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<br />specitication to analyzing coarse materials. If the amended waste material contains a <br />significant fraction as larger than #4 sieve size, one of the material replacement methods <br />must be used to complete the analysis. [f incorrectly applied, selection of the wrong <br />analytical method will also bias the proctor test results. <br />If the wrong Proctor standards are applied in performing compaction tests of the <br />compacted GOB the operator may construct an unstable pile. It is important that an <br />acceptable comprehensive compaction testing control methodology be developed and <br />approved for the Bowie No. 2 GOB pile. The longer this task is delayed, the greater the <br />likelihood that the portion of the pile constructed prior to that approval may require <br />remedial treatment. <br />3. The Division is concerned that, ifsubsoil is being used to mir with overly wet coal mine <br />waste material, there might not be enough subsoil stockpiled at the coverfill stockpile to <br />use as cover over the gob pile when the pile is reclaimed. Please comment. <br />BRL has submitted a volume estimate of 11,500 cubic yazds for the subsoil in the <br />coverfill stockpile. At a reclamation replacement depth of 3.5 feet, this amount of subsoil <br />would cover a little over 2 acres of coal waste. The entire gob pile will cover about 5.5 <br />acres in aerial extent. BRL is actively removing additional subsoil as the gob pile <br />progresses up the hill and placing the subsoil onto the gob pile bench outslope for <br />reclamation. The Division encourages BRL to enstue that enough subsoil, and topsoil for <br />that matter, aze stripped off of the hillside as the gob pile advances, so that shortages will <br />not occur when the gob pile is complete. <br />4. The Division is concerned that no compaction tests have been performed to date at the <br />gob pile. It is the Division's opinion that compaction testing should be performed at least <br />quarterly, possibly on each two foot lift, and especially in the very early stage of the gob <br />pile's development. In that way, the geotechnical engineer would be able to determine <br />whether or not the gob pile construction was proper, so that any remediation work, if <br />needed, would not be costly and di~cult. Please comment on why no compaction testing <br />at the gob pile has been done to date, considering how much material has already been <br />placed there. Also, please comment on how the operator is confident that the compaction <br />at the gob pile has occurred according to design. <br />BRL stated, in the September 28, 1998 letter, that it has not been decided which <br />methodology will be used to determine the relative compaction of the initial gob <br />placement. The use of remote density probes work well in fine grained sands and clays. <br />The Division's experience with this equipment suggests that difficulty will be <br />encountered in coarse, gravelly materials. The probes require the installation of a tightly <br />fit liner tube to accommodate the remote probe. Coarse soils make installation of the <br />container tube challenging, if not impossible. The operator may want to consider the <br />simplistic approach of test pit excavation to accommodate the density testing procedure. <br />3 <br />