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<br />need to be relocated through an appropriate revision application. <br />The light use road alinement is currently being used to facilitate <br />equipment traffic. I suspect that the constriction to movement is, <br />or will, create delays in project progress. I also suspect that <br />the affected slope cannot be rehabilitated. In any case, the <br />disturbed area will need to be stabilized and reclaimed. Because <br />the materials have been driven past peak strength to failure, it <br />probably will not be possible to simply regrade the failed slope to <br />AOC. Significant over excavation and stabilization will probably <br />be required. I doubt that movement on the failure plane will cease <br />within the next month. <br />The stream buffer and riparian area adjacent to the creek have <br />probably been irreversibly compromised. Temporarily, measures <br />should be taken to prevent downcutting of the compromised channel <br />and sediment generation. MCC's suggestion of a temporary flexible <br />PVC pipe to transport waters past the failed mass is probably an <br />acceptable temporary measure. We should specify a date for <br />submittal of a revision for operation accommodation and final <br />reclamation of the channel and riparian area. I assume the Corps <br />of Engineers also must be notified and appropriate permits applied <br />for by MCC. Finally, we should specify a date for completion of <br />any stream channel modifications prior to the end of this year's <br />construction season. <br />tation - Slope Failure <br />Tl~e~fibstation cut slope had been largely graded as of our visit. <br />A three to five foot high circular head scarp was obvious in the <br />excavation. It appeared that a surficial circular rotational <br />failure has developed in the weathered material mantling the cut. <br />The failed mass occupies approximately half of the excavated face. <br />I suspect that the failure will clean most of the weathered <br />colluvial veneer from the excavation exposing less weathered <br />bedrock. Subsequently the exposed bedrock will slake and <br />disaggregate, leading to progressive rotational failures. In this <br />manner the failed area will seasonally increase in volume, <br />resulting in debris moving downslope. The substation, constructed <br />at the toe of the cut, will be exposed to potential debris damage, <br />placing the power supply for the ventilation shaft fans at risk. <br />In addition, progressive evolution of the head scarp upslope will <br />soon undercut and compromise the light use goat trail road to the <br />powerline, located approximately 30 feet above the existing initial <br />rotational head scarp. <br />While at the site I discussed my concerns with Eric Mende and MCC's <br />geotechnical consultant. I expressed my concerns regarding the <br />light use road. I suggested that it would be appropriate to <br />attempt to constrain upslope migration of the failed mass through <br />tiebacks or piling above the existing head scarp. I also suggested <br />that revetments or debris walls might be helpful above the <br />substation. <br />As in the case of the access road failure discussed above I believe <br />