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1CVV Q A S S O C I A T E S I N C On July 24, 1997, to investigate the extent of residual soil contamination at the site, a total of six soil borings were advanced to depths ranging from approximately 16 to 31 feet below ground .surface (bgs). Detectable concentrations of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), and benzene, toluene, ethylbenzene, and xylenes (BTEX) were observed in soil samples collected from the site. The distribution of petroleum constituents beneath the site has been essentially defined and appears to be limited laterally to the immediate vicinity of the former tank pit. The highest concentrations were reported between 10 and 20 feet bgs and generally attenuate rapidly with depth. Only low concentrations of toluene (0.064 mg/kg) and xylenes (0.012 mg/kg) were detected at approximately 30 feet bgs in one boring, the maximum depth explored. Attempts were made to further advance the Geoprobe unit in several of the borings, however probe refusal was encountered at depths ranging from approximately 16 to 30 feet bgs due to the hardness of the formation. The results of the subsurface investigation were summarized in Smith Technology's "Summary Report, Subsurface Investigation", dated December 22, 1997. In April 1999, at the request of PHS/EHD, ATC completed a receptor survey for the subject property. ATC reviewed PHS/EHD groundwater well construction logs, Department of Water Resources (DWR) groundwater well construction logs, and conducted a site walk in the vicinity of the site to identify any groundwater wells located within a 2,000-foot radius of the site. This • survey revealed fourteen wells located within approximately 2,000 feet of the site. The closest of these wells is located approximately 800 feet upgradient of the project site. The receptor survey findings are summarized in ATC's "Well Survey", dated April 9, 1999. In October 1999, ATC submitted a"Closure Report" for the site that evaluated available data and requested No Further Action (NFA). PHS/EHS subsequently submitted a "Case Closure Summary" to California Regional Water Quality Control Board (RWQCB) for site closure. However, a "Nonoccurrence with No Further Action Required' letter dated February 3, 2000 was issued by the RWQCB. PHS/EHD, in their correspondence dated February 11, 2000, requested additional work be performed to investigate the potential for groundwater contamination at the subject site. SCOPE OF WORK Workplan Preparation ATC has completed the soil boring permit application for the proposed subsurface investigation. The permit application and associated fees are attached to this workplan. ATC will also schedule field personnel and equipment, notify Underground Service Alert to locate underground utilities as required, and perform any other necessary field preparation and job start-up activities. w:1920541repoM\wkp-boring.dor 2