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I <br /> 1� <br /> ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Director 304 East Weber Avenue, T111IC1 Floor Mike Huggins,R.E.H.S.,R.D.T. <br /> ` Al Olsen,R.E.H.S. Stockton, California 95202-2708 <br /> Douglas W.Wilson,R.E.H.S. <br /> • c: �c , Program Marrager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Q�rfioR� Robert McClellon,R.E.H.S. <br /> Laurie A.Cotuua,R.E.H.S. Fax: (2.09) 464-01.35' <br /> Program Manager Mark Barcelios,R.E.H.S. <br /> LORI SHIELDS 3 'F EB 17 2004 <br /> DIESEL PERFORMANCE <br /> 2804 FREMONT STREET <br /> STOCKTON PA .. 95205 <br /> RE: Diesel Performance SITE CODE: 1120 <br /> 2804 Fremont Street, <br /> Stockton EA 95205 <br /> San Joaquin County Environmental Health Department (SJCIEHD) has reviewed "Site <br /> Conceptual Made <br /> 1a�� nd Corrective Action Plan dated January 5, 2004" submitted on your <br /> behalf by ATC Associates, Inc. (ATC) and has the following comments. <br /> In correspondence dated July 8, 2003, SJCIEHD directed the submittal of a Site <br /> Conceptual Model (SCM), and requested that it include cross sections showing the site <br /> hydrogeological framework, potential contaminant migration pathways, and a rose.' <br /> diagram of the historical groundwater flow direction. The submitted document did not <br /> contain these items. The SCM as submitted included a discussion of:the subsurface <br /> lithology at the site-based on one cone penetrometer testing;(CPT) boring, a two <br /> dimensional diagram of the estimated extent of the soil contamination, and a general <br /> discussion of potential human exposure pathways that would typically be included in a <br /> risk based corrective action (RBCA) model. Although risk tohuman health is an <br /> important consideration, SJCIEHD needs to consider the transportation and fate of the. <br /> contaminants in the subsurface. Please re-submit a complete SCM, including the items <br /> listed above and an estimate of the contamEnant mass remaining in soil, as soon as <br /> possible, but no later than March 5, 2004. A <br /> The contaminant concentrations in groundwater at this site have decreased in recent <br /> water elevation. Current <br />' monitoring events, in theroundcoinciding 'with a decrease g <br /> depth to water is approximately 54 feet below surface grade (bsg). Known soil <br /> contamination is present at this site near the former underground tank location, to depths <br /> of approximately 45-50 feet bsg. A December 2001 feasibility study indicated that soil <br /> vapor extraction would be a viable method for remediation othe soil contamination <br /> f <br /> remaining at this site. The CAP recommends using a high vacuum dual phase <br /> extraction mobile remediation system to target the contaminated vadosE and capillary <br /> fringe zone soils. Existing vapor extraction and monitoring wells are proposed for use in <br /> the remediation. ATC proposes to conduct the remedial action as three separate <br /> five-day events, one event per month, over a period of three'months., No justification or <br /> rational was provided for this proposed period of operation. SJC/EHD can approve <br /> time-limited pilot tests, but not time-limited final remediation. SJCIEHD concurrence <br /> must be obtained before ceasing remedial actions. <br /> i <br />