The Department of Economic Development, Jobs, Transport and Resources (DEDJTR) commissioned Dr Peter Beck of GHD Pty Ltd (GHD) to conduct an independent review of the environmental performance of the Stawell Gold Mine (SGM). Key stakeholders that provided information for consideration in the review included members of the community, interest groups, DEDJTR and SGM. The independent review focused on assessing risks to beneficial uses of the air, land and surface water elements of the environment and discusses community concerns that relate to impacts on the environment which were identified as a result of community consultation completed by Firelight Consulting.
This independent review used a precautionary approach in line with UNESCO 2005 and used the methodology for an independent audit set out in Section 5 of the Department of Resources, Energy and Tourism Leading Practice Sustainable Development Program for the Mining Industry Handbook: Evaluating Performance Monitoring and Auditing. In conducting the review a precautionary qualitative risk assessment method was adopted to assess impacts and risks to beneficial uses of the environment. The independent review was not an Environmental Audit in the context of the Environment Protection Act 1970.
1Key findings and recommendations - summary
This section presents only a summary of the key findings and recommendation; it will be important to read the remainder of the report to appreciate the context of the summary and recommendations, using the information for decision making. A key overall finding was that a lack of relevant monitoring and other information on the environment, emission sources and their impacts had a significant influence on the precautionary approach risk assessment outcomes. This is likely to have resulted in a conservative outcome for the risk assessment. Further information, once available, is likely to result in decreases in risk assessment outcomes provided these further assessments are supported by robust and defensible data that was subject to independent review.
The information review and qualitative risk assessment outcomes were used to develop a series of recommendations to address key data gaps and provide for revision of the risk assessment outcomes using more representative, robust and defensible data. These are detailed in Section 11 (Recommendations) of the report.
2Air quality findings
SGM has been operating ambient air quality monitoring stations at two locations (Fisher Street and Park Road) since 2013, and up to 18 (11 current and seven former) non-directional dust deposition gauges since 1999, to assess impacts on air quality. Monitoring data for the two ambient air quality monitoring stations suggest relatively similar air quality and the concentrations of the majority of the contaminants of concern were within the adopted air quality criteria. This suggests that widespread adverse impacts on ambient air quality in Stawell, as a result of emissions by SGM, are unlikely to have occurred in recent times. However, the two ambient air quality monitoring stations are not for the purpose of monitoring impacts from key SGM emission sources, and as such are not suitably located to assess localised impacts near these sources, in particular:
Impacts probably limited to localised areas around emission sources
Extent of localised impacts inadequately understood
Ambient air monitoring appears to show acceptable air quality in western parts of Stawell
Vent 4, the Mill, the Carbon Recycling Unit Afterburner Outlet and the Tailings Storage Facility (TSF) were considered key sources of potential impacts to beneficial uses of air and a potential risk to human health and the environment as there was a source pathway receptor linkage that was inadequately understood;
The limited monitoring information available for these key emissions sources was used to assess the potential risks the beneficial uses and the results indicated:
Emissions from the TSF were considered to pose a potentially unacceptable impact on beneficial uses of air with respect to human health, ecosystems, local amenity and visibility. The drivers for these findings are the close proximity of the nearest receptors to the emission source, and the lack of relevant emission and ambient air quality data to support a more representative assessment of risk.
Given the dominant wind direction and strength, the emissions from the TSF could travel several kilometres to the north, east and south of the TSF. Emissions towards the west and north west in the direction of the Stawell township would occur under lower strength wind conditions and therefore emissions would travel less distance and not likely to reach significant portions of the Stawell township. However, further work will be required to confirm the extent of emissions travel.
Emissions from Vent 4, the Mill and Carbon Recycling Afterburner Outlet were considered to possibly pose an undesirable impact on beneficial uses of air with respect to human health and ecosystems. Emissions from Vent 4 could also pose a potentially undesirable impact to local amenity and visibility.
Potential impacts of emission from Vent 4 are likely to be limited to several hundred metres around the vent locations, with further assessment required to refine these qualitative estimates.
Further air quality monitoring information will be required to support a more representative risk assessment
The dust deposition gauges do not provide information on ambient air quality but do provide information on fall out and the presence of contaminants of concern in that fallout. As the current gauges are non-directional the value of the data is limited as no information on the location of any potential emissions sources can be established. The monitoring results indicate that a range of contaminants of concern are present in the dust that is being deposited, but to assess the significance further information will be required.
