SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Mr. Russell Chapin 1766 W.Monte Diablo Avenue Page 3 of 5 2001, and groundwater extraction (GWE)was initiated in April 2002. As of September 30, 2003, 2,459,704 gallons of groundwater had been extracted, yielding a recovered benzene mass of 5.69 pounds and TPH-g mass of 140 pounds. As of the fourth quarter of 2004, AGE estimates that 6.46 pounds of benzene and 178.7 pounds of TPH-g have been recovered. Since the site was placed in LOP, the EHD has met with Mr. Chapin on numerous occasions and has discussed the site several times with CVRWQCB staff. The LOP staff meets monthly to discuss general and site-specific issues; the meetings are attended by CVRWQCB staff. On October 15, 2003, an LOP staff meeting was held, which was attended by Brian Newman and Jim Barton of CVRWQCB. At the conclusion of this staff meeting, Bill Little of AGE, Mr. Chapin's consultant, met informally with the EHD and CVRWQCB staffs to discuss Mr. Chapin's site. According to Mr. Little, Mr. Chapin was aware of the meeting. It was not the intention of either the EHD or CVRWQCB staff to exclude Mr. Chapin from the meeting or to issue directives affecting his site, but was to discuss the value of continuing the GWE effort. Mr. Newman noted the persistent contaminant concentrations in the extracted groundwater and was concerned that soil washing may be occurring. Approval was given for Mr. Little to turn off the GWE system for 30 days and consider the results. When tested a month after shutting down the GWE, concentrations had rebounded, so the system operation was restarted. On December 19, 2003, the EHD met with Mr. Chapin and his consultants (AGE representatives, Bob Marty and Bill Little, and ATC Associates Inc. representative, Drew Van Allan) to discuss the site status and closure requirements. Margaret Lagorio, Nuel Henderson and Harlin Knoll represented the EHD. Jim Barton representing the CVRWQCB was also present. At this meeting, Mr. Chapin presented a history of the site investigation and requested closure consideration. The AGE representatives presented the results of the soil investigation under the building and the last quarterly groundwater monitoring results. The EHD informed Mr. Chapin that his consultant must submit a report of the work done and give recommendations for closure or future monitoring, etc., for the site. By the end of the meeting, both ATC and AGE recommended that the pump and treat system should be operated until the closure report had been prepared. During the December 19, 2003, meeting, Nuel Henderson, R.G., of the EHD described what would be necessary to produce a model demonstrating that the site merited closure consideration while leaving a large mass of contaminants in place. Included in such a model would be a hydrogeological site model, a reliable updated estimate of dissolved and sorbed contaminant masses and their distribution, the contaminant flux rate between sorbed and dissolved states, and the groundwater seepage rate. These components would be a necessary part of the overall model in order to develop a reliable fate and transport model for the site. On August 13, 2004, the EHD received the Closure Report dated August 10, 2004, prepared by ATC. ATC had utilized the Modflow program to develop a hydrogeological model and the MT31D program to model contaminant fate and transport. Based on the conclusions drawn from the model results, ATC recommended immediate site closure with no further groundwater monitoring. The EHD carefully reviewed the ATC model, testing each statement, model component and reasoning. On October 4, 2004, EHD issued a comment letter on the August 10, 2004, Closure Report. The EHD could not concur with the request for closure or for immediate cessation of groundwater monitoring, due to weaknesses EHD identified in the model and detailed in the comment letter.