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Jim Tjosvold, P.E. Page 4 September 21 , 1987 Comment 9 The Department acknowledges McCormick and Baxter's commitment to defining all boundaries of groundwater contamination and agrees to postpone requirements for wells in the northern boundary until the next phase of investigation. Comment 13 and 23 The requirement for second column confirmation is not a requirement specifically for the McCormick and Baxter site, but pertains to the consultant's analytical laboratory. All laboratories certified by the State to analyze hazardous waste must comply with this requirement as of June 8, 1987 . HML has been notified of CH2M Hill 's position. McCormick and Baxter may be eligible for an exception to this rule. Conditions for the exception are for monitoring wells which have been previously confirmed, have gas chromatograms that are not complex, have chromatograms which are largely unchanged from those which were confirmed, and that representative samples be periodically (semiannually) confirmed. Before McCormick and Baxter is eligible for this exception, all wells must be confirmed initially. CH2M Hill has already sampled all wells on site where this requirement would have the largest effect. McCormick and Baxter and their consultant laboratory are still bound to this requirement and must address how they will attempt to fulfill it. Comment 16 The request to not filter water samples is based on scientific data which shows that metals will begin to precipitate immediately after exposure to air or adsorb to particulates. If these precipitates or particulates are removed by filtering after the sample was collected, then groundwater results would be artificially low. McCormick and Baxter is concerned that the sample preservation will extract natural metals from soil particulates and cause high results. To satisfy both parties, samples should be collected from an in-line filter, thus removing iron precipitates and soil particulates immediately before absorption can occur. If McCormick and Baxter does not agree to in-line filtering for all samples, then results of both techniques must be shown to determine that there is no effect. Comment 19 McCormick and Baxter has not agreed to sample wells OS-1E and OS-3E on a quarterly basis. The response from CH2M Hill does not include all the possibilities for contaminant migration. Depth sampling from OS-3E shows contamination to a depth of 152 feet. This may continue to migrate down to the E zone.