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a . <br />Reporting Period July 28, 1997 -August 3, 1997 <br />3 <br />Substation: Visual observation of the failed slope above the substation on July 31 and <br />August 3 showed no obvious additional movement in the slumped area and no advancement <br />of the head scarp into the Landing #2 road, even with very soggy slope conditions. <br />Realignment of the Landing #2 road further into the hill, and construction of a bench <br />approximately mid-slope has resulted in an overall slope configuration that approximates pre- <br />existing slopes and appears to be stable. <br />Shaft Site #1 and #2: A shallow slope failure on the steep cut slope south of Shaft #I was <br />observed and reported by construction personnel Wednesday morning. When inspected on <br />Thursday afternoon, the slide zone measured approximately 50 feet wide (base width) by 35 <br />feet high, with a head scarp of 3 feet at the top of the cut. Slope failure was observed to be a <br />series of soil wedges which are toppling outward, with the base of the failure area at the level <br />of an exposed claystone and sandstone outcrop. When inspected Sunday, the head scarp had <br />progressed another 5-10 feet upslope, but the lateral extent of the triangular wedge, and basal <br />movement of the slide had not changed. The undisturbed ground above the entire cut slope <br />was thoroughly inspected, and no cracking or movement was observed in areas inside or <br />outside the slide zone, except for directly above the head scarp. Directly upslope of the apex <br />of the head scarp, additional soil cracks have appeared approximately 15 feet further upslope. <br />MCC halted construction in this area on Wednesday, and per MCC's slope stability action <br />plan, is evaluating stabilization methods for this area. <br />Data Collection and Evaluation <br />Additional monitoring of inclinometer I-12 at the failed fill area continues to indicate a slip plane <br />at approximately 6 feet below surface, which places the slip plane within the fill rather than in <br />native ground. However, total movement is small enough that the data is still considered <br />inconclusive. A summary of cumulative displacement data for I-12 is attached. Monitoring and <br />evaluation will continue. Surface surveys continue to indicate no measurable (> 0.1') movement <br />either above the cut slope or below the fill area. Test pits below the toe on either side of <br />Sylvester Gulch are scheduled for the week of August 11. <br />Draft cumulative displacement charts for inclinometers I-4 (approximately Station 30+00) and I-2 <br />(approximately Station 15+00) were received, and are attached. Velocities at I-4 are approaching <br />zero and monitoring of I-4 will be discontinued after the next reading. Re-evaluation of the <br />current design slope at this location is in progress. Data at I-2 shows very little movement to date <br />and is inconclusive. Monitoring and evaluation of I-2 will continue. <br />A new survey line for the substation cut slope was established to allow continued monitoring of <br />this slope, and to facilitate back calculated stability evaluations. Per MCC's slope stability action <br />plan, MCC is continuing to look at long term feasible stabilization techniques, however, in the <br />short term, no stabilization activities appear necessary. <br />