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Pacific Southwest, Region 9: Superfund

Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations

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

EPA #: CAD980817985

State: California(CA)

County: Los Angeles

City: Los Angeles

Congressional District: 38

Other Names:

Bulletin Board

On 10/13/17, this website will no longer be updated. Site information will be migrated to the new web page at: http://www.epa.gov/superfund/sangabrielpuentevalley .
EPA appreciates your patience through this transition. If you have questions, please contact EPA staff listed below.


Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 09/08/83

Final Date: 05/08/84

Deleted Date:

The San Gabriel Valley Area 4 site is an area of contaminated groundwater that runs along San Jose Creek in La Puente. This site is one of four Superfund sites located in the 170-square-mile San Gabriel Valley. More than 30 square miles of groundwater under the Valley may be contaminated. The sites include four large areas of groundwater contamination that underlie significant portions of the Cities of Alhambra, Arcadia, Azusa, Baldwin Park, Industry, El Monte, La Puente, Monrovia, Rosemead, South El Monte, West Covina, and other areas of the San Gabriel Valley. Contamination of the groundwater by volatile organic compounds (VOCs) was first detected in 1979 when Aerojet Electrosystems in Azusa sampled nearby wells in the Valley County Water District. Following this discovery, the California Department of Health Services (CDHS) initiated a well sampling program to assess the extent of contamination. By 1984, 59 wells were found to be contaminated with VOCs. The basin's groundwater provides approximately 85 percent of the domestic water supply for more than 1,000,000 people who live in the Valley. Water supply wells are used in the basin to extract groundwater for industrial, business, agricultural, and domestic uses. Water utilities in the area provide clean water that meets all state drinking water standards.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Soil and Sludges

Groundwater and soil are contaminated with various VOCs. The primary VOC contaminants are trichloroethylene (TCE), perchloroethylene (PCE), and 1,4-dioxane. Low levels of perchlorate have also been detected. People who inhale vapors from groundwater that contain VOCs could be exposed to hazardous substances. Currently, all drinking water provided meets Federal and State drinking water standards.

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Who is Involved

This site is being addressed through Federal and State actions.

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Investigation and Cleanup Activities

The cleanup approach is groundwater extraction and treatment at the western end of the Puente Valley. Three separate projects are planned to address and contain contaminated groundwater. These are known as the Shallow Zone North, Shallow Zone South and Intermediate Zone remedies.

The Shallow Zone North and Shallow Zone South remedies will include 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 design of the SZ South system is currently underway and may be completed in early 2018.

The treated water from the Shallow Zone North 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 Remedial Design Investigation (or RDI) for the Shallow Zone South remedy was completed in Summer 2015.

The Intermediate Zone remedy may include up to eight extraction wells capable of pumping approximately 1.5 MGD. The project will include granular activated carbon water treatment equipment for removal of VOCs and advanced oxidation (for removal of 1,4-dioxane) ion exchange (for removal of perchlorate) and reverse osmosis to reduce inorganic constituents. Treated groundwater is anticipated to be provided to a local water supply distribution system.

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 was 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.

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.

Source Identification and Control: The California Regional Water Quality Control Board, Los Angeles Region, working under a Cooperative Agreement with the EPA, has identified sources of contaminants. To date, nearly 400 individual facilities throughout the San Gabriel Valley have been confirmed as having soil contamination and / or groundwater 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. For example, in the intermediate zone at the mouth of the valley, a series of extraction wells must meet the following objectives: "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 remedies 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 and other constituents 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. (now, Northrop Grumman Systems Corporation [Northrop Grumman]) to design, build, and operate the intermediate zone remedy. 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 North remedy. The Consent Decree also required 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 planned to use it for the benefit of the local community. The environment project was completed in September 2014.

In August 2009, EPA and the Department of Justice reached an agreement with Northrop Grumman Corp. to implement the Intermediate Zone remedy in the form of a Consent Decree. In September 2011, EPA issued an order to Northrop Grumman to investigate, design, build, and operate the Shallow Zone South Remedy after lead agency oversight was transferred from the Los Angeles Regional Water Quality Control Board for work related to the former Benchmark Technology facility located in the City of Industry.

Cleanup Ongoing

EPA completed its Second Five-Year Review Report for the site in 2016, and concluded that in order for the remedy to be protective in the long-term, the following actions are required:
(1) Design, construct, and operate groundwater remedial systems to meet RAOs;
(2) Evaluate vapor intrusion pathways for residential buildings located near the former TRW Benchmark facility;
(3) Revise the Sampling and Analysis Plan to include groundwater monitoring of production wells impacted by Site-related
groundwater contamination, including, SWS 147W3;
4) Install additional monitoring wells to better define the extent of groundwater contamination in the shallow zone and intermediate zone;
(5) Properly destroy any inactive water production well(s) providing a vertical conduit for Site-related groundwater
contamination migration; and,
(6) Evaluate detections of hexavalent chromium relative to remedial action objectives to prevent exposure of the public to contaminated groundwater i.e., protection of production wells, and to reduce the impact of continued contaminant migration on water supply wells.

