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Corrective Action Closure Report June 11, 1993 BP Chemical Facility (SJCEHD Site Code 2042) Page 2 feet deep) and collecting soil samples for chemical analysis. Because groundwater was not encountered during the drilling of those soil borings, groundwater monitoring wells were not constructed, and groundwater samples were not collected. Sol[ samples were collected at five-foot intervals in each boring. The soil samples collected at 21 and 39.5 feet below the ground surface were submitted for chemical testing. No detectable concentrations of total petroleum hydrocarbons-as-gasoline (TPH-G); benzene, toluene, ethylbenzene, and xylene (BTEX); ethylene dibromide (EDB); or organic lead were reported in the samples tested. Additional details of the subsurface investigation were presented in the Preliminary Soil Assessment report (dated April 26, 1992). The results of the subsurface assessment conducted by BP Chemical at the time the underground storage tank was removed indicated that the soil immediately adjacent to the former UST contained detectable concentrations of petroleum fuel constituents. The results of the subsequent investigation by Groundwater Technology indicated that the petroleum hydrocarbons in the soil were limited to the area immediately adjacent to the former tank location. Because soil samples from 21 and 39.5 feet below the ground surface did not contain detectable concentrations of petroleum hydrocarbons; and because the groundwater is greater than 40 feet below the ground surface, it appears that the groundwater beneath the BP Chemical facility has not been affected by the operation and storage of petroleum fuel hydrocarbons. Corrective Action Work Plan Because petroleum fuel hydrocarbons were detected in soil from the former UST excavation, Groundwater Technology recommended (report dated April 28, 1992) the following: ■ Overexcavation of the tank pit to remove soil affected by petroleum hydrocarbons; ■ Collect closure confirmation samples from the excavation sidewalls and excavation bottom; and ■ Backfill the excavation. In a letter dated June 17, 1992, the SJCEHD concurred with the recommendations for the overexcavation as an appropriate remedial/corrective action. The SJCEHD requested the preparation and submittal of a remedial work plan. Groundwater Technology prepared a Corrective Action Work Plan (dated October 20, 1992) which described the planned soil remediation (overexcavation) activities at the BP Chemical facility. Because these activities are defined as Corrective Actions according to the California Code of Regulations (CCR) Title 23, Division 3, Chapter 16, Article 11, the Corrective Action Work Plan was submitted for public notification by the SJCEHD. No comments were received during the public review period, and the tasks defined in the Corrective Action Work Plan were performed. CACR0074.0K GROUNDWATER �. TECHNOLOGY, INC.