EXCAVATION/TRENCHING

PRIOR TO OPENING

1. Prior to opening an excavation, check excavation permit if any.

2. All underground installations (i.e. sewer, water, fuel, electrical
and communication lines, etc., shall be located and protected from damaged or displacement.
3. Trees, boulders, stumps, or other surface encumbrances located
so as to create hazards at any time during operations shall be removed before excavation is
started.

DURING OPERATIONS

1. Men working in deep trenches shall wear goggles and hard hats as a protection against falling
objects or materials.
2. Excavated materials shall be stored and retained at least 1.0 meter from the edge of the
excavation and at a distance to prevent excessive loading on the face of the excavation.
3. Boulders or other materials such that may slide or roll into the excavation shall be removed or
made safe.
4. Do not stockpile materials or store equipment nears the edge of excavation, excessive loading
on the face of excavation will tend to collapse.
5. Special attention shall be given to side slopes, which may be adversely affected by weather,
moisture content or vibration.
6. The sides of excavations 4.0 ft. or 1.22 meter or more in depth unless in solid rock, hard shale,
or cemented sand and gravel shall either be sloped to the angle of repose or be supported by
sheeting, shoring or other support systems.
7. Where it is necessary to undercut the side of an excavation, overhanging material shall be
safely supported.
8. Pick and shovel men working in excavation/trenches shall keep a sufficient distance apart so
they cannot injure each other.
9. Where excavations are to be made below adjacent foundations of structures, such foundations
shall be supported by adequate shoring, bracing underpinning or other supports shall be
inspected daily and after every rainstorm or other hazards increase occurrence by a competent
person.
10. Ground water shall be controlled. Diversion ditches dikes or other suitable means shall be
constructed and used to prevent surface water from entering an excavation/trenches.
11. Where pedestrian and vehicular traffic is to be maintained over or adjacent to excavations,
proper safeguards should be provided, such as walkways, bridges, guardrails, barricades,
warning flags or lights.

EQUIPMENT OPERATIONS AT EXCAVATION

1. If it is necessary to operate power shovels, trucks, materials or

heavy objects on a level above and near an excavation, the sides of excavation shall be sheet
piled, shored and braced as necessary to resist the extra super imposed loads.
2. Excavating or hoisting equipment shall not be allowed to raise,
lower or swing loads over personnel in the excavation without substantial overhead protection.
3. When mobile equipment is utilized or allowed adjacent to
excavations, substantial stop logs, warning signs, or barricades shall be installed.
4. Do not work too close to the cliff or edge of the excavation.
Avoid rework due to cave in.
5. When starting the machine to move forward and backward,
sound the horn or give signals to ensure safety.
6. Always pay attention to the people around the machine.
7. Always provide a signalmen for the safety of the workers.
8. If concrete placement will be done at the excavation, stop logs
shall be placed near the edge of excavation

During Break Times

1. Workmen shall never stand or take rest on high banks of soft

material where there is danger of a cave-in.

Access to Excavations

1. Excavations over 1.0 meter deep should be by ramps, ladders and stairways. Workmen
should not jump into the trench and shall not use the bracing as a stairway.
2. Ladders used as access-ways shall extend from the bottom of the trench to not less than
3.0 ft. or 91. 44 cm above the surface. Lateral travel to an exit ladder shall not exceed 25.0 ft.
or 7.62 meters.

After Operations

1. Guardrails, fences or other barricades and warning lights or other illuminations maintained
from sunset to sundown shall be placed at all excavations.
2. No tools, materials or debris should be left in walkways, ramps, or near the edge of
excavations. Such material might be knocked off or cause a worker to loose his footing.
3. Guardrails

Excavation in Confined Spaces

1. Check the atmosphere condition before entry

2. Do not work alone in confined space.
3. Provide life line
4. Provide ventilation or blower before entering the confined
spaces.
5. Emergency rescue equipment such as breathing apparatus,
safety harnesses and line and basket stretcher shall be readily available where adverse
atmospheric conditions are suspected or may develop in excavations.

GUIDELINES FOR EXCAVATION WORK

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This guideline provides a standard for proper sloping and shoring of trenches and excavations. It is
intended to give excavation contractors and workers practical information relating to the
requirements of the regulations pertaining to excavation work.

This guideline contains general information about excavation work. For specific regulatory
requirements regarding excavation work please consult the regulations adopted under the
Workplace Safety and Health Act.

