What DNL contour must the airport own all property within, according to FAA?

The correct answer is based on the guidelines set by the Federal Aviation Administration (FAA) regarding noise exposure and land use near airports. The FAA stipulates that airports must own all property within the 65 DNL (Day-Night Average Sound Level) contour to ensure that the area is controlled to manage noise impacts on the surrounding community.

Owning property within the 65 DNL contour is crucial because this area represents the threshold at which significant noise impact can occur, influencing decisions on land use and ensuring that the airport can manage any potential adverse effects on residents or developments nearby. Therefore, while options like 70 DNL or higher represent more severe noise impacts, the requirement for property ownership to mitigate noise and its effects begins at the 65 DNL threshold.

This ownership allows the airport authority to implement noise abatement measures, maintain control over future land use, and mitigate any potential conflicts or complaints from nearby residents due to noise exposure. Thus, the correct selection centers on the FAA's focus on the 65 DNL contour for property acquisition and control, ensuring that the airport retains influence over the areas that experience significant noise levels.