In accordance with the Clean Water Act, airports must responsibly manage stormwater runoff through a combination of industrial stormwater permitting, MS4 permitting, and state/local post-construction stormwater requirements for development. Permitting requirements for airports can vary widely across the nation, with some airports also subject to municipal stormwater fees. These fees may be reduced via credits for effective on-site management (quantity and quality). Given that water quality is a significant component of these responsibilities, a firm understanding of stormwater quality from various airport land uses will help airports manage permitting requirements and obtaining stormwater fee credits.
Unlike highways, which have had extensive research related to stormwater runoff quality, there are few studies on stormwater runoff quality from various portions and layouts off existing airports and airfields. Yet runoff from runways and taxiways is often compared to that from highways or other high intensity uses, which doesn't appear to be appropriate, especially at airports that do not deice runways and taxiways (due to either climate or airport classification). Preliminary studies indicate that runoff from runways and taxiways is cleaner than most regulatory staff realize, due in part to natural treatment occurring next to these areas and may actually function as Low Impact Development (LID). Runways and taxiways are often flanked by large, grassed areas that help mitigate runoff volume and quality before it leaves the airport property. More data is needed to evaluate the hypothesis that airports can effectively treat runoff with grassed areas and vegetated swales before the runoff leaves the airport property. A positive conclusion could mean additional treatment or best management practices (BMPs) are not required for these airports and, furthermore, that stormwater fee credits may be appropriate based on runoff reduction from these features.