Located in Riverside County approximately five miles northwest of the City of Riverside and one mile north of the community of Glen Avon, the Stringfellow Hazardous Waste Site occupies 17 acres at the head of Pyrite Canyon in the Jurupa Mountains. Commonly referred to as the Stringfellow Acid Pits, the site functioned as a Class I industrial waste disposal facility permitted by the Santa Ana Regional Water Quality Control Board (RWQCB) from August 1956 to November 1972. In 1955, the RWQCB contacted James B. Stringfellow, owner of the Stringfellow Quarry Company, to discuss the creation of an industrial waste dump on a portion of his company's land in the Jurupa Mountains. Following a report by the State Division of Water Resources approving use of the site, Stringfellow agreed to the proposal, and the dumping of toxic wastes commenced in 1956. Approximately 34 million gallons of industrial wastes, which belonged to some of the most high-profile American companies and contained over 200 hazardous chemicals, were disposed of over the course of the site's 16-year operation.

In 1969, excessive rainfall caused the reservoirs at the facility, known as evaporation ponds, to overflow into Glen Avon. That same year, Parents of Jurupa, Inc., a non-profit corporation comprised of Glen Avon residents, was established with the goal of permanently closing and cleaning up the Stringfellow site, which was believed to be the cause of many health problems in the community. Due in part to the lobbying efforts of the organization, the site officially ceased operation in November of 1972 and permanently closed the following month. The facility's state permit was revoked as a result of waste-discharge violations, and management of the site subsequently passed from the Stringfellow Quarry Company to Riverside County in 1974, with operational responsibility assigned to the RWQCB. Responsibility later passed to the California Department of Health Services (DOHS) in 1981.

In 1980, the United States Congress passed the Comprehensive Environmental Response, Compensation and Liability Act, which established a $1.6 billion trust fund known as the "Superfund" for the emergency cleanup of chemical spills and hazardous waste dumps in the U.S. The Stringfellow Hazardous Waste Site was officially placed on the United States Environmental Protection Agency's (US EPA) Superfund national priority list in 1983. By that time, contaminants had already moved into the local groundwater supply in Glen Avon, requiring residents to ultimately receive water from public utilities. Cleanup efforts were jointly managed by the US EPA and the DOHS Toxic Substances Control Division (later Department). According to the US EPA, Region IX website, the site cleanup process has progressed in five phases: an initial action phase (1980-1984) and four long-term remedial action phases (1984-present). The latter phases include the installation of a pre-treatment plant, contaminant source control, the cleanup of the lower canyon, and the hydraulic control and cleanup of the contamination affecting the community water supply wells. The site is geographically divided into four zones as follows: Zone 1 - On-site/Upper Mid-Canyon Area, Zone 2 - Mid-Canyon Area, Zone 3 - Lower Canyon Area, and Zone 4 - Glen Avon Community.

Since 1996, the Department of Toxic Substances Control, a branch of the California Environmental Protection Agency, has maintained operational control at Stringfellow, with the US EPA serving as an oversight agency. Treatment of the hazardous waste site is ongoing.

1955:

James B. Stringfellow, owner of the Stringfellow Quarry Company, was contacted by California officials to discuss the creation of a 17-acre hazardous waste dump on his property.

1956:

In August, Stringfellow began operating a class I hazardous waste disposal facility permitted by the Santa Ana Regional Water Quality Control Board (RWQCB).

1969:

Excessive rainfall caused the disposal ponds at Stringfellow to overflow into Glen Avon.

Parents of Jurupa, Inc., a non-profit corporation of Glen Avon residents, was established with the goal of closing down the Stringfellow HazardousWaste Site.

1972:

The Stringfellow Hazardous Waste Site ceased operation as a disposal facility in November, and closed permanently in December.

1974:

The State of California gained control of the Stringfellow Hazardous Waste Site, with the RWQCB serving as the responsible party.

1978:

Excessive rainfall caused the disposal ponds at Stringfellow to overflow into Glen Avon a second time.

1980:

The United States Congress passed the Comprehensive Environmental Response, Compensation and Liability Act. Known as the "Superfund," the Act provided $1.6 billion for the emergency cleanup of chemical spills and hazardous waste dumps.

1981:

Responsibility for the Stringfellow Hazardous Waste Site passed from the RWQCB to the California Department of Health Services (DOHS).

1983:

The United States Environmental Protection Agency (US EPA) officially placed the Stringfellow Hazardous Waste Site on the national priority list for the federal Superfund.

1984-Present:

Cleanup activities, jointly managed by the US EPA and DOHS Toxic Substances Control Division, began at the Stringfellow Hazardous Waste Site. Treatment is ongoing.

1996:

The Department of Toxic Substances Control, a branch of the California Environmental Protection Agency, assumed operational control at Stringfellow, with the US EPA serving as an oversight agency.