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t i4 Third Quarter 2004 Quarterly Groundwater Monitoring Report } Stockton Center Site Authority—University Park September 10,2004 1 Page 4 of 5 SUMMARY AND PROPOSED FUTURE WORK The laboratory analytical results of the current monitoring are generally consistent with the historical laboratory analytical results. The current groundwater gradient direction (south) is the southern-most gradient direction estimated for the site during the brief monitoring history. Historic gradient directions have ranged from approximately due east to approximately due south. The site water table elevation has i decreased relatively steadily from approximately 20 feet below mean sea level to approximately 24 feet below mean sea level during the site monitoring history(December 2001 to August 2004). {" Condor prepared a Soil and Groundwater Remediation Work Plan, dated March 3, 2003, at the request of David Rosso, representative for the Stockton Center Site Authority (SCSA). At that time, site development was anticipated to proceed rapidly.and the proposed scope of work for remediation was intended to facilitate the rapid site development by quickly and aggressively cleaning up the site with less regard to cost. The scope of work described in the Work Plan included (1) groundwater dewatering with j dewatering wells, groundwater treatment, and proper disposal of treated groundwater; (2) soil over- excavation, including transport and disposal of contaminated soil; and (3) - in-situ groundwater remediation utilizing ozone sparging technology. In a letter dated March 27, 2003, Mr, Nuel Henderson 1 of the San Joaquin County Environmental Health Department (SJCEHD) approved the soil'over- R excavation portion of the Soil and Groundwater Remediation Work Plan as an interim remedial measure. However, Mr. Henderson also indicated that ozone sparging would not be considered by the SJCEHD until site characterization was complete. As the plan for site development was modified and clarified during the past year, very aggressive and timely but less cost-effective site remediation was deemed unnecessaryb the SCSA. Condor, on Y behalf of the SCSA, is currently proposing evaluation of site source area remediation by pilot testing of air- i sparging in combination with soil vapor extraction. The currently proposed procedures are described by Condor in a work plan to be provided under separate cover. i Condor recommends continued quarterly groundwater monitoring of MW-1, MW-2, and MW-3. The next groundwater monitoring event is tentatively scheduled for November 2004. i j is CONDOR �s