Since 1993, Environmental Services has been working closely with the Oregon Department of Environmental Quality (DEQ) to study the slough's sediment and to eliminate pollutants that reach the Columbia Slough. Studies show widespread, low-level contamination throughout the slough's sediments with a few isolated areas of higher contamination.

The city's cleanup approach includes:

• Working with businesses to prevent pollution from industrial and commercial facilities.
• Stopping unauthorized and illegal discharges to storm sewers that flow directly to the slough.
• Installing filters in city storm sewers to remove pollutants.
• Stopping soil erosion.
• Encouraging homeowners to landscape with native plants and reduce pesticide use.
• Building wetlands to filter stormwater.
• Planting native vegetation on the banks of the Columbia Slough to buffer the water from human activity.
• Engaging residents of the Columbia Slough watershed to ensure they know how they can help keep rivers and streams clean.
• Eliminating sanitary waste overflows into the slough. In 2000, Environmental Services finished building the Columbia Slough Combined Sewer Overflow (CSO) projects, which eliminated CSOs to the slough.

Learn more about our efforts to clean up slough sediment in the most recent annual report or at DEQ's Columbia Slough Sediment Project.