I. DEFINITIONS

- Deep Foundation means a foundation unit that provides support for a building by
transferring loads either by end bearing to soil or rock at considerable depth below the
building, or by adhesion or friction or both, in the soil or rock in which it is placed.
- Excavation means a man-made cavity or depression in the earth's surface formed by
earth removal, and includes a trench, deep foundation, tunnel, shaft, or open
excavation, but does not include borrow pits, gravel pits and quarries, unless specified
by a safety and health officer.
- Open Excavation means an excavation where the width is equal to or greater than
the depth.
- Pile or Caisson means a slender deep foundation unit made of materials such as
wood, steel or concrete or combination thereof, which is either premanufactured and
placed by driving, jacking, jetting or screwing, or cast-in-place in a hole formed by
driving, excavation or boring.
- Professional Engineer means a person who is a member of the Association of
Professional Engineers and registered as a professional engineer under the
Professional Regulation Commission or who, being a non-resident, is in possession of
a subsisting license granted under this Commission.
- Shaft means a vertical or inclined opening excavated below ground level.
- Sheating means a continuous row of wood or steel sheets in close contact to provide
a tight wall to resist the pressure of the walls of an excavation.
- Shoring means a construction procedure used specifically to maintain the stability of
the walls of an excavation and provide protection to workers who may enter the
excavation.
- Shoring means a construction procedure used specifically to maintain the stability of
the walls of an excavation and provide protection to workers who may enter the
excavation.
- Strut means a horizontal cross-member of a shoring system that directly resists
pressure from a wale or upright.
- Support Structure means a shoring system required to maintain the stability of the
walls and ceiling of an excavation and includes a trench cage.
- Trench means an excavation having a depth which exceeds its width measured at the
bottom.
- Trench Cage means an approved steel support structure designed to resist the
pressure from the walls of a trench and capable of being moved as a unit.
- Trench Jack means a screw or hydraulic jack used as a brace in a shoring support
structure.
- Tunnel means a generally horizontal excavation more than 1 meter in length located
below ground level.
- Uprights means the vertical members of shoring that are placed up against and
directly resist pressure from a wall of a trench.
- Waler means a shoring member that is placed against and directly resists pressure
from sheating or uprights.

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II. HAZARDS TO EXCAVATION WORKERS

Why do serious injuries and fatalities to workers continue to occur in the excavation
industry?

It is because both employers and workers often forget that when they remove earth from
the ground, they are creating a situation where extreme pressures may be generated at
the face of an excavation. There is no longer material available to support the walls of the
excavation. Engineering controls must be utilized to provide a safe and healthy workplace
within the excavation.

Remember that:

- No one can predict accurately if an excavation is safe to enter without a proper

support structure being provided.
- A worker does not have to be completely buried in soil to be seriously injured or
killed. Workers who have been only buried up to their waist have died as a result of
the pressures exerted by the soil on their bodies.
- Excavations in or near "back-filled" or previously excavated ground are especially
dangerous since the soil is "loose" and does not support itself well.
- Water increases the possibility of a cave in. The increased water pressure
exerted on the soil can be the final factor in causing the walls to collapse.
- Clay can be extremely treacherous if dried by the sun. Large chunks of material
can break off a trench wall after having been stable and solid for a long period of time.
- It is not safe to assume hat because the walls of an excavation are frozen that it is
safe to enter. Frozen ground is not an alternative to proper shoring.
- An excavation should be considered a confined space and appropriate evaluation
and controls undertaken to ensure workers are not exposed to contaminated
atmospheres.
- Shoring must be adequate to overcome additional pressures from piles of
excavated material, adjoining structures, vehicular traffic, and nearby equipment.

III. WHAT TO DO PRIOR TO EXCAVATING?

1. Make sure you are a registered contractor

All employers undertaking excavation work are required to notify the Workplace Safety
and Health Division and obtain a registration number. Once this number is obtained,
the employer is considered a registered excavation contractor. If an employer is not
performing excavation work safely, then a Safety and Health Officer may revoke the
registration and the employer cannot do any more excavation work.

An employer may re-apply for registration, but must prove to the satisfaction of a
Safety and Health Officer that he/she understands the requirements of the excavation
regulation and will perform excavation work safely. Contact the division if you are not
registered.

2. Notify the division prior to excavating

Every excavator who intends to make trench excavation in excess of 1.8 meters (6
feet) or an open excavation exceeding 2.4 meters (8 feet) in which a worker may enter
must notify the Division not more than 48 hours prior to beginning the excavation. The
Division will assign a serial number for that excavation.

