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SECrk w�secoccom <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C O R INCORPORATED 916- 661-0400V SCA 95670 <br /> 916-061-0430 vnx <br /> December 30, 2003 <br /> Mr. Michael Infurna ZOO <br /> San Joaquin County Environmental Health Depar%TTH <br /> Environmental Health Division Et,,v, <br /> 304 East Webber Avenue, Third Ropy ri{vii I, �_nVICES <br /> Stockton, CA 95202 <br /> Re: Response to San Joaquin County Environmental Health Department <br /> Circle K Store 01205 <br /> 16470 Cambridge Street, Lathrop, California <br /> SECOR Project No.: 77CP.61205.06.00010 <br /> Dear Mr. Infurna: <br /> This letter, prepared by SECOR International Incorporated (SECOR) on behalf of ConocoPhillips, <br /> presents the response to correspondence between Mr. Mike Infurna with San Joaquin County and Ed <br /> Ralston with ConocoPhillips (e-mail November 5, 2003) and Clinton Harms with SECOR International <br /> (phone conversation November 5, 2003) regarding Addendum to Work Plan for Off-Site Assessment <br /> dated April 7, 2003. During the above mentioned correspondence Mr. Mike Infurna addressed the <br /> two following concerns 1) performing additional lateral assessment based on only one sampling <br /> event conducted at well MW-16 may not be appropriate and 2) the need for vertical assessment of <br /> the dissolved groundwater plume both on and off-site. <br /> Performance of Lateral Assessment <br /> The fourth quarter groundwater sampling event performed at the site was conducted on October 9, <br /> 2003 (Analytical data is included in Attachment A and will follow in a quarterly monitoring report <br /> prepared by TRC Alton Geosciences). The following are the results and a comparison with 3rd <br /> quarter 2003 data for the down gradient wells. Well MW-16 was initially developed and sampled on <br /> September 15, 2003 after installation. <br /> 3 Quarter 2003 4 Quarter 2003 <br /> Well TPH MTBE TP H MtBE Comments <br /> MW-12 7,600 880 16,000 540 Increase in TPH /decrease in MtBE <br /> MW-13 <50 <2.0 <50 <2.0 Same <br /> MW-14 <50 6.6 <50 2.3 Decrease in MtBE now below MCL <br /> MW-16 52 140 <100 180 Sli ht Increase in MtBE <br /> All concentrations in parts per billion (ppb) <br /> SECOR would request that SJC EHD approve the Addendum to Work Plan for Off-Site Assessment <br /> dated April 7, 2003 based on the above data. SECOR anticipates that the work will be completed <br /> during the first quarter after encroachment permits and access agreements are completed. <br /> Performance of Vertical Assessment <br /> ConocoPhillips would like to complete the vertical assessment requested at the site during a future <br /> scope of work, not the currently proposed work outlined in Addendum to Work Plan for Off-Site <br />