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bench area was essentially a cliff or "natural highwall." If the <br />stability analysis of the complete highwall backfill scenario <br />results in a static factor of safety less than 1.3, the applicant <br />can then evaluate alternative backfilling schemes for the portal <br />bench area and access road cut to arrive at an optimal backfill <br />configuration that allows for backfilling of the exposed coal seam <br />with a minimum of 4 feet of non-toxic, non-combustible fill and <br />which provides for a prudent degree of stability for both the fill <br />and the remainder of the exposed highwall. The determination of the <br />most appropriate backfilling scheme should also incorporate as a <br />design feature a basic cut and fill balance to avoid importing fill <br />material from off-site locations. <br />2. <br />3. <br />ii. The applicant's proposal to install a diversion ditch at the crest <br />of the highwall fill needs to be evaluated in terms of overall slope <br />stability. Based on a preliminary review, it appears that this type <br />of drainage control structure could significantly decrease the <br />stability of the fill by increasing the amount of water percolating <br />through the highwall/backfill interface. The applicant may wish to <br />consider alternative means of controlling erosion on the regraded <br />fill such as flat or gently sloping terraces which reduce slope <br />length without concentrating runoff within an unlined ditch situated <br />at the crest of the fill. <br />iii. Once a backfilling and grading plan for the portal bench area has <br />been mutually agreed upon, the permit application text and <br />appropriate maps will need to be revised accordingly. Any <br />extraneous information or discussions regarding backfilling schemes <br />other than the approved plan should be removed from the text to <br />eliminate confusion. <br />Variance from Approximate Original Contour <br />type of backfill configuration works out to less than 1.3, then a request <br />fora variance is appropriate and Section 2.06 of the application should <br />be revised to describe the configuration and relative stability of the <br />alternative backfilling scheme mutually agreed upon by the applicant and <br />the Division. <br />The request for a variance from approximate original contour restoration <br />requirements contained in Section 2.06-2 of the application will need to <br />be revised to he consistent with the backfilling scheme mutually agreed <br />upon between the Division and the applicant. If the backfilling scheme <br />that involves complete backfilling of the exposed highwall achieves a <br />static factor of safety of 1.3 or greater, then a request fora variance <br />is no longer appropriate. If the calculated factor of safety for this <br />Bonding/Reclamation Cost Estimate <br />Based upon additional information submitted by the applicant, the <br />Division has revised the preliminary reclamation cost estimate for the La <br />Plata #1 Mine as follows (refer to attached revised worksheets): <br />