Combined Sewer Systems
The Everett wastewater collection system is divided into 2 distinct areas: a north end combined sewer system, and the south end separated sewer system.
Combined Sewer Overflows
Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, the combined sewer system conveys all of the wastewater to the Everett Water Pollution Control Facility, where it is treated and then discharged to either the Snohomish River or Port Gardner Bay. During periods of heavy rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system. For this reason, the combined sewer system is designed to overflow occasionally and discharge directly to the Snohomish River or Port Gardner Bay. These overflows are called combined sewer overflows (CSOs).