The Hazards of Leading Edges – Part II: Excavation

This week we’ll look at leading edge hazards in excavation work. OSHA regulates hazardous elevations starting at 48 inches (four feet) in general industry, and 72 inches (6 feet) in construction. However, proactive safety management programs look for leading edge hazards at any height and create plans to protect workers.

The leading edge of an excavation project poses several potential injury scenarios, including falls and cave-ins. The danger to workers and equipment is great if the edge warning is limited or non-existent. Devastating impact injuries occur from falling into excavation holes, especially if the worker lands on an object, such as a concrete pipe or concrete forms.

Never pile excavated material (spoils) too close to the edge of a trench/excavation. It obscures the view of the edge, which makes it possible for equipment to drive off the edge and into the excavation.

Soil at the leading edge of an excavation site has a low, unconfined compressive strength, meaning the soil does not have anything to push against when it is compressed. An edge with low compressive strength can result in the soil giving way, and anyone or anything at that edge will cascade into the hole.

Provide leading edge protection on an excavation site by doing one or more of the following:

  • Use snow fencing or other visual warning material to create a warning barrier.
  • Set spoils and equipment at least two feet from the excavation.
  • Where the site does not permit a two-foot set back of materials, temporarily haul spoils to another location.

Leading edges exist in all types of construction. Make sure your jobsite safety audit includes an inspection of all leading edges and provides a plan of action for protecting workers.

The Hazards of Leading Edges – Part I: Roof Work

Falls are the number one cause of fatalities in construction. According to OSHA, more than 800 construction workers die every year while on the job. Because falls cause one in three construction worker deaths, it is important to understand the safety principles for managing this hazard, regardless of the specific type of construction.

The hazard associated with falling is at the point of the leading edge, which we define as the break of elevation between one surface and another. The leading edge can be along a roofline, where the sheer sides of a building descend to the ground. This line of demarcation is the point where an uncontrolled descent – otherwise known as a fall – can begin.

Recognizing the leading edge as the point of hazard is critical. Once we pinpoint the area of the hazard, we can take the most appropriate protective measures for the conditions.

In roofing work, the leading edge is where the side walls meet the roof. We must use some form of fall protection for any work at or within six feet of the leading edge. It may involve using a positive tie-off to an approved anchor point or performing work under the strict supervision of a safety monitor, provided that individual is a roofing craftsman and a competent person on the jobsite.

Workers on large, flat-roof projects have the option of utilizing a fall protection method we refer to as the safety monitor/warning line approach, which entails establishing a warning line at a point that is six feet from the leading edge. This warning line must be at least 19 inches high and supported on stanchions that require at least 20 pounds of force to knock over. The line itself must be highly visible. You don’t need an additional fall protection system when workers are within this warning line.

When performing work outside of the warning line – that is, between the warning line and the leading edge – a safety monitor must directly supervise workers to ensure against any action that may result in a worker stepping, tripping and/or falling over the edge. The safety monitor may not engage in any other activity beyond watching and managing the safety of other workers who are between the warning line and the leading edge. All workers must be within the eyesight and voice command of the designated safety monitor.

The safety monitor/warning line system utilized during actual roofing work is one of the few situations where we can approach fall protection without using the more demanding system of using a positive tie-off to an approved anchor point.

In Part II of this Toolbox Talk, we will discuss the leading edge in other types of construction work.