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fi <br /> January 17, 1991 <br /> Mr. John Margowski _ <br /> Environmental Director <br /> Wickland Properties <br /> 1765 Challenge Way <br /> Sacramento, CA 95815 <br /> (916) 921-1100 <br /> PE. Source Test for %a-)or extraction, former Regal Station 603 <br /> (EXXON) , 6425 Pacific Avenue, Stockton, California. <br /> Dear Mr. Margowski: <br /> INTRODUCTION <br /> This letter documents the results of the source test for vapor <br /> extraction into activated charcoal at the above mentioned site. <br /> PILOT TEST <br /> Gasoline range hydrocarbons are known to exist beneath the <br /> undergound storage tanks area. The tank excavation was <br /> overexcavated to the 26 foot depth. on December 27-28, 1990, , <br /> monitor well MWlO was manifolded to the treatment area. On <br /> January 3, 1991, activated charcoal in two 85 gallon tub scrubs <br /> were delivered to the site. The blower was installed on January <br /> 7, 1991, and a few days later, the test was begun. The test was <br /> conducted for three and a half days (january 11-January 15, 1910) . <br /> Break through was noted from a sample obtained on January 14 and <br /> analyzed on January 15, 1991. At this time the system was , <br /> sampled, shut down, and disconnected. <br /> TEST PROCEDURES <br /> Vapor extraction well NW10 was connected to a vacuum system (1HP -i <br /> Rotron Blower) that exhausted into two 85 gallon activated <br /> charcoal tub scrubs. Sample ports were located at excavation <br /> wells ES1 and EX2 and monitor wells MW1, MW2, MW3, MW4, MW6, and <br /> MW9 for obtaining vacuum/pressure and vapor readings during the <br /> test. Also sample ports were located at the intake of the blower, <br /> the exhaust rg thv blower, and the exhaust of the charcoal. The is} <br /> exhaust from the tub scrubs was checked daily for breakthrough ` <br /> using a hand held photoionizing detector (1ID) that has been <br /> calibrated to 50 ppm isobutylene in air. Breakthrough was assumed <br />