Which of the following activities is required prior to commencing excavation work on a building site?

Contacting "Call before you dig" is essential prior to starting excavation work because it is a crucial safety measure designed to prevent damage to underground utilities and ensure the safety of workers and the public. This service allows contractors to determine the location of any buried utilities, such as water, gas, electricity, and telecommunications lines, which helps avoid accidental strikes that can lead to serious injuries, service disruptions, and costly repairs.

While notifying local authorities, obtaining a construction permit, and scheduling utility relocation may also be important steps in the overall process of preparing for excavation, the "Call before you dig" service specifically focuses on utility identification and is a targeted action that directly preempts hazardous situations related to excavation activities. Thus, ensuring this step is followed helps maintain safety and compliance before any physical digging begins.