PROJ01996

• Contract/PO #: FS0068FX
• Contractor Name: Minturn, Town of
• Contract Type: Loan
• Water District: 0
• Loan Projects - Doc Type: Feasibility Study

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level drop corresponding to 100,000 gallons, while the second pump was set to turn on at a
further drop of 100,000 gallons. These settings were chosen to maintain a relatively high rate
of water exchange through the tank, By adjusting these settings so that the pumps are activated
in response to a smaller withdrawal volume, the equalization volumes cited above could be
substantially reduced,

Emergency Volume: Emergency volume is that quantity of stored water needed to meet water
demands during temporary shutdown of the treatment works. A time period of eight (8) hours
was selected as the upper time limit for which storage would be expected to act as a the sole
source of emergency supply, Using an average daily demand rate of 0.5 mgd( the resulting
emergency volume is found to be 167,000 gallons, It should be noted that the most likely
emergency scenario, a power outage, would not necessarily require the use of stored water, since
the treatment plant is at sufficiently high elevation to allow gravity flow at sufficient rate and
pressure to meet normal demands, Indeed this is how water is currently supplied to the system.
However, emergency scenarios whiCh involve the rupture of the treatment plant transmission
main, or which involve contamination events of the raw water supply or clearwell would require
water be supplied from the storage tank.

Fire Protection Volume: Fire protection volume is that quantity of stored water needed to
supplement water supplied from the treatment works in order to satisfied required fire flow.
The Town has several structures for which the Insurance Services Office (ISO) has determined
a 3500 gpm fire flow. The duration for a flow of this magnitude, as recommended by the ISO,
is three hours, Thus, the total fire volume required is 630,000 gallons. However, after deducting
the portion of the total flow which would be provided by the water supply pumps at the
treatment plant, the required volume of water in storage was found to be 560,000 gallons. Since
the ISO gives credit for stored water volume corresponding to the minimum tank levels reached
on an average day, fire protection volume is in addition to the 100,000 gallon equalization
volume.

Based upon the criteria stated above, the more conservative (Le. higher volume) approach for
calculating total storage need yields a volume of 830,000 gallons, as summarized below.

Equalization Volume:
Emergency Volume:
Fire Protection Volume:
Total Volume:

100,000 gal (average day)
167,000
560.000
830,000 gal

As an alternative, a smaller tank size was considered. It is not unusual for water planners to
include emergency water and fire protection water in the same tank volume. Thus this

Town of Minturn Water System Upgrade Project, March, 1995

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