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Stantec May 6, 2009 Page 2 of 5 owned or operated underground storage tanks (USTs) or associated gasoline fueling equipment at the site. The Exxon gas station operated from approximately 1971 to 1991. Historical environmental impacts associated with the former Exxon gas station are summarized below: Engineering-Science, Inc. (ESI) installed three groundwater monitoring wells in March 1991. Soil samples collected during the well installation were below laboratory detection limits, except for the sample collected from SB-02, which contained detectable concentrations of ethylbenzene, total xylenes, and total petroleum hydrocarbons as gasoline (TPHg). The groundwater samples collected from MW-1 and MW-3 during three events in 1991 did not contain detectable levels of benzene, toluene, ethylbenzene and xylenes (BTEX) or TPHg. The groundwater samples collected from MW-2 contained detectable levels of BTEX and TPHg. (ESI. Final Report for Initial Site Investigation. April 1991). In June 1991, Artesian Environmental Consultants, Inc. (Artesian) conducted additional subsurface investigation to determine the vertical and lateral extent of hydrocarbons in the soil and groundwater. Seven soil borings were drilled, and three of the borings were advanced as groundwater monitoring wells. (Artesian. Phase I/ Subsurface Investigation. July 1991). In October 1991, the Exxon gas station building was demolished, and the USTs, fuel dispensers, and associated piping were removed. The four USTs at the former Exxon gas station included one 1,000 gallon used oil UST, one 6,000 gallon gasoline UST, one 8,000 gallon gasoline UST, and one 10,000 gallon gasoline UST. During the UST removal activities, soil samples were collected beneath the former USTs, the waste oil UST, and beneath the associated product piping. Soil samples collected indicated that soil in the vicinity of the dispensers and USTs was impacted with TPHg and BTEX concentrations. During the UST and fuel system removal activities, approximately 450 to 500 cubic yards of impacted soil was removed and disposed of. (Artesian. Tank Removal Report. December 1991). In November 1991, monitoring wells MW-1 and MW-2 were properly destroyed by a licensed driller under the supervision of Artesian. Upon completion of the well destruction, approximately 1,296 cubic yards of additional soil was overexcavated in April and May 1992. (Artesian. Soil Remediation Report. July 1992). In July 1993, Delta Environmental Consultants, Inc. (Delta) drilled eight soil borings to assess the lateral and vertical extent of possible residual petroleum hydrocarbons in the soil in the eastern portion of the site. (Delta. Soil Investigation Report. September 14, 1993). Quarterly groundwater monitoring occurred from March 1991 to April 1996. At the time of Delta's Site Closure Request Report, dated September 18, 1996, Delta calculated that the total volume of liquid-phase petroleum hydrocarbons as gasoline remaining in the soil beneath the site was approximately 2.5 gallons and the amount of dissolved benzene in the soil was approximately 0.0019 gallons. Delta estimated that the amount of dissolved benzene in groundwater was negligible, and the amount of dissolved TPHg was less than 0.008 gallons in groundwater. Additionally, groundwater analytical results were below the laboratory limits of detection in the four existing groundwater monitoring wells for four consecutive quarters for TPHg and BTEX. The case was granted regulatory closure by the SJCEHD in November 1996. 14113 Soil and Groundwater Assessment Results.doc