Mine and the Mount Morgan township to the Don and Dawson Rivers and then into the Fitzroy River, within the Fitzroy Basin (Basin 130). The Dee River catchment represents 0.63% of the entire Fitzroy Basin. The Environmental Protection (Water and Wetland Biodiversity) Policy 2019 (EPP Water) is relevant to the Project with respect to the protection of EVs and water quality objectives (WQOs). The Callide Creek Catchment Environmental Values and Water Quality Objectives (DEHP, 2013) prescribes EVs for the Dee River and tributaries in developed areas as follows: ∕ Aquatic ecosystems; ∕ Irrigation; ∕ Farm supply/use; ∕ Stock water; ∕ Human Consumer; ∕ Primary recreation; ∕ Secondary recreation; ∕ Visual recreation; ∕ Drinking water; ∕ Industrial use; and ∕ Cultural and spiritual values. The Dee River is classified as highly disturbed from the Mount Morgan Mine to the confluence of the Don River. ARD is the key environmental concern at the mine site, posing a significant adverse risk to downstream catchments, namely the Dee, Don and Dawson rivers. ARD is caused by oxidised sulphide minerals in rocks and soils being mobilised by water moving over or through the sulphide minerals (Unger et al., 2003). This sulphidic waste material was dumped across a large area, including the slopes of relatively steep hills in the upper reaches of the Dee River catchment – factors which have facilitated its oxidisation and transport offsite. Sulphide minerals have been exposed to weathering for more than 100 years in some parts of the mine. Inadequate past mine management practices have left the Dee River in a poor state, where pH is as low as 2.8. High metal concentrations have been recorded in the Dee River next to the mine site during periods of low flow (Wels et al., 2007). While there is no recent evidence of acidic flows extending beyond the Dee River catchment into the Don, Dawson or Fitzroy rivers, there are anecdotal reports of acidic flows extending into the Dawson River when the mine was still working (GreenGold, 2021). Water quality in the Dee River network deteriorated over time due to ARD seepage from the OCP, known as one of the main source points (Markham et al., 2003). In 2000, as a part of rehabilitation planning for this site, the former Department of Natural Resources and Mines (DNRM) engaged EWL Sciences Pty Ltd (Jones, 2001) to undertake a contaminant source study in which the Dee River was monitored. Rehabilitation plans aimed to improve water quality downstream and enable greater usage of water resources by preventing overflows from the OCP (Markham et al., 2003). River water quality monitoring indicates impacts from the Mount Morgan mine site are most prevalent in the first 20 km downstream (AARC, 2017a). The diversity of species in this section of the river is greatly reduced, however some species do exist there. The water quality in the Dee River continues to improve with distance downstream as it is diluted by other freshwater catchment inflows. Although contaminated water seepage from the Mount Morgan Mine has a high level of sulphates (salts), the water quality at the lower end of the Dee River is suitable for irrigation and livestock. The water quality in the Dee River improves with distance downstream as it is diluted by large freshwater inputs further down the catchment. Water quality at Duaringa (140 km downstream of Mount Morgan) is suitable for potable use (GreenGold, 2021).
Project number: 25B061
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