San Gabriel Valley (area 1) El Monte, South El Monte, Whittier Narrows

Investigation and Cleanup Activities

This site is being addressed in five long-term remedial phases focusing on cleanup of area-wide contamination, the Whittier Narrows area, the Suburban Water System's Bartolo Well Fields, the Richwood Mutual Water Company area, the El Monte Area, the South El Monte Area, and identification and cleanup of the source of contamination.

Site Studies

Area-wide Contamination: In 1984, the EPA began a study into the nature and extent of contamination throughout the four San Gabriel Valley sites. The intent of the investigation is to identify areas of the site for focused study and provide support to ongoing cleanup efforts. This study is expected to continue through late 1997.

Remedy Selected

Whittier Narrows Area: In 1987, the EPA began a study of the nature and extent of contamination in the Whittier-Narrows area of the San Gabriel Valley. The investigation led to a decision in 1993 that no immediate action was needed but that monitoring would continue. Since 1996 contaminant levels had increased significantly. EPA evaluated new alternatives to control the migration of the contaminated groundwater, and in 1999 issued a Record of Decision Amendment calling for extraction and treatment of groundwater from extraction wells just north of the Whittier Narrows Dam.

Remedy Selected

Suburban Water Systems: Bartolo Well Field: Design of the potential cleanup activities was completed in 1991. However, groundwater contamination levels at the Bartolo Well Field and throughout the area adjacent to and upgradient from the wells dropped and now meet federal drinking water standards. Therefore, the remedy was amended in the fall of 1993 to include monitoring only, with a contingency plan to treat groundwater should contaminant levels again exceed federal drinking water standards.

Cleanup Ongoing

Richwood Mutual Water Company: In 1992, the EPA installed a water treatment system to provide clean water to the Richwood Mutual Water Company. In 1993, responsibility for operating the plant was transferred from the EPA to the California State Department of Toxic Substances.

Remedy Selected

El Monte : In March 1995, an agreement was reached between U.S. EPA and 15 Potentially Responsible Parties (PRPs). In the agreement, the PRPs have committed to complete the regional investigation of the area which was completed in early 1998. A cleanup plan was proposed in late 1998. An Interim Record of Decision was signed in June 1999. An Explanation of Significant Differences was signed in 2002 which incorporated treatment for emergent chemicals in the area.

Remedy Selected

South El Monte : Regional Investigation of the area was completed in late 1998 under an agreement between U.S. EPA and one of the Potentially Responsible Parties. A cleanup plan is to be proposed in mid 1999. An Interim Record of Decision (ROD) was signed in September 2000. An ESD was issued in 2005 to address the treatment of emerging chemicals.

Site Studies

Source Identification and Control: The California Regional Water Quality Control Board, Los Angeles Region, working under a Cooperative Agreement with the EPA, is identifying the sources of contamination. To date, nearly 400 individual facilities have been confirmed as having soil contamination.

Cleanup Ongoing

Whittier Narrows OU: The 1999 ROD Amendment selected groundwater extraction and treatment as the remedy. EPA started construction of the Whittier Narrows Groundwater Extraction and Treatment Facility in June 2001 and completed construction in March 2002. The facility consists of seven groundwater extraction wells, conveyance pipelines, and 20 pairs of granular activated carbon (GAC) filter vessels for removal of VOCs. EPA has entered into an agreement with the City of Whittier to operate and maintain the treatment facility and to supply treated water to local businesses and residents. EPA conducted the first Five-Year Review for the remedy in September 2006 and is currently implementing recommendations from the report.