Los Osos Basin Management Committee Los Osos Creek Groundwater Recharge Study

Los Osos, CA

The community of Los Osos/Baywood Park relies solely on groundwater for municipal water supply. Three water purveyors pump, treat, and distribute potable water within the community. Additionally, private wells outside of the three service areas draw from the local groundwater basin for various potable and non-potable uses, including a significant use for agricultural irrigation in the Los Osos Valley. A Basin Management Committee was formed after groundwater adjudication proceedings to protect and sustainably manage the local groundwater basin. In 2017, San Luis Obispo County completed construction of the Los Osos Wastewater Project, including a community sewer collection system and the Water Recycling Facility (WRF). The majority of the community, which previously utilized septic systems, was connected to the WRF for centralized treatment. The WRF produces tertiary disinfected recycled water that can be used for urban and/or agricultural irrigation. The County and the Basin Management Committee has long been investigating ways to best utilize the recycled water as a community resource to offset potable water use.


The Basin Management Committee (BMC) hired MKN to prepare a Feasibility Study to investigate permitting and technical feasibility of discharging recycled water from the Los Osos WRF to the nearby Los Osos Creek. MKN’s Creek Discharge Study included review of environmental and permitting issues; review of regulatory requirements and consultation with RWQCB and Department of Drinking Water (DDW) staff; and development of discharge scenarios, preliminary infrastructure requirements and relative planning-level cost opinions for comparison of alternatives. The Study concluded that the discharge will likely be considered a Groundwater Replenishment Reuse Project (GRRP), as defined by the State Water Resources Control Board DDW. MKN performed a cost-benefit analysis for the project alternatives and provided recommendations for the next steps, should the project be pursued. The BMC subsequently hired MKN to prepare a Work Plan for the next steps. The Work Plan included a summary of the next steps and a recommended budget and schedule.

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