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"IMV <br />om <br />San Joaquin County <br />Environmental Health Department <br />600 East Main Street <br />Stockton, California 95202-3029 <br />Website: www.sjgov.org/ehd <br />Phone: (209) 468-3420 <br />Fax: (209) 464-0138 <br />April 12, 2010 <br />Mr. Donald Helsel <br />Earthgrains Baking Companies, Incorporated <br />2651 South Airport Way <br />Stockton, California 95206 <br />Subject: Earthgrains Baking Companies, Incorporated <br />2651 South Airport Way <br />Stockton, California 95206 <br />DIRECTOR <br />Donna Heran, REHS <br />PROGRAM COORDINATORS <br />Robert McClellon, REHS <br />Jeff Carruesco, REHS, RDI <br />Kasey Foley, REHS <br />On April 5, 2010, a conference call was conducted between personnel from the San Joaquin <br />County Environmental Health Department (EHD), and PSC Industrial Outsourcing, LP, <br />(PSC) to discuss the EHD requirements to obtain closure for the above -referenced site. <br />Discussions focused on the groundwater fate and transport modeling, trend analysis, vapor <br />intrusion survey, and remedial alternatives for the site presented in Feasibility <br />Study/Remedial Evaluation and Case Closure Request Report dated October 7, 2009, <br />prepared and submitted by PSC. <br />PSC clarified the field data input parameters for the Bioscreen model used for fate and <br />transport modeling, and stated that the analysis demonstrates that the chemicals of concern <br />are immobile and if chemical degradation did not occur, it would take approximately fifty <br />years for the contaminants of concern to reach the property boundaries. In response, the <br />EHD stated that it appears that concentrations of benzene have been increasing <br />significantly in groundwater samples collected from piezometer PZ -2 between 1999 and <br />2009, and concentrations of total petroleum hydrocarbons quantified as gasoline (TPH-g) <br />demonstrate an overall increasing trend in groundwater collected from PZ -2 during this <br />same time -period. <br />The EHD expressed the need to perform remediation at the core of the petroleum <br />hydrocarbon plume to reduce the contaminant mass and demonstrate a declining trend of <br />petroleum hydrocarbon contamination. Discussions focused on the remedial methods <br />proposed by PSC in the feasibility study/remedial evaluation. PSC agreed to evaluate three <br />remedial alternatives: enhanced bioremediation by biosparging, in-situ air stripping, and in- <br />situ chemical oxidation, and recommend one of these remedial methods based on site <br />specific conditions and data, and provide technical justification to support the anticipated <br />success of the proposed remedial method. Please submit the evaluation of these three <br />remedial alternatives to the EHD by June 15, 2010. <br />The EHD agreed to discuss the site conditions with the Central Valley Regional Water <br />Quality Control Board (CVRWQCB) before deciding whether it is necessary to collect soil <br />gas samples to evaluate the potential for soil vapor intrusion into buildings. If soil gas <br />