed water main meets the COB design criteria. Fire hydrants will be installed so not to
exceed 600’ spacing, fulfilling the distance requirement for fire hydrant spacing, as well as
assisting in flushing of the main. Gate valves will be installed at the connection point to the
existing mains as well as on property lines, per City standards. Blow-offs have been designed
for all dead-end lines that will be extended in the future. Depending on lot layout, each building
within the subdivision will either be served by a service line connecting directly to the water
main or by a main extension looping through that lot.
This system is not expected to be extended or expanded past what is proposed in this report, as
all lots within the subdivision are accounted for in this report. If any extensions are required in
the future, that developer will be required to analyze and submit a report to the City of Bozeman
and the MDEQ for review (DEQ 1.1.2.c. and d., and 1.1.14).
D. Capacity Analysis
A capacity analysis was performed on the proposed water main extension for the 28-acre
subdivision of R-5, residential mixed-use high density. The water main extension has been
Cottonwood Subdivision
Water Design Report
Page 3 of 4
designed to meet the maximum day demand plus fire flow during the peak hour. The City does
not have design standards for R-5 mixed-use high density residential. To determine the water
demand for the entire subdivision, the density was assumed based on the proposed 400 units over
the 16.76 developable acres, and the City of Bozeman design of 170 gpd per capita and 2.17
persons/unit. This equates to 23.89 units/acre. The main will be looped into the existing City of
Bozeman system. Table 1 shows the water demand for the entire subdivision.
TABLE 1
WATER DEMAND – RESIDENTIAL
Zoning Units Density
(residents/unit)
Per Capita Flow
(gpd/resident) Total Flow
R-5 400 2.17 170 147,560 (gpd)
103 (gpm)
It is anticipated that the average daily demand for the subdivision will be 103 gpm. In addition
to the average daily demand, the water main extension must account for peak periods of daily
use. Peaking factors are applied to the demand and account for these peak periods in daily use.
The peaking factors used are maximum daily use and peak hour and are obtained from the City
of Bozeman Design Standards. Table 2 shows the peaking factors and the resultant flows from
those factors when applied to the average daily demand of 103 gpm.
TABLE 2
PEAKING FACTORS
Flow Designation Peaking Factor Flow (gpm)
Average Day Demand 1 103
Maximum Day Demand 2.3 236.90
Maximum Hour Demand 3 309
The required fire flow for Type V-B structures is 1,500 gpm. With a fire flow demand of 1,500
gpm and a peak hour demand of 309 gpm, a peak hour flow of 1,809 gpm (4.04 cfs) is required.
A Hazen-Williams “C” Factor of 130 was used in the pipe evaluation. The working residual
water pressure shall not be less than 20 psi at any point in the water distribution system under
maximum day plus fire flow. The velocity shall not exceed 15 feet per second through the main
line.
E. Results
Flow analysis of the 8-inch D.I. pipe with a C value of 130 can provide the required 1,809 gpm.
The maximum pipe velocity will not exceed 15 ft/s, as illustrated in the attached WaterCad
Automated Fire Flow Analysis. Using the hydrant flow data listed on page 2 of this report, a
three-point pump curve was generated to simulate existing conditions within the City of
Bozeman water system. The residual pressure is typically used to model the low point on the
pump curve. For this simulation however, the pitot pressure was used as the low point on the
pump curve to ensure a conservative design (residual pressure = 110 psi, pitot pressure = 80 psi).
The minimum system pressure during a fire event is 52 psi, which exceeds the minimum
Cottonwood Subdivision
Water Design Report
Page 4 of 4
required pressure of 20 psi. Capacity analysis calculations outlining the capacity of the proposed
8-inch pipe are included in the appendix of this report.
F. Conclusion
Based on this analysis, the proposed 8-inch water main extensions for the proposed Cottonwood
Subdivision provide adequate service to meet the peak hour demand and fire flows for the
development. This project will require the approval of the City Engineer and MDEQ.
