Wet and Dry Stormwater Ponds
A pond is a type of stormwater management facility designed to collect rainwater and pollutants and prevent downstream flooding.
Ponds have an embankment (called a dam) to hold back water that is entering the pond. Most dams are earthen (not concrete) and are grass covered. All stormwater ponds also have a control structure that releases water at a much slower rate than the stormwater entering the pond. While water remains in the pond, pollutants have time to settle at the bottom.
Most ponds located throughout Montgomery County are stormwater management ponds, even ones that are community amenities. Ponds can have many different designs, including ponds with concrete channels, dry ponds with sand filters on the pond bottom, and ponds that provided wetland habitat around the edges.
Why are Stormwater Ponds Important?
Stormwater ponds are important stormwater management tools, because they:
As rainwater flows over hard surfaces and lawns it picks up pollutants such as sediment, trash, pesticides from lawns, nutrients from fertilizer or pet waste, and oil and grease from cars. Ponds can help to reduce this pollution from entering our waterways.
Maintaining Stormwater Ponds
As the property owner, you are responsible for all maintenance of your stormwater pond unless a shared maintenance agreement has been made with the DEP Stormwater Facility Maintenance Program. Ponds at County facilities and schools are the maintenance responsibility of the Department of Environmental Protection.
Stormwater ponds require regular maintenance similar to other landscaped areas, including grass cutting, trash removal, and vegetation management. Please visit the stormwater facilities maintenance page for a list of approved contractors. DEP-approved contractors are recommended but not required for non-structural maintenance.
By maintaining your stormwater pond, you are doing your part to help the environment and protect your local streams and the Chesapeake Bay.
How Will I Know What Maintenance is Required?
Montgomery County regulations require that you perform ongoing routine grass cutting, trash removal, and vegetation management of your stormwater facility. If the work described below is not done regularly, you could receive a notice of violation.
✔ Mow grass in the pond area at least twice a year
✔ Manually remove all trees and woody vegetation in the following pond areas at least twice a year
✘ Do not apply herbicides, fertilizers, or pesticides in or around the pond. If manual removal of invasive weeds has been ineffective, limited applications of aquatic friendly herbicide may be applied by a qualified professional certified by the State of Maryland.
The most commonly forgotten non-structural maintenance is mowing and removal of trees and woody vegetation on the downstream slope of the embankment.
✔ Remove trash and debris from all areas in and around the pond monthly
Other Preventive Maintenance
✔ Know the pollutant sources on your property and try to reduce or eliminate the pollutants at the source
✔ Notify DEP if beaver activity or animal burrowing is observed
✔ Prevent trees and woody vegetation from growing in these areas
✔ Seed and cover adjacent areas of bare soil to prevent erosion
✔ Notify Montgomery County police if graffiti is observed
✔ Verify all pond safety signs are in place
✔ Inspect the facility after every major storm and contact DEP if you are concerned
These basic actions will keep your facility working correctly and prevent more serious repairs, which will save you money in the long term.
Structural maintenance must be performed by contractors who have been approved by DEP. No one should remove control structure manholes or enter the control structure without proper training, certification, and permits for confined space entry. Entering the water or any confined spaces without these requirements is a violation of State law and could be dangerous or deadly.
Ponds 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.
Can I remove my stormwater pond 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.
Pond Safety and Concerns
Stormwater ponds that are functioning as they were designed should not cause mosquito problems. DEP has developed a webpage and brochure with all the information you need to identify if mosquitoes are coming from a mal-functioning stormwater management facility and how to prevent these issues. The webpage also contains general information on mosquito biology and prevention.
The Montgomery County Code (section 36-3) requires that a person who owns or controls land that includes a publicly accessible pond must post warning signs around the pond and at any major approach to the pond, such as a path. A publicly accessible pond is defined as a water impoundment that:
The County Code has established standards for warning signs, including the size, message, construction, placement, and maintenance. They are listed in the table below.
Resources and Financial Incentives
Have a stormwater pond on your property? Financial incentives are available for you.
The Water Quality Protection Charge Credit Program
After you have installed your stormwater pond, 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 stormwater pond 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.