In Korea, hundreds of abandoned and closed coal and metallic mines are present in the steep mountain valleys due to the depression of the mining industry since the late 1980s. From these mines, enormous amounts of coal waste were dumped on the slopes, which cause sedimentation and Acid Mine Drainage (AMD) to be discharged directly into streams. A limestone slurry by-product (lime cake) is produced from the Solvay process in manufacturing soda ash. It has potential to be used as a neutralizer for acid-producing materials. A field plot experiment was conducted to test the application of lime cake for reclaiming coal wastes. Each plot was 20 x 5 m (L x W) in size on a 56% slope. Treatments included a control (waste only), calcite, and lime cake. The Lime Requirement (LR) for the coal waste to pH 7.0 was determined and treatments consisted of adding 100%, 50%, and 25% of the LR. The lime cake and calcite were also applied in either a layer between the coal waste and topsoil or mixed into the topsoil and coal waste. Each plot was hydroseeded with grasses and planted with trees. In each plot, surface runoff and subsurface water were collected. The lime cake treatments increased the pH of coal waste from 3.5 to 6, and neutralized the pH of the runoff and leachate of the coal waste from 4.3 to 6.7. Surface cover of seeded species was significantly increased with lime cake and the 25% LR plots were sufficient to neutralize the acidity in the coal waste.