SITE INFORMATION AND CORRESPONDENCE

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0 0 Re-Manufacturing, Ltd. -2- 26 June 1991 Closure Plan lead concentrations in the slough, in the proximity of the surface impoundment, represent background for the slough. According to the plan, all soils containing total lead above the BTLV of 785.7 mg/kg will be excavated from the impoundment. This would remove soils above the Total Threshold Limit Concentration (TTLC) of 1,000 mg/kg, but may not remove hazardous concentrations of soluble lead. Table 4 in the closure plan shows the ratio of soluble lead to total lead in the surface impoundment soils varies from 11 percent to 73 percent, using the citrate Waste Extraction Test (WET) . (The ratio of 1 . 1 mg/l soluble lead to 100 mg/kg total lead is, for instance, 11 percent and not 1 .1 percent because of the ten fold dilution in the WET method. ) Two samples I collected from the impoundment on 3 May 1991 contained 67 and 68 percent soluble lead. Therefore, a sample with a concentration of total lead at 75 mg/kg or greater may still contain levels of soluble lead above the Title 22 Soluble Threshold Limit Concentration (STLC) value of 5 mg/l , which is considered hazardous. Performing the :e-ionized water WET on impoundment samples, howev r, has yielded non-detectable results in the past. The plan states that levels of total lead below 785.7 mg/kg do not pose a threat to water quality at this time. However, the impoundment will still contain hazardous concentrations (above the STLC) of soluble lead. Looking at the percentages of soluble lead to total lead already observed, soils with a concentration of 785.7 mg/kg total lead could have a corresponding soluble lead concentration ranging from 8.6 mg/l to 57.3 mg/1 . Hazardous concentrations of soluble lead, combined with the fact that the impoundment is djacent to Mormon Slough, continue to pose a threat to water quality Therefore, isolation of the waste from surface waters and prevention of migration toward ground water must be assured by the closure plan. It is suspected that the entire site contains "hot spots" with high levels of lead. For example, samples collected 4 and 5 feet below ground surface, roughly 150 feet east of the surface impoundment, contained 3270 mg/kg and 476 mg/kg total lead, respectively. The corresponding soluble lead values were 70.4 mg/l and 2.5 mg/1 . In addition, recent samples collt :ted by the Department of Health Services (DHS) in the excavation at the El Dorado Chemical Company contained hazardous levels of total lead (soluble results are pending) . The excavation is on the Moore property, immediately adjacent to Mormon Slough (see attached sampling data) . Furthermore, DHS staff observed battery casings and ether debris in the sidewalls of E1 Dorado's excavation, indicating that their tank was constructed above fill material from past disposal practices at the site. These "hot spots" are not considered appropriate background levels and because of their distance from the impoundment, it is not likely that the lead contamination migrated from the TPCA surface impoundment. We concur that the definition of the lateral extent of the contamination resulting from discharges to the surface impoundment would be difficult, if not impossible to distinguish from what appears to be contaminated fill on the property. Re-Manufacturing has defined the lateral extent of the lead contamination resulting from the surface impoundment to the north and west as the width of the levees. To the south, the lateral extent of the impoundment contamination was not defined with the latest sampling effort. Again it is unclear if the southern sidewall is fill material .