700- foot (213.4m) portion of the eastern half of the canal and a 

 450- foot (137.2m) portion of the western half. 



The dispersion of effluent was also examined by analyzing copper 

 concentrated in the sediments. Duke et di (1966) and others have 

 shown that sediments concentrate trace elements from seawater. Since 

 the effluent had more copper than ambient water, it followed that 

 sediments exposed to the effluent would be correspondingly higher in 

 copper than sediments not so exposed. Further, sediments are contin- 

 ually depositing and would bury older sediments and leave a continuous 

 record of copper loading in the muddy bottom which could be traced back 

 to conditions before the desalination facility was built. 



Sediments were collected from 150 different locations in and around 

 Safe Harbor. The samples were collected by SCUBA divers using Whirl- 

 Pak polyethylene bags. These containers are inexpensive, compact, and 

 have a wire rim at the opening which serves as a scoop and as a method 

 of sealing the bag. Each sample was taken by opening the bag at the 

 point of collection and carefully scooping up the surface layer of 

 sediment (less than 1 cm in depth) . Four separate sub-samples were 

 taken per bag from each area to provide a composite sample of a larger 

 bottom area. These samples were frozen for later analysis of total 

 copper and foraminifera. 



Core samples were taken at four locations to examine the history of 

 copper levels back to before the plant was constructed. PVC pipe, 

 three inches (6.4 cm) in diameter and three feet (Im) long, was used 

 as the coring device. It was driven into the sediment, capped, and 

 removed. The mud core was extruded with a piston and split in half 

 longitudinally using a thin stainless steel knife. The different 

 strata were noted for age determination later and sub-samples of the 

 core were placed in Whirl-Paks for copper, nickel, and foraminifera 

 analysis. The strata were aged using known data from the history of 

 the construction of Safe Harbor, sedimentation rates from jars 

 placed at all the stations, and by measuring the percentage water 

 content in the upper layers of the sediments. 



Safe Harbor is entirely man-made. Construction of the harbor was 

 carried out over approximately ten years as shown in Figure 6. When- 

 ever a bulkhead was installed or a portion of the harbor dredged for 

 fill, course sediments were produced which formed strata clearly different 

 from the normal fine sediments deposited in the basin. Coarse sand strata, 

 therefore, offered useful datum planes in core samples for checking cal- 

 culated ages. 



The level where the coarse sediment left by the original construction 

 of the harbor canal and the sediment which settled later is clearly 

 deliniated by the microscopic appearance of sediment particles and by 

 the onset of seasonal cycles which have left numerous strata of varying 

 tones of grey. The depth of this level in core samples demarcates the 

 total amount of sediment which has accumulated since that portion of 

 the canal was built. 



28 



