Car Lot overland flow, Dane County Regional Airport |
The Dane County Regional Airport in Wisconsin, US had to increase its stormwater capacity to meet requirements of treating 40% of total suspended solids. This article looks at why a final filtration solution was chosen as part of small retention pond.
By Natasha Wiseman
Airports are often a big contributor to stormwater loading due to extensive roofed buildings and other impervious surfaces including the runway, taxiways, apron, access roads and parking lots. The stormwater runoff may be polluted with hydrocarbons from fuel, de-icer residues, suspended sediments, particulate and dissolved metals and wind-blown trash.
While many airports were built before environmental regulation required them to conform to stormwater quantity and quality standards, any facilities undergoing expansions or new construction must comply.
Airports are usually constructed on flat ground either on a plain, or on a valley floor. The topography therefore puts flow restrictions on the drainage, because achieving sufficient head for efficient water flow over long distances requires careful design and planning. Flat topography also favours temporary standing water; all things considered, airport drainage is a complex subject.
No compromise on safety
Another factor that must be considered is aircraft safety. In addition to reducing the standing water hazard on runways, airports spend time and money to minimise hazards from bird strikes on aircraft by reducing attractions for birds.
Temporary or permanent surface water pools that could attract water fowl to the vicinity of an airport are considered dangerous. Along migration routes such as the Mid-West corridor, where large waterfowl move in huge seasonal numbers, extra care must be taken.
Conventional land-based methods of managing airport runoff, such as temporary ponds and wetlands, therefore run counter to Federal Aviation Authority (FAA) guidelines, which do not allow ponds that retain water for longer than 48 hours.