Excavator Strike on a Buried Service
You are trenching for a stormwater line with a 13-tonne excavator. The plans show a 100 mm water main running parallel to the trench at 1.2 m depth, 2 m to the north. You have hand-dug and located it at the expected position. At 1.1 m depth, about 8 m along the trench, the bucket contacts something solid and you hear a sharp hiss. The trench is 1.6 m deep at that point, unsupported, with a spoil heap 1.5 m from the edge. Two labourers are working in the trench 5 m away. The water main you located is still intact - the strike is on something not on the plans. Your supervisor is 40 m away and has not seen it.
1. What are your immediate actions in the first 30 seconds?
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Stop immediately and act in a fixed order. Stop the machine, lower the bucket to the ground, and shut down. Signal and warn the two labourers to get out of the trench now - an unplanned service strike could be gas, power, or water, and an unsupported 1.6 m trench with a 1.5 m spoil heap is already a collapse risk. Do not attempt to identify the service by digging further or by hand near the strike. Raise the alarm to the supervisor and, if gas is suspected, clear the area, remove ignition sources, and call the emergency number. Isolate if you can do so safely - for water, locate the valve; for gas or power, do not approach. Keep people back, establish an exclusion zone, and wait for the supervisor and the service owner. Record what happened.
2. The supervisor arrives and says "it's probably just an old stormwater pipe, keep going". How do you respond?
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You should not keep going. The hiss indicates a pressurised escape - that is consistent with water or gas, not a dry old stormwater pipe. Continuing to dig risks a larger rupture, trench flooding, or ignition if it is gas. Also, the trench is unsupported at 1.6 m with a spoil heap too close to the edge - both are unsafe regardless of the strike. The correct response is to explain what you observed (solid contact, sharp hiss, not on the plans), state that the service is unidentified, and refuse to continue until it is identified and made safe by the service owner or a competent person. Offer to help establish the exclusion zone and call the service locator. Document the refusal and the supervisor's instruction in the site diary. If the supervisor insists, escalate to the site safety officer.