This model for stormwater management and sustainable development practices was completed under a very tight schedule.
WES needed to increase the capacity of the Tri-City Water Pollution Control Plant (WPCP) from an average dry weather flow of 8.4 mgd to 11.9 mgd, and peak flow from 50 mgd to 68.6 mgd. The $90 million Phase 1 Expansion consists of a new membrane bioreactor (MBR) treatment train, a new intermediate pumping station, ultraviolet (UV) disinfection facilities, non-potable water pumping station, and reclaimed water pumping station. Because the existing conventional plant was at capacity, the project was under a very tight schedule. Through a fast-tracked and innovative process focused on partnership and cooperation, the project team selected the membrane supplier and general contractor, completed the design and initiated construction activities in 10 months. A more traditional and conservative approach would have likely taken 18 months or longer.
The MBR treatment train has a 4-mgd average flow and 10-mgd peak flow capacity. The MBR train is operating in parallel with existing conventional activated sludge treatment process. Energy savings was a priority, so the team used high-efficiency fluorescent lighting and skylights throughout the expansion, with a three-level lighting system set to provide additional light only when necessary. Additionally, the design includes eight 300-hp high-speed turbine blowers, high-efficiency pumps, 23-foot-deep MBR aeration basins and a vertical UV system to optimize energy use. WES participated in the PGE dispatchable power program which provides emergency electricity to the community when not needed by the plant.
The MBR treatment system, including UV disinfection, produces a high-quality effluent that meets Class A reclaimed water requirements (the highest recognized by the Oregon Department of Environmental Quality, with facilities for treating and pumping reuse water that help offset water demands on the fish-sensitive Clackamas River.
The design of the Tri-City WPCP also serves as a model for storm water management and sustainable development practices in the Pacific Northwest. The site treats 100% of the surface water onsite – nothing goes into the river. Other sustainable features include membrane treatment for high-quality effluent, facilities for treating and pumping reuse water and heat recovery for in-plant heating, as well as natural systems such as water-permeable roads, sustainable landscaping and green roofs.