Seven-Foot Trench Through Fill With Water
Northgate Utilities is repairing a sewer lateral in a 7-foot-deep, 4-foot-wide, 20-foot-long trench. The soil looks like stiff clay, but the north end cuts through an old fill area with brick rubble, and water is seeping in. There is no shoring, shielding, or sloping. The spoil pile is about 3 feet from the trench edge and roughly 4 feet high. The only ladder is 30 feet from the workers' end of the trench. The competent person looked at the trench at 7:00 a.m. and said, 'Clay stands fine; we'll be done by noon.' A worker is about to enter to hand-dig around the lateral.
1. What hazards and required controls apply before the worker enters?
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The trench is 7 feet deep, so a protective system is required before entry. The competent person must inspect the trench and classify the soil, but the presence of water, brick rubble, and old fill makes a simple 'clay stands fine' conclusion unreliable. Those conditions point toward a less stable soil classification and require a protective system designed for it.
The spoil pile is also too close; it should be kept at least 2 feet from the edge, and here it is 3 feet away and 4 feet high, adding surcharge load. Access and egress must be within 25 feet of workers, but the only ladder is 30 feet away. The sewer lateral may also present atmospheric hazards, so testing may be needed before entry.
2. The foreman proposes sloping the walls back at 3/4:1. Is that adequate? Explain your reasoning.
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Probably not. A 3/4:1 slope is the steepest allowance and is associated with Type A soil. Type A cannot be assumed where there is water, fill, or previously disturbed ground, and this trench has water seeping in and brick rubble from old fill.
If the competent person classifies the soil as Type B, the required slope is 1:1; if Type C, it is 1.5:1. The foreman's proposed slope is therefore likely too steep. The competent person needs to classify the soil based on the actual conditions and select a protective system, which may be sloping, shoring, or a trench shield. The spoil pile and water also have to be controlled.
3. The worker says he is not comfortable entering. What are his rights and the employer's obligations?
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The worker should not be forced into an unprotected 7-foot trench. Employees may refuse to perform work when they have a reasonable belief that an imminent danger exists, and the employer may not retaliate against them for raising the hazard or refusing.
The employer's obligation is to correct the hazard before entry: provide a protective system, move the spoil pile, provide safe access and egress, address the water, and have the competent person re-inspect. If the employer pressures the worker to enter, that is both a safety problem and a potential retaliation problem.