There’s more to tab data than charts and tables.
Most trench fatalities happen in unprotected trenches, but previous studies estimate that 24% occur when sloping, benching, shielding or shoring is used improperly. In these tragic incidents, OSHA tables and charts for sloping, benching, timber shoring, or manufactured systems with tabulated data using shields or shores are not being followed.
“There are a variety of shoring and protection systems, and it’s important that the competent person understand the tabulated data for each one that the contractor wants to use,” said Joe Wise, regional customer training manager, United Rentals Trench Safety, in a recent webinar on understanding manufacturer’s tabulated data.
Too often, that understanding is missing. In 2019, United Rentals partnered with the Center for Construction Research and Training to distribute an OSHA/NIOSH survey on trench safety issues. The survey revealed that more than 40% of respondents had trouble with tabulated data and the installation and use of protective systems.
To help improve those numbers, the United Rentals Trench Safety Team shared some critical do’s and don’ts for using a trench protective system and following manufacturer’s tabulated data. Below are some highlights.
Follow the depth ratings
Manufacturer’s tabulated data contains tables and charts that dictate whether the protective system can be used at certain depths and under certain conditions. OSHA does not allow contractors to use the system outside of these parameters unless the manufacturer has given prior approval or a Registered Professional Engineer has approved that usage in writing.
Look beyond the charts and tables
In addition to charts and tables, manufacturer’s tabulated data includes instructions for safe and appropriate use of the protective system.
“Unless we understand everything necessary and written out by the manufacturer, we're going to be misusing that particular equipment that was designed to protect workers,” said Wise.
For example, if a contractor wants to use a system that includes parts from two or more manufacturers, the competent person must check the manufacturers’ instructions to determine whether doing so is permissible.
Know that similar systems are not the same
A lack of industry-wide standards means that for the same type of protective system, each manufacturer’s tabulated data will be different. The competent person must carefully read and consider the tabulated data for each individual system in regard to factors such as:
- Surcharge loads
- Allowances for soil types
- Dewatering limits
- Limitations on depths with vertically sided lower portions
- Time limitations on use of the system
Account for changing conditions
The manufacturer’s tabulated data must be kept on the jobsite during construction because conditions can change quickly. A sudden downpour, for example, may affect soil conditions or flood the trench.
After such an event, and on a daily basis, the competent person must conduct inspections of the site and refer to the tab data to ensure that use of the protective system still falls within the limits of safe operation. These checks are also needed when the trench becomes wider or deeper, when more pipe clearance is needed and when the contractor is using a shield and sloping out the sides of the trench.
Understanding and following all the requirements spelled out in tabulated data does take time and effort. But it’s the competent persons’ responsibility and duty to have every worker climb out of the trench at the end of each day and return home unharmed.