Access

Walkways

Access is very important in the tunnel construction and should be marked clearly for egress during an emergency or while construction and during operation stages. The walkways should be properly identified with the escape routes properly signed.

Minimum clear space of 2000 mm high and 900 mm wide, with the walking surface no less than 430 mm, should be maintained where possible. Where practicable, walkways should be physically separated from any traffic route, or additional precautions should be taken to safeguard any person using it during the passage of a vehicle. In a place where the minimum clearance could not be maintained, proper signages related to the visibility should be maintained throughout the passage of the tunnel.

Extra care must be taken for vehicles as well as workers working inside a tunnel due to unexpected dust and moisture. The proper signages that should be installed include:

• 1. recess constructed outside the general line of excavation;

  2. robust barriers between the safe position and haulage route;

  3. stages raised clear of any possible hazard.

Lighting is a crucial element that is needed to prevent any incident, therefore it should be provided to assist pedestrians as well as moving vehicles.

In a tunnel where there are areas of occasional access for inspection and maintenance and are unlit, proper reflective signages should be installed indicating the escape routes. All related PPE should be carried by the person entering such unlit areas. the PPE includes a hand/cap lamp and appropriate means of communication (BS 6164: 22.1).

MUST KNOW

According to the Alberta Occupational Health and Safety Code (current as of January 1, 2019) an employer must follow the following:

According to Part 8, Section 121(1)

An employer must ensure that a walkway, runway or ramp

(a) is strong enough to support the equipment and workers who may use it,

(b) is at least 600 millimetres wide,

(c) is wide enough to ensure the safe movement of equipment and workers, and

(d) has the appropriate toe boards and guardrails required by AOHS Part 22.

According to Part 8, Section 121(2)

An employer must ensure that the surface of a walkway, runway or ramp has enough traction to allow workers to move on it safely

Access for maintenance

Where access is intended to carry only maintenance or to transfer the material from one location to another, a safe system of work should address at least,

• 1. Minimum dimension for access;

  2. Adequate ventilation;

  3. Rescue procedure with due allowance for the reduced number of personnel on site, and obstruction in the tunnel;

  4. Gas detection equipment;

  5. Avoidance of lone working;

  6. Communication equipment.

Removal of machinery to the surface should be given more consideration, along with the construction of the maintenance shaft (BS 6164: 22.2).

Gradient

For slopes of less than 30°, pedestrian access can be achieved using a properly constructed stairway. However, for slopes exceeding this angle, specialized equipment like a bucket conveyor should be utilized for access (BS 6164: 22.3).

MUST KNOW

According to the Alberta Occupational Health and Safety Code (current as of January 1, 2019) an employer must follow the following:

According to Part 8, Section 122(1)

An employer must ensure that

(a) the width of the treads and the height of the rise of a stairway are uniform throughout its length, and

(b) the treads of a stairway are level.

According to Part 8, Section 122(2)

An employer must ensure that

(a) a stairway with 5 or more risers has the appropriate handrail required by this AOHS Code, and

(b) a stairway with open sides has a handrail and an intermediate rail or equivalent safeguard on each open side.

According to Part 8, Section 122(3)

An employer must ensure that temporary stairs are at least 600 millimetres wide.

Working at height in tunnels and shafts

Working at a greater height should be given more consideration due to the fall hazards. In work, such as bolts in tunnel linings or mesh in sprayed concrete linings, mechanical access should be used. In systems such as a fixed ladder with protection, access platforms or permanently installed movable platforms should be provided in operations of greater height where fall can be deemed as a hazard.

MUST KNOW

Alberta Occupational Health and Safety Code Relevant to the Topic

According to the Alberta Occupational Health and Safety Code (current as of January 1, 2019) an employer must follow the following:

According to Part 8, Section 119(1)

An employer must ensure that every worker can always enter a work area safely and leave a work area safely.

According to Part 8, Section 119(2)

An employer must ensure that a work area’s entrances and exits are in good working order.

According to Part 8, Section 119(3)

An employer must ensure that a work area’s entrances and exits are free from materials, equipment, accumulations of waste or other obstructions that might endanger workers or restrict their movement.

According to Part 8, Section 119(4)

An employer must ensure that, if a worker could be isolated from a primary escape route,

(a) there is a ready, convenient and safe secondary means of escape from the work area, and

(b) the secondary escape route is always readily useable.

According to Part 8, Section 119(5)

An employer must ensure that all workers are familiar with escape routes from the work area.

According to Part 8, Section 120(1)

An employer must ensure that doors to and from a work area can be opened without substantial effort and are not obstructed.

According to Part 8, Section 120(2)

An employer must ensure that a door used to enter or leave an enclosed area that poses a hazard to workers entering the area

(a) is kept in good working order, and

(b) always has a means of opening it from the inside.

According to Part 8, Section 123(1)

Alberta OHS Code Part 8, Section 123 applies to stairways with 5 or more risers.

According to Part 8, Section 123(2)

An employer must ensure that a stairway is equipped with a handrail that

(a) extends the entire length of the stairway,

(b) is secured and cannot be dislodged,

(c) is between 800 millimetres and 920 millimetres above the front edge of the treads, and

(d) is substantial and constructed of lumber that is not less than 38 millimetres by 89 millimetres or material with properties the same as or better than those of lumber.

According to Part 8, Section 123(3)

An employer must ensure that posts supporting a handrail

(a) are spaced not more than 3 metres apart at their vertical centres, and

(b) are constructed of lumber that is not less than 38 millimetres by 89 millimetres or materials with properties the same as or better than those of lumber.