3-93 



4 m depth has a salinity of 22.4 ppt, a temperature of 4.8 C, and a dis- 

 solved oxygen concentration of 11.5 mg/l. The solubility of oxygen in 

 water with these properties is 7.6 ml/1 (10.9 mg/l at 1 atms) . This 

 means that the? plume water is 106% saturated at a depth of 4 m. At 4 m 

 the volume of 11.5 mg/l of oxygen is less than the saturation value, so 

 there is no tendency for the oxygen to come out of solution. When the 

 plume reaches the surface it has been diluted by an additional factor of 

 approximately 25 to 1. Assuming that the last 4 m of the water column 

 has a salinity of 10 ppt, a temperature of 1 C and is 100% saturated, 

 the discharge water would have a salinity of 19.9 ppt, a temperature of 

 4 C, and a dissolved oxygen concentration of 11.8 mg/l when it reaches 

 the surface. With these properties, the discharge water at the Harbor 

 surface is 105% saturated with oxygen and could potentially lose 0.4 

 mg/l of oxygen to the atmosphere. 



The potential for this loss of oxygen to occur in water which 

 has passed through power plants has been recognized and studied at other 

 locations. Jacobson (1976) studied the oxygen balance in the condenser- 

 cooling water system of the Connecticut Yankee Plant and found that 

 oxygen concentrations decreased throughout the cooling system (which 

 unlike the New Haven Harbor Generating Station system included contact 

 with the atmosphere before discharge into the river) when intake waters 

 became supersaturated upon the addition of heat. These losses ranged 

 between 0.9 and 1.3 mg/l and usually occurred at ambient water tempera- 

 tures below 6 C and at ambient dissolved oxygen concentrations above 

 11.8 mg/l. Dissolved oxygen concentrations remained virtually unchanged 

 after passage through the condenser when percent oxygen saturations in 

 the heated water were below 100%. Adams (1969) , studying two tidewater 

 power plants in California, noted supersaturation of oxygen in the 

 discharge waters but found no changes in dissolved oxygen concentra- 

 tions. 



The situation that appears to exist in New Haven Harbor is 

 that the generating station has little effect on the amount of oxygen 

 dissolved in the Harbor waters. During the summer months, the harbor is 



