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��ENT <br /> HEALLTA�JEPAR <br /> ENV�ROI�VIEN <br /> O Pp.0 IN.. SAN JpAQVIN COUNTY program Coordinators <br /> �. 1` <br /> ?� gonna K. Heran, R.E.H.S. 304 East Weber Avenue,Third Floor Carl Borgman,R.E.lLS. <br /> Director Mike Huggins, R.E.H.S., R.D.I. <br /> Laurie A. Cotulla,R.E.H.S. Stockton,California 95202-2708 Margaret Lagorio,R.E.H.S. <br /> • c...-�--:;P• Assistant Director Telephone: (209)468-3420 Robert McClellon,R.E.H.S. <br /> 4�;F�•aa <br /> Fax: (209) 464-0138 Teff Carruesca, R.E.H.S. <br /> Website:www.sjgov.org/ehd/ Kasey Foley,R.E.H.S. <br /> ,FEB 0 9 2001 <br /> DON PRATT <br /> ATLANTIC RICHFIELD COMPANY M HAMZEH Y HAJIAN PPT <br /> PO BOX 1257 111 QUINTAS LANE <br /> SAN RAMON CA 94583 MORAGA CA 94556 <br /> RE: Former ARCO Station #548 SITE CODE: 1127 <br /> 1612 Hammer Lane <br /> Stockton CA 95209 <br /> San Joaquin County Environmental Health Department (SJCIEHD) has reviewed Revised <br /> Work Plan for Biosparging Feasibility Testing dated December 19, 2007 submitted on <br /> your behalf by SECOR International Incorporated (SECOR) and has the following <br /> comments. <br /> In this revised work plan SECOR proposes to use existing onsite air sparge (AS)wells to <br /> conduct a feasibility test of the potential for injection of air to increase the concentration of <br /> oxygen in the shallow groundwater at this site, and to hopefully promote biodegradation of <br /> the petroleum hydrocarbon contamination remaining in the groundwater. <br /> As discussed at a meeting held on December 7, 2006 and attended by SECOR, ARCO <br /> and SJCIEHD personnel, 'baseline data' will be collected for three months by analyzing <br /> groundwater samples from all wells onsite for dissolved oxygen, carbon dioxide, oxidation <br /> reduction potential, nitrate, sulfate, chemical oxygen demand, ferrous iron, total iron, total <br /> dissolved solids, total organic carbon and heterotrophic plate count. Following three <br /> months collection of data, the existing air sparging system will be modified to maintain <br /> flow rates between 2 and 6 standard cubic feet per minute, and restarted. SECOR will <br /> operate the AS system for a period of one year, collecting groundwater samples monthly <br /> and analyzing for the above listed parameters. After one year of operation SECOR will <br /> evaluate how effective the air sparge system is in remediating the groundwater <br /> contamination at this site. SJCIEHD approves initiation of work proposed in the revised <br /> work plan on the condition that the system will be shut down if there is any indication that <br /> the sparging is causing transport of the plume offsite. During monthly sampling of all site <br /> wells for the parameters listed above, down-gradient wells MW-5, MW-7 and MW-6 <br /> should also be analyzed for petroleum hydrocarbons. <br /> Two other site issues were discussed at the meeting but not addressed by SECOR in the <br /> revised work plan. The first was the concentration of 1,2-dichloroethane (1,2-DCA) in <br /> onsite monitoring wells, which SECOR said would not likely be affected by increased <br /> oxygen concentrations. It was expected that SECOR would examine the 1,2-DCA issue <br /> and provide comment. The Regional Water Quality Control Board (RWQCB) is not <br />