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Montana 



Beginning September 1986, and concluding in June 1987, the Montana 

 Department of Health & Environmental Studies (DHES) conducted an 

 ambient air quality monitoring study near Scobie, Montana. Funds 

 for the study were appropriated from Montana's Resource Indemnity 

 Trust Fund (RIT) by the State's 1985 legislation. 



The DHES operated one primary air monitoring site and eight 

 additional sulfation rate sites in the Poplar River area in 

 1986-87. The parameters that were monitored included sulphur 

 dioxide, total suspended particulates, sulfation rate, wind speed, 

 with direction, and temperature. The primary site was located at 

 the Don Marlenee Ranch which is approximately four miles south of 

 the U.S. - Canadian border and one mile east of Highway 13. 



During the year of monitoring, sulphur dioxide concentrations 

 remained less than both the Montana and national ambient air 

 quality standards. The maximum 1-hour concentration of 0.075 ppm 

 was recorded at the Marlenee Ranch site during October, 1986. This 

 concentration is 15 per cent of the Montana standard. The highest 

 3-hour concentration of 0.042 ppm occurred during October, 1986. 

 The highest 24-hour concentration of 0.008 ppm occurred during 

 March and April, 1987. Most of the higher sulphur dioxide 

 concentrations occurred with northwest or north-northwest winds 

 indicating the Saskatchewan Power Corporation generating facility 

 as the probable source. Table 8 sximmarizes the SO. data. 



The Montana and U.S. Federal standards for total suspended 



particulates were not exceeded at the monitoring site. The highest 



3 



24-hour concentration was 144 ug/m recorded on January 21, 1987; 



3 

 the second highest was 140 ug/m recorded on November 10, 1986. 



The reading on January 21, 1987 was caused by fugitive dust 



emissions associated with high wind speeds. 



