The expansion of Pierce County’s Chambers Creek Regional Wastewater Treatment Plant was recently named “Project of the Year” by the American Public Works Association in the “Environment, more than $75 million” category.

“We are proud of the Pierce County employees and partner companies involved with this project,” Dennis Hanberg, Planning and Public Works director, said in a statement. “Winning this award shows that the quality of design, construction, and project management stands out on a national level.”

The 11-year, $342 million expansion project increased the plant’s wastewater treatment capacity by more than 35 percent, from less than 29 million gallons daily to 45 million gallons daily, according to a statement released by Pierce County. Components of the plant, many of which were built in the 1980s, were upgraded to add capacity, better control odor, and introduce new utility tunnels, a new electrical system, and a new laboratory.

One of the key consequences of the improvements is that nitrogen levels in the water discharged into the Puget Sound will be substantially reduced, according to the county.

Pierce County’s sewer system serves 294,000 people in a 117-square-mile area that covers University Place, Lakewood, DuPont, Steilacoom, Parkland, Spanaway, Midland, South Hill, Frederickson, and part of Tacoma. The population served by the plant is expected to double by 2040.

The project began in 2006 and was completed in May 2017. All work was completed while the plant remained in operation. M.A. Mortenson Company was the general contractor, Brown and Caldwell was the designer, and EC Electric was the electrical contractor.