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-paq <br /> _ _11 _ <br /> a , <br /> ��—�—� <br /> ® App/ird GedSy.'^s �/Iiu�' 4191-E Power Inn Road, Sacramento, CA 9826 (916)452.2901 <br /> 0 FREMONT o COSTA MESA •SACRAMENTO • HOUSTON <br /> July 8, 196r <br /> 070STROS <br /> AGS Job No. 38032•-1 <br /> Mr. Tim Ross. <br /> ® UNOCAL Corporation <br /> 2175 North California Boulevard <br /> Suite 650 <br /> Walnut Creek, California 94596 <br /> Subject: Executive summary of report on subsurface environmental <br /> investigation and removal of underground storage tanks <br /> at UNOCAL Service Station No. 6981, 4707 Pacific <br /> Avenue, Stockton, California. <br /> Mr. Ross: <br /> This report summarizes Applied GeoSystems' evaluation of soil <br /> ta_ contamination at the above-referenced site. Applied GeoSystems <br /> was requested to perform this work because hydrocarbon <br /> contamination was detected during installation of a gasoline- <br /> blending system at the site. Applied GeoSystems initially <br /> collected soil samples in the vicinity of the dispenser islands, <br /> as specified by UNOCAL personnel; analysis-of these soil samples <br /> indicated that the soil was contaminated with hydrocarbons. <br /> UNOCAL Corporation subsequently contracted with Town & Country <br /> Contractors of Sacramento, California, to remove three <br /> underground gasoline storage tanks from the site and acquire <br /> appropriate permits. Mr. Harlin Knoll of the San Joaquin Local <br /> V Health District was present during removal of the tanks and soil <br /> sampling. Analytical results of s611 samples collected beneath <br /> the former tanks indicated contamination of the soil: had <br /> occurred. In response to these results, the tank ca';rity was <br /> further excavated to approximately 22 .feet below grade. <br /> Analytical results of soil samples obtained from 22 feet below <br /> grade indicate that soil contamination remains in the center and <br /> northeastern portions of the tank cavity beyond the reach of the <br /> equipment used. With the concurrence of the. San Joaquin Local <br /> Health District and the California Regional Water Quality Control <br /> --- -----Board,-Central—valley--Regi on --the--tank-Cavity--was-backfilled-with--- - <br /> pea gravel to approximately 15 feet below grade, a 15 inch <br /> diameter conductor casing was placed in the center of the cavity <br />