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NAPL Area 1
Figure 5 presents the TCE concentrations in groundwater in NAPL Area 1 from the interior monitoring wells before, immediately after, 10 months and 2 years following ERH. Two years following the ERH remediation in NAPL Area 1, average TCE concentrations in groundwater continued to decline significantly from approximately a 89% reduction post ERH to a 99.5% reduction in the interior monitoring wells two years post ERH.
Figure 6 illustrates the average TCE concentrations in soil pre, post and nearly two years following ERH in NAPL Area 1. Immediately following ERH (Hot Soil Sample Data) the average TCE soil concentrations were reduced by 99.87% when compared to the pre-ERH data. Almost two years later (April 2006), the average TCE concentrations in soil had declined by 99.97% when compared to the pre-ERH data. Sixty-two percent of the soil samples were non-detect (ND) for TCE. Soil samples from NAPL Area 1 were not analyzed for DCE at the end of the ERH remediation.
| COC | Pre-ERH |
End-ERH Average(ug/kg) |
Percent Reduction |
April 2006 Average(ug/kg) |
Percent Reduction |
Percent ND |
|---|---|---|---|---|---|---|
| TCE | 94,407 | 123 | 99.87% | 29 | 99.97% | 62% |
| DCE | 7,233 | 11 | 99.84% |
Figure 7 illustrates the TCE concentrations in groundwater pre, post, and 10 months following ERH in the exterior monitoring wells in NAPL Area 1. The data shows that even ten months following ERH, TCE concentrations in the exterior groundwater wells continued to decline. The average reduction of TCE concentration in groundwater was 98% when compared to the pre-ERH data.
A total of 95,029 lbs of mass was removed in NAPL Area 1. About 93% of the total mass was total petroleum hydrocarbons (TPH), about 6% was TCE and the remaining 1% was cis DCE and vinyl chloride.