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T _ ^ <br /> Page 1 of 1 <br /> Vicki McCartney [EH] <br /> From: Nuel Henderson [EH] <br /> Sent: Tuesday, March 20, 2012 3:42 PM <br /> To: 'Kirk Larson' <br /> Cc: Vicki McCartney [EH] <br /> Subject: Shell Station at 620 W Charter Way, Stockton; CUF Claim No. 4954 <br /> Kirk, <br /> The above referenced site still has free product in monitoring well MW-16-50, about 1/4th inch when last <br /> measured and nearby Monitoring well MW 9 has had a significant dissolved concentration increase during the last <br /> monitoring event in October 2011. In MW9, TPH g increased from 3400 ppb to 21,000 ppb; benzene from 37 ppb <br /> to 200 ppb; MTBE and other oxygenates were about the same as usual. <br /> You've recommended closure consideration in 2010 and 2011, and at least in 2011you noted the presence of <br /> free product in MW16-50 and other wells in the past. The so-called B interval, from 45 to 50 feet bsg, commonly <br /> contains a sand unit that appears to be overlain and underlain by fine-grained units; it appears to be a potential <br /> migration pathway. The impact has not been delineated toward the north and northwest. <br /> think we should try to remove the free product from MW16=50, monitor MW-9 once or twice more to see if <br /> concentrations continue to increase, stabilize or decline. Also, a grab sample from the B interval in the <br /> undelineated direction would be helpful. Can you modify your recommendation, or should we proceed with site <br /> closure? <br /> Nuel Henderson <br /> i <br /> i <br /> 3/20/2012 <br />