...Silica continued...

Dust, including silica dust, is generated by everyday activities everywhere.

The last Update (July 14 2009) looked at sources of silica, and the range of industries, other than mining, where workers are exposed to it.

This Update describes the steps we take at the mine to manage and monitor crystalline silica in order to protect our workforce and maintain a high standard of air quality. It also compares Environment Waikato's air quality monitoring results in other towns to those in Waihi.

 

What steps are taken at the mine to CONTROL silica dust?

  • Applying dust suppression product (see Update April 21 2009)
  • Watering haul roads and using sprinkler systems and water sprays where required
  • Dust collectors and filters on drill rigs and crushers
  • Using a windbreak fence adjacent to the crushers
  • Keeping stockpiles low so wind is less likely to spread dust
  • Planting grass to cover long-term stockpiles
  • Planting pasture, shrubs and trees as soon as rehabilitation areas are available
  • Washing vehicles before leaving site to travel on public roads
  • Wearing personal protective equipment

Water Truck

Applying dust suppression emulsion to haul roads.

Inset: Washing vehicles before they leave site. This prevents mud on roads turning to dust when dry.

Storage Lakes

The southern side of Storage 2 (left) and Storage 1A (right). To date 52.4% of the total dam area has been rehabilitated and a further 8Ha to the right of the photograph will be completed in stages through spring and summer. Weather permitting, by the end of summer around two thirds of the total dam area will be rehabilitated.

 

What steps are taken at the mine to MONITOR silica dust?

In the mining industry in Waihi, as in other industries where employees are potentially at risk of exposure to crystalline silica dust, a range of measures is taken to protect the workforce and to monitor the effectiveness of these measures. Annual health checks on workers are carried out by Occupational Health and Safety (OHS) staff. This independent body is affiliated to the NZ Institute of Safety Management. In addition, personal dust monitoring measurements are routinely made by Newmont and by independent occupational hygienists.

Waihi Gold has been monitoring dust emissions since 1982, along with the Department of Health. Our specialist consultant on air quality states that the company's dust monitoring programme is "the most extensive around an industrial enterprise in New Zealand". Monitoring has provided a continuous dust database as good as, or better than, anywhere else in New Zealand.

At the mine and around Waihi monitoring is carried out for the three different types/sizes of dust particles: deposited particulate, total suspended particulate (TSP) and for PM10/silica.

Continuous monitoring for PM10/silica has been undertaken by Environment Waikato since 2007. Before that, NWG employed a mobile monitoring unit to record data for a few months once every two years. The equipment currently used by EW is called a Partisol air sampler. An electric pump sucks in air, just like a vacuum cleaner. The air is first drawn through a special inlet that only accepts particles up to 10 microns and then filters it. The sampler automatically changes filters daily.

NWG's monitoring method for TSP includes six air monitors fixed in raised positions, such as on power poles. The process is similar to the Partisol sampler except no special inlet is used (all suspended particles are filtered). Technicians change filters weekly and record the volume of air that has passed through the pumps. The used filters are then weighed and results are entered into a database, which is reported to Environment Waikato.

The monitoring data from EW and that from NWG shows a very strong correlation and provides a high degree of confidence that NWG's monitoring carried out over many years is an accurate record of air quality in Waihi.

Changing Filter

Changing the filter in one of the air monitors.

Further information
The information on this page relates to PM10/silica. More information about dust can be found on the links on our homepage.

 

What does the monitoring tell us?

Monitoring results show:

  • Measured inhalable dust levels are well below those set to protect against health effects.
  • Crystalline silica levels are very low.
  • Metal concentrations of the dust are very low and compare with levels in other small towns. Urban area levels are much higher.
  • No employee or contractor has displayed health effects related to air quality. Mine employees or contractors would be the first to display any such effects as they work on site close to potential dust sources.
  • Air quality in and around Waihi is not deteriorating.
  • Results for Waihi are comparable with those from other small urban areas. This is what might be expected for a township located adjacent to a major highway.
  • Air quality is often at its worst in winter due to air contaminants from domestic fires.
  • Continuous monitoring since the start of the project shows that 99% of all dust measurements are within compliance with consent conditions and that the other 1% was attributable to activities that were not mining-related.

How does Waihi's air quality COMPARE to other towns in the Waikato?

In the Waikato EW carries out inhalable dust (PM10) monitoring at Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata, Putaruru, Ngaruawahia and Waihi. A summary of results for 2008 is in the table below, sourced from the EW report found on their website: www.ew.govt.nz/PageFiles/11956/TR0904.pdf

Summary Chart

Measurements given are in micrograms per cubic metre (µg/m3).

One microgram is equal to one-millionth of a gram.