SITE INFORMATION AND CORRESPONDENCE

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i CHRONOLOGY 22700 HIGHWAY 99, RIPON 01/12/88 A soil sample was collected beneath a 500 gallon gasoline underground storage tank (UST) that was previously closed in place at the site. The analytical results of that soil sample were non-detect for contaminants and no further action was required of that UST. 04/14/95 A 4000 gallon diesel UST was removed from the site and 2 soil samples were collected, the results showed diesel contamination. 02/10/97 The site was placed in the Local Oversight Program. 04/29/97 A work plan for 4 soil borings to further investigate the contamination. 05/09/97 Soil borings B1,132, B3, B4 were completed. Grab groundwater and soil samples were collected. High levels of diesel contamination were found in the samples from 131 and B2, which were at the ends of the former diesel UST location. B3 was near the closed in place gas UST and the analytical results for gasoline were non detect_ 05/29/97 Preliminary Site Investigation Report Route 99/Jack Tone Road Interchange Reconstruction Project includes information from 519197 work. 04/21/98 A work plan for 6 soil borings, 3 of which are to be completed as monitoring wells. 5128-29198 Monitoring wells MW1, MW2, MW3 installed and soil borings SB5, SB6, SB7 (20' deep) completed. MW 1 and MW3 screen interval 10 to 25 feet. MW2 screen interval 8 to 23 feet. Soil from S137, drilled in former diesel UST area, had diesel at 15 and 20 feet. Groundwater flow direction is towards Highway 99. MW1 evidenced diesel contamination. MW2 and MW3 were non detect for contaminants. 07/17/98 Environmental Site Investigation Report on May 1998 work. 09/28/98 A work plan for 5 geoprobes to define the lateral and vertical extent of contamination and to propose excavation of soil from the former diesel UST location.