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J � s p August 27, 1996 Page 2 the western portion of the site. The waste oil tank is of single wall steel construction with a 550-gallon capacity and is located northeast of the former station building. PREVIOUS INVESTIGATIONS In February 1995, The MARK Group, Inc:(MARK)conducted a Phase I Environmental Site Assessment(ESA). The ESA included a field reconnaissance of the site and adjacent properties, literature reviews regarding historical land-use and hydrogeology, interviews, and review of governmental environmental databases. Based on the results of the ESA, further environmental investigation was recommended(MARK, February 1995). In April 1995, MARK conducted a preliminary subsurface investigation which included the drilling of six exploratory borings. The six borings included one adjacent to the former waste oil tank, one at the location of the former hydraulic hoist, one at the location of the former pump island, one adjacent to the location of the former product lines,and two at the location of the former gasoline USTs. Total petroleum hydrocarbons calculated as gasoline(TPH-g), and benzene,toluene,ethylbenzene, and xylenes(BTEX compounds)were detected at 3,feet below ground surface(bgs)within the former UST excavation backfill. TPH-g and benzene were detected at concentrations of 170 parts per million(ppm)and 0.051 ppm,respectively. No TPH-g or BTEX compounds were detected.in any of the other samples collected(MARK, April , 1995). Subsurface materials encountered during drilling included near-surface clayey fill and clayey fill with concrete debris within the former UST excavation backfill, and native soil consisting of clay. Groundwater was not encountered and based on regional information groundwater flow is estimated to be to the southwest at a depth in excess of 50 feet(MARK,April 1995). Geophysical,Survey Investigation A geophysical survey which included the use of ground penetrating radar(GPR) and magnetometer technologies, was conducted at the site on June 18, 1996,to evaluate the possible existence of remaining subsurface lines, USTs,or other underground structures. The results of this investigation suggested the presence of the waste oil tank, however, no other subsurface structures (other USTs,product lines, etc.)were identified at the site. The geophysical report issued July 10, 1996 by NORCAL Geophysical Consultants, Inc. (NORCAL) is included as Attachment B. PROPOSED SCOPE OF WORK The proposed scope of work includes the removal of any remaining facilities associated with the former Chevron Service Station and to confirm the presence of and evaluate the extent of gasoline hydrocarbons in soil at the subject site. All applicable permits for the 9200391 A/W PLAN