These maps are intended to combine data from the U.S. Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (DEQ) in order to display potential contaminant source points in relation to other known features within the Tualatin River watershed. The 712-square-mile Tualatin River watershed in northwest Oregon and the northern Willamette Valley contains a mix of urban industrial, commercial, and residential land use and rural industrial, agricultural and residential land use. Also located within the watershed is the Tualatin River National Wildlife Refuge, one of the only urban national wildlife refuges in the United States. The refuge is home to nearly 200 bird species, more than 50 mammal species, 25 species of reptiles and amphibians, and numerous fish, insects and plants.
The 2001 U.S. Census estimated the watershed's human population at 450,000, and the Tualatin River Watershed Council estimates its land use as 15 percent urban, 35 percent agriculture, and 50 percent forestry. The Tualatin River is approximately 83 miles long, stretching from the Oregon Coast Range east to the Willamette River. Ninety-three percent of the land within the watershed boundary is privately owned. The Oregon DEQ in 2001 identified water quality issues within the watershed to include excess oxygen-consuming organics and ammonia, temperature, bacteria, and excess phosphorus. More information about the watershed.