Excavation Safety

Background Information:

Excavation and trenching operations are among the first undertaken at a construction site. Because of a lack of distinction between a trench and an excavation, both shall be considered an excavation for the purpose of this document and both are subject to the same requirements. There are numerous hazards often associated with excavations:

  • Accidental cave-ins of earth that has been excavated accounts for a large majority of construction-site fatalities in the United States each year. In many cases, workers receive no warning when excavated ground collapses, and they find themselves trapped under tons of soil.

  • Excavations can also damage underground utilities. Besides being costly to repair and a disruption to campus activities, damage to utilities can cause significant property damage, serious injury or even death.

  • Excavations can also present a fall-hazard to both workers and pedestrians. See photo below:

 Excavation at UWM Sabin Hall, Fall 2000
Excavation at Sabin Hall (Fall 2000) for chilled water connection.
Excavation for new construction. Note the deteriorated fencing.
Excavation for new construction (Spring, 2001). Note the deteriorated fencing.

Site Preparation For Excavations:

Prior to excavation at UWM, underground utilities shall be marked according to the following color codes in accordance with Wisconsin Statute 182.0175 and ANSI Standard Z53.1. For additional information, please see the Digger's Hotline website

The Milwaukee Diggers Hotline has prepared a resource document entitled "The Excavators Guide to Diggers Hotline" for use as a reference tool by Wisconsin's professional excavators.

www.diggershotline.com

Red Electric Power Lines, Cables, Conduit and Lighting Cables
Yellow Gas, Oil, Steam, Petroleum, or Gaseous Materials
Orange Communication, Cable TV, Alarm or Signal Line Cables or Conduits
Blue Water, Irrigation or Slurry Lines
Green Sewers and Drain Lines
Pink Temporary Survey Markings
White Proposed Excavation

Site Protection:

All excavations must be protected to prevent pedestrian traffic near the excavation site. Examples of minimally acceptable protection may include cyclone fencing, complete barricading, or OSHA standard railings around the entire site. Protection shall be placed well away from the excavation/trench if at all possible. Plastic barricade tape at the edge of an excavation is not acceptable site protection and will not be tolerated. Accident -prevention warning signs or flashing-barricades should also be placed adjacent to excavations.

Note the barricade fencing for protection from both the excavation and swing-radius of shovel in the photo to the right. This project was the UWM Library steam line replacement during the Fall of 2000.

 Excavation at UWM Library Fall 2000
Example of poor protection On the left is an example of deficient protection and site-security at an excavation site (August 1998). Contractor failed to maintain protective fencing/barricade systems around the entire site.

Personal Protection:

A stairway, ladder, ramp or other safe means of egress shall be located inside excavations that are more than 4 feet deep. The means of egress shall not be more than 25 feet from any worker in the excavation. If a ladder is used, it shall be properly secured and extend at least 3 feet beyond the surface or top of the trench box (OSHA 29 CFR 1926.651(c)).

Workers exposed to vehicular traffic shall wear DOT orange vests (OSHA 29 CFR 1926.651(d)).

Workers shall not enter an excavation during digging operations or an area where material is being mechanically lowered or raised (OSHA 29 CFR 1926.651(e)).

When the atmosphere in an excavation is hazardous, has a potential for becoming hazardous, or is deficient in oxygen, the atmosphere shall be tested each time workers enter to begin their activities, and as often as necessary during the operation to ensure safety. See the UWM Confined Space/Hazardous Space Entry Program for additional information (OSHA 29 CFR 1926.651(g)(1)(i-iv); (g)(2)(i-ii)).

Daily inspections of excavations and adjacent areas shall be conducted by a competent person before work begins and as needed throughout the shift. Of particular concern is the presence of rain, snow, or excessive vibration. If there is an indication of a hazard, work shall be stopped immediately, and the excavation shall be evacuated until appropriate support systems or control measures are installed (OSHA 29 CFR 1926.651(k)(1,2)).

Be on the lookout for buried asbestos. We have encountered "abandoned in-place" asbestos insulated utilities on numerous occasions.

Protective Systems:

An adequate protective system shall be used to protect workers in excavations from cave-ins in all excavations greater than 5 feet in depth, unless the excavation is entirely in stable rock (OSHA 29 CFR 1926.652(a)(1)(i-ii)).

Workers shall not be permitted to work at levels above other workers, when there is the inadequate protection from the hazards of falling, rolling, or sliding material or equipment (OSHA 29 CFR 1926.652(f)).

Workers shall also be protected from cave-ins when entering or exiting areas (OSHA 29 CFR 1926.652(g)(1)(iii)).

Other Resources:

Reference: U.S. Department of Energy, Construction Safety Reference Guide DOE/ID-10447, Section C. Excavations, September 1993.

Updated February 8, 2006 by SAK