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Infiltration Trenches

An infiltration trenches (also called infiltration areas) is a small trench filled with stone that collects rainwater from paved surfaces such as driveways and allows it to absorb into the surrounding soil. An infiltration area receives rainwater from surface runoff, not underground pipes like a buried dry well.

Infiltration trenches are common on residential lots, where they are typically located next to driveways and at least 20 feet from a building. Their location can be identified by the stone at the surface. Infiltration trenches are often found with sand filters

Image of an infiltration area.


Maintaining Infiltration Trenches

Image of tools that may be needed to maintain a infiltration areas, including a shovel and rake.
Tools for maintaining your infiltration area

As the property owner, you are responsible for all maintenance of your infiltration trench unless a shared maintenance agreement has been made with the DEP Stormwater Facility Maintenance Program.

Infiltration trenches need simple maintenance to keep stormwater flowing into them, such as the removal of sediment, leaves and plant debris from the trench and flow paths. 

An un-maintained infiltration trench may:

  • Cause flooding on other areas of your property if the stormwater is not able to flow into the infiltration area.

  • Require a complete replacement of the facility, which can be very expensive.

By maintaining your infiltration trench, you are doing your part to help the environment and protect your local streams and the Chesapeake Bay.


Image of the front of the Infiltration Area Maintenance Fact Sheet.
Need Help Maintaining Your Infiltration Trench?  
Download the Fact Sheet (PDF, 357KB)



Actions You Can Take to Maintain Your Infiltration Trench
Monthly Actions Seasonal Actions As Needed Actions

✔ Remove sediment and debris that has accumulated on the gravel infiltration area or the flow path to the infiltration area. Even small accumulations of sediment can cause rain water to flow away from the infiltration area.

✔ Remove leaves and tree debris from paved surfaces and the gravel infiltration area surface from April through November. 
✔ Inform contractors working on your property of the infiltration area’s location to prevent accidentally damaging it.
✔ Inspect your infiltration area after storms to make sure that rain water properly drains to and through the infiltration area.  
✔ To prevent damage, be aware of infiltration area locations when doing snow removal.


Actions You Shouldn't Take to Maintain Your Infiltration Trench
✘ Do not remove an infiltration area or expand your driveway over top of the infiltration area.
✘ Don’t place decks, sheds, or other structures above an infiltration area.
✘ Don’t blow grass clippings into the gravel surface of the infiltration area.
✘ Don’t park cars on top of infiltration areas.


DEP can answer your questions and provide additional guidance about maintaining your stormwater facility. Please email or call the Montgomery County Customer Service Center at 3-1-1.


Infiltration Trenches in the Stormwater Facilities Maintenance Program

The Stormwater Facilities Maintenance Program is responsible for maintaining all public stormwater facilities as well as all private facilities that transferred their maintenance to the County.  The program also maintains facilities that were required as part of the Department of Planning permits.

Not sure if your infiltration trench is part of the Stormwater Facilities Maintenance Program?  Check out online Facilities Map or email


Can I remove my Infiltration Trench after installation?

No, you cannot remove any facilities that were part of your building installation - these are permitted structures and DEP maintains a database of these facility locations as part of the Stormwater Facility Maintenance Program. DEP may perform a maintenance inspection of your practice if it is a permitted structure.  Property owners must contact DEP before any major changes can be performed to the structure. 





Resources and Financial Incentives

Have a infiltration trench on your property? Financial incentives are available for you.

                                       Image of infiltration trench


The Water Quality Protection Charge Credit Program

After you have installed your infiltration trench, you are now eligible to receive a credit off your annual Water Quality Protection Charge (found on your yearly property tax bill).  The credit provides an incentive for maintaining your infiltration trench and other stormwater management practices.

You must apply for the WQPC credit separately – the credit will not be provided to you automatically.

Residential property owners can receive up to 50% off their WQPC depending on the type and size of stormwater management practices on the property.

Non-residential and multi-family properties can receive up to 50-60% off their WQPC depending on the type and size of the stormwater management practices on the property.

Learn more on the WQPC Credit webpage.


Image of an infiltration area.
Infiltration area on a residential property.