San Dieguito Groundwater Study

About the Study
Project Importance
About the Potential Project
Cost
Public Meetings
Next Steps
For More Information

About the Study

OMWD is studying the possibility of developing a local water supply by desalinating groundwater in the San Dieguito Valley. This exploration has been funded by grants from the US Bureau of Reclamation, California Department of Water Resources, and Metropolitan Water District of Southern California. View our initial Feasibility Study (28 MB) and Appendices (75 MB) completed in 2017.

The study is considering:

1. The amount of groundwater that could be extracted from the basin on a sustainable basis without impacting the environment or current water users
2. Groundwater quality
3. Methods of groundwater treatment
4. Identification of adequate land for the wells, treatment facility, and brine disposal necessary to operate the potential project
5. Costs associated with producing the new local water supply
6. Whether the expense of producing the new water supply is cost-efficient when compared to the cost of developing other potable water supplies

Initial studies yielded positive results, and on December 12, 2018, OMWD’s Board of Directors adopted a mitigated negative declaration to support the next project phases as part of the environmental review process. A test well was then constructed in order to complete a long-term pump test to verify the basin was a viable source of groundwater that could meet the project objectives without any significant impacts to the surrounding environment. The one-year pump test was completed in late 2020, producing data that has confirmed the results of the 2017 Feasibility Study and provided positive indications that the basin can support a potential potable water supply. The results of the pilot well pump test are available for review in the Design Pilot Report. Based on these results, at its April 14, 2021 Board Meeting, OMWD’s Board approved further project studies intended to inform the decision to potentially move forward with preliminary design and an environmental impact report.
Study Area Map

Project Importance

OMWD is heavily reliant on imported water, much of which comes from far-off places like the Sacramento-San Joaquin Delta and Colorado River. The development of a local, sustainable water source like this one is becoming increasingly important as imported water costs continue to rise and water availability becomes more uncertain. Local sources also provide water supply redundancy should imported supplies be cut off.

About the Potential Project

The potential project would extract groundwater from wells located in the San Dieguito Valley Groundwater Basin and deliver it to a nearby desalination facility. Treated through reverse osmosis, a separation process that improves water quality by removing impurities such as salts, hardness, and other dissolved minerals, the water would be available for uses like drinking and fire protection.

The groundwater used to create this supply for OMWD customers would be above and beyond that already being used by existing groundwater users. In other words, customers already using groundwater through a private well would not be impacted.

Cost

Project costs will be calculated as part of the study. The project would be paid for through OMWD capital improvement funds and developer fees, as well as potential state and federal grants.

The water supply would need to be produced at a cost that is comparable to developing other local potable water supplies in order to be considered feasible. OMWD has anticipated this cost in its long-term financial planning.

Public Meetings

OMWD continues to host public outreach meetings to discuss the project with local residents and area stakeholders.

• October 17, 2017, community meeting providing a project update.
• December 4, 2018, community meeting to discuss a test well in San Dieguito Valley.
• April 27, 2021, community meeting to present findings of one-year pump test.
• September 7, 2023, community meeting providing a project update; video recording and presentation.

Next Steps

At its May 31, 2023, Special Board Meeting, OMWD’s Board approved funding of the next project steps expected to carry through 2024. The next project phases include ongoing hydrogeologic and water rights investigations, partnership explorations, alternative studies, environmental strategy support, and preliminary design work.

For More Information

For more information about the study or the potential project, please contact Joey Randall, OMWD Assistant General Manager, at 760-753-6466.

If you’d like to sign up to receive project update notifications, please email watersaver@olivenhain.com to be added to the project stakeholder list.