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• The mining limit envelopes have been developed from the draw angles <br />selected from National Coal Board (NCB) data and presented 1n Section <br />4.6.1.5.2. These limit envelopes are shoMn on Maps A and B for No. 1 <br />Mine and No. 3 Mine, respectively. <br />Past research indicates that the draw angles used to construct the min- <br />ing limit envelopes are conservative values. Thick sandstone beds simi- <br />lar to those in the overburden at the North Thompson Creek Mines tend to <br />cause actual draw angles 1n the mining area to be less than those pre- <br />dicted from NCB data (King, 1980; Abel and Lee, 1980; and, Kapp. 1974). <br />Data from the DOE subsidence monitoring net will be collected during <br />mining of the first three longwall panels at No. 1 Nine. This data will <br />• be constantly reviewed during mining to insure that the actual, measured <br />values for the draw angles and maximum subsidence do not exceed the de- <br />sign values used to construct the mining limit envelopes. A site speci- <br />ftc subsidence model Mill also be developed. <br />The data and the site specific subsidence model will be used to evaluate <br />the existing mine plan to maximize resource recovery. All proposed re- <br />visions to the mine plan will be submitted to MLRB staff for their re- <br />view and approval. <br />Snowmass Coal Company believes that the proposed subsidence control plan <br />allows for the orderly development of the mine property over the short <br />• term Mh11e maximizing resource recovery over the life of the property <br />25 <br />