Receive and File Water Year 2005 Seaside Basin Aquifer Storage and Recovery Summary Report


Meeting Date:

December 12, 2005





David A. Berger,




General Manager

Line Item No.:


Prepared By:

Joe Oliver

Cost Estimate:



General Counsel Approval:N/A

Committee Recommendation: N/A

CEQA Compliance:N/A


SUMMARY:The Water Year (WY) 2005 report is the fourth annual report to document injection testing at the Districtís Santa Margarita Test Injection Well (SMTIW), located on the former Fort Ord Military Base adjacent to General Jim Moore Boulevard.Injection testing at the SMTIW began on January 4, 2005 and continued until March 29, 2005, when the diversion limit specified in the Districtís temporary water right permit from the State Water Resources Control Board was reached.A total of 351 acre-feet (AF) was injected at the well during this period.This is in addition to the 505 AF that were injected during previous seasons, for a total of 856 AF injected since testing began at the SMTIW in 2001.Injection was performed at average rates ranging between about 975 and 1,160 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 seven monitor well locations in the vicinity of the SMTIW.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.


The water quality investigation during WY 2005 included the performance of dechlorination (i.e., the removal of free chlorine residual) of the injection water prior to injection.The purpose of this component of the testing program was to investigate the effects of dechlorination on the formation and degradation of disinfection byproducts in the aquifer system.No water was recovered from the SMTIW for delivery to the Cal-Am distribution system in WY 2005, pending an amendment of Cal-Amís water system permit with the California Department of Health Services.A copy of the Executive Summary from the draft WY 2005 report, prepared by the Districtís engineering consultant on the project, Padre Associates, Inc. (Padre), is provided as Exhibit 3-A.Copies of the draft report have been distributed to Board members and Cal-Am under separate cover, and an additional copy is available at the District office for public review.


RECOMMENDATION:The Board should receive the draft report of the WY 2005 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 2005 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, known as the Santa Margarita Test Injection Well (SMTIW) in 2001 on the former Fort Ord Military Reservation, approximately 300 feet east of the PRTIW.Both well locations are shown on the map in Exhibit 3-B.The SMTIW 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 856 AF were injected at the SMTIW during WYs 2001 through 2005, for a total of 1,452 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.


The SMTIW was drilled in April 2001, in time to conduct only preliminary injection testing before the close of the WY 2001 season.The most significant outcome of that preliminary testing was a better understanding of the limitations of the existing Cal-Am distribution system in delivering sufficient water diverted from Carmel River sources to adequately test the performance of the SMTIW.During the remainder of 2001 and into early 2002, District staff worked with Padre and Cal-Am to design and construct significant modifications to Cal-Amís distribution system in the northeastern portion of Seaside, to facilitate the SMTIW injection testing program.


Accordingly, WY 2002 was the first season during which a significant quantity of Carmel River Basin water was injected at the SMTIW.At that time, the District worked with Cal-Am to seek approval from the California Department of Health Services (CDHS) to recover the injected water for delivery back into the Cal-Am distribution system, as a means to evaluate recovery efficiency and chemical interactions during storage.Due to concerns about the fate of disinfection byproducts in the recovered water, CDHS approval was not issued in 2002, but an interim approval was issued upon completion of additional water quality testing for a limited period in 2003.Interim approval for recovery was again issued by CDHS in 2004, concurrent with Cal-Amís request to use the SMTIW as an emergency back-up supply source.Approval for recovery testing was not granted by CDHS in WY 2005, pending a long-term agreement between the District and Cal-Am for the ASR operation.


IMPACT ON STAFF/RESOURCES:A significant staff effort has been expended planning, coordinating, and overseeing work on the Districtís injection/recovery project in the Seaside Basin.It is planned to continue this level of effort during the WY 2006 season.



3-A††††† WY 2005 draft report, Executive Summary

3-B††††† Regional Location Map, showing ASR well locations



J. Oliver, 12/12/05 staff note, 3 pages