Lake Miwasin is a demonstration-scale pit lake project that implements a ‘Permanent Aquatic Storage Structure’ (PASS) to treat mine tailings, which are subsequently stored at the bottom of the lake. Lake Miwasin requires levels of water high enough to maintain a threshold freshwater cap over the tailings and the surrounding upland has been designed to contribute water to the lake for this purpose. In recent years, small marsh-like wetlands dubbed “opportunistic wetlands'' have spontaneously appeared on this site. They provide heterogeneity for reclaimed landscapes and have potential to add to the overall amount of wetland ecosystems reclaimed (Hawkes et al., 2020; Little-Devito et al., 2019). However, the study of these wetlands on other sites is limited to a few papers and further understanding as to their function, controls on their permanence, and formation is needed. The objective of this study is to identify the conditions that lead to the formation of opportunistic wetlands and how they differ from constructed features on the Lake Miwasin site. This information aids in learning about the longevity of the wetlands, based on the conditions in which they form and continue to persist, and informs construction of marsh wetlands in future reclamation sites. To accomplish this objective, relative topography from 2019 to 2023 are evaluated and water table dynamics, soil, and vegetation properties in comparison with other constructed features are presented.