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Honokaa^ Haxoaii 



Located on the north coast of the island of Hawaii (largest of the 

 Hawaiian Islands) is a complex of six sugarcane processing plants. 

 These mills are remotely situated along an inaccessible shoreline char- 

 acterized by steep cliffs 100 to 200 feet high. The alongshore currents 

 push the wastes long distances along the shore and then out into the 

 ocean. 



The main effects of the sugarcane wastes have been the shading of 

 coral by the highly turbid waters, the occurrence of high phosphorus 

 and coiiform concentrations, and the lowering of fish diversity and 

 productivity. The slope of the ocean floor near shore is steep and great 

 depths are reached in a short distance. Thus, the mixing and dilution 

 capacity of the deep water minimizes the effects within a short distance 

 offshore, while some wastes drift alongshore with the currents. 



With the mixing and current structure of the steeply sloping ocean 

 bottom, the effects of the sugarcane mill wastes on the hydrography of 

 the area are negligible. There is no significant difference in the oxygen 

 concentration, temperature, or salinity in the outfall area. The color of 

 the waste from the sugar mill is that of the soil carried with the cane 

 from the fields (the common mode of harvesting sugarcane is with the 

 aid of a bulldozer and considerable soil is scraped up with the cane and 

 hauled to the processing mill) . The soil is a bright red-brown color, 

 and this color, plus the turbidity produced by washing the cane before 

 crushing, is discharged into the ocean producing a vivid contrast to 1:he 

 surrounding blue water. The alongshore currents carry this turbidity 

 great distances along the shore instead of allowing it to be diluted 

 further out at sea. 



One of the more distinguishing characteristics of a tropical coast 

 is the large quantity of coral. In the sugar mill waste disposal area 

 at Honokaa, the coral has been completely covered with sludge (com- 

 posed mainly of bagasse and settleable solids) within a radius of one- 

 quarter mile from the outfall. For the next quarter mile on either 

 side of the sludge deposit, the coral coverage has been reduced to about 

 10 percent total coverage. For the third quarter mile downcurrent from 

 the outfall, the coral coverage is between 10 and 55 percent. The coral 

 coverage on the downcurrent side of the outfall does not reach normal 

 density until about three-fourths of a mile from the outfall, where 

 coverage is about 55 percent (considered normal for comparable areas) . 

 There is little doubt that the reduced coral density is a result of the 

 increased turbidity, since coral relies upon light penetration for its 

 formation and maintenance. 



At many sugarcane mills, the normal procedure is to combine human 

 sewage with the sugarcane wastes. This practice results in very high 

 concentrations of coiiform bacteria, because the bacteria in the warm 

 sugar-laden waste multiply rapidly. At the outfall of the Honokaa 

 mill, the coiiform count was 100,000 per 100 milliliters. The coiiform 

 concentration was still as high as 1,000 per 100 milliliters at a distance 

 of 1 mile downcurrent from the outfall. 



Many tropical fish are dependent upon the coral reef structure for 

 protection from predators and on the organisms symbiont with coral 

 reefs for food. Since the coral in the Honokaa sugar mill outfall area 

 was destroyed, it is reasonable to expect that the fish population also 



