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)N~y .f with minimal damage and risk to i motorists. A mitigation plan was devel- oped that addressed responsibility for maintaining the road during the subsidence and signs that warned motorists of subsidence area and possible rough road. Again,survey- ing was an important part of the data collection. ]t showed the ef- fects to the county road in the west- ern mining district and then pro- jected the subsidence impact where the long panels were proposed. cepted by the owner and the regulatory agency for per- mit approval. Ln the first two long panels, both types of mitigation have been used where [he track is brought back [o origi- nalgrade and where the new grades after subsidence are within acceptable limits. The primary driver in the miti- gation plan is the daily surr•eying of the track profile and comparisons with predicted subsidence. This determines how much track leveling and grading are required to maintain grades. County road. A 9-m- (30-(t-) wide paved county road traverses the EMD. It is designed for light traffic. The permit process for the county was primarily based on traffic patterns and motorists' safety. Communication with the road maintenance supervi- sors began in the western mining district where a small section of road was undermined by the longwall opera- tion. This showed that the road could be undermined Ventilation A key factor in the early design layout of the long panels for long- wall mining was providing adequate ventilation and safe escape routes for the miners. The first step in the mine ventilation design was an up- dated mine ventilation survey. T'he survey and subsequent model development were conducted with the assistance of a third party contractor. This allowed for a check against ventilation models devel- oped in-house. It also gave credence to regulatory sub- mittals whereby the long panels could be safely venti- lated. One early discovery was that the past practice of ventilating the belt entry to return would not be possible at the proposed length. The mine had an existing peti- tion for modification where belt air could be directed to the face. However, it was realized that dust control would need to be properly managed. As a result of the ventilation modeling, a second main fan was put on line to increase the ventilation capacity. The bleeder system design was developed with ven- tilation and escapeway goals in mind. The design uses return and intake air in the bleeder systems (Fg. 7). A I:?2-m- (oft-) diam shaft was developed a[ [he back of the longwall panels to handle return air from [he gob and seal areas. A second 1.52-m- (5-ft-) diam shaft was installed about 23 m (75 ft) south of the return shaft (or intake air. 7'he intake shaft was de- signed with an PISti CRt~nvF t ~ elevator system Rgl~pgp SCR ((// Cor escape pur- 000NTYROAD poses. And a ~ blowing fan was WESTERN NING DI5T12f(.T FIG. 4 ~w~., M,,: - :~ ~ Eastern mining district with surface FA~ERN MINING DISTPJCr features suhject Powell uNeS to subsidence /i from the longwall FOIDEt CREW nuf mining. 24 DECEMBER 1998 ^ MINING ENGINEERING FIG. 3 Reserve houndary limits that led to the idea for long panels for longwall mining.