Portland’s wastewater collection system – the largest in Oregon – serves 530,000 people. Environmental Services has 145,000 residential customers and about 13,000 commercial customers. The City’s service area spans more than 94,000 acres. More than 28,000 acres of that area is served by a combined sewer system that mixes sanitary sewage and stormwater runoff. Separate sanitary and storm sewer systems serve the remaining 66,000 acres.
The collection system is made up of a network of more than 2,250 miles of pipe. It has approximately 964 miles of sanitary lines, 843 miles of combined sewer pipes, and 446 miles of storm sewer lines. Portland’s sewer pipes range in size from 4 inches to 12 feet in diameter. Environmental Services contracts with the Portland Bureau of Transporation Maintenance Operatons to maintain the sewers.
Whenever possible, the city uses gravity to carry wastewater from drainage basins to the treatment plants. Somestimes pump stations are needed to move wastewater uphill. Environmental Services has more than 90 pump stations throughout the Portland area.
Staff at the Columbia Boulevard Wastewater Treatment Plant monitor operations at each pump station around-the-clock using computer and telemetry systems. This allows a rapid response to power outages and equipment failures. Work crews routinely check the stations to ensure that equipment is functioning normally and to perform preventive maintenance.
The stormwater collection system includes over 14,000 sumps and sedimentation manholes that collect stormwater runoff from streets and other impervious surfaces.