Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Del Norte Pesticide Storage
EPA #: CAD000626176
County: Del Norte
City: 1 mile northwest of Crescent City
Congressional District: 01
Other Names: Del Norte County Department of Agriculture Del Norte County Airport
The Fourth Five Year Review was completed on June 19, 2015. A copy of the report and the attachments can be found in the Documents and Reports section of this site summary, as well as in the listed public information repositories.
For more information, please contact the EPA Site Manager or the EPA Community Involvement Coordinator in the Contacts section below.
On this page
Description and History
NPL Listing History
NPL Status: Deleted
Proposed Date: 09/08/83
Final Date: 09/21/84
Deleted Date: 09/18/02
The Del Norte County Pesticide Storage Area site operated from 1970 until 1981, accepting containers from local agricultural and forestry related industries. The site was intended to be an interim or emergency storage area for pesticide containers, which previously had been triple-rinsed and punctured. Wastes and rinse water were improperly disposed of in an unlined sump. Approximately 1,600 drums that had held the wastes and rinse water were recovered and recycled by the County Agricultural Department. This site is bordered by the Pacific Ocean, State-owned land, residences, and farmland. Private wells supply the domestic water to the area, and four wells are located within 2,500 feet of the site. In 2007, approximately 1500 people resided within a one-mile radius of the site.
The 5 ppb (parts per billion) drinking water standard for the final contaminant was achieved in all groundwater monitoring results since 2013, and only one sample was above 5 ppb since 2011. Monitoring is continuing on a reduced schedule to confirm that the groundwater has attained the drinking water standard. EPA worked with DTSC to complete the fourth Five Year Review in June 2015 which examined the monitoring results and all new information about the site and the contaminants present. We concluded that the site remains protective.
Contaminants and Risks
- Soil and Sludges
Groundwater and soil were found to be contaminated with various pesticides, herbicides and volatile organic compounds (VOCs). The primary contaminant remaining was the pesticide1,2–Dichloropropane (DCP), which had been used principally to control nematode worms on roots and bulbs. Coming into direct contact with or accidentally ingesting contaminated soil or groundwater may pose a potential threat to human health.
Who is Involved
This site was being addressed through Federal actions. The State of California, Department of Toxic Substances Control (DTSC) and the Del Norte County Department of Health and Human Services, Public Health Branch, are actively involved in monitoring groundwater quality.
Immediate Actions: In 1987, the EPA removed nearly 300 cubic yards of contaminated soils that were considered to be the source of groundwater contamination. This action alone resulted in a decrease in groundwater contamination from about 2000 ppb to less than 500 ppb in the two years before the groundwater treatment system began operating.
An air stripping groundwater treatment system was built in 1989 and operated for seven years, treating over 23 million gallons of groundwater and reaching protective levels for all contaminants except DCP. The DCP concentrations dropped from over 400 parts per billion (ppb) in 1990 to about 40 ppb by 1996. However, about 95 percent of the contaminants were removed within the first four years of treatment. After several attempts to optimize the treatment, it was shown that the concentration of the remaining contaminants would slowly decline whether or not the pump and treat system was operating. In October 1997, the pump and treat system was discontinued with the DCP level at 38 ppb. Monitoring results indicated that the groundwater contamination was not spreading any further. EPA, the State and Del Norte County agreed to monitor the final small area of contaminated groundwater until the protective goal of 5 ppb was reached everywhere. The County also instituted controls to prevent inadvertent exposure to contaminated land or to the water supply of nearby residents.
In 1985, the EPA selected a cleanup remedy for the entire site that included: excavation and off-site disposal of the remaining contaminated soils from the sump and trench areas; extraction of contaminated groundwater; treatment of contaminated groundwater by (carbon adsorption) coagulation and sand filtration technologies; piping of treated groundwater to the county sewer main; and groundwater monitoring.
Although initial cleanup actions were thought to be completed in the spring of 1992, the lack of contaminant reduction in the groundwater during the treatment in 1992 and 1993 led the EPA to install a pumping well and an air injection system in 1994. As of May 1996, approximately 23 million gallons of contaminated groundwater had been treated and discharged.
An Amendment to the Record of Decision was signed on August 29, 2000. The remedy was changed to halt active pumping and treating of the contaminated groundwater, which was no longer effective at reducing the level of DCP in the groundwater. A Technical Impracticability Waiver was granted for the site, and monitoring will continue until the level of DCP reaches below the drinking water standard (known as the Maximum Contamination Level or MCL) of 5 ppb.
The Del Norte Site was deleted from the National Priorities List on September 18, 2002. California EPA’s Department of Toxic Substances Control is currently the lead at the site, with the US EPA responsible for a comprehensive review of the cleanup every five years while the cleanup objects are being reached. Del Norte County will continue to monitor water quality at the site on a reduced schedule to confirm that the groundwater has attained the MCL of 5 ppb. Sampling conducted at the site through October 2009 indicates that contaminant levels declined naturally in the final two monitoring wells where contamination had been detected. Samples of Monitoring Well (MW) 104 and MW 105 had no detectable DCP on May 18, 2015.
Semi-annual sampling results through 2015 show a general trend of decline in the levels of DCP in the shallow groundwater. (See June 2015 Five Year Review.) Variation in annual rainfall causes distinct changes in the depth of the water table from year to year, and the contaminant concentrations show some variation as well. Monitoring will need to continue for several years to confirm statistically that the cleanup is permanently below the 5 ppb drinking water standard.
Cleanup Results to Date
The removal of contaminated soils and the installation and operation of the groundwater treatment system at the Del Norte Pesticide Storage site have reduced the potential for exposure to contaminated materials. All construction at the site is complete. Concentrations of the targeted groundwater contaminant, DCP, have decreased over time. Since 2005, all groundwater samples have been at 10 ppb or less. The site has been de-listed. EPA will re-evaluate the progress at the site until it is certain that the 5 ppb drinking water standard has been permanently achieved.
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.
In May 1998, EPA and DTSC recovered a portion of the cleanup costs for the cleanup of the Del Norte site from a group of agricultural and forestry companies and agencies. In March 2002, EPA and DTSC reached a settlement with Del Norte County that was formalized in a Consent Decree.
Documents and Reports
Public Information Repositories
The public information repositories for the site are at the following locations:
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
Department of Toxic Substances Control,
700 Heinz Ave, Suite 200
Berkeley, CA 94710-2721
Senior Environmental Health Scientist
Environmental Health Division,
981 H Street, Suite 110
Crescent City, CA 95531
After Hours (Emergency Response)