and hazardous material storage, and wastewater management in accordance with environmental best practice and relevant guidelines and standards. If the amendment is approved, a tailings management plan will also be developed to provide operational strategies to be implemented to ensure that the Upper Mundic Gully TSF is safe and stable and does not cause any further environmental harm through releases.
7.4
Groundwater
7.4.1 Values As with surface water, groundwater EVs and WQOs within Mount Morgan Mine receiving environment are outlined within the Callide Creek Catchment Environmental Values and Water Quality Objectives (DEHP, 2013). The environmental values of the Callide groundwaters (including Dee River) are the same as surface water with the exclusion of human recreation values. The WQO for aquatic ecosystem protection states that where groundwaters interact with surface waters, groundwater quality should not compromise identified environmental values and WQOs for those waters. Groundwater water quality within the Upper Mundic Gully TSF area has not been previously investigated. Most monitoring bores installed at the site are located between the sources of contamination and receiving environment, being the Dee River. Installation of groundwater monitoring bores in hydrogeological and topographical upgradient locations has not been warranted by either the State or various EA holders. Although the groundwater contours show migration of groundwater towards the south east, the influence of the OCP and the Western Dump on the Upper Mundic Gully area is not well understood. The presence of the exposed Western Dump could possibly be contributing to localised impacts to groundwater in this area, however this would require further investigation to determine, which is proposed through conditions identified in Section 2.3 of this document. ARD has severely affected the groundwater at the Mount Morgan Mine, with high levels of dissolved metals including sulfate, aluminium, iron, magnesium, calcium, copper and zinc (Unger et al., 2003). Measures of pH have been as low as 2.5 in previous groundwater measurements (Wels et al., 2007). DSITI (2015) analysed past groundwater quality data recorded from 2008 to derive site-specific set of water quality triggers. The Mount Morgan Mine was classified as a ‘highly disturbed site’, needing thresholds developed from historical data to detect and assess groundwater quality changes more accurately. The bores were divided into zones that reflected their proximity to the OCP, with Zone 1 bores being close to the pit (MB2, MB3, MB5S, MB5D and MB14) and Zone 2 bores being further from the pit (MB8D and MB9). The trigger values presented in DSITI (2015) are based on percentiles of historic observations expressed as two trigger values rather than a single trigger level. DSITI’s (2015) approach was not conventional. It was selected as “a compromise between the more traditional approach that employs a comparison of the median (50th percentile) with a trigger based on the 80th percentile of a historical reference data-set, and the control charting approach [...] that uses three control criteria lines”. In DSITI (2015), Trigger 1 uses the more traditional approach, and it is a statistically robust method for detecting gradual change over the medium term (i.e. 1 to 2 years). Trigger 2 permits the detection of event related change over a relatively short term (i.e. several weeks depending on the sampling frequency). Hydrobiology (2021) provided a review and update of the DSITI (2015) values, with additional data up to September 2018. Impact Assessment The Heritage Minerals Project will ultimately result in improved environmental outcomes at the Mount Morgan Mine through the excavation and historical ARD generating mine waste and 7.4.2
Project number: 25B061
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