Residential Construction Excavation Safety Requirements

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Residential Construction Excavation Safety
Requirements
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Objectives

• Review excavation hazards
• Discuss Soil Classifications
• Define Competent Person Responsibilities
• Overview of Protective Systems
• Discuss Residential Requirements
• Safe Work Practices

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Injury and Death

• Excavating is one of the most hazardous
  construction operations
• Most accidents occur in trenches 5-15 feet deep
• Can fail from the top or bottom, there is usually
  no warning before a cave-in.

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Fatality Statistics
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Soil (depending upon rock and water content)
weighs around 2700 pounds per cubic yard (3x3x3)
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Excavation Hazards

• Cave-ins are the greatest risk
• Moving machinery near the edge of the excavation
  can cause a collapse
• Accidental severing of underground utility lines
  or aboveground contact with power lines

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Other Excavation Hazards

• Water accumulation
• Oxygen deficiency
• Toxic fumes or vapors
• Access/Egress
• Falls
• Mobile equipment struck by or roll-over

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Competent Person

• Must have had specific training in and be
  knowledgeable about
• Soils classification
• The use of protective systems
• The requirements of the standard
• Must be capable of identifying hazards, and
  authorized to immediately eliminate hazards

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Site Evaluation Planning

• Before beginning excavation
• Evaluate soil conditions
• Construct protective systems
• Test for low oxygen, hazardous fumes and toxic
  gases
• Provide safe in and out access
• Contact utilities
• Determine the safety equipment needed
• Determine Protective System

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Protection of Employees

• Employees should be protected from cave- ins by
  using an adequately designed protective system
• Protective systems must be able to resist all
  expected loads to the system

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Unprotected Worker

• This worker is in a trench with no protective
  system, that is not sloped or benched and has no
  means of egress.

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What is the difference?

• Excavation a man-made cut, cavity, trench, or
  depression formed by earth removal.
• Trench a narrow excavation. The depth is
  greater than the width, but not wider than 15
  feet.

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Soil Classification

• Stable Rock
• Type A clay, silty clay, clay loam.
• Type B angular gravel, silt, silt loam, sandy
  loam.
• Type C Granular soils includes Gravel, Sand
  and Loamy sand or submerged soil from which
  water is freely seeping.

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Soil Classifcation

• Based on the result of one visual and one manual
  analysis.
• Visual analyses includes observation of
  excavated soil and soil on sides of excavation,
  identify and sources of vibration and look for
  evidence of water.
• Manual analyses includes test to determine
  plasticity, dry strength, unconfined compressive
  strength (thumb penetration penetrometer,
  torvane) and a drying test 24 hour requirement.

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Protect employees exposed to potential cave-ins
by

• Sloping or benching the sides of the excavation,
• Supporting the sides of the excavation, or
• Placing a shield between the side of the
  excavation and the work area

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Allowable Slopes
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Sloping for Type C soil
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Soil Can Be Layered!
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Benching
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Hydraulic Trench Support

• Using hydraulic jacks the operator can easily
  drop the system into the hole
• Once in place, hydraulic pressure is increased to
  keep the forms in place
• Trench pins are installed in case of hydraulic
  failure

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A trench box is a shield
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Other excavation hazards

• Struck by hazards
• Contact with underground/aboveground utilities
• Accumulating water
• Falls

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Struck By Hazards

• Moving machinery
• Dropped buckets
• Dropped materials
• Traffic

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NIOSH Study

• National Institute for Occupational Safety and
  Health (NIOSH)Identified 346 deaths associated
  with excavators or backhoe loaders during
  19922000
• Review of these data and of NIOSH Fatality
  Assessment and Control Evaluation (FACE) cases
  NIOSH 2000,
• 2001 suggests two common causes of injury
• (1) being struck by the moving machine, swinging
  booms, or other machine components or
• (2) being struck by quick-disconnect excavator
  buckets that
• unexpectedly detach from the excavator stick.
• Other leading causes of fatalities are rollovers,
  electrocutions, and slides into trenches after
  cave-ins.

