TRI-SERVICE NFPA 1670

Trench Rescue AwarenessReminderYour are not usually

attending this time for a patient, it is about body

recovery so don’t add another body!

WHY WERE YOU CALL TO THE SCENE simple Digging their own grave…

60 to 65% OF ALL FATALITIES ARE THE WOULD-BE RESCUER

Lack of knowledge

Lack of training

Compassion for the victim

Trench Rescue Hazards

• Hazards are not obvious

• Secondary collapses are common

• Dirt is heavy and moves fast

• Rescues are usually long-term operations

• Backhoes are not safe for victim rescue

• OH&S has trench limits and regulations

• Buried utilities can pose a threat to rescuers

• Impact or entrapment from falling debris or equipment

• Unprotected trenches are dangerous

• There may be inadequate equipment for shoring

• Possible legal liabilities for fire officers

Terms to Know

• Angle of Repose – the greatest angle above the horizontal plane at which loose dirt will lie without sliding.

• Back Fill – the refilling of a trench, or the material used to refill a trench, or to fill a void between two surfaces.

• Spoil Pile – the material excavated from the trench.

More Terms to Know

• Fin Form – ¾”, 14-ply, arctic white birch.

• Strong Back – a 2 x 10 or 2 x 12 attached to fin form to create a panel for shoring the wall of a trench.

• Struts – the horizontal bracing between the trench walls.

• Uprights – vertical supports, usually 2 x 8’s, the depth of the trench.

• Ground Pads – 4x8 or 2x8 sheets of plywood used to disperse weight around the edge of the trench.

Fin-form & strong

backs

Air-Shore strut

Paratechstrut

Back fill (wood &

dirt)

Ground pads

Use of multiple

types of shores

Fin-form & strong

backs

Ground pads

Whalers

Escape ladders

Trenches are Dangerous

• Once earth is disturbed, pressure begins to act on the trench walls.

• Sooner or later all trenches cave in.

• There is no way to predict when a trench will fail.

Note the deterioration to the left corner

Vibration Hazards

• All heavy equipment should be turned off and secured (take the keys and block the tires).

• All sources of vibration should be eliminated for 300’ in every direction. This includes roadways and railways.

Backhoes

• Backhoe operators will insist they can dig the victim out.

• OH&S statistics are riddled with cases of disembowelment and decapitation.

• Backhoe operators cannot tell the difference between a rock and a body.

• Weight of the backhoe adds to instability of trench walls.

• Vibration likely to speed up secondary collapse

Atmospheric Hazards

• The victim may be the result of bad air in the trench and have no actual trauma.

• Air should be monitored every 15 minutes for O2, CO, H2S and combustibles.

• Rescuers can fall victim to the same bad air if it is not checked regularly.

• O2 permissible exposure limits: 19.5%-23.5%.

• Methane Gas Flammable Limits: 5.0%-15.0%.

Public Utilities as a Hazard

• Many trenches are dug for utility maintenance or installation.

• Utility cables and pipes can add to trench instability.

• Electrical utilities can pose a threat to both the victim and the rescuer.

• Broken sewer or water lines may fill the trench, causing a drowning potential for the victim.

Dirt as a Hazard

• One cubic foot of dirt weighs 90-145 lbs.

• The average collapse is 1.5 cubic yards (4000 lbs.).

• The average victim buried under 2 feet of dirt will be covered by 3000 lbs., about 1000 lbs. of that will be on his chest.

• The speed of collapsing dirt is often less than 1/10th of a second.

Time…Time…Time…

• The average trench rescue takes between 4 and 10 hours.

• Long rescue time allows for further deterioration of trench walls.

• Rotation of rescue crews necessary to keep people fresh.

The First-In Company

• The location of an unconscious or trapped victim can be marked with paint or dry-chem at the edge of the trench.

• Ground pads will need to be laid around the edge of the trench.

• The spoil pile must be moved a minimum of 2’ away from the edge of the trench. This must be done while working off ground pads.

Incident Command

• Establish a trench team command structure

• Rescue Officer (required) – Officer in charge of the rescue and designates other rescue sectors.

• Rescue Safety (required ) – May be in addition to the scene safety officer and trained to the level of

the incident.

• Rescue Operations – Officer who runs the rescue.

Water, Water Everywhere…

• Prior to the rescue team entering the trench, all water must be evacuated. This includes water from a main break, ground water and rain water.

• Small amounts of water can be removed with a sump pump in a 5 gallon bucket.

• Larger amounts of water or water which is flowing can be removed with a vac-truck.

• The truck must be set up 300’ away and have a safety valve in line with the vacuum hose.

