Newmarket Gold’s Cosmo Howley Project Area (CHPA) is a gold mine in the Northern Territory (NT), Australia. An underground mine is currently in operation with planned underground expansion. CHPA contains several legacy open pits, waste rock dumps, and surface water control facilities. Tierra Group performed a site-wide environmental characterization evaluating climate, geologic, geotechnical, hydrologic, and geochemical conditions. Engineering assessments included groundwater quality, surface water quantity and quality, and geochemical studies. A hydrogeologic model was developed and the current site-wide water balance analyzed and improved. Recommendations for future closure and reclamation plans were developed for permitting support through Australia’s Department of Mines and Energy.