Maryland's Surface Water Quality Standards


Maryland's Triennial Review of Water Quality Standards and Regulation Changes 

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 March 11, 2022 issue of the Maryland Register, held a public comment period that ended on April 11, 2022, and held a virtual public hearing on March 30, 2022 to present on the proposed changes. After responding to all submitted comments, MDE finalized the regulation changes as proposed in the October 21, 2022 edition of the Maryland Register and these regulations became active on October 31, 2022. MDE will be submitting the completed Triennial Review to EPA for final approval. 

The regulatory changes and all supporting materials associated with this Triennial Review of Water Quality Standards can be accessed here​.


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 Online to access 26.08.01 and 26.08.02.​

How are changes to water quality standards made?

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 of Water Quality Standards (TR). The TR includes a robust public participation process prior to adoption of new or revised regulations. This process generally includes an Advanced Notice of Public Rule-Making (ANPRM) and solicitation of comments followed later by a more formal public comment period during which a hearing takes place (the formal comment period and hearing are required). Comments are incorporated and/or responded to in what becomes a public document as part of the TR package that EPA reviews. To see materials from Maryland's past Triennial Review actions please click here

Current Work

Contact Information 

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

Last Updated 11/2022​​

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