SITE INFORMATION AND CORRESPONDENCE FILE 2

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" ENVIRONMENTAL HEALTH DEPARTMENT SANJOAQUIN COUNTY Unit Supervisors 2 Donna K. Heran, R.E.H.S. Carl Bor man, R.E.H.S. Director304 East Weber Avenue, Third Floor Borg man, Huggins, R.E.H.S., R.D.T. At Olsen, R.E.H.S. Stockton, California 95202-2708 Douglas W Wilson, R.E.H . S. Program Manager Telephone: (209) 468 -3420 Margaret Lagorio, R.E.H .S . :I 9GIF Laurie A. Cotulla, R.E.H.S. Fax: (209) 464-0138 Robert McClellon. R.E.H. S . Program Manager Mark Barcellos, R.E.H. S . RODGER LISTON MAY 1 2 2004 DARPETRO INC USA SERVICE STATION 3450 EL CAMINO CERES CA 95307 RE: DARPETRO, INC Site Code : 1060 749 E CHARTER WAY STOCKTON, CA 9520 San Joaquin County Environmental Health Department (EHD) has received and reviewed a letter dated 04 May 2004, California Geophysical Group, Inc. Water Sampling Protocols (undated), and Amended Quarterly Report October 2003, all prepared and submitted by your consultant California Geophysical Group, Inc. (CGG). The documents were submitted in response to EHD directives issued by letters dated 13 April 2004, 16 April 2004 and 27 April 2004. The letter, resulting from the EHD directive of 13 April 2004, provides, data from an unidentified site in Modesto that CGG used to infer that the MTBE-impacted plume sinks at a rate of 1 foot per 20 feet of horizontal travel due to increasing density of the ground water from the addition of the methyl tert-butyl ether (MTBE). The data and calculation presented are fairly straight forward , but were not presented in the context of a site model with a sinking plume driven by a density increase of ground water due to the dissolution of MTBE into the ground water. The example given by CGG in the 04 May 2004 letter does not provide the demonstration that EHD was seeking. What EHD was requesting was a demonstration from other sites, preferably third party peer-reviewed reports, scientific articles or texts, that demonstrate descending plumes of MTBE- impacted ground water due to a density increase, as was attributed to the plume on your site by CCG in their Amended Site Concept Model of 17 November 2003. As this particular point is not likely to influence the work remaining on your site and EHD does not believe that there are reference works that demonstrate this particular phenomenon for MTBE-impacted ground water, your consultant need not respond further to this issue . The EHD directive for preparation and submission of a ground water monitoring plan for your site was fairly specific and the submitted California Geophysical Group, Inc. Water Sampling Protocols (protocols) document is not sufficient to meet the directive. Of necessity, the ground water monitoring and sampling plan will include many of the same procedures stated in the protocols, but the monitoring and sampling plan should be a more comprehensive document that, if followed, should lead to acquisition of high quality, useful data that will move this site toward eventual closure. Indeed, the protocols, included as an appendix of numerous quarterly monitoring reports, have not proven to be sufficient to assure collection of data having a high degree of confidence, as was observed by EHD during two recent monitoring events and detailed in the 16 April 2004 and 27 April 2004 letters - which is the reason EHD had directed preparation and submission of a ground water monitoring and sampling plan . The protocols recently submitted are rejected by EHD as insufficient to meet the directive on this subject. The specific items that EHD had directed to be included in the plan that were not addressed adequately, or were not addressed at all , included :