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' WORK PLAN FOR ADDITIONAL <br /> ' SOURCE AREA ASSESSMENT <br /> ' FORMER GEORGIA-PACIFIC CORPORATION <br /> TRACY CHEMICAL PACKAGING PLANT <br /> 75 WEST VALPICO ROAD,TRACY, CALIFORNIA <br /> AME PROJECT NO. 16014.01 <br /> 1.0 INTRODUCTION <br /> ' Acton • Mickelson • Environmental, Inc., on behalf of Georgia-Pacific Corporation (GP), has <br /> prepared this Work Plan for Additional Source Area Assessment(Work Plan) as requested by the <br /> California Regional Water Quality Control Board, Central Valley Region (RWQCB) in a <br /> meeting at the former GP Tracy Chemical Packaging.Plant(site, Figure 1) on August 16, 2001. <br /> ' The objectives of the investigation are to (1) assess whether chloroform concentrations in the <br /> vadose zone beneath the storm water basin (the source area) could be contributing to the ground <br /> water impact, (2) characterize the vertical extent of chloroform and other volatile organic <br /> ' compounds (VOCs) in ground water beneath the storm water basin, and (3) assess the feasibility <br /> of in-situ remediation. <br /> 2.0 BACKGROUND <br /> Standing water and sludge were removed from the basin and disposed offsite between <br /> October 1984 and January 1985 in response to a Cleanup and Abatement Order issued by the <br /> ' RWQCB on September 25, 1984. Chloroform was reported at concentrations up to <br /> 190,000 micrograms per liter (pg/L) in the removed pond water and up to 200,000 micrograms <br /> per kilogram(pg/kg) in the removed sludge. <br /> Sampling and interim remedial measures were conducted in the basin area from January to <br /> March 1985. Fourteen shallow soil samples were collected from the basin floor at depths of 0.1 <br /> to 2.8 feet below ground surface (bgs). Chloroform was reported at a maximum concentration of <br /> 1,200 pg/kg, prompting an over-excavation remediation. A 10-square-foot area in the basin <br /> floor was excavated to a depth of 3 feet. Confirmation samples collected from the base of the <br /> excavation reported up to 3,400 pg/kg chloroform prompting additional excavation. The total <br /> volume of removed sludge and soil was 1,500 cubic yards (Brown and Caldwell, 1985). Gravel <br /> was placed in the base of the excavation in November 1985 to restore the original elevation <br /> (approximately 17 feet bgs). <br /> ' A ground water pump and treat remediation system operated from June 1986 to September 1991. <br /> Recovery wells RW-1 (installed May 1985) and later RW-2 (installed November 1989) were <br /> 82001-032.dm <br />