Environmental Health & Safety

Excavation Safety

January 2010OSHA CFR 1926.650
  • Retraining is required every 3 years
  • Applies to all open excavations, including trenches
  • Soil Classification
  • Sloping and Benching
  • Timber Shoring and Trenches
  • Aluminum Hydraulic Shoring
  • Alternative Timber Shoring
  • Selective Protective Systems
  • May require the services of a Registered Professional Engineer

Excavation

Definitions

Benching / Bench System - One or a series of horizontal levels or steps, with vertical or near-vertical surfaces between levels.

Competent Person - Person who is capable of identifying existing and predictable hazards or working conditions, and that has the authority to correct or eliminate them.

Excavation - A cut, cavity, trench or depression that was made be a person into the earth’s surface, through the removal of the earth .

Faces / Sides - Vertical or inclined earth surface formed by excavation work.

Hazardous Atmosphere - A location that is or has the potential to be hazardous from an explosive, fire or IDLH standpoint.

  • Sewer Gas / Carbon Monoxide / Oxygen Deficient

Protective System - A system to protect employees from cave-ins, collapse, or from material or equipment falling in to.

  1. Support Systems
  2. Sloping
  3. Benching
  4. Shield Systems
  5. Guardrails
  6. Warning Barriers

Sheeting - Members of a shoring system that retain the earth in position, and are also supported by other members of the shoring system.

Shield/Trench Box - A structure that is capable of withstanding forces that may be imposed by faces and walls of an excavation to properly protect the occupants of the excavation.

Shoring - A metal hydraulic, mechanical or timber shoring system that supports the side of an excavation.

Sloping - Inclined faces and walls of an excavation, excavated in such a fashion to properly protect the occupants of the trench.

  • Angle is dependent on soil type and disturbance.

Stable Rock - Solid mineral material that can be excavated with vertical sides, and will remain in tact while exposed.

Wales vs. Bracing - Horizontal members of a shoring system placed parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth.

Dig Safe Notification Notification Required

No excavator installing a new facility, an addition to an existing facility, or repairing of an existing facility shall make an excavation in...
  1. Any public or private way
  2. Any company right of way or easement
  3. Any public or privately owned land or way
  4. Until the appropriate Dig Safe Permit is acquired.

General Duty Clause - Section 5 (a) (1)

“ Each employer shall provide a place of employment which is free from recognized hazards that would cause or is likely to cause death or serious physical harm to their employees.”
- Section 5 (a) (2)

Excavations - Open

When open…
  • All underground installations shall be protected, supported or removed to best protect the employee
  • Barricades, Guardrails and Warning Lines shall be provided to identify the hazardous area
  • Means of Egress
  • All trenches (>4’) shall be provided with a “means of egress” that is accessible to an employee within 25’.
  1. Ladder
  2. Ramp
  3. Stairway
  4. Vehicular Traffic
  • Employees must be properly protected from vehicular traffic by one or more of the following;
  1. Barricades set-up in a manner that properly warns vehicle operators of personnel in close proximity to the excavation.
  2. Signage (i.e. Personnel in Roadway etc.)
  3. Wearing of Warning Vests or, Reflecterized Garments
  4. Adequate and appropriate lighting in accordance with DOT requirements

Spoils

  • Must be located > 36” from edge of trench or excavation
  1. Exception - Toeboards or other suitable barricade is used.
  2. Boulders, Stumps and other material that could roll into the trench must be removed.

Personnel Hazards

  • No employee shall be permitted near or beneath loads handled by excavation equipment.
  1. They must be located away from the vehicle being loaded or unloaded, so as not to be struck by falling debris.
  2. In all construction areas where there is an overhead hazard, the appropriate personal protective equipment shall be worn.
  3. Operators of vehicles receiving the loads can remain in the cab of the vehicle, provided with proper overhead protection.

Warning Systems

  • If mobile equipment is operated adjacent to an excavation, or if required to approach, the operator must have clear view, or shall have a warning system consisting of…
  1. Barricades
  2. Hand or Mechanical Signals
  3. Stop logs
  4. Other suitable Warning Devices

Hazardous Atomospheres  

Testing Requirements

Potential or Known Hazards

  • Excavations > 4’

4 Gas Monitors

  • Lower Explosive Level (LEL)
  • Carbon Monoxide (CO)
  • Hydrogen Sulfide (H2S)
  • Oxygen Deficiency or Enrichment (O2)

Ventilation Modifications

Hot Work Activities

Hazardous Locations

Water

  • In the excavation
  • Entering into the excavation, or
  • Storm potential that could result in cave-ins

Precautions / Mitigations

  • Shielding
  • Pumping
  • Use of Personal Protective Devices

Surface Water - Drainage

Should excavation interrupt water flow...

  • Precautions shall be taken to prevent entry into excavation.
  • Stormwater Protection Devices and Materials.
  • Barricades, Dikes, Fabric Fences, etc.
  • Erosion Control Devices.

Structure Stability

If integrity of a building, facility or structure is in question, the employees must be protected with...
Support Systems
  • Bracing
  • Shoring
  • Underpinning
  • Registered Professional Engineer
Sidewalks, pavement, structures shall not be undermined unless a support system or other suitable method of protection has been set up
  • Registered Professional Engineer and Manufacturers Specifications

Inspections

Competent Person
  • Must be performed DAILY
  • Prior to work
  • As needed throughout the shift
  • Shall include adjacent areas and protective systems
  • Possibility of Cave-In?
  • Failure of Protective Systems
  • Known or Potential Hazardous Atmospheres
  • Hazardous Conditions
  • Rain storms or water run-off

Fall Protection

Walkways around, excavations and/or hazardous equipment shall be properly guarded.
  • Guardrails shall comply with OSHA
  • Top and mid-rails with appropriate toeboards
  1. Top Rail = 36 – 42” in height
  2. Potential for falling objects into trench
  3. 200 lb down and outward force

Physical Protection

Pits, shafts and wells can be covered.
  • Must be able to withstand (4x) heaviest potential load.

Excavation Slopes

  • Excavations can not be sloped at an angle steeper than 1 : 1 ½ (horizontal to vertical) or 34 degrees.
  • Sloping or Benching shall follow appropriate standards, using tabulated areas from tables and charts
  • If the depth of excavation is > 20’
Registered Professional Engineer
  • Copies of tabulated data which identifies the engineer
  •  Log of all test results should be maintained on the work site
  • Located on the job site, during construction of the Protective System

Shields

Trench Boxes
  • Must be restricted from lateral or other hazardous movement.
  • Must adequately and properly protect employees.
  • Can not be moved, placed or removed in the excavation if employees are located within the trench.
  • Shields can be moved, in place of using shoring, provided no employee is in the excavation.

Soil Classification

Type A
  • Cohesive Soil
  • Clay, Silty Clay, Clay Loam, Cemented Soils and Hardpan
  • No soil is Type A, if…
  1. It is fissured
  2. Been subjected to vibration
  3. Previously disturbed
Type B
  • Granular, cohesionless soil, like crushed rock, silt, silt loam
  • Previously disturbed Type A
  • Fissured or subjected to vibrartion
Type C
  • Granular soils, sand or soil with free seeping water

Employee Safety

  • Employees are not permitted to work on faces or walls of a sloped or benched excavation at levels above other employees.
Exception
If employees at lower levels are properly protected from falling, rolling, sliding material or equipment
Exception to the Exception
Equipment above the excavation making the slope or trench