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West Elk Mine • flquifers Horizontal strain produced during subsidence could impact local aquifers in bedrock beneath the blanket of clay-rich surficial material. It also may impact local aquifers in surficial material, where permeable and saturated zones are stratigraphically positioned in zones of tensile strain. Impacts may occur for long periods of time, where the aquifer is located above mine boundaries and bamer pillazs, azeas where permanent strain occurs. On the other hand, dynamic strains and related cracks produced by subsidence above moving longwall faces in a given area are nil and close when the longwall faces move out of the area of influence of this area. Based on the author's evaluation, any mining effects on local on aquifers can best be identified by monitoring any changes in flow and water levels in springs and ground water. Ground Water Wells The two monitored, ground water wells in the South of Divide mining azea aze located east of, and near the mouth of Deer Creek. They are located above, or within the azeas of mining influence of, the barrier pillaz areas and haulageways of projected longwall panels E2 and E3. Overburden depth to the E seam is approximately 375 to 400 feet. The major source of the water in these is wells likely from colluvium and alluvium in the Deer Creek drainage. These wells, and any other water wells within the azea of mining influence will continue to be monitored (or begin to be monitored) for as many years prior to mining as possible, in order to • determine baseline information that would yield seasonal variations. Roads With the exception of the presence of minor subsidence cracks on an access road to Jumbo Mountain, no subsidence features (cracks or bulges) were observed during the annual subsidence observatons. Large, extensive cracks were observed on Jumbo Mountain in landslide areas; however, they were considered to be exclusively caused by the natural landslide process. Based on past observations in the Apache Rocks and Box Canyon mining azeas, no significant effects from mine subsidence aze expected on most of the access roads and drill road in the South of Divide azea. Also, no effects from landslide movements or rockfalls aze expected, because the highest rockfall potential is mapped in the high category. Rockfalls were observed to occur only in the very high rockfall category azeas in the Box Canyon mining azea. Although no cracks aze expected in the soft, pliable alluvium, some cracks aze expected to occur on the harder and more highly compacted Dry Fork access road, particularly in the area near the confluence of Deer Creek and Dry Fork. As discussed previously, the range of maximum vertical displacement, tilt, and horizontal strain is projected to be 8.4 to 11.2 feet, 1.3 to 6.4 percent, and 0.7 to 4.2 percent (respectively) in the North Fork stream valley and road above the solid coal boundazies at western limits of longwall panels E2 and E3. • 1.05-140 Revised November 2004 PRIO