"Because of the areal extent and depths of bottom 

 sediments, particularly in the Brandon Road and Dresden 

 Island pools, coupled with the periodic resuspension of 

 the sediments by barge tows, it is doubtful that the 

 aquatic ecology of the waterway can be measurably en- 

 hanced solely by achieving current water quality standards. 

 A program for the removal of undesirable sediments in crit- 

 ical zones probably will have to be devised and implemented. 

 However, any such program should be preceded by a study de- 

 signed to predict the impact of resuspended sediments on 

 downstream DO (dissolved oxygen) resources that would re- 

 sult from sediment removal operations." 



Butts (1974) felt that, "The resuspension of sediments by barge 

 traffic may increase short-term localized oxygen demand loads by seven 

 or eight fold." If the depth of the navigation channel of the Illinois 

 River is increased from 9 to 12 ft, as has been proposed, the increased 

 size of the towboats using the improved navigation channel and the in- 

 creased number of tows would keep more sediment in suspension, with a 

 consequent increase in oxygen demand and turbidity. Figure 5 shows that 

 if towboats pass a point on the river more frequently than once every 

 2% hours, the resuspended sediment will not have a chance to settle out, 

 and the mean amount of suspended sediment in the river will increase. 

 It is likely that river traffic will increase to some extent in the 

 future, whether or not the channel is improved, but it is certain that 

 traffic will increase to a much greater extent if the proposed improve- 

 ments are undertaken. 



The proposed increase in channel depth would be accomplished by 

 a combination of raising low-flow water levels and dredging. Depending 

 on local topography, the water surface area might be increased. Judging 

 by the increased fishery in the Illinois River following a rise in water 

 levels in 1900 as a result of water diversion from Lake Michigan, one 

 might expect a beneficial effect. However, bottomland lakes that now 

 have a chance to clear during periods when they are cut off from the 

 river might then become permanently connected to the river and receive 

 a continuous, rather than intermittent, input of oxygen-demanding silt. 

 Some of the bottomland lakes on the east side of the Illinois River 

 between Kingston Mines (mile 145.3) and Meredosia (mile 71.1) recover 



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