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development and retreat mining operations will be submitted to and <br />approved by the Mine Safety and Health Administration (MSHA). <br />Development of the coal reserve, starting from the portal decline site, <br />will proceed by mining a set of main entries to the west and concurrent <br />mining of submain entries towards the mineable limits of the seam. <br />Main and submain entries will provide long-term access to all areas of <br />the mine, and will be designed and maintained for their purpose. A <br />typical plan for the design of mains and submains is illustrated by <br />Figure 2.05.3-1, Main and Submain Entry Development. The multiple <br />entry systems depicted on the plan show the function of individual <br />entries for intake and return airways, and an entry for coal haulage by <br />conveyor systems. The described development mining leaves support <br />pillars in place designed to effectively support the mine openings <br />according too depth of cover and strength of the coal and the immediate <br />roof and floor strata. The actual number of entries will vary depending <br />primarily on the area required to provide sufficient airflow for mine_ <br />operations. <br />Mining panels will be developed off the submains, consisting of a set of <br />five or six entries, to either the limit of mineable coal or the boundary <br />of adjacent sub-main entries. Panels will access the majority of coal <br />• reserves, aind will serve to extract the reserves by retreat mining <br />methods. Tlhe panels will be designed to provide for relatively short- <br />term acces:> into the mining area and to optimize the recovery of coal <br />within the boundaries of the panel. Typical plans for development and <br />pillaring of a panel are shown on Figure 2.05.3-2, Panel Development <br />and Retreat: Mining. Once a given panel is developed to its designed <br />limit, additional rows of pillars (rooms) are developed to the side of the <br />panel to access adjacent reserves from the developed panel. <br />Generally, c-nly two or three rooms are developed at one time ahead of <br />a similar number of rows of pillars that are retreat mined. Northfield <br />will conduct retreat mining by systematically mining as much coal as <br />safely possilble from the pillars, thereby recovering approximately 40 <br />to 50 percent of the coal remaining in support pillars while pillaring the <br />mine panel. Pillaring will continue through the length of the panel and <br />stop at a designed location near the entrance to the panel. At this <br />point, .the pillars at the mouth of the panel and adjacent barrier pillars <br />will be left u~nmined in order to protect the adjacent main or submain <br />entries from the increased ground pressure created by the removal of <br />the panel pillars. Long narrow pillars and relatively large blocks of coal <br />called barrier pillars will be left unmined in areas such as between <br />panels, betv~reen panels and submains, and in areas where subsidence <br />control is required. The proposed development and retreat mining <br />methods will <br />2.05.3-3 Revised 5/01/07 <br />