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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 /> RE: Source Test for vapor 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 27-280 1990 , <br /> monitor well MW10 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 MW10 was connected to a vacuum system ( 1HIP <br /> Rotron Blower ) that exhausted into two 85 gallon activated <br /> charcoal tub scrubs . Sample ports were located at excavation <br /> wells EX1 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 of the blower , and the exhaust of the charcoal. The <br /> exhaust from the tub scrubs was checked daily for breakthrough <br /> using a hand held photoionizing detector (PID) that has been <br /> calibrated to 50 ppm i.sobutylene in air. Breakthrough was assumed <br />