Mine productivity at oil sands mines can be adversely affected by the presence of large frozen oil sands lumps that jam crushers causing unplanned crusher downtime. Lumpy loads in haul trucks are diverted to lump dumps in the winter to reduce occurrences of crusher jams. This paper documents the problems caused by large oil sands lumps generated by hydraulic and cable-electric shovels using production data linked to climate and equipment performance. Upper benches and the Upper McMurray facies groups were found to be more likely to generate lump dump loads as well as lump jams. Hydraulic shovels were found to generate more loads delivered to a lump dump than cable-electric shovels on a normalized basis. Methods to minimize the occurrence and effects of frozen lumps and ways to improve overall mining efficiency during the winter months are suggested. Read less