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N"Nw <br /> DEPARTMENT <br /> ENVIRONMENTAL HEALTH <br /> SAN JOAQUIN COUNTY <br /> • —�-�'' �� Unit Supervisors <br /> y. : . 304 East Weber Avenue, Third Floor <br /> Donna K.Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • cq. ��p Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> F o R Laurie A.Cotulla,R.E.H.S. <br /> Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> NOV 10 2003 <br /> JERRY MOORE <br /> 54:91 F STREET �� <br /> BA CA 04 <br /> RE: Work Plan for Ozone Sparging Site Code: 1502 <br /> 5491 F Street_ <br /> Banta CA 95304 <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Work Plan for Ozone Sparging (WP), dated 26 September 2003, <br /> prepared by Apex Envirotech, Inc. (AEI). The site has been under soil vapor <br /> extraction (SVE) remediation off and on since 1995. To date, approximately <br /> 4,369 pounds of hydrocarbons have been removed from the vadose zone with <br /> the current remediation system. Contaminant concentrations in ground water has <br /> not responded as well as was expected, therefore AEI proposes to enhance the <br /> SVE system by adding an ozone sparging system to breakdown dissolved <br /> hydrocarbons and other fuel components. <br /> To better evaluate this WP, EHD reviewed various quarterly reports, boring logs, <br /> and previous directives to characterize the site status. The subsurface of the site <br /> appears to consist predominantly of silt and minor clay at 5 feet bsg; primarily of <br /> sand at 10, 15 and 20 feet bsg; and more commonly silt and/or clay, and less <br /> commonly sand at 25 feet bsg. Limited data suggest that sand occurs between <br /> 30 and 40 feet bsg. The thick sand sequences are suggestive of deposition in or <br /> near a former stream channel. The fine grained soil at 25 feet bsa does not <br /> appear to be an effective barrier to vertical migration of dissolved contaminants <br /> as sand occurs locally at that depth. <br /> The vertical extent of impacted soil appears to be reasonably delineated. Data <br /> reviewed by EHD is too limited to determine if the lateral extent of impacted soil <br /> has been delineated, but most of the impacted soil appears to occur at 10 feet <br /> bsg in the data reviewed, suggesting smear zone contamination on the capillary <br /> fringe. <br /> Ground water occurs at approximately 11 feet bsg and the depth to water has <br /> varied by only a few feet since monitoring began on the site (circa 1988). Ground <br /> water flows predominantly toward the northeast, on occasion varying toward the <br />