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West Elk Mine . 3. Interconnected fractures in the fractured zone may form in the Marine Sandstone that underlies the D Seam and impact isolated groundwater that may be present. Any water present in these lenticular sand units of the Marine Sandstone might therefore be diverted to the mine workings. Though unlikely, fractures filled with water and methane that were reported in the abandoned Oliver No. 2 Mine (Dunrud 1976, p. 30-34) might be encountered or intersected by the B Seam fractured zone that may divert the water and methane to the B Seam workings. South of Divide Mining Area -Predicted subsidence impacts for the South of Divide mining area has been described in detail above. The greatest surface impacts are expected to occur along the precipitous slopes and cliffs that flank Minnesota Creek, Lick Creek, and other tributazies. Though unlikely, the worst possible consequences foreseen aze that cracks could locally form and be as much as 25 to 50 feet deep above chain pillazs and barrier pillars in bedrock on the precipitous slopes, ridges, and/or cliffs that flank Minnesota Creek, Lick Creek, and other tributaries, and may locally accelerate the naturally-occurring rockfall and landslide process. Some cracks are expected occur on the Dry Fork access road, however, in the area near the confluence of Deer Creek and Dry Fork. Maximum vertical displacement ranging from 8.4 to 11.2 feet, tilt from 1.3 to 6 percent, and horizontal strain from 0.7 to 4.2 percent aze projected in the Dry Fork valley above the western limits of longwall panels E2 and E3. • Based on subsidence observations by Mr. Dunrud (as discussed in Maximum Depth of Surface Cracks), no cracks aze expected to occur in either alluvium in the Dry Fork and Lick Creek drainages or stock watering ponds and drainage diversion ditches. In addition, no cracks are predicted to occur in colluvium more than about ten feet thick. Mr. Dunrud has estimated the alluvial cover in Dry Fork and Lick Creek to be approximately 25 to 75 feet thick (Section 11.3, Exhibit 60 B). The monitoring suggested above will compare results expected by the author, and actual Feld results. Potential Impacts from Local Seismic Activity Earth tremors have been recorded or felt by local residents in the Somerset azea since the early 1960s. The tremors commonly aze the result of coal mine bumps and rock bursts, which are spontaneous releases of strain energy in highly stressed coal and rock. In the Somerset Mine area before closure, the bumps and rock bursts were common in room-and-pillaz mining azeas where stresses concentrated within isolated pillars and blocks of coal (called bump blocks). Earth tremors have continued sporadically in the Somerset Mine azea since the mine was closed. Tremors generated by bumps and rock bursts in the Somerset Mine azea attain magnitudes that have shaken structures in the West Elk Mine azea and have been felt sometimes by West Elk Mine personnel. These local tremors may affect underground workings, landslide or potential rockfall azeas, particulazly during prolonged periods of increased precipitation. It is noteworthy, however, that the Rulison nucleaz shot in 1969, which produced a tremor with a Richter magnitude of 5.2, was many times greater than the magnitudes of any recorded coal bump. To Mr. Dunrud's knowledge, the Rulison nucleaz shot did not trigger any known landslides, rockfalls, did not affect the Somerset Mine, neither did it impact reservoirs, ponds, nor streams in the South of Divide 1.05-138 Revisedhme 1005 PRIO, Rev. March 1006; May 1006 PRIO