STATE WATER RESOURCES CONTROL BOARD DRAFT REVIEW OF CALIFORNIA AMERICAN WATER COMPANY’S MONTEREY PENINSULA WATER SUPPLY PROJECT

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ABSTRACT: The STATE WATER RESOURCES CONTROL BOARD DRAFT REVIEW OF CALIFORNIA AMERICAN WATER COMPANY’S MONTEREY PENINSULA WATER SUPPLY PROJECT draft document is embedded. Importantly, the Conclusion states, in part, as follows: 

“If no injury results–this would have to be shown through modeling, mitigation, project design or other means–Cal-Am could legally pump from the Basin by developing a new water supply through desalination that produces water that is surplus to the existing supply. If Cal-Am’s extractions are limited to water derived from brackish or saline sources or areas of the Basin, and it returns all incidental fresh water to the Basin in a method that avoids injury to other users, the MPWSP could proceed without violating other users’ groundwater rights.” 
The Conclusion and Recommendations text sections are reproduced.

Swrcb Mpwsp Draft Report 12-21-12

STATE WATER RESOUCES CONTROL BOARD DRAFT REVIEW OF CALIFORNIA AMERICAN WATER COMPANY’S MONTEREY PENINSULA WATER SUPPLY PROJECT

10. Conclusion:

The key determination in whether Cal-Am may extract water from beneath the Salinas Basin is whether injury will result to other users or the Basin. If the MPWSP is constructed as described in the FEIR for the North Marina Project the slant wells would pump from the unconfined dune sand aquifer. If groundwater is pumped from an unconfined aquifer and the modeling assumptions in the FEIR for the North Marina Project are accurate, then there will be lowering of groundwater levels within an approximate 2-mile radius. Since seawater intrusion occurs in this area, this water developed through desalination is likely “surplus” to the needs of other users in the Basin. Based on the information available, it is unlikely any injury would occur by the lowering of the groundwater levels in this region. Nevertheless, Cal-Am would be required to show there was no injury and that any fresh water it extracts is returned to the Basin.

Modeling for the North Marina Project does not predict that Basin users’ fresh water supplies would be affected if its wells pump from an unconfined aquifer, which we assume to also be true for the MPWSP. If however, further exploratory testing shows water is removed from a confined aquifer, water levels would be lowered in a larger inland area and the effect on groundwater flow direction would be greater. Since the pumping from a confined condition would affect a much larger area, there would be a greater likelihood of the MPWSP extracting fresh water from the Basin thereby causing impacts to other users in the Basin that would require additional mitigation measures to avoid injury to affected users.

If no injury results–this would have to be shown through modeling, mitigation, project design or other means–Cal-Am could legally pump from the Basin by developing a new water supply through desalination that produces water that is surplus to the existing supply. If Cal-Am’s extractions are limited to water derived from brackish or saline sources or areas of the Basin, and it returns all incidental fresh water to the Basin in a method that avoids injury to other users, the MPWSP could proceed without violating other users’ groundwater rights.

A physical solution could be implemented to ensure that all rights are protected while maximizing the beneficial uses of the Basin’s waters.36 Such an approach is consistent with the general policy stated in the California Constitution article X section 2, and by a long history of case law that has provided guidance on the solutions that can be developed to address complex groundwater issues in regions where supply is constrained. The ongoing development of unique solutions tailored to the specific conditions that apply to a given groundwater basin, reflects the understanding that waters in California are too valuable not to be utilized to the maximum extent possible if beneficial uses and other legal users’ rights are maintained.

11. Recommendations

Additional information is needed to accurately determine MPWSP impacts on current and future Basin conditions. First, specific information is needed on the depth of the wells and aquifer that water will be extracted from. Studies are needed to determine the extent of the dune sand aquifer, the water quality and quantity of the dune sand aquifer, the extent and thickness of the SVA and the extent of the 180-Foot Aquifer.

Second, the effects of the MPWSP on the Basin need to be evaluated. A series of test boring/wells would be needed to assess the hydrogeologic conditions at the site. Aquifer testing would be needed to determine the pumping effects on both the dune sand aquifer and the underlying 180-Foot Aquifer. Aquifer tests should mimic proposed pumping rates.

Third, a groundwater model will be needed to predict future impacts from the MPWSP. Modeling scenarios will need to be run to predict changes in groundwater levels, groundwater flow direction, and changes in the extent and boundary of the seawater intrusion front. Additional studies will be necessary to determine how any extracted fresh water is replaced, whether through re-injection wells, percolation basins, or through existing recharge programs. The studies will form the basis for a plan that avoids injury to other groundwater users and protects beneficial uses in the Basin.