PROJ00156

• Contract/PO #: C153721
• Contractor Name: Lyons, Town of
• Contract Type: Loan
• Water District: 5
• County: Boulder
• Loan Projects - Doc Type: Feasibility Study

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Table 7. Pressure Zone Data
Zone Upper Limit Lower Limit
Upper zone 5584 (40 psi) 5422 (108 psi)
Lower zone 5422 (40 psi) Varies
Notes:
I. Elevations were determined by subtracting the head loss produced by the maximum
day flow at the most remote fire hydrant location (28 feet) and 40 psi pressure (92 feet)
at the hydrant from the top level of the storage tank or hydraulic grade of the PRV.
2. Data subject to model calibration.
3. Refer to Figure 5.

Ions. The town has 1.35 MG of active storage in the upper and lower pressure zones. The
town owns a third tank, located near the treatment plant, which is not in use. Storage must be
adequate to:

· backup the treatment facility during mechanical failures. If the storage provided is
equal to the maximum daily demand, this will allow the operators 24 hours to bring the
plant back on-line if the failure occurs on the peak day. If the failure occurs on an
average day, this should provide approximately 4 days to bring the plant back on-line.

Using the worst case scenario, failure of the plant during a peak day demand period would
require the Utility Department to institute emergency "no watering" measures until the plant is
back on-line, thus conserving the available storage.

. provide adequate volume for fire flow. This component is determined by the local
fire authority and the town standards. If a fire flow of 1500 gallons per minute
(g.p.m.) is required at a minimum pressure of 20 psi at the hydrant sustained for two
hours, the total storage volume required is 180,000 gallons.

Combining 1.03 MG for peak day usage with 0.18 MG for fire flow requires about 1.21 MG
of storage. The available 1.35 MG is adequate but close to the requirement, assuming both
tanks are full when the worst case demand occurs. More relevant is the system reliability to
utilize this storage. If a failure should occur in the 2.5 mile I2-inch diameter transmission
line, available storage is inadequate to meet most domestic/commercial demands on the
system. Furthermore, as explained later in this section, without the service of the transmission
line, the upper zone adjacent to town will be without any water for fire protection or other
uses. Pertaining to condition of the storage tanks, utility personnel report that all tanks have
been inspected and are in good repair.

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