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CaliforniWgional Water Quality Cotrol Board .;..., <br /> Central Valley Region I= E <br /> Katherine Hart, Chair •a <br /> 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 <br /> Linda S.Adams Phone(916)464-3291 •FAX(916)464-4645 Edmund G.Brown Jr. <br /> Acting Secretary for http://www. s.ca.gov/centralvalley Governor <br /> Environmental Protection <br /> TO: Antonia K. J. Vorster kw <br /> FROM: Gerald Djuth <br /> Site and Groundwater Cleanup Private Sites Cleanup Unit <br /> Program Manager <br /> SIGNATURE: ��� Q� <br /> Duncan A. Austin, Chief <br /> Private Sites Cleanup Unit <br /> DATE: 16 February2011 SIGNATURE: ` <br /> SUBJECT: RATIONALE FOR CONSIDERING NO FURTHER ACTION ON GEORGIA- <br /> PACIFIC CORPORATION, FORMER TRACY CHEMICAL PACKAGING <br /> PLANT, 75 W. VALPICO ROAD, TRACY, SAN JOAQUIN COUNTY <br /> Setting: The facility is rectangular in shape, approximately 15 acres in size, and located <br /> about two miles south of the City of Tracy (Figure 1). The site is bordered by a residential <br /> area to the north, light-industrial and commercial areas to the south, and open fields on <br /> both the east and west sides. The residential area is downgradient of the source area. <br /> Groundwater is about 45 feet below ground surface, with a gradient to the northwest <br /> (Figure 2). <br /> Source: A percolation basin being used for the disposal of waste cooling water and <br /> stormwater runoff was treated with sodium hypochlorite bleach in July 1984 to mitigate <br /> sulfite-type odors, resulting in the formation of chloroform. . <br /> Rationale: Georgia-Pacific has completed several rounds of remediation, including source <br /> area removal of 150,000 gallons of standing water, excavation of 1 ,500 yd of sludge, <br /> operation of a groundwater extraction and treatment system for over 6 years, and <br /> attempted in-situ chemical oxidation of residual chloroform. On-site monitoring wells have <br /> well documented decreases in chloroform and continue to decline (Figure 3). The <br /> chloroform is naturally attenuating, is below the California Primary Maximum Contaminant <br /> Level (MCL) of 80 ug/I in all monitoring wells, and is approaching the cleanup goal of 5 ug/I <br /> set in 1996. <br /> Issues: Although dissolved phase chloroform concentrations in ground water have <br /> diminished to levels below the MCL in all monitoring wells, a sample well BC-19 from 2006 <br /> showed a spike to 40 ug/I of chloroform in groundwater at the source area. This <br /> concentration is above the cleanup goal of 5 ug/l. However, the most recent data from <br /> California Environmental Protection Agency <br /> Q?Recycled Paper <br />