Jump to main content.

Perchlorate in the Pacific Southwest


On this page:
State Advisory Level
Site-Specific Information
State Links

Perchlorate has been discovered in over 350 of 6,400 public water supply wells tested in California. Contamination of groundwater and of the Colorado River affects important drinking water and irrigation water supplies. There may be over 30 sites with perchlorate in California alone. Thirteen of these are EPA Superfund sites and the state of California leads cleanup efforts at twelve other sites. The remaining sites have been identified through contaminated well data, and are the focus of a cooperative and innovative site assessment process by EPA and California. The discovery of perchlorate at sites where cleanups were already underway has both delayed those cleanups and added substantial costs over initial projections.

State Advisory Level

In March 2004, the California EPA Office of Environmental Health Hazard Assessment (OEHHA) set a Public Health Goal (PHG) of 6 parts per billion (ppb). State law requires OEHHA to develop PHGs for chemical contaminants in California's publicly supplied drinking water. A PHG is the level of a chemical contaminant in drinking water that, based upon currently available data, does not pose a significant risk to health. Unlike EPA's Drinking Water Equivalent Level, OEHHA's PHG level accounts for exposures to a contaminant from sources besides drinking water. It is not a regulatory requirement, but represents an optimal level that the state's drinking water providers should strive to achieve if it is possible to do so.

OEHHA forwards this number to the California Department of Health Services (CDHS) for use in developing a drinking water standard known as a Maximum Contaminant Level (MCL). CDHS must set MCLs as close as possible to the corresponding PHGs while taking into account technical issues and economic impacts.

Site-Specific Information

EPA has been at the forefront in detecting and treating perchlorate contamination at Superfund sites, and is aggressively pursuing the parties responsible for the perchlorate contamination that has been found in California drinking water. EPA has demonstrated cost-effective, full-scale perchlorate treatment technologies at California's Aerojet, San Gabriel Valley, Lawrence Livermore Site 300, and NASA-Jet Propulsion Laboratory Superfund sites. The San Gabriel perchlorate treatment system was the first in the nation to treat millions of gallons of water per day to deliver clean water to a municipal water supply.

states map

This thumbnail clicks to a map showing the locations of all perchlorate detections in Region 9 reported to EPA as of September, 2004.

"NPL" indicates that the site is listed on the Superfund National Priorities List

Top of page

Aerojet General Corp. Superfund Site, Rancho Cordova (near Folsom) (NPL)

The Aerojet Superfund site is a 5,900-acre rocket motor manufacturing and testing site fifteen miles east of Sacramento, California. Soils and groundwater at the site are contaminated with volatile organic compounds such as trichloroethylene (TCE) and rocket propulsion components including perchlorate and n-nitrosodimethamine (NDMA). In the early 1990s, detection of part-per-million levels of perchlorate in a drinking water supply aquifer led EPA's Superfund team to request the country's first evaluation of perchlorate's toxicity.

The first large-scale perchlorate treatment process in the U.S. was developed and implemented at the Aerojet site in 1998. This biological system treats more than seven million gallons of contaminated ground water each day and reduces blended perchlorate concentrations from 2,500 parts per billion (ppb) to less than 4 ppb. EPA issued a Unilateral Administrative Order in August 2002 that requires Aerojet-General Corp. to design, build, and operate a groundwater extraction and treatment system to contain and clean up groundwater contamination in the western portion of the Aerojet site. The order also requires Aerojet to provide needed replacement water for wells lost due to contamination.

Edwards AFB, near Mojave (NPL)

Edwards AFB is a 301,000 acre military base located in the Antelope Valley region in Southern California. The Base was placed on the NPL in 1990 and entered into a Federal Facility Agreement with EPA, the California Department of Toxic Substances Control, and the California Regional Water Quality Board in 1992.

Perchlorate contamination at Edwards AFB resulted from years of solid-fuel propellant development and rocket testing. This solid propellant testing created several groundwater plumes at several locations on the base. The highest concentration of perchlorate detected at the Base was 160,000 parts per billion (ppb). In May 2003, EPA initiated an ion exchange treatability study that is expected to run for two years. EPA hopes that this study will not only demonstrate the technology's effectiveness, but also achieve cleanup to levels safe to human health and the environment. Since May 2003, 2.6 million gallons of groundwater have been treated and seven pounds of perchlorate have been removed. The Air Force is responsible for all costs associated with the investigation and cleanup of the perchlorate.

Lawrence Livermore National Laboratory, Livermore (NPL)

The 11-acre Lawrence Livermore National Laboratory site has been operated by the University of California for the U.S. Department of Energy (DOE) primarily as a high-explosives and materials testing site in support of nuclear weapons research. This site was named an NPL (Superfund) site in 1990. Approximately 350 people who work in the area and adjacent ranch houses draw drinking water from the aquifer in the immediate vicinity. Nitrate, high explosive compounds and perchlorate are among the groundwater contaminants that resulted from the laboratory's activities since its inception in 1952.

DOE scientists developed an innovative constructed wetlands system to biologically degrade nitrate under relatively low-flow conditions (5 to 10 gallons per minute) at remote locations throughout the site. Both nitrate and perchlorate are degraded to harmless elements by related microbial populations that are supported by the wetlands, which are contained in tanks that can be relocated as necessary.

There are currently two treatment facilities with wetlands, used in conjunction with ion exchange, and one more facility is planned. The contained wetlands have reduced perchlorate concentrations from 10 to 20 micrograms per liter (µg/L) to less than 4 µg/L. Nitrate concentrations have been reduced from 90+ µg/L to below 45 µg/L (the discharge requirement).

