Which agency may require the installation of obstruction lights on an elevated tank depending on its height and location?

The agency responsible for requiring the installation of obstruction lights on elevated tanks is the Federal Aviation Administration (FAA). This requirement stems from safety protocols designed to ensure that any structure which may potentially obstruct air traffic is clearly marked, particularly if it is of significant height or in proximity to an airport or flight paths. The FAA's regulations are aimed at preventing accidents by making such structures visible to pilots during both day and night, thereby enhancing safety in air navigation.

Other agencies listed, such as the Environmental Protection Agency (EPA), focus on environmental protection and regulation but do not engage in aviation safety. The Occupational Safety and Health Administration (OSHA) deals with workplace safety and health concerns rather than airspace safety. The National Transportation Safety Board (NTSB) investigates transportation accidents but does not impose regulations regarding the installation of safety measures for structures like elevated tanks.