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_ R&B Trucking Project No.01-37.1.1 March 27,1990 Page 2 During the excavation of the tanks, Mr. Barenchi had the contractor extend the excavation both vertically and horizontally to remove the contaminated soil. The soil beneath the ` contaminated areas around tanks 1 and 5(Figure 3)was excavated to a depth of 15 or 16 feet. At that point, ground water began filling in the excavation. At the time of excavation the water table was depressed to 15.5 to 16 feet from construction dewatering operations occuring just to the north of the site. This soil from the bottom of the excavation (approximately 5 to 7 cubic yards) was stockpiled separately from the rest of the excavated soil. On 3 January 1990,Geological Technics collected two samples from this stockpile and submitted them to Chromalab in San — Ramon via GeoAnalytical Laboratories in Modesto. The samples were collected 18 inches beneath the surface of the stockpile and after being composited were tested for TEPH. In August,1989,Geological Technics(GTI)was contracted to perform a Phase I Site Assessment. GTI proposed in the Work Plan,dated 20 September 1989,to install one monitoring well midway in the former tank cluster adjacent to the position once occupied by tank no.5. In response to comments in the letter dated 12 October 1989 by Tom Peltier(CRWQCB),GTI prepared addendum no. 1,dated 27 November 1989. This addendum responded to Mr.Peltier's concern that a minimum of three monitoring wells be installed instead of the single well proposed. These concerns were addressed by describing the placement and construction of the two additional wells. Upon reevaluating the project,GTI issued addendum no. 2,dated 3 January 1990. Addendum no.2 modified the first addendum by altering the placement of the two additional monitoring wells. GTI proposed that the two additional wells be placed to the south and west of the tank excavation. Also included was a schematic diagram illustrating the construction of the wells. The reasoning behind the decision to place the wells as listed was to have all three wells at a close distance from the tank to evaluate the water surrounding the tanks where the known soil contamination was observed. In addition to the proposal and addendums prepared by our firm,a full site review was performed. The scope of the site review included visually observing obvious surface features that would indicate a potentially contaminated area. These surface features included discoloration,odors,and unexpected lack or profusion of vegetation. Mr.Barenchi was also questioned as to other potential source areas or business practices that may have led to releases of other potentially hazardous chemicals. Since the time of the waste oil tank removal, we observed that the storage of waste oil in above ground containers had not been a cause for detectable site contamination(no evidence of an overturned drum or gross spillage was visually detected). A complete record search was not performed since the owner of the property indicated that no — known hazardous waste was stored on site. However,a review of the records at The City of Tracy was performed over the phone and a historic search of available air photos was performed.