NASA Jet Propulsion Laboratory, Pasadena (NPL)

NASA Jet Propulsion Laboratory is a space science lab covering 176 acres in Pasadena. The Laboratory was placed on the NPL in 1992 after several solvents were found in nearby drinking water wells. Perchlorate was first discovered at the same wells in 1996. Subsequent on-site and off-site investigations have identified an on-site source area with levels of perchlorate in groundwater around 1,500 parts per billion (ppb). The off-site portion of the plume has levels up to 200 ppb, and the plume has caused seven water supply wells to be taken out of service.

In July 2004, NASA paid for the installation of an ion exchange and carbon treatment system at the Lincoln Avenue Water Company. The system is currently treating approximately three million gallons per day. An on-site treatment system is under construction. This system will use a fluidized bed biological reactor to treat approximately 125 gallons per minute from the source area. The treated water will then be injected back into the aquifer.

Negotiations and design are currently underway to install an ion exchange system on wells owned by the City of Pasadena. The plume should be contained and treatment systems installed on affected city wells by mid-2005.

Olin Flare Facility, Morgan Hill

Perchlorate contamination beneath a former flare manufacturing plant was first discovered in 2000, several years after the plant had closed. The plant had used potassium perchlorate as one of the ingredients during its 40 years of operation. By late 2003, the state of California and the Santa Clara Valley Water District had confirmed a groundwater plume currently extending over nine miles through residential and agricultural communities.

The Regional Water Quality Control Board and the Santa Clara Valley Water District have engaged in a major outreach effort that has received extensive press and community response. A well testing program is underway for approximately 1,200 residential, municipal, and agricultural wells in the area. Large ion exchange treatment units are operating in three public water supply systems that include seven municipal wells where perchlorate has been detected. The potentially responsible parties, Olin Corporation and Standard Fuse Incorporated, are supplying bottled water to nearly 800 households with private wells. The Regional Water Quality Control Board is overseeing PRP cleanup efforts.

Rialto-Colton Area, San Bernadino

In the Rialto-Colton area in San Bernadino, California, perchlorate has been detected in 20 water supply wells at concentrations above the California action level of four parts per billion (ppb). The loss of these wells has created a serious water supply shortage. EPA has issued a Unilateral Administrative Order to two former operators at the site, and the State of California Regional Water Quality Control Board has issued investigation orders to 19 parties suspected of testing, manufacturing, storing, or disposing of perchlorate-containing materials in the area.

The state has already provided $6 million to help the affected water utilities purchase water treatment equipment. One of the potentially responsible parties has provided an additional $4 million. As of September 2003, the water utilities have installed four ion exchange systems, and by the end of 2005, four more systems are expected to go online, allowing treatment of more than 20 million gallons per day of perchlorate-contaminated groundwater.

San Gabriel Valley, Baldwin Park Superfund Sites (NPL)

The San Gabriel Valley Superfund sites include multiple areas of contaminated ground water in the San Gabriel Basin aquifer, a critical source of drinking water in Southern California. Groundwater contamination at the sites results from the cumulative impact of decades of spills, improper chemical handling and disposal practices. The most prevalent contaminants in the ground water are trichloroethene (TCE), perchloroethylene (PCE), carbon tetrachloride, perchlorate, and N-nitrosodimethylamine (NDMA).

Perchlorate has been detected in at least 23 water supply wells at the San Gabriel Valley Superfund sites. Most of the contaminated wells are located in the Azusa/Baldwin Park area, where the testing and manufacture of solid-fuel rockets in the 1940s and 1950s is believed to be the primary source of the contamination. The first perchlorate treatment system was completed in March 2001, making use of ion exchange technology. The system cleans up the ground water and supplies drinking water to approximately 9,000 San Gabriel Valley residents.

The four perchlorate treatment systems, estimated to cost more than $17 million to install and roughly $5 million per year to operate, will supply drinking water to more than 100,000 San Gabriel Valley residents. Over the next 15 years, it is expected that more than $200 million will be spent on cleanup of perchlorate and other groundwater contaminants at the Baldwin Park site alone. The costs are being paid by a group of potentially responsible parties and federal appropriations earmarked for San Gabriel Valley cleanup

More information about San Gabriel Valley, Baldwin Park Superfund site (PDF) (4 pp, 420K  About PDF)

Stringfellow Superfund Site, Jurupa Valley (NPL)

The Stringfellow Superfund site is located near the community of Jurupa Valley, in Riverside County. From 1955 until 1972, the 17-acre Stringfellow site was operated as a state-permitted hazardous waste disposal facility. More than 35 million gallons of industrial waste, primarily from metal finishing, electroplating, and pesticide production were deposited in various pits at the site. Cleanup efforts, led by California Department of Toxic Substances Control (DTSC), have focused on controlling the waste sources and capturing the contaminated groundwater plume.

In May 2001, California officials detected perchlorate in groundwater throughout the site, including parts of the aquifer beyond the existing plume capture area. The highest perchlorate concentration detected in ground water was 87,000 ppb at the source. Perchlorate was also detected in approximately 30 private wells in the area; contamination ranged from 2.1 to 37 ppb. DTSC hired a contractor and finalized the work plan to conduct a remedial investigation and feasibility study to respond to the perchlorate contamination.

Stringfellow Superfund Site (Jurupa Valley, CA)

California Department of Health Services Fact Sheets:

Proposed Public Health Goal for Perchlorate - CalEPA fact sheet (PDF) (2 pp, 124K  About PDF)

Top of page

Region 9 Topics and Programs | A-Z Index

Local Navigation

Jump to main content.