effects of different stressors and provide a measure of 

 their aggregate impact; and 



. Periphyton and other biological communities may be the only 

 practical means of evaluating impacts from non-point sources 

 of pollution where specific ambient criteria do not exist 

 (e.g., impacts that degrade habitat or increase nutrients). 



PROJECT AREA AND SAMPLING SITES 



The project area is located near the town of Circle in east 



central Montana. The Redwater River begins in southern McCone 



County at an elevation of about 3,000 feet and flows northeast 



for about 80 miles, joining the Missouri River south of Poplar, 



Montana. Circle (pop. 716) and Brockway (pop. 75) are the only 

 communities on the Redwater River. Brockway is located about 12 

 miles upstream from Circle. 



The watershed of the Redwater River is situated within the 

 Northwestern Glaciated Plains Ecoregion (Woods et al . 1999). The 

 surface geology of the watershed is composed of the Fort Union 

 Formation, a coal -bearing sedimentary deposit of Paleocene age 

 (Renfro and Feray 1972) . Upland vegetation is predominantly 

 mixed grassland (USDA 1976) . The main land use is livestock 

 grazing with some dryland farming. 



Periphyton samples were collected at four sites, two above' 

 and two below the Circle wastewater treatment ponds (Map 1, 

 Table 1). Elevations at the sampling sites are about 2,400 feet. 

 •The Redwater River is classified C-3 in the Montana Surface Water 

 Quality Standards. 



METHODS 



Periphyton samples were collected following standard 