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Quick-disconnect excavator bucket that detached
from the excavator stick
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Swing Radius

• The swing radius of crane is highly regarded as a
  safety hazard since workers can be hit by, or
  caught by, the body of the crane as it swings
  into position.
• Excavating equipment (especially hydraulic
  excavators) operate and look very similar to
  cranes.
• Before starting to dig, set up safety barriers to
  the sides and rear area of your swing pattern to
  prevent anyone from walking into the walking area

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Swing Radius
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Swing Radius

• Lifting equipment and loads over the heads of
  employees is not a safe work practice.
• Conduct hazard awareness training - warn workers
  of the hazards.
• Barricade the area around the excavator.
• Extending a hardened warning line system
  connected to the track-hoe/excavator and extended
  from the machine, covering the distance of the
  swing radius (this will prevent workers form
  entering the area around the excavator, even if
  the excavator was moving).

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a 21-year-old male construction laborer was
fatally injured when a backhoe fell into the
excavation in which he was working.
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Working in Traffic

• Employees exposed to public vehicular traffic
  shall be provided with, and shall wear, warning
  vests or other suitable garments marked with or
  made of reflectorized or high visibility material.

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Protection from Vehicles

• Install barricades
• Hand/mechanical signals
• Stop logs
• Grade soil away from excavation
• Fence or barricade trenches left overnight

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Utility Protection

• Prior to opening an excavation the estimated
  location of all utilities must be determined
  (i.e., sewer, phone, fuel, electric, water lines,
  or any other installations that may reasonably be
  expected to be encountered during the work).

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Utility Locations
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Water

• Employees shall not work in excavations in which
  there is accumulated water

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Water

• When water is present in an excavation it is
  extremely hazardous to enter

Note that these workers are not wearing hardhats
to protect them from materials falling into the
trench
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Protection from Falls, Falling Loads, and Mobile
Equipment

• Install barricades
• Use hand / mechanical signals
• Grade soil away from excavation
• Fence or barricade trenches left overnight
• Use a flagger when signs, signals and barricades
  are not enough protection

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Means of Egress
This ladder does not meet the requirements of the
standard

• A stairway, ladder, or ramp must be present in
  excavations that are 4 or more feet deep, and
  within 25 feet of the employees

The ladder should extend 3 feet above the
excavation
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Access and Egress
These two ladders which are lashed together are
not an adequate means of egress The ladder should
extend 3 feet above the top of the excavation
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If fall distance is greater than 6 feet, guard
rails are required
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Spoils

• Dont place spoils within 2 feet from edge of
  excavation
• Measure from nearest part of the spoil to the
  excavation edge
• Place spoils so rainwater runs away from the
  excavation
• Place spoil well away from the excavation

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Residential Construction Exemption

• Suspension of 29 CFR 1926.652 to House
  Foundation/Basement Excavations
• Protection of employees in excavations shall not
  be applied to house foundation/basement
  excavations when all the following conditions are
  present

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Protection of employees in excavations shall not
be applied to house foundation/basement
excavations when all the, following seven
conditions are present

• The depth of the foundation/basement trench
  cannot exceed 7½ feet deep unless you provide
  other cave-in protection.
• The minimum horizontal width (excavation face to
  formwork/wall) at the bottom of the excavation is
  as wide as practicable but not less than two (2)
  feet.

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Protection of employees in excavations shall not
be applied to house foundation/basement
excavations when all the, following seven
conditions are present

• 3. There is no water, surface tension cracks, nor
  other environmental conditions present that
  reduce the stability of the excavation
• 4. There is no heavy equipment operating in the
  vicinity that causes vibration to the excavation
  while employees are in the excavation

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Protection of employees in excavations shall not
be applied to house foundation/basement
excavations when all the, following seven
conditions are present

• 5. All soil, equipment, and material surcharge
  loads are no closer in distance to the top edge
  of the excavation than the excavation is deep
  however, when front end loaders are used to dig
  the excavations, the soil surcharge load shall be
  placed as far back from the edge of the
  excavation as possible, but never closer than two
  (2) feet.

