SITE INFORMATION AND CORRESPONDENCE

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Antonia Vorster -2- 16 February 2011 2009 showed the concentration dropping to 22 ug/I. Georgia-Pacific provided a statistical trend analysis that projected the cleanup goal in BC-19 will be met in 2016. • Chloroform concentration in the groundwater ranges from 22 ug/I in BC-19 at the source area, to non-detect. • Chloroform concentration decreases down-gradient from the source area, and is naturally attenuating (Figure 4 and Figure 5). • The Mann-Kendall trend analysis was used to predict concentration trends in individual monitoring wells. The analysis showed that chloroform is diminishing in all site monitoring wells except well BC-20, which is the furthest down-gradient well, about 1,200 feet down-gradient of the source. However, chloroform in this well is 2.6 ug/I, below the established cleanup goal of 5 ug/I, and may be affected by residential landscape watering. • A potable water sample collected from the former G-P building contained 7 ug/I chloroform, and is representative of what could be contributed from residential watering. Actions: • On 25 September 1984, the Regional Board issued a Cleanup and Abatement order to Georgia-Pacific to stop seepage of pollutants from the storm-water pond and stop pollution of the groundwater and odor nuisance. • Starting in October 1984, 150,000 gallons of standing water were pumped out of the basin and disposed offsite. Wastewater flow to the basin was discontinued. • Contaminated soil beneath the basin was sampled. Chloroform concentrations in the samples ranged from 0.020 to 200 milligrams per kilogram (mg/kg). Based on sampling results, nearly 1,500 cubic yards of sludge and soil were excavated from the basin floor and sidewalls and shipped offsite during February and March 1985. Confirmation soil samples were collected from the sidewalis and bottom of the excavated area. Chloroform concentrations in the samples ranged from 0.004 to 3.4 mg/kg. • Contaminated ground water in the basin area was extracted and treated using a ground water extraction and air stripper treatment system between June 1985 and February 1992. Approximately 194 million gallons of ground water was treated, removing about 139 pounds of chloroform. • An in situ ozone sparge system containing 12 sparge wells for treatment of residual chloroform was approved on 11 September 2003. • The CAO was rescinded on 5 November 2003. California Environmental Protection Agency *Recycled Paper