Unnamed Maryland perennial tributary

Every waterway in Maryland is protected by restrictions on instream work to help minimize impacts to aquatic habitats during construction projects. The Time of Year Restrictions (TOYRs) for Use I (Nontidal Streams) and Use IV (Recreational Trout Waters) streams both begin March 1 and extend until June 15 and May 31, respectively. The Maryland Department of the Environment (MDE) enforces these restrictions by routinely visiting job sites, and will shut down those projects that are in violation.

Note that the TOYR for Use III (Nontidal Cold Water) streams is currently in effect until April 30 – see our recent Field Notes for more information about Use III TOYR.

You can avoid violations and project delays by being aware of the Maryland Stream Use Classification for streams on your project sites prior to construction, and by planning any instream work around the TOYR period. Your MDE wetland permit identifies the TOYR restriction that applies to your project, and Wetland Studies and Solutions, Inc. staff can help you:

  • Identify the stream use classification for streams on your current and future projects
  • Determine which TOYR applies to your projects
  • Plan your construction activities around the Maryland Stream TOYR
  • Submit a written request to MDE to continue work past the start of a TOYR period

WSSI Can Help

If you have questions about your Maryland state wetland permit, need clarification on the Stream Use Classification or TOYR for streams on your project site, or need to continue instream work past the start of the TOYR period for your project, please contact Mike Klebasko, Haley Kelly, or Scott Petrey in our Maryland office.

What are the Maryland Stream Use Classifications?

Maryland waterways are divided into four main Stream Classification Uses: Nontidal Streams, Tidal Waters, Nontidal Cold Water, and Recreational Trout Waters. Maryland ArcGIS provides a map that identifies the classification of every Maryland waterway here.

Stream Use Classification Stream Type Instream Work Prohibited From
I Nontidal Streams March 1 – June 15
II Tidal Waters Variable depending on species present
III Nontidal Cold Water (Naturally Reproducing Trout Streams) October 1 – April 30
IV Recreational Trout Waters (Stocked Trout Streams) March 1 – May 31


What actions can I take to work around TOYR periods?

To accommodate the Maryland instream restrictions, you can either completely avoid construction during the TOYR periods, or you can prepare for the TOYR by taking incremental steps to ensure that your project can progress throughout the TOYR. For example, if you properly install stream diversions prior to the start of the instream restriction period, you can continue work in the original stream channel during the TOYR period. Similarly, if you install and stabilize a road culvert prior to the TOYR, you can continue work on the road crossing during the TOYR – provided the work occurs outside of the stream channel. We can help identify circumstances where you can prepare for the TOYR by completing certain work prior to the restrictions.

What can I do about projects that are underway but cannot be completed prior to the instream TOYR period?

If you cannot avoid instream work during a TOYR, you must submit a written request to MDE prior to the start of the restriction period justifying the need to continue work. If approved, MDE typically allows only a few extra days to complete an activity and will not grant permission for extended work into the TOYR period. MDE also will not allow instream work to begin prior to the end of the restriction period.


  • Mike Klebasko

    Millersville, MD

  • Haley Kelly

    Millersville, MD

  • Scott Petrey

    Millersville, MD