Driveways

Driveways are a big deal! They include residential driveways, small lot subdivision access, commercial, industrial and emergency access ways. NEMO's research in CT has shown that residential driveways can contribute 15% to the total impervious surface area. National research shows that they are also hot spots for pollutant (auto and household hazardous waste) accumulation. In addition, most driveways concentrate runoff (and accumulated pollutants) and direct it to stormwater systems, where it may end up in local waterways essentially untreated. When they are paved with black top they become "heat islands" that elevate the temperature of the first flush of stormwater runoff.

Tips for reducing runoff from driveways

Planning/Regulatory Techniques
Reducing Imperviousness
Reducing Impacts

For more information download NEMO's Technical Paper on Driveways (PDF - 27k)

Planning/Regulatory Techniques

The number and size of impervious driveways found in a community is often related to minimum standards found in local zoning and subdivision regulations and road ordinances.

To reduce the number of driveways installed, review your towns zoning and subdivision regulations and road ordinances. Are shared driveways permitted? Allow shared driveways to serve commercial/industrial areas and up to four single-family lots.
What do your lot setbacks generate? Driveway length is often directly related to front yard setback requirements found in the local zoning regulations. For example, if local zoning requires a 50' front yard, a driveway at least 50' long will be needed to connect the garage and the street. If circular drives are installed, they will generally be longer than straight ones. Establish maximum limits on paved driveway lengths.
Are driveway standards asking for a minimum width that can be easily exceeded? Establish maximum limits on paved driveway widths. width of 9' is usually more than adequate, for comfortable and safe driving and parking on a single lane driveway.

Specify limits on paved lengths for driveways.

Minimize width as specified by zoning regulations can be exceeded!

Reducing Imperviousness

Allow various driveway designs, including ribbon drives.
Allow the use of alternative paving surfaces. Many local driveway regulations require impervious pavement. Driveways with grades of less than 7% may not need pavement while those greater than 7% should have some type of surfacing to prevent erosion. There are various materials available that, when designed and installed properly, will support vehicle weight and let runoff soak in. There are several options for porous driveway surfaces. The key to the use of porous driveway surfaces is the installation of a sub-base specifically designed to promoting infiltration and runoff cleansing.


Ribbon driveways reduce imperviousness. Haddam, CT.	Alternatives to pavement can allow water to infiltrate rather than concentrate, collect and be conveyed off the site. Wallingford, CT.

Ecostone driveway at Jordan Cove subdivision, Waterford, CT.

Reducing Impacts

Design impervious drives to follow contours encouraging sheet flow of stormwater over porous areas (avoid grassed areas that use heavily applied chemicals and septic leaching fields!). Grassed swales installed along paved drives can provide additional pollutant renovation and infiltration.
Install driveways with a crowned surface, so that a greater portion is shed to the sides as sheet flow. The vegetated areas to the sides of the driveway will easily be able to handle this runoff.
Where impervious driveway surfaces are installed, avoid direct connections to the storm drain system by using porous materials in the area where the drive intersects the road.

Grass pavers in a firelane in Waterford, CT.

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