Tidal action alone may not rapidly sweep an estuary clean of 

 pollutants. Although estuarine water may be in oscillating motion because 

 of tidal action, the resultant flow may be mostly reciprocal, rather than 

 directional, and the process of discharge to the ocean may be slow in non- 

 stratified estuaries. Clearly, in predicting the effects of pollution 

 it is important to recognize that different types of water bodies are 

 characterized by different assimilative capacities. 



Industrial facilities that cause heavy pollution, such as petro- 

 chemical plants, may have to be banned from confined estuarine waters. 

 Moreover, todal creeks, dead-end harbors, small lagoons, and similar 

 small or poorly flushed water bodies should be off limits for all dis- 

 charges because of their extremely limited capacity to accept and 

 assimilate even small amounts of contaminants. 



Physical and chemical characteristics of the water itself (tempera- 

 ture, DO, suspended solids) will affect the chemical reactivity of pollu- 

 tants such as heavy metals and ammonia, and will determine to a large 

 extent the chemical composition, solubility, and retention time of 

 such pollutants in the receiving waters. Pollutants in the water in 

 certain concentrations may react synergistically, causing a greater 

 impact than if each had acted separately. Such effects have been ob- 

 served for combinations of temperature and oxygen stress and mercury 

 intoxication [131] [132]. There are many such synergistic effects, in- 

 volving combinations of pesticides, detergents, heavy metals, PCBs, pulp 

 mill and sewage waste, petroleum products, radioactive substances, ther- 

 mal pollution, and dredged material. Such complex matters are considered 

 in impact assessment. 



Ranking Basin Waters : It is necessary, in conformance with the plan- 

 ning requirements of the EPA, for each state to classify and rank basin 

 waters according to severity of pollution. This procedure entails 

 delineating and classifying water segments through a process involving 

 assimilative capacity determination, and ranking them in the order of 

 the severity of pollution problems associated with each. 



A water segment is defined as a portion of the basin where surface 

 waters have common hydrological characteristics, common physical, chemical, 

 and biological aspects, and thus, similar reactions to pollutants. These 

 segments are to be classified according to whether or not it is 

 anticipated that water quality objectives will be met after application 

 of 1977 effluent limitations established by the EPA. "Effluent limited" 

 segments are expected to meet the criteria, whereas "water-quality- 

 limited" segments would not. 



4.14.4 Treatment 



Treatment methods vary as widely as the types of processing that exist 

 in OCS-related industries and the diversity of the products manufactured. 



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