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 signed the MOU with the Cruise Lines International Association North West & Canada (CLIA-NWC) and the Port of Seattle on April 20, 2004.

The agreement:

  • Bans wastewater discharges to Washington state waters from all cruise ships
    • Except discharges treated with advanced wastewater treatment systems (AWTS).
  • Allows us to inspect the wastewater treatment systems on each vessel.
  • Requires cruise lines to sample and monitor wastewater discharges from their ships.

Every three years, the MOU parties consider public amendment proposals to update the MOU. We are accepting proposals until Dec. 18, 2020. To propose an amendment please see the criteria and more information below.


See a problem?

  • Immediately report MOU non-compliance to: 425-649-7000 (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 only cruise lines that are members of the CLIA-NWC. 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. 

Annual meeting

Each year, we meet with the CLIA-NWC 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 and we publicize it. The annual meeting for the 2019 season was held on May 14, 2020. During the 2018 season annual meeting, we presented on an evaluation of water discharges from exhaust gas cleaning systems installed on many of the MOU cruise ships.

Call for proposed amendments to the MOU

Every three years, the MOU parties consider public amendment proposals to update the agreement. We are accepting amendment proposals through Dec. 18, 2020

After the close of the proposal period Ecology and the signatories will review the comments, amendments that meet the criteria will be posted for a 30-day public comment period (around mid-February). At the end of the comment period, MOU signatories will review the comments and meet to decide which, if any, of the proposed amendments should be adopted. In order for an amendment to be adopted, it must receive unanimous approval from the MOU signatories.

Amendment criteria

We are seeking amendments that address only cruise ship activity within the boundaries of the MOU and do not duplicate or replace existing regulations. However, proposed changes can be more stringent.

Proposed amendments must include: 

  • The basis for the amendment (e.g., what environmental concern it addresses within the scope of the MOU).
  • How the amendment is applicable to or compatible with the MOU.
  • The anticipated benefits of the amendment.
  • Potential impacts of the amendment.
  • Include scientific data that supports the proposed amendment as applicable

You can find the full process for amending the MOU in the current MOU document item no. 10.

How to submit proposals

Please submit proposals to:  (email preferred) or

mail to:

Evan Dobrowski
Department of Ecology
Water Quality Program
3190 160th Ave SE
Bellevue, WA 98008

Previous cruise season reports