Nutrient pollution continues to harm Puget Sound, leading to low-oxygen zones that threaten fish and animals. As the population of Western Washington grows, the combined burden of millions of toilets and thousands of acres of lawns and farms overload the Sound with more nutrients than it can handle, causing a series of events that leads to low oxygen levels.

Ecology has drafted the Puget Sound Nutrient Reduction Plan to guide the region as it seeks to address the many human sources of nutrient pollution.

When an estuary like Puget Sound suffers from low oxygen, it alters the marine food web in ways that impact endangered salmon and orca. This includes increases in algae blooms, jellyfish smacks, and fish kills. Low oxygen levels can also lead to reduced feeding, slower growth, and potential negative effects on the reproductive and immune systems of aquatic life. Low oxygen in marine waters leads to more acidic waters, making it more difficult for shellfish to form shells and can mean less plankton for forage fish to eat.

To create this plan, Ecology held more than 20 public Puget Sound Nutrient Forum meetings starting in 2017 to review the science, present data, take feedback on approaches to clean water, and hear from regional and national experts on solutions to nutrient pollution. The plan highlights the need to reduce the amount of nitrogen in wastewater, invest in wastewater treatment plant upgrades, and address other sources of excess nutrients.

David Giglio, who manages Ecology’s Water Quality Program, said the plan is an essential component of the broader efforts to restore Puget Sound.

“This draft plan is a way to continue conversations on the region-wide work needed to tackle nutrient pollution and support Puget Sound recovery,” Giglio said. “We are proposing a suite of actions between now and 2050 to improve the oxygen levels in Puget Sound, and we invite everyone to help us chart this path to cleaner water.”

Nutrient pollution is one of the water quality threats facing Puget Sound. Ecology has outlined a long-term path to reduce nutrient pollution, recognizing the need to prioritize and plan these investments.

Taking action on nutrient pollution

Nutrients such as nitrogen and organic carbon are an important part of a healthy marine ecosystem. But too much of these nutrients can cause serious problems. Washington is not alone; nutrients are a problem in many communities across the country.

The largest source of excess nitrogen in Puget Sound is human urine. Unless a wastewater treatment plant has nutrient reduction controls in place, that nitrogen can enter the Sound and cause water quality problems. Ecology estimates facilities that discharge directly into Puget Sound contribute approximately two-thirds of the excess nitrogen. Excess nitrogen can come from other sources as well, including fertilizers and leaking septic systems.

As the region’s population continues to grow and the amount of nitrogen continues to increase, it overwhelms the natural balance in Puget Sound by causing excess plant and algae growth. As plants and algae die and decompose, they use up oxygen that is critical to aquatic life. At certain times of the year, parts of the Sound don't have enough oxygen for fish and other aquatic life to survive and thrive. Under the Clean Water Act, Ecology has a responsibility to address the sources of nutrient pollution to improve the health of Puget Sound.

The draft plan outlines actions for cleaner water by 2050, including:

• Update water quality permits to reduce the amount of nitrogen coming from wastewater and industrial facilities.
• Establish water clean-up plans for watersheds that flow into Puget Sound.
• Monitor water quality data to track the plan’s progress for decades to come.

The science behind the plan

The draft plan uses scientific modeling to forecast how different amounts of nitrogen from sources throughout Puget Sound impact oxygen levels in the water. Called the Salish Sea Model, this tool allows everyone to see how different actions can improve water quality.

“Communities are faced with controlling and cleaning up many types of pollution. When it comes to nutrient pollution, there are proven ways to solve the problem, and we will need to use all our tools to get to clean water,” Giglio said. “This includes significant investments for wastewater infrastructure. As a region, we need to be as efficient as possible with our resources while we work toward a healthy Puget Sound and restoring salmon runs.”

As Ecology developed the draft plan, the agency looked at different modeling scenarios to find the mix of nutrient reductions that would restore healthy oxygen levels. Ecology’s modeling efforts indicate that communities surrounding Hood Canal and the straits of Georgia and Juan de Fuca — and the very small municipal wastewater treatment plants that discharge throughout the Sound — may not need the same nutrient control technologies as facilities serving other parts of the region.

Ecology plans to convene a technical advisory committee to guide its approach to developing numeric nitrogen limits and incorporating them into future permit updates. More information on approaches to developing future permit requirements and the technical advisory committee is available as part of the draft plan.

Provide input and join our meetings

Ecology is accepting public comments on the draft plan from 8 a.m. June 12 to 11:59 p.m. Aug. 27, 2025. The draft plan, supporting materials, and information on how to comment is available on Ecology’s Reducing Nutrients webpage.

The agency welcomes feedback on the entirety of the draft plan, including the targets set by the plan and draft milestones, ideas on other nutrient reduction scenarios that could meet state water quality goals, how model outputs are evaluated and used, and any other innovative ideas to address impairments and meet water quality standards.

There are multiple opportunities to learn more about the draft plan, each with question-and-answer sessions. The details for a virtual meeting are below. The agency will hold in-person meetings later this summer and announce those meetings on the Nutrient Forum email list. Ecology is planning to hold one meeting in the North Sound area and one in the South Sound area.

Virtual meeting

• June 24 at 1 p.m.
• Register on Zoom.