emissions from the entire haul road instead ofjust a small area 

of influence at the sampling point. Due to the higher variability of the wind direction, this effect cannot be seen in the 

graphs of the actual results for August 2nd and August 5th in 

Figs. 8,9,11 and 12. 

Conclusion 

Modeling dust dispersion is an inexpensive method to identify 

potential hazardous areas for mine workers. However, for the 

modeling to be effective, it has to be accurate. The ISC3 model 

is sufficient for modeling dust dispersion from stationary 

sources. However, the DCP is on average 85% better at 

modeling dust dispersion from mobile sources than the ISC3 

model. 

By comparing the modeling and field study results, it was 

concluded that the following causes contributed to the 

overprediction of dust dispersion of the ISC3 model over the 

actual results. The main reason is due to the inability of the 

ISC3 model to handle mobile emissions sources. Applying the 

source (haul truck) emissions over the entire haul road is not 

representative of the actual emissions from a haul truck. 

Applying the emissions as a moving point source along the 

haul road, as accomplished by the DCP, is a better representation of the actual emissions from a haul truck and ensures 

more accurate results. In addition, as the number of trucks 

passing the study area increased, the amount of over-prediction by the ISC3 model also increased. This did not occur in 

the results for the DCP. This effect is related to the previously 

mentioned method of application of the source (haul truck) 

emissions in the ISC3 model. The other cause of the 

overprediction, which would affect both models, is the 

overprediction of the amount of emissions from the source 

when using the emissions factor equations from the U.S. EPA. 

It is obvious that if the amount of emissions input into the 

model is less, then the resulting modeled dispersion will be 

less, resulting in a lower magnitude of overprediction by the 

models. 

The results from the modeling comparison demonstrate 

that the DCP model is clearly an improvement over the ISC3 

model. The DCP model generally better predicts PM 10 dispersion from haul trucks by a factor of two to three. If the 

frequency ofhaul trucks is high (over 200 trucks per day), then 

the DCP's performance becomes significantly better, by an 

order of magnitude, due to the inability of the ISC3 program 

to handle emissions from mobile sources. This has been 

demunstrated fur twu different mine sites that ea{;h have 

different characteristics, one being a stone quarry and the 

other being a coal-mining site. 

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