PROJ00001

• Contract/PO #: C153168
• Contractor Name: Delta, City of
• Contract Type: Loan
• Water District: 40
• County: Delta
• Bill Number: SB 77-35
• Loan Projects - Doc Type: Feasibility Study

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Filtration Plant

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The existing filtration plant consists of four pressure filter units
located approximately two miles north of the City of Delta at an elevation
of approximately 5,080 feet above mean sea level. The filtration plant was
completed in early 1968 as part of an overall program to improve the
previous existing treatment facilities. Two existing pressure filter
units, incidently purchased from the City of Gunnison, Colorado, were
"rehabilitated" by replacing the existing sand media with an improved
filter media. Two more filter units were also added to increase capacity.
The filtration plant also houses a small but well equipped laboratory for
testing water quality of various water samples.

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Construction of the water treatment facilities was financed through
1967 general obligation bonds which are presently being retired by revenue
from water sales and not by tax levy. The filtration plant began producing
treated water for use in the City on May 22, 1968.

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The capacity of all four units as a whole at any given time depends
on the degree of material collected on each of the filter units. As more
and more material is filtered from the water, the pressure differential
across each filter unit will increase. The entrapped material tends to
make the filter unit less efficient and the "capacity" in effect steadily
decreases until the next backwash cycle. By staggering the backwash of
each filter unit, the plant as a whole will have a more uniform
capacity.

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Calculation of the maximum capacity of the filtration plant depends
on what period of time is used as a basis. The scales on each filter rate
indicator range from 0 to 1.5 million gallons per day (0 to 1,042 gpm) and
the plant effluent tube was specified to have a rated maximum capacity of
6.0 million gallons per day (4,167 gpm). During short peak periods of
operation lasting for no more than a few hours at any given time, the
filtration plant has been able to produce finished water at a maximum rate
of about 3,500 gallons per minute. If this rate of production were
continued over a 24 hour period, this rate of production would be
equivalent to a sustained rate of about 5.0 million gallons per day.
However, the actual maximum rate of production over a 24 hour sustained
period has always been at a lesser rate of around 3.5 million gallons per
day (2,430 gpm). This rate is believed to be the most efficient
sustainable level of production of the existing facilities. Above this
level, there are sometimes unexplained (and perhaps unfounded) claims of
sand being passed into the distribution system. We suspicion that the high
velocities through the pipeline are removing sand and silt that had been
deposited in the lines prior to the construction of the filter plant. Over
the seven year period of operation, the filter plant has seldom produced
filtered water at an average rate over 3.5 million gallons per day based
on a 24 hour period of continuous operation. A summary of filtration plant
capacity is shown in Table III-i.

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III - 10

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