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Treadvvell&Wlo 1 1 June 2004 Project No. 2597.10 Mr. John Jackson San Joaquin County Environmental Health Department 304 E. Weber Avenue,Third Floor Stockton, CA 95202-2708 Subject: Confirmation Soil Sampling UST Removal Activities Former Carando Machine Shop (420 N.Madison Street) North Shore Parcel Stockton, California Dear Mr. Jackson: Treadwell &Rollo, Inc.have prepared this letter to document confirmation soil sampling results and present the methodologies used during the removal of three discovered underground storage tank(UST)conducted on 28 April 2004 at the subject site(Figure 1). The former Carando Machine Shop was located at 420 Madison Street in Stockton, California. The UST removal activities were performed under the direction of representatives of the San Joaquin County Environmental Health Department(SJCEHD). The removal of three USTs at the site was performed by Jim Thorpe Oil, Inc(Thorpe), a licensed contractor,who acquired the appropriate permits, removed and arranged for the disposal of the USTs. As presented in Treadwell&Rollo's Soil and Groundwater Investigation report dated 12 April 2004,historic aerial photographs and Sanborn maps identified a gasoline service station on the southeast corner of the intersection of Madison Street and West Fremont Street. These records indicate that the service station was present at the site from at least 1950 until the late 1960's. No records for the installation or removal of the station's USTs have been identified. Soil samples collected by Treadwell&Rollo and others have reported concentrations of total petroleum hydrocarbons as gasoline(TPHg)that range up to 12,000 milligrams per kilograms (mg/kg)in the immediate vicinity of the discovered USTs. In the Soil and Groundwater Investigation report, excavation to a depth of 23 feet below ground surface was proposed.to remove elevated TPH concentrations in soil in the area where the three USTs were eventually found. This remedial action was approved by the SJCEHD letters dated 16 and 20 April 2004. On 28 April 2004, two steel,single-walled,USTs were discovered during the removal of surface concrete around the proposed soil excavation area(Figure 2). The concrete removal work was halted and the USTs investigated. The Treadwell &Rollo field geologist notified the City, Stockton Fire Department(SFD), SJCEHD, and California Department of Toxics Substance Control. The USTs appeared to be a 550-gallon(UST#1)and 350-gallon(UST#2)tank. The USTs were located under the sidewalk along West Fremont Street(Figure 2),with the long axis of the tanks perpendicular to sidewalk. The top of the USTs were approximately 4 feet below the ground surface. The upper portion of the southern end of each UST was punctured by the Treadwell&Rollo,Inc.Environmental&Geotechnical Consultants 555 Montgomery Street,Suite 1300,San Francisco,CA 94111 Telephone(415)955-9040.Facsimile(415)955.9041