A grass drainage swale is an open channel that collects water from hard surfaces and allows it to percolate into the ground, reducing the amount of runoff leaving the road or property. The grass covering the side slopes and swale bottom provides a filtration surface for the water and helps to reduce the flow velocity.
In steeper areas, some swales have stone or concrete ‘check dams’ across the width to help slow the flow rate, promote infiltration, and prevent erosion.
During large storms, swales can direct extra runoff to other stormwater facilities or the storm drain system. Swales are commonly found along roads, parking lots, or between properties of residential lots.
Some grass swales are bioswales and have special soils to increase infiltration.
Maintaining Grass Swales
As the property owner, you are responsible for all maintenance of your grass swale unless a shared maintenance agreement has been made with the DEP Stormwater Facility Maintenance Program.
An un-maintained grass swale may:
DEP can answer your questions and provide additional guidance about maintaining your stormwater facility. Please email email@example.com or call the Montgomery County Customer Service Center at 3-1-1.
Grass Swales 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.
Can I remove my grass swale 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 grass swale on your property? Financial incentives are available for you.
The Water Quality Protection Charge Credit Program
After you have installed your grass swale, 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 grass swale 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.