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R <br /> 8town anti Caldwell <br /> Cunsuitants <br /> :rzrrerta <br /> •r�aaa�^3 <br /> =a<C}161 a.1s3" <br /> January 20, 1992 JAN 2 3 1992 <br /> CNV)R1.;!9f0CNTAL l'::•l.TF1 <br /> PERMIT/SERVICES <br /> Mr. Cm k Carmel <br /> ARCO Products Company <br /> 20M Alameda de las Pulgas <br /> Post Office Box 5811 017-5690-03/1 <br /> San Mateo,California 94402 <br /> Subject: Status of Groundwater Extraction System, ARCO Station 2133, <br /> Stockton,California <br /> Dear Mr. Carmel: <br /> ' This letter presents the current status of the groundwater extraction system and the results of the <br /> groundwater discharge sampling at ARCO Products Company (ARCO)Station 2l33,1G^ated at ; <br /> 2908 Henjanxin Holt Drive in Stockton, California. Listed chronologically is a summary of the <br /> activities related to the discharge of groundwater at the site from November 16 tl.rough_ <br /> December 15, 1991. Table 1 presents a summary of the artected constituents for the extta:ti��i; <br /> system to date. <br /> The groundwater extraction system was not operating continuously during this reportkig period <br /> of 30 days. As stated in the December 16, 1991 status letter the extraction system flcSv rate was <br /> decreased to 5.5 gallons per minute(gpm)from 10.5 gpm because the zone of capture Was larger <br /> than needed. The decreased flow.in the discharge piping allowed sewer gases from,*e sewer ' <br /> main to migrate back ug to the point where the lower explosive limit(LEL)exceeded 10 percent <br /> -which tamed the system off. <br /> 'Cite LEL sensor was checked and calibrated,and the system restarted. The system again turned <br /> off due to a high LE alarm after approximately 2000 gallons were discharged. The LEL sensor, <br /> has been relocated so that it monitors explosive gases in the headspace of the above'gxourl <br /> holding tank: In this location the LEL sensor monitors gases that are more representative of <br /> gases being;discharged to the see-t:r. The system was restarted on December 2D, at 5 gprrt,and <br /> has been operating since then. Tile system was sampled for TPH-G/BETX, metals, and total <br /> toxic organics on January 8, 1992. The results of this sampling will be included in the next <br /> -;� status report (covers December 16, 1991 through January 157 1992). <br /> ;•lc� t �e�- 1 5 . <br />