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is �f The site's station building and garage were demolished in December 1994 to facilitate corrective action activities including the removal of hydrocarbon contaminated soil which was present beneath the station building The demolition of the station building was requested in PHS/EHD correspondence dated July 7, 1994 A required demolition asbestos survey conducted previously on the station building, determined the presence of asbestos containing materials E T Abatement, of Modesto, California, properly removed and disposed of the site's suspected asbestos containing materials on November 11, 1994 In February 1995, Smith Environmental personnel supervised the excavation of approximately 1,400 cubic yards of soil from the vicinity of the former underground storage tanks Approximately 10,000 gallons of groundwater was pumped from the open excavation into an on- site Baker Tank The excavation pit was subsequently backfilled with imported self compacting material Excavation activities are discussed in detail in Smith Environmental's Excavation Summary Report, dated October 24, 1995 On November 25, 1996, Smith Technology personnel supervised the advancement of eight soil borings at the subject site The soil borings were advanced to define the extent of petroleum hydrocarbon contamination in soil and groundwater in the northern portion of the site Results of the subsurface investigation will be summarized a forthcoming report On December 2, 1996, Smith Technology personnel began the construction of a soil aeration cell in accordance with a letter workplan submitted to PHS/EHD and an authority to construct issued iby the San Joaquin Valley Unified Air Pollution Control District Approximately 1,200 cubic yards of stockpiled soil was placed on visquene plastic, with a maximum soil height of three feet, to promote aeration of the hydrocarbon impacted soil QUARTERLY MONITORING ACTIVITIES Smith Technology performed quarterly groundwater monitoring and sampling on March 25, 1997 Field work included measuring the depth-to-water in wells MW I through MW6 and purging and sampling the water from wells MW2 through MW6 and the nearby community well (Thornton 42) The samples were analyzed for the presence of dissolved petroleum hydrocarbons Depth to water measurements collected on March 25, 1997 from monitoring wells MW1 through MW6 indicate the water table has risen to the highest recorded levels since the project groundwater monitoring program was initiated in November 1991 The water table elevation has increased an average of approximately 5 12 feet since the last monitoring event in December 1996 The current groundwater elevation, 4 5 feet below the top of the well casings, is above the top of the screen, approximately 8 to 10 feet below the top of the well casings Because of the extremely high groundwater elevation, the petroleum hydrocarbon concentrations in groundwater . at this time are representative of the screen interval and not the groundwater table Groundwater w 1943261quadlyllgr-1997 doc 2 • Sr"H