2010-12-17_REVISION - C1981019 (115)

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• Create gridded quality surfaces o Use FEM interpolator as "override interpolator spec" • Create suites of coal quality contours • o Review isopleths Quality Export Notes The Colowyo coal quality parameters modeled in StratModel consists of total moisture, equilibrium moisture (EQM), dry ash, dry sulfur, dry btu, ASG, and AFT. The incremental data samples are exported from the database. The EQM and AFT values are not analyzed with incremental samples. Therefore, EQM and AFT values are derived from the composite samples of the same hole, based on the centroid depth of the incremental sample. The incremental samples are exported and modeled in MineScape, in -lieu of composite samples, so that potential changes in mining seam height can be addressed within MineScape without having to re- export data from the database. MineScape Quality Composite Method MineScape contains a complete set of tools for determining composite quality values from incremental quality values. These tools use the StratModel table (drill hole model) to determine composite quality values by seam. • The basic process of determining quality composites in MineScape is: • The depths of the incremental coal quality data are converted to elevations based on the collar elevation of the drill hole. • Within each drill hole, the elevations of each incremental sample are compared to the elevations of each lithological seam. • A composite quality value is created by weight averaging those incremental samples that reside in whole or in part of a seam. o Weight averages are currently performed by length only. ASG or density can be used as an additional weighting factor. • The resulting output table contains columns of composite values by seam and quality parameter (e.g. D2—ash or E2_BTU). • Grid surfaces are then created from the composite values for each seam and quality parameter. These surfaces provide the basis for resource estimates. 11