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Mrch 1997 A'uticify Evelustan ~ 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-irch in diameter. Perccm moisture u the poim where this thrall begins <br />to break into segmems approximately 1/8 - 3/8 inch in length is designated u the plastic limit. Plazdcity index <br />is then calculated az the mtmerical difference between the liquid and plastic limits. <br />2.0 Ewaluatlon of Plattlcily Test Results <br />ACZ will review, organize and evaluate all plasricity test data resulting from the initial sampling. Evaluarion will <br />include statistical analysis to determice minimum/maximum values, range, mean and standard deviation for liquid <br />limit, plastic limit and plasticity index. Data will also be analyzed to idemify and determire the extern of any <br />correlation between plazticity values for taw and in-place samples, samples corresponding to production from the <br />two different coal seams, and samples from differem placemem periods. <br />Mean plazticiry index value and range of values will be reviewed relative m the friction angle assumptions util'ved <br />in the most recem (1/14/92) stability analysis and any previously determired or assumed values. Variances <br />between actual and assumed values will be quantified and both variances and rclated implications relative to the <br />stability analysis, structural integrity of the existing refuse stockpile, and currem and future placemem practices <br />will be preserved and discussed in a summary evaluation report. <br />In the unlikely evem that plasticity testing indicates much higher plasticity values than assumed in the most recent <br />stability analysis, ACZ will rerun the analysis using new material strength parameters consistent with representative <br />plasticity values. Based on the results of this new analysis, ACZ may verify that the existing refuse pile <br />configuration and placement practices conform with applicable regulatory requirements, propose additional sampling <br />and testing to more accurately defice actual material strength parameters for the existing pile, or recommend <br />specific modificarions to dte stockpile configuration and/or refuse placemem practices. <br />• 3.0 Ongoing Plasticity Monitoring <br />The need for and scope of ongoing plasticity monitoring will be determiced by the results of the initial testing. <br />If testing indicates uniformly low plasticity index values, tto additional mommring may be indicated. Cowersely, <br />if some or all plasticity ibex values are high, more rigorous monitoring may be appropriate to insure the stability <br />of portions of the refuse pile to be constructed in the future. It is anticipated drat actual test results will fall <br />somewhere between these two extremes. EFCI currently azsumes that monthly sampling and testing will be <br />required over a period of six mo[[[bs to one year to documem the normal range of plazdciry values and identify <br />any significant variances. The plan for any future plasticity monitoring will be developed and submitted to <br />CML.RD along with the summary evaluation report az pan of a technical revision submittal. <br />4.0 Criteria trod Designs for Selective Placement of High Plasticity Material <br />Initial and ongoing sampling and monitoring will provide the basis for developmem and any necessary fo[[[re <br />modification of the criteria and designs for selective refuse placemem. If high plasticity tttarerials are identified <br />by sampling and testirtg, it is anticipated that a plasticity index threshold level will be established az the quantitative <br />determinant dictating selective placement. Based on standard engineering practices and experience oa similar <br />facilities, ACZ assumes that if selective placemem is indicated, design plain will involve delineation of critical <br />failure zones, and specification of placement locations and practices for potentially deleterious refuse materials to <br />both keep dtese materials out of and prevem them from otherwise infiuertcing these critical azeaz. Criteria and <br />designs for selective placement wiB be developed and submitted to CMI-RD alottg with the summary evaluation <br />repon az part of a technical revision submittal. <br />• <br />~:~.ar~~eeo~gw.~ <br />lyFM9I Sup <br />