Volume 26, Number 2 February 23, 2018

Working in Maryland Streams?
Be Aware of Time of Year Restrictions!

Unnamed Perennial Tributary to Muddy Branch in Malcolm King Park, Gaithersburg, MD

Every waterway in Maryland is protected by restrictions on instream work – these Time of Year Restrictions (TOYR) help minimize impacts to aquatic habitats during construction projects.  The Maryland Department of the Environment (MDE) enforces restrictions by routinely visiting job sites to ensure contractors are not working in streams during restricted times of year, and will shut down those projects that are in violation.  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 Maryland state wetland permit identifies the streams on your project site, and lists the restrictions that apply to that site.  Wetland Studies and Solutions 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.

Note that the Stream Use Classification III TOYR for nontidal cold water is currently in effect until April 30.  These streams are generally located in western Maryland, northern Montgomery County, Howard County, Carroll County, and Baltimore County.  Classification I TOYR for Nontidal Streams and IV TOYR for Recreational Trout Waters both begin March 1.  We addressed the Use III waterways in our September 2017 Field Notes.

What are the Maryland Stream Use Classifications?

Maryland waterways are divided into four main Stream Use Classifications: 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.

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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 instream activities are prohibited during TOYR?

Time of year restrictions apply to any temporary or permanent activity that disturbs stream channels, including but not limited to culvert installations, utility line crossings, stream diversions, and stream restoration activities. 

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.

If you have questions about your Maryland state wetland permit, or need clarification on the Stream Use Classification or TOYR for streams on your project site – our Maryland Environmental Scientists can help!  If you need to continue instream work past the start of the TOYR period for your project, please contact Mike Klebasko or Ken Wallis in our Maryland office as soon as possible. 

Check out past issues in the Field Notes Archive.


  • Mike Klebasko

    Millersville, MD