m 



most extensive use of secondary treatment being in the Chesapeake 

 Bay estuarine rejgion. 



Associated with the major metropolitan developments are large 

 numbers of industrial complexes with their attendant waste products. 

 Many of these industrial wastes, especially from the chemical indus- 

 try, are of such a complicated nature that it is difficult both to identify 

 them and to assess their effects on the receiving streams. Only 4,000 

 of the more than 200,000 manufacturing plants in the coastal States 

 account for 97 percent of the total liquid wastes discharged. Of the 

 nearly 22 billion gallons of industrial wastes discharged only 29 per- 

 cent receive any kind of waste treatment. 



Intensification of use of the estuarine zone has resulted in many 

 artificial changes being made in the physical structure. Shoreline 

 areas have been filled to create more land area for residential and 

 commercial use ; channels have been dredged and maintained to permit 

 safer and better navigation ; and harbor facilities have been dredged 

 and bridges and causeways have been built. All of this activity has 

 had impact on the coastal zone ecosystem, but the activities having 

 the most impact on water quality are dredging and filling. The 

 potential for pollution of the system exists in both filling and dredg- 

 ing; both can introduce foreign materials into the water, destroy 

 aquatic habitat, and alter physical circulation patterns. 



The primary source of thermal pollution is from industrial cooling 

 water effluents. Powerplants are the major users of cooling water in 

 the estuarine zone, and power generation capacity has approximately 

 doubled each decade during tMs century. The impact of this growth 

 on the estuarine areas is evidenced by the fact that, in 1950, 22 per- 

 cent of the powerplants were in the coastal zone ; it is anticipated 

 that over 30 percent of the plants will be located there in the late 1970's. 



Estuarine areas are also very important highways of commerce, 

 and thousands of commercial vessels, foreign and domestic, from 

 ocean liners to barges, traverse the coastal waterways each year. Added 

 to this are many of the 1,500 Federal vessels and many nearly 8 

 million recreational vessels. All of these watercraft carry people 

 and/or cargo, and are a real or potential pollution source. 



Mining from the estuary floor causes alteration of the estuarine 

 shape and water circulation characteristics, with a secondary effect 

 being the turbidity problems associated with material removal. Min- 

 ing of sand and gravel from the estuarine floor are universal while 

 oyster shell dredging in any great quantity is restricted to the Gulf 

 Coast. These operations remove part of the estuarine floor with a con- 

 comitant destruction of habitat and life. There are also great amounts 

 of suspended and settleable solids frequently released into the water, 

 from which they are redeposited in other places. 



The water quality of estuarine areas is dependent not only on direct 

 waste sources but also on the quality of the in-flowing streams and 

 runoff entering the system. Tributary influent quality is generally 

 a good index of the type and intensity of land use surrounding and 

 upstream from estuarine systems, and can be a major cause of ecologi- 

 cal stress within the system. The complex interactions between fresh 

 and salt water may magnify the effects of pollutants carried into the 

 tidal regime, resulting m quality anomalies completely alien to either 

 fresh or oceanic environments. 



