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X� ENVIRONMENTAL HEALTH ]DEPARTMENT <br /> 'OPpu1N CO <br /> SAN JOAQUIN COUNTY <br /> Pro rant Coordinators <br /> N � � , t( Donna K. Heran, R.E.H.S. 8 <br /> 304 East Weber Avenue, Third Floor carr I3or man, R. E. H.S. <br /> Director Borg <br /> man, <br /> A. Cotulla, R.E.H.S. Stockton, California 95202-2708 Mike Huggins, R. E 1i.S ., R.D .T. <br /> cgZlFsa��c Assistant.DirectorTelephone: (209) 468-3420 Margaret Lagono, R.E.H.S . <br /> Robert McClellon, R.E.H.S. <br /> Fax : (209) 464-0138 Jeff earruesco, R.E.H.S. <br /> Website : www.sjgov.org/ehd/ Kasey Foley, R.E.H.S. <br /> JAN © 2 2007 <br /> GARY STALLWORTH LEWIS STALLWORTH <br /> 602 CALIFORNIA STREET 1107 BURKETTE AVE <br /> STOCKTON CA 95202 STOCKTON CA 95205 <br /> RE : Stallworth Auto Sales SITE CODE : # 2486 <br /> 602 California Street <br /> Stockton CA 95202 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed Soil <br /> Vapor Extraction/Air Sparge Feasibility Work Plan (Work Plan) dated December 14 , 2006, <br /> submitted on your behalf by Advanced GeoEnviron mental , Inc. (AGE) and has the <br /> following comments. <br /> The Work Plan was submitted in response to a directive from SJC/EHD to submit a <br /> feasibility study for determining the most effective remediation alternative for your site. <br /> The Work Plan proposes the installation of six soil vapor extraction (SVE) wells, three <br /> screened from 10-20 feet below surface grade (bsg ) and three screened from 20-30 feet <br /> bsg , and one air sparge (AS) well screened from 35-40 feet bsg . The Work Plan <br /> proposes to conduct two 8-hour SVE tests for determining the feasibility of using SVE for <br /> remediation of the vadose zone soil contamination present near and downgradient from <br /> the former underground storage tank location , and one 72-hour AS/SVE test to determine <br /> the feasibility of using AS to remediate shallow impacted groundwater. <br /> SJC/EHD approves the installation of four SVE wells, the two pairs proposed to be <br /> located near the former tank pit area, as adequate to conduct an SVE pilot test. The <br /> SJC/EHD recommends that the vapor well screen intervals be set by soil lithology, rather <br /> than strictly by depth, to more effectively address each soil lithology. According to cross- <br /> sectional diagrams provided by AGE for your site, the proposed depth of the air sparge <br /> well would have it screened in clay. SJC/EHD does not approve the installation of this <br /> well at this time. The SJC/EHD will reconsider this proposal if it can be shown in an <br /> addendum work plan that the sparged air and stripped hydrocarbons are likely to be <br /> recovered by the SVE system and are unlikely to spread the plume horizontally. A <br /> feasibility study, comparing at least two different remedial alternatives , must be completed <br /> to address the groundwater contamination at this site , contamination that exists in high <br /> concentrations to a depth of 50 feet bsg (MW-1 B) and at lesser concentrations to 150 feet <br /> bsg (MW-1 D). Air sparging into clay at 40 feet bsg would not provide an adequate test to <br /> determine the best remedial alternative for the groundwater contamination at your site. <br /> Review of cross sections prepared by AGE and quarterly groundwater monitoring results <br /> for deep wells MW- 1 C and MW- 1 D show that the sandy interval between 60 and 70 feet <br /> bsg should also be monitored , as it is a likely horizontal contaminant migration pathway. <br /> Please submit a work plan addendum to provide suitable monitoring wells in this interval . <br /> If submitted promptly, the wells may be installed during the same mobilization for <br /> installation of the approved soil vapor extraction wells : <br />