2.8 Planning phase

Impacts of dust and other emissions need to be carefully considered in the planning phase of a mining project. The design and layout of any operation are vitally important in achieving an operation that is dust free. Equally important to reducing emissions are the levels of environmental assessment carried out and approaches to obtaining of approvals.

2.8.1 Environmental assessment

An air quality environmental assessment is normally required for a new project. It is important that the assessment team is suitably qualified and experienced. Much time and money can be lost in responding to regulators’ questions arising from inadequacies in air quality assessments. The assessment should be as complete and accurate as possible, identifying all the potential sources of emissions and assessing their impacts.

The air quality assessment may involve establishing the baseline conditions, identifying emissions sources and their characteristics relevant to dispersion, compiling data on meteorology and emission rates, modelling the ground level concentrations of key pollutants (usually particles), describing mitigation measures and, importantly, conveying information to the potentially affected community.

The Victorian Environment Protection Authority’s Draft protocol for environmental management—mining and extractive industry sets out three levels of project assessment:

A level 1 assessment is required when developments are located close to residential areas or urban areas and have the potential to give rise to significant offsite impacts. These assessments are the most rigorous and require the most extensive modelling and monitoring data.

A level 2 assessment is required when the proposed development is in a rural location with residences in close proximity or where a small operation is located in an urban area. A level 2 assessment is required when the proposed development is less likely to give rise to significant off-site impacts due to reduced scale, greater distance from residential areas or inherently lower emissions.

A level 3 assessment is required when the development is in a rural location with no residences nearby. A level 3 assessment is the least onerous due to a lower potential risk arising from emissions from the proposed operations compared to operations requiring a level 1 or level 2 assessment. A level 3 assessment may be required when the development is small, in a location remote from residences, or where it is considered that the off-site impacts would be small compared to sites requiring level 1 or level 2 assessments.

For mines and quarries with less than 20,000 tonnes/yr extraction, no modelling assessment of air quality is required, but emissions on site must be controlled by the application of best practice site management. (EPA 2006)

The specific requirements will differ in detail from one jurisdiction to another, but these Victorian examples are indicative of the rationale for environmental assessments.

The major pollutants of concern are related to dust and specific substances that may be contained within the dust (such as crystalline silica or heavy metals). For proposals requiring an air quality assessment, it is normally necessary to assess PM10, which is the main airborne particle indicator. Depending on the jurisdiction and the circumstances of the site, it may also be necessary to consider PM2.5, respirable crystalline silica (defined as the PM2.5 fraction), arsenic, heavy metals (for example, antimony or lead), hydrogen cyanide, polycyclic aromatic hydrocarbons (such as benzo-a-pyrene), naturally occurring asbestos and radio nuclides or radon. Dust deposition may also be required. Early advice from the regulatory agency is strongly recommended.

Uranium mining poses specific issues around potential exposure of workers and the public to radioactivity. For members of the public, the most important pathways for an operating mine are generally radon transport and ingestion of radio nuclides following surface water transport. For a rehabilitated mine over the short term, the most important pathways are likely to be inhalation of radon progeny and radioactive dust re-suspension, and direct irradiation. Over the long term, groundwater and surface water transport of radio nuclides and/or their bioaccumulation into edible animals and plants that feed or grow on site or associated water bodies may become more significant (DEWHA 2009). Uranium mining proposals require detailed evaluation of these risks.

Some assessment procedures are deemed significant enough to warrant a public inquiry, to ensure that all issues are suitably aired and decisions on approval and conditions are appropriate. In New South Wales, for example, some projects are subject to public hearings by expert panels who make technical comment and recommendations for government to consider. An example is the process that was invoked for the assessment of the Anvil Hill (now Mangoola) coal mine project in the Hunter Valley. A key aspect of this process was the way in which decisions about private property acquisition were made in the light of uncertainties about the accuracy of model predictions of air and noise impacts in the surrounding community.

2.8.2 Value chain planning

The most effective way to manage total group operational costs, human resources and so on is to take a value chain approach—the same applies to mitigating particulate emissions. The effect of a particulate emissions reduction project carried out in the pit will benefit not only the pit and the associated plant but the downstream operations as well.

As a result, it is important to understand where and how particulate emissions mitigation projects can be carried out in the value chain and what benefits can be realised elsewhere.

CASE STUDY: Approval process for the Anvil Hill (Mangoola) coal mine project

The proposal for the Anvil Hill (now known as Mangoola) coal mine in the Hunter Valley of New South Wales was classified as a major project under Part 3A of the New South Wales Environmental Planning and Assessment Act 1979. After the environmental assessment (EA) had been publicly displayed, the Minister for Planning directed that an independent hearing and assessment panel would be constituted in accordance with section 75G of the Act, to assess key aspects of the proposal in more detail.

Under the Act, the Minister for Planning was required to consider the panel’s report in deciding whether or not to approve the project. A panel of experts exercises its functions in accordance with arrangements made by the minister, but is not subject to the direction of the minister regarding the findings and recommendations of its report. The panel provided a report on its findings to the Director-General of Planning.

