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NUCLA EAST OVERBURDEN ASSESSMENT <br /> Chemical analyses of overburden samples obtained from the Nucla East study area were <br /> performed by Peabody Coal Company to identify any acid-forming, toxic-forming, alkalinity <br /> producing, or other inhibitory materials present within the proposed mine boundary. <br /> Physical properties of the overburden were determined to define compaction, stability, <br /> permeability, erodibility, and water holding characteristics. Chemical and physical <br /> analyses also reveal the most desirable overburden strata to be placed at the spoil <br /> surface and in the pit base. This baseline information is required prior to mining to <br /> effectively prepare a mine plan that restores landscape productivity and which also <br /> minimizes environmental degradation. <br /> Contained within this report are evaluations of the chemical and physical data, locations <br /> and extents of suitable and unsuitable overburden, and proposed methods of mitigation. <br /> Spoil mixing phenomenon is discussed and core variability is documented. A sampling <br /> program immediately after mining is proposed to investigate and evaluate mining methods, <br /> overburden mixing, and reclamation success (see Tab 21, Minesoil Reconstruction). These <br /> investigations and proposals are intended to optimize postmine vegetation growth and <br /> ground water aquifer characteristics. <br /> Conclusions and recommendations are based on the interpretation of laboratory data and <br /> lithological descriptions developed during the sample collection and analysis. <br /> Overburden Sampling Schedule <br /> A two phase overburden sampling program was utilized within the proposed Nucla East permit <br /> area to prepare the overburden assessment. Similar phased sampling techniques have been <br /> described by USDA (1979), Barrett et al . (1980), Dollhopf et al . (1981), Barth et al . <br /> (1981), Dollhopf (1983), Montana Department of State Lands (1983), and Wyoming Department <br /> of Environmental Quality (1985). Phased drilling programs can decrease overburden, <br /> interburden, and underburden (OIU) characterization costs substantially without <br /> jeopardizing the quality of data obtained. <br /> The following tasks were accomplished during the two phases of OIU analyses: <br /> Phase I : The first phase drilling was implemented in 1986 to determine OIU <br /> 6-1-11 Revised 04/11/88 <br />