Maintenance and Inspection of Stormwater Best Management Practices

August 31, 2020
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A dry pond sand filter, a type of stormwater BMP.

Did you know there are more than 17,000 Stormwater Best Management Practices (BMPs) in Montgomery County? These stormwater BMPs protect rivers, streams and ultimately the Chesapeake Bay!

Stormwater BMPs are designed to help reduce water pollution and protect stream habitat. How do they function? Stormwater BMPs reduce or eliminate pollution that washes off surrounding lands before the runoff reaches local streams. They protect our rivers and streams by slowing down the rainwater and filtering pollutants. In addition, stormwater BMPs provide habitat by using native plants that are good for pollinators! Believe it or not, stormwater BMPs come in all sizes and shapes. They can be small, such as dry wells, cisterns and rain gardens, to very large like ponds. See our previous blog about Stormwater Best Management Practices for more information.



Permeable pavers, a type of stormwater BMP, at a commercial property.


A bioretention stormwater BMP at a commercial property.

In order to ensure that stormwater BMPs are working appropriately, routine inspections and maintenance occur year-round by Montgomery County’s Department of Environmental Protection (DEP) and it’s contractors. DEP conducts these routine inspections to ensure that all stormwater facilities are in good working condition and are being adequately maintained. Properly functioning stormwater BMPs protect infrastructure and public safety while reducing pollutants in streams.  Additionally, these efforts are required by State and County law.

Stormwater BMPs may be owned by the County, a Homeowners’ Association, a commercial business or even a homeowner! They can be found at schools, hospitals, parks, and even on rooftops.

Regardless of who owns the stormwater BMP, they are inspected at least once every three years by DEP staff and contractors managed by DEP. Inspections are key because they help identify required repairs or additional maintenance needs that can be costly if not addressed early.

Inspections Cycle

To inspect all stormwater BMPs, the County is divided into three regions. Each region contains up to 3,900 stormwater BMPs. Although Inspections are done every year, each region is inspected every three years on a rolling schedule. For example, looking at the blue area on the map below. If stormwater BMPs were inspected in 2020 in the blue area, the next time those stormwater BMPs would be inspected would be in 2024.


Permeable pavers being cleaned by a contractor.

Maintenance of the stormwater BMPs is performed by either a DEP contractor (County owned and maintained BMPs) or the private property owner, such as a Homeowners Association, commercial property owner, or single-family residential homeowner.

  • Annual maintenance is required to ensure the stormwater BMPs are working appropriately and continue to protect local streams and rivers. The type of stormwater BMP dictates the type of annual maintenance.
  • Regular maintenance can include removal of sediment and litter (dirt and litter flows to BMPs during rain events), replacing vegetation, pruning, and mowing any grass coverings. This type of non-structural maintenance is typically the responsibility of the property owner.
  • The need for Major Stormwater BMPs structural maintenance, such as pipes, concrete, and underground structures, may be discovered during the inspections.  Sometimes the structural maintenance project will retrofit an existing design of the stormwater BMP to improve its stormwater treatment.

The Montgomery County Department of Environmental Protection has a wealth of information on our website:

  • Find fact sheets for annual and seasonal maintenance for all types of stormwater BMPS here.
  • More information about major stormwater BMPs structural maintenance can be found here.

A bioretention stormwater BMP at a congregation parking lot.

Why is it Important to Maintain Stormwater BMPs?

An unmaintained stormwater BMP may cause rainwater to pool on the surface and become a breeding place for mosquitos, stop filtering the rainwater and allow the pollutants to enter our local streams or block the flow of water and cause local flooding.

By maintaining stormwater BMPs, all property owners are doing their part to help the environment and protect local streams, the Potomac River and the Chesapeake Bay.

Potomac River by Great Falls Tavern in Montgomery County, MD.

Helpful websites:

  • Learn more, including whether there is a stormwater BMP on your property, and how to maintain them, visit our website.
  • Have a stormwater BMP in your yard? Did you apply for a Water Quality Protection Charge credit?  Learn more here.


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