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Work Plan—Byron Road, Tracy,California June 16,2003 06-6102-00-2931-030 Page 5 The SJCEHD granted a "No Further Action" letter dated September 30, 1996. Based on the letter, the RWQCB concurred and groundwater-monitoring wells associated with the Monterosso property were destroyed. Cintra Property In November 1989, Harlan Tait Associates (HTA) prepared a site history of the Toste/Schwilke property (Cintra property). The site history indicated a moderate to high potential of petroleum contamination to soil and groundwater from existing underground storage tanks or from the former pipelines that carried crude oil and bunker C fuel oil. HTA recommended additional subsurface exploration of the property be performed. In December 1992, 19 soil borings were advanced and soil samples collected by RESNA. The soil borings were advanced to depths between 5 and 15 feet bgs. Select soil samples were submitted for analyses of O&G and BTEX constituents. Petroleum hydrocarbons were not detected in any of the soil samples analyzed. An additional grab groundwater sample was collected and contained low concentrations of toluene(13 pg/L), ethylbenzene(3.4 pg/L),and xylenes(22 µg/L). In November 1997, Geomatrix supervised the advancement of three soil borings to an approximate depth of 16 feet bgs along the southern property boundary. Three soil samples were collected from the borings and analyzed for TPHc, BTEX,and PAHs. Grab groundwater samples were also collected from the three borings and analyzed for the BTEX, PAH's, TPHg, and TPHd. The grab groundwater samples were also analyzed for methyl tertiary butyl ether(MTBE). Petroleum hydrocarbons were not detected in either the soil or grab groundwater samples analyzed. The SJCEHD granted a"No Further Action"letter dated January 16, 1998. Dividend Property The Dividend property is located north of Byron Road and is split into two parcels. The north parcel is located north of the Interstate 205 overpass and the south parcel is located south of the overpass. In November 1989, Dames and Moore collected groundwater from eight shallow soil borings and nine shallow test pits (maximum depth 6 feet bgs) as well as ten random surface locations throughout the entire property. Soil samples from two of the test pits that contained visibly contaminated soils, and two that did not contain visible contamination, were collected for analyses. Soil samples from the test pits were analyzed for TPHd and BTEX. BTEX compounds were not present above detection levels, but TPHd was detected in all shallow soils collected with a maximum concentration of 2,400 mg/kg. Ten surface soil samples were collected from the upper six inches of ground surface using a hand-held device. Surface soils were analyzed for pesticides and PCBs; these analytes were not present above detection levels. Groundwater samples were analyzed for TPHd and BTEX. Petroleum hydrocarbons were not detected in the groundwater samples analyzed. Toxic Technology Inc. (TTI) conducted a soil and groundwater investigation of the north parcel of the Dividend property in June 1991. The investigation included the installation of seven groundwater- monitoring wells, and collection of soil and groundwater samples for analyses. Petroleum hydrocarbons were detected in soil at five locations ranging in depths from 6 to 14 feet bgs. Petroleum hydrocarbons were also detected in one groundwater sample. K:C VX-O VP\RO W—SITES\westsidechannel\draftworkplan.doc