These guidelines describe the process that must be undertaken when a proponent is considering using a natural water body frequented by fish as a Tailings Impoundment Area (TIA) such that a regulatory amendment to the Metal Mining Effluent Regulations (MMER) would be required. In the context of these guidelines, the term, TIA refers to a natural water body frequented by fish into which deleterious substances (such as tailings, waste rock, low-grade ore, overburden, and any effluent that contains any concentration of the deleterious substances specified in the MMER, and of any pH) are disposed. The requirements for the conduct of alternatives assessments that are presented in Part 2 provide useful guidance for the assessment of all mine waste disposal areas including those developed on land. The overall objective of the alternatives assessment process is to minimize the environmental footprint of the disposal area.