tolerance zone is the area where you aren’t supposed to dig with machinery

Safety regulations for machinery operation within tolerance zones and prohibited excavation areas include several key considerations. A warning system must be utilized when mobile equipment is operated adjacent to an excavation, especially if the operator lacks a clear view of the edge. Acceptable warning systems include barricades, hand signals, mechanical signals, or stop logs. [1]

Employees should be provided with and wear warning vests or other suitable garments marked with or made of reflectorized or high visibility material when exposed to vehicular traffic. [1]

It is important to preplan excavation operations to avoid cave-ins. Important questions to consider prior to digging include:

• What types of soil will be found?
• What are the soil moisture conditions?
• Has the soil previously been disturbed?
• How large will the excavation be?
• How long will the excavation be open?
• What kinds of weather can we expect?
• What kinds of equipment will be on the job?
• Will the excavation be near structures?
• Is traffic control needed near the excavation?
• What sources of vibration will be nearby?
• Will water be a problem?
• What kind of shoring? How much?
• Underground installations?

[3] Additionally, a competent person should inspect the excavation site daily, before each shift, and after any event that could increase hazards, such as precipitation or a thaw. The competent person should also ensure that spoil piles are at least two feet from the trench edge and that there is a safe exit within 25 feet of each worker. [2]

Employees are not allowed under loads handled by lifting or digging equipment and must be protected from vehicles being loaded or unloaded to prevent falling material. [1]