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TRENCH OPERATIONS

TRENCH OPERATIONS. For safety is not a gadget but a state of mind.  ~ Eleanor Everet. Objectives. Governing Standards Anatomy of a Trench Soil Physics First arriving units actions/ Scene management Equipment Familiarization Type of Trench Collapses and Recognize hazards

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TRENCH OPERATIONS

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  1. TRENCH OPERATIONS For safety is not a gadget but a state of mind.  ~ Eleanor Everet

  2. Objectives • Governing Standards • Anatomy of a Trench • Soil Physics • First arriving units actions/ Scene management • Equipment Familiarization • Type of Trench Collapses and Recognize hazards • Assignments & Responsibilities • Techniques for Protection

  3. Understand what is required to manage a Trench Rescue Incident • Provide tools to enable the student in making safe and effective decisions during a trench rescue incident • Implement the Incident Management / Accountability System

  4. NFPA 1670 • REQUIREMENTS FOR OPERATIONS AND TRAINING • AWARENESS Level Functions • Size-up of existing and potential conditions • Development & implementation of procedures for carrying out an emergency response system • Site Control & Scene Management • Recognition of hazards and procedures to mitigate these hazards

  5. NFPA 1670 OPERATIONAL LEVEL FUNCTIONS • Develop & Implement procedures: • To make entry • Shoring in non-intersecting trenches > 8 feet • To identify probable victim location • For making the rescue area safe • For initiating a one-call utility location service • To ventilate the trench or excavation • Placing ground pads & protecting the lip • To provide entry and egress paths • For conducting a pre-entry briefing • For record keeping • For utilizing a RIT • …other responsibilities!

  6. 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”.

  7. 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.

  8. 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

  9. ”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.

  10. 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.

  11. Anatomy

  12. 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.

  13. Weight of one cubic yard of soil Weight of a Volkswagen 2,785 Pounds 2,700 Pounds

  14. 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

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

  16. Types of Worker Protective Systems • Sloping • Benching • Shielding • Shoring • Determined by • Soil class • Work space required • Economic factors

  17. Sloping and benching

  18. Trench Shield / Trench Box • Shields are manufactured by a number of companies and are designed to protect workers working within the confines of the shield. • Check tabulated data for the maximum allowable depth it can be used. The tabulated data must accompany the shield when it is being used. • Additionally, the shield must be designed by a Registered Professional Engineer, be in good condition, and used properly.

  19. Shoring • Shoring is one of the most common used methods of worker protection. It is light-weight, portable and easy to install. • The manufacturer provides tabulated data with the shoring that provides the limitations, precautions, required spacing and proper use. This photo shows an example of aluminum hydraulic shoring.

  20. 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 don’t be lulled to sleep by a protected trench • Approach identically as an open trench

  21. What makes trenches hazardous?

  22. Hazards Present?

  23. Most deaths occur in trenches 5 ft. to 10 ft. in depth and 6 ft. wide. 90% of fatal accidents occurred in trenches less than 20’ deep

  24. First Arrival • Apparatus spotting • Spot at least 100 ft from location • Create Exclusion Zones (on next slide) • Size-up – accurate address of location, length, width and depth of trench, number of victims, length of time from collapse, call for help • Secure RP, job foreman, or witness to accident • Safety 360 Review – approach trench from the end, Secondary size-up • Conduct Risk-to-benefit analysis • 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?

  25. Hot Zone 0 – 100 ft. Warm Zone 100 – 150 ft Cold Zone 150 – 300 ft. Trench Scene ManagementExclusion Zones

  26. Ground pads • For distribution of weight on trench edge

  27. Ladder Bridge

  28. Review of Monitoring Values

  29. Equipment Familiarization • Strongbacks/Uprights = Shoring Panels • Timber • Waler • Palm nailer • Airshore • Speedshore

  30. Shoring Concept Works by creating “double funnel effect” Strong enough to prevent soil from starting to move set in four feet intervals vertically and horizontally as a general rule. Strut pressurizes trench wall in all directions

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

  32. Slough In / Lip slide Slough failure • The loss of part of the trench wall

  33. Sheer Wall Shear wall collapse • section of soil that loses it’s ability to stand

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

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

  36. Bell Pier Condition Bell pier condition • Long term toe failure on both sides

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

  38. Assignments and Responsibilities • Extrication/ Entry Team • Developing plan for patient extrication • Also personnel used for digging • Assists Shoring Team to set shores • Shoring Team • Assembling, placing and removing shoring & walers • Panel Team • Place ground pads • Prepare and placement of panels

  39. 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

  40. TECHNIQUES FOR TRENCH PROTECTION

  41. 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

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

  43. 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.

  44. The “L” trench can be describe as two trenches that intersect at there ends

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

  46. Pier-hole

  47. Trench Environments

  48. Tacoma incident w/ fatality Trench accidents have a 112% higher fatality rate that other construction accidents

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