SITE INFORMATION AND CORRESPONDENCE_FILE 1

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N San Joaquin County Sites Page 2 sections should be prepared by your consultant to identify potential or likely contaminant migration pathways. EDB should be added to the suite of analytes being tested for in the groundwater samples 145 S. SUTTER, STOCKTON (HUMAN SERVICES) The Corrective Action Plan submitted in January 1998 recommended Intrinsic Remediation with Monitoring as the appropriate corrective action for this site. Groundwater monitoring and sampling is ongoing and the concentrations of contaminants in the source area have not declined to a level that would indicate the site should be closed . In addition , the vertical extent of the groundwater contamination in the source area has not been defined . Reviews of the plan were to be conducted at five- year intervals and there has been no review of the plan. Your consultant should review the mass of contaminants remaining at the site and determine if active remediation can be performed or if site closure leaving the remaining mass in place can be justified . 503 E. TENTH, TRACY The contamination at this site appears to be defined . Monitoring and sampling of the groundwater has not been conducted since February 1999 . Two quarterly monitoring events should be conducted and the mass of the contamination remaining should be calculated . If the analytical results of the groundwater samples from the monitoring wells are non detect at appropriate detection limits and the mass calculation shows the water is unlikely to be impacted in the future then a closure report for the site shouldbe prepared . EDB should be added to the suite of analytes being tested for in the groundwater samples. 392 S. MOFFAT, MANTECA This site is currently performing routine quarterly groundwater monitoring and sampling . The work plan to continue the investigation of the vertical and lateral extent of the contamination approved by EHD in June 2003 should be implemented. A site conceptual model and/or cross section should be prepared by your consultant to identify likely contaminant migration pathways . EDB should be added to the suite of analytes being tested for in the groundwater samples 222 E. WEBER, STOCKTON There is a sand lens at 35 feet below grade (bsg) at this site that may be a migratory pathway for the MTBE contamination . It was discussed that placement of soil borings up-gradient (southwest) and cross-gradient (southeast) of MW1 and obtaining soil samples and grab water samples from 35 feet bsg may provide definition for the site. If those samples are non detect then the site should be evaluated to see if further investigation is needed. 130 N. HUNTER, STOCKTON Groundwater monitoring wells were installed in July 2002 and were destroyed in February 2005 because the City of Stockton purchased the site and are having a parking garage constructed . Monitoring wells will be installed following completion of construction activities at the site. The contamination remains undefined . The City of Stockton has taken over as the active responsible party for the site investigation as stated in the purchase agreement.