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Page 2 <br /> Former Stefano's Gasoline Station February 23, 2011 <br /> 1419 East Charter Way <br /> Stockton, California 95205 <br /> was not detected in soil samples collected from OZ-4 at 10 and 15 feet bsg using a photo- . <br /> ionization detector (PID)., <br /> The EHD has reviewed current and historical data rfor this site. Samples collected from monitoring <br /> well MW-2'appear to be the only impacted groundwater.' Results for groundwater collected from <br /> MW-2 have not demonstrated a significant influence from the SVE system that operated between <br /> November 2004 and June 2005; nor have the groundwater data demonstrated a significant <br /> reduction in contaminant contaminations from the ozone injections. Hopefully, the installation of <br /> the additional,ozone injection point in. October 2010_and the anticipated start up of the ozone <br /> system by 28-February 2011 will reduce the concentrations of contaminants in groundwater from <br /> MW-2. <br /> Confirmation samples P-1 through P-3 were collected west and south of MW-2; and soil sample <br /> OZ4-5 was collected approximately seven feet west/northwest of MW-2 at 5 feet bsg in the former <br /> tank pit area presumably where clean fill was utilized to backfill the excavation following the tank <br /> removal. There has been no sample collected in shallow soil between the former excavation and <br /> the motel building located approximately 20 feet north of MW-2. Boring B-1, impacted to at least <br /> 40 feet bsg, advanced approximately 7 feet north of MVV-2, has soil data from only 30 to 60 feet <br /> bsg. <br /> rt the presence of a motel approximately 20 feet from <br /> structure on this roe p , <br /> Although there is no strut property,Y, <br /> the most impacted well, MW-2, requires a high confidence level that there is minimal potential for <br /> a vapor intrusion problem: Thiscan be addressed by advancing a confirmation boring north of the <br /> former tank pit, between MW-2 and the motel, or collecting a soil gas sample for laboratory <br /> analysis. Soil samples should be collected at 5, 10 and 15 feet bsg for chemical analysis: The <br /> concentrations of any petroleum hydrocarbon contaminants detected in the three soil samples <br /> should be compared to ESLs for gross contamination and direct exposure, and to the California <br /> Human Health Screening Levels (CHHSLs) established by the California 'Environmental <br /> Protection Agency and the potential risk from vapor intrusion should be evaluated. A work plan to <br /> advance the confirmation boring may be submitted following remediation by ozone injection. <br /> In the fourth quarter report "AGE recommends incorporating the newly installed ozone injection <br /> well into the on-site ozone injection system:" .The EHD assumes that the newly installed injection <br /> well will be incorporated into the ozone injection system without direction from this office. . <br /> If you have any questions, please contact Vicki McCartney at (209) .468-9852 or by e-mail at <br /> vmccartney@sjcehd.com. <br /> Sincerely, <br /> 4 <br /> � <br /> /&at <br /> Victoria L. McCartney, REHS Nuel C. Henderson, Jr., PG <br /> Health <br /> Senior Registered red EnvironmentalSpecialist Engineering Geologist <br /> Sen g <br /> I� <br /> c: Mr. Brian W. Millman, PG, Advanced GeoEnvironmental, Inc., 837. Shaw Road, Stockton, <br /> California 95215 <br /> } Mr. James L.L. Barton, PG; California,Regional Water Quality Control Board. Central Valley <br /> Region, 11020 Sun Center Drive, Suite-200, Rancho Cordova, California 95670 <br />