BHP Billiton Iron Ore initiated a program in January 1995 at the Mt Whaleback operation in Newman, Western Australia to develop a closure plan for the overburden storage areas (OSA), which have the potential to generate acid rock drainage. The primary research program includes the development of technology for the long-term performance of OSAs with respect to slope stability, surface run-off, erosion, water infiltration and vegetation. The objective is to control acid rock drainage by preventing moisture movement into and through the OSA material. Infiltration to the underlying OSA material and closure costs are minimised due to the presence of the run-of-mine (ROM) cover material. A summary of the field data is presented to illustrate low percolation rates to the underlying OSA and key performance characteristics of the moisture store and release cover system design. Field data collected to date demonstrates that a moisture store and release cover system constructed with suitable ROM material has good potential as a final cover system at the Mt Whaleback site. The performance of the cover system on a sloped surface was significantly different as compared to placing the cover system on a horizontal surface.