a thorough review of existing information on the 

 geochemistry of the Phosphoria Formation, including its 

 potential for affecting surface and ground water. 

 Intense surface and ground water sampling should be 

 conducted to characterize these sources of phosphorus. 

 Wells should be sampled in the Garrison area during 

 summer when ground water is most likely to enter the 

 river and when additional phosphorus would cause the 

 most problems. 



2. Monitor nitrogen loading from the Bitterroot River. 



Conduct intense water quality monitoring along the 

 lower Bitterroot to pinpoint the sources contributing to 

 elevated levels of nitrogen in the Clark Fork system. 

 The Clark Fork should be monitored directly above and 

 below the confluence with the Bitterroot to determine 

 the nitrogen load attributable to the Bitterroot. 

 Septic drainfields and irrigation return flows are 

 suspected sources. 



3 . Limit nutrient loading to the Clark Fork and Lake Pend 

 Oreille. 



a. Criteria for controlling eutrophication in the 

 Clark Fork and Lake Pend Oreille are not known but 

 common sense indicates we should work to limit 

 nutrient loading. The Water Quality Bureau should 

 require that all MPDES permits restrict nutrient 

 loading in compliance with the nondegradation 

 rules of the Montana Water Quality Standards. 



b. Regulatory agencies, industries, municipalities, 

 and public interest groups should work to identify 

 opportunities to reduce all forms of nutrient 

 loading to the Clark Fork Basin. Some additional 

 control of point and nonpoint sources may be 

 necessary. 



DO, Temperature, and Mixing Zones 



It is important to maintain sufficient dissolved oxygen 

 concentrations in the Clark Fork to meet the needs of fish 

 and other aquatic life. Elevated stream temperatures, when 

 combined with suboptimal dissolved oxygen levels, can have a 

 synergistic effect on salmonid populations. Although some 

 work has been conducted to study DO and temperatures in the 

 Clark Fork, additional monitoring is warranted. 



5-16 



