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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Willamette Plan Area Water Quality

oil to a storm sewerWater Quality

Bacteria and temperature are the primary water quality concerns in the Portland portion of the Willamette River. Concentrations of copper and lead have also exceeded water quality criteria. Trend analysis indicates that dissolved oxygen levels may be declining, but further analysis is required to confirm this trend. Few data exist for many of the 303(d) listed parameters (aldrin, DDT, dieldrin, manganese, mercury, pentachlorophenol, PAHs, PCBs).

In December 2000, Portland Harbor was designated as a federal Superfund site because contaminated sediments have been found in a six-mile stretch of the river, from the southern tip of Sauvie Island to Swan Island. The contaminants of concern include DDT, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals. The City of Portland is participating in a long-term program to clean up the harbor, which will include an analysis of the water quality impacts of the sediment contamination.

Stormwater runoff is the single biggest pollutant source within Portland. Runoff from impervious urban areas contains a range of pollutants from residential, commercial, institutional, and industrial land uses. Transportation areas (roads, parking lots) are a significant source of pollutants such as oil, grease, and metals. Open space areas can be a source of sediments and nutrients. Stormwater runoff can also elevate water temperatures as it absorbs heat from impervious surfaces, and it causes combined sewer overflows that discharge untreated sewage into the Willamette.

In addition to direct discharges to waterways, stormwater is also managed through a system of more than 9,000 sumps and test wells located in many parts of the Willamette Watershed in Portland. Protecting and improving the quality of stormwater entering sumps helps protect groundwater, which often returns to local waterways.

The water quality of the Willamette mainstem is also impaired by upstream sources by the time the river flows into Portland. These include point source pollutants from industrial and stormwater discharges, and discharges from wastewater treatment plants, as well as non-point runoff from agricultural land uses.

The water quality characterization of the river channel in the Willamette plan area focused on identifying parameters of water quality concern based on reference documents. Twenty-four water quality parameters, listed in the table to the left, were considered in the evaluation.

Water Quality Parameters


 Pesticides and Organics
 E. coli
Dissolved oxygen
 Fecal coliform
Total suspended solids
Total phosphorus

303(d) parameters shown in bold italic. For more information, visit the DEQ Willamette TMDL site.