Laserfiche WebLink
N <br /> Remo Canepa Page 4 of 5 <br /> 6230 Pacific Avenue May 18, 2011 <br /> Stockton, CA <br /> 1993 and that there was a 14-year window opportunity for a release of gasoline containing <br /> MTBE from the old UST system and at most a 3 .5-year window for such a release after the new <br /> UST system was installed. As discussed below, there have been no reported releases to the <br /> i <br /> subsurface from the UST system or repairs of the system during the latter time period. <br /> The following graph shows MTBE concentrations from 1996 to 2010 . Laboratory analysis for <br /> MTBE on the site did not begin until August 1996 , approximately 3.5 years after the current UST <br /> system was installed ; it can be seen on the graph that MTBE was already present at significant, <br /> and apparently stable concentrations at that time. In July 1998, when well SV-4 was first tested <br /> for MTBE, the compound was already present at a concentration in excess of 100 ,000 <br /> micrograms per liter. The gradual concentration increase in the down-gradient MW-3 may <br /> represent migration of more intensely impacted groundwater to that well , while the fairly abrupt <br /> concentration increase in MWA may be related to the decline of groundwater elevation bringing <br /> more intensely impacted groundwater closer to the screened interval of that well. <br /> DTW vs MTBE all <br /> 1000000 0 <br /> M <br /> 100000 10 <br /> x <br /> 10000 20 <br /> ( ,, -0- MW-1 MTBE <br /> °P !C" -o- MW-2 MTBE <br /> 0 1000 30 -x- MW3 MTBE <br /> - - SV4 MTBE <br /> K + 6230 Pacific DTW <br /> c ] 4 a <br /> U <br /> 100 40 <br /> 10 x 50 <br /> 1 60 <br /> 4L 4h 4) C1 O� OA 90 O� Off' O� Ob Oh OfO 0 00 DO <br /> SO AJC )JC �J� AJC AJC AJC AJC AJC AJC AJC SO AJC 30 AJC <br /> Sampling Dates <br /> In the EHD letter dated 08 October 2009, the EHD identified additional information needed to <br /> better evaluate the chemical data and the interpretation put forth by F&B ; however none of this <br /> has been provided . The EHD will not issue a LIAR based on tentatively identified compounds <br /> (F&B report dated 10 December 2009) and notes that F&B did not repeat their initial <br /> interpretation of a new release in their last report. <br /> The EHD reviewed the UST records again to check for any indication of a significant release <br /> from the current UST system and discussed the records with the Program Coordinator of the <br /> EHD unit that oversees USTs . The EHD records show a small release under a dispenser in <br /> 2006 that stayed within the secondary confinement system and a release from a leaky fuel filter <br /> LIAR Request Response and Directive Letter 0511 <br />