Maryland's Surface Water Quality Standards

The Public Review Period for Maryland's Proposed Water Quality Standards Regulations

The Clean Water Act (CWA) requires that States review their water quality standards every three years (Triennial Review) and revise the standards as necessary. Consistent with this requirement, MDE published a notice of proposed action in the May 26, 2017 issue of the Maryland Register. This marked the beginning of the public comment period that ended on July 10, 2017 (please note the extension of the public comment period). Stakeholders were invited to comment both on the proposed changes to water quality standards and on other water quality standards of interest. ​A brief summary of the proposed changes can be accessed by clicking here. To see more detail on the proposed changes please click here. After considering and addressing all comments received on this Triennial Review, the final set of regulations will be submitted to the Division of State Documents for promulgation.

MDE held a public hearing at 3pm on June 13th in Baltimore to present on the proposed changes and to answer questions. A recording of that hearing is available by clicking the first link below and the presentation can be accessed through the second link below.  Other materials, relating to the proposed removal of Tier II segments, were requested by attendees of the hearing and are provided as the 3rd, 4th, and 5th bullets below.   

Comments or questions may be directed in writing to Timothy Fox at or alternatively at:

Mr. Timothy Fox
MDE - Water and Science Administration
1800 Washington Blvd
Baltimore, MD 21230


What are water quality standards?

The purpose of water quality standards is to protect, maintain and improve the quality of Maryland surface waters. The following make up the three components of water quality standards:

  • Designated Uses,
  • Water quality criteria, and
  • Antidegradation policy.

What are Designated Uses?

A designated use is a goal for water quality. Typically, the goal is the description of an appropriate intended use by humans and/or aquatic life for a water body. Designated uses for a particular waterbody may include recreation, shellfishing, water supply and/or aquatic life habitat. The designated uses established may or may not be met currently, but must be attainable. In Maryland these designated uses are grouped into "Use Classes" (e.g. Use Class I, I-P, II, III, IV-P) so as to describe a unique combination of designated uses that apply to a single water body. Each stream segment, lake, bay, etc. in Maryland is assigned to a use class.

For more detailed information about Maryland’s designated uses and use class groupings, please click HERE. To go directly to maps of surface waters and their associated use classes, please click HERE.

Water Quality Criteria

  • Numeric criteria set the minimum water quality to meet the designated uses.
  • Maryland has numerous numeric criteria for protection of aquatic life and human health (e.g., 5 milligrams/liter for dissolved oxygen; 82 micrograms/liter for Pb (acute, freshwater)
  • Criteria are published for toxics, dissolved oxygen, turbidity, bacteria, and temperature.
  • Where specific numeric criteria are not available (e.g., oil, grease, odor, nuisance), narrative criteria apply.
  • The Numerical Criteria for Toxic Substances in Surface Waters are provided in the Code of Maryland Regulations (COMAR) Section They can be accessed through the web at:
  • Water Quality Criteria Specific to Designated Uses, are provided in COMAR Section They can be accessed through the web at:


  • Maryland’s antidegradation policy assures that water quality continues to support designated uses.
  • EPA regulations provide for three tiers of protection:
    • Tier 1 specifies the minimum standard that must be met—support of balanced indigenous populations and support of contact recreation—this is often referred to as "fishable-swimmable."
    • Tier 2 protects water that is better than the minimum specified for that designated use. For more information on Maryland's Tier II Antidegradation Policy please click HERE. To go directly to maps of Tier 2 high quality waters, please click HERE
    • Maryland is developing the third Tier of protection (Tier 3) called an Outstanding National Resource Water or ONRW.
  • Maryland's Antidegradation Regulations are provided in COMAR Sections,, and Click on each hyperlink to access that particular section.

Current Water Quality Standards

For the full text of Maryland Water Quality Standards please visit COMAR 26.08.01 and COMAR 26.08.02

Changes to the Water Quality Standards

Changes to the Water Quality Standards are implemented through regulatory changes which are subject to the normal promulgation process.

  • Every three years, the Clean Water Act requires that States review their water quality standards in what is called the Triennial Review.
  • Active public involvement is a clear priority.

On April 2, 2014, the Secretary of the Environment adopted amendments to the water quality standards regulations. These amendments were proposed in the December 13, 2013 edition of the Maryland Register (40:20 Md. R.). Final action on the regulations was published in the April 18 edition of the Maryland Register. Click here: Maryland Register Online. Comments specific to this proposal were received and have been addressed in a comment/response document. To see a list of those waters which had their Use Classes changed in the regulations, please click on the following link.


Contact Information

For more information, please contact Matthew Stover at or at (410) 537-3611.​​​