SITE INFORMATION AND CORRESPONDENCE_FILE 2

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r� Jerry Moore 5491 F Street, Banta, California Page 3 of 3 TPH-mo at concentrations ranging from 1.6 to 5.6 mg/I, the deepest sample being the most impacted. The analytical laboratory noted that the detected chemical(s) did not match the expected pattern for motor oil, but did not identify the 'TPH-mo'further. The EHD is concerned by these data,,which suggest that the 'TPH-mo' originated in the CPT2 area and has migrated at least 70 feet toward the east at approximately 78 feet bsg. The vertical extent of the 'TPH-mo' has not been delineated, nor has the deeper lateral extent. The high groundwater usage of the area requires that the detected 'TPH-mo' be identified and characterized. Submit,a work plan to the EHD by 02 July 2007 to confirm and identify the 'TPH-mo' detected in the CPT1 and CPT2 water samples. Deeper wells in the area may be required to properly monitor the TPH-mo' if confirmed. The CVRWQCB has identified vapor intrusion into structures from impacted soil and/or groundwater to be a concern, therefore you are directed to perform and report a vapor intrusion evaluation, with, emphasis on the onsite structure and adjacent residential structures. By 02 July 2007, submit to the EHD the vapor intrusion evaluation or a work plan to acquire data necessary to perform the evaluation. The ozone sparge system has recently been upgraded to improve ozone injection efficiency. The EHD notes that there are too few observation wells or monitoring wells in the immediate vicinity of the ozone injection Wells to adequately sample and evaluate the system efficiency or efficacy. Propose a method to perform such evaluation or submit a work.plan by 02 July 2007 to address this issue. Currently the.soil vapor extraction (SVE) system is not in operation. Based on the recent reports the system should remain.inactive pending rebound testing. Questions or comments may be directed to Nuel Henderson at (209) 468-3436. Donna Heran, RENS, Director Environmental Health Department Nuel C. Henderson, Jr., PG Margare Lagorio, R HS Engineering Geologist Program Coordinator Unit IV- Site Mitigation Unit IV—Site Mitigation C: James LL Barton, PG—CVRWQCB Daniel Lafontaine, PE—Chemical Engineer—APEX Envirotech, Inc.