Volume 25, Number 2 February 6, 2017

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

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

Instream work restrictions apply to every waterway in Maryland. For most streams within Central and Southern Maryland, as well as the Eastern Shore, instream construction activities are prohibited by the Maryland Department of the Environment (MDE) between March 1 and June 15 of any year. However, note that if you are working in a Nontidal Cold Water (Class III), the restriction starts on October 1, and Class II waters have restrictions that vary with species presence. MDE inspectors will visit job sites to ensure that instream work is not occurring during the restriction period, and will shut down work on those projects that are in violation. Avoid costly delays by planning your instream work around the restriction period.  Before beginning construction, be aware of your stream use classification and associated time of year restriction (TOYR) period, which is listed as a condition on your state wetland permit.  If you are unsure of your stream use classification or TOYR period, please contact Mike Klebasko, Ken Wallis, or Dan Lucey in our Maryland office for more information.

What are the stream use classifications and instream TOYR?

Maryland waterways are divided into four main use classifications (I, II, III, and IV), and the restrictions vary for each use classification. The instream TOYRs for each of the four stream use classifications are listed in the simplified table below:  

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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

An interactive map highlighting the stream use classifications of every waterway in Maryland can be found here. Please note that if your project impacts a Use III waterway (generally located in western Maryland, northern Montgomery County, Howard County, Carroll County, and Baltimore County), the instream TOYR is currently in effect until April 30; WSSI addressed the Use III waterways in our September 2016 Field Notes.

Which instream activities do these restrictions apply to?

These restrictions apply to culvert installations, utility line crossings, stream diversions, stream restoration activities and any other temporary or permanent activity that disturbs stream channels.  If stream diversions are properly installed prior to the start of the instream restriction period, then work may continue in the original stream channel during that TOYR period.  Also, if a road culvert is installed and stabilized prior to the stream restriction period, work may continue on the road crossing provided the work occurs outside of the stream channel.  

What if your work cannot be completed prior to the start of the instream TOYR period?

A written request justifying the need to continue in-stream work during the restriction period must be submitted to MDE prior to the start of the restriction period.  If approved, note that MDE typically allows only a few extra days to complete an activity.  Extended incursions into the TOYR period are not granted by MDE, nor will MDE allow instream work to commence prior to the end of the restriction period. Should you need to continue instream work past the start of the TOYR period, 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