2 WHAT IS A TRENCH? O.S.H.A. defines a trench as Excavations that are deeper than they are wide, however no more than 15 feet wide and 20 feet deep.O.S.H.A. only recognizes the need for worker protection in trenches that are in excess of 5 feetThe O.S.H.A. standard for trenches is 29CFR 1926Trenches that exceed 20 feet deep and 15 feet in width require a Registered Professional Engineer (RPE)
3 HIDDEN HAZARDS65% of deaths that occur in trenches are “would be rescuers”A second hazard is the “Secondary Collapse”Initial collapses weaken the trench side wallsBuried utilitiesBad air quality
4 O.S.H.A. Worker Protection O.S.H.A. prohibits entry into trenches over 5 feet deep unless one of the following conditions are met:The walls are properly sloped back so they cannot fall inThe worker is properly protected by a properly designed and positioned trench shieldThe worker is protected by properly designed and constructed shoring
5 3 TYPES OF WORKER PROTECTION SlopingShieldingShoring
6 TYPES OF COLLAPSES4 TypesSlough-inSide wall-inShear-inSpoil-in
7 FACTS ON SOIL The speed of dirt Weight of dirt Trench walls often collapse in less than 1/10 of a secondWeight of dirtA single cubic foot of dirt can weight as much as 145 lbs.A small cave in involves about 1.5 cubic yards of dirt, or about 4,000 lbs.
8 RESCUE OPERATIONS Long term operations Victims must be entirely uncovered prior to attempting a rescueBackhoes and other hydraulic equipment MUST never be used
9 SOIL CLASSIFICATIONS Class A Soil Class B Soil Class C Soil Most stableSoil has clumps and clumps are difficult to break apartThumb test can only dent the clumpClass B SoilSoil has clumpsClumps break apart with minimal effortThumb can penetrate or mold soilClass C SoilSoil is granularTrench is wet
10 METHODS FOR CLASSIFYING SOILS Thumb penetration methodSimplest and easiestSoil that is removed the spoil pile, if the soil is granular of wet = Class C SoilSoil that is removed from the spoil pile is, difficult to break apart or only dents = Class AAnything in between = Class B
11 ADJUSTMENTS TO SOIL CLASSIFICATIONS Once the basic soil classification has been determined, other environmental factors must be consideredIn many cases the soil must be lowered, if the soil is being effected by dangerous environmental conditionsThe longer a trench remains open and exposed to the elements, the more effected it will be.
12 SOIL ADJUSTMENTS Layered Soils Fissured Soils Previously Disturbed SoilVibrationWet soils or standing water in the trenchAny wet soil is automatically considered Class C Soil
13 O.S.H.A. ADJUSTEMNTS TO SOIL CLASSIFICATION Wet Soil = Class CAdjust Soil Class DOWN one level for the following:Trench involves SLOPED-LAYERED SOILTrench involves FISSURED (Cracked) SOILTrench involves PREVIOUSLY DISTRUBED SOILTrench is subject to VIBRATION
14 OTHER FACTORS THAT EFFECT TRENCH STABILITY Water RemovalUnderground UtilitiesO.S.H.A. requires that all utilities or other structures exposed in trenches be properly supportedSurface EncumbrancesItems that cannot be moved and have to be supportedSuperimposed LoadsO.S.H.A. requires that all superimposed loads, including the spoil pile, be placed no more than two feet from the edge of the trenchExposure to the elementsO.S.H.A. requires that trenches be analyzed for safety and stability at least daily, and after any event which may have effected the stability of the trench or of the protection system
15 ADDITIONAL REGULATIONS FOR WORKER SAFETY Personal Protective EquipmentHard HatsShoes or BootsIn areas of traffic workers should wear reflective vestsIn trenches with water accumulation, drowning precautions must be taken
16 PROTECTIVE SYSTEMSO.S.H.A. provide three methods for protecting workers in trenchesSlopingShieldingShoringNo worker is to enter a trench greater than 5 feet deep unless one of these protections is in place
17 ADDITIONAL REGULATIONS FOR WORKER SAFETY Escape RoutesNo more than 25 Feet travel distancesLadders are usually usedLadders must extend a “few feet” above the lip of the trench and MUST be securedAir Quality MonitoringCare should be taken with the sick or unconscious patientVentilation may be required“Bad Air”Oxygen deficientCarbon MonoxideHydrogen Sulfide
18 SLOPINGInvolves the cutting back of the side of the trench to an angle at which the earth will no longer slide.ANGLE OF REPOSE – is defined as the angle at which soil will no longer slideClass A = 1 ft. down ½ ft. backClass B = 1 ft. down 1ft. backClass C = 1 ft. down 1 ½ ft. backSafest form of protection, however is time consuming and takes a significant amount of space
19 SHIELDING / TRENCH BOXES Extremely strong steel boxesAssembled on site and moved into placeTrench boxes should be placed so to extend above the lip of the trench and not more than 2 feet off the bottom of the trench
20 SHORINGShoring is designed to be strong enough to stop the walls from starting to move, but is not designed to be strong enough to stop moving dirt.Several types of shoringAir shoresHydraulic ShoresDimensional Lumber Shoring
21 SHORING Continued Screwjack Shoring Uses up rights and whales Timber ShoringShoring membersUprights4”x6”x 14’Cross braces8”x8”x 4’Whalers8’x8’x14’Sheeting1 1/8” plywood¾” 14 ply thin formsScrewjack ShoringUses up rights and whalesNot O.S.H.A. approved
22 SHORING Continued Pneumatic Shoring Use of air pressure Locking collar and pin assemblyWorking range is limitedCost extensive due to the need to purchase different sizesHydraulic ShoringAssembled with cross braces and uprights in placePumped with a hydraulic pumpVery heavyNot easy to storeShores can be placed without entering the trench
23 SHORING INSTALLATIONOf the four shoring systems, only the hydraulic shoring can be installed without entering the trenchShoring systems must be installed from the top of the trench down, and removed in the reverse order.
24 INITIAL COMPANY OPERATIONS Initial response personnel can still perform tasks which will serve to speed-up the rescue, protect the victim, and eliminate the need for rescue or recovery of additional personnelEstablish a Trench Rescue Training ProgramPreplan and Activate a Trench Rescue Team Quicklly
25 OPERATIONS TO BE CONDUCTED ON ARRIVAL DO NOT allow personnel into an unprotected trenchDO NOT allow the use of heavy equipmentSet up control zonesHot, warm, coldStop all sources of vibrationStop all vibrations within 300 ft. of the trenchTry to locate the victimStart moving superimposed loadsLay ground pads if availableTest the air and Set-Up ventilation
26 OPERATION CONTINUEDPrepare for injuriesNotify O.S.H.A.