Portland's Integrated Operating Strategy and Results from CSO and Treatment System Operations

Portland operates its completed CSO system using a strategy that integrates operations of the CSO, collection, and treatment systems. The strategy is guided by nine prioritized operating objectives that protect the wastewater treatment system, protect public health from sewage releases, and minimizes CSO discharges. Using the prioritized objectives, Portland formulated a decision hierarchy for making system-wide operational decisions which begin within the treatment plant and reach completion in the CSO tunnels. This paper presents observations, results, and lessons learned from nearly two years of operating the completed system, including treatment performance, effluent quality, and levels of CSO control achieved.