2 Relevant Reference Material OSHA 29 CFR : Scope, Application and DefinitionsOSHA 29 CFR : Specific Excavation RequirementsOSHA 29 CFR : Requirements for Protective SystemsOSHA 29 CFR 1926 Subpart B Appendices A-FNational Fire and Rescue; Trench Rescue Secrets, Parts 1 & 2. Patrick MooreFEMA Structural Collapse Technician Course, Student Manual, Module 2B Shoring Construction,
3 IntroductionEach year, 1,100 workers are severely injured and 100 workers die in trenching and excavating accidents
4 Why do trench accidents occur?? ComplacencyShortcutting of safety for profitWeekend warriors-no shoring utilizedIgnorance of hazardsUnprepared or poorly trained in excavation
5 Anatomy of a TrenchTrench-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 trenchIn reality, an open grave waiting for an occupant
6 Inherent trench problems Natural and man made forces began acting immediately to close a trench once its been createdThese forces overcome the strength of the soil composition and cause the trench to eventually collapse
7 Dirt Dynamics 1 cubic foot of dirt weighs 100 lbs 1 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 gallon buckets3113313
8 Soil TypesType 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 waterType 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
9 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
10 Soil Effects on Victim Traumatic Asphyxiation Soil restricts expansion of victims chestSoil blocks airwaysCauses suffocationImpact crushes the victim:Breaking limbsCausing internal injuriesCausing soft tissue injuries
11 Victim Survival Profile Time is the biggest factor8-10 min.’s for response6-10 min.’s for initial assessment18” of dirt = poundsHazard Risk Assessment Profile needs to be considered
12 Types of Trench Accidents Spoil pile slideOccurs when improper techniques are used and the excavated material is not placed far enough away from the trench lipUNSAFE
13 Slough In (cave in) Slough trench lip Most commonly occurs to previously excavated materials, primarily in sand, gravel mixtures
14 Side wall shear Occurs commonly to clay type soils exposed to drying
15 Trench 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
16 Padding 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.
18 Trench Terms Angle 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
19 Trench 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” plywoodShoring-Horizontal bracing between panels, can be pneumatic or timber shoring
20 TermsScabs-Hold timber shoring firmly in place against uprights. 2 x 4 piecesSpoil pile-The material excavated from the trench
21 Trench TermsLowering lines-Line used to lower pneumatic shoring. Lines should be of a different color
22 Making the Trench Safe Three ways to “safe” a trench: 1.-Slope the angle of repose2.-Benching3.-Shoring/ShieldingSloping the angle of repose and benching require backhoes as well as additional manpower.Shoring operations require well trained coordinated rescuers
23 Shoring BasicsShoring Types:Shoring is the provision of a support system for trench faces used to prevent movement of soil, underground utilities, roadways and foundations.
24 Shoring Types Hydraulic Shoring: A prefabricated strut and/or system manufactured of aluminum or steel. Pressurized w/5 gal hand pump to psi. Pressure must be maintained, no locking device.
25 Shoring Types Pneumatic 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 StrutSwivel strut baseStrut Extension
26 Shoring TypesTimbering: Difficult and time consuming task. 4 x 4 lumber generally used for timbering.
27 ShieldingTrench boxes are different from shoring because instead of shoring up the trench face, they are intended to primarily protect workers from slough ins.
28 Shoring OperationsShores should be located 18”-24” from the floor and the lip of the trenchShores should be no more than 48” apart verticallyPlacement 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)
29 Pneumatic Shoring Order First shore should be placed in the middle of the uprightSecond shore is placed in the top of the uprightThird shore is paced in the bottom of the uprightshores are lowered by lowering lines directed by the shoring officer then “shot”
30 Shooting ShoresAfter 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
36 TimberingThe first shore is placed at the top of the upright and requires the rescuer to enter the trench on a ladderThe second shore or middle shore is placed in the middle of the upright, again forcing rescuer further in the trench on a ladderLast shore is placed on the bottom of the trench above trench floor
37 Hazard Control Hazards may include: Vibration from: Electrical utilitiesRuptured gas linesBroken water/sewer linesWorkers on sceneSpoil pileFalling debris in trenchO2 deficient atmosphereVibration from:Operating machinery on sceneNearby trafficResponding apparatus
38 Rescue 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.
39 Safety First Appropriate PPE: Make the general area safe: 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
40 Safe the General Area First arriving apparatus: Stops and is turned off no less than 250’ from the dispatched location. This becomes the warm zoneEstablish command and designate a staging area for other other responders with equipment/apparatus.Assign a staging officer
41 Cold/Hot ZoneCold Zone Staging should exceed 500’or more from trench incident siteHot Zone Area:Should extend 100’ in all directions around the siteUse fire line tape, rope, etc. to mark these zones
42 Rehab PIO IC Operations Trench Staging 100 Feet 250 Feet 500 Feet PersonnelStagingIC250 Feet500 Feet
43 Outer Circle Check Restrict entry to site Eliminate sources of vibration, stop and shut down construction equipmentIdentify witnesses to the accident if anyIdentify job foremanBegin to establish incident perimeters
44 Inner Circle Check Approach site from end of trench Identify victim location (if possible) using witnesses, location of trench failure, surveyors markers etc.Identify number of patientsEstablish patient/victim condition if possible
45 Making the Rescue Scene Safe 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?)
46 Inner Circle Check Establish full command structure How is the patient trapped?-totally buried, if so, where??-trapped by utilitiesWhere???Don’t forget to consider Hazard Risk Assessment ProfileDirect non trapped workers out of trenchEstablish full command structure
47 Operations: 4 Team Approach 1.-Excavation2.-Monitoring3.-Shoring4.-Rescue
48 Excavation Coordinates operation for dewatering (if needed Initiates/completes lip safetyRemoves spoil pile, reduce angle of repose
49 Monitoring Monitors trench during entire rescue operation Establishes ventilation in all levels of trenchEstablishes back-up ventilation in case of primary ventilation failure
50 Shoring 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
52 Rescue Prepares and executes disentanglement procedures Patient/victim packagingPatient/victim removalRope system if needed (4:1, 5:1)A-Frame/gin pole if needed
53 Rescue 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)
54 Rescue Be prepared for vertical extrication: Consider A-Frame (engine co. task) construction away from hot zone and radio for it when readyMechanical advantage system neededShoring position may be impede vertical pt/victim removal
57 SummaryManaging 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.