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�_ Vzj - A S S O C I A T E S I N C gasoline USTs contained detectable concentrations of petroleum hydrocarbon constituents. The excavations were subsequently backfilled. In October 1997, an ATC geologist supervised the advancement of one soil boring to 31 feet bgs, one soil boring to 26 feet bgs, and five soil borings to 20 feet bgs. Soil borings SB I through SB6 were placed in the vicinity of the former 10,000-gallon UST and soil boring SB7 was placed in the vicinity of the forte 750-gallon UST. A site plan with soil boring locations is shown on Figure 2. The borings were advanced using a truck mounted Geoprobe® narrow diameter rig employing direct push technology. Soil and grab groundwater samples collected from the vicinity of the former 10,000-gallon UST contained elevated concentrations of petroleum hydrocarbons. Field activities were summarized in ATC's Summary Report of Subsurface Investigation, dated November 24, 1997. In August 1998, ATC personnel supervised the advancement of three soil borings at the site. Drilling was performed using hollow stem auger. In accordance with the approved workplan, the soil borings were completed as groundwater monitoring wells MW1, MW2, and MW3. Soil samples contained detectable concentrations of petroleum hydrocarbons. The groundwater monitoring wells were subsequently developed and the groundwater samples contained detectable concentrations of total petroleum hydrocarbons as diesel (TPHd). Field activities were summarized in ATC's Summary Report of Additional Subsurface Investigation, dated October 19, 1998. SCOPE OF WORK Plannine and Permits ATC has completed the soil boring permit application for the proposed subsurface investigation. The permit application and associated fees (check no. 243) are attached to this workplan. ATC is in the process of obtaining access agreements from the Burlington North Santa Fe Railroad to install soil borings in the Burlington North Santa Fe Right of Way. At the request of Mr. Jeff Wong of PHS/EHD, ATCis in the process of obtaining an encroachment permit from the City of Stockton to install soil borings in the City of Stockton Right oay aroun arbor Street to eac d south and southwest of the Burlington North Santa Fe Railroad. The advancement of soil borings in the City of Stockton Right of Way is a contingency plan. If the soil borings placed in the Burlington North Santa Fe Railroad Right of Way appear impacted with petroleum hydrocarbons, ATC will advance soil borings further south and southwest of the railroad tracks in the City of Stockton's Right of Way for Harbor Street. 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 A625001reponslwkph.doc 2