Conventional wisdom is that production of wallboard-grade FGD gypsum requires the use of horizontal belt vacuum filters for dewatering service, to limit cake moisture to 10% or less. New Brunswick Power initially planned to use HBVFs for gypsum dewatering for the FGD retrofit to its 3 x 350 MW Coleson Cove plant. However, project budget constraints led to cost reduction evaluations which identified potential cost savings if rotary drum filters could be used instead. This paper documents the cost saving considerations that led to the substitution, including improved building arrangement, reduced equipment cost, and reduced power requirements. The operating performance results of the rotary drum vacuum filters at Coleson Cove are presented, proving the capability to produce wallboard quality gypsum filter cake with moisture content as low as 6%. Key aspects of the design and operation of the filters that make rotary drums a viable choice for dewatering are presented.