Cruise ships in Washington waters

A voluntary agreement, called a memorandum of understanding (MOU), helps prevent wastewater discharges from large cruise ships into state waters. We first signed the MOU with the Cruise Lines International Association North West & Canada (CLIA-NWC) and the Port of Seattle in 2004. In the 2023 MOU updates, CLIA was removed as a signitory and member cruise lines were added. The member cruise lines pay for this program.

The waters subject to the MOU include Puget Sound and the Strait of Juan de Fuca south of the international boundary with Canada; along Washington’s Pacific Coast extending three miles seaward; and the Olympic Coast National Marine Sanctuary.  

Cruise vessel sailing

Cruise vessel sail from Elliott bay.  Photo courtesy - Port of Seattle

The agreement:

  • Bans wastewater discharges to Washington state waters from all cruise ships
    • Except discharges treated with advanced wastewater treatment systems (AWTS) and outside Puget Sound No Discharge Zone.
  • Allows us to inspect the wastewater treatment systems on each vessel.
  • Requires cruise lines to sample and monitor wastewater discharges from their ships.                               

See a problem?

  • Immediately report MOU non-compliance to: 206-594-0000 (available 24 hours a day).
  • Immediately report “upset of disinfection" to Washington State Department of Health at 360-236-3330 (8 a.m. to 5 p.m.) or 360-786-4183 (after hours).

Cruise liners help protect Washington's marine waters

The MOU prohibits cruise ships from discharging blackwater (from toilets) and graywater (from sinks and showers) to Washington waters, unless the discharges are treated with advanced wastewater treatment systems (AWTS) and outside the Puget Sound No Discharge Zone.

Who does the agreement cover?

The agreement covers the brands owned and operated by the cruise companies that signed the agreement. This means the MOU does not cover all vessels that carry paying passengers. The following vessels types are not covered:

  • Non CLIA-NWC member line smaller passenger ships or boats carrying less than 249 passengers.
  • Washington state ferries (state ferries pump their sewage to on-shore treatment plants)
  • Alaska Marine Highway ferries
  • Large cargo ships, which are subject to EPA’s Vessel General Permit.

Requirements for cruise ships

Ships that opt to legally discharge via an AWTS must meet other stringent requirements, including:

  • Advanced notification and documentation from ships planning to discharge via AWTS
  • No discharges within a half mile of shellfish beds or within the Puget Sound No Discharge Zone
  • Limits on certain pollutants, with specific sampling, testing, and reporting requirements
  • Continuous monitoring for turbidity (murkiness) and disinfection
  • Disinfection of all discharges, with capability to shut down immediately

Area covered by the agreement

The agreement applies to Washington marine waters, including:

  • All waters south and east of the Canadian border
  • Ocean waters up to three miles from shore
  • Olympic Coast National Marine Sanctuary

Almost all cruise lines have opted to not discharge any sewage or graywater while in Washington waters covered by the MOU. Since 2012, every CLIA-NWC vessel in Washington has followed this practice.


Each year the cruise lines must send us an annual report on their ships' wastewater practices. The MOU allows us to inspect each vessel's wastewater records and equipment to verify compliance. The MOU also allows us to complete random onboard equipment and records inspections on an annual basis. 

Ongoing studies 

Exhaust Gas Cleaning Systems (EGCS) are used on many cruise ships to comply with international air quality requirements limiting sulfur as an alternative to low sulfur fuels. EGCS’ are air pollution control systems that intake sea water to clean the exhaust systems resulting in washwater discharges. Ecology did an initial evaluation of EGCS washwater systems in 2018. The MOU partners agreed to further study EGCS washwater studies and their impacts in Puget Sound. The Puget Sound Exhaust Gas Cleaning System EGCS Washwater Ecological Risk Assessment, led by Oregon State University and EcoAnalysts is currently underway with expected results in 2024.

Annual meeting

Each year, we meet with the cruise companies and the Port of Seattle to review the past cruise season and consider ways to strengthen the agreement. This meeting is open to the public. Partners consider amendments to the agreement every three years. All parties must agree in order to amend the MOU. 

Public webinar

We are hosting a public webinar on the Cruise Ship Memorandum of Understanding on Monday, May 6,  2024 at 10.a.m.

Please, register in advance. After registering, you will receive a confirmation email with details on how to join the webinar.

Stay informed

If you like to receive notifications about the MOU, join our email list                           

Previous cruise season reports