3-94 



undcrsaturated with regard to oxygen. The generating station will raise 

 the percent saturation by approximately 17% at discharge. Usually this 

 will be reduced to less than 7% by mixing with the ambient water before 

 the discharge plume reaches the surface. Since the inner harbor percent 

 saturations are generally below 70% from June through August, an in- 

 crease of even 17% would not create a situation where oxygen could be 

 lost by the Harbor waters. 



The example test case shows that, during the winter the gen- 

 erating station could cause oxygen supersaturation in the discharge 

 plume, and that in the example there is a potential to lose 0.4 mg/1 of 

 oxygen to the atmosphere. Whether oxygen is actually lost to the atmos- 

 phere in the Harbor, as occurred in the study by Jacobson (1976) , or 

 whether there is supersaturation without any loss of oxygen, such as was 

 observed by Adams (1969) , cannot be determined from the available data. 



Table 3-8 shows the percent of oxygen saturation at the 

 surface at Stations 4, 8, 9, 11 and 16 for January through December 1976 

 during ebb tide. It can be seen that supersaturation of the surface 

 waters is common throughout the year at Station 16 and at all stations 

 during the winter. These high values are probably due to the rapid 

 natural mixing of water properties that characterizes this and most 

 other estuaries. Station 8, which is most likely to represent plume 

 water, does not show unusually high values of percent saturation. 

 Examination of the dissolved oxygen concentrations observed at Station 8 

 during 1976 reveals that they were not low in comparison to Stations 4 

 and 9. 



In summary, the New Haven Harbor Generating Station has no 

 effect on dissolved oxygen concentrations in the harbor during the 

 summer months when the percent saturation is well below 100%. During 

 the winter, when percent oxygen saturation is near or greater than 100%, 

 the station has the potential for driving a small amount (less than 1 

 mg/1) of oxygen out of solution by heating and mixing of waters; how- 

 ever, natural estuarine mixing in the harbor causes a great deal of 



