Treating Salem’s Wastewater


We collect and treat sewage (also called wastewater) to protect public health and local waterways.

What is wastewater? 

Wastewater includes the used water from inside a home, business, or an industrial building for something like food processing. Any time water goes down a drain in your sink, shower, or toilet, the used water becomes wastewater and must be cleaned before it can be re-used.

About Salem’s Wastewater System

In Salem, wastewater leaves a building, flows through underground pipes, and is pumped to the Willow Lake Wastewater Pollution Control Facility. Once at Willow Lake, the wastewater is treated to clean it so that it is safe to be released to the Willamette River for downstream communities to re-use.

Salem’s wastewater collection system (also known as a sanitary sewer system) was designed to collect wastewater, not runoff from rain or snow events. (That’s called stormwater, which we catch in storm drains on streets. Learn more about stormwater here.) Sanitary sewer systems are typically built with some room to treat higher flows of wastewater, which can happen when it rains or snows more than usual and that extra water seeps into the wastewater collection system.

The City of Salem’s wastewater system serves more than 60 square miles through over 800 miles of pipe and includes the cities of Turner and Keizer. The wastewater system treats an average of 30 million gallons per day in summer months and a peak of 200 million gallons per day in winter months when both Willow Lake Wastewater Pollution Control Facility and the City’s back up facility at River Road Park are in use.

What is a Sanitary Sewer Overflow?

Sanitary sewer overflows can occur when wastewater escapes from the sanitary sewer collection system, before treatment at Willow Lake, releasing raw sewage into the environment.

There are two main reasons why a release like this may occur.

  • Pipes that carry wastewater are clogged with fats, oils, grease, wet wipes, other debris, or tree roots. The clogs cause wastewater (before treatment) to back up and spill onto the ground.

  • Too much stormwater seeps into the wastewater pipes through broken pipes, cracks in the pipes, or faulty seals. Heavy rainstorms and many days of rain are causes of stormwater seeping into the wastewater collection system. The amount of water in the water in the system can be too much for the wastewater treatment plant to handle, causing spills or emergency discharges of untreated wastewater into the Willamette River.

Preventing Overflows of Sanitary Sewer System

The City of Salem has a robust program to reduce the amount of sanitary sewer overflows that occur. We work to prevent sewer overflows by regularly vacuum cleaning, inspecting, and grouting the more than 800 miles of sanitary sewer lines within the cities of Salem, Keizer, and Turner to avoid clogs and to reduce the amount of stormwater that enters the City’s sewer pipes.

Monitoring During Wet Weather

During the wet weather months, crews carefully and continuously monitor the wastewater collection system. When a storm event is expected to occur that may overload the sanitary sewer system, crews are on standby.  Crews monitor how the sanitary sewer system is filling so that they can avoid releasing untreated wastewater into the Willamette River.

Crews monitor Willow Lake Pollution Control Facility, the backup wastewater facility, and over 30 sewer pump stations around the City.


The City regularly checks the aging of lines, locates defects in the pipes and issues them for repair, discovers damage caused by directional boring and other construction activity, and inspects the quality of new pipe with closed circuit video. Two trucks run on battery and solar power to inspect the more than 800 lineal miles of sanitary sewer lines.  Each truck can video inspect up to 1200 lineal feet of pipe, from six inches in diameter up to 42 inches in diameter on a self-propelled transporter. Larger diameter lines up to 72 inches in diameter can also be inspected.


High-pressure cleaning scours silt, rocks, and other debris from the bottom of the pipes as well as blasts grease build up from the pipe walls. The City has four hydro/vacuum combination trucks to clean the sanitary sewer lines out to distances up to 1000’ lineal feet. Once cleaned, the materials are vacuumed out of the system for disposal at the waste processing facility.


The City seals void, crack, and joint defects in pipes to stop stormwater from getting into the sanitary sewer system. The City has one grout truck that checks lines that have leaking joints and cracks. Grouting of these issues prevents stormwater from entering the wastewater collection pipes.

Pipe Replacement:

Sometimes larger maintenance or pipe replacement projects are required.  These projects are featured in the City’s five-year Capital Improvement Plan.

How You Can Help Reduce Overflows

Everyone can do their part to prevent wastewater or sanitary sewer backups and overflows.

National Pollutant Discharge Elimination System (NPDES) Permit for Wastewater Treatment 

The City of Salem owns and operates a complex wastewater treatment facility located in Keizer, Oregon. Domestic, commercial, and industrial wastewater is treated and discharged to the Willamette River in accordance with National Pollutant Discharge Elimination System (NPDES) Permit. This permit is a joint federal and state permit and subject to federal and state regulations. The Clean Water Act, the Code of Federal Regulations, and numerous guidelines of the Environmental Protection Agency (EPA) provide the federal permit requirements. The Oregon Revised Statutes, Oregon Administrative Rules, and policies and guidelines of the Department of Environmental Quality (Department) provide the State permitting requirements.

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