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r <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 /> 304 East Weber Avenue, Third Floor <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • �.. P• Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> qc;F o a� p Robert McClellon,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Fax: (209) 464-0138 <br /> Program Manager Mark Bareellos,R.E.H.S. <br /> APR 2 7 2004 <br /> JOHN & MARGARET MARCI <br /> 6816 STABILUS ROAD <br /> VALLEY SPRINGS CA 95252 <br /> RE: John and Margaret Marci Property SITE CODE 2015 <br /> 2969 Loomis Road <br /> Stockton, California 95205 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan Pilot Test <br /> for Soil vapor Extraction, dated September 17, 2003, prepared and submitted on your behalf by <br /> Geological Technics Inc. (GTI). In this work plan, GTI proposes a soil vapor extraction (SVE) <br /> remedial action pilot test, targeting the clay/silt zone at a depth of approximately 50 to 60 feet <br /> below ground surface (bgs). An extraction well (VEW-1) is proposed to be installed approximately <br /> ten feet southwest of monitoring well MW-7 and screened between 53 and 58 feet bgs. An <br /> additional extraction well (VEW-2), screened between 53 and 58 feet bgs, would be installed west <br /> of VEW-1 to monitor the vacuum influence from VEW-1. The pilot test is anticipated to last five <br /> days and the results will be used to determine the feasibility of removing diesel concentrations <br /> using high vacuum extraction pressures. <br /> EHD also reviewed the geologic cross sections A—A' and B—B' submitted in the work plan and is <br /> concerned that the heavy hydrocarbons may not be recovered by the SVE system. Additional <br /> information is needed to evaluate this proposal. Please provide the following: <br /> • References for other diesel sites with similar lithology having successful application of this <br /> proposed technology; <br /> • Estimation of the percentage of diesel concentration having favorable vapor pressure that <br /> may be susceptible to the enhanced vacuum; <br /> • Justification for targeting the 50 to 60 foot clay/silt zone as opposed to the sand/gravel zone <br /> at approximately 40 to 50 feet bgs near MW-4 and MW-7 where free product was <br /> encountered ; and <br /> • Specification of the pressure drop still effective for diesel volatilization to be utilized to <br /> define the radius of influence. <br /> t A-1 Further investigation of the contamination will be necessary to assess the vertical and lateral extent <br /> l 'of impacted soil and groundwater at this site. Please prepare a site conceptual model (SCM) to use <br /> as a tool for future work on this site. The general purposes for an SCM are to demonstrate where <br /> 11 ' �, , the contaminants came from, where they are at the present time, how they move through the <br /> I ' subsurface,how they will respond to changes in the groundwater flow characteristics or to potential <br /> 1 <br />