_ 38 _ 



Downtime for the opacity monitor was 2.2 percent in 1988 and 0.3 per- 

 cent in 1987. Stack gas flow rates ranged from 378 to 658 m^/s, with 

 an average flow of 590 in 1988, which is close to the 580 m 3 /s in 

 1987. Downtime for the 12 month period in 1988 was 5.2 percent, up 

 from 1.9 percent in 1987. 



Montana 



The Montana Department of Health and Environmental Sciences, Air 

 Quality Bureau, operates five sulfation plate sampling sites in the 

 Scobey area — Richardson Residence (Scobey), Flaxville, TV Tower Hill, 

 Scobey Downtown, and Four Buttes. Samples from these sites are 

 indicators of sulfation levels in the area, and a high concentra- 

 tion would give warning of a potential problem. There is no standard 

 for sulfation rate; readings greater than 0.5 rag/100 centimeters 

 squared per day (cm 2 /d) indicate possible trouble spots. The highest 

 reading for 1988 was 0.07 mg/100 cm 2 /d at the Flaxville site in 

 February. Table 7 gives the sampling results for 1988. 



Table 7. Sulfation Rate of Sulfur Trioxide in Milligrams per 

 100 Square Centimeters per day at Five Locations 

 During 1988. 



Site 



Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 



.01 .04 .00 — .00 .00 .00 .06 .00 



.04 .00 .00 — .00 .01 .00 .00 



.03 .05 — .03 .00 .02 .00 .00 .00 



.03 .04 — .00 .00 — -- .00 .00 



.02 .05 .00 .00 .00 .00 .00 .00 .00 



