Although several 24-hour concentrations of total suspended particulates exceeded 

 the Class II Prevention of Significant Deterioration increment, it is likely 

 that the Sasi<atchewan power plant is only a minor contributor. The major source 

 of particulates is fugitive dust from agricultural fields and unpaved roads. 



The annual geometric and arithmetic means for total suspended particulates 

 returned to the low levels experienced prior to I98I; a drought year that was 

 associated with frequent dust storms. The Montana Air Quality Bureau considers 

 that the I982 values are close to normal. These particulates are also well 

 below Montana and United States ambient air-quality standards. In addition, 

 the sulphate and nitrate levels were low and typical of remote unpolluted 

 areas. Visibility measurements taken at the International Boundary site show 

 an average Beta scattering coefficient of 1.9 x 10 per meter for I982. 

 Although the Poplar River area is designated Class II under the Prevention of 



Significant Deterioration increment program, the average scattering coefficient 



-5 -5 



of 1.9 X 10 per meter is well below the Montana standard of 3 x 10 per meter, 



which applies only to pristine Class I areas- 

 Saskatchewan 



Ambient sulphur dioxide monitoring began near Coronach in July 1979- To date 

 a few detectable concentrations have been recorded at this site. The highest 

 concentration recorded in I982 was 3-9 pphm on June 4, which is below Saskatchewan 

 Environment's one-hour air-quality standard of 17 pphm. 



The 24-hour average suspended particulate concentrations in Coronach exceeded 

 Saskatchewan Environment's air-quality standards on three occasions in I982. 



25. 



