Groundwater Protection Update

OCWD continues its longstanding efforts to see cleanup in both the North Basin and the South Basin groundwater contamination areas.

In the North Basin, work has steadily progressed toward the installation and operation of one of the most productive of the remediation wells installed, EW-1.  Pump testing and groundwater modelling have estimated that the well will produce 1,000 gallons per minute and that it will capture high concentrations of volatile organic compounds (VOCs) that are currently migrating from several upgradient sources.   This plume capture is not the definitive answer to the groundwater problem in the North Basin, but it is a significant first step toward reducing the spread of VOCs that cover an area of approximately seven square miles.

Discussions are also underway regarding the possibility of doing similar projects with the other five wells already in place.  The US Environmental Protection Agency (EPA) is now the official regulatory agency overseeing North Basin activities.  Under its direction, work will soon begin on a new phase of remedial investigation and feasibility study (RI/FS) that will include the development of a site conceptual model, the installation of additional monitoring wells, additional water quality analysis, expanded groundwater modeling and an evaluation of alternatives for the remediation of the parts of the plumes with elevated VOC concentrations.   Upon completion of the RI/FS, the EPA will select a remedy and will direct its construction and implementation.

In the South Basin, OCWD plans to work closely with the California Department of Toxic Substance Control (DTSC) and the Regional Water Quality Control Board (RWQCB) to develop a comprehensive cleanup strategy that addresses on-site and off-site groundwater contamination. While the contaminant plumes originated from individual industrial sites, in many cases they have moved off-site and comingled with plumes from other sites.  As with North Basin, most of the contaminants are VOCs.  

Critical to this approach is the coordination between the agencies with the ongoing RI/FS work that has been undertaken by OCWD over the past year.  OCWD will work with the state regulatory agencies as they review and comment on the various RI/FS documents prepared by the District.  The remedial investigation will better characterize the subsurface geology and extent of contamination in the shallow groundwater.  The RI/FS will conclude with the feasibility study that evaluates the remediation options most appropriate to remove contaminants and reduce their ability to spread and reach drinking water aquifers.

In the North Basin and South Basin areas, OCWD is taking the lead in implementing the necessary environmental studies in the interest of protecting and improving the quality of this vital groundwater resource. It is our hope that those responsible for the contamination will follow OCWD’s lead and step forward and do their part by joining in the cooperative cleanup.

Visit the OCWD website for more information about the District’s groundwater cleanup efforts.