Which of the following is a potential environmental hazard on the airside?

Fuel spills represent a significant environmental hazard on the airside due to the potential for contamination of soil and water. When fuel leaks occur, they can lead to pollution of the surrounding environment, affect local wildlife, and pose fire hazards. Proper management of fuel handling practices and prompt cleanup of spills are crucial to mitigate these risks and protect both the environment and the safety of airport operations.

Other activities such as birdwatching, while potentially interesting, do not present the same level of environmental risk on the airside. Ground service delays and passenger congestion are more operational concerns and relate primarily to efficiency and service rather than direct environmental hazards. Thus, the focus on fuel spills highlights the importance of environmental awareness and safety in airport operations.