These factors are used to determine limits on allowable concentration levels, and to limit the number of violations per year. When issued by EPA, the criteria provide guidance to the states on how to establish their standards. The segment of a river which meets and is influenced by tidal currents. The intersection between ocean and fresh water where the salt water is diluted through integration of the fresh water. Exotic species can be introduced to a region naturally or by human activity, such as the discharge of ballast water by ships.
Exotic species disrupt the native ecosystem by competing for resources needed by indigenous species.
The disposal of dredged material in the river both in and adjacent to deep areas of the navigation channel. The disposal of dredged material in the river, both in or near the area from which it was dredged. It is a product of combustion from transportation and stationary sources and a major contributor to the formation of ozone and acid rain. Water pollution that is diffused and can not be traced to a specific source. Sources of NPS pollution include runoff from agriculture, silviculture, urban development, mining, construction, dams and channels, inappropriate land disposal of waste, marinas, and saltwater intrusion.