A sand filter is a type of stormwater management facility designed to filter rainwater through sand to remove pollutants. Filters are typically a depression in the ground filled with sand that helps to manage polluted or excess rainwater. To the untrained eye, it may look like a sand box or volleyball court. You can find sand filters in residential neighborhoods and around commercial businesses.
During a storm, rainwater collects pollutants as it flows across hard surfaces, such as rooftops, sidewalks, and roads. Flow splitters are often used to send a certain quantity of untreated water, known as the “first flush,” to a surface sand filter. The sand filter captures the rain water, directs it through layers of sand and gravel that filter and remove the pollutants, and returns the clean water back to the local stream or into the storm drain system.
Sand filters are often found with infiltration trenches.
Why are Sand Filters Important?
Sand filters 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. Sand filters reduce this pollution and stormwater runoff entering our waterways.
Maintaining Sand Filters
As the property owner, you are responsible for all maintenance of your sand filter unless a shared maintenance agreement has been made with the DEP Stormwater Facility Maintenance Program. Sand filters at County facilities and schools are the maintenance responsibility of the Department of Environmental Protection.
Sand filters 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 like weeding or trash pick-up.
Un-maintained sand filters may:
By maintaining your sand filter, 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 at least twice a year
✔ At least twice a year
✘ Do not apply herbicides or pesticides within the facility. Vegetation removal should be performed manually.
✔ Remove trash and debris from all areas in and around the filter monthly
Performing preventive maintenance regularly will prevent long-term damage and help avoid potential violations. These actions will keep your facility looking good and working correctly, which will save you money in the long term. The preventive maintenance actions listed above can be thought of as similar to preventive car maintenance (like changing the oil in your car every 3 months).
✔ 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
✔ Keep children from playing in the sand or stones
✔ Inform contractors working on your property of the location of the sand filter to prevent accidental damage and the placement of snow over the sand filter
✔ Inspect the facility after every major storm and contact DEP if you are concerned
Structural maintenance is work done on the components of the filter that allow it to control rainwater and remove pollutants. Structural maintenance problems in the table below are things you should be looking out for. When they happen, call DEP for help (like calling your mechanic when the engine light comes on).
The DEP performs inspections of all sand filters in Montgomery County every 3 years. If DEP finds maintenance issues during its inspection, you will receive a notice of violation with a work order showing a list of items that need to be performed to restore your facility to proper working condition. You will have 60 days from the date of the notice to make the noted repairs. A civil citation may be issued if you have not complied with the maintenance requirements.
DEP can answer your questions and provide additional guidance about maintaining your stormwater facility. Please email firstname.lastname@example.org or call the Montgomery County Customer Service Center at 3-1-1.
Sand Filters 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 sand filter 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 sand filter on your property? Financial incentives are available for you.
The Water Quality Protection Charge Credit Program
After you have installed your sand filter, 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 sand filter 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.