New York Times Report: 500,000 violations of Clean Water Act in past 5 years
The New York Times has compiled a comprehensive collection of data on facilities permitted under the Clean Water Act, violations of the law, and enforcement actions. The data shows that enforcement is often lax, but Oregon fairs better than many other states.
The most common violators in Oregon, under the Clean Water Act, are municipal waste water treatment plants, including Portland's facility on Columbia Boulevard.
You can browse the data at http://projects.nytimes.com/toxic-waters.