Since the 1950s, some community residents have proposed re-opening the City Canal. They argue that opening the Slough to the Columbia's tidal flow would eventually remove pollutants. In addition, others claim that opening the slough would allow for navigation and increased business opportunities.

   For years, numerous industries including the woodworking companies, oil refineries, and steel production facilities dumped waste into the Columbia Slough. Agricultural pesticides, landfill seepage, airport de-icing fluid, and increased parking lot runoff contribute to the numerous hidden pollutants that affect slough communities. The viscuous film of bloody debris and raw sewage that once covered the Lower Slough is no longer visible, but other less obvious contaminants have led scientists, environmentalists, city officials, the media, and many residents to declare the Columbia Slough a site of "Toxic Waters."