San Gabriel Valley (area 4) City Of Industry, Puente Valley

Investigation and Cleanup Activities

The cleanup approach is groundwater extraction and treatment at the western end of the Puente Valley. Two separate projects are planned, known as the shallow zone and intermediate zone remedies.

The shallow zone remedy will include ten extraction wells capable of pumping approximately 2.0 million gallons per day (MGD). The project will include granular activated carbon water treatment equipment (for removal of VOCs), advanced oxidation equipment (for removal of 1,4-dioxane) and, ion exchange equipment (for removal of perchlorate).

The treated water from the shallow zone remedy was to be originally discharged to a local flood control channel. In light of new environmental concerns, EPA is re-evaluating this discharge option.

The intermediate zone remedy will include six extraction wells capable of pumping approximately 1.5 MGD. The project will include granular activated carbon water treatment equipment for removal of VOCs and, if necessary, advanced oxidation (for removal of 1,4-dioxane) and ion exchange (for removal of perchlorate). Treated groundwater is anticipated to be provided to a local water supply distribution system. During low demand winter months portion of the treated water may need to be discharged to San Jose Creek.

Site Studies

Area-wide Contamination: In 1984, the EPA began a study of the nature and extent of contamination throughout the San Gabriel Valley. The intent of this investigation is to identify specific areas of the site for focused study and provide support to ongoing activities at all areas of the San Gabriel Valley site.

Site Studies

Puente Valley Area: Potentially responsible parties, under EPA oversight, investigated the nature and extent of contamination at the Puente Valley area. This phase of the project, commonly referred to as the Remedial Investigation/Feasibility Study (RI/FS) was completed in June 1996.

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 sources of contaminants. To date, nearly 400 individual facilities throughout the San Gabriel Valley have been confirmed as having soil contamination.

Remedy Selected

The selected remedy for the PVOU includes extraction, containment and treatment of contaminated groundwater in the shallow and intermediate zones at the mouth of Puente Valley. The remedy also includes a set of wells for monitoring the groundwater in the shallow, intermediate, and deep zones at mid-valley and the mouth of the valley, to ensure that the remedy meets the performance criteria set in the September 1998 Record of Decision (ROD) and updated in the 2005 Explanation of Significant Differences (ESD) which included the contaminants 1,4-dioxane and perchlorate.. Cost estimates for the remedy assume that additional extraction and treatment systems will be needed for both the intermediate and shallow zones. The estimate also assumes that the treatment technology will be air stripping and adsorption of VOCs in the off-gas. The net worth of this interim remedy, at the time of the ESD, was approximately $51 million.
This remedy specifies criteria that the treatment system must meet while providing flexibility in implementing the system. For example, in the intermediate zone at the mouth of the valley, the ROD provides the option to either install a series of extraction wells or use an existing well-field extraction system, as long as the following performance criteria is met: "the remedial action shall provide sufficient hydraulic control, through groundwater extraction, to capture groundwater contaminated with VOCs above MCLs [Maximum Contaminant Levels allowed by State law], and prevent it from migrating into or beyond the B7 well field area (depending on the location of extraction)." The shallow zone remedy must comply with the following performance criteria: "the remedial action shall apply measures necessary to prevent further migration of groundwater in the shallow zone with VOCs above 10 times MCLs from migrating beyond its current lateral and vertical extent."

Extracted groundwater will be treated to remove VOCs before it is discharged. EPA is evaluating discharge options in light of potential environmental concerns regarding discharge to surface water.

Remedy Design

The Remedial Investigation and Feasibility Study was completed in May 1997 and a cleanup plan adopted in September 1998 (the Puente Valley Operable Unit Interim Record of Decision). In September 2001, after negotiations failed, EPA ordered Carrier Corporation to design, build, and operate the shallow zone remedy. In March 2002, EPA issued a second order to TRW Inc. to design, build, and operate the intermediate zone remedy. TRW is now known as Northrop Grumman Space and Mission Systems Corporation (Northrop Grumman)). In June 2005, EPA issued an Explanation of Significant Differences (ESD) to update the 1998 cleanup plan by requiring additional treatment for 1,4-dioxane and possibly perchlorate. The Record of Decision is available on EPA’s website as part of the site overview for the San Gabriel Valley Area 4 Superfund Site.


In August 2005, EPA and the Department of Justice reached an agreement requiring United Technologies Corporation (UTC) and its subsidiary Carrier Corporation to implement the shallow zone remedy. Significant work is underway. The Consent Decree also requires Carrier Corp. to carry out an environmental project at a former duck farm overlying a portion of the contaminated groundwater. The Watershed Conservation Authority purchased the former duck farm and plans to use it for the benefit of the local community.

EPA is currently working with Northrop Grumman, who is implementing the Intermediate Zone remedial system to convert the existing Unilateral Administrative Order to a Consent Decree

With work underway in both the shallow and intermediate zones, EPA is continuing to negotiate settlement agreements with remaining parties. Two settlements together worth approximately $10.6 million have been negotiated so far and numerous others are in progress.