Has grate kiln furnances. This is a plant at a mine. Burning mill residue. The Permittee commenced construction prior to receiving a written air emission permit. During the same period, the Permittee also requested permission to test burn wood and oat hulls in the kiln burners of Lines 3, 4, and 5. The MPCA granted the request, and found out later that permanent equipment had been installed in order to burn these fuels. These actions were allegedly in violation of PSD regulations, and were addressed in a May 15, 1991, Stipulation Agreement between the MPCA and the Permittee.