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diversion ditches, areas considered suitable for ditch relo- <br />cations, etc. We assume Cyprus will also reconci~e the suL <br />old <br />ma <br />We assume that Cyprus will assist us in obtaining the samples <br />of the waste pile material by providing a backhoe for 1 day. <br />We also assume that Cyprus will monitor the ground water <br />levels in the monitoring well installed by Lambert & Assoc- <br />iates in the boring on the top of the west ridge waste pile. <br />PORTAL CUT SLOPE FAILURE EXISTING CONDITIONS <br />The failure at the north part of the west portal cut occurred <br />during March 1969. It developed in the upper cut portion, <br />above the intermediate bench generally separating bedrock <br />and overburden formations. However, at the location of the <br />failure, bedrock is apparently absent in the lower cut portion. <br />The failure appears to be limited by the intermediate bench <br />at the bottom. The crest of the failure is close to the <br />crest of the portal cut. A topsoil storage pile is located <br />on previously undisturbed ground immediately above the failure. <br />A surface diversion ditch that collects runoff from the topsoil <br />storage pile runs between the top of the failure and the toe <br />of the topsoil storage pile. <br />POSSIBLE SLOPE FAILURE MITIGATIONS <br />The existing failure needs to be mitigated during 1989 to <br />prevent its enlargement in future years and to prevent the <br />potential loss of portions of the topsoil storage area and/ <br />or the diversion ditch. We consider that several mitigating <br />measures are feasible: <br />1. Excavation of some or all of the failure mass and flat- <br />tening the slopes above it. This solution would probably <br />require permanent relocation of the diversion ditch and <br />partial relocation of the topsoil storage pile. <br />2. Rebuilding of the failure area to approximately prefailure <br />conditions. This would probably require some reinforce- <br />ment of the slope by geotextiles, constructing of a <br />buttress at the toe of the failure, etc. <br />We also understand that MLRD is willing to accept mitigating <br />measures that do not provide factors of safety required for <br />permanent slopes, and that some risk of future stability <br />problems in the area can be accepted. <br />DEN/40Y/020 4 <br />