Receive and Accept Report on Water Year 2004 Seaside Basin Injection Testing Program


Meeting Date:

December 13, 2004





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) 2004 report is the third annual report to document injection testing at the Districtís Santa Margarita Test Injection Well (SMTIW), located on the former Fort Ord adjacent to General Jim Moore Boulevard.WY 2004 marked the second season that both injection and recovery occurred at the SMTIW.Injection testing at the SMTIW began on February 6, 2004 and continued intermittently until March 29, 2004, when excess flows were no longer available for diversion from the Carmel River, as per the Districtís temporary water right permit from the State Water Resources Control Board.A total of 160 acre-feet (AF) was injected at the well during this period.This is in addition to the 345 AF that were injected during previous seasons, for a total of 505 AF injected since testing began at the SMTIW in 2001.Injection was performed at average rates ranging between 600 and 1,450 gallons per minute (gpm), which is approximately equal to 3 to 6 acre-feet per day (AFD).The well maintained injection and production capacity during the season, indicating that well plugging was minimal and was successfully managed by routine backflushing of the well between injection tests.


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 monitored wells throughout the period, even at the peak of the injection season.Recovery of water commenced on July 13, 2004, when the SMTIW was put into emergency production to replace California American Waterís (Cal-Amís) nearby Paralta well, which experienced a pump motor failure.Recovery continued at Cal-Amís request until October 26, 2004, during which 696 AF were recovered, or 430 percent of the WY 2004 injected volume.


Water quality results showed that the recovered water was a mix of native and injected water, indicating that all the injected water did not migrate away from the well during the storage period.Rather, the injected water partially filled, temporarily, the existing pumping depression in this area of the basin, and was subsequently recovered into the Cal-Am distribution system at the SMTIW and Cal-Amís existing nearby wells, or served to replenish depleted ground water storage in the basin.A copy of the Executive Summary from the draft WY 2004 report, prepared by the Districtís engineering consultant on the project, Padre Associates, Inc. (Padre), is provided as Exhibit 2-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 2004 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 2004 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 the injectate 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 350 feet east of the PRTIW.Both well locations are shown on the map in Exhibit 2-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 505 AF were injected at the SMTIW during WYs 2001 through 2004, for a total of 1,101 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 by-products 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.Accordingly, recovery testing at the SMTIW commenced on July 13, 2004 and was completed on October 26, 2004.696 AF was recovered during this period, which is about 430% of the WY 2004 injected volume.A total of 1,139 AF has been recovered during WYs 2003 and 2004.


Extensive water quality sampling was conducted during recovery operations in each of these last two seasons.Results indicate that the recovered water was a blend of Carmel River system water and native ground water, and that the recovered water retained some chemical imprints of the Carmel River system water even after 100% of the injected volume was removed.This suggests that injection is capable of ďconditioningĒ the aquifer even after more water is removed than was injected.This reduces the occurrence of hydrogen sulfide in the native ground water, representing an ancillary benefit of the ASR program in terms of reduced water treatment costs.


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 2005 season.



2-A††††† WY 2004 report, Executive Summary

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



J. Oliver, 12/13/04 staff note, 3 pages