UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 9 75 Hawthorne Street San Francisco , CA 94105-3901
June 7 , 2010 MEMORANDUM SUBJECT: De-Proposal ofthe 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 ofToxic 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 -dichloroprop ane). 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 cutoffregardless 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 ofthe site, GBF Ho ldings 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 ofthe 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 's table 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 ofhistoric high chlorinated solvent concentrations in groundwater. V. Conclusion The GBF, Inc
., Dump Site will continue to be cleaned up by the current owners ofthe site under the regulatory authority ofthe 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 ofthe site file, believes that it would be appropriate to de

-propose GBF , Inc
., Dump from listing on the NPL.
Attachment: Consent Order