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Water: Vessel Water Discharge

No Discharge Zones (NDZs)

The Clean Water Act (CWA) is the centerpiece of Federal legislation addressing pollution in U.S. waters.  Under section 312 of the CWA, vessel sewage may be controlled through the establishment of areas in which discharges of sewage from vessels are not allowed.  These areas are also known as "no discharge zones."

What is a no discharge zone for vessel sewage?

A no discharge zone (NDZ) is an area in which both treated and untreated sewage discharges from vessels are prohibited.  Within NDZ boundaries, vessel operators are required to retain their sewage discharges onboard for disposal at sea (beyond three miles from shore) or onshore at a pump-out facility.

How is an area designated as an NDZ under the CWA?

The CWA lists three circumstances where a State may initiate the process to establish an NDZ:

  1. The State determines that the water body requires greater environmental protection, and EPA finds that adequate pump-out facilities are available. (Commonly known as a 312(f)(3) NDZ) A State may completely prohibit the discharge of sewage from vessels, whether the sewage is treated or not, into some or all of its waters if: (1) the State determines that the protection and enhancement of the quality of the waterbody requires greater environmental protection than the current Federal standards allow; and (2) EPA determines that adequate facilities for the safe and sanitary removal and treatment of sewage from vessels are reasonably available. 33 U.S.C. § 1322(f)(3) Exit EPA Disclaimer.
  2. EPA, upon application by the State, determines that the protection and enhancement of the water body requires establishment of an NDZ. (Commonly known as a 312(f)(4)(A) NDZ)  If EPA determines, upon application by a State, that the protection and enhancement of specified waters requires sewage discharges to be prohibited, EPA will, by regulation, completely prohibit the discharge of sewage from vessels, whether the sewage is treated or not, into those waters. Unlike NDZs established pursuant to CWA section 312(f)(3) (described above), the State does not have to show that adequate pump-out facilities are reasonably available to request that this type of NDZ be established 33 U.S.C.1322(f)(4)(A) Exit EPA Disclaimer.
  3. Drinking Water Intake Zones. (Commonly known as a 312(f)(4)(B) NDZ)  EPA, upon application by a State, will, by regulation, prohibit the discharge of sewage from vessels within a drinking water intake zone. The purpose of this NDZ is to safeguard human health through the protection of intake waters used for drinking. The State does not need to show that adequate pump-out facilities  are reasonably available to establish this type of NDZ. 33 U.S.C.1322(f)(4)(B) Exit EPA Disclaimer.

Who enforces the NDZ requirements?

Under section 312 of the CWA, the U.S. Coast Guard and the State in which the NDZ has been designated may enforce the NDZ requirements. 33 U.S.C. 1322(k) Exit EPA Disclaimer.

Which States have NDZs?

A number of States have designated some or all of their surface waters as NDZs.  A list of established NDZs may be found at No Discharge Zones by State.  Maps of established NDZs may be found at Where you Live: Find No Discharge Programs.


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