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Alert: Explosion - Sewer Construction Using a Laser Device

  • ISSN: 1195-5228
  • Issued: September 1993
  • Content last reviewed: June 2009

Hazard Summary:

During the investigation of an explosion at a sewer repair project the ignition source was found to be the battery connection for the project's laser alignment device. Both laser and battery had been located in a manhole. Natural gas, seeping through the soil from a damaged temporary plastic gas line, was ignited by a spark from the battery connection. In the resulting explosion a worker was badly burned.

A battery inside a manhole, and not remote from it, may be a hazard. The laser manufacturer's written instructions apparently do not address battery location.

Location(s) and Sector(s):

Construction of underground piping systems. Also work in existing sewer manholes when tying into existing sewer lines which are considered a confined space.

Suggested Precautions:

The battery for a laser device should be located far enough from the manhole or sewer pipe to ensure that it will not act as an ignition source for explosive hazards originating in the excavation or in existing sewer lines. Extra-length conductors may be required and are available.

Legislative Requirements:

The Confined spaces requirements outlined in the Regulations for Construction Projects, Ontario Regulation 213/91, require an employer on a project including a confined space that workers may enter to perform work, to develop and maintain a written confined space program, to have a competent worker carry out an adequate assessment of the hazards related to the confined space before it is entered by a worker, and to have a corresponding adequate written plan, identifying the controls to be implemented for each one of the identified hazards (respectively sections 221.5. 221.6 and 221.7). Other confined space requirements, including an entry permit need to be implemented as well.

Even in those instances where no confined space exists, the employer must “take every reasonable precaution in the circumstances, for the protection of a worker” (Occupational Health and Safety Act, section 25(2)(h). This includes evaluating the hazards in the workplace and establishing adequate controls and a health and safety program implemented in the workplace.

This Ministry of Labour Alert has no legal effect and does not constitute and is not a substitute for legal advice. If you require specific assistance with respect to the interpretation of a legislative provision and its potential application to you please contact your legal counsel.

Remember that while complying with occupational health and safety laws, you are also required to comply with applicable environmental laws.

Please photocopy Ministry of Labour Alerts, distribute them widely and post them where people will see them.