West Yost prepared a Sanitary Sewer Master Plan for the Clean Water Services District (District). The project included evaluating the system, expanding and updating the collection system hydraulic model, and ranking problem areas according to severity of surcharging under three development conditions to differentiate between near-term and long-term projects.
The District operates four wastewater treatment plants and 39 pump stations, serving 12 member cities and unincorporated areas surrounding Portland, Oregon. The District partners with the cities to build and maintain the public sanitary sewer and surface water management system, primarily in urban Washington County, as well as small portions of Portland, Lake Oswego, Multnomah and Clackamas Counties.
Six years of land use planning and collection system construction triggered the need for an updated sanitary sewer master plan for the 122 square mile District serving a population of 500,000 near Portland, Oregon. Significant but well-managed growth is expected to eventually increase the population served by as much as 50%, through a combination of; urbanization of undeveloped areas, densification, and infill development.
Such growth will result in a need for new sewers and pump stations, wastewater treatment plant expansions, and upsized replacement sewers. West Yost evaluated the system by expanding and updating the collection system hydraulic model. During this work, the model was enhanced to include 10-inch and larger sewers, and 23 previously unmodeled pump stations.
The updated master plan ranks problem areas according to severity of surcharging under three development conditions to differentiate between near-term and long-term projects. Individual projects are described in an accessible, convenient data sheet format that summarizes all relevant information such as flows at various growth milestones, a map of the pipeline alignments and pump station locations, and identification of any unique project features that will affect costs. The master plan document is a valuable tool useful to District staff during their day-to-day work.
Due to the size of our system, the amount of data collected, updated, verified and analyzed was substantial. The results of the updated plan provide a valuable mix and balance of detailed information needed for decision making and graphical presentations summarizing large amounts of information in a format that facilitates big picture assessments. These elements of the master plan are useful in conveying information and concepts to a broad audience.