HomeMy WebLinkAbout03/01/1994, C-8 - DESIGN FOR GROUNDWATER TREATMENT FACILITIES AT THE AUTO PARKWAY WELL. 1111111111111 `Ip�`�pIIII�I�I�I �J MEETING GATE:
II illYiX�) C,' o san suis oBispo March 1, 1994
COUNCIL AGENDA REPORT ITEM NUMBER:
FROM: John Moss, /x'11 PREPARED BY: Dan Gilmore;
Utilities Defector Utilities Engineer
SUBJECT:
Design for groundwater treatment facilities at the Auto Parkway Well.
CAO RECOMMENDATION:
By motion, approve Request for Proposals (RFP) for the design of treatment facilities for the
Auto Parkway Well and direct staff to proceed with the issuance of the RFP and evaluation of
submitted proposals. Authorize CAO to execute agreement with the successful bidder, providing
the bid is within the budget amount of $100,000.
BACKGROUND:
Basin Characteristics. The "Ground Water Basin Evaluation," dated January, 1991, was
prepared for the City of San Luis Obispo by Boyle Engineering. This in-depth study covers
many of the detailed characteristics of the ground water basin. The following summarizes the
highlights of the report.
The San Luis Obispo Ground Water Basin has been identified and defined by the California
Department of Water Resources (DWR) as Basin 3-9. The.basin covers an area of 18 square
miles and has an estimated storage of 24,000 acre-feet (af). The study estimates the annual
average recharge rate to be 3700 af. However, even after the recent drought, the basin fully
recharged following a fairly normal season of rain. The groundwater basin is an important and
reliable source of water supply for the City of San Luis Obispo.
Historic Use of Groundwater. In 1988, the City implemented a ground water development
program. Prior to that, ground water had not been used as a source of domestic supply since
the 1940's. During the recent drought, ground water accounted for up to 48% of the City's
domestic supply. In 1990 and 1991, ground water production averaged around 1950 acre feet
per year (afy). In May of 1992, the agreement to use the Dalidio Well as a domestic supply
expired, and the well was removed from municipal service. In October of 1992, the Auto
Parkway Well was taken out of service due to an elevated level of nitrate. The Calle Joaquin
(Denny's) Well was also shut down due to nitrate contamination on June 11, 1993.
Current City Policies on Groundwater. On February 24, 1987, City Council directed staff
to proceed with the development of the groundwater resource. Groundwater was identified as
a component of the City's water supply in the Draft Water Management Plan and a Major
Objective of the 1987-89 Financial Plan. On December 7, 1987, Council authorized the first
two phases of a groundwater study, conducted by John L. Wallace and Associates. On April
5, 1988, Council authorized the third phase of the study. And, on October 4, 1988, the final
two phases of the study were authorized.
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COUNCIL AGENDA REPORT
On September 3, 1991, Council adopted the concept of a "multi-source water supply" to meet
the City's water needs. Since ground water use was reestablished in 1988, ground water has
been a component of every Water Operational Plan and Financial Plan. Consistent use of the
groundwater resource is necessary to secure a future right to this water, should the basin ever
be adjudicated.
The draft Water Management Plan recommends using the groundwater resource to its full
potential. The City's Safe Annual Yield (SAY) model, adopted in September of 1992, depends
on a minimum contribution of 500 afy from groundwater.
Inventory of City Wells (potable water). The City currently relies on four domestic water
supply wells, Pacific Beach #1 and #2 on Los Osos Valley Road, the Fire Station No. 4 Well,
and the Mitchell Park Well.
Pacific Beach #1 and #2 are relatively close together and the influence they have on each other
limits their use. Continual pumping causes the water table to drop in the area of these wells to
the point where one or both wells must be throttled back or shut down completely. Operating
together, Pacific Beach #1 and 42 can produce as much as 45 of in a month. On average,
however, the two wells can be expected to produce around 25 of per month consistently. This
corresponds with an annual pumping rate of about 300 afy.
The Fire Station No. 4 Well is also very sensitive to ground water levels. The well can produce
around 12 of in a month. But, sustained pumping would only yield around 4 of per month or
48 afy.
The Mitchell Park Well is a relatively low producer, but more consistent. This well will
produce an average of about 4 of per month or 48 afy.
The Auto Parkway Well was the'City's most productive and reliable groundwater production
well. While other wells had to be shut down or throttled back during the recent drought period,
the Auto Parkway Well consistently pumped at capacity contributing nearly 1,000 acre feet per
year (afy). The Auto Parkway Well was taken out of service on October 19, 1992, after routine
sampling showed elevated levels of nitrate. Successive testing has revealed that the nitrate
problem is likely to remain for a long period of time and should be considered a permanent
situation. Any future use of the Auto Parkway Well will require a nitrate removal facility.
The Denny's Well was another consistent producer of groundwater that was lost to elevated
levels of nitrate. Though fairly close to the Auto Parkway Well, both wells can be operated
simultaneously without significantly impacting each other. Prior to being removed from service,
the Denny's Well produced around 25 of per month or 300 afy.
The City has investigated the possibility of developing new wells to expand the municipal water
supply, including the drilling and testing of a well at the Lady-Sutcliffe Cemetery. It was
determined that water quality and yield uncertainties did not warrant further investigation.
city of San LUIS OBISPO
djj% COUNCIL AGENDA REPORT
DISCUSSION:
On August 21, 1992, the City purchased a parcel of property near the Auto Parkway Well for
the purpose of relocating the existing carbon filtration tanks. When the Auto Parkway Well
tested high in nitrate, the carbon filtration tanks were dismantled and stored at the City's
Corporation Yard, pending further tests on the well. The carbon filtration tanks are still
available for removal of tetrachloroethylene (PCE) and trichloroethylene (TCE) at the Auto
Parkway Well site.
Treatment alternatives for the removal of nitrate were investigated by City staff. Several viable
treatment alternatives exist for the current situation. A Request for Proposals has been prepared
to solicit bids for the design of treatment facilities to be located at the Auto Parkway site. The
site appears adequate for the location of both the nitrate removal facilities and the carbon
filtration tanks.
CONCLUSION:
The Auto Parkway Well is the City's largest and most consistent producer of groundwater. It
is a vital part of the City's water supply resources. The 500 afy of groundwater identified in
the City's SAY model could be supplied entirely by the Auto Parkway Well. The City's other
municipal wells will also be utilized as long as they continue to produce quality water. The
costs of treatment at the Auto Parkway Well are offset by the reliability of the well and the costs
associated with procuring water from other supply sources.
FISCAL IMPACT:
A total of $250,000 was approved as a part of the 1993-94 Budget to support Groundwater
Development (1993-95 Financial Plan, page E-5). A total of $0 has been expended, to date,
leaving a balance of $250,000 available to support the recommended design project.
Development of the recommended treatment facility will be paid out of the $500,000 approved
as a part of the 1994-95 Budget for Groundwater Development.
Note: Request for Proposals is available in the Council Office for inspection.
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