Table 25. Estimated Quantities of Pollutants that Could Enter Municipal 

 Receiving Waters in a Hypothetical City (Source: Reference 111) 



the boundaries of the site and to release it at a natural rate and in 

 acceptable quality. The stormwater plan must consider the immediate 

 effects of construction activity as well as the long-term effects of 

 operation of the project. Stormwater retention and water quality 

 restoration from a development site usually involve either (1) artificial 

 detention (basin) and treatment system; (2) an adequate vegetated 

 surface for natural treatment, or (3) some combination of the two 

 strategies. In any event, the system should be designed to hold for 

 treatment and slow release the heaviest normal rainfall expected (the 

 5-year or 10-year flood). 



4.12.2 Conventional Systems 



In coastal urban areas, large-scale storm sewer systems often collect 

 runoff and pipe it either (1) directly into coastal waters through a 

 "separate system" or (2) into the municipal wastewater treatment plant 

 through a "combined system" of stormwater and wastewater. On the one 

 hand, the direct discharge (no-treatment) alternative creates high peak 

 flow surges of fresh water, that contains pollutants, to the coastal 

 basin with adverse effects on the ecosystem. On the other hand, the 

 combined treatment alternative often leads to flow surges that overwhelm 

 the treatment system resulting in discharge of raw sewage and stormwater 

 to the coastal basin. 



149 