The panel held meetings with community stakeholders, government agencies and the project proponent in Muswellbrook from 17 to 19 October 2006. The Department of Planning received a total of 2,040 submissions on the proposal and the panel heard 28 submissions at the hearings.

The then Department of Environment and Conservation (now the Department of Environment and Climate Change) initially stated that it could not support the proposal, on account of noise, vibration, air quality, threatened species, Aboriginal cultural heritage and water quality impacts. The department was concerned that the proposal would ‘represent an unacceptable impact on an entire community’ at Wybong, 20 kilometres west of Muswellbrook.

The main grounds for objection were (in decreasing order of mention) greenhouse gas emissions and associated global warming/climate change; impacts on flora and fauna, and surface water and groundwater; noise and blasting; dust; and socioeconomic impacts (given the large number of property acquisitions required for the proposal).

After extended consultation and the design of measures to address these concerns, the Minister for Planning approved the project, subject to conditions under the Act.

Air quality

The panel recognised that air quality modelling contains inherent uncertainties, and that the available criteria do not fully address all aspects of dust impacts, particularly in relation to the nuisance potential from dust deposition. Therefore, it could eventuate that, over time, either more or fewer properties than were identified in the EA would be adversely affected by dust.

A primary issue with the predicted dust impacts was the potential for nuisance, associated with excessive dust deposition, which tends to be concentrated over time into discrete events. However, there are difficulties in adequately measuring and assessing such short-term events, and 24-hour average PM10 concentrations are the main short-term assessment benchmark.

The EA identified proposed measures for controlling both wind-blown dust and dust generated by mining. These measures include disturbing the minimum area necessary for mining, and rehabilitating completed overburden areas as soon as practicable; using water carts on coal handling areas and haul roads; using water sprays on coal stockpiles; using dust suppression equipment on drill rigs and lowering dust aprons; and confining blast charges.

Given some uncertainty about precisely how many and which properties might be affected by 24-hour PM10 concentrations above the 50 μg/m³ assessment criterion, effective ongoing monitoring, dust management and community consultation was identified as an essential requirement. The panel indicated that the property acquisition program might need to be expanded further if actual mine performance were to result in higher than predicted impacts.

Approval condition 27 for the project requires an air quality monitoring program that includes a combination of real time monitors, high-volume samplers and dust deposition gauges to monitor the dust emissions of the project, and an air quality monitoring protocol for evaluating compliance with the air quality impact assessment and land acquisition criteria in the approval. Condition 26 requires the operator to regularly assess real time air quality monitoring and meteorological monitoring and to relocate, modify or stop mining operations as required to ensure compliance with the air quality criteria.

Noise

The EA indicated that, under worst case operational and meteorological conditions, the project would have a moderate to significant impact on a large number of private properties at some stage during the course of the project. Notwithstanding mitigation measures, the project would result in a residual noise impact to a large number of private properties.

The number of properties identified in the EA as likely to be affected by operational noise was 179, including 106 significantly affected properties. By the time the panel made its report, the proponent’s land acquisition program had reduced the number of affected private properties to 118, including 49 significantly affected properties. Independent analysis by the panel indicated that the noise predictions in the EA may have been marginally underestimated for properties to the north-west, meaning that around 10 additional properties might be significantly affected.

To compensate for noise impacts, and given the very low background noise conditions of the locality, the noise conditions placed on the project are significantly more stringent than the standard approach to noise management. They included requirements for the proponent to:

  • undertake (with landowners’ consent) architectural noise treatments at
    • all residences where operational noise levels meet
      or exceed a noise criterion of 35 dBA
    • all residences where traffic and rail noise levels exceed the relevant road and rail noise criteria
  • purchase (with landowners’ consent) any private property that experiences operational noise levels at or above 40 dBA
  • establish and implement a comprehensive noise monitoring program which includes real time monitoring of noise impacts with the view to modifying mining operations as appropriate to reduce noise impacts.

2.8.3 Baseline monitoring

As outlined in Section 2.4, baseline monitoring is normally required to gather site-specific information on existing air quality. The level of monitoring will depend on the potential size of the impact and the sensitivity of the surrounding land use. Monitoring will typically not be required if the site is remote from sensitive receivers and there is an absence of other major emission sources.

For baseline monitoring it may be sufficient to establish one monitoring site, but if there are existing sensitive sites around the project area the possibility of local variations in existing air quality should be considered, and additional monitoring sites established if warranted.

Issues of instrument selection, siting, power requirements, maintenance and data quality must be carefully considered. If a level 1 type of assessment (as described in Section 2.8.1) is required, it will be necessary to measure PM10 (and PM2.5) and to analyse samples for hazardous components such as crystalline silica. For the monitoring of PM10 , if a continuous time-varying background is required for modelling a sophisticated instrument such as a TEOM will be required. These instruments can record data every 10 minutes. Alternatively, a less detailed approach would entail a more traditional highvolume sampler or a partisol sampler, gathering 24-hour average data.

It is important to gather meteorological data as part of an air quality monitoring program. Weather data are important for interpreting air quality data and can be used in dispersion modelling. If it can be demonstrated that representative background data are available from a nearby site, monitoring may not be required.

