ITEM:

CONSENT CALENDAR

 

6.

Receive and File Water Year 2006 Seaside Basin Aquifer Storage and Recovery TESTING Summary Report

 

Meeting Date:

April 16, 2007

Budgeted:

N/A

 

From:

David A. Berger,

Program/

N/A

 

General Manager

Line Item No.:

 

Prepared By:

Joe Oliver

Cost Estimate:

N/A

 

General Counsel Approval:N/A

Committee Recommendation: N/A

CEQA Compliance:N/A

 

SUMMARY:The Water Year (WY) 2006 report is the fifth annual report to document injection testing at the Districtís Santa Margarita Test Injection Well No. 1 (SMTIW No. 1), located on the former Fort Ord Military Base adjacent to General Jim Moore Boulevard.Injection testing at the SMTIW No. 1 began on January 4, 2006 and continued intermittently until May 24, 2006.A total of 411 acre-feet (AF) was diverted from sources in Carmel Valley through the California American Water (CAW) distribution system for injection testing in the Seaside Basin during this period.This is in addition to the 856 AF that were diverted for injection testing during previous seasons, for a total of 1,267 AF since testing began at the SMTIW No. 1 in 2001.Injection was performed at average rates ranging between about 980 and 1,115 gallons per minute (gpm), which is approximately equal to 4 to 5 acre-feet per day (AFD).

 

Positive response to injection was observed at the five nearby monitor well locations that provided continuous water level data during the testing.However, due to the heavy reliance on ground water pumping from this area of the Seaside Ground Water Basin, water levels remained below sea level at most of the wells monitored throughout the period, even at the peak of the injection season.

 

A copy of the draft WY 2006 report, prepared by the Districtís technical consultant on the project, Pueblo Water Resources, Inc., is provided as Exhibit 6-A.The draft report is also available at the District office for public review.

††††

RECOMMENDATION:The Board should receive the draft report of the WY 2006 testing program, and approve preparation and distribution of the final report, subject to inclusion of comments from the District or other interested parties.If this item is adopted along with the Consent Calendar, the WY 2006 report will be finalized and distributed within approximately one month.

 

BACKGROUND:The District has been studying the Aquifer Storage and Recovery (ASR) concept in the Seaside Basin since 1996.The concept entails diverting excess winter flows from the Carmel River Basin approximately six miles to the hydrologically-separate Seaside Basin, where the water is injected into specially-constructed ASR wells, for later recovery during dry periods.Prior to injection, the diverted water is treated so that it meets potable drinking water standards.†† In 1998, the District constructed a pilot injection well, known as the Paso Robles Test Injection Well (PRTIW) in the northeastern portion of the City of Seaside.The pilot well is 12 inches in diameter, 460 feet deep, and screened in the Paso Robles Formation aquifer.Injection testing during WYs 1999 and 2000 at the pilot well provided data that allowed the District to proceed with construction of a larger injection test well, now known as the SMTIW No. 1 in 2001 on the former Fort Ord Military Reservation, approximately 300 feet east of the PRTIW.The SMTIW No. 1 is 18 inches in diameter, 720 feet deep, and screened in the Santa Margarita Sandstone aquifer.Currently, testing is focused on the Santa Margarita aquifer, which has more favorable hydrogeologic characteristics, and is therefore more conducive to a full-scale ASR project in the basin.

 

Under temporary water right permits from the State Water Resources Control Board (SWRCB), 596 AF of water were injected at the PRTIW during WYs 1998 through 2002, and 1,267 AF were injected at the SMTIW No. 1 during WYs 2001 through 2006, for a total of 1,863 AF injected at both wells to date.As a result of the injection testing operations to date, much has been learned about the hydraulic response of these two target aquifer systems, as well as various operational and maintenance issues that would be attendant to a full-scale ASR project in the basin.A principal finding from this testing is that ASR wells completed in the Paso Robles aquifer, although less expensive to construct, would be limited to fairly low injection capacities of approximately 350 gpm, whereas Santa Margarita aquifer ASR wells are capable of injection capacities of at least 1,500 gpm and extraction capacities of 3,000 gpm or more.

 

Currently, work is underway on the construction and initial testing of the second ASR well at this site, SMTIW No. 2, which is being constructed as part of the Districtís Phase 1 ASR Project.No injection testing has yet been conducted at this new facility, but the District is in the planning process for conducting such testing later this year.

 

IMPACT ON STAFF/RESOURCES:A significant staff effort has been expended planning, coordinating, and overseeing work on the Districtís ASR testing program in the Seaside Basin.It is planned to continue this level of effort during the remainder of this year and into the next recharge season.

 

EXHIBITS

6-A††††† WY 2006 draft report, without appendices

 

 

J. Oliver, 4/6/2007 staff note, 2 pages

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