Understanding a site's contamination characteristics is fundamental to a safer site investigation and, while CL:AIRE's CAR-SOIL document and CIRIA's Good practice site guide provide guidance on asbestos in soil and construction and demolition materials, there is still uncertainty around the procedures and precautions to take when drilling or intrusively investigating sites where asbestos could be present.
The potential for asbestos on site should first be considered using any available information, through a desk study or data from a previous site investigation. The information obtained can dictate which risk category the site falls under; low, medium or high.
Applying a preliminary risk category determines which control measures are needed for intrusive investigation. Consideration of the method of intrusive investigation will also help determine control measures; for example, trial pitting may result in a greater risk of exposure to asbestos in soil than window sampling due to disturbance of a larger volume of soil and the lack of containment. Having a properly trained and competent person on site to recognise any potential asbestos-containing materials (ACM) will identify any change in risk category, which can determine if a change of control measures is required.
Vigilance on site is important to identify risk, which is why having appropriate asbestos awareness training can help site staff to avoid exposing themselves and others to asbestos. Higher levels of task-specific training (eg, asbestos NLW training) are required where asbestos is known to be present.
While basic five-point personal protective equipment may generally be acceptable for low-risk sites, medium- or high-risk sites may require other measures including respiratory protective equipment. A minimum assigned protection factor of 20 should be worn and fit testing the mask ensures it is effective in protecting the worker. Disposable coveralls can stop the spread of asbestos fibres, as can personal and equipment decontamination and controlling access to a segregated area.
The primary exposure pathway for asbestos in soil is inhalation of airborne fibres. Therefore, dust suppression (by damping down) and preventing the release of asbestos fibres should be a key control measure. Asbestos air monitoring can provide reassurance that workers and other parties have not been exposed.
Even with a thorough risk assessment, emergencies do happen
Where sampling of the potential asbestos-contaminated soils or ACM is required to enable positive confirmation by laboratory analysis, the procedure for sending samples to the laboratory must also follow a strict and controlled process to minimise risk through secure and sealed bags, clear labelling systems and recorded chain of custody.
Even with a thorough risk assessment, emergencies do happen and having a plan for dealing with an uncontrolled disturbance of asbestos fibres due to disturbance must be effectively managed to control and minimise exposure.
Having an emergency procedure in place is best practice for any risk-based scenario. Knowing how to effectively deal with an uncontrolled release of asbestos fibres can minimise exposure and safeguard human health.
For more information about the BDA, its health and safety programmes and guidance, or about becoming a member, visit www.britishdrillingassociation.co.uk.