2.8.4 Modelling and impact assessment

Modelling the dispersion of emissions involves the input of data on emissions, meteorology, terrain and surface roughness (which can be represented indirectly by land use categories). Models require slightly different details for point, volume or area sources to be handled. However, for each source type data are required on location, dimensions, release height and emission rate. Emission rates may be entered as constant values, or may be allowed to vary according to season, time of day or meteorological conditions.

At the planning stage, emission rates for the project must be estimated using best available data and methods, since they cannot be measured. The most common approaches are to use actual data from very similar sources and to scale them according to size, or more commonly to apply emission factors. Emission factors are often used for NPI reporting, and are documented in NPI manuals for a wide variety of activities. However, emissions estimates are inherently prone to uncertainty, and it is important to be aware of the sensitivity of emission rates to the assumptions and data choices involved in using emission factors. Default values provided for various parameters in emission factors can and should be replaced by site-specific data whenever possible.

The planning phase should involve early engagement between project planners and engineers on the one hand and the air quality consultants on the other. Preliminary modelling will identify any potential problem issues, identifying specific emission sources that are likely to have high impacts. This allows for feedback to the design process to modify layouts, processes and the like and iteratively reach a satisfactory result.

2.8.5 Planning for locations of operations and clear areas

In terms of the hierarchy of control, the most important way to prevent dust impacts on mining operations and the local community is to eliminate the problem entirely. Careful planning of the location of operations is the best way to prevent dust becoming a nuisance.

Distance from other activities and consideration of prevailing winds

The geographic location of the operation must be as far away from any existing sensitive receptor (dwelling, village, town, school, hospital, etc.) as is practically possible. This consideration will mitigate visual, dust and noise impacts. In addition, the location must always be downwind (in terms of the prevailing winds) of any such settlement. Once the site has been purchased the location of the mine, plant and stockpiles must be the first consideration in the design of the site. They must be located as far as possible from, and downwind of, any offices or workshops.

Size of the site

When considering the area of land to be purchased/leased, the larger the site the better it is. When a new site is established the land is relatively cheap, so this is the best time to establish a large site. Purchasing a large area prevents the establishment of a local community close enough to the site to be bothered by the site’s operations.

Once a site has become operational, people not associated with the operation will migrate towards the site and, in time, they will begin to impose their will on the operation in terms of their environmental needs. If the site is sufficiently large, the operation’s impact on this new community will naturally be minimised.

Local hills or rises

Never place an operational site on a raised area such as a hill. This is the worst scenario that can be considered, since it exacerbates the effect of the visual, dust and noise impacts of the site on the surrounding area. If a hill is on the site, the most useful place to put the operation is on the downwind side of that hill. The hill will force any wind to blow up and over the site, which will reduce the adverse impact that the site will have on the region.

Existing flora

When preparing the site for construction, do not clear (or allow a contractor to clear) the entire site of trees, bush and grass. The natural fl ora play a significant part in reducing the impact that an operation will have on the region, by hiding the infrastructure, collecting dust in the foliage, slowing and disrupting wind flows and absorbing noise. Specific areas should be designated and cleared as roadways, lay-down areas and construction sites and all other areas of the site should be designated no-go areas for any use.

Roads

The most well-known dust sources on a mine site are the roads. On an annual basis, the roads at an operation will produce as much dust lift-off as the dust generated by the movement of the raw material. When designing or laying out a new operation, the location and design of the roads should take into consideration particulate emissions.

A well designed road will last longer and produce fewer emissions than a quickly and usually poorly built road. Roads and parking areas that are environmentally friendly are usually sealed by one of the chemicals mentioned in Table 2.5. Roads that are laid out with particulate emissions in mind will tend to be downwind of offices, workshops and so on.

2.8.6 Mitigation measures

The planning phase should establish a solid outline of mitigation measures needed to ensure that the future operation will be able to meet air quality objectives. These measures may include:

  • applying specific engineering controls on significant emission sources, such as watering systems for stockpiles 
  • sizing the elements of the project to limit emission rates
  • tactics to be implemented in unfavourable conditions, such as limiting or ceasing activities, or applying controls such as watering, under critical weather conditions.

A critical aspect at this stage is to understand the implications of model uncertainty for the extent and type of mitigation measures that might be necessary once the operation is in place. If actual impacts are greater than expected, additional measures will be needed, so it is important to explore the ‘worst case’ possibilities at the planning stage.

2.8.7 Community consultation

Most communities faced with a new mining project in their neighbourhood will have some negative feelings about it and may vigorously object to the proposal. The onus is on the company to fully and openly explain the project’s impacts on the neighbours, to be mindful of their concerns and, as far as possible, to work with them to resolve any misunderstandings and unreasonable impacts.

Generally, community concerns and their level of negativity are greater if people perceive that the information given to them is incomplete, unreliable or dismissive of the true nature of their objections. Hence, a strictly technically based consultation process may do more harm than good, as there are usually purely personal and perceptual concerns, as well as more pragmatic concerns about property value, amenity and community continuity, that need to be addressed.

A sensitive and serious approach to community consultation is essential at the planning stage, and an experienced consultant expert in this area is an important team member.

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