Advance Notice at Flin Flon

At the Hudson Bay Mining and Smelting company’s copper smelter in Flin Flon, Manitoba, the plant’s exhaust stack is only 300 metres from the town’s uptown area. Another town, Creighton in Saskatchewan, is about two kilometres away.

To help to protect these nearby communities the company developed an Air Dispersion Model with the help of environmental engineers from AECOM’s Winnipeg office. The model is to predict atmospheric concentrations of sulphur dioxide, taking into account known emissions data as well as forecasted meteorological conditions and the local topography. Based on predictions provided by the model, the company can make production changes and alert the local communities when there are potential air quality concerns over the next few hours.

The metallurgical facility produces anode copper for shipment to a refinery in Michigan. It has a copper smelter, zinc plant and a concentrator. Sulphur dioxide releases are primarily from the 250-metre stack located at the north end of the 875-hectare site. While emissions data from the stack was readily available, fugitive emissions are experienced in other parts of the smelter, and AECOM incorporated those emissions into the model.

The meteorological data is collected continually throughout the day using the United States Air Resource Laboratory’s website. (The U. S. data includes Flin Flon Airport, and is more comprehen- sive than the Environment Canada website.)

The height of the plant’s stack (one of the highest in North America), extreme temperature variations in this northern location, and unique topographical features such as surface bedrock and lakes, made the modeling unique. Lakes, for example, cause temperature gradients that play a significant role in dispersing plumes.

The modelling is based on CALPUFF, which uses a 3-D meteorological wind field to advect and disperse a plume over the model’s domain. The model can be dynamic, or it can be statically run on a daily basis. A graphical user interface generates an animation file to show the emissions concentration over a local area base map.

Manitoba’s air quality guidelines determine the emissions threshold at 0.34 ppm of sulphur dioxide as the point when the community should be notified. A level 2 condition exists when any one-hour average of sulphur dioxide is greater than 0.34 ppm. At that level people are advised to remain indoors with the windows closed, not to exercise or smoke, and to take other precautions.

Clifton Samoiloff of AECOM says that from the model results it appears that in terms of emissions from the stack, the worst conditions for dispersal occur during the breakup of a low level morning temperature inversion.

Prime consultant: AECOM Winnipeg (Clifton Samoiloff, B. Sc., Jeffrey Connors). Client: Hudson Bay Mining and Smelting Co.