The University of North Dakota Energy and Environmental Research Center (EERC) conducted a two-part investigation of known and suspected ash-related problems that occur when a Montana subbituminous coal is burned in Unit 4 of the Clay Boswell Steam Electric Station near Cohasset, Minnesota. The research was performed in cooperation with Minnesota Power and a coal company. The target coal was termed Coal A to maintain confidentiality. A second Montana subbituminous coal, Coal B, was used for comparison purposes. The first part of the work was designed to determine whether firing Coal A created deposition or corrosion problems in the convective pass of the boiler. There were three areas of interest: corrosion of steam tubes in the reheater, downstream and cross-pendent deposits in the primary superheater and economizer, and hard deposits at the top of the secondary superheater. The goal of the second part of the investigation was to determine why the opacity of plant emissions were higher when burning 100% Coal A as compared to a 70/30 blend of Coal A and Coal B. Once the causes of the higher opacity were identified, a strategy for reducing the emissions was to be proposed.