TRENCH OPERATIONSTRENCH OPERATIONSFor safety is not a gadget but a For safety is not a gadget but a state of mind.  ~Eleanor Everetstate of mind.  ~Eleanor Everet

Objectives Objectives Governing StandardsGoverning Standards Anatomy of a TrenchAnatomy of a Trench Soil PhysicsSoil Physics First arriving units First arriving units

actions/ Scene actions/ Scene management management

Equipment Equipment FamiliarizationFamiliarization

Type of Trench CollapsesType of Trench Collapses Assignments & Assignments &

ResponsibilitiesResponsibilities Techniques for Techniques for

ProtectionProtection

OSHA CFR 1926 Subpart P, OSHA CFR 1926 Subpart P, Excavation:Excavation:

– Important to rescuers for several Important to rescuers for several reasonsreasons First the data and information will give you First the data and information will give you

the information from which you can decide the information from which you can decide the protective systems.the protective systems.

Secondly, knowledge of the standard, its Secondly, knowledge of the standard, its requirements, protective systems, and soil requirements, protective systems, and soil classifications will qualify the user as a classifications will qualify the user as a “Competent Person”.“Competent Person”.

General requirementsGeneral requirements

All trenches must be protected before entries All trenches must be protected before entries except:except:

Those made entirely of stable rock.Those made entirely of stable rock. Those less than five feet in depth, including the height of the spoil Those less than five feet in depth, including the height of the spoil

pile must be protected.pile must be protected. Protection:Protection:

– Anything more than five feet in depth, including the height of the spoil Anything more than five feet in depth, including the height of the spoil pile must be protected.pile must be protected.

Spoil Pile:Spoil Pile:– Must have two-foot set back for the lip.Must have two-foot set back for the lip.

Egress:Egress:– Trenches four feet or greater in depth must have a means of egress Trenches four feet or greater in depth must have a means of egress

every twenty-five feet “Ladders”.every twenty-five feet “Ladders”. Atmospheric:Atmospheric:

– Trenches four feet or greater in depth must be testedTrenches four feet or greater in depth must be tested before entry. before entry.

Definitions Definitions A A “trench”“trench”, means a narrow excavation (in relation to its length) , means a narrow excavation (in relation to its length)

made below the surface of the ground. In general, the depth is made below the surface of the ground. In general, the depth is greater than the width, but the width measured at the bottom is greater than the width, but the width measured at the bottom is

not greater than 15 feetnot greater than 15 feet.. WIDTHWIDTH

DEPTHDEPTH

””Excavation”Excavation”, includes a , includes a trenchtrench

It means any man made cut, cavity, trench, or depression in an It means any man made cut, cavity, trench, or depression in an earth surface formed by the earths removal. Again, in practical earth surface formed by the earths removal. Again, in practical terms, when a hole is more than 15 feet wide at its base, it is terms, when a hole is more than 15 feet wide at its base, it is called specifically an excavation. Overall, an excavation is wider called specifically an excavation. Overall, an excavation is wider than it is deep.than it is deep.

Competent PersonCompetent Person

One who can identify existing or One who can identify existing or predictable hazards in the surrounding predictable hazards in the surrounding that are unsanitary, hazardous, or that are unsanitary, hazardous, or dangerous to employees. Also has dangerous to employees. Also has authorization by the nature of their authorization by the nature of their position to prompt corrective position to prompt corrective measures to eliminate them. The measures to eliminate them. The person shall be knowledgeable in the person shall be knowledgeable in the requirement of this part.requirement of this part.

Anatomy Anatomy

How Heavy is Dirt?How Heavy is Dirt?

Physical forces Physical forces associated with associated with collapse:collapse:– Dirt has volume Dirt has volume

that has mass and that has mass and weightweight

– One cubic foot of One cubic foot of dirt weights dirt weights between 85 and between 85 and 125 pounds per 125 pounds per cubic foot.cubic foot.

