IN JANUARY 1994, DIVERSIFIED CONTRACTORS, INC. INSTALLED A PORTABLE SOIL REMEDIATION/THERMAL TREATMENT FACILITY ON PROPERTY WITHIN THE BOUNDARIES OF THE AK-CHIN INDIAN RESERVATION IN ARIZONA. THE FACILITY CLEANS PETROLEUM CONTAMINATED SOIL BY HEATING IT IN A ROTARY DRYER TO BURN OFF VOLATILE ORGANIC COMPOUNDS. THE VOC LADEN EXHAUST STREAM FROM THE ROTARY DRYER IS DUCTED VIA A CYCLONE AND BAGHOUSE TO A THERMAL OXIDIZER WHERE THE VOCS ARE DESTROYED. THE TREATED SOIL, AND THE FINE PARTICULATE MATTER FROM THE CYCLONE AND BAGHOUSE, ARE CONVEYED TO A PUG MILL FOR COMPACTING. IN JANUARY 1995, AFTER EPA ISSUED A NOTICE OF VIOLATION, DIVERSIFIED INSTALLED A BAGHOUSE ON THE PUG MILL TO CONTROL PARTICULATE MATTER EMISSIONS. BEFORE MOVING TO THE RESERVATION, DIVERSIFIED OPERATED THE FACILITY IN PINAL COUNTY, ARIZONA, PURSUANT TO A SYNTHETIC MINOR SOURCE PERMIT ISSUED BY THE ARIZONA DEPARTMENT OF ENVIRONMENTAL QUALITY. ADEQ DOES NOT HAVE ANY JURISDICTION ON THE RESERVATION, AND THEREFORE, THE ADEQ PERMIT IS UNENFORCEABLE. THE ADEQ PERMIT REQUIRED DIVERSIFIED TO OPERATE THE BAGHOUSE ON THE ROTARY DRYER TO REDUCE PARTICULATE MATTER EMISSIONS IN THE EXHAUST STREAM TO MINOR SOURCE LEVELS. AFTER DIVERSIFIED MOVED TO THE RESERVATION, ADEQ INSPECTORS COMPLAINED TO EPA ABOUT EXCESS VISIBLE EMISSIONS FROM THE FACILITY. ADEQ INSPECTORS BELIEVED THAT DIVERSIFIED WAS NOT OPERATING THE ROTA