Remedial Action Report Construction Phase

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5.2 Former Senator Hotel (Areas 18, 21, and 22) Area 18 During construction activities on March 15, 1999, a 625-gallon UST (labeled UST-9) was encountered at approximately two feet below street grade in the northwest portion of the Courthouse Square property. Figure 6 shows the former location of UST-9. When discovered, the UST was completely full of product and water. Spencer Environmental of Portland, Oregon was retained to pump the liquids out of the tank using a vacuum truck. The liquids were transported to Spencer's facility for recycling. A copy of the recycling receipt is provided in Appendix F. A diesel odor was noted in soil near the fill port. Soil sample UST-9 was collected from the fill port area for NWTPH- HCID analysis with quantification. Figure 6 shows the location of the sample. On March 25, 1999, CJ Environmental removed UST-9. During decommissioning, diesel-impacted soil was observed below the UST. Remedial excavations in the UST-9 area were performed in two phases due to the construction schedule. A total of 540 tons of diesel-impacted soil was excavated from the UST-9 area for off-site disposal. Groundwater was not observed in the excavations. Soil samples UST9-BF 1, UST9-BF2, and UST9-BF3, collected from the contaminated soil removed from the remedial excavation, were analyzed for NWTPH-D~c. Confirmation samples UST9-1-12.0 through UST9-8-14.0 were collected from the bottom of the excavation and analyzed forNWTPH-Ds. In addition, soil samples UST9-6-13.5, UST9-7-13.0, and UST9-8-14.0 were analyzed for NWTPH-Gx since these samples were located in the vicinity of the gasoline impacted soil associated with Area 22 (described in "Area 22" of this section). Soil sample UST9-6-13.5 was also analyzed for BTEX. Figure 6 shows the location of the samples and the extent of contaminated soil removed from Area 18. Gasoline was detected at a concentration of 53.9 mg/kg in confirmation sample UST9-6-13.5, below the 80 mg/kg matrix cleanup level (Table 5). Diesel was detected at a concentration of 3,290 mg/kg in soil sample UST9-4-9.0. Based on this result, additional soil in the vicinity of UST9-4-9.0 was excavated and disposed off-site. Diesel was detected at a maximum concentration of 278 mg/kg in the remaining confirmation samples. BTEX was not detected in confirmation soil sample UST9-6- 13.5. On March 17, 1999, a 75-gallon UST (labeled UST-10) was encountered at approximately three feet below street grade in the northwest portion of the Courthouse Square property. Figure 6 shows the former location of UST-10. After the UST was removed, one soil sample (labeled UST-10) was collected from approximately six-inches beneath the tank for NWTPH-HCID analysis. No visual or olfactory evidence of contamination was noted in the soil surrounding the UST. Groundwater was not observed in the excavation. No petroleum hydrocarbons were detected in soil sample UST-10 (Table 5). Construction Phase - Remedial Actions - 12 - 4080600127 Courthouse Square November 9. 1999