Challenge

The groundwater in the area of the Rialto-Colton basin has been regarded by the California Department of Drinking Water as being severely impaired. The groundwater in the basin has also historically been impacted by perchlorate and volatile organic compounds (VOC). Both of these issues have affected the City of Rialto, preventing the City from obtaining sufficient, clean water sources and leading the Regional Water Quality Control Board to require a replacement water system for the City.

Solutions

GLA was contracted by the County of San Bernardino in 1997 to assist in the evaluation of perchlorate in the basin. In response to our evaluation that found perchlorate and VOC impacts, the Solid Waste Management Division of the County contracted GLA in 2000 to assist in designing a response to the impacts to groundwater at and near the planned Unit 5 expansion area of the Mid-Valley Sanitary Landfill.

GLA’s original evaluation had led to the discovery of the Western Plume, which posed a threat to municipal production wells in the area. After contracting with the Waste Management Division, we installed 18 groundwater monitoring wells to characterize the nature and extent of perchlorate and VOC impacts to the groundwater within the Western Plume. We used these wells to develop a three-dimensional numerical groundwater model to assess plume transport and potential contaminant measures and detailed our findings in a Remedial Investigation/Feasibility Study report. This report also detailed alternative mitigation measures, concluding that impacts could best be remedied by intercepting and containing the plume, treating the collected water to potable stands, and distributing the treated water to the City of Rialto.

Our team then designed a groundwater treatment system (GWTS) at Rialto Well No. 3 based on the report. We worked closely with the County and the City of Rialto to provide all required documentation to the California Department of Drinking Water for the severely impaired groundwater, then completed all other necessary permitting for the GWTS. Once all necessary permits and regulatory documentation was submitted and approved, we proceeded with constructing the GWTS. We have continued to assist in the operation of the GWTS, which has expanded to include two more groundwater production wells, a 125,000-gallon influent reservoir, an ultra-violet treatment unit to address bacteria in the pumping wells, two ion exchange vessels, and four granular activated carbon treatment vessels.

GLA is also providing litigation support through comments to Counsel and the Solid Waste Management Division to verify that the County’s treatment responsibilities will be negatively affected by the Combined Remedy for which Emhart Industries shares responsibility for the treatment plant and responsibilities.

Results

Our work on this project has provided water to an area in critical need of reliable water resources. The City of Rialto now has a reliable source of clean water, satisfying the requirement by the Regional Water Quality Control Board. We have provided the County with an effective and cost-efficient system that has successfully cut down on the threat posed by the Western Plume.