UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 


REGION 9 


75 Hawthorne Street 


San Francisco, CA 94105-3901 


June 7, 2010 

MEMORANDUM 

SUBJECT: 	 De-Proposal of the GBF, Inc. , Dump Site 

FROM: 

Antioch, Cal' ./ 

tor 

TO: 	 Betsy Southerland, Director 

Assessment and Remediation Division 

1. Introduction 

The U.S. Environmental Protection Agency (EPA), Region 9, is requesting to withdraw its 

earlier proposal to list the GBF, Inc., Dump Site on the National Priorities List (NPL). The 

proposal was published in the Federal Register on February 7, 1992 (4824 - 4830 Federal 

Register / Vol. 57, No. 26). This request is supported by the California Department of Toxic 

Substances Control (DTSC), which is overseeing the site cleanup pursuant to a California 

Consent Order. EPA has reviewed all of the documentation supporting this action and feels 

confident that California will take all appropriate cleanup action through the agreement already 

in place. 

II. Site Background 

The GBF, Inc. , Dump (the Dump) covers approximately 88 acres at the comer of Somersville 

Road and James Donlon Boulevard in Antioch, Contra Costa County, California. The site is 

bounded on the south, east, and northeast by residential developments, and on the west and 

northwest by open space. An intermittent creek, Markley Creek, runs along the western 

boundary. A drinking water canal, operated by the Contra Costa Water District (CCWD) and 

carrying water from the Sacramento-San Joaquin Delta, runs along the northern boundary. 

CCWD supplies the public with drinking water from the Delta. Groundwater in the area is not 

used for drinking water. The depth to groundwater increases in the direction of groundwater 

flow (north). The depth to groundwater at the Dump is 30 feet below ground surface (BGS). 

The depth to groundwater at the downgradient edge of the plume is 100 feet BGS. 

From the early 1960s to 1975 the Dump accepted hazardous waste in the form of sludges, acids, 

oils and slurries containing numerous chemicals, including hexavalent chromium, lead, cyanide, 

asbestos, benzene, trichloroethylene (TCE), tetrachloroethylene (PCE), and DDT. The primary 

contaminants of concern in the groundwater are volatile organic compounds (i.e., TCE, PCE, 

carbon tetrachloride, vinyl chloride, benzene, and 1 ,2-dichloropropane). The Dump continued to 

accept non-hazardous municipal waste until 1992. 
III. NPL Listing History 

In June 1988 EPA proposed the site to the NPL. In response to public comments, the Hazard 

Ranking System (HRS) score was recalculated and it fell below the cutoff of 28.5 , so EPA 

dropped the site from consideration for the NPL. 

In 1991 EPA used the revised HRS to evaluate the site and, using new information to evaluate 

the surface water pathway, the site qualified for NPL proposal. Before the second proposal, 

DTSC requested that EPA not propose listing the site. EPA' s policy at that time was to propose 

sites that scored above the NPL cutoff regardless of state involvement, so EPA proceeded with 

the NPL proposal. However, since the State of California was managing the cleanup at the site, 

EPA agreed to let DTSC continue its oversight role. On February 7, 1992, EPA re-proposed it to 

the NPL. 

IV. State of California Enforcement Activities and Cleanup 

In 1988 the California Department of Health Services, the predecessor to DTSC, issued a 

Remedial Action Order to the current and historic site operators, owners, and hazardous waste 

generators in order to initiate site characterization and remediation efforts. In 1997, following 

several years of soil, groundwater and landfill gas investigations, DTSC issued a Remedial 

Action Plan for the site, with groundwater pump-and-treat as the remedy. In 2001 DTSC and the 

current owners of the site, GBF Holdings LLC, entered into a Consent Order, which remains in 

effect today. 

In 2001 a landfill cap was installed and in 2002 the landfill was certified closed by the 

Sacramento Regional Water Quality Control Board. In 2002 and 2003 the groundwater 

extraction and treatment system was installed along the porthern (downgradient) boundary of the 

landfill. The treatment system consists of 30 extraction wells and an activated carbon treatment 

system. Semi-annual groundwater monitoring and sitej pspections are part of the operations and 

maintenance ofthe remedy. The footprint of the plume iS'stable and contaminant concentrations 

are neither increasing nor decreasing. Treated groundwater is discharged, under permit, to the 

Delta Diablo Sanitation District. 

DTSC is currently completing the Five-Year Review Report for the site. The Report 

recommends a more aggressive approach to the groundwater cleanup, such as in-situ enhanced 

reductive dechlorination. DTSC is also requiring soil vapor sampling in areas of historic high 

chlorinated solvent concentrations in groundwater. 

V. Conclusion 

The GBF, Inc., Dump Site will continue to be cleaned up by the current owners of the site under 

the regulatory authority of the State of California. DTSC has been, and will continue to be, the 

lead agency responsible overseeing for the cleanup. DTSC believes that Superfund involvement 

at this site is not warranted and in a letter to EPA dated May 13 , 2010, requested that the site be 

de-proposed from the NPL. Region 9 concurs with DTSC' s request and, based on EPA' s review 

of the site file, believes that it would be appropriate to de-propose GBF, Inc., Dump from listing 

on the NPL. 

Attachment: Consent Order