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subsidence control at the Bear No. 3 Mine. No structures overlie the underground <br />workings of the Bear No. 3 Mine. Potentially affected renewable resource lands are <br />limited to the aquifers of the Barren Member of the Mesaverde and the coal seams <br />overlying the B- and C-Seams extracted in the Bear No. 3 Mine and the springs <br />located in Lone Pine Gulch. The limited area of the potentially affected aquifers <br />which occur within the permit area, and the limitation of potential effects to the <br />down-dip, near-outcrop parts of these aquifers and coal seams, will reduce the <br />possible hydrologic effects of subsidence upon the aquifers and [he coal seams. Bear <br />did not mine within the angle of draw of the Lone Pine springs, and additionally used <br />50 percent coal extraction in areas adjacent to these springs. The Division does not <br />consider the Bear No. 3 Mine a threat to either structures or renewable resource <br />lands. <br />B: With the submittal of Permit Revision No. 2, the Division determined that Bear Coal <br />Company should submit a list of the various structures and renewable resources <br />within and adjacent to their permit area. Bear submitted the inventory and a <br />subsidence control plan (page 2.05-63d of the permit application) to restrict mining <br />and associated subsidence to areas that are well away from structures or renewable <br />resource lands absent additional subsidence monitoring. Upon further review, the <br />Division determined that additional subsidence monitoring would be required in areas <br />that were previously not considered as renewable resources and not identified as such <br />by the operator. These areas are the Mountain Coal ventilation fan access road, an <br />ephemeral surface tributary to Lone Pine Gulch, and the area overlying panels 31-38. <br />This additional monitoring was addressed through submittal of a technical revision <br />as required by Stipulation No. 35. <br />Bear Coal Company has backfilled the portals at the Bear No. 1 and 2 Mines. The <br />Division stipulated that the stability of these two backfilled areas be monitored for <br />a period of two years in the September 18, 1985 permit revision findings document. <br />This stipulation has been satisfied. <br />The canyon walls of the North Fork of the Gunnison River are covered with <br />numerous landslide deposits. These mass movement features vary in age from <br />ancient to modern. Rotational slumps, translational, earthflow and debris-flow <br />features are present on the site. A study conducted by Rocky Mountain Geotechnical <br />of the Bear No. 3 property has mapped numerous mass movement features. <br />The Division was concerned about reactivation of these features by subsidence of the <br />land surface resulting from coal extraction. An extensive study by Rocky Mountain <br />Geotechnical was completed in 1986 that addressed the relationship between <br />subsidence and the potential reactivation of slide bodies above the Bear No. 3 Mine. <br />The study concluded that the general mass movement mechanism was small, shallow <br />slope failures rather than large, deep failures. The report concluded that the <br />landslide features above the Bear No. 3 Mine were unstable and that failures would <br />occur regardless of subsidence effects. No subsidence effects were expected to occur <br />30 <br />