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~*, .'~ Reporting Period October 08, 1997 -October 19, 1997 Field Observations, Data Collection, and Ongoing Evaluations 2 A complete inspection was performed by MCC on 10/17/97 to visually observe and evaluate the stability of slopes within the project area. Data collection efforts and evaluation or re-evaluation of specific areas of concern continues. Individual areas are discussed in detail in the following sections. Supporting documentation is attached for your review. Lower Svlvester Gulch Road: Excavation of cut slopes and benches along the alignment of the lower Sylvester Gulch road are approximately 95 % complete. Culvert and culvert inlet excavation are in progress. The top-of--slope french drains described in previous reports appear to working effectively in that water is being captured at all locations where installed, and slopes below the drains are remaining stable. MSE Wall E (station 50+50 to 54) has been modified with the placement of a rock buttress at the toe of the wall to provide greater stability and additional erosion protection, due to the walls' close proximity [o [he Sylvester Gulch stream channel. The latest readings on inclinometer I-2 (10/9 and 10/16) show incremental movement at the surface is not continuing, lending credence to the conclusion that the previously monitored surface movement was attributable to construction equipment. At 24' to 32' depth, incremental movement continues but with decreasing velocity. Inclinometer 1-2 will continue to be maintained and monitored during conswction and for the long term. A new inclinometer, 1-4B, to replace inclinometer I-4 destroyed during construction, will be completed 10/21/97. The location of this inclinometer is above the top of the cut slope, within the same previously mapped slide as 1-4, but approximately 100 feet further north. Uooer Svlvester Gulch Road: Stability analyses and other evaluations of the failed fill area by Golder Associates and Barr Engineering were received. Both Golder and Barr believe the failure was caused by compacted clay material blocking natural subsurface drainage, which in tutu lubricated a deep failure plane. MCC will evaluate recommended stabilization methods, however, as mentioned previously, it is unlikely any fix will be attempted this construction season. New inclinometer 1-13, installed at the top of the ridge above the failed area shows no movement at depth. Main Embankment (F-Walls): Weekly measurements at I-9 and 1-10 taken on 10/9 and 10/IS show continued decreases in incremental and cumulative movement. Pore pressures also continue to decrease. MCC will continue to monitor the inclinometers and piezometers. Landine#2 Road: The light-use road to Landing #2 was inspected on 10/17. Soil cut and fill slopes appeared stable throughout the length of the road. Drainage ditches appear to be working properly. Dewatering Borehole Road: The french drain above the top of the redesigned cut slope was completed and excavation of the cut slope is in progress. Survey monuments installed above the cut slope and french drain show a minor northward creep. Monitoring will continue. Substation Slooe: Visual observations and survey data for the slope above the substation indicates movement is continuing at a slow and gradual pace, with incremental movements decreasing over time. No advancement of the head scarp further upslope and into the Landing #2 road was observed.