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Memo to Joe Dudash <br />Bowie #2 Gob Response <br />page 2 <br />in radius around the probe. If one or more coarse cobbles exist within that sphere, they will bias <br />the compaction results upward. Standard methodology dictates that the operator excavate a one <br />foot radius sphere after the probe reading is completed, in order to verify that the material tested <br />is appropriately devoid of coarse materials. Franlay, many technicians tail to complete this <br />important verification step. Further, if the excavation determines that the test was biased by <br />coarse material it should repeated until successful. Many technicians lose interest after several <br />attempts. The same concerns apply to older sand replacetent testing methods. If coarse <br />material exists within the volume of soil excavated during the test, the test should be repeated. <br />Yet another source of inaccuracy results from the failure to apply the correct proctor test <br />specification to analyzing coarse materials. If the amended waste material contains a significant <br />fraction as larger than #4 sieve size, one of the material replacement methods must be used to <br />complete the analysis. If incorrectly applied, selection of the wrong analytical method will also <br />bias the proctor test results. <br />If the wrong Proctor standards are applied in performing compaction tests of the compacted GOB <br />the operator may construct an unstable pile. It is important that an acceptable comprehensive <br />compaction testing control methodology be developed and approved for the Bowie No. 2 GOB <br />pile. The longer this task is delayed, the greater the likelihood that the portion of the pile <br />constructed prior to that approval may require remedial treatment. <br />Compaction Testing of Lowest 20' Lift (Item #4) <br />The use of remote density probes work well in fine grained sands and clays. My experience with <br />this equipment, gained first hand in the City of Boulder, suggests that difficulty will be <br />encountered in coarse, gravelly materials. The probes require the installation of a tightly fit liner <br />tube to accommodate the remote probe. Coarse soils make installation the container tube <br />challenging, if not impossible. The operator may want to consider the simplistic approach of test <br />pit excavation to accommodate the density testing procedure. This would necessitate backfilling <br />and recompaction of the test pits, but may be considerably less demanding. <br />Underdrain Material Gradation (Item #5) <br />The submitted gradation results confirm specification compliance. <br />Cc: Larry Rouuen <br />doc: M:\COALVAP\Bo++2GobR.wPD <br />1P/1P <br />