The EPA reported a more balanced and healthy biological 

 system on the mainstem at and below Garrison and high 

 quality water in streams tributary to the Clark Fork. 



Between 1973 and 1983, a variety of studies were 

 conducted on the Clark Fork (Braico 1973; EPA 1974; Botz and 

 Karp 1979; Janik and Melancon 1982; Hydrometrics 1983b). 

 However, the best records of surface water quality for that 

 decade are from the DHES-WQB station at Deer Lodge and the 

 uses station below Missoula. The station at Deer Lodge was 

 sampled by the WQB sporadically from 1974 through 1977 and 

 monthly between 1978 and 1983. The WQB documented high total 

 recoverable copper and zinc concentrations (up to 800 

 micrograms per liter [ug/1]) associated with spring runoff 

 events, particularly between 1974 and 1976. Although peak 

 concentrations were not as high in the 1977-83 period, many 

 of the concentrations measured exceeded copper and zinc 

 aquatic life toxicity criteria. Total phosphorus concentra- 

 tions were often greater than 100 ug/1 and reached over 500 

 ug/1 on one occasion. 



uses data for part of the same period for the Clark Fork 

 below Missoula document relatively low concentrations of 

 total recoverable copper and zinc from 1978 through 1980, 

 with strong peaks during runoff events in May 1981 and 

 February 1982. Total phosphorus concentrations were 

 generally below 100 ug/1, although they reached a peak value 

 of 770 ug/1 in February 1982 (Brosten and Jacobson 1985) . 



Recent and Current Surface Water Quality Monitoring Programs 



The attention that has been focused on the Clark Fork 

 system in the last few years has prompted a number of 

 agencies to conduct monitoring programs or special projects 

 in the basin. As a result, we now know a great deal about 

 the quality of surface waters in the basin, and we should be 

 able to make much more informed resource decisions. 



The Department of Fish, Wildlife, and Parks measured 

 concentrations of total recoverable copper, iron, and zinc in 

 water in the spring of 1984. Samples were taken weekly 

 between early April and mid-July 1984 at eight mainstem 

 locations and in six tributaries located above Milltown Dam. 

 The data provide documentation of very high metal concentra- 

 tions in the Clark Fork during a runoff event in May 1984 

 when Silver Bow Creek was diverted directly into the Clark 

 Fork (Phillips 1985) . 



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