Weight of a Volkswagen

2,785 Pounds

Weight of one cubic yard of soil

2,700 Pounds

Soil Physics Soil Physics

Compounding the Compounding the effects of gravity is effects of gravity is hydrostatic hydrostatic pressurepressure

Add the weight of Add the weight of water and rock, a water and rock, a cubic foot of dirt cubic foot of dirt can be as much as can be as much as 125 pounds per 125 pounds per cu/ftcu/ft

A six foot trench:A six foot trench:– at the four foot level at the four foot level

has approximately 400 has approximately 400 pounds vertical weight.pounds vertical weight.

– Lateral forces could be Lateral forces could be expected to be 132 expected to be 132 pounds of horizontal pounds of horizontal pressurepressure

– Distribution of lateral Distribution of lateral pressure occurs on pressure occurs on about a 45 degree about a 45 degree angle from the bottomangle from the bottom

Accidents without cave-insAccidents without cave-ins

– Most emergencies in Most emergencies in trenches deal with trenches deal with something other than a something other than a collapsecollapse

– Most of the work is Most of the work is done after the trench done after the trench has been dughas been dug

– In these cases don’t be In these cases don’t be lulled to sleep by a lulled to sleep by a protected trenchprotected trench

– Approach identically as Approach identically as an open trenchan open trench

Hazards Present?Hazards Present?

First Arrival First Arrival Apparatus spottingApparatus spotting

– Spot at least 100 ft from locationSpot at least 100 ft from location Create Exclusion Zones (on next slide) Create Exclusion Zones (on next slide) Size-up – accurate address of location, call for helpSize-up – accurate address of location, call for help Secure RP, job foreman, or witness to accidentSecure RP, job foreman, or witness to accident Safety 360 Review – approach trench from the end, Safety 360 Review – approach trench from the end,

Secondary size-upSecondary size-up Rescue or Recovery modeRescue or Recovery mode Assess potential hazards to rescuers (Atmospheric, Assess potential hazards to rescuers (Atmospheric,

water,Trench etc)water,Trench etc) Make The Trench Lip Safe – ground pads/ Ladder bridgesMake The Trench Lip Safe – ground pads/ Ladder bridges Shielding of patient – with material on site, plywood, Shielding of patient – with material on site, plywood,

backboard backboard Air monitoring – Bottom at patient, middle and top of trenchAir monitoring – Bottom at patient, middle and top of trench Apparatus Base Area with manager. location?Apparatus Base Area with manager. location?

Trench Scene ManagementTrench Scene ManagementExclusion ZonesExclusion Zones

Hot Zone 0 – 100 Hot Zone 0 – 100 ft.ft.

Warm Zone 100 – Warm Zone 100 – 150 ft150 ft

Cold Zone 150 – Cold Zone 150 – 300 ft. 300 ft.

Ground padsGround pads

For distribution of weight on trench For distribution of weight on trench edgeedge

Ladder Bridge Ladder Bridge

Review of Monitoring Values Review of Monitoring Values Atmospheric Level Action Monitor

Combustible /Flammable gas

10% of LEL If outside thespace correctatmosphere. If

inside the spacebegin exit

Alarms bothvisually and

audibly

Oxygen Less than 19.5%or greater than

23.5%

If outside thespace determine

problem andcorrect. If insidethe space begin

to exit

Alarms bothvisually and

audibly

Toxicity CO – 35 ppmH2S –10 ppm

If outside thespace determinecause of problem

and correct, Ifinside the space

begin to exit.

Alarms bothvisually and

audibly

Equipment FamiliarizationEquipment Familiarization

Strongbacks/Strongbacks/Uprights = Shoring Uprights = Shoring PanelsPanels

Timber Timber WalerWaler Palm nailer Palm nailer Airshore Airshore Speedshore Speedshore

