need for improved understanding of the impact of human activities and better strategies for preventing and mitigating problems in the coastal environment.

The management of wastewater and stormwater in coastal urban areas is inextricably linked to overall coastal management objectives. While wastewater and stormwater management constitute an immense enterprise, they take place in the context of a multitude of other human activities and natural processes within the coastal zone. In addition, there are many difficult tradeoffs associated with the array of options available for wastewater and stormwater management.

This report, as was requested of the National Research Council by the U.S. Environmental Protection Agency at the direction of Congress, examines issues relevant to wastewater management in coastal urban areas. These issues include environmental objectives, policies, and regulations; technology; management techniques; systems analysis and design; and environmental modeling. The National Research Council was not asked to review past policies or decisions. Instead, it was directed to identify opportunities for improving the current system through which coastal urban wastewater and stormwater are managed. The report addresses marine and estuarine areas in particular and does not consider the Great Lakes.

STRESSES ON THE COASTAL ENVIRONMENT

Most coastal water-quality problems result from human activities associated with populations concentrated along the coasts and from land-use practices throughout coastal watersheds. As the U.S. population grows, it is becoming increasingly urbanized and concentrated along the coasts. In 1990, at least 37 percent of the total U.S. population, or approximately 93 million persons, resided in coastal counties, mostly in urban areas (NOAA 1990a). Population growth in coastal areas is expected to continue more rapidly than in other parts of the nation well into the future. As shown in Figure 1.1, coastal areas are the most densely populated in the United States, rivaled only by the Great Lakes region.

More than 1,400 municipal wastewater treatment plants provide service to these coastal populations and discharge approximately 10 billion gallons of treated effluent per day. Approximately 85 percent of this effluent is discharged into bays and estuaries rather than the open ocean (EPA 1992a). More than 100 municipalities serving approximately 16 million persons have combined sanitary and stormwater sewers that overflow at approximately 1,800 points along the coast. In addition to municipal dischargers, approximately 1,300 industrial facilities are permitted to discharge about 11.3 billion gallons per day of treated industrial wastewater and spent cooling water to marine waters (EPA 1992a).



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