Protective Systems in a Trenching Project: When Are They Necessary?

July 4, 2019

As a common-sense measure, trenching protection systems are adopted when the walls of an excavated ground channel are dangerously high. But that's something of a subjective term. When is "high" too high? According to most nationally recognized health and safety regulations, if a trench wall rises higher than 1.5 metres (5-feet), then that soil face must be fitted with a protective system of some kind. Of course, even that regulation is subject to interpretation.

Call Out the Competent Person

Is the job going to get the go-ahead if the trench faces are less than 1.5 metres high? That question's not as easy to answer as you'd think. A competent person needs to show up to check out the situation. That professionally accredited individual sees workers crouched down low and sitting on their haunches. The wall faces are therefore way above their heads. Arguably speaking, a protective system could be installed here, even though the walls are less than a metre high. Another factor that influences the standard height limit is soil condition. If the dirt is tight and loamy, then it's probably stable. If there's water seeping out of a loosely packed soil face, a series of trench shields made of rigid timber or strengthened alloy sheets, should buttress the excavated trench walls. At the end of the day, if a cave-in possibility exists, a competent person must order the installation of trench shoring.

Assessing Trench Conditions

Let's keep that man in charge onsite for a little longer. The bottom of the excavated trough needs further assessment before the job can begin. What's down there? If there are electrical lines, the relevant safety procedures must be adopted. If the line is a pipe, full of raw sewage, the trench workers need to have their inoculations card updated. Sewage waste carries all kind of nasty bacterial parasites, after all. Furthermore, a cracked sewage line will likely discharge gaseous emissions. As another form of protection, the personnel in the trench will need to wear respiratory gear before they can sink down into a pit that's full of heavier-than-air sewage emissions.

An entire support system comes together to protect trenching personnel. They're wearing their reflective vests at night. During the day, after a night's heavy rainfall, pumps are removing flood water. Nobody goes into the muddy channel until it dries out. Again, that's the competent person's decision. Again, whether trench walls require benching or shoring, the decision isn't a clear-cut one. There's the standard 1.5-metre limit, which functions as a good guideline, but such standards aren't just blindly followed. Someone has to assess the soil condition and trench content. That job, as always, falls into the hands of a site-approved competent person.

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