Is gravel considered impervious surface?
Yes. It is difficult for water to soak into a packed gravel surface. Once gravel is compacted, from cars or heavy equipment for example, surface water runs off of it much like a paved surface. The gravel may slow the flow of water from the area, but nearly the same amount of runoff will flow from the area under the gravel as if the gravel was not there. Many flat roofs are covered with gravel, but they still shed the rainwater that falls on them. In addition, if cars or heavy equipment are traveling on these gravel surfaces; runoff typically carries pollutants like metals, or petroleum into our waterways.
New gravel is not considered impervious under the Stormwater Management rules. However, if an applicant can demonstrate that under existing conditions on a previously developed site, the gravel material performs as an impervious surface, it may be considered impervious for the purposes of redevelopment. It is important to note that gravel may be considered impervious under other Department rules.
