Remedial Action Report Construction Phase

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Although groundwater was not observed in the Area 18 excavations, dewatering was performed from Sumps 2 and 6, located near Areas 18 and 22. Refer to "Area 22" of this section for details regarding water sampling in the vicinity of Area 18. Area 21 On April 26, 1999, excavation was performed in the location of a former boiler. No visual or olfactory evidence of contamination was noted in the soil surrounding the boiler. Soil sample 21-1- 16.0 was collected on the bottom of the excavation for NWTPH-HCID analysis. Groundwater was observed in the excavation. No evidence of contamination was observed on the groundwater. Based on field observations, ground water samples were not collected from the excavation. No petroleum hydrocarbons were detected in confirmation soil sample 21-1-16.0 (Table 2). Area 22 During construction activities on April 28, 1999, petroleum hydrocarbon-impacted soil was encountered during excavation in the northern portion of the former Senator Hotel building (Area 22). Based on information included in the ESA, the impacted area had been used as a garage between 1926 and 1950 (Century West 1997a). Soil sample 22-1-14.5 was collected from the impacted soil and analyzed for NWTPH-HCID with quantification and BTEX to characterize the contamination and evaluate disposal options. Based on the analytical results, approximately 1,393 tons of gasoline impacted soil ~~~ere removed from Area 22 for off-site disposal. Groundwater was observed in the Area 22 excavation. Soil samples 22-2-15.0 through 22-21-14.0 were collected from the Area 22 excavation and analyzed for NWTPH-Gx and BTEX. In addition, soil sample 22-10-15.5 was analyzed for EDB, EDC, and lead. Soil samples 22-8-15.0, 22-9-15.5, 22-12-15.5, 22-13-14.0, and 22-16-1 ~.5 through 22-21-14.0 were also analyzed for NWTPH-Dx since the impacted soil in Areas 18 and 22 overlapped. Soil samples 22-19-13.5 through 22-21-14.0 were also analyzed for PAHs. Soil samples 22-SP-1 through 22-SP-3, collected from contaminated soil removed from the remedial excavation, were analyzed for NWTPH-Gx and BTEX. Figure 6 shows the location of the samples and the extent of contaminated soil removed from Area 22. Gasoline was detected at concentrations ranging from 103 mg/kg to 2,710 mg/kg in confirmation soil samples 22-1-14.5, 22-4-15.5, 22-5-15.~, 22-10-15.5, 22-11-15.0, and 22-19-13.5, exceeding the matrix cleanup level (Table 6). However, BTEX results for these samples were either not detected or detected at concentrations significantly below the applicable RBCA Tier I RBSLs. Diesel was detected at concentrations of 1,540 mg/kg, 16,900 mg/kg, and 1,450 mg/kg in confirmation soil samples 22-13-14.0, 22-19-13.5, and 22-20-14.0, respectively. These concentrations exceed the 500 mg/kg matrix cleanup level. However, the PAH concentrations for these samples were below the Construction Phase - Remedial Actions - l3 - 4080600127 Courthouse Square November 9, 1999