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.

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.

Every three years, the MOU parties consider public amendment proposals to update the MOU. The most recent call for proposed amendments ended on December 18, 2020.  The MOU parties had 45 days to review the amendments to verify they met the requirements for further review and then open proposed amendments  for a 30-day public comment period.

Proposed MOU amendments open for public comment 

We are accepting comments from Feb. 17 until March 19, 2021. 

To comment on the proposed amendments please see the  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.

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Proposed MOU amendments open for public comment 

 We are accepting comments from Feb. 17 until March 19, 2021. 

Proposed MOU amendments:

  1. Institute a ban on the discharge of exhaust gas scrubber washwater from all scrubber types, including bleed off or sludges, in MOU waters.

This proposed MOU amendment met the criteria as it was specific to the MOU waters and was accompanied by scientific data to support the amendment. However, if adopted, some of the wording of this amendment is likely to change to conform with regulations under the MARPOL treaty regarding exhaust gas scrubber washwater.

  1. Ecology proposes to incorporate the Vessel Sewage No Discharge Zone (NDZ) for Puget Sound into the MOU to reflect the Washington state NDZ regulation. Chapter 173-228 Washington Administrative Code (WAC), adopted on April 9, 2018, and effective May 10, 2018. As written, the MOU allows for treated sewage (blackwater) discharges after advanced wastewater treatment that are now not allowed by the NDZ regulation. To be consistent with the regulation and to prevent vessel sewage discharges in MOU waters, allowances of sewage discharges in MOU waters should be prohibited. This would not affect graywater discharge in the MOU.

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

How to submit comments

  • Use our online eComment form. 
  • Mail to: Evan Dobrowski; Department of Ecology; Water Quality Program; 3190 160th Ave SE; Bellevue, WA 98008.

Previous cruise season reports