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Basically, overburden and interburden needs to be characterized accurately enough for the <br />applicant and the Division to make valid determinations of any potential impacts of <br />regraded spoil on water quality and revegetation efforts. Some of the geology in the area <br />of interest will presumably be very similar to the geology at the Colowyo Mine. Data <br />accumulated from the Colowyo operation could be factored in to this assessment, most <br />appropriately following an initial round of overburden assessment in conjunction with early <br />exploration work. However, prior to identifying similarities or differences in local geology, <br />and prior to assessing the likelihood of spoil spring development in the new area of interest, <br />I would suggest general adherence to recommended procedures in the Montana guidelines. <br />In short, my recommendation is to collect core or rotary chip samples from representative <br />holes with a spacing of approximately one hole per 80 acres. Composite samples <br />representative of each strata down to the stratum below the lowest coal seam of interest <br />should be collected in 2-10 foot intervals, as discussed in the enclosed guideline. Following <br />this initial characterization, the need for more or less data in given areas or strata could be <br />evaluated in conjunction with analogous overburden and regarded spoil data from the <br />Colowyo Mine. That point in the overburden assessment program would appear to be the <br />appropriate time to assess the possibility of collecting any additional data during mining <br />operations, and/or from only the upper strata if they will be handled by truck and shovel. <br />I would recommend analysis of the following parameters during overburden analysis: <br />Textural class Saturation percentage Conductivity <br />pH Acid-base potential SAR <br />Boron Selenium Molybdenum <br />Nitrate Calcium Magnesium <br />Sodium <br />Lab procedures for these analyses, and unsuitability criteria listed in the Montana guideline, <br />which the Division generally refers to, are also enclosed for your reference. <br />I apologize for not getting this information to you sooner. If you have any questions, or <br />need more information, feel free to contact me. <br />Sincerely, <br />~i~~ <br />F~+7/ <br />Larry P. Routten <br />Environmental Protection Specialist <br />enclosure c:\wp51\071295 <br />