The following information must be provided to the Division at the time of notification:
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 - the excavation contractors registration number
- the name and address of the owner of the land where the proposed excavation is
to be made
- the name and address of the employer, principal contractor, municipality, public
utility, or agency of the government proposing to excavate
- the location of the proposed excavation and the date of the commencement of the
work
- a description of the proposed depth, length, and width of the excavation
- a description of the proposed method of shoring, including the type of shoring
materials to be used
- verification that the appropriate utilities have been notified and that the location of
any pipes, conduits, or previous excavations in or adjacent to the proposed site
has been determined and
- the name of the on-site worker supervising the excavation

3. Obtain clearance from the public utilities

Serious accidents have occurred in the past when excavators have made contact with
a gas or energized electrical line causing fires, explosions and injuries.

An excavation cannot be started until all the public utilities (including telephone, hydro,
gas, steam, etc.) have been notified and the accurate location of all underground
facilities has been determined.

If damaged to any pipe, cable, or other underground facility occurs once the
excavation has started, the employer must contact the utility immediately and advise
them of the contact. No further excavation work should proceed until the utility has
undertaken an on-site inspection. The workers must be evacuated from the worksite if
an energized cable is exposed or dangerous fluid or gases are released.

Where a worker or any portion of excavating machinery or equipment may come

closer than 3 meters (10 feet) to an overhead or underground electrical power line, the
public utility must be contacted and permit authorization obtained.

4. Obtain engineering approvals

An employer must engage a professional engineer to provide design information and

approvals for shoring support structures where a worker/s are required to enter an
excavation:

- where a straight-cut trench excavation exceeds 4.5 meters (15 feet) in depth or
1.5 meters (5 feet) in width
- where, in the opinion of a Safety and Health Officer, a shoring support structure is
required to be designed due to the nature of the excavation or soil conditions
- where a trench cage is to be used as a shoring support structure
- for all shaft and tunnel excavations
- for all deep foundation (caisson, pile) excavations or
- where the excavation may affect the structural integrity of an adjacent building,
foundation, utility pole or other structure.

5. Plan for dangerous conditions

A hazard assessment must be undertaken to determine the risks associated with

workers entering an excavation. Possible hazards include:

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 - explosive and toxic atmospheres
- lack of oxygen
- restricted access and egress
- flooding
- utility contacts (electrical, gas, steam, etc.) and
- human factors (phobias, mental and physical conditions)

If a risk assessment reveals that there is a confined entry hazard in an excavation,

then a proper work plan must be developed.

For example, in cases where a toxic or hazardous atmosphere may exist or could
reasonably be expected to exist in an excavation, the employer must test the
atmosphere and control worker exposure to the hazard. (For example, this may occur
in excavations where there are accumulations of gasoline vapors due to leaking
underground task. There are also situations where there may be elevated carbon
monoxide (CO) levels or a lack of sufficient oxygen in the excavation.)

What to do:

a) The employer must test the atmosphere prior to entry into the excavation. If an
unsafe atmosphere exists ventilation must be provided to maintain safe working
conditions.
b) If it is impossible to maintain a safe atmosphere by providing engineering controls
and a worker must enter the excavation. Then a proper supplied air respirator
and emergency evacuation procedures must be provided.
c) If other hazardous conditions such as potential flooding of the excavation exist,
then the employer must establish a safe working procedure. This may include
provision of safety harnesses and lifelines to allow workers to be removed from
the excavation immediately, should the hazardous condition develop.

6. Train the workers

An effective training program must be developed and delivered to excavation workers.

Prior to a worker beginning excavation work, the employer must instruct each worker
in proper and safe work procedures. This includes making the worker aware of the
hazards associated with excavations and any emergency procedures or rescue
methods that may have to be utilized.

7. Appoint an experienced supervisor

The employer must ensure that an experienced and trained worker is designated to
directly supervise each excavation project. This worker must be familiar with all
aspects of excavation work, from shoring requirements to emergency rescue
procedures. The supervisor must directly supervise all excavation work during the
entire period the workers are in the excavation.

IV. GENERAL SHORING REQUIREMENTS

1. Personal Protective Equipment (PPE)

All workers doing excavation excavation work must wear CSA approved Grade 1
safety footwear and safety helmet. Additional personal protective equipment may be

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 required, depending on the risk assessment for the work to be undertaken (i.e. hearing
protection, hand protection, etc.)

