DO concentrations were generally below saturation 

 at all other stations except during periods of 

 maximum photosynthesis. However, minimum values 

 did not drop below 6 mg/1 at any of these stations, 



Braico attributed the results of the study to a 

 combination of factors, including extremely low streamflow 

 (less than half of normal) , loss of shade-producing bank 

 vegetation due to highway construction, warm weather during 

 the study, and heavy algal populations. 



Knudson and Hill (1978) summarized past data and 

 collected new information on inutrients, dissolved oxygen, and 

 algal accrual in the upper Clark Fork during 1976 and 1977. 

 They concluded that summertime nutrient concentrations were 

 elevated just below Deer Lodge and Missoula but were 

 relatively low in other locations. Among the tributaries, 

 only the Bitterroot had elevated nutrient levels. Lowest 

 dissolved oxygen levels were recorded in late July and early 

 August near Deer Lodge and Bonita. 



In 1984 and 1985, the WQB conducted a number of water 

 quality studies in the Clark Fork between Turah and the Idaho 

 border, partly in response to the controversy surrounding 

 the discharge permit issued to the Champion International 

 mill (now Stone Container Corp.). Five sampling runs 

 provided ambient water quality data on DO concentrations. 

 Because sampling was done at all hours of the day, the 

 diurnal variability of DO may have masked the affects of 

 deoxygenation caused by organic decomposition, making 

 changes in DO difficult to interpret. However, the DO data 

 suggested that much of the oxygen demand from the Champion 

 discharge was satisfied within the mixing zone from the 

 Champion outfall to Huson. The effects of instream dilution 

 on the wastewater would diminish the oxygen demand to nearly 

 unmeasurable levels (DHES 1985) . 



Diel DO monitoring runs were also conducted in August 

 1984 and 1985 to determine daily oxygen maximums and minimums 

 at sites above and below the Champion mill. Results of this 

 monitoring did not indicate a problem with DO levels in the 

 Clark Fork. However, one run was conducted when the waste- 

 water discharge was highly diluted, and the other was done 

 during a period of no wastewater discharge. The data 

 therefore represent only a narrow range of conditions (DHES 

 1985) . 



Self-monitoring data from Champion (a requirement of 

 its permit) for the period of January 1984 to September 

 1985, revealed DO concentrations below 7 mg/1 on 12 days. 

 No waste was discharged on nine of those days (DHES 1985) . 



3-81 



