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San Joaquin County <br /> Environmental Health Department <br /> 600 East Main Street <br /> Stockton, California 95202 <br /> Phone: (209) 468-9852 <br /> Fax: (209) 468-3433 <br /> Email: vmccartney@sjcehd_com. tmailto:vmccartney@sjcehd.com> <br /> From: David R. Daniels [mailto:david.daniels@cardno.com] <br /> Sent: Tuesday, January 3.1, 2012 6:16 AM <br /> To: Vicki McCartney [EH] <br /> Subject: RE: Former Mobil Service Station located at 25355 North Highway 99, Acampo, <br /> CA <br /> Vicki, <br /> The 1,2 DCA trend evaluation for .25355 North Highway 99 in Acampo is provided below <br /> and in the attached graphs. Please contact me with any .comments or questions. <br /> ESTIMATE OF TIME REQUIRED TO MEET Water Quality Numerical Limits <br /> Cardno ERI compared the dissolved-phase- concentrations at the site with water <br /> Quality Numerical Limits (WQNLs) established by the California Regional Water Quality <br /> Control Board, Central Valley Region . (CRW QCB-CVR 2004) . <br /> Wells in which 1,2 DCA concentrations exceed WQNLs were graphed versus time and a <br /> first-order exponential decay trendline was added to show when WQNLs will be achieved. <br /> li Well MW1 <br />� 1, 2 DCA concentration in well Mn1 increased by approximately one order of magnitude <br /> I <br /> during 2004 and have since declined. Cardno ERI prepared a regression based on the <br /> analytical data following the 2004 increase. Based on the regression, the 1,2 DCA WQNL <br /> will be achieved in well MW1 in approximately 2021_ <br /> r <br /> Well MW3 <br /> f <br /> 3 <br />