.04-1 Antidegradation Policy Implementation Procedures: Tier I Level of Protection — Existing Uses and Designated Uses.

A. All waters of the State shall receive Tier I protection which requires the protection and maintenance of existing uses and designated uses.

B. Protections. Waters that have demonstrated an existing use that is not protected by the water quality criteria specified for the current designated use for this water body shall be protected so as to maintain the existing use and the water quality necessary to protect the existing use.​

C. Implementation of the Tier I level of Protection for Cold Water Existing Uses. The determination and protection of cold water existing uses in Maryland will be implemented according to the "Cold Water Existing Use Determinations: Policy and Procedures (Maryland Department of the Environment, May 12, 2021)", which is incorporated by reference.

D. Compilation and Maintenance of the List of Waters with Existing Uses. The Department shall compile and maintain, on its website, a public list of the waters with an existing use that is not protected by the currently designated use and associated water quality criteria. ​