3Air quality recommendations 1 to 6 and 17
The following recommendations were made in relation to management and protection of beneficial uses of air:
Emissions modelling needs to be conducted for the key emission sources including Vent 4, Afterburner Outlet and TSF to assess the extent of potential impacts on and risks to beneficial uses;
Improve monitoring of Vent 4 emissions and include monitoring of PM10 and PM2.5 in the sampling and analysis program;
Improve dust deposition monitoring by switching to use of directional dust deposition gauges and installing an additional seven monitoring locations to better characterise emission from the Mill and TSF, as well as establishing background dust deposition rates and composition; and
Install and monitor ambient air quality at two additional locations to better assess impacts to air quality due to emissions from Vent 4 and TSF, and to assist in confirming model predictions and evaluation of potential impacts to receptors due to emissions from these key sources.
The recommendations related to the Air Element of the Environment were:
Conduct emission modelling to assess impacts on air quality as a result of emissions from Vent 4, Afterburner Outlet, and TSF
Switch to use of directional dust deposition gauges
Install a directional dust deposition gauge at the location of the former DG13
Install four additional directional dust deposition gauges and monitor for hydrogen cyanide around TSF2
Install high volume air samplers to be sampled on the same schedule as the existing two samplers
Identify three locations where directional dust deposition gauges can be installed to establish natural and ambient background dust deposition and composition
Dust deposition has potential to impact land
Soil impacts in Stawell likely due to natural and anthropogenic sources
SGM operates dust deposition gauges that provide information on atmospheric fallout that can affect soil quality. The community also collected eight soil samples from the Stawell Township and had these analysed for a range of heavy metal contaminants of concern. Additionally, information from research into soil quality in the area was also available.
The risk assessment conducted for this independent review found:
Due to the potential impacts of dust and volatile hydrogen cyanide emissions on beneficial uses, and the general lack of relevant data, the precautionary approach adopted for the risk assessment suggests that there is potentially an unacceptable impact on human health, ecosystems, amenity and production of food, flora and fibre as a consequence of emissions from the TSF;
SGM’s underground blasting activities were considered to potentially have unacceptable impacts on buildings and structures, and amenity, with the review identifying key data gaps in monitoring information and a lack of robust and defensible data to assess the risk to protected beneficial uses. While there appears to be merit in the concerns regarding cosmetic damage to buildings and amenity as a result of SGM’s blasting activities, further detailed monitoring and assessment will be required to inform understanding on the significance of the risk and associated impacts;
The potential impacts to beneficial uses of land as a result of emission from Vent 4, the Mill and Processing Plant were considered to possibly present undesirable impacts on human health, ecology, amenity and production of food flora and fibre.
The results found that the soils in the Stawell area show some elevated heavy metal concentrations, which are likely to be the result of natural enrichment by the mineralisation in the area and anthropogenic deposition as a result of urbanisation, and industrial and mining activities. SGM’s contribution to these impacts cannot be established based on the limited data currently available, although some historical dust monitoring from former monitoring points suggests that dust emission from the Mill and the TSF may be a potential source of impacts to soil quality.
Underground blasting activities in the mining operations have the potential to adversely impact the integrity and aesthetic appearance of buildings and structures, as well as impact to amenity, as a consequence of vibration and noise emissions. The current monitoring network may not be adequate in monitoring the effects of blasting in the context of the geological complexity, and variability of building design and foundation materials.
5Land recommendations 7 to 11 and 18 to 20
The following recommendations were made in relation to management and protection of beneficial uses of land:
Collect and analyse 13 surface soil samples at Vent 4 (three locations) and the TSF (10 locations) to assess potential impacts on air and soil quality from dust emissions;
Conduct a review and independent audit of blasting activities to establish the appropriateness of the current monitoring systems, locations and methods; offer installation of monitoring equipment in buildings subject to impacts of blasting; and conduct independent inspections and assessments of properties to identify the mechanism(s) likely to have caused damage.
