In 1973, Falconbridge Ltd. (Kidd Creek Division) of Timmins Ontario implemented the Thickened Tailings Disposal method, which involves the deposition of tailings at 60-65% solids, resulting in a relatively stable and erosion resistant tailings mass. The TTD method attempts to maintain the tailings at moisture saturation, thereby limiting oxidation and thus metal and acid drainage from the tailings. In conjunction with this disposal method, the company is considering the use of de-pyritized and gold tailings, as well as other waste materials such as sewage incinerator ash and granulated slag, as a cover to aid in the revegetation of the site. Growth experiments have shown that none of the materials has a significant effect on germination. De-pyritized tailings appear to provide a better growth medium than pyritic tailings, especially with respect to root growth. Gold tailings support the best root growth, while sewage incinerator ash gives the best leaf growth. In a column leach test, the amount of iron leached from the column was elevated under a cover of gold tailings, sewage incinerator ash or slag, while the amount of copper leached out was increased under a depyritized tailings cover. Apart from these exceptions, amounts of metals leached remained the same or were reduced under each of the covers.