2010-09-01_INSPECTION - C1992080 (2)

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From the position of the feature on the slope relative to the former bench and erosion control, we concluded that the origin of the observed feature was compaction of the topsoil placed on the slope during reclamation. Immediately above the feature, the erosion logs had silted and overtopped two years ago, providing a water source to saturate the topsoil and allow compaction in the area noted. The lack of a continuous crack or evidence of movement, combined with the feature having vegetation along its length, refutes the inference that this is an instability feature. Also in Section III, Comments-Compliance, under the heading, Slides and Damage you state, "A zone of instability was observed at the western toe of the Rock Fill, adjacent to the paved roadway (Photo 3). Although the surface was dry at the time of the inspection, it appears that excess water may be moving out of the slope on a seasonal basis. The surface of the soil is disturbed, and the predominant vegetation at the location is field bindweed, in contrast to the established elsewhere on the Rock Fill. " There is no area of the Carbon Junction Mine designated as the "Rock Fill". From the description and photograph it was deduced that you were referring to the Previously Reclaimed Spoil Area (PRSA). Again, based on your photograph, the area described was inspected on July 31, 2010. No area of instability was observed. There was on evidence of potential slope failure, no tension cracking, no slope bulging, no displacement of vegetation, no seeps or springs. In short, there was no evidence of any potential or actual instability (Figures 2 and 3). For several reasons the likelihood of slope instability in the area you described is minuscule. The PRSA was created from shot durable rock sandstone with an engineered French drain to remove any moisture from the fill. The fill material above the durable rock sandstone is a homogenous mix of compacted porous colluvial overburden and aggregate, covered with topsoil. The potential for water retention in such an engineered fill is essentially nil. Certainly, the slope angle of the area you describe is insufficient to generate an unstable slide mass. The presence of field bindweed, an opportunistic early seral stage herbaceous perennial with any extremely broad ecologic niche is not indicative of any slope instability, or of any significant condition. In Section III, Comments-Compliance, under the heading, Excess Spoil and Development Waste you state, "Adjacent to the northeast side of the Rock Fill, there is an area (perhaps %a acres in size) which appears to pond water on a seasonal basis "(Photo 4). The ground was dry at the time of the inspection, but vegetation differences (foxtail and weeds) and remnant wildlife footprints provide clear indication that ponding does occur. There exists the possibility that water ponded here is contributing to the toe bulge described in the preceding section. Continued monitoring of the Rock Fill is warranted. " There is no area of the Carbon Junction Mine designated as the "Rock Fill". From the description and photograph it was deduced that you were referring to the Previously Reclaimed Spoil Area (PRSA). Again, based on your photograph, the area described was inspected on July 31, 2010. Carbon Junction Mine Page 2 CDRMS July 2, 2010 Inspection Rebuttal