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F <br /> EXECUTIVE SUMMARY <br /> l <br /> 510 North Main Street, Manteca, CA <br /> The subject property, 510 North Main Street, is a 1 6 acre site located on the northeast <br /> corner of Alameda and North Main Street in Manteca, California Currently, there is a <br /> shopping plaza on the property <br /> In 1985, the underground tanks from an abandoned service station were removed form <br /> this site The San Joaquin County Environmental Health Department had determined <br /> that a petroleum release had occurred to the subsurface <br /> Two (2) site investigations were undertaken between 1986 and 1990 by Harding <br /> Lawson & Associates and Canonie Engineering <br /> WHF Environmental Consultants, Inc , proposed an excavation of the contaminated <br /> soils, which took place on September 20, 1990, and was completed on October 3, <br /> 1990 A total of 4,394 cubic yards were excavated, of which 903 cubic yards were con- <br /> taminated. The contaminated soil was remediated by aeration, on the site <br /> There are, currently, six (6) monitoring wells on this site Two (2) of the monitoring <br /> wells, which are located in the southwest end of the property, had previously shown <br /> low levels of contamination This is the area where approximately 20 cubic yards of <br /> soil has been left in place from the excavation These contaminated soils were left in <br /> place because their removal would have caused the remedial excavation sidewall to fail, <br /> endangering the workers and civil structures (sidewalk, street pavement, buried <br /> utilities) The contaminated soils are at a depth of 22 feet, they could have an area of <br /> 560 feet7 and have a thickness of one foot <br /> WHF, with the approval of San Joaquin Environmental Health and the Air Pollution <br /> C,')ntrnl Distnct, i,,. l'ropo-ng to inct?Jl a co'1 -- or eXtraction gystem 71,ts will rr rvmst <br /> of placing a soil gas extraction system on to the monitoring well in the location of the <br /> contamination The piping will extend 15 feet to the north of the monitoring well into <br /> two (2) carbon canisters (in series). The area will have a steel cage surrounding it to re- <br /> strict public access This phase of work is estimated to take approximately three to four <br /> (3-4) months <br />