Excavation
Any dug hole, trench or pit, controlled under CDM against collapse, falls, striking services, water and contamination, and inspected at the start of every shift.
CDM 2015 requires that excavations be prevented from collapsing by supports or battering, that people cannot fall into them, that material and plant cannot fall in, and that they be inspected by a competent person at the start of every shift, after any event likely to affect stability, and after any fall of material, with the inspection recorded. There is no minimum depth in the regulations; a metre of trench can kill when it collapses, because a cubic metre of soil weighs more than a tonne and the person is face down under it.
Before digging, the permit-to-work process covers the other killers: locating buried services with drawings, a cable avoidance tool and a signal generator, hand-digging trial holes near marked services, and treating every service as live; ground conditions and water; contamination; and the stability of adjacent structures. Trench boxes, drag boxes, hydraulic shoring and battering at a safe angle are the collapse controls. Edge protection, barriers, ladders for access and stop blocks for plant complete the picture.
Where it comes from
- Construction (Design and Management) Regulations 2015 reg.22 (excavations) and Schedule 3 (inspections).
- HSE guidance HSG47 (Avoiding danger from underground services) and HSG185 (Health and safety in excavations).
Questions people ask
How deep before I need shoring?
There is no depth in the regulations. The test is whether collapse is reasonably foreseeable, which for most soils it is from about 1.2 metres, and for poor ground, wet ground or ground next to a previous dig, much less. Assess each one and support or batter accordingly.
How often must an excavation be inspected?
At the start of every shift in which people will work in it, after any event likely to affect it (rain, a vehicle passing close, a fall of material), and the record of the start-of-shift inspection kept. Weekly is not enough.
Excavation, handled on a phone
SiteLynx puts the RAMS, permits, inspections, audits, plant checks and records behind every term in this glossary on the crew's phones, signed on site, with a PDF at the end. 14 days free, no card.
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