HomeMy WebLinkAbout012.2 - SRXII - Water Corrosivity Analysis
SOUTH RANGE CROSSING NORTH
SUBDIVISION
WATER SYSTEM IMPROVEMENTS
DESIGN REPORT
November 2024
PREPARED BY:
MMI #: 5659.021
3
5 SITE CONDITIONS (1.1.4)
The SRX-II property is currently undeveloped agricultural land which gently slopes from south to
north with existing grades of less than 4% and mostly Meadowcreek loam and Blackmore silt
loam, Turner loam, and Enbar-Nythar loam deposits (USDA, Natural Resources Conservation
Service, Web Soil Survey) as shown in Appendix F.
A geotechnical report has been completed for SRX-II by Rawhide Engineering Inc dated February
22, 2024 and is included as Appendix G.
Seasonally-high groundwater levels onsite range between approximately 1 and 3 feet below
existing grade based on well monitoring performed from May 2023 to September 2023. The
groundwater flows generally from the south to the north based on generally observed groundwater
flows in Bozeman. A corrosivity test was performed for SRX-II using soil samples collected during
the geotechnical investigation. The corrosivity soil samples had very similar scores ranging from
25-35, recommending ductile water mains to be wrapped with V-Bio® Enhanced Polyethylene
Encasement.
6 WATER USE DATA, INCLUDING (1.1.5):
The water distribution system serving the proposed project will be designed and installed in
accordance with the Montana Department of Environmental Quality (MDEQ) Circular No. 1 (DEQ-
1); Montana Public Works Standard Specifications (MPWSS); the City of Bozeman Modifications
to MPWSS; City of Bozeman Water Facility Plan; and the City of Bozeman Design Standards and
Specifications Policy (and all addenda thereto). The following section addresses the design
capacity and flow requirements discussed in Section 8 of DEQ-1.
For this report, water demands were calculated and modeled for two different scenarios. The first
scenario provides water for Block 1 and Block 2 of the subdivision. The second scenario will
provide water throughout the subdivision including Restricted Lot 1. The capacity requirement for
the water main extension is calculated as follows:
SRX-II is proposed to be zoned REMU with the exception of Block 1 proposed to be zoned B2-
M. The Water Facility Plan Update (WFPU) dated July 2017, Table 3.7-Future Infill Zoning District
WDFs, states an average day demand for REMU is 873 gpad, and demand from B2-M is 705
gpad. The usage of Block 2 is known and is proposing 341 units. The average daily demand
(ADD) can also be calculated using 135 gallons per capita per day at 2.17 people per dwelling
unit. Block 2 is proposed to have an ADD of 99,896 gpd across 9.19 acres equating to 10,870
gpad.
The expected demand for these water main extensions is in the following paragraphs:
Peaking factors were applied to expected average daily demands in accordance with Design
Values from City of Bozeman Design Standards, March 2020 Version, including:
Maximum Day Demand (MDD) Peaking Factor = 2.3
Maximum Hour (Peak Hour) Demand (PHD) Peaking Factor = 3.0
H
APPENDIX H
CORROSIVITY ANALYSIS
South Range Crossing North
Dipra Corrosivity Likelihood Score Sheet
(ohm-cm)(points)(ppm)(points)(%)(points)(yes/no)(points)(s.u.)(points)(ppm)(points)(mv)(points)Yes/No (points)
TP-1 1740 19 19 0 >15 5 yes 5 7.7 0 36 4 303 0 Yes 2 35
TP-2 1870 19 23 0 >15 5 yes 5 7.6 0 30 4 292 0 Yes 2 35
TP-4 1570 19 20 0 >15 5 yes 5 7.8 0 42 4 295 0 Yes 2 35
TP-6 2250 10 16 0 >15 5 yes 5 7.8 0 23 4 294 0 Yes 2 26
Total
PointsSample
Bi-Metallic ConsiderationsRedox PotentialSulfide IonsPHGround Water InfluenceMoisture ContentChloridesResistivity
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South Range Crossing North
Dipra Consequence Score Sheet
(in)(points)Classification (points)(ft)(points)(yes/no)(points)
Onsite <24 0 Routine 0 <10 0 Yes 0 0
Total
PointsLocation
Pipe Diameter Location Depth of Cover Alternate Water Supply
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5
< 500 ohm-cm 30
500 - 1000 ohm-cm 25
> 1000 - 1500 ohm-cm 22
> 1500 - 2000 ohm-cm 19
> 2000 - 3000 ohm-cm 10
> 3000 - 5000 ohm-cm 5
> 5000 ohm-cm 0
> 100 ppm = positive 8
50 - 100 ppm = trace 3
< 50 ppm = negative 0
> 15% = Wet 5
5 - 15% = Moist 2.5
< 5% = Dry 0
Pipe below the water 5
table at any time
pH 0 - 4 4
pH > 4 - 6 1
pH 6 - 8, with sulfides
and low or negative redox 4
pH > 6 0
positive ( 1 ppm)4
trace ( > 0 and < 1 ppm) 1.5
negative ( 0 ppm) 0
= negative 2
= positive 0 - 100 mv 1
= positive > 100 mv 0
Connected to noble metals 2
(e.g. copper) - yes
Connected to noble metals 0
(e.g. copper) - no
TOTAL POSSIBLE POINTS
Cinders, Mine Waste, Peat Bog,
Landfill, Fly Ash, Coal
RESISTIVITY
CHLORIDES
MOISTURE
CONTENT
GROUND WATER
INFLUENCE
pH
SULFIDE
IONS
REDOX
POTENTIAL
BI-METALLIC
CONSIDERATIONS
Known Corrosive
Environments
POINTS
30
8
5
5
4
4
2
2
60
21
* Soils with Known Corrosive Environments shall be assigned 21 points
or the total of points for Likelihood Factors, whichever is greater.
Likelihood Score Sheet
TABLE 2
– >
– >
MAXIMUM
POSSIBLE
POINTS
LIKELIHOOD FACTOR
6
DIPRA and Corrpro again listened to the needs of utility
operators and recognized the differences between long,
large diameter, straight-run transmission mains and the
more complicated networks of distribution pipelines that
bring water to our neighborhoods and businesses. The result
provides a more practical solution for pipeline networks that
comprise the distribution systems within a utility’s service
area. The use of V-Bio® enhanced polyethylene encasement
in conjunction with metallized zinc provides water operators
with an effective alternative to controlling corrosion in
distribution systems.
3” to 24” 0
30” to 36” 8
42” to 48” 12
54” to 64” 22
Routine (Fair to good access,
minimal traffic/other utility 0
consideration, etc.)
Moderate (Typical business/
residential areas, some right 8
of way limitations, etc.)
Difficult (Subaqueous
crossings, downtown
metropolitan business areas, 20 multiple utilities congestion,
swamps, etc.)
0 to 10 feet depth 0
> 10 to 20 feet depth 3
> 20 feet depth 5
Alternate supply available - no 3
Alternate supply available - yes 0
TOTAL POSSIBLE POINTS
PIPE SERVICE
LOCATION:
Construction-Repair
Considerations
DEPTH OF COVER
CONSIDERATIONS
ALTERNATE WATER SUPPLY
POINTS
22
20
5
3
50
Consequence Score Sheet
TABLE 3
The revised
DDM® recognizes
the practical
differences in
corrosion control
needs between
transmission mains
and distribution
systems.
MAXIMUM
POSSIBLE
POINTS
CONSEQUENCE FACTOR