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• <br />• <br /> <br />Msrch J992 A'asticiry Evalusrion ~ 1 <br />For the plastic limit test, the sample from the liquid limit test is dried until the sample can be remolded and rolled <br />into a uniform thread approximately l/8-i~h in diameter. Percem moisture at the poim where this thread begins <br />to break into segments approximately 1!8 - 3/8 ioch in length is designated as the plastic limit. Plasticity index <br />is then calculated as the numerical difference between the liquid and plastic limits. <br />2.0 Ewaltratlon of Plasticity Test Results <br />ACZ will review, organize and evaltrate all plasticity test data resulting from the initial sampling. Evaluation will <br />include statistical analysis to determirc minimum maximum values, range, mean and standard deviation for liquid <br />limit, plastic limit and plasticity index. Data will also be analyzed to identify a~ determi~ the extern of any <br />wrrelation between plasticity values for raw and in-place samples, samples corresponding to production from the <br />two differem coal seams, and samples from different placemem periods. <br />Mean plasticity index value and range of values will be reviewed relative to the friction angle assttmptioas utilired <br />in the most recent (1/l4/92) stability analysis and any previously detemrined or assumed values. Var+~n~~ <br />between actual and assumed values will be quantified and both variances and related implications relative to the <br />stability analysis, swctural integrity of the existing refuse stockpile, and current and futtrre placement practices <br />will be presented and discussed in a y~immary evaluation repott. <br />[n the uWikely event thaz plasticity testing indicates much higher plasticity values than assumed in the most recem <br />stability analysis, ACZ wiB rerun the analysis using new material strength parameters consistem with representative <br />plasticity values. Based on the results of this new analysis, ACZ may verify that the existing refuse pile <br />configurationand placemempracticesconform with applicable regulatory requirements, propose additional sampling <br />and testittg to more acctuately define actual material strength parameters for the existing pile, or recommend <br />specific modifications to the stockpile configuration and/or refuse placemem practices. <br />3.0 Ongoing Plasticity Monitoring <br />The Deed for and scope of ottgoing plasticity monitoring will be determired by the resdts of the initial testittg. <br />If testing indicates uniformly low plasticity index values, no additional monitoring may be indicated. Conversely, <br />if some or all plasticity index values are high, more rigorous monitoring may be appropriate to iature the stability <br />of portions of the refuse pile to be conswcted in the future. It is amicipated that actual test results will fall <br />somewhere between these two extremes. EFCI curremly assumes that momhly sampling and testing will be <br />required over a period of six mouths m Due year to documem the normal range of plasticity values and identify <br />any significant variances. The plan for any future plasticity monitoring will be developed and submitted to <br />CMLRD along with the rnmt~ry evaluation report as pan of a technical revision submittal. <br />4.0 Criteria and Designs for Selediwe Placement of Aigh Plasticity Material <br />Initial and ongoing sampling and monitoring will provide the basis for developmem and any recessary fo[[[re <br />modification of the criteria and designs for selective refuse placemem. [f high pLtisticiry materials are identified <br />by sampling and testing, it is anticipated that a plasticity index threshold level will be established as the gttanfitative <br />determinant dictating selective placemem. Based on standard engireering practices and experience on similar <br />facilities, ACZ assttmes that if selective placement is indicated, design plans will involve delireation of critical <br />failure zones, and specification of placemem locations and practices for potentially deleterious reface materials to <br />both keep these materials out of and prevem them from otherwise influencing these critical areas. Criteria and <br />designs for selective placemem will be developed abe submitted to CMLRD along with the a~mmary evaluation <br />repott as pan of a technical revision submittal. <br />r:~.~ueapr.go <br />MrfMR_BUn <br />