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Protection of employees in excavations shall not
be applied to house foundation/basement
excavations when all the, following seven
conditions are present

• 6. Work crews in the excavation are the minimum
  number needed to perform the work and
• 7. The work has been planned and is carried out
  in a manner to minimize the time employees are in
  the excavation.

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Protection of employees in excavations shall not
be applied to house foundation/basement
excavations when all the, following seven
conditions are present

• The requirements for a competent person are
  unchanged.
• Applies to all soil types.
• Ancillary work such as waterproofing is covered
  by the memorandum.
• Applies to
• below grade concrete stairs and
• underground heating oil tank and
• conduit installations
• adjacent to foundations of new houses
• when the excavations for such are dug at the same
  time as the foundation excavation is dug for the
  house.

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Residential Excavation of Foundation
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Moving Equipment

• Employees shall not be permitted underneath loads
  or near vehicles being loaded or unloaded.
  Operators may remain in properly equipped vehicle
  cabs for protection during loading and unloading
  operations.

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Work Practices

• Keep workers away from digging equipment and
  never allow workers in an excavation when
  equipment is in use.
• Keep workers from getting between equipment in
  use and other obstacles and machinery that can
  cause crushing hazards.

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Utility Protection

• Contact utility companies or OUPS
  (1-800-362-2764) to establish the location of
  underground installations.

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Cave-in Hazard
This excavation has inadequate support posts and
egress access
Inadequate protective system
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Inadequate Protective System

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Shoring

• General
• Provides a framework to work in
• Uses wales, cross braces and uprights
• Supports excavation walls
• OSHA tables provide shoring data
• Must know soil type
• Must know depth and width of excavation
• Must be familiar with the OSHA Tables

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Trench Shield

• A trench shield was built around this work area

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Hazardous Atmosphere

• Test excavations more than 4 feet before an
  employee enters the excavation for
• Oxygen deficiency
• High combustible gas concentration
• High levels of other hazardous substances

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Trench Water Cave-in Hazard
These workers must be protected from cave-in.
Note the water in the bottom of the trench.
This is a very hazardous condition!
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Where Can I Find The Regulations?

• 29 CFR 1926 Subpart P - Consists of the
  following
• 1926.650 -Definitions
• 1926.651 - Excavation Requirements
• 1926.652 - Requirements for Protective Systems
• And...

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Factors Involved in Designing a Protective System

• Soil classification
• Depth of cut
• Water content of soil
• Changes due to weather and climate
• Other operations in the vicinity

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Regulations

• Appendix A - Soil Classifications
• Appendix B - Sloping and Benching
• Appendix C - Timber Shoring for Trenches
• Appendix D - Aluminum Hydraulic Shoring for
  Trenches
• Appendix E - Alternatives to Timber Shoring
• Appendix F - Selection of Protective Systems

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• Trenching accidents on U.S. construction sites
  account for an estimated 100 fatalities per year.
• The fatalities account for nearly 1 of all work
  related deaths in the United States.

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• Trench
• A narrow excavation made below the surface of
  the ground in which the depth is greater than the
  width-the width not exceeding 15 feet.

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Excavation

• Any man-made cut, cavity, trench, or depression
  in the earths surface formed by earth removal.
  This can include excavations for anything from
  cellars to highways.

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Sloping

• A method of protecting employees from cave-ins by
  excavating to form inclined sides away from the
  excavation to prevent cave-ins.
• The incline angle required to prevent a cave-in
  varies with soil type, environmental conditions
  of exposure, and application of surcharge loads.

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• Where soils are configured in layers.
• When this exists, the soil must be classified on
  the basis of the soil classification of the
  weakest soil layer.
• Each layer may be classified individually if a
  more stable layer lies below a less stable layer,
  i.e., where a Type C soil rests on top of stable
  rock.

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Benching

• A method of protecting employees from cave-ins by
  excavating the sides of an excavation to form one
  or a series of horizontal levels or steps,
  usually with vertical or near-vertical surfaces
  between levels.

