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jeopardize the vehicle occupants safety. Although the lack of durable <br />surfacing material will cause increased erosion to the road surface and off- <br />road sediment, all drainage from the road except for two sections (Segments 3 <br />and 9) is directed to a sedimentation pond prior to leaving the permit area. <br />Alternate sediment control measures are provided for Segments 3 and 9 as <br />described in this appendix. <br />Three drainage runout points are provided along the Goat Trail. The <br />runouts occur at the end of Segments 3, 8, and 9. Over the previous 40+ years <br />that the road has been in existence gullies have formed below all of these <br />runouts. It is P6M's belief that the gullies have remained relatively stable <br />over the past 15 years. However, to help minimize any additional erosion of <br />the gully features, loose rock filters will be maintained in the runout <br />channels of the drainage system along the roadway to reduce the runoff <br />velocity and help ensure the continued stability of the gullies. The runout <br />channel descriptions provided in this appendix represent minimum design <br />criteria. The channels may be built larger than designed to accommodate <br />construction of effective loose rock filters. Rock materials for the loose <br />rock filters will have a D5p of 6 inches. The gradation of the rock materials <br />will be sufficient to enable the voids between the larger particles to be <br />filled with smaller particles minimizing flow beneath the riprap and the <br />formation of open pockets. Figure 3.SF-1 shows a typical runout channel and <br />the loose rock filter configuration and placement. <br />It has been mutually agreed by the CDMG and P&M that any attempt to <br />remediate the gullies themselves would result in more detrimental <br />environmental impacts than could be solved due to the steepness of the slopes <br />and removal of existing vegetation. As such, PAM will monitor the gullies to <br />determine if the loose rock filters placed in the drainage runouts are <br />sufficient to maintain the stability of the gullies. This monitoring effort <br />will be incorporated in the Rill and Gully monitoring program already <br />initiated by the Company with the results being reported to the regulatory <br />authority on an annual basis. Should the remedial measures in the drainage <br />runouts fail to keep the gullies in a stable condition, additional remedial <br />will be implemented along the drainage runouts to stabilize the gullies. <br />It is recognized that the gullies were primarily formed prior to the <br />passage of SMCRA, and are considered pre-existing conditions. PAM further <br />• <br />3.SF-2 May 14, 1993 <br />