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

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Mountain Home Water Facilities Planning Study Update October 2019
20 psi. For Mountain Home, there are approximately 19 structures with fire demands of 2500+ gpm, of
which 2 have demands of 4000+ gpm. Keller Associates recommends that a maximum fire demand of
4000 gpm for 4 hours be provided. This is consistent with previous planning assumptions and industry
standards. A copy of the original ISRB data along with a letter from the local fire authority can be found
in Appendix C. For future growth in areas zoned commercial/industrial, a minimum of 2,500 gpm at 20
psi for 2 hours is recommended.
In addition to design standards for the delivery of flow rates, standards for system pressures are
necessary for the normal daily operation of the water system. The aim of standards for pressure is to
provide safe and reliable service to water users under a variety of system conditions. If pressures are
too high, damage can occur within the distribution system and at points of use. If pressures are too low,
a variety of issues arise including back flow contamination, and low or no water availability. The
recommended distribution pressure standards for new connections are listed in Table 2.6. These
pressures are consistent with current DEQ standards.
System Scenario
Table 2.6 – Distribution System Pressure Standards
3.0 EXISTING FACILITIES EVALUATION AND ALTERNATIVES
The Mountain Home water system is comprised of nine potable water wells, four storage reservoirs, two
booster stations, and a network of distribution pipelines that conveys water to users spread throughout
three pressures zones. This chapter provides an analysis of Mountain Home’s existing system
components of supply, storage, delivery, and distribution with respect to the design criteria presented in
Chapter 2 of this report. The most recent Sanitary Survey performed on the Mountain Home’s water
system in April 2018 revealed four deficiencies, primarily concerning proper screening on well
overflow/discharge lines, an open port on a well, and secondary containment for fuel. All of these
deficiencies were addressed by the City prior to October 10th, 2018 and are not included as part of this
existing system evaluation. A copy of the action summary of the Sanitary Survey has been included in
Appendix F for reference.
3.1 STUDY AREA
The study area was developed in close coordination with City planning staff. Areas of probable
residential and commercial development were identified. Figure 3.1 in Appendix A illustrates the study
area and land use contemplated for this planning study. This planning effort focuses on the projected
2040 growth areas.
3.2 EXISTING ENVIRONMENTAL CONDITIONS
This portion of the report presents a general overview of existing environmental conditions within the
study area. Should the City seek DEQ funding for priority improvements, a separate Environmental
Information Document (EID) will need to be completed.
3.3.1. Physical Aspects: Topography, Geology and Soils
Pressure (psi)
Peak Hour Demand Event - Minimum 40+
Maximum Day Demand Plus Fire - Minimum 20+
Mainline Pressures - Maximum (without special pipe design) 100
Pressures at service without Pressure Regulator - Maximum 80
The City of Mountain Home is relatively flat, with elevations ranging from approximately
3,080 to 3,400 feet above sea level. The highest elevations are north and east of the City,
with elevations dropping to the south and west.
CITY OF MOUNTAIN HOME | KA 214010-020 8