Remediation Overview

Background
Soil Investigations and Site Reuse
Groundwater and Surface Water Monitoring
Groundwater Remediation
More Information

Background

The DuPont Oakley Site is located in the city of Oakley, California, about 40 miles from San Francisco and 50 miles from Sacramento.

When DuPont built the former Antioch plant back in the 1950s and early 60s, we were a leader in the development of best engineering and construction practices, just as we are now. But the people in our industry have learned a lot in the last 50 years, and even though the original manufacturing plants were designed and built to the highest standards at that time, we now know that these mid-century Best Engineering and Operational Practices could not completely prevent releases of chemicals to soil and groundwater. Unfortunately, this is not a problem that's unique to the Oakley Site. Almost without exception, industrial facilities built before the 1980s have at least some degree of soil or groundwater contamination that resulted from past manufacturing operations.

At Oakley, the good news is that an effective remediation program is under way to restore the site to beneficial use by the local community. In the late 1990s, DuPont closed and demolished its manufacturing operations at Oakley, which meant that other uses for the property could be evaluated. Because the site is a significant part of the City of Oakley’s revitalization plans, DuPont determined that site cleanup, or remediation, should be conducted with a specific redevelopment plan in mind. For more information on these redevelopment plans, please click on this Site Redevelopment link.

Before the site can be released for future development, DuPont and the California Department of Toxic Substances Control (DTSC, or the Department) must agree that all contamination at the site has been identified and removed or controlled to meet exacting standards for safe public access. Federal and state regulations determine the way that a site’s investigation and remediation programs are performed. DuPont signed a Corrective Action Consent Agreement with DTSC in June 2003 that directs the various stages required to complete Oakley Site cleanup. The investigations and risk assessments described below are used to design remediation programs that will allow DuPont and DTSC to safely and confidently return the Oakley Site to active public use.

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Soil Investigations and Site Reuse In 2005, DuPont submitted the results of investigations to DTSC that allowed the Department to recommend the release of almost 50 acres on the site perimeter, the Western and Eastern Development Areas, for unrestricted future development. In March 2006, DuPont submitted a report to DTSC that included the results of more than 1,000 soil samples collected throughout the remaining area of the site. This soil investigation was primarily focused on the site’s former manufacturing areas, but also included a distribution of samples from other adjacent, or “open” areas, that will also be developed. The Department’s review of this Phase 1 Soil Investigation Report will provide comments and recommendations that DuPont must include in its remediation and redevelopment plans. The report is designed to identify areas of the site that will require remediation, as well as highlight those areas where soil samples indicated that commercial and industrial development can proceed without the need for remediation. Back to Top Groundwater and Surface Water Monitoring DTSC also controls the monitoring programs required of DuPont to evaluate the quality of groundwater underneath, and surface water adjacent to, the Oakley Site. Currently, groundwater monitoring includes samples every 6 months for as many as 197 wells screened at various depths to as much as 115 feet below ground surface. A variety of chemicals spilled or released during active manufacturing operations are found in groundwater underneath the site; however, drinking water wells are not allowed on the site. Because groundwater ultimately discharges to surface water bodies adjacent to the site, DuPont also collects surface water samples every 6 months at 20 sampling locations along the San Joaquin River. Surface water sample results have consistently demonstrated that the San Joaquin River is a safe drinking water source and Little Break is a high quality ecological environment. Back to Top

Groundwater Remediation

In addition to the groundwater and surface water monitoring programs described above, DuPont has conducted numerous groundwater investigations that helped guide the selection of remediation alternatives to improve groundwater quality. The most recent phase of groundwater remediation was completed in 2005, when DuPont installed a 485﷓foot-long, 117﷓foot-deep, underground Permeable Reactive Barrier, or PRB, to destroy carbon tetrachloride contaminants in groundwater. The first 110-foot segment of the PRB was installed in 2001 as a proof-of-concept experiment, or pilot test. A three-year monitoring program demonstrated the effectiveness of this pilot PRB and DTSC authorized DuPont to complete construction of the full-scale PRB system in 2005.

Over the next several years DuPont will monitor the PRB to verify its performance, with results reported every six months to DTSC. In addition, based on the analysis of all data from the comprehensive, sitewide groundwater monitoring program, DuPont will propose other groundwater remedies in areas that are not currently addressed by the PRB.

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More Information

For more information about the DuPont site investigation and remediation programs, please click on this link to the Publications web page for documents available via download from this website, or click directly on the links shown below. Local residents will find complete copies of all reports submitted by DuPont to DTSC at the Oakley Public Library, located at 1050 Neroly Road, Oakley, CA.

Oakley Repository – List of Available Documents
DTSC 2005 Fact Sheet
DTSC 2006 Fact Sheet
2005 Annual Groundwater Monitoring Report: Executive Summary
2005 Annual Surface Water Monitoring Report: Executive Summary
Phase 1 Groundwater Interim Measures Work Plan: Introduction
PRB Construction Completion Report: Introduction, Summary and Conclusions
Phase 1 Soil RFI Report: Executive Summary

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