HomeMy WebLinkAbout01/05/1993, 4 - EXPLORATORY NON-POTABLE WELL AT WATER RECLAMATION FACILITY1IIINI11I11 QUINfI MEETING DATE:
1W� 11 city Of Sark �aIS OBISPO January 5 1993
so COUNCIL AGENDA REPORT 0�
FROM: John Moss L ',.( Prepared By: David Pierce
Acting Ut' ities Director Reclamation Coordinator
SUBJECT: Exploratory Non - Potable Well at Water Reclamation Facility
RECOMMENDATION
By motion, approve plans and specifications for "Non- Potable Well at
Water Reclamation Facility, City Plan Number T -35L" and authorize
soliciting of bids and contract award by the CAO, if the lowest
responsible bid is within the Engineer's cost estimate.
DISCUSSION
This project consists of drilling three small diameter holes to
determine the most promising location for a well and then drilling an
exploratory well to test the production potential. This work needs to
be accomplished at this time to confirm the yield of the well so that
the impacts of a permanent well can be analyzed in the Water
Reclamation Project EIR. This is not a recommendation to actually
operate this well at this time. The recommendation is merely to
evaluate the potential in order to scope the project for the EIR.
Preliminary design work on the Water Reclamation Project has identified
that a significant limitation to amount of reclaimed water that can be
used for irrigation will be the amount of water that can be provided to
meet the customers peak demands. The flow through the Water
Reclamation Plant will be fairly constant during dry weather. The
number of customers that may be connected to the system will be limited
by the amount of water that can be provided to meet their peak demand
in August. If the peak supply can be increased during the month of
August, additional customers may be served and they can continue to be
served using reclaimed water only during the lower demand periods. The
additional water for peak supply can be supplied from seasonal storage
of reclaimed water or by obtaining water from another source. Seasonal
storage requires large land areas for ponds or tanks which may be
susceptible to algae and odor problems and will be very costly.
Therefore well water is proposed as a readily available cost effective
additional source.
Although well water is being drawn from the same ground water basin as
our potable water supplies, there is a net reduction in the need for
potable water for irrigation because the addition of this water during
the peak demand periods allows an increase in the use of reclaimed
water during non -peak periods. Since the main users of reclaimed water
would be using well water or potable water for irrigation if the
reclaimed water were not available this will produce a net reduction in
demand for potable water..
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COUNCIL AGENDA REPORT
Well Project T -35L
page 2
Without a well it will be possible to deliver up to 1480 acre feet of
reclaimed water per year for irrigation. Using a 200 gallon per minute
well during August, it will be possible to provide a total of 1600 acre
feet of water per year for irrigation. This will include 35 acre feet
of well water and an additional 86 acre feet of reclaimed water. This
roughly translates it; for every gallon of well water used to
supplement the program peak needs, an additional 3 gallons of reclaimed
water can be sold.
On the following graph,
the bars depict the reclaimed water available from the treatment
plant (monthly variations reflect the length of the month),
the - +- line depicts the water useful for irrigation without a
peaking well,
the - *- line depicts the water useful for irrigation with a 200
gallon per minute peaking well, and
the darkened portion of the bars depict the increase in reclaimed
water that is useful for irrigation with the peaking well.
Note that the additional water available for irrigation is
reclaimed water except for August and a portion of June.
300
250
200
a
a
L6 150
a
L
U
100
50
M
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
® Available —+— No Well A 200 gpm
WATER RECLAMATION PLANT EFFLUENT AND IRRIGATION WATER SUPPLY
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COUNCIL AGENDA REPORT
Well Project T -35L
page 3
The non - potable well can be located on City owned property, adjacent to
Interstate 101 near the ponds. This site is an excellent area for
groundwater, and due to Health Department restrictions and possible
water quality problems, is unsuitable for a potable water well.
FISCAL IMPACT
Engineer's estimate for the installation of this exploratory well is:
Drill 3 pilot holes $ 61000
Drill & test exploratory well 17,000
Contingency @ 9% 2.000
Total Engineer's estimate $25,000
A total of $2.35 million was approved for groundwater water
development, phase III (1989 -91 Financial Plan Supplement and Approved
1990 -91 Budget, page H -16).
ALTERNATIVES
1. Construction of seasonal reservoirs.
To replace a 200 gallon per minute well would require 40 acre
feet of storage.
To use all available reclaimed water for productive
irrigation would require 1300 acre feet of storage.
This alternative would require significant land for storage pond
siting and would be costly to construct and maintain. This
alternative is not recommended.
2. Limit the distribution of reclaimed water to those customers whose
needs can be fully met by available reclaimed water from the
reclamation plant. This alternative would reduce the amount of
water available for reclaimed use by approximately 120 acre
feet /year. This alternative is not recommended.
Plans and Specifications are available for review in the City Council
office.