General Orientation

Rev. November 10, 2020

Trenching Procedure

This policy establishes the minimum requirements for practices and procedures to assure the safety of staff who work in or around excavations as part of their job duties. It also serves to protect staff, contractors or visitors who may work or travel in the vicinity of an excavation or trench.

Trenching Procedure

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Trench Work

· A Notice of Trench Work is required if a notice of project has not been acquired

· Familiarize yourself with the Soil Types and Trenching Procedures prior to entering a trench

· Equipment operators and supervisors shall ensure all trenching procedures are followed

· Be aware of your surroundings, including changes that may affect the stability of the trench

· Never jump into a trench, enter and exit a trench using a ladder or engineered steps

· Remain in visual contact with the operator if within the machines danger zone

· Work shall not be performed in a trench without adequate surface supervision

· If trench wall becomes unstable, worker is to exit trench immediately and no one will be permitted to enter the trench until it is redefined as safe by the supervisor

· All trenches shall be kept reasonably free of water

· Trench shall be excavated in a manner to allow room for workers, equipment and structures

 

Soil Types

Type 1 Soil

· is hard, very dense and only able to be penetrated with difficulty by a small sharp object;

· has a low natural moisture content and a high degree of internal strength;

· has no signs of water seepage; and

· can only be excavated by mechanical equipment. O. Reg. 213/91, s. 226(2)

 

Type 2 Soil

· is very stiff, dense and can be penetrated with moderate difficulty by a small sharp object;

· has a low to medium natural moisture content and a medium degree of internal strength;

· has a damp appearance after its excavated.  O. Reg. 213/91, s. 226(3)

 

Type 3 Soil

· is stiff to firm and compact to loose in consistency or is previously excavated soil;

· exhibits signs of surface cracking;

· exhibits signs of water seepage;

· if it is dry, may run easily into a well-defined conical pile; and

· has a low degree of internal strength.  O. Reg. 213/91, s. 226(4)

 

Type 4 Soil

· is soft to very soft and very loose in consistency, very sensitive and upon disturbance is significantly reduced in natural strength;

· runs easily or flows, unless it is completely supported before excavating procedures;

· has almost no internal strength;

· is wet or muddy; and

· exerts substantial fluid pressure on its supporting system.  O. Reg. 213/91, s. 226(5)

Wall Stability

A level area extending at least one metre from the upper edge of each wall of an excavation shall be kept clear of equipment, excavated soil, rock, and construction material.  O. Reg. 213/91, s. 233(1)

The stability of a wall of an excavation shall be maintained where it may not be affected by stockpiling excavated soil or rock or construction materials. O. Reg. 213/91, s. 233(2)

 

No person shall operate a vehicle or other machine and no vehicle or other machine shall be located in such a way as to affect the stability of a wall of an excavation.  O. Reg. 213/91, s. 233(3)

 

Barriers

If a person could fall into an excavation that is more than 2.4 metres deep, a barrier at least 1.1 metres high shall be provided at the top of every wall of the excavation that is not sloped as described below.

 

Sloping a Type 1 or Type 2 Trench

Made in Type 1 or Type 2 soil and whose walls are sloped to within 1.2 meters of its bottom with a slope having a minimum gradient of one horizontal to one vertical.  O. Reg. 213/91, s. 234(2)(e)

 

 

 

 

 

 

 

 

 

Sloping a Type 3 Trench

Made in Type 3 soil and whose walls are sloped from its bottom with a slope having a minimum gradient of one horizontal to one vertical.  O. Reg. 213/91, s. 234(2)(f)

 

 

Sloping a Type 4 Trench

Made in Type 4 soil and whose walls are sloped from its bottom with a slope having a minimum gradient of three horizontal to one vertical.  O. Reg. 213/91, s. 234(2)(g)

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