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WATERWORK`" .. GEOCHEMICAL•GEOTECHNICAL•ENVIRONMENTAL February 15, 1990 aw a n� FEB2 1 "^^� Ms. Darlene Reuss ENVIRONMENTAL HEALTH San Joaquin Public Health Services PERMIT/SERVICES Environmental Health Division P.O. Box 2009 Stockton, CA 95201 Re: De Rollo Mazda, 308 Gran>*-Street, Stockton CA Dear Darlene: This letter is provided as an addendum to the workplan outlined in Waterworks Preliminary Report dated October 11, 1989 for the above referenced site (Figure 1 ) . Concentrations of 470 parts per million (ppm) total hydrocarbons and 0.05, 1.2, 1.9 and 18 ppm of benzene, toluene, ethylbenzene and xylene were detected in the soil sample collected at a depth of 15 feet under the north end of the gasoline tank B (Figure 1 ) . A vertical soil boring drilled adjacent to this sample point did not record gasoline hydrocarbons above method detection limits in samples collected at 20. 5, 25 . 5 and 30. 5 feet below grade (Table 1 ) . Groundwater was encountered at approximately 31 feet below grade. We propose re-excavation of this area to remove the gasoline contaminated soils which are a potential source for groundwater contamination. An amendment to the workplan which includes removal of these gasoline contaminated soils is presented below. Amendment to Proposed Workplan: To remove the remaining gasoline contaminated soils from the north end of this tank pit, WaterWork proposes to re-excavate this end of the pit to a depth of 15 to 25 feet. The following scope of work is proposed: 1 . Re-excavate the north wall and floor of tank pit B. Excavation will be continued laterally and vertically until visual and PID screening indicate that the contamination has been removed. This field area will be excavated to a maximum depth of 25 feet. 1710 MAIN STREET • ESCALOR CA 95320 • (209) 838-3507 FRESNO,CA(209) 222-3495 • RENO, NV(702) 788-6830