Appendix
1. WaterCad Analysis
2. City of Bozeman Proposed Water Distribution System Figure 9-2
3. Exhibit A – Sewer and Water Main Exhibit
cushingterrell.com
Appendix C: Phase 1 Water Main Design Report
cushingterrell.com
Appendix D: Calculations and Back-up Data
Scenario: Base
Page 1 of 176 Watertown Road, Suite 2D Thomaston, CT 06787 USA +1-203-
755-1666
12/19/2024
WaterCAD
[10.03.05.05]Bentley Systems, Inc. Haestad Methods Solution CenterCottonwood Phase 2 Water Main extension.wtg
Scenario: Base
Current Time Step: 0.000 h
Fire Flow Node FlexTable: Fire Flow Results Table
L:\COTTONWOOD_P2\Docs\5_Team\5.1_Civil\Water System\Model\Cottonwood Phase 2 Water Main extension.wtg
Label Zone Satisfies Fire Flow Constraints?Fire Flow Status Fire Flow (Needed) (gpm)
Fire Flow (Available) (gpm)
Flow (Total Needed) (gpm)
Flow (Total Available) (gpm)
Pressure (Residual Lower Limit) (psi)
Pressure (Calculated Residual) (psi)
Pressure (Zone Lower Limit) (psi)
Pressure (Calculated Zone Lower Limit) (psi)
Junction w/ Minimum Pressure (Zone)
Pressure (System Lower Limit) (psi)
Pressure (Calculated System Lower Limit)
(psi)
Junction w/ Minimum Pressure (System)
Is Fire Flow Run Balanced?
J-1 <None>True Passed 1,549 1,998 1,598 2,047 20 28 20 20 J-12 (N/A)20 J-12 TrueJ-2 <None>True Passed 1,549 1,901 1,598 1,950 20 24 20 20 J-12 (N/A)20 J-12 TrueJ-3 <None>True Passed 1,549 1,901 1,598 1,950 20 22 20 20 J-12 (N/A)20 J-12 TrueJ-4 <None>True Passed 1,549 1,811 1,598 1,860 20 20 20 28 J-12 (N/A)28 J-12 TrueJ-5 <None>True Passed 1,549 1,860 1,598 1,909 20 22 20 20 J-7 (N/A)20 J-7 True
J-6 <None>True Passed 1,549 1,847 1,598 1,896 20 22 20 20 J-7 (N/A)20 J-7 True
J-7 <None>True Passed 1,549 1,700 1,598 1,749 20 20 20 34 J-12 (N/A)34 J-12 True
J-8 <None>True Passed 1,549 1,845 1,598 1,894 20 22 20 20 J-12 (N/A)20 J-12 True
J-9 <None>True Passed 1,549 1,843 1,598 1,892 20 22 20 20 J-12 (N/A)20 J-12 True
J-10 <None>True Passed 1,549 1,855 1,598 1,904 20 20 20 20 J-11 (N/A)20 J-11 TrueJ-11 <None>True Passed 1,549 1,818 1,598 1,867 20 20 20 23 J-10 (N/A)23 J-10 TrueJ-12 <None>True Passed 1,549 1,774 1,598 1,823 20 20 20 27 J-17 (N)(N/A)27 J-17 (N)TrueJ-13 <None>True Passed 1,549 1,912 1,598 1,961 20 22 20 20 J-12 (N/A)20 J-12 TrueJ-15 <None>True Passed 1,549 1,931 1,598 1,980 20 26 20 20 J-12 (N/A)20 J-12 TrueJ-16 (N)<None>True Passed 1,549 1,887 1,598 1,936 20 22 20 20 J-10 (N/A)20 J-10 TrueJ-17 (N)<None>True Passed 1,549 1,797 1,598 1,846 20 20 20 24 J-12 (N/A)24 J-12 TrueJ-23 <None>True Passed 1,549 1,917 1,598 1,966 20 23 20 20 J-12 (N/A)20 J-12 TrueJ-24 <None>True Passed 1,549 1,912 1,598 1,961 20 22 20 20 J-12 (N/A)20 J-12 TrueH-1 <None>True Passed 1,549 1,921 1,549 1,921 20 20 20 20 J-12 (N/A)20 J-12 TrueJ-25 <None>True Passed 1,549 1,921 1,598 1,970 20 24 20 20 J-12 (N/A)20 J-12 True
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