The CSO project extends from downtown Port Angeles along the waterfront and the Olympic Discovery Trail, through the former Rayonier mill site, to the city's wastewater treatment plant (WWTP), a distance of about 1.7 miles.
The City of Port Angeles has contracted with IMCO General Construction from Ferndale, Washington for the Combined Sewer Overflow (CSO) Phase 1 project. The Phase 1 project is the first phase of two projects in the Capital Facilities Program.
The Phase 1 construction project will increase the size of the sewer force main (primary interceptor) between downtown and the wastewater treatment plant. The current interceptor is too small to handle peak flows during wet weather. It is located along the shoreline and in some places, in the harbor. Figuratively, it is the main artery of this system, connecting all other wastewater pipes to the plant. By eliminating this bottleneck in the system, much of the CSO problem will be corrected.
The new interceptor pipes will cross Ennis Creek on a bridge that has been sited to facilitate future creek restoration projects. When the project is complete, the Olympic Discovery Trail will be improved, and will cross over the new bridge.
In addition, the wastewater treatment plant will have some internal bottlenecks remedied, which will increase the capacity of the plant.
During the heaviest rain events, the wastewater treatment plant will not be able to treat all the flow as it arrives. At those times, excess flow will be pumped to a 5 million gallon storage tank that will be retrofitted as part of the CSO Phase 1 project. This tank will be gradually drained into the plant during times when flows will permit it.
In addition, the old Rayonier industrial outfall will be retrofitted and placed into service as the city's primary wastewater treatment plant outfall. This outfall is larger, longer, and deeper than the city's existing outfall, and will diffuse treated wastewater more effectively and in a location farther away from the Port Angeles harbor.