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Ms. Diane Hinson <br /> February 14, 1994 <br /> Page- 2 <br /> "commended us for excellent" results. These samples were prepared by the <br /> freon extraction procedure used on the Catellus project, not purge & trap. We <br /> perform these test samples regularly, and can send you additional sets if you <br /> desire more data. <br /> Hopefully, these performance test data demonstrate to you the validity of the <br /> data generated by this procedure. As I attempted to explain in my letter to Mary <br /> Meays dated November 29, 1993, the procedure is clearly quantitative, i.e., <br /> volatiles are not lost in the vial head space. Rather, like any preparation <br /> procedure (extraction or purge & trap), the more important factor is the recovery <br /> of the analytes from the soil matrix, which is matrix dependent. To monitor this, <br /> we add surrogates to all the samples and reject the data if the surrogate <br /> recovery is less than 65%. Further, we perform matrix spikes & spike duplicates <br /> to ensure that recoveries are within acceptable ranges. if you review these QC <br /> data for the Catellus project, you'll see that all recoveries were within acceptable <br /> limits. <br /> Finally, when we were advised that you had a concern on the final day of the <br /> confirmation sampling at the subject site, we ran the samples from the last day <br /> by extraction and purge & trap. The same results were obtained by both <br /> methods. Note also that the matrix spike data from the extraction preparation <br /> method show equally good recoveries when compared to the spikes done by <br /> purge & trap on the last day. <br /> Regarding the issue on what procedures are or are not certified, the SW846 <br /> manual states on the first page of the Preface & Overview section that the <br /> procedures contained therein are not requirements, but guidelines (relevant <br /> page attached). The manual allows for flexibility and the skill, training, and <br /> experience of the analyst to make modifications, so long as the modifications <br /> can be documented to provide accurate data. As a consequence, modifications <br /> are done all the time by laboratories, the most obvious one being the California <br /> LUFT TPH method. We did inform the Los Angeles office of ELAP of the validity <br /> of the BTEX analysis by freon extraction in correspondence dated March 3, <br /> 1992, a copy of which is also attached. We have had many agencies visit our <br /> mobile laboratories (San Diego HMMD, LA Public Works, LA-DTSC) and have <br /> had many audits by both public & private groups, and all have been satisfied by <br /> our protocols. <br />