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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