SAN GABRIEL VALLEY (AREA 1)
EL MONTE, CA
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The San Gabriel Valley (Area 1) site is a 11-square-mile area of contaminated groundwater in Los Angeles, California. It is one of four Superfund sites in the 170-square-mile San Gabriel Valley. Multiple potentially responsible parties (PRPs) contaminated over 30 square miles of groundwater under the Valley with volatile organic compounds (VOCs) and industrial solvents. About 400 facilities in the region have soil contamination. Cleanup, operation and maintenance activities, and monitoring are ongoing.
What Has Been Done to Clean Up the Site?
The site is being addressed through federal, state and local actions.
EPA conducted two five-year reviews of the Whittier Narrows and South El Monte OU’s interim remedies. These reviews ensure that the interim remedies put in place protect public health and the environment, and functions as intended by site decision documents. The most recent review concluded that response actions at the two OUs for groundwater are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment in the short term. Continued protectiveness of the remedy requires evaluation of the monitoring well and pumping well programs.
For the vapor intrusion pathway at the South El Monte OU, the five-year review concluded that EPA could not make a protectiveness determination until it performed further assessment. EPA is working to characterize the site for vapor intrusion and will address the findings from the characterization studies by selecting a final remedy for this pathway.
EPA conducted one five-year review of the remedies at the Richwood and Suburban OUs. Both of these remedies were found to continue to be protective, and work at these OUs is complete.
EPA oversees the operation of four treatment plants that contain and treat contaminated groundwater in the El Monte OU. The shallow groundwater contamination is treated to remove contamination and either reinject to groundwater or discharge accordingly. The shallow groundwater extraction well network is currently being optimized by the West Side parties. Deep groundwater is treated to meet all drinking water standards and is supplied within the San Gabriel Valley. Currenly, all drinking water provided meets all Federal and State drinking water standards.
EPA has negotiated multiple consent decrees with potentially responsive parties (PRPs) to help clean up the site. The South El Monte OU has 9 consent decrees worth over $25 million that partially fund the implementation of the interim remedy by EPA through a Cooperative Agreement. The El Monte OU has two PRP groups that are actively implementing the remedy on the East and West side.