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Memo to Shawn Smith <br />Southfield Stability Analysis <br />page 2 <br />In closing this report, Mr. Nettleton observed that "it may be prudent to <br />sample and test plasticity characteristics of the fine refuse to identify an <br />acceptable range. If high clay content material is encountered in the mining <br />operations, it could be sampled and compared with this range, with selective <br />placement in the pile to avoid adverse stability impacts if high plasticity is <br />indicated." <br />Conclusion and Recommendation: <br />In my opinion, each of Mr. Nettleton's assumptions and conclusions is <br />appropriate. His report clearly explains his rationale in arriving at his <br />conclusions. I do not disagree with any of his assumptions or conclusions. <br />The Southfield coal mine refuse pile has been under construction since 1981. <br />I have visited the pile at least annually during the past decade. I have <br />never observed any indication of slope instability, deep or surficial. In <br />consideration of your recent notice of violation, I briefly examined the top <br />of the refuse pile during our visit last month. The operator had constructed <br />a safety and drainage control berm around the periphery by depositing coarse <br />refuse in a linear pile along the outer edge. I suspect that this practice <br />has resulted in selective placement of coarse refuse in the outer most zone of <br />the refuse pile. This practice has helped to preclude the occurrence of near <br />surface failures, which one might anticipate if fine material was placed at <br />the outer face of the pile. <br />Because of the possible high-clay refuse constituency and strength variation <br />which Mr. Nettleton discusses in his report, I believe it would be desirable <br />to impose the following condition upon acceptance of this abatement <br />submittal. Southfield Mine should prepare a method to monitor the plasticity <br />of the fine waste fraction and criteria with which to trigger selective <br />placement of material, as recommended by Mr. Nettleton in the second paragraph <br />of his section 4.0 "Conclusions and Recommendations". <br />With the imposition of this condition, I believe that the Southfield Mine has <br />succeeded in demonstrating that its coal mine refuse pile is sufficiently <br />stable to satisfy our regulatory requirements. <br />cc: Cathy Begej <br />Dan Hernandez <br />Doc. No: 1125E <br />JP/jP <br />