Sunnyside Wastewater Treatment Plant

Gray & Osborne completed a facility plan, permitting, design, construction management, contract administration, and funding documentation for the Lake Stevens Sewer District’s new 5.01 mgd biomembrane filtration wastewater treatment plant to replace its existing 2.4 mgd wastewater treatment facility located in the floodplain and to meet population growth demands over the next 20 years.

The project team included Conley Engineering, Sider + Byers, HWA GeoSciences, and Weisman Design Group. The new membrane bioreactor (MBR) plant, called the Sunnyside WWTF due to its location along Sunnyside Boulevard in the Lake Stevens area, is located on a new 10-acre, upland site. The Phase 1 project completed in 2013
provides a capacity of 5.01 mgd, with the ability to expand up to 6.36 mgd by 2028 within the same footprint.

The project also includes construction of a new pump station, force main, and gravity interceptor to convey flows to the new treatment facility.

The new Sunnyside WWTF includes a headworks building with screening and flow measurement, two primary clarifiers, primary effluent screening, activated sludge basins to provide nitrification and denitrification, membrane bioreactors for filtration of mixed liquor solids, ultraviolet disinfection system sized to meet Class A reclaimed water standards, anaerobic digesters, centrifuge dewatering of biosolids, and odor control facilities.

The treatment plant includes a new administration and  laboratory building. The project was designed for construction in phases to allow for the optimum match between the customer base and capital costs.