Seattle Public Utilities
The Dalles, Oregon recently completed the first, full-scale wastewater treatment plant installation embarked on by an Oregon municipality and is one of the “first of its kind” in the nation.
The project began in 2015, when the city of more than 15,000 residents chose Kennedy Jenks and Mortenson Construction to upgrade the Dalles Wastewater Treatment Plant to ensure efficient service well into the future. At the time, the WWTP had an immediate need to improve influent pumping capacity headworks screening and increase anaerobic digestion capacity.
Kennedy Jenks served as the design engineer and Mortenson took charge of construction. The team collaborated on a progressive design-build project delivery method for $14.4 million of improvements that would treat peak wastewater flow rates, lower blower operating costs, and generate clean energy. (The city currently operates a microturbine, producing green energy from digester gas to offset electrical consumption.)
The project is notable for the innovative use of primary filtration, which diverts high strength solids directly to the anaerobic digesters to increase gas production. The design-build approach ensured a high level of partnership from the very beginning of the project, incorporating ongoing feedback, avoiding design iteration, and ensuring goals are met
The project’s design phase cost and overall fee structure were determined up front, through a series of workshops which resulted in a guaranteed maximum price. The discussions identified environmental sustainability as a top priority and highlighted the importance of implementing energy efficient solutions, which secured additional public funding to offset the cost of improvements. Upon completion, the plant’s capacity increased from a peak flow rating of 7.7 MGD to a projected capacity of 13.2 MGD, all within a shortened timeline and under the $14.4 million GMP.
Through the use of innovative treatment technologies and efficient project delivery, the result was a project that’s been recognized with a Grand Award at the 2019 American Council of Engineering Companies (ACEC) of Oregon Engineering Excellence Awards Dinner. It stands out as the first municipal PBD for a major wastewater treatment plant in the state, and one of the first full-scale installations of its type in the country.
