Dewey commissioners clarify pervious, impervious surfaces

Citing a goal to eliminate runoff as much as possible, Dewey Beach commissioners voted unanimously March 15 on an ordinance to clarify requirements for pervious ground-level surfaces on residential or residential/commercial mixed lots.

Commissioner Gary Persinger said it was best to generally define impervious and pervious materials in the ordinance because there is no guarantee that any list of materials will handle all concerns. 

Town Counsel Fred Townsend said a Catch-22 exists in that the town can better enforce standards the more specific the ordinance is, but specificity can also create loopholes in that a list of approved materials would not capture new technology.

The ordinance states that no portion of any lot developed for a residential or mixed commercial/residential can be covered or paved with impervious materials, installed in such a way that impervious surfaces are created for any ground-level surface, including driveways, parking spaces and sidewalks, or any other structure not directly under a roof.

A required swimming pool walk space may have an impervious surface, but the walk space may be no wider than 3 feet. Persinger said swimming pools have to hold water and can’t be constructed with pervious materials, but the walkway could be.

Pools are permitted in Dewey Beach, Townsend said, and the minimum three-foot walkway around them is required for safety. The pool can’t go right up against a fence because people need to get out, he said, so it’s  an exception to the impervious surface prohibition. A pervious walkway could be constructed with a concrete-like surface surrounding the pool but that’s very expensive, he said.

Building official Daune Hinks said that pools have a minimum 10-foot side-yard setback from the pool’s water edge to the property line, and a minimum 6-foot rear-yard setback from the property line to the water’s edge.

Hinks said artificial turf is also permitted, depending on the manufacturer. Materials may state they are pervious, she said, but she requires documentation as part of the application process that shows the perviousness and rate water will perk through.

Impervious is defined as a material or surface that does not allow water or other fluids to pass through it, preventing filtration leading to increased runoff, which can contribute to flooding and erosion. Such materials include asphalt, concrete and plastic.

Pervious is defined as a material or surface that allows water or other fluids to pass through it and infiltrate the ground, and it includes gravel, porous concrete or permeable pavers.

The ordinance was recommended by the planning and zoning commissioner and goes into effect March 15. Impervious surfaces existing before March 14, 2009, may continue as a nonconforming structure, and may be repaired, but cannot be expanded horizontally or vertically, or rebuilt or replaced with impervious materials.