Types of CollapsesTypes of Collapses

Spoil pile slideSpoil pile slide Excavated earth too Excavated earth too

close to the lipclose to the lip Heavy rain Heavy rain

increasing wt of pileincreasing wt of pile

Slough In / Lip slideSlough In / Lip slide

Slough failureSlough failure The loss of part of The loss of part of

the trench wallthe trench wall

Sheer WallSheer Wall

Shear wall collapseShear wall collapse section of soil that section of soil that

loses it’s ability to loses it’s ability to standstand

Toe FailureToe Failure

Toe failureToe failure Slough that occurs Slough that occurs

at the bottomat the bottom Found in location of Found in location of

fill dirtfill dirt

Bell Pier ConditionBell Pier Condition

Bell pier conditionBell pier condition Long term toe failure Long term toe failure

on both sideson both sides

Wedge FailureWedge Failure

Wedge failureWedge failure Occurs with Occurs with

intersecting intersecting trenches, T or L trenches, T or L TrenchTrench

Angled section of Angled section of earth falling from earth falling from the corner of an the corner of an intersecting trench intersecting trench

Assignments and Assignments and ResponsibilitiesResponsibilities

Extrication/ Entry TeamExtrication/ Entry Team– Developing plan for patient extricationDeveloping plan for patient extrication– Also personnel used for digging Also personnel used for digging – Assists Shoring Team to set shores Assists Shoring Team to set shores

Shoring TeamShoring Team– Assembling, placing and removing shoring & Assembling, placing and removing shoring &

walerswalers Panel Team Panel Team

– Place ground pads Place ground pads – Prepare and placement of panelsPrepare and placement of panels

TECHNIQUES FOR TRENCH TECHNIQUES FOR TRENCH PROTECTIONPROTECTION

Ops operating within trench Ops operating within trench Straight wall trench procedures:Straight wall trench procedures:

– Set middle set of panels as directly over Set middle set of panels as directly over the victim as possiblethe victim as possible

– For Pneumatic Struts:For Pneumatic Struts: Set middle shoreSet middle shore Set top shoreSet top shore Set bottom shoreSet bottom shore

TECHNIQUES FOR TRENCH TECHNIQUES FOR TRENCH PROTECTIONPROTECTION

Outside WalerOutside Waler– Uses outside walers to Uses outside walers to

span openingspan opening

Outside waler Outside waler procedures:procedures:– Place pickets to tie Place pickets to tie

walers walers – Place and tie off bottom Place and tie off bottom

of Walerof Waler– Place and tie off top of Place and tie off top of

WalerWaler– Set middle set of panels Set middle set of panels

as directly over victim as directly over victim as possibleas possible

Inside WalerInside Waler

Inside walers are Inside walers are used to span a set used to span a set of panels for the of panels for the purpose of creating purpose of creating an open spacean open space

The intersecting The intersecting “T” trench is a very “T” trench is a very unstable trench unstable trench because not only is because not only is one wall exposed, one wall exposed, but a section has but a section has been cut that been cut that intersects the other intersects the other wall.wall.

The “L” trench can The “L” trench can be describe as two be describe as two trenches that trenches that intersect at there intersect at there endsends

Deep trenches are Deep trenches are those trenches those trenches over 10 feet but over 10 feet but not more than 20 not more than 20 feetfeet

Pier-holePier-hole

Trench EnvironmentsTrench Environments

Take Home PointsTake Home Points Create a Hot, warm and cold Create a Hot, warm and cold

zonezone– Hot zone 0 – 100 ftHot zone 0 – 100 ft– Warm zone 100 – 150 ftWarm zone 100 – 150 ft– Cold zone 150 – 300 ftCold zone 150 – 300 ft

Call for help, location, Staging Call for help, location, Staging Control Traffic movementControl Traffic movement Shut down all heavy Shut down all heavy

equipment operating within equipment operating within 300 ft of the collapse300 ft of the collapse

Ladders for egress every 25 Ladders for egress every 25 feet.feet.

Ground padsGround pads Air monitoring Air monitoring Spoil pile moved 2 feet from Spoil pile moved 2 feet from

lip of trenchlip of trench

Questions?Questions?

Thank youThank you

For safety is not a gadget but For safety is not a gadget but a state of mind.  ~Eleanor a state of mind.  ~Eleanor

EveretEveret

Rotational FailureRotational Failure

Rotational failureRotational failure Scoop shaped Scoop shaped

collapse that starts collapse that starts at the lip and at the lip and transmits itself to transmits itself to the trench wallsthe trench walls