Stormwater BMP Maintenance

Did you know that the pond in your commercial development and the ditch planted with native grasses and flowers on your street are tools for managing stormwater?

These structures are called stormwater best management practices (BMPs) because they are designed to mitigate flooding and in some cases stormwater pollution. Stormwater BMPs make it possible to live in our developed and paved environment that limits the ability of water to infiltrate into the ground or be absorbed by natural vegetation.

If BMPs are improperly maintained, they can become a pollutant source or be limited in their ability to store stormwater. Other benefits of BMPs may be limited too, such as their aesthetic appeal or capacity to be urban habitat. If maintenance is deferred, issues can compound and more expensive and time consuming repair and maintenance may be necessary.

Fortunately, proper and regular maintenance can help reduce costs and keep BMPs functioning optimally. Read on to learn more about stormwater BMPs as well as best practices for maintaining them.

Who is Responsible for Maintaining a Stormwater Best Management Practice?

If a stormwater BMP is on private property, the owner of the BMP is responsible for seeing that the BMP is maintained. The owner might be legally obligated to see that this maintenance is occurring if they have a Long Term Maintenance Agreement, or LTMA, with a unit of government such as a city or county. A LTMA will have specific terms for the maintenance of the BMP, some of which may include:

A maintenance schedule
Responsible party(s) or organization responsible for maintenance
Authorization for municipal staff to access the property to inspect the BMP for maintenance activities
A process for reporting maintenance activities

Do you have a structure on or near your property that you think might be a stormwater BMP? Even if you did not establish the agreement, it may be registered as a property deed restriction, and as the current owner of the property you are legally obligated to ensure that the BMP is being maintained. You can find out if you have a deed restriction by contacting your county or municipal clerk.

How are Stormwater Best Management Practices Maintained?

There are many different types of stormwater BMPs, and for each type, there are a variety of tasks to be regularly and occasionally completed to ensure that they are functioning correctly. If the BMP is under a LTMA, there may be a specific suite of tasks that the landowner or operator are required to complete, and this may be included in a stormwater maintenance plan. Even property owners who have a maintenance agreement or contract with another entity should be knowledgable about the maintenance needs of their BMPs.

Wisconsin Department of Natural Resources has developed standards for maintaining certain BMPs that are based on current research, field experience, and the best available technology. You can find these technical standards on WDNR’s website, and some of the more everyday tasks that they have published are included below. These should not be taken as explicit instructions for maintaining your BMP, but to give you an idea of the tasks that you should be completing in order to maintain your structure.

Who is responsible for stormwater BMP maintenance?

How do I know if I have an LTMA?

What are some common maintenance tasks for BMPs?

Bioretention Devices

Description: An excavated area that has been partially filled with a soil mixture engineered for optimal infiltration, then covered with mulch and planted. Stormwater percolates through the soil and is treated by a variety of physical, chemical, and biological processes before it infiltrates into the native soil.

Typical Maintenance Activities Include:

Watering plants
Re-mulching
Treating diseased trees and shrubs
Removing liter and debris

See full WDNR Technical Standard - Bioretention

Infiltration Basin

Description: An excavated area greater than 15 feet wide at the narrowest point with a flat, vegetated floor dedicated to the infiltration of runoff.

Typical Maintenance Activities Include:

Mowing plants to specific heights
Controlled burning on specific schedules

See full WDNR Technical Standard - Infiltration

Wet Detention Ponds

Description: A permanent pool of water constructed to collect, detain, treat, and release stormwater runoff.

Typical Maintenance Activities Include:

Measuring and removing sediment from the pond
Clearing embankments of woody vegetation
Removing weeds and algae

See full WDNR Technical Standard - Wet Detention Pond

Permeable Pavement

Description: A pavement system that allows movement of stormwater through the pavement surface and into a base/subbase reservoir. Examples include pervious concrete, porous asphalt and permeable pavers/blocks.

Typical Maintenance Activities Include: