Wastewater Pollution - Puget Soundkeeper Alliance

Puget Soundkeeper is dedicated to improving regulations and infrastructure to keep wastewater contamination from destroying habitat and impairing our waterways.  Wastewater is used water that is affected by domestic, industrial, and commercial use. Wastewater pollution is a major source of contamination to Puget Sound. 

Many contaminants from industrial processes make their way into wastewater, which is then discharged directly to waterways.  In addition, heavy rains cause combined sewer systems to overflow, dumping raw sewage into rivers, lakes, and the Sound. 

Population growth in the Puget Sound region has placed immense pressure on wastewater treatment systems.  This pressure is expected to intensify with a predicted addition of 1.8 million people by 2050.  With increased population growth, industrial activity, and climate change, strong improvements for wastewater treatment are critical in protecting our waterways. 


Industrial Wastewater

Wastewater from industrial sites is often contaminated with metals, chemicals, petroleum products, and other toxic pollutants that are harmful to waterways, people, and fish.  The Clean Water Act requires any facility that discharges wastewater directly to surface water to have a National Pollutant Discharge Elimination System (NPDES) permit that sets limits for effluent discharge, which is liquid pollutants or sewage being discharged.   These limits are set to protect water quality and aquatic and public health.  Some facilities must have a NPDES permit to discharge to municipal sewer systems or groundwater.  Puget Soundkeeper tracks NPDES permit compliance in the Puget Sound region, advocates for strong permit requirements to protect local waterways, and files lawsuits under the Clean Water Act when needed to stop pollution from entering our waterways. 

Puget Soundkeeper’s Clean Water Act Legal Work 

Washington State Department of Ecology Industrial Wastewater Permit page 


Municipal Wastewater

Municipal wastewater treatment facilities, or sewage treatment plants, receive domestic sewage and wastewater from cities, towns, and municipalities.  These facilities are required to treat their wastewater to meet quality standards before discharging it to waterways.  These standards are stipulated in NPDES permits, which also includes benchmarks for how clean the treated wastewater discharge must be.   

Many municipal wastewater systems are challenged by population growth and infrastructure limitations.  Additionally, climate change is impacting our icepacks, stream flows, and storm patterns, adding more pressure on these aging systems.  Further, combined sewer systems – like those in Seattle and King County – which carry both sewage and stormwater runoff, often overflow during heavy rains.  Known as combined sewer overflows, or CSO, these events send raw sewage and stormwater directly into nearby waterways.  Even separated sewers can overflow when stressed. 

Many sewage treatment plants also receive industrial wastewater.  Since municipal sewage treatment facilities are not equipped to deal with the heavy contamination that can result from industrial operations, these treatment facilities must set up a pretreatment agreement requiring the industrial operation to eliminate certain contaminants at the source, prior to discharging their wastewater to the sewer.  If this process fails at any point, it can result in serious pollution problems. 

Puget Soundkeeper has won legal cases resulting in huge reductions of sewage overflows in Bremerton and the city of Snohomish.  We also monitor and report sewage overflows that we see on patrols

Current Actions

Combined Sewer Overflows (CSOs)

In 2013, King County and the City of Seattle entered into settlement agreements, called Consent Decrees, with the Environmental Protection Agency (EPA) due to years of Clean Water Act violations.  For decades, these municipalities discharged raw sewage into Puget Sound and nearby waterways from their combined sewer systems.  King County and the City of Seattle are required to control their combined sewer overflows, or CSOs, by 2025 and 2030, respectively.  Each municipality prepared a plan to limit their CSOs to one overflow, per outfall, per year.  To meet this limit, these municipalities planned projects to separate parts of the combined sewer, to add additional storage capacity to the system, and to build new treatment facilities to control their CSOs.   

Puget Soundkeeper participates in Seattle and King County’s Long-Term Control Plan Update processes to track ongoing progress, and to ensure that projects are designed and implemented in an equitable and scientifically sound manner.   We educate the public about CSOs, investigate CSO events, and advocate for strong, science-based solutions when there are major CSOs harming our waterways. 

Municipal Wastewater Treatment Plants and the General Nutrients Permit 

In 2017, Puget Soundkeeper began participating in a stakeholder group led by the Department of Ecology (Ecology) called the Puget Sound Nutrient Forum to discuss the growing issue of nitrogen pollution.  Ecology determined that Puget Sound is impaired by dissolved oxygen as a result of excess nutrients being discharged into the Sound by human activities, such as increased development, increased use of fertilizers, deforestation, and loss of habitat.  However, the State of Washington does not currently have a water quality standard set for nitrogen – apart from being identified as a harmful and widespread pollutant in our waterways. 

While nitrogen is a naturally occurring nutrient that can be used as a fertilizer, in excessive amounts, it can cause harmful algal and plankton blooms that reduce the amount of dissolved oxygen, or D.O. in our waters.  Low levels of D.O. can cause fish kills and dead zones.  The Sound is already experiencing dead zones in some areas as a result of low D.O. and excessive nutrients.  If left unaddressed, we could experience more dire consequences throughout the Sound as climate change and population growth increase the quantities and concentrations of nitrogen discharged to our waters.  

Years of research and scientific data confirm that municipal sewage treatment plants are the biggest human source of Puget Sound’s nitrogen problem.   While the technology needed to control nitrogen pollution at our municipal wastewater treatment plants has been known for years, contributing factors that include pet waste, residential stormwater, and agricultural pollution must also be addressed.     

In 2020, Puget Soundkeeper joined an Advisory Group to assist Ecology with the development of a new Clean Water Act General Nutrients Permit for municipal treatment plants that discharge to Puget Sound.  We are deeply engaged in this process and advocate for the strongest possible water quality protections to stop nitrogen pollution from impairing Puget Sound. 

National Pretreatment Program 

Municipal Wastewater Overview 

The Puget Sound Nutrient Reduction Project 

King County’s CSO Webpage 

Seattle’s Sewage Overflow Prevention Webpage