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Trench Requirements

• > 4 ft you must ladder

• > 5 ft you must shore

• Ladder within 25’ reach

• Ladder must be extend 3’ above lip of trench

25Layers of soil

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Belly

Li

p

Toe

Floor

Spoil pile

Parts of a Trench

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Types of Collapses

• Slough-in (Belly In)

• Sidewall-in (Side Wall Shear)

• Shear-in (Lip Slide)

• Spoil-in (Spoil Pile Slide In)

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Slough-In (Belly In)

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Notice the color of

the soil

Slough-

in

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Sidewall-In (Side Wall Shear)

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Shear-In (Lip Slide)

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Spoil-In (Spoil Pile Slide In)

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Stop Vibrations within 300’ of

Trench

30

0’

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Superimposed Loads

• Add weight & stress to trench

• Examples

Spoil pile

Heavy equipment

Work materials (cable, vaults, pipe)

People

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Superimposed Load

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Wet Soils/Submerged Soils

• Added weight

• Loss of friction

• Movement of water carrying soil

• Standing water undermining trench walls

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Exposure to Elements

• Time - longer trench is open the more unstable it will be

• Sun and wind

• Freezing / Thawing

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Buried Utilities

• Must be located do not assume they were done and correct

• Often requires time-consuming hand digging

• Common problem since most trenches are located in easements

• OH&S requires that all utilities or other structures exposed in trenches be properly supported.

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Types of Worker Protective Systems

• Sloping

• Benching

• Shielding

• Shoring

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Determined by

• Soil class

• Work space required

• Economic factors

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Sloping

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Benching

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Shielding Principles

• Strong metal “boxes” designed to withhold the pressure of collapsing soil

• Must be engineered for size trench & soil class

• Must be level with or extend above lip of trench.

• Must not be more than 2’ up off the bottom

• Usually dragged down a trench -worker may be inside as long as no lifting is required

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Two basic types of shields

• Steel, non-adjustable

• Aluminum, adjustable

Manual

Hydraulic

Pneumatic

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Manufactured Trench Boxes

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Specific Types of Shores

• Timber

• Screw jack

• Pneumatic

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Timber Shoring

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Screwjack Shoring

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Pneumatic Shoring

• Air driven units

• Locking collar & pin

• Limited working range

• Relies on industry/regulations timber charts for uprights & whalers

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Size –Up Considerations

• Depth of Trench

• Soil Type

• Entry point

• Weather conditions

• Width of Trench

• Spoil pile

• Exit point

• Level of Training

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Size –Up Considerations(con’t)

• Water content in Trench

• Impact of nearby LOADS

• Location of Victim(s)

• Angle of Repose

• Supports in place

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Size –Up Considerations(con’t)

• Manpower

• Equipment availability

• Witness Information

• EMS (life support)

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Personal Protective Equipment

At minimum:

• Head Protection (Const. Hardhat)

• Eye Protection (Safety glasses)

• Hand Protection (Leather work gloves)

• Foot Protection (Steel toe/shank boots)

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Prepare for injuries

• Fractures

• Lung injuries

• Head injuries

• Spinal injuries

• Respiratory system injuries

• Hypothermia

• Crush syndrome

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10 Steps to Trench Rescue

• Preparation

• Response

• Assessment

• Hazard Control

• Support Operations

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10 Steps to Trench Rescue

• Gaining Access

• Disentanglement

• Packaging

• Removal

• Termination

NFPA 1670 Trench Rescue Awareness

Refresher Exam

1. O H & S defines a trench as excavations that are deeper than they are wide.A. TrueB. False

2. O H & S only recognizes the need for worker protection in trenches that are in excess of:A. 1 footB. 2 feetC. 3.5 feetD. 5 feet

3. List three trench hidden hazards.

4. Before entry into a trench, O H & S requires:A. Walls are properly slopedB. Trench shieldsC. Properly designed shoringD. All of the above

5. A Side wall-in collapse is when the excavated soil is too close to the trench resulting in collapse.A. TrueB. False

6. A cubic yard of soil weighs approximately:A. 100 poundsB. 500 poundsC. 1.5 tonsD. 1 ton

NO ROOM FOR WRONG ANSWERS

7. Of the 3 soil classifications, which is the most unstable?A. Class AB. Class BC. Class CD. Class U

8. Soil that is removed from the spoil pile and is difficult to break apart is?A. Class UB. Class BC. Class AD. Class C

9. Initial thumb penetration has determined the soil to be Class B (moist) however it has been raining since first responders arrived. Based on this environmental condition, the classification is now:A. Class AB. Class B, no change necessaryC. Class CD. Class U

10. Along with sloping, shielding and shoring, what are 2 additional regulations for worker safety?

11. Sloping involves the cutting back of the side of the trench to an angle at which the earth will no longer slide.A. TrueB. False

ONLY A 100% will do for the answer this time

12. A shielding/Trench box may not be more than:A. 5 feet off the trench bottomB. 4 feet off the trench bottomC. 2 feet off the trench bottomD. Shielding/Trench boxes are not required13. There are 4 types of shoring used in trenches:A. Timber, screw jack, pneumatic, whalesB. Screw jack, upright, hydraulic, tensionC. Screw jack, tension, whales, strong backD. Timber, Screw jack, pneumatic, hydraulic

14. Shoring systems must be installed from the bottom of the trench then up.A. TrueB. False

15. List 5 operations to be conducted upon arrival at a trench incident.

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Trench & Excavation Summary

• Recognize the general hazards associated with trench and excavation emergency incidents

• Recognize typical trench and excavation collapse patterns, the reasons trenches and excavations collapse, and the potential for secondary collapse

• Identify how a rapid, non-entry extrication of non-injured or minimally injured victims is initiated.

• Recognize the unique hazards associated with the weight of soil and its associated entrapping characteristics