SITE INFORMATION AND CORRESPONDENCE FILE 2

Home Browse Search

N N ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY Q40, Uuit Supen isors Donna K. Heran, R.E.H.S. Carl Bor man, R E H S . Director 304 East Weber Avenue, Third Floor sAI Olsen, R.E.H.S. Stockton, California 95202-2708 Mike Huggins, R.E.H.S , R.D. I . Douglas W. Wilson, R.E.H.S . Prograar Manager Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. Laurie A. Cotulla, REMS, Fax : (209) 464-0138 Robert McClellon, R.E.H.S . Program Manager Mark Barcellos, R.E.H.S, RODGER LISTON APR 1 3 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 reviewed Amended Site Concept Model (SCM-A), dated 17 November 2003 , prepared on your behalf by California Geophysical Group, Inc. (CGG). The SCM-A was received by EHD on 21 November 2003. EHD also has discussed the SCM-A with Mr. James Barton of the Central Valley Regional Water Quality Control Board (CVRWQCB). A copy of Quarterly Report October 2003 was received by EHD on 14 November 2003 and Quarterly Report January 2004 was received on 17 February 2004. The quarterly reports were also reviewed by EHD ; comments are provided below. During this review, EHD has updated its site chronology and integrated the pertinent findings and data to evaluate CGG's interpretation that the methyl tert-butyl ether (MTBE) is originating from an up-gradient source. The SCM-A lists the historical stages of the site investigation and references the reports containing the results and data of the various investigations. Some of the findings of each stage of investigation or specific data that CGG draws on for their interpretations are noted in the Geology section . The section titled 'Geology' describes the upper 70 feet or so of soil types (lithology) underlying the site as consisting of 19 to 22 feet of silty clay and clayey silt underlain by 3 to 5 feet of silty sand , underlain by 23 to 25 feet of silty clay, which overlies approximately 20 feet of silty sand , which in turn is underlain by clay of unknown thickness . The contaminant distribution encountered in the borings advanced on the site was discussed in very general terms. There were no summary descriptions or calculations of contaminant masses and distribution in soil included in this or any other portion of the SCM-A. The SCM-A included three cross sections and a reference map showing the lines of cross section and monitoring well locations . It is the opinion of EHD that the amended site conceptual model (SCM), as presented, still does not adequately demonstrate the professional interpretations and opinions advanced by CGG in the SCM-A. There was no summary of conclusions and interpretations presented by CGG, but EHD believes the following to be CGG's main points and interpretations : j i