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<br />run on the actual amended gob pile material being placed GVhether or not one or several <br />test samples are taken jot analyses depends on whether the material in the gob pile is <br />homogeneous or stratifred !n this wav, a comparison can he made benveen the properties <br />oJ~the coal waste material and the properties of the composite material. 4Pith this <br />comparison, it can be determined whether or not additional laboratory tests and an <br />accompanying slope stability analysis need be completed. Plense comment. <br />[n the September 28, 1998 letter to the Division, it was stated that Norm Johnston. P.E. of <br />Lambert & Associates, geotechnical consultant to BRL advised Mr. Stover that there was <br />no reason to be concerned with relative compaction results in excess of 100%. The <br />Division concurs that it is not uncommon to determine field densities of up to l1~%of <br />proctor standazds. However, the Division believes that results which routinely exceed <br />11 ~% of the Proctor optimum dry density aze unlikely. Results exceeding 11 ~% of <br />optimum dry density suggest that the Proctor was performed on a soil which is not <br />representative of the material being tested. The Division does not consider Mr. Stover's <br />response adequate to resolve its concern stated in our previous adequacy letter. <br />The Division reiterates its eazlier request that BRL develop an acceptable methodology <br />for verifying that the proctor standazd being applied during a compaction test is <br />appropriate for the materials being inspected. The brute force approach is Co perform a <br />proctor analysis every time a compaction testing is performed. That approach is <br />expensive and time consuming, and normally unnecessary. Ofren, if concern exists on <br />the part of the engineer in chazge of the inspection, a sieve analysis may serve to <br />determine mechanical similarity of the standazd and the tested specimen. If the materials <br />aze shown to be similaz in gradation, fine content, and visual constituency, they can be <br />assumed to be representative. In some cases, however, it materials aze variant because of <br />source variation or amendment, numerous proctors may need to be completed. <br />Another common cause of compaction test inaccuracy is failure to properly analyze the <br />constituency of the sample tested. It has been the Division's experience that modern <br />nucleaz density testing standazds aze cottunonly misapplied. The nucleaz probes measure <br />the average density of a sphere approximately one foot in radius azound the probe. If one <br />or more coazse cobbles exist within that sphere, they will bias the compaction results <br />upwazd. Standazd methodology dictates that the operator excavate a one foot radius <br />sphere afrer the probe reading is completed, in order to verify that the material tested is <br />appropriately devoid of coazse materials. The Division's experience suggests that <br />technicians may fail to complete this important verification step. Further, if the <br />excavation determines that the test was biased by coazse material, it should be repeated <br />until successful. The same concerns apply to older sand replacement testing methods. If <br />coazse material exists within the volume of soil excavated during the test, the test should <br />be repeated. <br />Yet another source of inaccuracy results from the failure to apply the correct proctor test <br />