2. "Observer" to be on the job

The employer is required to ensure that there is always an experienced worker

designated to be the "observer" for trench excavations. This worker is responsible to
remain on the surface and keep the trench and workers under observation for unsafe
conditions.

3. Provision for access/egress

A suitable means of access and egress must be provided for workers entering an
excavation. This is usually provided by means of a ladder or stairway. Ladders must
extend 1 meter (8 feet) above the top of the excavation. In a trench excavation, a
ladder must be located within 8 meters (10 feet) of a worker's working position.

If workers are required to cross-over an excavation, then a proper walkway with

suitable guardrails on all exposed sides must be provided.

4. Location of excavated materials and equipment

All excavated materials must be piled in a manner so that the material cannot roll back
into the excavation. The material must never be closer than 1 meter (8 feet) from the
edge of the excavation, and should be placed as far away from the excavation as
possible.

Tools, equipment, and heavy machinery shall not be placed or used near an
excavation where they may fall into the excavation or affect the structural stability of
the walls of the excavation.

5. Public protection and traffic control

All excavations, where the public has access, shall have a means provided to guard
the public from the hazards of the excavation project. This includes barriers and
signage to protect the public from falls, falling material, and excavating equipment.
Proper covers or fencing must be provided to prevent the public from access to the
excavation during "off" hours.

In the public traffic areas, adequate signage and barricades meeting the requirements
of the municipal or provincial highway authorities must be provided.

6. First aid

First aid and emergency supplies must be kept at the excavation project at all times. It
is recommended that at least one worker per shift be a trained first aider with CPR
certification.

7. Engineering information

Engineered design specifications for shoring support structures, including trench

cages, must be forwarded to the division before using the structures, and made
available at the excavation site to a Safety and Health Officer.

Design specifications shall include:

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 a) the size of the component members of the structure
b) the loads and types of soil conditions for which the structure is designed
c) how the system is to be constructed and utilized

The employer is required to construct all shoring systems in accordance with the
engineering design information provided.

V. TRENCH AND OPEN EXCAVATIONS

Shoring, or the proper sloping of an excavation must be provided where a worker is to

enter an excavation that is considered to be:

A. An open excavation exceeding 2-4 meters (8 ft) in depth. (An

open excavation is any excavation that does not meet the criteria of being a trench,
shaft, caisson or tunnel) or
B. A trench excavation exceeding 1.8 meters (6 ft) in depth (Fig. 1)

The shoring support structure must be designed to withstand all external forces that may
be caused by:

a) soil pressures
b) nearby structures
c) additional loadings and vibrations (heavy equipment, traffic, piled materials near the
excavation, etc.)

Unless approved by a professional engineer, shoring support structures must be installed

so that they are in firm contact with the walls of the excavation. This may require
backfilling of voids in the excavation up to the shoring support structure.

Frozen ground is not considered an alternative to proper shoring.

TRENCH EXCAVATIONS

A. Soil Categories

For purpose of establishing shoring tables for trench excavations, soils have been
categorized into three main types:

- stiff and firm soils -solid soils with substantial coheson and no water table
present. (i.e. good clay, stiff clay till, medium till)
- soils likely to crack or crumble -soil that can be excavated by hand tools, show
signs of cracking after excavating, and possess a low to medium moisture content
(i.e. heavily seamed silty clays, compacted clayey fill, and mixtures of clays and
silts); and
- soft and loose soils - soils easily excavated by hand with little or no cohesion
(i.e. sand, gravel, silt, organic soil, soft and wet clay, and loose fill)

B. Vee-Type (Sloped) Excavations

Instead of a shoring support structure, a safe method to protect workers in an

excavation is to slope the walls of the excavations at a grade of 1:1 (45 degrees) or
flatter. The 45 degree slope is required no matter what type of soil conditions exist
(Fig. 2)

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 A combination 1:1 (45 degree) slope and vertical face may be used, as long as the
vertical face does not exceed 1 meter (3 feet) and the overall depth of the excavation
is not greater than 5 metres (15 ft.) (Fig. 3)

To calculate the overall width of a sloped excavation, use the following formula: Width
= (2 X depth) + bottom trench width

C. Type of Shoring Material

The majority of wood shoring used in trenches is comprised of full dimension popular
planks and timbers. Spruce lumber is also acceptable as shoring material provided it
meets the shoring table requirements. The lumber must be construction grade No. 2
or better plywood used as sheating material in loose soils must be a minimum of 20
mm (8/4 inch)

Steel trench jacks may be used as struts, as long as they are equivalent in strength to
the wood struts specified in the shoring tables. The longer dimension of the trench
jack "foot" must be located perpendicular to the grain of the wood on the upright. (Fig.
5)

D. Trench Shoring Tables

The shoring tables and diagrams indicate the allowable size and spacing of wood
classifications of soil.

