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sediments. One only needs to inspect the cliffs along Routt County Road 27 near the Twentymile <br />Coal Company headquarters to see direct evidence of subsidence impacts on the rock formations <br />in the area. On the other hand, vast areas of subsided land in the immediate vicinity cannot readily <br />be recognized as having been subsided. So the effects on cultural resources from subsidence will <br />depend upon the nature of the resource itself and on the nature of the landscape where the site is <br />situated. Sites most sensitive to the effects of subsidence include rockshelter and rock art sites <br />located on or beneath rock outcrops. Standing structures are also sensitive to the effects of <br />subsidence. <br />Site types not sensitive to the effects of subsidence would include surface and shallowly <br />buried historic and prehistoric sites located in open terrain. Sites where the effects of subsidence <br />have not been adequately documented include buried and/or stratified archaeological sites, and sites <br />located in proximity to streams whose gradients and courses might be slightly altered by subsidence <br />and a resulting change in erosion patterns. Some very limited potential for impacts to archaeological <br />sites along Fish Creek, Grassy Creek, and intermittent tributaries can be anticipated as the channel <br />reverts to base gradient after subsidence. Changes in the floodplain hold little potential for <br />disturbance simply because those sediments are so recent. The areas of concern, however, are the <br />terraces and benches that parallel the floodplain which may be impacted by lateral channel migration <br />and increased erosion in situations where those surfaces see a relative increase in height above the <br />floodplain. <br />Cliff bands and unstable or steep slopes have potential to collapse or slump during or <br />following subsidence, as clearly demonstrated by the cliff fall above the current mine headquarters <br />where MAC excavated the Red Army Rockshelter, 5RT345, in 1993 and 1994 (Pool 1997). Such <br />disturbance would certainly have an impact on sites found in these areas, particularly rockshelter <br />sites and rock art sites. <br />Finally, standing historic (or prehistoric) structures also have potential to be impacted by any <br />differential settling associated with subsidence. In this particular project area, no prehistoric <br />structural remains are anticipated (given the terrain, and recent uses as open pasture and hayfields), <br />but there is potential for historic Euroamerican structures such as houses, barns and other buildings, <br />primarily associated with ranching. <br />FIELD AND LABORATORY METHODS <br />Given the above, and in order to address the potential effects of subsidence without <br />conducting an inventory of the entire mine permit area, MAC proposed a modified inventory <br />methodology designed to locate and record site types that are sensitive to the effects of subsidence, <br />as well as to inventory all settings where there is reasonable expectation that subsidence may have <br />an effect on the integrity of sites. The inventory strategy was to focus on landforms and topographic <br />features where there is potential for surface disturbance, slumping or collapse. It was also to focus <br />specifically on locating and recording standing historic structures. This strategy was discussed in <br />a Class I report separately submitted to, and reviewed by the Bureau of Land Management, Little <br />Snake Resource Area, and the Colorado Office of Archaeology and Historic Preservation (Metcalf <br />and McKibbin 2008). The methods proposed in that document were followed in this study. <br />14