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(• 3.2.1 Mining Methods <br />STORM KING proposes to extract coal at the Coal Ridge No. 1 <br />Mine with a full-extraction hydraulic mining system. The proposed <br />mining technology and mining layout are described in Sections 4.1 <br />and 4.2 of the permit application. <br />The proposed mining area will be divided into extraction <br />panels. These panels will be subdivided into sublevels from which <br />the actual hydraulic mining will take place. As a sublevel is <br />extracted, the roof will be allowed to cave. <br />Coal in each panel will be extracted sequentially from each <br />sublevel, starting with the uppermost sublevel in each panel. It <br />is anticipated that extraction in each individual panel will <br />approach 85~. Average extraction for a multiple panel area will <br />approach 63%. <br />3.2.2 Site Parameters Affecting Subsidence <br />~• The magnitudes of surface subsidence effects are controlled <br />by parameters characteristic of the specific mine site and the <br />mine plan. The critical parameters affecting subsidence effects <br />are: <br />1. Overburden depth <br />2. Surface topography <br />3. Overburden stratigraphy <br />4. Overburden structural geology <br />5. Mine layout <br />This section briefly summarizes these site parameters for the <br />proposed permit area at the Coal Ridge No. 1 Mine site. <br />3.2.2.1 Overburden Depth <br />Overburden depths in the proposed permit area vary from zero <br />at the outcrop to a maximum of about 6000 ft at the southwest <br />corner of the proposed permit area. <br />Overburden depths in the proposed 5-year mining area vary <br />. from about 100 ft to 140 ft at the base of the crown pillar to a <br />maximum of about 1400 ft near the western end of the 5-year mining <br />page 14 <br />