EXCAVATIONS

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Regulations OSH Standards Rule 1410 Construction Safety OSH Standards Rule 1413-Excavation 29 CFR 1926 Sub Part P - Excavation

AGENDAIntroductionTerminologiesExcavation HazardsGeneral Requirements Prior to Excavation Soil TestingExcavation Safety PrinciplesMaximum Allowable SlopesMethods of Excavation ProtectionOSH RequirementsContributory Factors in Excavation CollapseExcavation Safety InspectionProtection SystemEquipment & HandtoolsHeavy Equipment Operator & SpotterStrategies in Implementation of Excavation Activities

INTRODUCTIONExcavation is always important part of the construction works & mining, i.e, excavation of building & bridge foundations, trenching for buried pipelines & electrical poles, tunneling, etc. Strategic plan should be tabled & implemented while engage for this work.

Accidents due to cave-in occur for excavations which are not shored or otherwise supported. Even rock that looks solid from a cursory inspection can collapse w/o warning. The sides of an excavation may need to be suitably shored, benched or sloped back to a safe angle of repose, depth and soil classification.

INTRODUCTION (CONT)Other types of excavation accidents are caused by contact w/ above & under ground pipes and cables, by falls of equipment and person, by persons being struck by excavating equipment, and by hazardous atmosphere.

INTRODUCTION (CONT)TYPICAL EXCAVATION SITE

Typical Excavation Sites

Excavation HazardsSurface encumbrancesUtilitiesAccess/EgressVehicle trafficFalling loadsMobile equipment

Hazardous atmospheresWater accumulationAdjacent structuresLoose rock or soilFallsCave-in

GENERAL REQUIREMENTS PRIOR TO EXCAVATIONCarry out joint site safety inspection with client / owner, consultant & company representatives.Identify & locate underground facilities / utilities, i.e., water / oil / gas pipelines, electric powerlines, telephone lines, sanitary sewer lines.Municipal Permit RequirementsExcavation PlanVerify existing utilitiesRefer to as built plansEmergency / Contingency PlanPublic safetyProximity of adjacent structuresWeather & moisture conditionsSources of the vibrationsAdjacent road footpathsMethod of excavationOther possible considerations

Surface EncumbrancesNeed to be removed or supportede.g. fencing, piping, structure, materials

UtilitiesUndergroundLocate prior to diggingCertify deactivationProtect, support, or remove

Access/EgressNote: Poor housekeeping --- # 1 cause of slips, trips and falls on construction projectsDebris kept cleared from work areasMark hazards Barricade or cover holes

Egress provided- - 25 travel distance- ladders- ramps- stairs

Vehicle TrafficTraffic ControlTraffic Safety Vests

Mobile EquipmentWarning systemBarricadesHand signalsMechanical signalsStop logsGrade away from excavation

Hazardous Atmosphere Test @ 4 if suspected LELOxygenCOH2SPetroleumOther toxics

VentilationDisplace hazardous gases and vaporsConsiderationsHeavier than air or lighter than air contaminantExhausting or blowing inVolume/time required to lower concentrations to acceptable levels

Water AccumulationsProtection from hazards associated with water accumulationProtection against cave-inWater removal (pumping)Run-off protectionConsider temporary shut-off of water lines

Adjacent StructuresEnsure structure stabilityShoringBracingUnderpinningOr evaluation by P.E.

Cave-inProtection from cave-in requires a systematic approach including:Soil classificationProtective systemsInspectionEmployee training

SOIL TESTINGSoil testing shall be done by accredited Soil Testing Firm for the following reasons:soil type pre-planning type of sloping / shoring requiredCompilation of Test Certificate

EXCAVATION SAFETY PRINCIPLES

SAFETY PRINCIPLESSOIL MECHANICSIn trenching and excavation practices, SOIL is defined as any materials removed from the ground to form a hole, trench or cavity for the purpose of working below the earths surface.

SAFETY PRINCIPLESSOIL MECHANICSSoil Mechanics point of view:

SAFETY PRINCIPLESFigure 2. Mechanics of Trench Failure.(2a)(2b)TRENCH FAILURES(2c)(2d)(2e)

SAFETY PRINCIPLES

SAFETY PRINCIPLESSOIL CLASSIFICATIONStable Rock - natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed.

Type A - cohesive soil with unconfinedcompressive strength of 144 kPa or greater. Examples; clay, silty clay, clay loam, sandy clay, clay loam and silty clay loam and sandy clay loam.

SAFETY PRINCIPLESSOIL CLASSIFICATIONType B - cohesive soil with unconfined compressive strength greater than 48 kPa but less than 144 kPa.Examples;angular gravel, silt, silt loamsandy loam

Type C - cohesive soil with unconfinedcompressive strength of 48 kPa or less. Examples; gravel, sand, loamy sand submerged soil

SAFETY PRINCIPLESTYPES OF SOIL COLLAPSE General zone of exposure The area where workersare exposed to masssoil/rock movement. Spoil pile slide .

SAFETY PRINCIPLESTYPES OF SOIL COLLAPSE Side wall Shear Slough-in (Cave-in) Rotation

MAXIMUM ALLOWABLE SLOPES

METHODS OF EXCAVATION PROTECTIONSloping - please see table for maximum allowable slopesBenchingShoring / TimberingSheet PilesConcrete PilesMicro pilesDiaphragmDewatering System

OSH REQUIREMENTS

OSH REQUIREMENTSGENERAL REQUIREMENTSTRAIN WORKERS

OSH REQUIREMENTSGENERAL REQUIREMENTSPERSONAL PROTECTIVE EQUIPMENT (PPE)

OSH REQUIREMENTSGENERAL REQUIREMENTSPROTECTION SYSTEMS

The excavation or trench must either be sloped or supported as required to comply with OSHS

Excavation over 6.6 m deep, protection system must be installed to prevent the movement & collapse of adjacent structure shall be designed by structural engineer & approved by the proper authority.

