Before starting work at a site, which of the following must be present?

The essential requirement before starting work at a site is to ensure that a copy of each worker's permits is present. This is critical because permits validate that each worker involved has completed the necessary training and is certified to perform their specific tasks safely and correctly. Compliance with local regulations and safety standards is paramount in construction and lead abatement operations, making the verification of these permits vital before any work begins. This ensures not only the safety of the workers but also compliance with legal and regulatory standards.

Other options, while relevant to a safe working environment, do not embody the same regulatory urgency as ensuring that workers possess the proper permits. Having a competent person license, insurance verification, and a completed safety checklist are important for overall site management and safety; however, the presence of worker permits is specifically mandated for personnel engagement at the site.