19 70 and October, 19 71. 



1. Safe Harbor has an average depth of 22.6 feet. Deep water 

 circulation is restricted by a 17-foot sill in the approach 

 channel. Tidal flushing results in a 10.76 million cubic 

 feet per day exchange. The volume of Safe Harbor is 101.8 

 million cubic feet. 



2. The desalination plant effluent averaged 35°C, 7.0 pH, 

 50.00 o/oo salinity, and 1,766 ppb copper. Its volume 

 averaged 1.33 x 10^ gal/month or about 0.77 million cubic 

 feet per operational day. 



3. The effluent was diluted about twenty times at the point 

 of discharge and sank to form a warm, dense stratum which 

 was found throughout the Safe Harbor basin. The top of 

 the stratum had an average depth of 18 feet. Although it 

 occasionally floated in mid-water, it was normally in con- 

 tact with the bottom. The volume of the effluent stratum 

 was about 20.6 million cubic feet. 



4. The effluent heated the receiving water at deeper stations 

 in Safe Harbor by an average of 0.2 to 0.5°C and raised its 

 salinity by an average of 0.2 to 0.45 o/oo over ambient con- 

 ditions. 



5. Diluted effluent escaped from the system along the floor of 

 the approach canal and along the western edge of the turning 

 basin. 



6. Ambient salinity, the volume of effluent, and the 17-foot 

 sill in the approach channel controlled the depth of the 

 effluent stratum. Intensity of the stratum was closely 

 correlated with total hours of sunshine. 



7. Copper was discharged from the desalination plant at con- 

 centrations up to 6,700 ppb. It was found to be 78.4 per- 

 cent ionic, 3.4 percent particulate, and 18.2 percent or- 

 ganically complexed. 



8. Copper discharge was highest following plant maintenance 

 periods and during periods of unstable pH. Raising pH in 

 the plant significantly reduced copper discharge. 



9. Copper in sediments of Safe Harbor and Lindbergh Bay (St. 

 Thomas, U.S. Virgin Islands) showed the average, long-term 

 distribution of effluent and provided a permanent record 



of copper build-up from pre-plant conditions to the present. 

 Analysis of copper in sediments is a rapid technique for 

 determining the average distribution and intensity of effluent, 



