Laserfiche WebLink
<br />III. COMMENTS -COMPLIANCE <br /> <br />Below are comments on the inspection. The comments include discussion of observations made <br />during the inspection. Comments also describe any enforcement actions taken during the <br />inspection and the facts or evidence supporting the enforcement action. <br />SGFA Electric Substation -Slope Failure <br />The substation cut slope had been largely graded as of our visit. A three to five foot high <br />circular head scarp was obvious in the excavation. It appeared that a surficial circular rotational <br />failure has developed in the weathered material of the cut slope. The failed mass occupies <br />approximately half of the excavated face. I suspect that the failure will clean most of the <br />weathered colluvial veneer from the excavation, exposing less weathered bedrock. Subsequently <br />the exposed bedrock will slake and disaggregate, leading to progressive rotational failures. In <br />this manner the failed area will seasonally increase in volume and size, resulting in debris moving <br />downslope. The substation to be constructed at the toe of the cut, will be exposed to potential <br />debris damage, placing the power supply for the ventilation shaft fans at risk. In addition, <br />progressive evolution of the head scarp upslope will soon undercut and compromise the light use <br />goat trail road to the powerline, located approximately 30 feet above the existing initial rotational <br />head scarp. <br />While at the site I discussed my concems with Eric Mende and MCC's geotechnica] consultant. <br />I expressed my concerns regarding the light use road. I suggested that it would be appropriate <br />to attempt to constrain upslope migration of the failed mass through tiebacks or piling above the <br />existing head scarp. I also suggested that revetments or debris walls might be helpful above the <br />substation. <br />As in the case of the access road failure discussed earlier in this report, I believe MCC must <br />analyze the failure in order to develop an acceptable methodology for rehabilitation and <br />stabilization of the substation cutslope. Back calculation of the exact failed configuration should <br />provide more accurate material strength parameters for use in the development of remedial <br />treatments and final reclaimed treatments for the effected cutslope. <br />Roads <br />From the base of the slide azea, Mr. Boulay and Ms. Johnston continued walking to the south <br />along a light use road "jeep trail" that is located below and to the east of the main hauUaccess <br />road. At approximately 30 to 40 yards south of the southernmost limit of the slide, the jeep trail <br />parallels and is located immediately adjacent to the stream in Sylvester Gulch. At this location, <br />Mr. Boulay noted that the road berms built on the east side of the road were constructed <br />immediately adjacent to the stream in Sylvester Gulch. The silt fence (constructed to control <br />erosion and prevent additional contributions of sediment to streamflow) was broken in at least <br />four locations. Due to the weight of the berm construction material, the silt fence was laid down <br />into the stream channel at several locations east of the light use road. Berm construction <br />3 <br />