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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,R.E.H.S. <br /> 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> JL4 S 1 <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas%V.Nilson, R.1:.II.S. <br /> Program Alanager'91 Telephone: (209) 468-3420 Margaret Lagorio.R.E.H.S./FORS Y <br /> Laurie A.Cotulla,R.E.H.S. Robert McClellon.R.E.H.S. <br /> Program Afanager Fax: (209) 464-0138 Mark Barcellos,R.E.H.S. <br /> MR RUSSELL CHAPIN JAN 0 7 2005 <br /> CHAPIN BROTHERS, INC <br /> 1203 N CARLTON AVE <br /> STOCKTON CA 95203 <br /> RE: CHAPIN BROTHERS Site Code: 1190 <br /> 1766 MON T E DIABLO AVENUE <br /> STOCKTON, CA <br /> The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> the document Response to San Joaquin Environmental Health Department Correspondence <br /> Regarding Request for Closure for Chapin Brothers Investments, Inc. Property at 1766 Monte <br /> Diablo Avenue, Stockton, California (ATC response), dated 23 November 2004 and prepared by <br /> ATC Associates Inc. (ATC). In addition, the EHD has revisited the Closure Report document, <br /> dated 10 August 2004, also prepared by ATC. <br /> The ATC response letter addressed 11 points commented on by the EHD letter dated 04 <br /> November 2004. Very generally, those points included: <br /> 1. Site lithology and its control on hydrology and contaminant migration, <br /> 2. Number of layers utilized in the Modflow model, <br /> 3. Selection of groundwater flow direction, <br /> 4. Selection and use of hydraulic conductivity values in the model, <br /> 5. Effect of engineered remediation vs. natural attenuation, <br /> 6. Recharge flux concentration, <br /> 7. Mass estimate calculation, loading of the hydrocarbon plume and simulation of <br /> biodegradation; <br /> 8. No Further Action Required (NFA) under Section 6.0 of Appendix A of the Tri-Regional <br /> Recommendations Criterion 3, <br /> 9. NFA Criterion 4, <br /> 10. NFA Criterion 5, and <br /> 11. NFA Criterion 6. <br /> Point 1: The EHD had noted that the closure report contained no discussion of hydrologic units <br /> or how the hydrologic units control groundwater movement, flow direction, and, therefore, <br /> contaminant migration. The EHD had also noted that the distribution of dissolved contaminants <br /> had been utilized to infer a predominant flow direction oblique or counter to the flow directions <br /> commonly inferred from the site groundwater elevation data. ATC replied that their two cross <br /> sections are sufficient to determine groundwater flow characteristics. <br />