PSFA Trench RescuePSFA Trench Rescue

Relevant Reference MaterialRelevant Reference Material

OSHA 29 CFR1926.650: Scope, Application and Definitions

OSHA 29 CFR1926.651: Specific Excavation Requirements

OSHA 29 CFR1926.652: Requirements for Protective Systems

OSHA 29 CFR 1926 Subpart B Appendices A-F

National Fire and Rescue; Trench Rescue Secrets, Parts 1 & 2. Patrick Moore

FEMA Structural Collapse Technician Course, Student Manual, Module 2B Shoring Construction, http://www.fema.gov/emergency/usr/sctc.shtm

IntroductionIntroduction

Each year, 1,100 workers are severely injured and 100 workers die in trenching and excavating accidents

Why do trench accidents Why do trench accidents occur??occur??

ComplacencyShortcutting of safety for profitWeekend warriors-no shoring utilizedIgnorance of hazardsUnprepared or poorly trained in excavation

Anatomy of a TrenchAnatomy of a Trench

Trench-Trenches are narrow excavations made below the surface of the ground. In general, the depth is greater than the width. However, the width of a trench is not greater than 15 feet. An excavation is also considered to be a trench

In reality, an open grave waiting for an occupant

Inherent trench problemsInherent trench problems

Natural and man made forces began acting immediately to close a trench once its been created

These forces overcome the strength of the soil composition and cause the trench to eventually collapse

Dirt DynamicsDirt Dynamics

1 cubic foot of dirt weighs 100 lbs1 cubic yard of dirt weighs 2,700-3,500 lbs1 cubic foot of dirt will fill eight 1 gallon

buckets1 cubic yard of dirt will fill 203 1 gallon

buckets

1

11 3

3

33

Soil TypesSoil Types

Type A-Most stable:clay, silty clay and hardpan (resists penetration) No soil is type A if it is fissured, is subject to vibration of any type, has previously been disturbed or has seeping water

Type B-Medium stability:silt, sandy loam, medium clay and unstable dry rock, previously disturbed soils unless otherwise classified as Type C. Soils that meet the requirements of Type A soil but are fissured or subject to vibration

Soil Types continued:Soil Types continued:

Type C-Least stable:gravel, loamy sand, soft clay, submerged soil or dense, heavy unstable rock and soil from which water is seeping freely

Soil Effects on VictimSoil Effects on Victim

Traumatic Asphyxiation– Soil restricts expansion of victims chest – Soil blocks airways– Causes suffocation

Impact crushes the victim:– Breaking limbs– Causing internal injuries– Causing soft tissue injuries

Victim Survival ProfileVictim Survival Profile

Time is the biggest factor8-10 min.’s for response6-10 min.’s for initial assessment18” of dirt = 2500-3500 poundsHazard Risk Assessment Profile needs to be

considered

Types of Trench AccidentsTypes of Trench Accidents

Spoil pile slide

Occurs when improper techniques are used and the excavated material is not placed far enough away from the trench lip UNSAFE

Slough In (cave in)Slough In (cave in)

Most commonly occurs to previously excavated materials, primarily in sand, gravel mixtures

Slough trench lip

Side wall shearSide wall shear

Occurs commonly to clay type soils exposed to drying

Side wall shear

Trench TerminologyTrench TerminologyLip extends 2 feet vertically and horizontally from the edge of the trench. If the spoil pile is located within 2 feet of the trench, it must be removed.

Lip

Padding the LipPadding the LipAcceptable materials: 2 x 12 lumber, 4 x 8 ¾” or 5/8” plywood or trench panels. Should extend from an area of stability to instability, if end of trench is accessible, start there.

Padding the LipPadding the Lip

Trench TermsTrench TermsAngle of Repose

The greatest angle above the horizontal plain at which loose soil will lie without sliding. Reducing this angle will reduce the amount of spoil slide

Trench TermsTrench TermsUprights-Vertical supports that attach panel to upright. Shoring is attached to uprights between panels (usually 2 x 8’s or 12’s)

Panels-Support side walls of trench Pre-made Shore form panels, 4 x 8 sheeting of 2 ¾” plywood

Shoring-Horizontal bracing between panels, can be pneumatic or timber shoring

TermsTermsScabs-Hold timber shoring firmly in place against uprights. 2 x 4 pieces

Spoil pile-The material excavated from the trench

TrenchTrenchTermsTerms

Lowering lines-Line used to lower pneumatic shoring. Lines should be of a different color

Making the Trench SafeMaking the Trench Safe

Three ways to “safe” a trench:– 1.-Slope the angle of repose– 2.-Benching– 3.-Shoring/Shielding

Sloping the angle of repose and benching require backhoes as well as additional manpower.

Shoring operations require well trained coordinated rescuers

Shoring BasicsShoring Basics

Shoring Types:Shoring is the provision of a support system for trench faces used to prevent movement of soil, underground utilities, roadways and foundations.

Shoring TypesShoring Types

Hydraulic Shoring:

A prefabricated strut and/or system manufactured of aluminum or steel. Pressurized w/5 gal hand pump to 500-1000 psi. Pressure must be maintained, no locking device.

Shoring TypesShoring TypesPneumatic Shoring System:

Works in a manner similar to hydraulic shoring, primary difference is that pneumatic shoring uses air pressure to set shores (can be set manually)

Pneumatic Strut

Strut Extension Swivel strut base

ShoringShoring Types Types

Timbering: Difficult and time consuming task. 4 x 4 lumber generally used for timbering.

