TRENCH OPERATIONS

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TRENCH OPERATIONS

• For safety is not a gadget but a state of mind. 
  Eleanor Everet

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Objectives

• Governing Standards
• Anatomy of a Trench
• Soil Physics
• First arriving units actions/ Scene management
• Equipment Familiarization
• Type of Trench Collapses
• Techniques for Protection

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OSHA CFR 1926 Subpart P, Excavation

• Important to rescuers for several reasons
• First the data and information will give you the
  information from which you can decide the
  protective systems.
• Secondly, knowledge of the standard, its
  requirements, protective systems, and soil
  classifications will qualify the user as a
  Competent Person.

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General requirements

• All trenches must be protected before entries
  except
• Those made entirely of stable rock.
• Those less than five feet in depth, including the
  height of the spoil pile must be protected.
• Protection
• Anything more than five feet in depth, including
  the height of the spoil pile must be protected.
• Spoil Pile
• Must have two-foot set back for the lip.
• Egress
• Trenches four feet or greater in depth must have
  a means of egress every twenty-five feet
  Ladders.
• Atmospheric
• Trenches four feet or greater in depth must be
  tested before entry.

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Definitions

• A trench, means a narrow excavation (in
  relation to its length) made below the surface of
  the ground. In general, the depth is greater
  than the width, but the width measured at the
  bottom is not greater than 15 feet.

WIDTH DEPTH
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Excavation, includes a trench

• It means any man made cut, cavity, trench,
  or depression in an earth surface formed by the
  earths removal. Again, in practical terms, when
  a hole is more than 15 feet wide at its base, it
  is called specifically an excavation. Overall,
  an excavation is wider than it is deep.

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Competent Person

• One who can identify existing or predictable
  hazards in the surrounding that are unsanitary,
  hazardous, or dangerous to employees. Also has
  authorization by the nature of their position to
  prompt corrective measures to eliminate them. The
  person shall be knowledgeable in the requirement
  of this part.

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Anatomy
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How Heavy is Dirt?

• Physical forces associated with collapse
• Dirt has volume that has mass and weight
• One cubic foot of dirt weights between 85 and 125
  pounds per cubic foot.

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Soil Physics

• Compounding the effects of gravity is hydrostatic
  pressure
• Add the weight of water and rock, a cubic foot of
  dirt can be as much as 125 pounds per cu/ft

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• A six foot trench
• at the four foot level has approximately 400
  pounds vertical pressure
• Lateral forces could be expected to be 132 pounds
• Distribution of lateral pressure occurs on about
  a 45 degree angle from the bottom

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Accidents without cave-ins

• Most emergencies in trenches deal with something
  other than a collapse
• Most of the work is done after the trench has
  been dug
• In these cases dont be lulled to sleep by a
  protected trench
• Approach identically as an open trench

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Hazards Present?
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First Arrival

• Apparatus spotting
• Spot at least 100 ft from location
• Create Exclusion Zones (on next slide)
• Size-up accurate address of location, call for
  help
• Secure RP, job foreman, or witness to accident
• Safety 360 Review approach trench from the end,
  Secondary size-up
• Rescue or Recovery mode
• Assess potential hazards to rescuers
  (Atmospheric, water,Trench etc)
• Make The Trench Lip Safe ground pads/ Ladder
  bridges
• Shielding of patient with material on site,
  plywood, backboard
• Air monitoring Bottom at patient, middle and
  top of trench
• Apparatus Base Area with manager. location?

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Trench Scene Management
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Ground pads

• For distribution of weight on trench edge

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Ladder Bridge
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Review of Monitoring Values
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Equipment Familiarization

• Strongbacks/Uprights Shoring Panels
• Yates Spec Pack
• Waler
• Palm nailer
• Airshore
• Speedshore

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Types of Collapses

• Spoil pile slide
• Excavated earth too close to the lip
• Heavy rain increasing wt of pile

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Slough In / Lip slide

• Slough failure
• The loss of part of the trench wall

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Sheer Wall

• Shear wall collapse
• section of soil that loses its ability to stand

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Toe Failure

• Toe failure
• Slough that occurs at the bottom
• Found in location of fill dirt

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Bell Pier Condition

• Bell pier condition
• Long term toe failure on both sides

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Rotational Failure

• Rotational failure
• Scoop shaped collapse that starts at the lip and
  transmits itself to the trench walls

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Wedge Failure

• Wedge failure
• Occurs with intersecting trenches, T or L Trench
• Angled section of earth falling from the corner
  of an intersecting trench

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TECHNIQUES FOR TRENCH PROTECTION
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TECHNIQUES FOR TRENCH PROTECTION
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TECHNIQUES FOR TRENCH PROTECTION

• Ops operating within trench
• Straight wall trench procedures
• Set middle set of panels as directly over the
  victim as possible
• For Pneumatic Struts
• Set middle shore
• Set top shore
• Set bottom shore

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Outside Waler

• Uses outside walers to span opening
• Outside waler procedures
• Place pickets to tie walers
• Place and tie off bottom of Waler
• Place and tie off top of Waler
• Set middle set of panels as directly over victim
  as possible

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Inside Waler

• Inside walers are used to span a set of panels
  for the purpose of creating an open space

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• The intersecting T trench is a very unstable
  trench because not only is one wall exposed, but
  a section has been cut that intersects the other
  wall.

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• The L trench can be describe as two trenches
  that intersect at there ends

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• Deep trenches are those trenches over 10 feet
  but not more than 20 feet

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Pier-hole
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Trench Environments
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