TIDAL FLUSHING 



The total surface area of Safe Harbor was 4.48 million square feet 

 (0.416 million m^) and its volume was 101.78 million cubic feet 

 (2.88 million cubic meters). The mean tidal exchange was 1.2 feet 

 (0.366m) (ESSA Tide Tables, 1970) and thus the mean tidal flushing 

 was 5.38 million cubic feet (0.15 million cubic meters) of water 

 per mean tidal cycle or 10.76 million cubic feet (0.3 million cubic 

 meters) per day. During spring tides, tidal flushing increased to 

 about 13.45 million cubic feet (0.38 million cubic meters) per day. 



SEDIMENTS 



Calcuim carbonate silt was 8.6 feet (2.6m) thick in the entrance 

 canal in front of the desalination plant and only 4.5 to 3.5 feet 

 (1.4 to 1.1m) thick in the inner harbor. Sediments in depths 

 shallower than 25 feet (7.6m) generally had a covering of white 

 or brown mud while those at greater depths often had a covering 

 of black silt; the black color derived mainly from H2S, copper and 

 iron sulphide. These compounds formed because of poor water cir- 

 culation in depths greater than 25 feet (7.6m), particularly during 

 summer when there was strong thermal stratification of the water 

 column. During the summer months, the water in these deep pockets 

 was characterized by low oxygen, low temperature, high H2S content, 

 and high water clarity. Core samples of sediment taken to bedrock 

 showed horizons of hydrogen sulfide present in the sediments in 

 the past. This anoxic layer was not present from November, 1970 

 to May, 1971 and during that time the sediment was light grey. 



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