E. Shoring of Trench Excavations

When installing shoring within a trench type excavation, proper methods and
procedures must be followed to provide for a safe excavation. (Fig. 11)

Uprights, struts (screw jacks), wales, and plywood must be installed in accordance
with the shoring tables based on the soil conditions, depth, and width of the trench
excavation.

Installation of Shoring

When shoring is in progress, the bucket of the excavation machine must be placed in
the trench directly in front of the shoring being installed. The bucket will serve as
additional protection is a cave-in occurs.

A proper ladder must be provided in a trench or open excavation. The ladder must
extend at least 1 meter (3 ft) above ground level and be within 3 meters (10 ft) of a
worker's working position.

It is essential that shoring struts/jacks be installed from the top down. It is important
that the top (first) strut/jack be placed approximately 0.5 meters (18 inches) below the
surface, then the second strut/jack placed according to the shoring table. The
installation of the first and second strut/jack to support the vertical uprights is very
important as it stabilizes the excavation walls.

When plywood is used, the jack or strut must never be installed directly on to the
plywood. (If the walls move, the jack or strut could push through the plywood). Where
plywood is used, the jacks must be placed on the uprights that support the plywood.

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 Once the worker has a minimum of two struts/jacks placed on each set of uprights, the
worker can proceed to install the bottom strut/jack. There must be less than two
struts/jacks used on each set of shoring.

This procedure is to be followed with each set of shoring. Using this method, the
worker is protected by the bucket of the digging machine and the shoring already
installed.

Removal of Shoring

When removing shoring, the reverse procedure is used. That is, the struts are
removed from the bottom to the top. Remember, there MUST never be less than two
sets of uprights in place and the worker must always remain within the shoring in place
for protection.
If there is undue pressure felt when removing a strut or jack, it means that the soil has
moved and the trench must be backfill led up to the bottom jack before it is removed;
then up to the next jack and so forth. Remember, do not try to remove a jack with
undue pressure as it may cause a sudden collapse.

It is preferable to have the worker who installed the struts to be the one who removes
them. That worker will know if there has been a change in conditions, undue pressure
on struts or other potentially dangerous conditions.

F. Trench cages

A trench cage is a self-contained steel structure placed in an excavation (prior to a

worker entering) that is designed to withstand soil, pressures and protect the worker(s)
against soil cave-ins (Fig. 13)

Trench cages must be designed by a professional engineer and constructed inspected

and maintained in accordance with the engineering specifications. The design criteria
for a trench cage is normally based on 75 pounds per square foot of earth pressure,
per foot of depth of the excavation.

Where trench cages are designed to be "stacked" in deep excavations, these must be
secured in a manner to transmit the loading condition between cages.

Trench cages shall have continuous sides and extend at least 600 mm (24 inches)
above the vertical wall of the excavation.

Hoisting hookup and drag points on trench cages must be designed and engineer
approved. Workers working in a trench cage that is to be dragged forward, must be
protected against rigging failure by suitable protective screening or other means.

No worker is to work outside the protection of the trench cage.

G. Hydraulic/pneumatic shoring systems

Hydraulic and pneumatic shoring systems are advantageous because a worker does
not have to enter the excavation in order to put the supports in place. These systems
are often made of lighter weight material such as aluminum and can be handled
easily. Care must be taken to ensure that the systems are properly maintained and
not damaged when in use.

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 Hydraulic and pneumatic shoring systems must be certified by a professional engineer
to be equivalent to the requirements as specified in the trench shoring tables for the
particular soil conditions.

OPEN EXCAVATIONS

Excavations that are not considered to be trenches, caissons, shafts, or tunnels may be
classified as open excavations. A basement or foundation excavation for a building or
structure is a good example of an open excavation. If an open excavation exceeds 2.4
meters (8 ft) in depth, then the walls of the excavation must be vee'd-out or a shoring
support structure designed and installed.

A shoring support structure for an open excavation must be designed by a professional

engineer. Typical structures consist of heavy wood lagging supported by steel I-beams
properly installed into the foundation. The engineering specifications must include
complete details on the correct procedures to install the support structure and on-going
inspection criteria to ensure the shoring is maintained in a safe condition.

