The City of Astoria’s wastewater system serves approximately 10,000 residents across nearly four square miles and treats an average of five million gallons of wastewater per day. The modern wastewater treatment system, including the treatment plant, pump stations, and interceptor line, was constructed between 1972 and 1974. Prior to that time, untreated sewage from the city was discharged directly into the Columbia River and Youngs Bay.
Astoria’s wastewater collection system includes approximately 72 miles of sewer lines, nearly 4,000 service connections, 1,546 manholes, and nine pump stations. Many sewer lines date back to the late 1800s and connect to an interceptor pipe that runs along the city’s waterfront, conveying wastewater to the City’s lagoon-based treatment facility. Operation and maintenance of the system is funded through sewer utility rates.
The wastewater treatment plant uses an aerated lagoon system, where natural biological processes break down organic waste with the assistance of mechanical aerators. After treatment and disinfection, the treated water is discharged into the Columbia River. Wastewater entering the plant is regularly monitored and tested to ensure compliance with treatment standards.
Much of Astoria’s system is a combined sewer system, meaning both wastewater and stormwater flow through the same pipes. During heavy rainfall, flows can exceed system capacity, resulting in combined sewer overflows (CSOs) that discharge diluted wastewater into the Columbia River and Youngs Bay. To address this issue, the City is implementing a $50 million CSO reduction program mandated by the Oregon Department of Environmental Quality (DEQ) to significantly reduce these discharges. Four of the five phases of the CSO program have been completed, representing major progress toward improving water quality and reducing overflow events. A CSO surcharge, established in 2002, helps fund these improvements.
In addition, the City operates and maintains approximately 35 miles of stormwater lines, including catch basins, manholes, detention facilities, tide gates, culverts, and cleanouts. As CSO projects are completed, new stormwater infrastructure continues to expand and improve the City’s stormwater management system.
For more information about the Astoria wastewater and stormwater systems, please visit the links below.
