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2132 Mariposa Rd., Stockton <br /> Page 2 <br /> the contamination was undefined so three more MWs (MW4P-MW6P)were installed in <br /> September 1995 with screen intervals of 55-85 feet, 55-85 feet, and 54-84 feet <br /> respectively. <br /> To date, nine MWs and a soil vapor extraction well have been installed, five MWs and a <br /> vapor extraction well installed on-site and four MWs installed off-site. Water samples <br /> from all the MWs have had detections of gasoline, gasoline constituents and gasoline <br /> additives including MTBE, TBA, DIPE and 1,2- DCA. <br /> On 17 November 1997 three 12,000-gallon gasoline and one 3,000-gallon diesel USTs <br /> were removed from the site. Soil samples were collected at that time and most all the <br /> results were positive for gasoline and gasoline constituents. Three new USTs were <br /> reinstalled in the excavation. <br /> The vertical and lateral extent of the soil and groundwater contamination remains <br /> undefined. Although, soil samples were collected during installation of the monitoring <br /> wells, the soil samples collected from MW S-1 (well closest to the UST area) below 15 <br /> feet were not analyzed. Analysis of the soil samples from the other wells evidenced low <br /> levels of contamination. The soil samples collected beneath the UST's, at 15 feet, when <br /> they were removed in 1997, had higher levels of contamination and there has been no <br /> investigation of the soil since that time. Therefore, the vertical extent of soil <br /> contamination in the area of the former UST's is not defined, as well as the lateral <br /> extent. Further soil and groundwater assessment is required to determine the full extent <br /> of the contamination. <br /> A work plan proposing an investigation to determine the extent of the soil and <br /> groundwater contamination and evaluate feasible remedial alternatives, an EHD well <br /> permit application(s), and permit fees are to be submitted to EHD by 1 August 2007. <br /> If you have any further questions regarding this matter, contact Harlin Knoll at (209) 468- <br /> 3442. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Aa-,_ �� <br /> Harlin Knoll, Senior REHS Margaret Lagono, REHS <br /> LOP/Site Mitigation Unit IV Program Coordinator Unit IV <br /> Cc: SWRCB-Cleanup Fund <br /> CVRWQCB-James Barton <br />