214010-020-mtn-home-2019-10-31-wfps-report

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Mountain Home Water Facilities Planning Study Update October 2019
pipelines and prone to failure. City staff has requested that the two areas that contain
transite pipe, the subdivision north of the City’s water shop and the subdivision on N 4th W
near West Elementary school, be targeted for Priority 1 pipeline replacement.
3.7.2. Distribution System Improvements Alternatives
No Action Alternative
Failure to correct existing distribution system deficiencies will result in development
restrictions for the City of Mountain Home. As population grows and system demand rises,
pressures will continue to be at risk of dropping below 40 psi during peak hour demands.
Mandatory curtailment could be required to ensure pressures are above 40 psi if one of the
larger City wells is off-line during peak demand periods. Additionally, fire protection will be
substandard for several locations.
Additionally, this alternative will leave the transite pipe in place, and the issues with said
pipelines reported by City staff will remain unresolved.
Existing Pipeline Improvements
To improve transmission to portions of town which experience pressure or fire flow
deficiencies, upsizing existing pipelines or constructing parallel pipelines can be
implemented to address said deficiencies. Pipelines that would benefit from upsizing or
parallel pipe installation were modeled and the benefits were discussed with City staff. The
pros and cons of installation of parallel transmission lines vs pipeline replacement is
discussed in Table 3.7.
Table 3.6: Pros and Cons of Parallel Pipeline Installation vs Pipeline Replacement
Parallel Lines
Replacement
Pros
- Reduces temporary services during
construction
- Lower construction cost
- Only 1 pipeline to maintain
- Lower O&M cost over time
Cons
- 2 pipelines to maintain
- Larger O&M cost over time
- Higher construction cost
New Pipeline Construction
In locations where pipeline upsizing or parallel pipelines may not provide a huge benefit,
installation of new pipelines may provide that benefit. These new pipelines may provide
looping benefits and/or draw water from a nearby portion of town that do not experience
deficiencies. Pipelines that would benefit from new construction were modeled and vetted
with City staff. In addition, as the City expands, new pipelines will need to be constructed
for service to those areas. Areas of anticipated growth a can be found in Appendix A. While,
in general, the development community is responsible for extending waterlines, their
developments often do not require more than 8-inch diameter pipelines, where in many
cases larger pipelines are desired to provide improved transmission or serve adjacent future
developments. In these cases, the City has expressed interest in compensating the
contractor for the cost of upsizing the pipe. The costs of upsizing are reflected in the CIP list
in Section 4.3 of this report.
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