The recommendations related to the Land Element of the Environment were:
Sample the surface soils of the waste tailings at 10 locations selected on a randomised grid pattern and analyse these for heavy metals, hexavalent chromium and cyanide species
Sample the surface soils at three locations in the stained fall out area at Vent 4
Conduct a full and independent audit of the current blast impact monitoring
Offer to install monitoring equipment that measures peak particle velocity and overpressure
Engage an independent suitability qualified engineer to inspect properties of owners that consider their properties have suffered damage due to blasting
Assess impacts on amenity from blasting and identify measures to limit the impacts
Alternative mining methods assessment
Engage a suitably qualified, independent geotechnical engineer to assess the geological condition and mining history to provide an opinion on the risk of sinkhole development
6Surface water findings
SGM undertakes limited surface water quality monitoring at eight locations. Historical monitoring data at these locations suggests that there were impacts due to emissions of leachate from the TSF to surface water, adversely impacting quality, but since the implementation of the leachate control trenches and pumping wells these impacts appear to have declined.
However, impacts to beneficial uses are observed occasionally even in recent monitoring rounds. The sources and pathways for these contaminants are not fully understood based on the available information. Emissions of dust and hydrogen cyanide from the TSF, and dust from the Mill, could be deposited down-wind in the surface water catchment. Any breach of the TSF dam that could result in discharge of waste tailings into the catchment would potentially have a significant adverse impact on the beneficial uses of the surface water. This limited understanding of source, pathway and receptor linkage resulted in a precautionary outcome for the risk assessment:
Historically impacts occurred regularly but have declined in recent years Occasional impacts still occur
The potential impacts to beneficial uses of surface water as a result of emissions from the Mill and TSF were considered potentially unacceptable with respect to ecosystems, agricultural use for irrigation, and human consumption after treatment;
An additional potential risk to the catchment that was considered to pose a potentially unacceptable impact is the TSF dam and its long term stability. Any breach and discharge of waste tailings could have a significant detrimental impact. Currently only very limited information was available from an independent source on the integrity and long term stability of the TSF dam; and
Other possibly undesirable impacts to beneficial uses as a result of emissions from the TSF included primary and secondary contact recreational use, aesthetic enjoyment, aquaculture and production of fish, crustaceans & molluscs for human consumption.
7Surface water recommendations 12 to 15
The following recommendations were made in relation to management and protection of beneficial uses of surface water:
Modify the existing surface water sampling program to include testing for total and dissolved contaminant concentrations at all existing surface water monitoring locations, and conduct sampling of the drinking water supply dams to assess potential impacts in water quality from key emission sources;
Collect sediment samples at each surface water monitoring location to assess dust deposition and attenuation within the catchment;
Engage a suitably qualified tailings dam stability specialist to conduct an independent review of the design and stability of the TSF 2 dam. This independent review should also consider the review and audit records held by SGM and Earth Resources Regulation to assess the robustness and defensibility of these reviews and make recommendations for improvements as appropriate.
The recommendations related to the Surface Water Element of the Environment were:
Collect water samples for total and dissolved analysis of heavy metals and cyanide species from the raw drinking water supply dams
Collect sediment samples at the current surface water sample collection locations and analyse these for the same analysis suite as the surface water samples
Engage a suitably qualified tailings dam stability specialist to conduct an independent review of the design and stability of the TSF 2 dam
As the risk to protected beneficial uses of the groundwater element of the environment has been consider in the environmental audit currently underway for the TSF, this aspect was not included in this independent review.
The current mining licence conditions cover most aspects of environmental performance, although some revisions to improve and clarify compliance requirements would be of benefit.
The Environmental Audit already under way in relation to impacts to groundwater could be expanded to consider the air, land and surface water beneficial uses as well.
The current Environmental Management Plan used by SGM appears to focus on compliance and could benefit from some revisions and updates to clearly state the compliance criteria adopted to assess environmental performance in the context of a beyond compliance approach. Also, SGM does not appear to be signatories to the International Cyanide Management Code, which promotes best practice environmental management with respect to the use of cyanide in gold mining.
Current Victorian environment protection standards are in line with or based on national standards. While there are some differences in the derivation methodology, particularly for the air quality standards and toxicity data used between Victorian, national and international standards; however, the criteria for the majority of the key contaminants of concern are similar between these standards. There are some exceptions, including arsenic, hexavalent chromium and cyanide, where there are differences in approach and exposure assumptions between Victoria and some other international jurisdictions.
The EMP in place for the SGM operations should be revised to include the monitoring requirements set out in the recommendations, clarifications on the methodology and communication of audit findings should also be undertaken;
SGM and Newmarket Gold should become signatories to the International Cyanide Management Code as part of a continual improvement process and to improve rigour and transparency in their environmental performance reviews.
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