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_. <br />Memo to Grassy Gap File - 2 - August 24, 1989_. <br />I do not oelieve the likelihood of Rock castle Company significantly regrading <br />the site to better meet AOC to be high. And at this Doint, with several years <br />of stable performance benind us, I do not consider significant regrading to be <br />desiraole either. The one long-term stability concern which John and I <br />perceive is surface Drainage through the site. Currently water is collected <br />in the large flat area and controlled and channeled through the use of <br />discontinuous contour furrows and a perimeter ditch. This system releases <br />almost all runoff from the site adjacent to the pit access road. Significant <br />erosion has resulted in the perimeter ditch along the road, and at the point <br />wnere water is released from the ditch and flows down an oversteepened slope <br />to intersect the road ditcnes. Continual effort is exerted to stabilize <br />erosion in these areas. Yet erosion continues to reoccur. <br />Therefore the one long-term stability concern which I nave is surface water <br />Drainage. The contour furrows and the perimeter ditch are not permanent <br />structures Dut rather temporary measures to enhance revegetation and control <br />erosion. It is apparent that revegetation and erosion control efforts have <br />peen successful. Rock castle needs to address the long-term drainage <br />characteristics of the site, without the control exerted by contour furrows <br />and the perimeter co llection ditches. A drainage channel snould be <br />constructed to handle drainage off the area - ultimately channeling it to the <br />natural drainage to the north of the pit area. Given the current topography, <br />two drainage channels may be required. <br />After this issue has been successfully addressed on the ground, tnen we could <br />contemplate accepting the current topography as acceptable. <br />Tnese conclusions are based on extensive inspection of the site and study of <br />premining topographic maps and reclamation maps contained in the permit <br />application, as well as topographic and perspective maps generated in-house <br />using our survey data. <br />In summary, I believe the Dit 6 reclaimed topography meets AOC and is <br />acceptaole. Pit 5 reclaimed topography could be acceptaole with the <br />implementation of an approved permanent drainage design. This drainage design <br />would presumably entail some regrading and the construction of at least one <br />small stream channel. <br />9193=/scg <br />