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F , Quarterly Summa Report First Quarter 1999 Former Unocal Service Station# 0123 1034 Central Avenue Tracy, California BACKGROUND, The site was reportedly an operating Unocal service station from 1920 through 1962. Two underground storage tank (UST) complexes have existed at the site. A cluster of three UST's located at the northern property boundary adjacent tb the 11`h Street site were identified as "abandoned" and a second.cluster of three tanks to tIhe south were identified as active UST's. The property was purchased by Bank of America and the service station was demolished in 1962. The site is currently an asphalt-paved parking lot owned by and servicing the Wells Fargo Bank located immediately to the south. A limited silbsurface investigation was conducted by LMS.. As requested by the an Joaquin County Public Health Services,Unocal submitted a work plan to perform a soil and groundwater investigation. Nine soil borings and three groundwater monitoring wells were installed in may 1995. Exploratory test pitting was performed and two abandoned UST's were encountlered at the northern property boundary, beneath the 11th street sidewalk. A report documenting the soil and groundwater, investigation was submitted to Unocal and San Joaquin County in December 1995. On September 6, 1996, Unocal submitted a corrective action plan to address hydrocarbon impacted soils that may be encountered during removal of the UST's. Two abandoned 550- gallon UST's were removed in November 1996. A third UST was encountered during the removal activities and was properly abandoned in place by grout injection. One groundwater monitoring well (U-4) was installed in December 1996 in the location of he removed UST's to evaluate soil and groundwater quality. Two groundwater monitoring wells (U-S, upgradient and U-6, downgradient)were installed an October 6, 1998. 9100172B%IQSR99 2 March 16, 1999