Discovery Corridor Wastewater Transmission System (DCWTS) Phase 1

Location: Vancouver, WA
Client: Clark Regional Wastewater District/City of Ridgefield

The City of Ridgefield has historically been one of the fastest growing communities in Washington State. Hampering their growth potential has been the availability of wastewater treatment capacity. The City has been studying treatment options for many years, and decided to build a new transmission main and has partnered with the Clark Regional Wastewater District (District) to construct a pipeline to existing District infrastructure at the north limits of Vancouver’s urban area.

Otak has been assisting the City in studying wastewater treatment and conveyance options for more than six years. Work has included assistance in their selection to build a pipeline south, and then once the decision was made, Otak led the effort to develop the DCWTS. This included routing studies to determine the best route south, population and flow projections, and studies to determine the best connection point. The study recommended a route, pipe sizes and diameters, pump station locations, and preliminary designs and cost estimates for the recommended route. Additional responsibilities included the development of an engineering report meeting Washington Department of Ecology standards, and the development of 30 percent plans and a design report. The design report included evaluation of pipeline and pump station hydraulics, evaluation and selection of pipeline materials, and details on operational design features of the system. Pump station layouts and architectural design features were also be developed with the preliminary design.

The DCWTS includes a phased approach to building the system that allows for “just in time” construction of new phases, and has been designed to provide capacity for at least 20 years. It also includes a new pump station in an area of potential future development. Otak also led the team that developed construction documents for Phase 1 of the DCWTS, a $25M project includes upgrades to two pump stations, construction of two new pump stations, and construction of nine miles of 14-inch to 16-inch force main.