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� i • <br /> UNDERGROUND STORAGE TANK CLOSURE R610ff <br /> 1605 South EI Dorado Street Stockton California <br /> On December 17, 1991, the top-of-casing well elevations for MW-1, MW-2, and MW-3 <br /> were resurveyed by Tom O Morrow, Inc , of West Sacramento, California <br /> 2.3 Adjacent Land Uses <br />' The area is predominantly occupied by commercial buildings, with a dry cleaners <br />' 0 25 mile south of the site <br /> 2 4 Generalized Geology and Hydrogeology <br /> The alluvium beneath the site is of the Quaternary Age Modesto Formation The Modesto <br /> Formation is underlain by the nonmarine Tertiary Tehama Formation Within the vicinity <br />' of the site, the Tehama formation reportedly vanes in thickness up to 3,000 feet The <br /> nearest body of water, Mormon Slough, is approximately 1 mile north of the site <br /> (Figure 1) <br />' Based on data collected on April 22, 1992, depth to groundwater is approximately 45 feet <br /> below surface The estimated groundwater flow direction is to the east <br /> 3 0 RESULTS <br /> I3.1 Soil Conditions <br />' The subsurface soils in the former tank basin and former product line trenches consisted <br /> of clayey sand fill material from 3 to 12 feet below surface Below the fill, sediments <br /> consisted mainly of silty clays No groundwater was encountered while excavating J <br />' 3 2 Removed Underground Storage Tanks and Associated Piping <br />' Prior to removal, the USTs and associated product piping were um ed out and tri le- <br /> -uasgb wA water After removal of the rmsate from the tanks, the USTs were degassed <br /> with liquid nitrogen and approved for removal by the SJCPHS/EHD and the Stockton Fire <br />' Department The steel USTs were visually inspected upon removal and were observed <br /> to be in fair condition with slight corrosion The USTs were manifested and hauled by <br />' Erickson, Inc , to their facility in Richmond, California The uniform hazardous waste <br /> manifests are included in Appendix C <br />' Aegis personnel collected two soil samples beneath each former UST, and one sample <br /> every 20 linear feet beneath the former product piping runs, 2 feet into native soil <br /> (Figure 3) <br />' 91-044A TCF 3 <br />