Laserfiche WebLink
Mr. Michael T. Goldstein <br /> October 28 , 1985 <br /> Page 4 <br /> Simulation <br /> Analysis of simulations demonstrated chloroform that leaked into the <br /> aquifer after April 20 , 1985, was recovered by the recovery system <br /> initiated on July 1 , 1985. The simulations showed 125 pounds of <br /> chloroform entered the aquifer between April 20 , 1985 , and October <br /> 15 , 1985 . The simulations also demonstrated the recovery well system <br /> has removed approximately 95 pounds of chloroform as of October 15 , <br /> 1985. Another 15 pounds of chloroform will be removed by <br /> Novembver 15, 1985, and an additional 15 pounds will be removed if <br /> RW1 continues pumping until January 1986 . This will leave the <br /> 30 pounds of chloroform that entered the aquifer prior to April 20 , <br /> 1985 , still in the groundwater. <br /> The water pumped from RWl has been intermittently discharged into the <br /> excavated basin introducing variable amounts of chloroform into the <br /> aquifer. This has leached chloroform out of sediments under the <br /> basin and into the aquifer. The effectiveness of the recovery system <br /> has been confirmed by the decreasing chloroform concentrations in the <br /> wells around the basin after slugging. Over all concentrations have <br /> been reduced by pumping, and simulation indicates concentrations will <br /> continue to be reduced by the recovery system. <br /> Assumptions <br /> The following assumptions were utilized to develop the simulations : <br /> 1. A uniform aquifer thickness of 40 feet, confirmed from well <br /> lithology logs. <br /> 2. Uniform hydraulic properties in the shallow aquifer, derived <br /> from the recovery well (RW1 ) aquifer test. <br /> 3. The storm water basin was the only source of chloroform. <br /> 4. The initial concentration of chloroform in the basin was <br /> 200 ,000 ppb, derived from analyses of basin water samples <br /> taken in August 1984. <br /> 5. The production from the recovery well was 110 ,000 gallons per <br /> day ( 76 gallons per minute) after June 30 , 1985. <br /> 6. The infiltration into the basin averaged 33 ,200 gpd after <br /> June 28 , 1985, based on analysis of records of discharge to <br /> the basin and did not significantly effect the groundwater <br /> velocity. <br /> 7. Infiltration of water through the basin will be minimal after <br /> October 15 , 1985. <br /> BROWN AND CALDWELL <br /> P.O.BOX 8045 WALNUT CREEK,CA 94596-1220• (415)937-9010 TELEX 33-6490•OFFICE AT 3480 BUSKIRK AVENUE PLEASANT HILL 94523 <br />