Be aware! An open excavation may become a trench excavation as the project proceeds.
A concrete basement wall constructed in an open excavation 2 meters (6.6 ft) deep, now
requires shoring or veein-out if workers are required to work on the outside wall between
the concrete and earth. (Fig. 14)

VI. SHAFT AND TUNNEL EXCAVATIONS

Shaft and tunnel excavations are used primarily in sewer, water, and other utility work and
include such procedures as vertical circular shafts, "hand" tunneling operations and fully
mechanized excavating systems ("moles")

GENERAL REQUIREMENTS

A. Confined Entry

Shaft and tunnel excavations are to be considered confined entry situations and a
hazard assessment and risk control analysis must be undertaken.

Where monitoring of hazardous atmospheres is required, the job site supervisor must
be equipped with suitable testing equipment (i.e. explosive meter, oxygen, and toxic
gas detectors) and be trained in proper monitoring procedures. It is recommended
that continuous monitoring devices be used where monitoring is necessary.

Ventilation systems must be put in place to provide a safe atmosphere where they
may be a lack of oxygen or unsafe accumulations of toxic vapors, gases, dusts, or
other harmful substances.

The ventilation rate at the work face of the tunnel shall not be less than 2.75 cubic
meter per second per square meter of face area (50 cubic feet/minute per square foot
of face area).

B. First Aid Facilities/Emergency Procedures

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 Due to the nature of work, it is important that proper first aid supplies be provided at
the excavation worksite. A first aid kit shall be provided at each shaft location. It is
recommended that at least one worker on each shift shall be a certified first aider with
CPR training. A basket stretcher and blankets must also be provided at each
worksite, as well as a "parachute-type" full body harness for hoisting a worker to the
surface, if necessary.

Workers shall be instructed on rescue procedures to be undertaken in case of a

serious accident or injury occurring in a shaft or tunnel.

C. Sanitary Facilities

The wash-up facilities at excavation worksites must be kept in a sanitary condition.

Provisions must be made to provide a supply of clean and warm running water, hand
cleaners, soap and towels for the workers to use.

D. Lighting/Electrical Installations

Underground excavations must be provided with a source of electrical illumination for

the full length of the tunnel and at the working face of the tunnel excavation [minimum
25 lux (2.5 foot-candles) of illumination]. In the event of electrical failure, an
emergency lighting system must be in place. This may consist of battery operated
flashlights suitably sized and located to assist workers in exiting the tunnel.

All electrical circuits in underground excavations must be installed in accordance with

the Phil. Electrical Code. Light bulbs shall be caged to protect them from physical
damage. Due to the moisture accumulations in such excavations, it is essential that
electrical wiring systems be properly grounded. Only electrical equipment and tools
that are doubly insulated or properly grounded can be used. It is recommended that
ground fault circuit interrupters (GFCI's he used for electrical circuits grounded.

E. Fire Protection

A minimum of two, 2A-10BC rated multi-purpose type fire extinguishers shall be

provided in each shaft and tunnel excavation. Any flammable or combustible liquids
must be stored in compliance with the Fire Code and dispensed only from safety
containers meeting requirements of CSA Standard B376, "Portable Containers for
Gasoline and other Petroleum Fuels".

Combustible scrap materials such as wood shoring components, shall not be allowed
to accumulate in the excavation. These shall removed at least daily.

F. Use of explosives

All blasting operations must be undertaken by a certified blaster who is qualified to

handle and use explosives. Explosives must be stored and transported in accordance
with both Transport Canada and Energy Mines and Resources Canada Regulations.

G. Access/Egress

Vertical Circular Shafts

Vertical drilled shafts, shored with steel sleeves, are normally provided access by a
straight fixed vertical ladder. Where the ladder exceeds 5 meters (15 feet) in length a
rest platform or proper fall protection must be provided. This can be done by providing

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 a worker with a full-body safety harness secured with a lifeline to a fall-arresting
device.

Shafts with Hoistways

In shaft and tunnel operations, the worker accessway to a shaft must extend the full
length of the shaft and completely separated from the hoistway in a manner so that the
load or hoisting device cannot come in contact with the workers. The accessway must
be equipped with a vertical ladder having rungs spaced at 300 mm (12 inches) on
center with a clear space of 150 mm behind each rung, and rest platforms (landings)
located every 5 meters (15 feet)

Both accessways and hoistways shall be provided at the surface with proper
guardrails having a top rail, mid-rail and toeboard. The accessway must have a
secured cover to prevent unauthorized entry and the cover is to be locked at all times
when not in use.

