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~J <br />• <br />Contained within this report are evaluations of the chemical and physical data, locations and <br />extends of suitable and unsuitable overburden, and proposed methods of mitigation. Spoil mixing <br />phenomenon is discussed and core variability is documented. A sampling program immediately <br />after mining is proposed to investigate and evaluate mining methods, overburden mixing, and <br />reclamation success (see Section 2.05.4(2)(d), Topsoil (Redistribution). These investigations and <br />proposals are intended to optimize postmine vegetation growth and ground water aquifer <br />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 New Horizon 2 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 a1. (1981), <br />Dollhopf (1983), Montana Department of State Lands (1983), and Wyoming Department of <br />Environmental Quality (1985). Phased drilling programs can decrease overburden, interburden, <br />and underburden (OIU) characterization costs substantiallywithoutjeopardizing the quality of data <br />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 characteristics <br />over the entire study area and to obtain representative core hole locations from <br />which cross sections could be developed. Following the initial data analysis and <br />interpretation, general areas and percentages of suitable and unsuitable material <br />were identified. The site specific horizontal and vertical variability and <br />discontinuities of strata were evaluated. <br />Phase II: Three additional sampling locations were approved for the New Horizon 2 study <br />area on August 7, 1987 by CDMG (Peter O'Connor's letter to J. Lunan). Phase II <br />• REVISED August 2006 2.04.6-13 <br />