EFFLUENT DISPERSION 



1. Copper in the Sediment ; Concentration of metals by marine sediments 

 proved the most useful, least expensive, method of characterizing 

 the dispersion of the effluent. It was also more sensitive than 

 hydrographic measurements and had the added benefit of permitting 

 analysis of the effluent conditions recorded in the sediments dating 

 back to ambient conditions prior to the construction of the desalina- 

 tion plant. 



2. Dye Observations and in situ Diver Observations : Ascertaining the 

 overall distribution of the effluent and its dynamics was facilitated 

 by simply following the top of the submerged effluent stratum which 

 was visually and tactilly detectable by divers. Adding Rhodamine B 

 dye to the sump and visually following the dye with divers permitted 

 more accurate analysis of the flow of effluent through the harbor. 



3. Temperature Inversion Analysis : The hot effluent stratum was easily 

 detectable as a temperature inversion. An electric thermometer 

 proved invaluable in following the dispersion of the effluent and 

 analyses of the position of the effluent stratum could be made 

 rapidly from a small boat. Installation of the Westinghouse ther- 

 mister array permitted instant analysis of the movement of the 

 effluent in the field and the long-term movements of particular 

 isotherms . 



4. Hydrographic Surveys : The twice-weekly analyses of the water con- 

 ditions were exceedingly time consuming and probably did not add 

 significantly to the understanding of the biological impact. An 

 initial hydrographic survey of one or two months would have pro- 

 vided an adequate knowledge of the relationship of the effluent 



in the water column to the amount of copper in the sediment or to 

 temperature inversions and these could have supplanted the less 

 productive and time consuming hydrographic surveys. Of the variety 

 of parameters measured, temperature, salinity, and copper provided 

 the most useful data as they controlled movement of the effluent 

 stratum and its relative toxicity. Alkalinity, pH, and oxygen 

 measurements were not greatly influenced by the effluent and occa- 

 sional (perhaps monthly) measurements would have sufficed. 



The worst feature of the regular hydrographic surveys was their 

 failure to record rapid changes induced by sudden effusions from 

 the desalination plant. These high, transient peaks were more 

 important in damaging the environment than the normal effluent 

 and deserved closer attention. Future surveys should plan to 

 incorporate the analysis of these effusions in hydrographic sur- 

 veys. 