SHORING

All shafts and tunnel support structures shall be designed and approved by a professional
engineer in accordance with the provisions

A. Shaft and Tunnel Operations

A shaft that is to be excavated to a depth of 1.8 meters (6 ft) or more shall have
shoring installed continuously from 300 mm (12 inches) above the surface of the
excavation to the bottom of the shaft.

Soil shall not be exposed in lifts greater than 1.8 meters (6 ft) where workers may
enter, without the immediate installation of proper shoring.

Subject to confirmation by a professional engineer, vertical shoring must be equivalent

to full 75 mm X 200 mm (3' X 8") close shored timbers supported by 200 mm X 200
mm (8" X 8") horizontal wales [maximum 2.5 meters (8 feet) span not more than 1.8
meters (6 feet) on center and posted at the corners. For spans greater than 2.5
meters (8 feet0, the wales must be increased in size in accordance with engineering
specifications.

Subject to confirmation by a professional engineer, crown shoring shall not be less

than full 75 mm x 200 mm (3” x 8”) timbers that extend from the 10 o’clock position
around the roof to the 2 o’clock position. The shoring shall be put in place as digging
proceeds and as soon as possible after the “monkey hole” has been excavated.
Planks shall be fully over lapped at connection points. [75 mm (3”) minimum].

Crown shoring shall extend a maximum of 900 mm (3 feet) beyond the concrete
framing for the next “push”. The maximum length for crown shoring is 3.0 meters (10
feet) under stable soil conditions.

“Face” shoring is to be installed in all tunnels greater than 1.8 meters (6 feet) in
diameter and in tunnels at a lesser diameter where soil conditions may be unstable.

B. Vertical Circular Shafts

Steel sleeves are often used to shore vertical drilled circular shafts in cohesive soils.
The sleeves are usually made from unreinforced steel plate and have proved to

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 successfully prevent local “cave-ins” of blocks of soil and wet silt layers. Subject to
confirmation by a professional engineer, the following minimum criteria apply:

1. The steel sleeve must be in good condition, circular in shape when standing
upright, and the plates should have no cracks, bends, or buckles.
2. The shaft must be drilled, and its diameter should not be more than 50 mm (2”)
greater than the outside diameter of the sleeve.
3. The sleeve plate thickness should not be less than 10 mm (3/8”)
4. For shafts up to 2.4 m (8 feet) in diameter, adjoining sections of sleeves may be of
the same diameter, simply butted at the joints. For holes greater than 2.4 m (8
feet) in diameter, sleeve sections should be of varying diameter, allowing
successively lower sections to be placed inside upper sections in the manner of a
telescope. Sections of sleeves should have a minimum overlap of 300 mm (1
foot).

C. Personal Protective Equipment

A worker entering a caisson must wear a full-body safety harness attached to an

approved lifeline that is secured to a fall-arresting retrieval device located at the
surface of the excavation.

The worker must wear CSA approved footwear and headwear at all times. Safety
eyewear and other job-specific protective equipment may also be necessary.

TYPES OF SOIL COLLAPSE

1. General zone of exposure – the area where workers are exposed to mass soil/rock
movement.
2. Spoil pile slide – poor excavating procedures where the excavated material is not
placed far enough away from the edge of the excavation.
3. Side wall shear – common to clay-type soils which are exposed to drying
4. Slough-in (Cave-in) – common to previously excavated material, sand and gravel
mix.
5. Rotation – clay-type soils when saturated with water.

SPECIAL HEALTH AND SAFETY CONSIDERATIONS IN EXCAVATION

A. COMPETENT PERSON. The designated competent person should have and be able to
demonstrate the following:
 Training, experience, and knowledge of:
- soil analysis;
- use of protective systems;
 - Ability to detect:
- conditions that could result in cave-ins;
- failures in protective systems;
- hazardous atmospheres; and
- other hazards including those associated with confined spaces.
 Authority to take prompt corrective measures to eliminate existing and predictable
hazards and to stop work when required.

