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|Tg Soda Ash has operated a shortwall mining system in the Green River, WY trona district since August 1982. The system has proven to be highly productive. In an effort to reduce the amount of relatively expensive development mining and improve mine planning flexibility, a method to mine the return air tailgate during the shortwall retreat was tested beginning in April 1987. As of June 1988, four shortwall panels had been completed using the advancing tailgate, producing more than 739 kt (815,000 st). This paper discusses the effects of the advancing tailgate on shortwall production, development mining requirements, costs, strata mechanics, and ventilation. Shortwall mining is a hybrid extraction method combining the self-advancing hydraulic roof supports from longwall mining and continuous mining machines (Fig. 1). The technique has been only marginally successful at the majority of the nearly 20 installations worldwide. At present, the face at Tg Soda Ash Inc. is the only shortwall operating in the United States and the only noncoal shortwall in existence. Despite the method's record of limited success, the staff at Tg Soda Ash determined that the conditions in its trona mine were well suited for shortwall mining. The commitment to install a shortwall was made in late 1981 and the first panel commenced in August 1982. Between that time and June 1988, about 3.33 Mt (3.67 million st) of trona have been mined with the system from 15 panels. Annual average productivities have ranged from 818 t/shift (902 st per shift) in 1982 to 1.4 kt/t shift (1591 st per shift) in 1987. Overall, the system has produced an average of 1.3 kt/ shift (1450 st per shift). In April 1987, a method of mining the return air tailgate during shortwall retreat was tested (Fig. 2). The objective was to determine if a return airway could be established and maintained by mining a series of rooms and pillars about 7.6 m (25 ft) past the face support line. The method would allow a barrier pillar to be left between shortwall panels without requiring the mining of a separate return air tailgate.|