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Woodward-Clyde <br /> Consultants <br /> Diane M. Hinson <br /> San Joaquin County Environmental Division <br /> October 11, 1994 <br /> Page 2 <br /> TANK REMOVAL ACTIVITIES <br /> On October 4, 1994, Woodward-Clyde observed the removal of two 10,000-gallon steel <br /> USTs, from the YFS facility in Stockton, California. The tanks reportedly contained diesel <br /> from 1973 to 1990. The tank removal and soil sampling activities were directed by San <br /> Joaquin County, Environmental Health Division (SJCEHD). The tank removals were <br /> performed by SEMCO Environmental of Modesto, California, under contract with Kelleher <br /> Environmental Inc., of Burnsville, Minnesota. Kelleher is contracted by Yellow Freight <br /> System Inc. <br /> Tank product piping and two pump dispensers were located just east of the two USTs. No <br /> visible holes were observed in the two-inch diameter product piping. The pump dispensers <br /> were operated by suction. Several holes measuring up to 0.5-inch in diameter were observed <br /> in both of the 3-feet long, 4-inch diameter fill pipes. No cathodic protection devices were <br /> observed for the tanks or its appurtances. <br /> Both tanks had a diameter of 8-feet and a length of 28-feet. Less than 50-gallons of product <br /> were removed from the tanks prior to triple-rinse cleaning. The tanks were triple-rinsed <br /> with a hot pressure steam wash, with rinseate pumped into two 55-gallon drums. Both USTs <br /> were inserted with dry ice prior to their removal from the excavation. The tanks were <br /> measured for percent Lower Explosivity Limit(LEL)and percent oxygen using a GASTECH <br /> Model 1314 combustible gas indicator. Both tanks were observed to have zero percent LEL. <br /> The northernmost tank (Tank #2) exhibited 18% oxygen and the southernmost tank <br /> (Tank #1), exhibited 16% oxygen. <br /> Upon removal of Tank #1, three holes were observed on the bottom of the tank, below the <br /> fill end. One hole was approximately 2-inches in diameter. Two smaller holes, <br /> approximately 0.5-inch diameter, were observed near the larger hole. The remainder of the <br /> tank appeared in fair condition. Tank #2 was observed to be in good condition with no <br /> apparent holes or corrosion. The tank bottoms were observed at a depth of approximately <br /> 11-feet below ground surface (bgs). <br /> SOIL SAMPLING AND ANALYSIS <br /> Soil samples were collected by Woodward-Clyde at the direction of Mr. William R. Snavely <br /> of SJCEHD after the tank removal activities. A backhoe was used to collect the soil samples <br /> 4H04055VAYFs.WP(10-10-94)SAC <br />