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GENERAL53416
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Last modified
8/24/2016 8:38:58 PM
Creation date
11/23/2007 8:35:57 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
General Documents
Doc Date
8/25/1997
Doc Name
GEOTECHNICAL REPORT SYLVESTER GULCH SITE DEVEOLPMENT 8/12/97 - 8/17/97
From
MOUNTAIN COAL CO
To
MLR
Permit Index Doc Type
EXPLORATION
Media Type
D
Archive
No
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<br />Reporting Period August 12, 1997 -August 17, 1997 <br />3 <br />8' BGS at I-11, which contained a 6" thick soft, saturated clay layer that seemed to <br />correspond to the level at which movement was detected in the inclinometer. The Shelby tube <br />sample from 9.5'-11' BGS at I-12 contained roots, indicating the slip plane is in native material <br />rather than the fill material as first thought. Golder and Barr have been retained to prepare <br />independent evaluations of the stability of this area, and will provide recommendations to <br />MCC on whether this area is buildable, and to what degree. <br />Main Embankment (F-Walls): Approximately 14' of fill was placed in the last week. Pore <br />pressure data is being collected daily from the three strain gage piezometers and no rise in <br />pore pressure has been observed in any of the piezometers. In the center piezometer (VW-2), <br />the water level has dropped below probe elevation. Inclinometers I-10 at the south toe of the <br />embankment was installed on August 17. Inclinometer I-9 at the north toe of the embankment <br />(installed August 12) shows no movement. <br />Landing #2 Road: The light-use road to Landing #2 was inspected on August 15. Soil cut <br />and fill slopes appeared stable throughout the length of the road. <br />Dewaterina Borehole Road: The sight lines and slope conditions remain as previously <br />reported. Minor seepage associated with sandstone strata along this road continues. MCC <br />will be submitting a minor revision to convert this road to a 24' wide haul road, and has <br />incorporated French drains at the top and bottom of the new cut slope into the design. <br />Substation: Visual observation of the slope above the substation on August 15 indicated the <br />former scarp lines are reappearing in their previous location, however, no advancement of the <br />head scarp further upslope and into the Landing #2 road was observed. Survey stakes were <br />placed across the head scarp and when observed on August 17, approximately 3/8" of <br />movement was measured. Survey data taken on August 15 also indicates approximately 0.85' <br />of movement at station SL-3 (just below the head scarp) in the past week, and approximately <br />0.15' of movement at station SL-5 (toe of slope above substation highwall). <br />This movement is consistent with a sensitivity analysis of the as-built slope completed by <br />Golder Associates this past week. Golders' analysis shows that construction of the diversion <br />ditch (approximately midslope) destabilizes the slope using any assumed friction angle. The <br />analysis also shows that filling this ditch with rock and gravel re-establishes a stable slope, <br />again using any assumed friction angle. MCC intends to implement this solution as soon as <br />possible, and will continue to monitor the slope to determine if additional actions are <br />necessary. <br />Shaft Site #1 and #2: The shallow slope failure on the steep cut slope south of Shaft #1 that <br />was repaired last week with a compacted soil buttress was observed on August 15 and August <br />17, and no new movement was visually detected. Slopes to either side of the buttressed area <br />were also observed and appeared stable. Data from the survey prisms placed above this slope <br />confirm no movement is occurring. Additional hubs were placed in the finished slopes this <br />
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