It has been prepared by the Oregon Department of Environmental Quality based on data and professional observations collected or summarized by federal, state, and local organizations. The list is available for public comment until the end of February, 1996. More precisely, these are waters that do not meet or are not expected to meet water quality standards after application of the best available wastewater treatment technologies to municipal and industrial discharges. Water Quality Limited stream segments are those impacted by point or nonpoint pollution sources to the extent that the water quality is sufficiently impaired to restrict its use. Nonpoint pollution sources are those that enter streams and lakes throughout their surrounding areas, rather than through an identifiable pipe or culvert.
Soil erosion is a good example.
The riparian zone filters sediment from runoff, absorbs nutrients, protects the stream bank from erosion, and provides cover for wildlife. In addition, many riparian zones provide shading of the water surface. By considering the beneficial uses of each water body, specific water quality standards may be applied, thus making the system of standards more flexible. For example, the more restrictive fecal coliform bacteria standards required in shellfish-growing areas need not be met in areas where shellfish are not harvested. Table 1 provides a partial list of the beneficial water uses in Oregon, and the factors of concern that are evaluated to determine whether the water quality supports each use.