3-96 



super saturation during this time of year. In at least one study (Adams, 

 1969) , oxygen supersaturation in thermal discharge has been found to 

 occur without the loss of oxygen to the atmosphere. Oxygen removal can 

 only occur when amJjiont oxygen concentrations are relatively Viigh, and 

 thus has no adverse ecological impact. 



Increased Turbidity , 



The physical model studies conducted by the University of 

 Florida (UOF, 1972) predicted extensive scour of the bottom during the 

 startup of operations at the generating plant if preventive measures 

 were not taken. In response to this prediction, UI installed a pro- 

 tective rip-rap on the bottom at the end of the discharge pipe. Figure 

 3-28 shows the protective rip-rap and selected depth contours from a 

 bathymetric survey conducted by the Army Corps of Engineers in January 

 1978; Figure 3-29 shows selected contours from a survey conducted in the 

 spring of 1974 before the generating station began operations. From 

 these two figures it can be seen that the dredging done when the dis- 

 charge pipe was installed changed the bottom in the vicinity of the 

 discharge. Figure 3-28 shows a short trench or hole that begins at the 

 westerly end of the rip-rap. Though this area may have been dug out 

 during the dredging operations, it may also have been scoured out by the 

 discharged water. It was shown earlier (p. 69) that the plume travels 

 further horizontally before rising to the surface than was found in the 

 physical model. This extended horizontal reach of the discharged water 

 may indicate that the area of the protective rip-rap is less than what 

 is needed to prevent scour of the bottom. If the area of the bottom 



that could be scoured is defined by the 38 ft (11.6 m) depth contour, 



2 

 then Figure 3-28 shows 2327 m to be affected. A sediment trap study 



conducted by Battelle (1971) shows the rate of deposition in this area 



to be about 1.5 cm/mo. If the generating station was taken off line for 



a week the amount of sediment which potentially could be resuspended by 



the discharge would be approximately: 



