A study conducted in the summer of 1986 in the Clark 

 Fork near the Missoula WWTP and Stone Container Corporation 

 by Kerr (1987) involved two 24-hour diel surveys (July 8-9 

 and August 5-6) . Temperature and DO were measured at 

 regular intervals at six stations on the Clark Fork. The 

 objective was to determine whether wastewater discharges from 

 the WWTP and Stone Container Corporation had a measurable 

 effect on DO concentrations in the Clark Fork. The first 

 survey was conducted during a period of high wastewater 

 discharge, while the second occurred during a period of low 

 wastewater discharge. 



Average DO concentrations varied considerably by site 

 and survey. During low wastewater discharge, DO tended to 

 increase in a downstream direction; during high wastewater 

 discharge, it tended to decrease in a downstream direction. 

 The largest change between any two consecutive sites during 

 high wastewater discharge occurred between Shuffields and 

 Harper Bridge and Huson and Alberton. The theoretical net 

 oxygen loss during high wastewater discharge relative to low 

 wastewater discharge was greatest at Alberton. Because the 

 flow of the Clark Fork and weather conditions during the two 

 surveys were quite different, the estimated losses of 

 dissolved oxygen during high wastewater discharge could not 

 necessarily be attributed to the volume of wastewater 

 discharged by Stone Container. 



A diurnal DO survey was also conducted by the WQB in the 

 upper and middle Clark Fork from July 29 to July 30, 1987. 

 In the upper river, the lowest DO levels (about 70 percent of 

 saturation) of the day occurred between midnight and two a.m. 

 Watson (1988a) concluded that with current loading and algae 

 levels, the upper river is at high risk for DO levels below 

 the state standard of 7 ppm when nighttime water temperatures 

 rise above 16° to 18° C and flows tall below 1,000 cfs at 

 Turah and below 200 cfs at Deer Lodge. In the middle river, 

 the lowest DO levels (about 80-90 percent of saturation) were 

 observed between four and six a.m. Watson (1988b) concluded 

 that the middle river would be at high risk for DO levels 

 below the state standard when predawn temperatures rise above 

 18.5° C, and would be at risk at even lower temperatures in 

 extremely low-flow years. 



Color and Foam . Wastewater discharges to surface water 

 can cause increases in river color, particularly under low 

 flow conditions. Kraft pulping processes generate wastewater 

 that contains compounds that are known as foaming agents. 

 Both increased color and foam are potential aesthetics 

 problems in the Clark Fork (DHES 1985) . 



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