Excavation safety is critical and involves several key aspects. Here's a breakdown of important considerations:

1. Definitions: An excavation is any man-made cut, cavity, trench, or depression in an earth surface formed by earth removal 1, 3. A trench is a narrow excavation where the depth is generally greater than the width, and the width at the bottom is no more than 15 feet (4.6 m) 6, 11.

2. Protective Systems: These are crucial for protecting employees from cave-ins and materials falling into the excavation 1, 2. Protective systems include support systems, sloping and benching systems, and shield systems 1, 2.

3. Competent Person: A competent person must be able to identify existing and predictable hazards and have the authority to take corrective measures 3, 7. Daily inspections of excavations, adjacent areas, and protective systems must be conducted by a competent person [1].

4. Underground Installations: Before excavating, the estimated location of utility installations (sewer, telephone, fuel, electric, water lines, etc.) must be determined [2]. Utility companies should be contacted to establish the exact location of these installations [2]. If they cannot respond within 24 hours, proceed with caution using detection equipment [2].

5. Hazardous Atmospheres: Precautions must be taken to prevent employee exposure to hazardous atmospheres, including providing proper respiratory protection or ventilation [3]. Emergency rescue equipment, like breathing apparatus, safety harnesses, and basket stretchers, should be readily available where hazardous atmospheric conditions exist 5, 17.

6. Water Accumulation: Employees should not work in excavations with accumulated water unless adequate precautions are taken, such as special support or shield systems, water removal, or safety harnesses and lifelines 5, 17. If water removal equipment is used, it should be monitored by a competent person 5, 17.

7. Stability of Adjacent Structures: If excavation operations endanger the stability of nearby buildings or walls, support systems like shoring, bracing, or underpinning must be provided 5, 20.

8. Protection from Falling Materials: Provide adequate protection from loose rock or soil that could fall from an excavation face, using scaling or protective barricades 12, 20. Materials or equipment should be kept at least 2 feet (.61 m) from the edge of excavations or use retaining devices 12, 20.

9. Specific Requirements: For trenches more than 1.2 meters deep, workers must be protected from cave-ins by cutting back the walls, installing a temporary protective structure, or a combination of both [4]. In some regions, a professional engineer must design and certify temporary protective structures for excavations deeper than 3 meters [4].

10. Shoring: Shoring should be installed and removed in a manner that protects workers from cave-ins and structural collapses [4]. Shoring components must be securely connected to prevent sliding, falling, or kickouts [4].

11. Access and Egress: Ladders, stairways, or ramps should be installed to provide a safe means of entrance to and exit from the trench, located no more than 8 meters from a worker in the trench [5].

12. Equipment: Ensure that the open side of an excavation or a route used by powered mobile equipment has a barrier to prevent equipment from sliding or rolling into the excavation [6].

13. Material Placement: Excavated material must be kept at least 1 meter from the edge of the excavation or trench [7].

14. Atmospheric Testing: Where an employee may be exposed to a hazardous gas or oxygen-deficient atmosphere in an excavation or trench, testing must be carried out before the employee enters [8].