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B. SURFACE CROSSING OF TRENCHES . Surface crossing of trenches should be
discouraged; however, if trenches must be crossed, such crossings are permitted only
under the following conditions:
 Vehicle crossings must be designed by and installed under the supervision of a
registered professional engineer.
 Walkways or bridges must be provided for foot traffic. These structures shall:
- have a safety factor of 4;
- have a minimum clear width of 20 in (0.51 m);
- be fitted with standard rails; and
- extend a minimum of 24 in (.61 m) past the surface edge of the trench.
C. INGRESS AND EGRESS. Access to and exit from the trench require the following
conditions:
 Trenches 4 ft or more in depth should be provided with a fixed means of egress.
 Spacing between ladders or other means of egress must be such that a worker will not
have to travel more than 25 ft laterally to the nearest means of egress.
 Ladders must be secured and extend a minimum of 36 in (0.9 m) above the landing.
 Metal ladders should be used with caution, particularly when electric utilities are
present.
D. EXPOSURE TO VEHICLES. Procedures to protect employees from being injured or killed
by vehicle traffic include:
 Providing employees with and requiring them to wear warning vests or other suitable
garments marked with or made of reflectorized or high-visibility materials.
 Requiring a designated, trained flagperson along with signs, signals, and barricades
when necessary.
E. EXPOSURE TO FALLING LOADS. Employees must be protected from loads or objects
falling from lifting or digging equipment. Procedures designed to ensure their protection
include:
 Employees are not permitted to work under raised loads.
 Employees are required to stand away from equipment that is being loaded or
unloaded.
 Equipment operators or truck drivers may stay in their equipment during loading and
unloading if the equipment is properly equipped with a cab shield or adequate canopy.
F. WARNING SYSTEMS FOR MOBILE EQUIPMENT . The following steps should be taken to
prevent vehicles from accidentally falling into the trench:
 Barricades must be installed where necessary.
 Hand or mechanical signals must be used as required.
 Stop logs must be installed if there is a danger of vehicles falling into the trench.
 Soil should be graded away from the excavation; this will assist in vehicle control and
channeling of run-off water.
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G. HAZARDOUS ATMOSPHERES AND CONFINED SPACES . Employees shall not be
permitted to work in hazardous and/or toxic atmospheres. Such atmospheres include those
with:
 Less than 19.5% or more than 23.5% oxygen;
 A combustible gas concentration greater than 20% of the lower flammable limit; and
 Concentrations of hazardous substances that exceed those specified in the Threshold
Limit Values for Airborne Contaminants established by the ACGIH (American
Conference of Governmental Industrial Hygienists).
When testing for atmospheric contaminants, the following should be considered:
 Testing should be conducted before employees enter the trench and should be done
regularly to ensure that the trench remains safe.
 The frequency of testing should be increased if equipment is operating in the trench.
 Testing frequency should also be increased if welding, cutting, or burning is done in the
trench.
Employees required to wear respiratory protection must be trained, fit-tested, and enrolled
in a respiratory protection program. Some trenches qualify as confined spaces. When this
occurs, compliance with the Confined Space Standard is also required.
H. EMERGENCY RESCUE EQUIPMENT. Emergency rescue equipment is required when a
hazardous atmosphere exists or can reasonably be expected to exist. Requirements are as
follows:
 Respirators must be of the type suitable for the exposure. Employees must be trained
in their use and a respirator program must be instituted.
 Attended (at all times) lifelines must be provided when employees enter bell-bottom
pier holes, deep confined spaces, or other similar hazards.
 Employees who enter confined spaces must be trained.
I. STANDING WATER AND WATER ACCUMULATION. Methods for controlling standing
water and water accumulation must be provided and should consist of the following if
employees are permitted to work in the excavation:
 Use of special support or shield systems approved by a registered professional
engineer.
 Water removal equipment, i.e. well pointing, used and monitored by a competent
person.
 Safety harnesses and lifelines
 Surface water diverted away from the trench.
 Employees removed from the trench during rainstorms.

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 Trenches carefully inspected by a competent person after each rain and before
employees are permitted to re-enter the trench.
J. INSPECTIONS. Inspections shall be made by a competent person and should be
documented. The following guide specifies the frequency and conditions requiring
inspections:
 Daily and before the start of each shift;
 As dictated by the work being done in the trench;
 After every rainstorm;
 After other events that could increase hazards, e.g. snowstorm, windstorm, thaw,
earthquake, etc.;
 When fissures, tension cracks, sloughing, undercutting, water seepage, bulging at the
bottom, or other similar conditions occur;
 When there is a change in the size, location, or placement of the spoil pile; and
 When there is any indication of change or movement in adjacent structures.

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