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Ms . Bazeley <br /> June 5, 1996 <br /> Page 2 <br /> indication of the changes that occur in the extracted vapors and <br /> determine whether the SVE system has reached its "stabilization <br /> asymptote" . Additionally, DTSC requires that a minimum of 100-. <br /> soil gas samples should be delivered to a state certified <br /> laboratory for a complete VOC analysis using the modified EPA <br /> Method TO-14 . Samples should be analyzed within 24 hours upon <br /> collection of the samples . <br /> Please note that the above sample analysis requirement <br /> .applies to the full-scale SVE operation. It does not apply to <br /> the pilot testing period. During pilot testing, soil gas samples <br /> shall be analyzed by FID for total VOC concentrations, and by an <br /> off-site laboratory for a complete analysis of VOC <br /> concentrations . <br /> DTSC has two major concerns regarding the proposed <br /> performance goals : <br /> (1) DTSC does not understand why WZI believes that the 21 <br /> variation in mass removal rates will be feasible while the 201 VOC <br /> concentrations variation will not . WZI should know that the <br /> removal rates are calculated by multiplying VOC concentrations in <br /> the extracted vapor with flow rates (removal rate = VOC <br /> concentration x flow rate) ; and <br /> (2) DTSC is deeply troubled by the rationales of laboratory <br /> tolerance for analytical error and field sampling technique <br /> repeatability cited by WZI . DTSC reviewed the draft workplan for <br /> SVE testing at the Guild and Lustre-Cal sites in October 1995 and <br /> has required that procedures used for sample collection, storage, <br /> and delivery to a laboratory for analysis be incorporated into <br /> the final workplan for DTSC' s review and evaluation. To date, <br /> DTSC has not received any document regarding the required <br /> material . DTSC also cautions that it is essential for WZI field <br /> personnel to comply with the approved sampling procedures to <br /> minimize any problems that may be created by not following those <br /> procedures . <br /> 4 . Page 6 . "Secondary Cleanup Criterion" . The fourth <br /> paragraph: "Once the SVE reaches its asymptote, the operator will <br /> shut down the SVE units and begin rebound and . . . " <br /> DTSC Comment: Add the word "monitoring" or "assessment" <br /> after the word "rebound" . <br /> 5 . Page 7 . The second paragraph. "Monitoring events will <br /> include collection of "static" soil gas samples (undisturbed <br /> samples) from each of the extraction wells . Extraction wells <br /> will be monitored at biweekly intervals during early rebound <br />