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Water: Vessel Water Discharge

Marine Sanitation Devices


The Clean Water Act (CWA) is the centerpiece of Federal legislation addressing pollution in U.S. waters.  Under section 312 of the CWA, discharges of sewage from vessels are controlled in part by regulating the equipment that treats or holds the sewage: marine sanitation devices (MSDs).

What is an MSD?

  • For purposes of the CWA, a marine sanitation device is "any equipment for installation on board a vessel which is designed to receive, retain, treat, or discharge sewage, and any process to treat such sewage." 33 U.S.C. 1322(a)(5) Exit EPA Disclaimer.

Who is required to use an MSD?

  • Section 312 of the CWA requires the use of operable, U.S. Coast Guard-certified MSDs onboard vessels that are 1) equipped with installed toilets, and 2) operating on U.S. navigable waters (which include the three mile territorial seas). 33 U.S.C. 1322(h)(4) Exit EPA Disclaimer.
  • The MSD requirements do not apply to vessels that do not have installed toilets (e.g., vessels with "porta-potties").

Who regulates MSDs under section 312?

  • The U.S. Environmental Protection Agency (EPA) and the U.S. Coast Guard jointly regulate MSDs under CWA section 312.
  • EPA has issued regulations setting performance standards for MSDs (the standards address fecal coliform and total suspended solids), and the Coast Guard has issued regulations  Exit EPA Disclaimer governing the design, construction, certification, installation, and operation of MSDs, consistent with EPA's standards.
  • To learn more about the Coast Guard's certification requirements for MSDs, please visit the Coast Guard's website Exit EPA Disclaimer.

Are there different types of MSDs?

Yes, the Coast Guard categorizes MSDs into three types:

Type I Flow-through treatment devices that commonly use maceration and disinfection for the treatment of sewage May be installed only on vessels less than or equal to 65 feet in length

Must produce an effluent with:

  • No visible floating solids
  • A fecal coliform bacterial count not greater than 1000 per 100 milliliters
Type II Flow-through treatment devices that may employ biological treatment and disinfection (some Type II MSDs may use maceration and disinfection) May be installed on vessels of any length

Must produce an effluent with:

  • A fecal coliform bacterial count not greater than 200 per 100 milliliters
  • No more than 150 milligrams of total suspended solids per liter
Type III Typically a holding tank where sewage is stored until it can be disposed of shore-side or at sea (beyond three miles from shore) May be installed on vessels of any length No performance standard, but pursuant to Coast Guard regulations, a Type III MSD must "be designed to prevent the overboard discharge of treated or untreated sewage or any waste derived from sewage".  33 CFR 159.53(c).

What is the role of the States in implementing the CWA section 312 vessel sewage program?

  • Unlike the CWA section 402 National Pollutant Discharge Elimination System (NPDES) program, the States have a more limited role in implementing the section 312 vessel sewage program.
  • Except in the case of houseboats (as defined at CWA section 312(f)(1)(B)), States may not adopt or enforce any statute or regulation with respect to the design, manufacture, installation, or use of any MSD on any vessel subject to the requirements of section 312.  33 U.S.C. 1322(f) Exit EPA Disclaimer.
  • States may, however, request that EPA establish no discharge zones for vessel sewage (areas in which both treated and untreated sewage discharges from vessels are prohibited), or, after required findings are made by EPA, establish such zones themselves.
  • The provisions of section 312 are enforced by the Coast Guard, and may be enforced by the States as well.  33 U.S.C. 1322 (k) Exit EPA Disclaimer.

Are there certain waters where the discharge of treated sewage is prohibited?

  • Yes. Under the CWA and the implementing regulations, vessels are prohibited from discharging any sewage, whether treated by an MSD or not, into the following types of water bodies:    
    • A water body that has been designated as a no discharge zone.
    • Vessels with installed toilets are also prohibited from discharging sewage into freshwater lakes, freshwater reservoirs, or other freshwater impoundments whose entrance point(s) and exit point(s) are too shallow to allow these vessels to enter and leave, and into rivers that do not support interstate traffic by vessels subject to section 312.  See 40 CFR 140.3(a)(1) (PDF) (2 pp, 48K, About PDF)).


EPA received a petition and another separate request (collectively, "rulemaking requests") asking the Agency to revise its MSD performance standards.  The rulemaking petition also requests that EPA establish monitoring, recordkeeping and reporting requirements under the CWA to ensure compliance with the performance standards.

EPA published the following notice in the Federal Register: "Clean Water Act Section 312(b): Notice Seeking Stakeholder Input on Petition and Other Request to Revise the Performance Standards for Marine Sanitation Devices." 75 Fed. Reg. 39863 (July 12, 2010).  In general, the Notice sought public comment on the rulemaking requests and solicited additional technical input and factual information that will be useful to EPA as it considers how it might respond to the requests.  EPA is currently reviewing and considering the comments and information received in response to the Notice.


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