Rainbow hears about alternative water sources

The Rainbow Municipal Water District board heard a presentation on options for the district to diversify its water portfolio.

The presentation was not a voting item at the board’s May 28 meeting. “The principal recommendation was that we pursue groundwater resources,” said Rainbow general manager Brian Brady.

Rainbow staff completed an alternative water source feasibility study which evaluated various alternatives for the district to develop additional water supplies. The Rainbow district currently receives 100 percent of its water from the San Diego County Water Authority, and the development of additional supplies would increase Rainbow’s water supply reliability while also helping to mitigate the price increases for imported water.

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.

The Rainbow district territory overlays sub-basins of the Santa Margarita Basin and the San Luis Rey Basin. Rainbow lacks groundwater rights in either basin, but the district has a right to utilize 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. Brady is also FPUD’s general manager.

Utilizing the return flows would require hydrological studies which demonstrate that the return flows are being conveyed to the location where the groundwater pumping would occur. Studies must also determine the level of water treatment and associated cost for any groundwater developed from the return flows. District staff will develop a request for proposals to hire a consultant with expertise in hydrology, water rights, and groundwater treatment to assist the district. Board approval would be needed for an actual consultant contract.

The consultant would assist the district in evaluating the hydrology of the San Luis Rey Basin to determine the amount of imported water return flows which would 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.

Recycled water is typically sold at 15 to 20 percent less than imported water, and recycling water will also reduce sewage conveyance and treatment costs. Rainbow currently pays the City of Oceanside approximately $1,100 per acre-foot of effluent, which along with new revenue from recycled water sales at approximately $1,100 per acre-foot could be used as funding to develop recycled supplies.

Rainbow’s staff recommended that the next future board action regarding evaluation of recycled water should be pursuing the development of a joint study with the Valley Center Municipal Water District and the Fallbrook Public Utility District. FPUD has excess recycled water available as well as outfall and recycled treatment capacity, Rainbow has wastewater treatment capacity in San Luis Rey and large agricultural customers who could benefit from discounted recycled water, and Valley Center has a secondary effluent near Rainbow’s agricultural customer base and new developments which have requirements to build treatment plants.