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Cleanup Results to Date

EPA continues to oversee installation of wells, pipelines, and other remedial activities in the City of La Puente, City of Industry and unincorporated areas of Los Angeles County. These structures are part of a groundwater cleanup project called the “San Gabriel Valley Superfund Site, Puente Valley Operable Unit” (PVOU). The goal of the project is to protect drinking water. The cleanup system consists of three major parts: the “Intermediate Zone (or IZ) remedy”, the “Shallow Zone North (or SZ North) remedy”, and the “Shallow Zone South (or SZ South) remedy”. Northrop Grumman Corp. is responsible for the IZ and SZ South cleanup systems. Northrop Grumman has partially completed installation of extraction wells and pipelines for the IZ Remedy and construction of the water treatment plant is expected in spring 2018. United Technology Corporation/Carrier has completed installation of extraction wells and is conducting additional field activities for the SZ North. Northrop Grumman Corp. has currently completed field investigations for the SZ South and is now in remedial design. Pipeline installation and construction of the SZ treatment plant system will begin as soon as designs are completed.

EPA thanks residents, business owners, and local governments for their cooperation an patience during site investigation and monitoring well installations. We are currently re-evaluating and expect to finalize all Remedial Designs related to the interim groundwater remedy in light of new environmental concerns by Fall 2017. We expect to complete all construction for the project by 2018. Once constructed, the three groundwater cleanup systems may operate for approximately 15 to 30 years.

EPA and the companies have notified local residents and businesses of work through fact sheets and in flyers. EPA also hosted community meetings in La Puente to describe pipeline and other construction activities.

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Potentially Responsible Parties

Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.

(366 Kb, PDF format, requires Adobe Acrobat reader)

PVOU PRP List for 1993, 1997, 1999, 2000.pdf

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Documents and Reports

Hide details for Administrative RecordsAdministrative Records
Puente Valley Operable Unit
Puente Valley OU Remedial AR, Update #4
Puente Valley OU, Administrative Order for Access
Puente Valley OU/ Supplement #3
Hide details for Fact SheetsFact Sheets
01/01/98San Gabriel Valley Superfund Site, Area 4 - Puente Valley Operable Unit Proposed Plan
02/01/06EPA to Oversee Field Work to Install Groundwater Cleanup System in the Puente Valley Area
07/01/09EPA to Install Pipeline & Treatment System for Groundwater Cleanup Program / EPA instalará tubería y un sistema de tratamiento para el programa de la limpieza de la agua subterránea
12/20/11Progress Report on San Gabriel Valley Ground Water Cleanup
10/02/12EPA to Install Groundwater Monitoring Wells and Conduct Additional Site Investigation i the La Puente Area / La EPA instalará pozos de monitoreo de agua subetrránea y llevará a cabo investigaciones addicionales
01/01/14Progress Report on San Gabriel Valley Ground Water Cleanup (English, Spanish, Chinese, Vietnamese)
02/01/15Indoor air sampling in the South El Monte area (English, Vietnamese, Chinese, Spanish)
07/01/16Installation of Groundwater Conveyance Pipeline in Your Area (English, Spanish)
05/01/17Cleanup of the Valley’s Soil and Groundwater Continues (English, Chinese, Spanish, Vietnamese)
06/05/17Installation of Groundwater Pipeline in Your Area (English, Spanish)
Hide details for MapsMaps
08/01/13Draft Intermediate Zone VOC Plume Map - August 2013 Sampling Results
12/10/13Draft Shallow Zone VOC Plume - Puente Valley Operable Unit
Hide details for Records of DecisionRecords of Decision
09/01/98Puente Valley Operable Unit, Interim Record of Decision, Volume 1, September 1998
06/14/05Explanation Of Significant Differences ToThe 1998 Interim Record Of Decision Puente Valley Operable Unit
Hide details for Technical DocumentsTechnical Documents
10/01/08Community Involvement Plan San Gabriel Valley Superfund Site Area 4 - Puente Valley Operable Unit
03/02/11First Five Year Review Report
11/12/14Intermediate Zone - 2014 Annual Comprehensive Groundwater Monitoring Report (excluding Appendices)
11/13/14Shallow Zone South - 2014 Annual Comprehensive Groundwater Monitoring Report (excluding Appendices)
12/04/14Shallow Zone North - 2014 Annual Comprehensive Groundwater Monitoring Report (excluding Appendices)
09/29/16Second Five-Year Review Report

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Community Involvement

Public Meetings:

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Public Information Repositories

The public information repositories for the site are at the following locations:

Hacienda Heights Public Library
16010 La Monde Street,
Hacienda Heights, CA 91745
(626) 968-9356

La Puente Public Library
15920 E. Central Avenue
La Puente, CA 91744
(626) 968-4613

West Covina Library
1801 West Covina Parkway
West Covina, CA 91790
(626) 962-3541

The most complete collection of documents is the official EPA site file, maintained at the following location:

Superfund Records Center

Mail Stop SFD-7C

95 Hawthorne Street, Room 403

San Francisco, CA 94105

(415) 820-4700

Enter main lobby of 75 Hawthorne street, go to 4th floor of South Wing Annex.

Additional Links

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EPA Site Manager
Raymond Chavira
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Viola Cooper
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
State Contact
Deena Stanley
California Department of Toxic Substances Control
8800 Cal Center Drive
Sacramento, CA 95826
PRP Contact

Amy Sullivan
(Intermediate Zone Remedy
Shallow Zone South Remedy and Benchmark Source Area)

Bradley A. Barquest
(Shallow Zone North Remedy)





Northrop Grumman Corp.
2989 Fairview Park Drive
Falls Church, VA 22142

United Technologies / Carrier,
9716 Avocet Street NW,
Coon Rapids, MN 55433
Community Contact
Other Contacts
After Hours (Emergency Response)
(800) 424-8802

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