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• Registered Professional Engineer (PE) is a
  person registered as a PE in the state where the
  work is to be performed. However, a PE,
  registered in any state is deemed a registered
  professional engineer when approving designs for
  manufactured protective systems or tabulated
  data to be used in interstate commerce.

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• Accepted engineering practices are requirements
  that are comparable with standards of practice
  for a registered professional engineer.

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• Requirements for Protective Systems
• Each employee in an excavation shall be
  protected from cave-ins by an adequate protective
  system except when
• Excavations are made entirely in stable rock or
• Excavations are less than 5 feet in depth and
  examination of the ground by a competent person
  provides no indication of a potential cave-in.

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Protective Systems

• Methods of protecting employees from cave-ins
  from material that could fall or roll from an
  excavation face or into an excavation or from
  the collapse of adjacent structures.
• They include sloping and benching systems,
  shield systems, and other systems that provide
  the necessary protection.
• They must have the capacity to resist without
  failure all loads that are intended or could
  reasonably be expected to be applied or
  transmitted to the system.

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• The requirements for a competent person are
  unchanged by the memorandum.

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• Uprights
• Vertical members of a trench shoring system
  placed in contact with the earth and usually
  placed so that individual members do not contact
  each other. Uprights closely spaced, in contact
  with or interconnected to each other, are often
  called sheeting.

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Hazardous Conditions
The weight and vibrations of the crane make this
a very hazardous condition. They should not be
working under this crane.
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• Wales
• Horizontal members of a shoring system placed
  parallel to the excavation face whose sides bear
  against the vertical side members of the shoring.

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• Crossbraces
• Horizontal members of a shoring system installed
  perpendicular to the sides of the excavation, the
  ends of which bear against either uprights or
  wales.

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• Aluminum Hydraulic Shoring
• A pre-engineered shoring system comprised of
  aluminum hydraulic cylinders (cross braces) used
  in conjunction with vertical rails (uprights)
  and/or horizontal rails (walers). Such system is
  designed, specifically to support the sidewalls
  of an excavation and prevent cave-ins.

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• Shields
• Shield (shield system) a structure able to
  withstand cave -in forces imposed on it and
  protecting the employees inside
• Can be permanent structures or can be designed
  to be portable and moved along as work
  progresses
• Can be either pre-manufactured or job-built in
  accordance with 1926.652 (c)(3) or (c)(4)
• Shields used in trenches are usually referred to
  as trench boxes or trench shields.

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Materials and Equipment

• Equipment used for protective systems must not
  have damage or defects that impair function.
• If equipment is damaged, the competent person
  must examine it to see if it is suitable for
  continued use.
• If not suitable, remove it from service until a
  professional engineer approves it for use.

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Inspections of Excavations

• A competent person must make daily inspections
  of excavations, areas around them and protective
  systems
• Before work starts and as needed,
• After rainstorms, high winds or other occurrence
  which may increase hazards, and
• When you can reasonably anticipate an employee
  will be exposed to hazards.

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Inspections of Excavations

• If the competent person finds evidence of a
  possible cave-in, indications of failure of
  protective systems, hazardous atmospheres, or
  other hazardous conditions
• Exposed employees must be removed from the
  hazardous area
• Employees may not return until the necessary
  precautions have been taken

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The End

• Every reasonable effort has been made to prepare
  this document using the most current, correct,
  and clearly expressed information possible.
  However, inadvertent errors may occur. The Ohio
  OSHA On-Site Consultation Program disclaims any
  responsibility for typographical errors and the
  accuracy of the information contained in this
  document. The information and data included in
  this document have been compiled by the Ohio OSHA
  On-Site Consultation staff from a variety of
  sources that are subject to change without
  notice. The Ohio OSHA On-Site Consultation
  Program makes no warranties or representations
  whatsoever regarding the quality, content,
  completeness, suitability, adequacy, sequence,
  accuracy, or timeliness of such information and
  data.