ShieldingShielding

IV.                                                                                                                                   IV.                                                                                                                                   

Trench boxes are different from shoring because instead of shoring up the trench face, they are intended to primarily protect workers from slough ins.

Shoring OperationsShoring Operations

Shores should be located 18”-24” from the floor and the lip of the trench

Shores should be no more than 48” apart vertically

Placement of the first shore should be from the outside of the trench using hydraulic/pneumatic shoring (shores should not be placed directly above the pt/victim)

Pneumatic Shoring OrderPneumatic Shoring Order

First shore should be placed in the middle of the upright

Second shore is placed in the top of the upright

Third shore is paced in the bottom of the upright– shores are lowered by lowering lines directed

by the shoring officer then “shot”

Shooting ShoresShooting Shores

After shore is lowered and is in place (level), the following commands are to be given by shoring officer:– “Prepare to Shoot”– “Shoot”– Pneumatic shores are shot at 100 psi and

released at 150 psi

Corner ShoringCorner Shoring

Corner ShoringCorner Shoring

Corner ShoringCorner Shoring

Nailing ShoresNailing Shores

Nail half way into 45 swivel base and then bend nail over corner of base

Off Setting ShoresOff Setting Shores

TimberingTimbering

The first shore is placed at the top of the upright and requires the rescuer to enter the trench on a ladder

The second shore or middle shore is placed in the middle of the upright, again forcing rescuer further in the trench on a ladder

Last shore is placed on the bottom of the trench above trench floor

Hazard ControlHazard Control

Hazards may include:– Electrical utilities– Ruptured gas lines– Broken water/sewer

lines– Workers on scene– Spoil pile– Falling debris in trench– O2 deficient

atmosphere

Vibration from:– Operating machinery

on scene– Nearby traffic– Responding apparatus

Rescue OperationsRescue Operations

DO NOT GO INTO THE HOLE!!!!

First and foremost, the company officer needs to limit the possibility of further injuries and death, get the hole under control, make it safe for everyone, and, with the proper equipment, start to develop a safe work space.

Safety FirstSafety First

Appropriate PPE:– Dress for success, right gear should include

head, hand, foot, eye, ear and respiratory protection as appropriate.

Make the general area safe:– Establish a hot, warm and cold zone

Safe the General AreaSafe the General Area

First arriving apparatus:– Stops and is turned off no less than 250’ from

the dispatched location. This becomes the warm zone

– Establish command and designate a staging area for other other responders with equipment/apparatus.

– Assign a staging officer

Cold/Hot ZoneCold/Hot Zone

Cold Zone Staging should exceed 500’or more from trench incident site

Hot Zone Area:– Should extend 100’ in all directions around the

site– Use fire line tape, rope, etc. to mark these zones

Trench

100 Feet

250 Feet

ICPersonnel

Staging

500 Feet

Staging

Rehab

PIO

Operations

Outer Circle CheckOuter Circle Check

Restrict entry to siteEliminate sources of vibration, stop and

shut down construction equipmentIdentify witnesses to the accident if anyIdentify job foremanBegin to establish incident perimeters

Inner Circle CheckInner Circle Check

Approach site from end of trenchIdentify victim location (if possible) using

witnesses, location of trench failure, surveyors markers etc.

Identify number of patientsEstablish patient/victim condition if

possible

Making the Rescue Scene Making the Rescue Scene SafeSafe

Means monitoring the environment around the incident site. There is a good chance a hazardous environment exists and perhaps oxygen deficient space. Remember established confined space limits and use them to define problems. (Limited air?? Limited access?? Is the space continuously monitored?)

Inner Circle CheckInner Circle Check

How is the patient trapped?

-totally buried, if so, where??

-trapped by utilities

Where???– Don’t forget to consider Hazard Risk

Assessment Profile– Direct non trapped workers out of trench

Establish full command structure

Operations: 4 Team ApproachOperations: 4 Team Approach

1.-Excavation2.-Monitoring3.-Shoring4.-Rescue

ExcavationExcavation

Coordinates operation for dewatering (if needed

Initiates/completes lip safetyRemoves spoil pile, reduce angle of repose

MonitoringMonitoring

Monitors trench during entire rescue operation

Establishes ventilation in all levels of trenchEstablishes back-up ventilation in case of

primary ventilation failure

ShoringShoring

Shores trench with pneumatic, hydraulic, timber shoring

Establishes cutting table if neededEstablishes air supply for pneumatics with

back up supplyUnder control of a shoring officer

Cutting Table at the cut station

RescueRescue

Prepares and executes disentanglement procedures

Patient/victim packagingPatient/victim removalRope system if needed (4:1, 5:1)A-Frame/gin pole if needed

RescueRescue

Disentanglement procedures:-Remove dirt/soil away from victim,

accomplished by hand digging and buckets

-Clear the head and chest if victim caught in collapse in this position

-Secure patient using acceptable devices

(LBB, LSP, Reeves, Stokes, Harnesses)

RescueRescue

Be prepared for vertical extrication:– Consider A-Frame (engine co. task)

construction away from hot zone and radio for it when ready

– Mechanical advantage system needed– Shoring position may be impede vertical

pt/victim removal

A-Frame UseA-Frame Use

A-FrameA-Frame

SummarySummary

Managing the incident is the key to maintaining control, because you run a very good chance of working eight hours or more in many cases. Incident complexity and risk demand strong command, control and decision making ability.

Hazards in a trench rescue can be deadly and strike without little or no warning.

DON’T GET DEAD