Laserfiche WebLink
SHANNON F~WILSON, INC. <br /> <br />In general, surficial soils consist of a relatively thin layer of colluviaUresidual soils on steeper <br />slopes, and thicker colluviaUalluvial soils in valley bottoms. The colluviaUalluvial soils consist <br />of gravel to boulder-sized bedrock fragments within a clayey or sandy matrix. The deposits can <br />be stratified with clay seams in areas along valley floors. <br />Specifically, based on borings ST-1 and ST-2, the surficial soils encountered during drilling <br />consisted of a medium stiff to hard, sandy to gravelly clay interbedded with very dense, clayey, <br />sandy gravel. The borings indicated that the depth to bedrock is approximately 24 feet in the <br />valley bottom. The bedrock consisted primarily of low strength sandstone and claystone. A coal <br />seam was encountered near the bottom of boring ST-1. <br />In boring ST-1, groundwater was measured at a depth of approximately 20 feet below the <br />existing ground surface during drilling. Groundwater was not encountered during drilling in <br />boring ST-2. It should be noted that groundwater conditions during drilling are not a static <br />measurement, but rather reflect short-term conditions. Further, groundwater fluctuations may <br />occur depending on the time of the year and local conditions particular to the site. The locations <br />of mapped seeps and springs are shown on Figure 5 (Reference 20). <br />Aerial photo analysis indicates several minor features within the footprint of the proposed excess <br />spoil fills that maybe landslide features. Figure 4 shows the locations and extents of these <br />features. The features include potential slump blocks and small debris flow scars less than 500 <br />feet long. In the east fill location, apparent downhill facing scarps on the east side of the valley <br />may be subsidence features due to burning of coal seams. Previously mapped scarps and <br />potential slides were also identified within the footprint of the west fill. Based on the location of <br />these features relative to the planned excess spoil fill locations, it appears that the features will be <br />buried by the fill, such that the fill will act as a buttress, and the features will not be near the toe <br />of the out-slopes. Therefore, it is our opinion that these possible landslide features will not affect <br />the stability of the excess spoil fills. <br />We do not know of any previous underground mining beneath the site that would affect the <br />stability of the excess spoil fills. <br /> <br />23-1-01105-200-Ri.doc 23-1-01105-200 <br />