Wastewater

Century West’s experience with wastewater projects starts at the service lateral level through to sewer mains and lift stations and continues to the design of wastewater treatment systems ranging from lagoon systems to mechanical treatment plants. Inflow and infiltration are a major concern for many of our clients, and we bring the expertise needed to reduce inflow and infiltration in wastewater collection systems to meet NPDES permit requirements and required treatment targets.

Contact us about Wastewater Services

Liberty Lake Water & Sewer District, Wastewater Treatment Plant Expansion

Century West provided design and construction period services to upgrade Liberty Lake Sewer and Water District’s facilities, enhancing its water reclamation plant to better protect the Spokane River. Upgrading the plant to treat 1.5 MGD of wastewater, the project saw the installation of a cutting-edge membrane filtration system. Operational since September 2018, this system successfully reduces phosphorus, biochemical oxygen demand, and TSS in wastewater. Additionally, a new treatment building, effluent filtration, chemical systems, a UV disinfection update, and a repurposed fire station for lab/operations were part of the improvements. The project spanned design, installation, training, and post-commissioning phases, including the delivery of equipment and control panels.

City of Portland Bureau of Environmental Services, Wheeler Basin Sewer Rehabilitation

The Wheeler Basin project included approximately 11,600 LF of sewer line replacement and rehabilitation ranging from 8-inch to 30-inch diameter, numerous trenchless construction methods for sewer pipe rehabilitation, design of eight flow-through stormwater planter facilities, and ADA-accessible curb ramp design for six intersections within the project limits. In addition, Century West worked extensively with the City to navigate several new protocols during the project design. These processes included using a new City-wide online file collaboration suite, Bureau of Environmental Services electronic comment review protocol, and overhauling the current Portland Bureau of Transportation pavement rehabilitation guidelines.

Washington Department of Enterprise Services, Monroe Corrections Center Biosolids Removal

Century West was selected through our on-call contract with the Washington Department of Enterprise Services to work with the Monroe Correctional Center to address biosolids accumulating in wastewater lagoons. These lagoons were used to treat sewage before sending it to the Skykomish River. However, the lagoons were filling up and creating capacity concerns. After discussions with the City of Monroe, it was decided to divert the untreated wastewater directly to the city's treatment facility. The team proposed creating a permanent bypass system and only using the lagoons for emergency overflow. The city also set a limit on how much wastewater could be sent from Monroe Correctional Center to ensure the local system could handle it. Century West is currently in the design phase of the project.

Town of Reardan, Inflow & Infiltration Study

Century West provided engineering services for an inflow and infiltration study for the Town of Reardan. Our duties included evaluating flowmeter data, TV inspection videos, and field inspection logs to identify and quantify extraneous flows entering the collection system. The results of this study were used to create a comprehensive sewer plan for the Town’s long-term treatment and collection system improvement goals. Century West also successfully assisted the Town in obtaining a planning grant from the Washington State Department of Ecology to address the inflow and infiltration issues.

Confederated Tribes of the Chehalis Reservation, Wastewater Collection System & Wastewater Treatment Facility Improvements

Century West managed sewer improvements for the Chehalis Tribes, installing a new septic tank effluent pumping system for 21 homes and 5 tribal buildings, using over 8,300 lf of PVC pipes and two 100 gpm pump stations. As part of the project, Century West evaluated the existing treatment plant. The membrane system was deemed capable of treating flows for the next 20 years without requiring expansion. Thus, the team proposed enhancements, including new pumps, piping, electrical controls, and various facility upgrades. Original costs rose by $288K due to extra improvements requested by the Chehalis Tribes, ending the project at $2.5M in June 2022, $41K under budget thanks to cost-saving strategies, including scope reductions on planned enhancements.