Dust Created By Open Pit Mines

Posted by Stop Ajax Mine on September 29th, 2011 2:36pm

When considering what kind of problem could be created by the proposed KGHM-Ajax mine, it is useful to compare the type of operation being proposed by Ajax with another open pit mine, Bellavista Gold Mine. This will give some idea of what creates the dust, how much dust is created, and what quantity of dust can be expected to migrate from the Ajax mine site. The term "Fugitive Dust" is used to describe dust that is created by mining operations, and can escape from the mine site.


The Environmental Protection Agency (EPA) of the U.S.A. states that:

"The impact of a fugitive dust source on air pollution depends on the quantity and drift potential of the dust particles injected into the atmosphere. In addition to large dust particles that settle out near the source (often creating a local nuisance problem), considerable amounts of fine particles also are emitted and dispersed over much greater distances from the source."  In short, the smaller dust particles travel much further than larger ones. 

The EPA goes on to state that the potential drift distance of particles is governed by a number of factors including the initial injection height of the particles, particle size, and atmospheric conditions such as wind and turbulence. The EPA also states that  "Control techniques for fugitive dust sources generally involve watering, chemical stabilization, or reduction of surface wind speed with windbreaks or source enclosures. Watering, the most common and, generally, least expensive method, provides only temporary dust control. The use of chemicals to treat exposed surfaces provides longer dust suppression, but may be costly, have adverse effects on plant and animal life, or contaminate the treated material. Windbreaks and source enclosures are often impractical because of the size of fugitive dust sources."

The Bellavista Gold Mine study (using the USEPA study model) describes two types of dust. Total suspended Particles (TSP) and inhalable particles (PM). It states that The overall mine TSP emissions are estimated to be 114 tonnes/year.  However, the uncontrolled over- all mine TSP and PM emissions are estimated to be 494 tonnes and 206 tonnes per year, respectively, for a total of  700 tonnes per year.

What is the relevance of this information to the proposed KGHM-Ajax mine? 

 Let's look at the Bellavista Gold Mine and see. The following is extracted from a study called:

"Estimation of Fugitive Dust Impacts of Open-Pit Mines on Local Air Quality - A Case Study: Bellavista Gold Mine, Costa Rica

Bellavista gold mine is situated in the Puntarenas Province of Costa Rica.  The mine site is located approximately 3 km northeast of the town of Miramar. The fugitive dust impacts of the mine are of significance for the residents of Miramar and the forested area northeast of the mine site.

Bellavista gold mine has total mineable reserves of 11.2 million tonnes with an estimated project life of 10 years. Ore production will be approximately 1.6 million tonnes per year at its maximum capacity. Gold ore will be mined by conventional open-pit methods utilizing mid-size earth moving equipment. Approximately 2.2 million tonnes of waste rock per year will be excavated during the open-pit mining.

The Bellavista mine is located in a much wetter climate than the semi-arid conditions which prevail at Kamloops. Water is used as their primary resource in dealing with dust problems.

Operation Phase Emission Sources

The emission sources during the mine operation will be from point (stationary), mobile, and fugitive sources. The major point sources will be:

  • Power generators
  • Desorption column boiler
  • Doré furnace
  • Carbon regeneration furnace
  • Cement and lime silos

The major fugitive dust sources will be:

  • Primary, secondary, tertiary crushers/screens
  • Haul and various mine roads
  • Transfer points on the ore conveyors
  • Drilling and blasting in the mine pit
  • Materials handling (loading/unloading, bull-dozing etc. in/on open-pit, waste rock stockpile, leach pad, coarse ore stockpile, and various other material aggregates)
  • Wind erosion of the exposed surfaces (i.e. leach pad, coarse ore stockpile, waste rock stockpile, etc.).

Major mobile sources of air contaminants during the mine operation will be several 50-tonne haul trucks, front-end loaders, bulldozers, backhoes, utility trucks and pickups.


Detailed meteorological information about the mine area is necessary to estimate particulate matter emission rates and atmospheric dispersion of the emissions. Air quality dispersion models usually require hourly meteorological data covering at least a one- year period. In this study, data for the following parameters were used:

  • Wind speed
  • Wind direction
  • Ambient temperature
  • Rainfall amount
  • Atmospheric stability class.

Why we should worry about the possible health impacts caused by dust from the proposed Ajax mine.

Remember, Bellavista has a much wetter climate than Kamloops. Remember also that, despite the KGHM claims to the contrary, the proposed mine is as close as 1 kilometre from parts of Kamloops. Miramar is 3 kilometres from the Bellavista mine. Remember also that Kamloops is downslope and downwind of the proposed mine. And Ajax mine will use the same drilling, blasting, hauling and crushing methods used by Bellavista Mine, because that is how open pit mines operate.  

Compare the following:

Bellavista total annual tonnage of ore and waste rock: 3.8 million tonnes

Ajax total estimated annual tonnage of ore and waste rock: 65.7 million tonnes.

Bellavista uncontrolled over- all mine TSP and PM dust emissions are estimated to be 494 tonnes and 206 tonnes per year, respectively, for a total of 700 tonnes per year.

For a similar mining operation at Ajax - multiply the above by 16. 

This means that the Ajax operation could produce 11,200 tonnes of dust per year. 

And a great deal of it could be blown over Kamloops by the prevailing southwest wind.

All of the above raises some critical questions which must be answered before the mine is given approval to go ahead.

  1. What will be in the particulate matter generated by Ajax?
  2. How much of this particulate matter will fall out in Kamloops?
  3. What are the possible public health effects of this fall out?


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