SECTION I 

 CONCLUSIONS 



THE EFFLUENT AND ITS DISTRIBUTION 



The desalination plant produced two types of discharge; one emitted 

 when the plant was operating normally (effluent) , the other produced 

 during cleaning and maintenance cycles (effusions) . 



The effluent was turbulently mixed with the ambient water at the point 

 of discharge and, because the combined density was greater than ambient 

 water, it sank to the bottom of the man-made Safe Harbor. Since the 

 harbor was deeper than surrounding flats, the submerged effluent filled 

 the basin to the depth of the surrounding flats. Surplus effluent then 

 flowed onto the flats and mixed with the shallower water. 



The biota occupying portions of the harbor below 16 feet (4.9m) was 

 constantly exposed to the major contaminants: heat, salinity, and 

 copper. Temperature and salinity controlled the depth and density of 

 the effluent stratum but they were not biologically damaging by them- 

 selves. The effluent stratum averaged only 0.3 to 0.5°C above ambient 

 temperatures and only 0.2 to 0.5 o/oo above ambient salinities. To- 

 gether they caused the effluent to stratify and reduced the mixing 

 rate of the other major contaminant - copper. Consequently, copper 

 concentrations were often five to ten times above ambient levels; 

 amounts found toxic to experimental animals in acute toxicity bio- 

 assays. 



Although this situation proved deleterious for the biota in deeper 

 portions of Safe Harbor, the configuration of the system protected 

 shallower areas in the harbor and the surrounding Thdlassia flats. 



Poor water circulation in the deeper Safe Harbor water created an 

 enormous settling tank. Effluent remained in the effluent stratum 

 from 24 to 48 hours and copper, the major deleterious feature of the 

 effluent, was actively absorbed onto sediments during this time. Some 

 copper also precipitated out of the water when the effluent became 

 super-saturated with copper. 



Thus, distribution of the effluent was fortuitous during normal plant 

 operation. It was unfortunate that copper was produced in toxic quan- 

 tities but the biological impact would have been more widely distri- 

 buted had the effluent been discharged into a shallower embayment or 

 directly onto the flats. 



