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EPA COMMENTS ON <br /> THE DRAFT ENGINEERING REPORT <br /> FOR WELL EVALUATION AND ABANDONMENT (JULY-92) <br /> AT DDRW-TRACY <br /> GENERAL COMMENTS <br /> 1. Field procedures deviated only slightly from those suggested <br /> in the Final Work Plan for Well Evaluation and Abandonment <br /> at DDRW-Tracy, dated February 1992 . For example, the Work <br /> Plan calls for the first soil cuttings samples from -Wells 1 <br /> and 2 to be taken from depths of 31 to 35 feet; the first <br /> cuttings samples were actually taken from about 20 feet from <br /> Well 1 and from three to eight feet from Well 2 . Also, Well <br /> 1 could not be drilled down to its total depth. Such <br /> deviations as these are entirely reasonable when considering <br /> actual field conditions. (No response necessary. ) <br /> 2 . In spite of the locations of these wells within the <br /> contaminant plumes, the results of analyses of the <br /> groundwater samples and drill cuttings (soil) from Wells 1 <br /> and 2 , and of groundwater samples from Wells 4 and 7 showed <br /> no trichloroethene (TCE) or tetrachloroethene (PCE) to be <br /> present in these wells. <br /> 3 . Although benzene and 0-xylene were detected in drill cutting <br /> (soil) samples retrieved from Well 1 at a depth of 650, the <br /> samples retrieved from shallower depths in that well were <br /> either analyzed beyond the holding times for these <br /> constituents or were analyzed using elevated detection <br /> limits . These circumstances make it difficult to evaluate <br /> the significance of the results of the positive analysis for <br /> these aromatic volatiles. <br /> 4 . Groundwater samples from a depth of 145 feet in Well 2 <br /> analyzed filtered (dissolved) mercury above the Maximum <br /> Contaminant Level (MCL) of 2 µg/L for that compound. <br /> Likewise, dissolved manganese was analyzed above the <br /> Secondary MCL of 50 µg/L in every groundwater sample from <br /> Wells 1 and 2 . Contamination from these and other metals <br /> must be addressed in the upcoming Comprehensive Remedial <br /> Investigation/Feasibility Study (RI/FS) at DDRW-Tracy. <br /> 5 . Bromoform was detected in two of the groundwater samples <br /> from Well 1, in the waste water from Well 1, and in the <br /> analysis of the drilling fluid. At no point does the text <br /> detail the chronology of the field procedure for retrieval <br /> of the drilling fluid sample. Only one sample of drilling <br /> fluid was analyzed and according to the chain of custody, <br /> that sample was retrieved on May 7 , 1992 , the day Well 2 was <br /> 1 <br />