El Monte Operable Unit


The El Monte Operable Unit (EMOU) investigation phase has been completed and the remedial objectives have been specified in an United States Environmental Protection Agency’s Interim Record of Decision. This operable unit is generally characterized by volatile organic compound (VOC) contamination in the shallow zone that is mostly contained in the upper 100 feet of the aquifer. Limited amounts of VOC contamination have migrated into the deeper drinking water supplies and the recent discovery of perchlorate in monitoring wells and production wells threatens to complicate cleanup efforts further.

Responsibility for implementing the remedy has been divided into two separate groups of Potentially Responsible Parties. Each side has its own remedies to construct. The San Gabriel Basin Water Quality Authority has funded early actions in the past and continues to work with the Environmental Protection Agency, water purveyors and PRPs to facilitate the EMOU cleanup.

Currenlty, WQA is a co-lead agency with the City of El Monte for the EMOU East Side Interim Remedial Action Eastside Shallow Zone and Southern Deep Zone Remedy.

For additional information, please see Appendix A in WQA’s Groundwater Quality Management and Remediation Plan (406 Plan).