Excavation operations are not permitted under sidewalks unless what is in place?

Excavation operations under sidewalks necessitate the presence of a support system to ensure the structural integrity of the sidewalk and protect both workers and pedestrians. Sidewalks provide essential support to the surrounding structures and, without adequate support, they could collapse, leading to potential injuries and liabilities. A support system is designed to brace the sidewalk, distributing loads appropriately and preventing cave-ins during excavation activities.

In this context, while safety signs, heavy machinery, and temporary fences might be important for overall site safety and management, they do not directly address the critical issue of structural support needed when excavating under sidewalks. The presence of a support system is a fundamental requirement to maintain safety standards and comply with excavation regulations.