OSH REQUIREMENTSGENERAL REQUIREMENTSLOCATION OF EXCAVATED MATERIALS AND EQUIPMENT

OSH REQUIREMENTSGENERAL REQUIREMENTSPUBLIC PROTECTION & TRAFFIC CONTROL

Traffic around the site must be controlled, and barricaded, signs and/or flag persons used as needed to control both vehicular and pedestrian traffic.

OSH REQUIREMENTSGENERAL REQUIREMENTSPROVISION FOR ACCESS/ EGRESS

A ladder must be located within 25 ft or 8m of a workers working position.d>1 m0.83 m

OSH REQUIREMENTSGENERAL REQUIREMENTSd>2 m1.0 mPROVISION FOR BARRICADES

OSH REQUIREMENTSGENERAL REQUIREMENTSEXPERIENCED SUPERVISOR

An experienced and trained worker is designated to directly supervise each excavation project.- sloping and benching- shoring requirements- emergency rescue procedures.

OSH REQUIREMENTSGENERAL REQUIREMENTSSITE INSPECTION

Every part of an excavation over 2 m deep where workers work shall be inspected.

A competent person shall conduct daily inspections of excavations, adjacent areas, and protective systems for evidence of a situation that could result to an accident.

CONTRIBUTARY FACTORS IN EXCAVATION COLLAPSEWater (i.e., rain, natural ground water, near the water sources)!Improper sloping technique!improper impoundment of excavated soil!Wrong parking of heavy equipment, machines & vehicles!Improper barricade, light, sign, etc.No regular monitoring or inspection!No adequate training!

Simple SlopeType A - 3/4:1

Type B - 1:1

Type C - 1 :1

BenchingType A

Type B (cohesive soil)

Type CNA

Shoring

Timber Shoring

Aluminum Shoring

Shields (Trench Boxes)

Protective SystemsRemovalEmployees clear of area under shields during removalShoring removed from the bottom up, SLOWLY!Backfill with removal

SITE INSPECTIONEXCAVATION SAFETY INSPECTIONInspection shall be conductedpriorduringafter each hazard changing event.

Daily Inspection shall be conducted onexcavationsadjacent areasprotective systems for possible cave-insfailure of protective systemshazardous atmospheresother hazardous conditions

SITE INSPECTIONEXCAVATION SAFETY INSPECTIONSAMPLE DAILY INSPECTION

Surface ConditionsCracks or CrackingSpoil piles set back 2 from edgeNo equipment or material near edgeNo standing water in excavationNo sources of vibration

Banks and Sides of Slope or BenchCracks or CrackingSpallingChange in Soil typeSlope adequate for soil

SITE INSPECTIONEXCAVATION SAFETY INSPECTIONSAMPLE DAILY INSPECTION

Shoring and ShieldingIn placeNo leakage on hydraulic cylindersWedges tight

Access and EgressAccess every 25 feetStairs, ladders and ramp set properly

SITE INSPECTIONEXCAVATION SAFETY INSPECTIONSAMPLE DAILY INSPECTION

Existing UtilitiesSupport AdequateLoose MaterialsUtilities identified and protected.

WeatherRainTyphoon, Storm, Wind

PPEReflectorized vests in vehicular areasHard hats, steel-toe shoes, etc. being used as specified.

PROTECTION SYSTEMEXCAVATION SAFETY INSPECTIONSLOPING AND BENCHINGThe slope and configuration of sloping and benching system shall be selected and constructed by competent person.

SHORING AND SHIELDING

PROTECTION SYSTEM SELECTION OF PROTECTION SYSTEMS Is the excavation more than 3 feet or 1 meterIs the excavation entirely in stable rock Excavation may be made with vertical sidesExcavation must be sloped,shored, or shieldedFigure A. Preliminary Decisions Is there potential for cave-in? Go to Figure C Go to Figure B NOYESNONOYESYESSHORING OR SHIELDINGSELECTEDSLOPINGSELECTED

PROTECTION SYSTEM SELECTION OF PROTECTION SYSTEMSFigure B. Sloping OptionsSloping selected as the method of protectionWill soil classification be made in accordance with the maximum allowable configurations and slopes, or designs using tabulated data , or design by a registered engineer.Excavation must comply with one of the three options:

Option 1Design using requirements of Soil Classification and requirements of sloping and Benching.

Option 2Designs using other tabulated data

Option 3Design by a registered Professional Engineer.Excavation requires a slope of 1 1/2H and 1V (34 deg.)NOYES

PROTECTION SYSTEM SELECTION OF PROTECTION SYSTEMSFigure C. Shoring and Shielding OptionsShoring and Shielding selected as the method of protectionSoil classification is required when shoring or shielding is used. The excavation must comply with one of the following four options.

Option 1Design using requirements of Soil Classification and requirements of Timber Shoring for Trenches.

Option 2Designs using Manufacturers Tabulated Data

Option 3Designs using other tabulated data.

Option 4Design by a registered professional Engineer.

EQUIPMENT & HANDTOOLSEQUIPMENTBackhoebulldozerwheel LoaderGraderRock Breaker

HANDTOOLSShovelPickaxPneumatic hammeretc.

HEAVY EQUIPMENT

BACKHOE

Back Hoe

PNEUMATIC HAMMER

EXCAVATION SAFETY Whatswrongwiththisphoto?

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