The Oregon Department of Environmental Quality (DEQ) has established total maximum daily loads (TMDLs) for local rivers, which specify the maximum amount of pollutants that various entities can contribute to the Willamette River and tributaries that do not meet water quality standards. 

As one of those entities, the City of Portland has developed a TMDL Implementation Plan that identifies key management strategies to reduce TMDL pollutants from nonpoint (i.e., diffuse) sources and improve water quality.  Many of these strategies are similar to those used to reduce the discharge of pollutants from the City’s municipal separate storm sewer system (MS4) to receiving waters, since the strategies are applied citywide and are relevant to reducing pollution from both point (MS4) and nonpoint sources. The City submits an annual TMDL status report to DEQ to report on the implementation of the strategies.