Rainbow MWD approves consultant contract for San Luis Rey groundwater study

The Rainbow Municipal Water District approved a consultant contract to study the amount of groundwater available to the district from the San Luis Rey Basin.

The Rainbow board voted 5-0 November 19 to award a professional services contract to West Yost for an amount not to exceed $399,352.

“Local water supply has been studied for many years, and we believe this study will confirm the availability of local supplies for the district,” said Rainbow general manager Brian Brady.

Currently Rainbow relies on imported water for the entirety of its water supply. The development of local supplies would provide the district with some autonomy over water supply decisions and could also provide water at a lower cost than the San Diego County Water Authority charges for imported water.

The development of supplies in addition to SDCWA purchases would increase Rainbow’s supply reliability while also helping to mitigate the price increases for imported water. Earlier this year Rainbow staff completed an alternative water source feasibility study which evaluated various alternatives for the district to develop additional water supplies. The feasibility study caused district staff to determine that the top two priorities for the district to pursue would be evaluating groundwater supply development in the San Luis Rey Basin and evaluating development of recycled water service in conjunction with the Valley Center Municipal Water District and/or the Fallbrook Public Utility District.

Rainbow’s territory overlays sub-basins of the Santa Margarita Basin and the San Luis Rey Basin. Rainbow does not have groundwater rights in either basin, but the district has a right to utilized recaptured return flows from imported water the district provided to customers. The feasibility study indicated that up to 2,900 acre-feet per year of additional groundwater supplies could be developed; that amount does not include any additional contribution from FPUD imported water flows if Rainbow and FPUD collaborate.

Utilizing the return flows requires hydrological studies which demonstrate that the return flows are being conveyed to the location where the groundwater pumping would occur. The studies must also determine the level of water treatment and associated cost for any groundwater developed from the return flows. District staff developed a request for proposals for a consultant with expertise in hydrology, water rights, and groundwater treatment to assist the district.

Five firms responded to the request for proposals. Rainbow staff reviewed and ranked the proposals and conducted interviews with two finalists before determining that West Yost was the most qualified firm based on the content of the proposals and the interviews.

West Yost will assist the district in evaluating the hydrology of the San Luis Rey Basin to determine the amount of imported water return flows which could be developed based on alternative groundwater well field locations, identifying any water rights permitting requirements and assisting with submission of any needed applications, assisting with water quality and feasibility analyses of groundwater treatment plant requirements, and developing a footprint along with estimated capital, operations, and maintenance costs for the associated treatment facilities, wells, and conveyance facilities.

“It will help to confirm local water supplies for the district,” Brady said.

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