Cave-ins of a trench or excavation can be fatal. Certain steps must be taken to minimize this risk.
Excavation: any man-made cut, cavity, trench or depression in the earth's surface formed by earth removal
Trench: narrow underground excavation with depth > width AND width <= 15 feet.
Requirements:
(1) A protective system must be in place if a trench is >= 5 feet deep unless entirely in stable rock.
(2) A trench > 20 feet must have a protective system prepared/designed/approved by a registered professional engineer.
(3) The soil and ground conditions where the excavation will occur must be analyzed in advance.
(4) A competent person must inspect the trench daily and as conditions change that affect trench stability (rain, blasting, heavy vibrations, etc) or introduce hazardous conditions.
(5) There must be a safe means of access into a trench or excavation >= 4 feet. Every worker should be within 25 feet of a means of exit.
(6) Heavy equipment should be kept away from the edge of the trench.
(7) All surcharge loads (material removed from the trench) and building materials should be >= 2 feet from the edge of the trench.
(8) Any underground utilities should be located and secured before digging.
(9) The atmosphere in the trench should be monitored for hazardous gases and reduced oxygen.
(10) Caution should be used if the ground is wet or water has accumulated in the trench.
(11) Workers should not be present under suspended or raised loads.
(12) Fall protection should be in use for workers near the edge of the trench.
(13) Workers should wear high-visibility clothing is exposed to vehicular traffic.
(14) A harness with lifeline should be used when appropriate (bell-bottom pier hole; other deep and confined footing excavation.
Protective systems may include:
(1) sloping suitable for the soil and weather conditions
(2) shoring
(3) trench box or other form of shielding
