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-40- <br />SHALL UTILIZE STANDARD AERIAL OR FIELD SURVEY TECHNIQUES IN COMPLETING THE <br />REQUIRED SURVEY. THE SURVEY MAP AND A REPORT ANALYZING CONFORMANCE WITH THE <br />AMENDED POST-MINING TOPOGRAPHY SHALL BE SUBMITTED ANNUALLY TO THE DIVISION. <br />The Division has reviewed the geochemical overburden testing results, in order <br />to determine whether it would be appropriate to require any special handling <br />of toxic or acid-forming materials. It is the opinion of the Division that <br />there are no special handling requirements necessary for the placement of <br />backfilled spoil. <br />As a portion of the Deep Creek Permit Revision application, Chimney Rock Coal <br />Company proposes to construct a 181,250 cubic yard excess spoil fill, located <br />to the south of Pit 1R 2. In conjunction with the earlier swell factor <br />projections above, this material has been projected to be excess spoil with <br />which the Division concurs. <br />The applicant has submitted a report of a geotechnical investigation and <br />mathematical stability analysis for the proposed excess spoil pile, prepared <br />by CTL/Thompson, Inc., geotechnical consultant. The report represents the <br />results of drilling and materials testing performed on samples collected at <br />the site. Angering encountered 16 to 25 feet of colluvium underlain by <br />bedrock. Ground water was observed in one of the four auger boring at a depth <br />of 39 feet below ground surface. Appropriate materials testing was performed <br />on samples collected during the geotechnical investigation. The material's <br />shear strength values derived in that laboratory testing were used to complete <br />a modified Bishop's technique mathematical stability analysis of the proposed <br />excess spoil pile. <br />The stability analysis performed determined that the pile could comply with <br />the regulatory requirements with a static slope safety factor in excess of <br />1.5, if the following construction standards are adhered to. <br />1. Excess spoil shall be placed in lifts not to exceed 6 feet in <br />thickness and compacted by routing of loaded haul trucks over the <br />fill. <br />2. Well-cemented sandstone shall be segregated from the spoil and used <br />to construct subsurface drain blankets in three pre-existing <br />drainage swales, depicted on Figure 3 of the report. <br />3. Sheet flow shall be prevented from occurring on the surface of the <br />final reclaimed spoil through use of "deep furrows with direct <br />surface drainage downslope diversion ditches". <br />The report is vague regarding the design of the subdrains, as well as the <br />designs of deep furrows and drainage ditches to be implemented. For this <br />reason the Division believes it is appropriate to impose the following <br />stipulation upon permit approval. <br />