If BDU is closed, the remaining flight traffic would be less intrusive and less polluting because it will just be passing over. Repetitive landings and take-offs within the city limits - which cause the majority of noise and local lead pollution - would be eliminated.
Some have argued that flight traffic from BDU “protects” the airspace over Boulder, and that if BDU closes, planes from other airports will fill in the airspace. This is a misleading and inaccurate argument. BDU attracts aviation impacts; it does not protect against them.
In addition to the small number of Boulder-based pilots who use BDU, having runways attracts planes from nearby airports to practice here, often in repetitive “touch and go” patterns where they land and take off again without stopping, repeatedly circling over Boulder homes, schools, parks, and protected wildlife habitats, trailing noise and lead pollution in their wake.
If BDU closes, the use of airspace over Boulder would change. Without an airport to land at, flight traffic would be passing through the airspace higher up. Planes passing through at higher elevations create fewer impacts, both in terms of noise and also lead pollution, than planes flying low to the ground, taking off and landing three miles from downtown Boulder, in the middle of existing neighborhoods.
It is also vital to understand that if the airport stays, it is expected to at least double its flight traffic in the coming years. Airport growth is the goal of the FAA, the aviation industry, BDU-based aviation businesses, and is supported by the current airport management. Boulder's airport manager has advocated for starting a new FAA Airport Master Plan update, which would be a blueprint for airport growth and development, sinking more federal money into the airport and incurring decades of obligations to the FAA.