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HARLAN & ASSOCIATES, INC. <br /> Mr. Kevin Riordan <br /> District Ranger <br /> U.S. Forest Service <br /> October 23, 1996 <br /> Page 3 <br /> Corrosive Character <br /> Based on the sample results, the waters in Coal Basin area are not regarded as being <br /> corrosive, but tend to be slightly encrusting. It is noted, however, that Mancos Shale outcrops <br /> locally within Coal Basin and is known to produce hydrogen sulfide (H2S) which is corrosive. <br /> The generation of H2S occurs naturally and is unrelated to past mining or coal processing <br /> activities in Coal Basin. <br /> Although there are minor differences between sampling locations, both surface- and <br /> ground-water quality throughout the Coal Basin area are good. With respect to pH, the waters <br /> are typically neutral to slightly basic and contain relatively small concentrations of total dissolved <br /> solids. Specific conductance measurements on Dutch Creek and Coal Creek, for example, were <br /> typically less than 250 µmhos/cm which indicates small concentrations of dissolved soils. With <br /> the exception of the discharge from the twin haulage tunnels and that from the 016 ponds, (2300 <br /> and 1680 µmhos/cm, respectively), the measured specific conductance values were normally less <br /> than 1000 µmhos/cm at all other locations sampled including those sites monitored downgradient <br /> from the old refuse and Sutey Piles. <br /> Pre-Law Waste Piles <br /> For the purposes of the Coal Basin Mine environmental site assessment, no distinction <br /> was made between pre-law and post-law activities, waste disposal areas, and so forth. <br /> Consequently, all sampling locations were determined for the site as a whole. <br /> During the environmental site assessment, ground water in the immediate vicinity of the <br /> iron seep located on the south bank of Coal Creek east of the entrance gate was sampled at three <br /> locations (i.e., Seeps #1, #2 and #3). These samples were collected from along the edge of the <br /> river bank above the perimeter drainage ditch in order to minimize possible effects from the <br /> perimeter ditch on water quality. <br /> As indicated, the samples collected from Seeps #1, #2, and#3 were analyzed for volatile <br /> organic compounds (VOCs), RCRA metals, PCBs, and general inorganic parameters. The <br /> analytical results for these samples indicate that the ground-water quality is consistent with that <br /> observed elsewhere and that the concentrations of inorganic constituents are within the expected <br /> range. <br />