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Summary of Northern California Youth Center Sampling Results Week of May 14,2007 Forward Landfill-Austin Road Unit,California Page 2 Each tank contained an accumulation of sediment approximately 3 feet thick at its thickest point. Approximately 9 cubic yards of sediment were removed from the northernmost tank, 9 cubic yards from the middle tank, and 12 cubic yards from the southernmost tank. After removal of the sediment from each tank, the interior of the tank was inspected for signs of corrosion, chemical nodules, or physical damage.Aqua-Tech Company personnel reported that each tank was in satisfactory condition. Quality of Sediment Removed from the Storage Tanks A sample of sediment removed from each of the three tanks was submitted for laboratory analysis of VOCs. Tetrachloroethene was detected at a concentration of 3.3 ug/kg in a primary sample of the ' sediment removed from the northern tank,and a concentration of 5.4 ug/kg in a duplicate sample of the sediment removed from the northern tank (PQL = 5 ug/kg). Tetrachloroethene was not detected in sediment removed from the center storage tank or the southern storage tank(PQL=5 ug/kg). Water Quality in the Storage Tanks After Completion of Cleaning Activities Subsequent to sediment removal operations, a water quality sample was collected from each of the three tanks in order to determine if the sediment removal operations resulted in a decrease in tetrachloroethene concentrations in the tanks. Based on the results, the concentration of tetrachloroethene in the water in each storage tank was not reduced after completion of sediment removal activities. The concentration of tetrachloroethene in the three storage tanks after sediment removal ranged from 5.2 ug/1 to 5.6 ug/l, which is a negligible change compared to the concentration prior to cleaning activities. The concentration of tetrachloroethene in the northern tank after sediment removal was 5.3 ug/l in the primary sample and 5.6 ug/l in a duplicate sample, compared to the concentration of 5.0 ug/l(primary sample)and 5.3 ug/1(duplicate sample)prior to sediment removal as described above. The concentration of tetrachloroethene in the center tank after sediment removal was 5.2 ug/l, compared to the concentration of 5.3 ug/l prior to cleaning. The concentration of tetrachloroethene in the southern tank after sediment removal was 5.3 ug/l compared to the concentration of 5.6 ug/l prior to sediment removal. Based on these results,the removal of sediments from the tanks did not reduce the tetrachloroethene concentrations. Indoor Faucet Tetrachloroethene Concentrations ' After the completion of tank cleaning activities,a sample was collected from the same indoor faucet as was sampled during a previous sampling event at the facility. The indoor faucet sample yielded a tetrachloroethene concentration of 6.4 ug/l in a primary sample and a concentration of 6.7 ug/1 in a duplicate sample. A field blank sample was collected concurrently with the indoor faucet samples,and the field blank sample was non-detect for tetrachloroethene. A trip blank sample accompanied the faucet samples to the laboratory,and the trip blank sample was non-detect for tetrachloroethene. ' The concentrations of tetrachloroethene in the indoor faucet sample collected after completion of storage tank cleaning operations (6.4 ug/l in the primary sample and 6.7 ug/l in the duplicate sample) were similar to the concentration previously reported for the indoor faucet. The previous tetrachloroethene concentrations in the indoor faucet were 7.0 ug/1 in the primary sample and 7.2 ug/1 in a duplicate sample.