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aqua sc&.ice <br /> Now - IVengineers Inc. _ <br /> September 6 2002 <br /> SEP 12 2002 <br /> Ms. Lori Duncan ENVIRONMENT HEALTH <br /> San Joaquin Public Health Services PERMIT/SERVICES <br /> Environmental Health Division <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> SUBJECT: PROPOSED MODIFICATION TO DOMESTIC WELL <br /> SAMPLING FREQUENCY <br /> In Reference to: <br /> Frank's One Stop Service Station <br /> 2072 West Yosemite Avenue <br /> Manteca, California <br /> Dear Ms. Duncan: <br /> Since August 2000, Aqua Science Engineers, Inc. (ASE) has been collecting <br /> and analyzing water samples from domestic wells along Airport Way and <br /> Yosemite Avenue in Manteca, California (those with and without treatment <br /> systems) as a requirement related to the assessment of the plume related <br /> to the subject site. Since that time, we have compiled a great deal of data <br /> and have been able to see trends in the concentrations of contaminants. <br /> ASE believes it is now appropriate to modify the sampling frequency of the <br /> the domestic wells (except for 17950 Airport Way) for the following <br /> reasons: <br /> • Of the 15 domestic wells sampled, 11 of them are plumbed to a <br /> remediation system installed and maintained by ASE. Since the <br /> systems' installation, we have experienced breakthrough of MTBE o u t <br /> of the initial carbon canister in only one case, at 17950 Airport Way. <br /> The remaining 10 systems have not shown any breakthrough of any <br /> compound analyzed. The operating time of these remaining vessels h a s <br /> been no less than 8 months (at 495 Airport Way) and up to 17 months <br /> (at 17933 Airport Way). Furthermore, each of the systems has been <br /> designed with a redundancy factor; several carbon canisters plumbed <br /> in series. If the initial canister shows breakthrough, the second <br /> canister in line will contain the contaminants and ensure that the <br /> residents only receive treated water. <br /> The influent concentrations of these wells has either leveled-off or <br /> 208 W EI Pintodo, Danville, California 94526 • 925-820-9391 • Fax 925-8374853 <br />