Excavation after heavy rain: safe re-entry

Rain changes an excavation. Before anyone re-enters a trench that has been wet, softened or visibly altered, keep people out, have a competent person re-inspect the excavation and its support, and record the decision. Rainfall is an event that can affect stability, so the previous inspection no longer answers whether it is safe.

What has happened

Overnight or during a break, heavy rain leaves a trench or excavation waterlogged, with softened or slumped sides, washed-out fines, standing water or a changed appearance. The crew wants to pump out and carry on. But HSE excavation guidance and regulation 22 of the Construction (Design and Management) Regulations 2015 require an excavation that could collapse to be inspected by a competent person at the start of each shift and after any event likely to have affected its strength or stability. Rain is such an event, so re-entry waits for a fresh competent inspection.

Immediate actions

Keep everyone out of the excavation and away from the edges, and stop plant working close to it until it is assessed. Physically prevent access if needed. Arrange a competent person to inspect the excavation, its support or battering, the surrounding ground and any surcharge from spoil, plant or adjacent structures. Consider dewatering under a safe method, and reassess the support system, which may now be more heavily loaded. Only allow re-entry once the competent person confirms it is safe, and record the inspection outcome (a report is required under CDM 2015 where the excavation could collapse).

What not to do

Do not let anyone climb in to pump out or "have a quick look" before the inspection, and do not assume a support system is still adequate after saturation. Do not ignore softened or cracked ground at the top edge, spoil heaps near the edge, or water still entering. Do not treat the start-of-shift inspection as optional because it was inspected yesterday.

Who is responsible

The principal contractor and site management control access and coordinate the response; the competent person carries out and records the inspection; the temporary works arrangements (and designer where the support is designed) inform whether the system is still adequate. Operatives must not enter until re-entry is authorised.

Evidence and records

Record the rainfall event, the exclusion, the competent-person inspection and its report (as required by CDM 2015 for excavations that could collapse), any dewatering or remediation, the support review, and the authorised re-entry with time and person. Keep the inspection reports with the site records so the decision trail is complete.

Escalation

Escalate an unsafe excavation to competent temporary works or geotechnical advice and keep it closed until remediated. Where the ground change affects lifting or plant near the edge, coordinate with the lift-plan re-approval after a ground change, and where support details are in question see trench support and ground conditions. A near-collapse or injury may be reportable under RIDDOR.

Prevention

Plan for weather: build start-of-shift and post-event inspections into the method, protect excavations from surface water, keep spoil and plant back from the edge, and have dewatering and support contingencies ready. A method that expects rain and defines the re-entry check turns a wet morning into a controlled decision rather than a gamble.

Where Complys can help

Complys can hold the site's excavation inspection records, method statements and action log, and keep the post-event inspection and re-entry decision trail together. It does not inspect excavations or judge ground stability; a competent person does. Ask the Complys team to show how site inspections and records are tracked.