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1 - <br /> Remo Canepa Page 4 of 9 <br /> 6230 Pacific Avenue 4/17/2009 <br /> Stockton CA <br /> Canepas Car Wash MW,1 <br /> 6230 Pacific Ave. <br /> 1000000 <br /> i <br /> f <br /> s <br /> I m0000 It <br /> i <br /> t <br /> t <br />� t0000 <br /> 6/17/94 <br /> #1/21/05 <br /> TPHg <br /> 000 Ben ene <br /> 4121/9 <br /> 8/1/96 MTBE <br /> 7/22/04 <br /> U 100 <br /> 10 <br /> 1 r 1 <br /> p b <br /> i K� n" e`O Kej1 e9 R8' c' t� c9�" Ko`� c' c5i' X00 Ko PO <br /> Monitoring Dates <br /> • MW-1 , located near SV-4, screened from 50 to 70 feet bsg , currently with <br /> approximately 14 feet of water above screen , has been monitored from June <br /> 1994 to November 2008, is currently utilized for GWE and monitoring . From 1994 <br /> to approximately 2002, TPHg and benzene concentrations track together and <br /> gradually declined ; the initiation of SVE in March 1999 had no marked effect on <br /> the concentration trend , although the trend did continue downward . After analysis <br /> for MTBE started in 1996 , concentrations generally increased until SVE was <br /> initiated , then declined until 2002 , at which time concentrations of TPHg, <br /> benzene and MTBE started a gradual increasing trend , the concentrations of all <br /> three abruptly increased in January 2005 with the implementation of GWE , after <br /> which MTBE concentrations started a very gradual decline and benzene and <br /> TPHg started a very gradual increase. The EHD interprets the general <br /> concentration decline from 1994 to 2001 /2002 of TPHg and benzene to be a <br /> natural attenuation effect, the MTBE increase possibly due to advancing <br /> migration of dissolved MTBE from the late stage of release from the UST system <br /> when MTBE was a more common component of gasoline. The gradual <br /> concentration increase from 2001 /2002 to 2004 may be related to a more recent <br /> release, but may also represent natural variation of concentrations or may be <br /> related to other factors such as variation of groundwater elevation or flow <br /> direction ; it is not a sharp increase that would be more convincing of a second <br /> release. The sharp increase of all concentrations in January 2005 may have <br /> been related to implantation of GWE, which appears to have drawn more <br /> intensely impacted groundwater to the well . <br /> Second Release Evaluation 0409 <br />