Understanding water quality trends in the Borrego Basin is a top priority of BWD. Groundwater Quality is always a dynamic situation, especially in Borrego Springs where the impending dramatic reduction in future pumping will likely create changing conditions. Reduction in high volumes of Agricultural pumping in the future in the North part of the Basin could allow for migration of poorer water quality towards BWD Production Wells. In response to this threat, the BWD Board increased the frequency of water quality sampling over 5 years ago and have created a significant quantity of lab analyses. The BWD Board will now be considering development of a Groundwater Quality Risk Assessment Update (Assessment) to evaluate this critical data.

This proposed Assessment update will build from the 2017 Borrego Springs Subbasin Groundwater Quality Risk Assessment, 2020 Groundwater Management Plan (GMP) and ongoing water quality analyses for BWD’s Title 22 monitoring and Sustainable Groundwater Management Act (SGMA) implementation. Previous studies have investigated BWD’s potential risk associated with temporal changes in water quality that may result in exceedances of drinking water maximum contaminant levels (MCLs) in BWD production wells due to the long-standing critical overdraft of the Borrego Springs Groundwater Subbasin and the impacts of impending wide spread pumping reductions.

This Assessment will include updated analyses to support current and future water management planning decisions. Constituents of concern (COCs) identified in BWD include arsenic, fluoride, nitrate, sulfate, and total dissolved solids (TDS). At the time of the 2017 Borrego Springs Subbasin Groundwater Quality Risk Assessment ’s development, water quality data was sampled every three (3) years for select COCs, per Division of Drinking Water (DDW) requirements. Since development of the Borrego Springs Subbasin Groundwater Quality Risk Assessment, BWD and the Borrego Springs Watermaster have implemented semi-annual sampling of wells in the Borrego Springs Subbasin. This reduction in temporal data gaps has improved the quality of analyses in the Borrego Springs Subbasin.

There is no known water quality issue at any of the BWD Production Wells. Increasing our understanding of current water quality and looking at any trends is critical to locating any potential issue before it becomes a problem.

Primary deliverables will be a Technical Memorandum detailing the analyses conducted and results obtained, and a presentation to the BWD Board of the same. Recommendations for additional analysis and mitigation efforts will be included in both the technical memorandum and board presentation. The Analysis will be performed by Trey Driscoll and his team at Intera Geoscience and Engineering with completion in July.