Excavation Trenching Shoring

Excavation and Trenching The hazards of excavation & trenching and how to control them

Developed by Division of Occupational Safety and Health  August, 2009

Excavation and Tenching Opeations

Course objective: to provide a basic overview of the excavation, trenching and shoring regulations located in Part , chapter !"#$% '(C)

Topics covere covered d $

*azards of trenching & excavation

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+oil classification

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Trench protective sstems - shoring & sloping

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.ther hazard controls

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Common violations

'hat is an Excavation/ 

 An excavation is any peson!"ade cut, cavity, tench, o depession in the eath#s suface$

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 A tench is an excavation

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E"ployees "ust be potected fo" cave!in %hen the excavation is & feet o "oe in depth$

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'ave!in potection is not e(uied %hen) ! Excavations ae "ade entiely in stable oc*+ o 

! They ae less than & feet in depth and exa"ination of the gound by a co"petent peson povides no indication of a potential cave!in$

% 0atalities 1elated to Excavation (ctivities in 'ashington +tate %""2 - !332 Tpes of 4ncidents

+oil collapse 5cave$in6 7 8 +truc9 b machiner 7  +truc9 b motor vehicle 7 % +truc9 b falling object 7 % Electrocution 7 % 0all 7 %

'hat ma9es trenches hazardous/ The factors shown in this illustration can create deadl conditions for wor9ers) The spoils pile and the e;uipment being too close to the vertical walls of the trench are called etermine soil classification through testing

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Choose the correct protective sstem for soil tpe

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Berif protective sstem installation and set$up

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Provide safe access

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Compl with re;uirements specified in the Excavation, Trenching, and +horing regulations) Conduct dail inspections prior to the start of wor9, after an weather event, and as needed)

0irst: ou must locate utilities before digging

Go to:

www.callbeforeyoudig.org or Call %$233$!$ 4tAs 0ree

Fnderground 4nstallations 5utilities6 Dou are re;uired to to call for utilit locates and once the locates have been identified onsite, the emploer must do an exact locate as specified by: '(C !"#$%$#5!65c6 :;hen excavation opeations appoach the location of undegound installations, the exact location of the installations shall be dete"ined by safe and acceptable "eans$<

'h do ou need to do exact utilit locates/ ecause the are rarel spot$on, and older installations ma not show up on current utilit maps)

 Controlling heav vehicle surcharge loads 'hat does the $degree angle represent/ 4t represents the zone of influence or affected area) 4n other words, it represents the shear plane 5wea9est area6, at which the excavation or trench wall will fail, and that is wh it should alwas be 9ept clear of heav e;uipment or machiner, and the spoils pile, unless the trench can be properl shored)

Controlling water accumulation 'ater accumulation in a trench is hazardous because it erodes and changes soilG which means the stabilit of the soil is li9el wea9ened) Prevent water accumulation b using sump pumps, or create diversion ditches and di9es for natural drainage of streams interrupted b the excavation or in anticipation of heav rainwater runoff, or consult with an 1PE) +pecial supports or shield sstems ma be needed if water accumulates on the trench floor)

'ater (ccumulation Control +stem 'ater accumulation hazards should be prevented b either using a special support or shield sstems designed for water drainage issues, or water removal to control the level of accumulating water, or use of a safet harness and lifeline b wor9ers inside excavation) 'ater controlled through the use of pumps and other e;uipment setups must be monitored b a competent person to ensure proper operation) >iversion ditches, di9es, or other suitable means should be used to prevent surface water or rainwater from entering and accumulating in the excavation)

 A %ate contol syste" that got out of hand1

Classifing +oils 4t is important to correctl classif soil tpe before selecting and using a protective sstem) 4n order to classif soil, at least one visual test and one manual test are re;uired to determine if the soil is Tpe (, Tpe , or Tpe C) =ost enginees agee that less than 3> of the soil in ;ashington can be classified as Type A, and as soon as the Type A soil is distubed, it "ust be do%n gaded to a Type ?$ OTE) f you designate the soil as Type ', no testing is e(uied$

+oil characteristics Tpe (: Hood cohesive soil with a high compressive strength such as: cla, silt cla, sand cla, cla loam and cemented soils such as caliche, duricrust and hardpan

Tpe : Cohesive soil with a moderate compressive strength such as: silt, silt cla, sand cla, cla loam, silt loam, sand loam, angular gravel 5similar to crushed roc96, an previousl disturbed fissured or soil or subject to vibration

Tpe C: Cohesive soil with a low compressive strength such as: granular soils including gravel, sand, and loam sand or submerged soil or roc9 that is not stable or soil from which water is freel seeping

+oil classification 

Tpe oesnAt crumble *ard to brea9 up when dr Examples: I Cla I *ardpan I +ilt or sand cla, cla loam

'lay @oa"

'lay  As "oe oganic "atte, silt and sand 6 togethe *no%n as loa"7 gets "ixed in and as the gains get lage, the classification %ill be degaded to type ?$ As the "ix has less and less clay and oganic "atte in it beco"ing close to pue sand o gavel it

+oil Classification Tpe ( Even if soil has high cla content and is plastic when moist, it cannot be classified as