Remember Trenching and Excavation Safety!
Whether for replacing aging culverts or repairing or installing a water or sewer line, most workers in municipal road/highway/public works departments need to dig holes or trenches or perform some type of excavations. Once an area has been excavated, one or more employees often need to enter the hole to perform whatever work is required. While an employee’s focus is generally on the task at hand, the sides of an unsecured excavated area can be unstable and collapse unexpectedly, potentially resulting in entrapment, injury, or even suffocation. These hazards – and the OSHA regulations for preventing them – make it necessary for employers to provide appropriate safety equipment and training to all affected employees and for all employees working in or near an excavation worksite to closely adhere to established safety practices.
Trenching and excavation operations create serious hazards that every employer should take seriously.
In addition to the moral and ethical reasons for adhering to excavation safety rules, municipalities need to know that VOSHA inspectors can stop and examine any suspicious looking excavation that they happen to pass. Thus, any employer that does excavation work can be subject to a VOSHA inspection and potential fines at a moment’s notice. VOSHA fines for unsafe excavations can run into the tens of thousands of dollars, creating a financial incentive that supplements the moral and ethical responsibility for each employer to provide a workplace that’s free from recognized safety and health hazards.
Completing excavation work safely requires a number of skills, specialized equipment, and an understanding of what the regulations require. This article highlights some of the key requirements and also includes some PACIF guidance, based on our experience.
We have listed some major requirements and best practices below to inform and/or remind our readers, in hopes that everyone will leverage this knowledge into safe excavation operations. For complete details on applicable regulatory requirements, refer to OSHA standards 1926.651 and 1926.652, which VOSHA has adopted verbatim.
Trenching and excavation best practices and requirements include but are not limited to:
- Excavations must be overseen by a competent person. A competent person is one who has the knowledge and skills to evaluate and identify safety hazards and ensure the safe operation of the excavation process. That person must also have the authority to cease operations if uncontrolled hazards of any type are identified.
- Excavations that are four feet (4') or more in depth at any point must have means of egress that are within 25 feet (25') of employees. Ladders, stairs, or ramps may be used. Make sure ladders are rated for the weight of the employees using them.
- If the excavation has exposure to vehicular traffic, employees must wear appropriate Class II retroreflective garments and be protected by a properly designed and operated workzone, including traffic control if needed. Traffic and related vibrations also increase the risk for excavation collapse, which should be considered as part of evaluating excavation safety.
- Employees must be protected from excavated or other material (e.g., a spoils pile) and equipment that could pose a hazard by falling or rolling into the excavation. The best practice is to keep material at least two feet (2') away from the edge of the excavation. Heavy equipment, road traffic, etc. should be kept further away from the excavation to prevent accidental collapse.
- Unless the competent person is skilled in soil classification, all soil types should be considered as soil type C for the purpose of complying with excavation standards. Soil type C is the least stable soil type and therefore it requires the largest exposed opening when shielding or shoring systems are not used. It should be noted that soil that has been previously excavated is automatically classed as soil type C, as is any soil with evidence of water seepage or standing water.
- Any excavation that is five feet (5') deep or more at any point within the excavated area must be sloped and benched according to the soil type, or it must be properly shielded or shored. When using shielding systems, additional considerations include:
- The system must be used in accordance with its engineered design.
- It is permitted to excavate material as much as two feet (2') below the depth of the support system if the system is designed to resist the forces calculated for the full depth of the trench. The top of the trench box should be 18 inches (18") above grade.
- Employees should not be in an excavation when shields or boxes are being installed, moved, or removed. When using gas-powered equipment or products that contain chemicals within the excavation, consider the potential for hazardous atmospheres to develop.
- If shoring or shielding is not used, it is best to assume that soil type “C” exists and apply a slope or bench of 34 degrees (34°) or a run/rise ratio of 1.5:1. This will require significant enlargement of the excavation, e.g., a 34-foot (34') opening for a trench that is ten feet (10') deep and four feet (4') wide.
- The open ends of trench boxes are often inappropriately left unprotected, thus subjecting employees who are in the excavation to soil collapse. Bulkheads should be used in these areas as needed to protect against this hazard.
- Trenching and excavation operations create serious hazards that every employer should take seriously. Employees should never enter an excavation that is unstable or deeper than five feet (5’) without adequately opening up the excavation or using appropriate shielding or shoring. Doing otherwise exposes employees to serious hazards and exposes the employer to serious fines.
We encourage all VLCT members to get educated on how to perform excavations safely and exert safety discipline while performing these tasks. Our loss control staff is ready and willing to assist PACIF members with their education efforts and can meet with individual municipalities to answer questions about excavation practices. Additionally, Vermont Local Roads occasionally offers workshops on this topic. If you have questions, please reach out to your loss control consultant directly or contact us at losscontrol@vlct.org
