Construction Safety Week – Working Safely with Hazardous Substances
The standard reaction to hazardous substances on construction sites is often “Do you have the Safety Data Sheet?” (This will be Material Safety Data Sheet for those of a certain vintage!). It is a mistake to think that once the SDS is on file, the hazard has been controlled. In fact, the SDS should be reviewed to clearly understand the hazards, and this is then the perfect opportunity to review if any safer alternative products are available. If, despite the hazards, the substance is identified as the most suitable product for the task, then the following key sections (of the standard 16 sections of the SDS) need to be reviewed:
- First Aid Measures
- Handling and storage
- Exposure Controls / Personal Protection (i.e. PPE)
- Disposal considerations
Information in the other sections is also important, but can be more technical in nature, or require referencing after the above sections. A final important step is to incorporate the items identified into the method statement and ensure all personnel are briefed on the hazardous product they are using.
This process is straightforward for materials that come to site in a hazardous form (e.g. compressed gases, paints, adhesives), but some materials only present a hazard due to the process applied to them. An example would be timber products (including furniture) which are non-hazardous, but when cut, the wood dust (hard and soft wood) presents a hazard to human health.
Further, there can be the presence of hazardous substances in the ground we want to build on. This may be naturally occurring, or more likely from previous use and occupation of the site.
ORS has been involved as PSDP on a number of brownfield developments, where ground contaminated with hazardous substances. These projects included areas used as former petrol stations and medical facilities, which immediately suggest the potential for contamination.
One of the early steps of a project design team is to appoint expert consultants to survey existing structures (scheduled for demolition) for substances such as asbestos containing materials and lead paint. If these are identified, there are clear regulations and accepted good practice for removal of these materials, with controls in place to protect personnel.
Also in the early stages of a project, during site investigation works, soil and rock samples from boreholes and trial pits will be sent for laboratory analysis. As the site investigation report is generally interested in sub-surface ground conditions that affect the foundation design and stability of the structure, details on identified contamination may be vague. Advice from an environmental consultant is recommended.
A site investigation report on one of our recent projects, identified very low levels of ACMs, in just one trial pit. Following this, further trial pits were conducted, surrounding this location. Therefore, the area containing the ACMs was localised to a small corner of the site, and works could proceed for the development. As a further control, the supervisor was recommended to complete asbestos awareness training, in the unlikely event of ACMs in other areas of the site.
On another recent ORS project, heavy metals such as arsenic, mercury and lead were identified in the soil. Although the heavy metals were present at concentrations that allowed for the disposal as inert waste, the report was not clear on the hazard to the health of those on site and potentially exposed. An occupational hygienist was consulted to review the laboratory results of the testing and advise on controls. These controls included ensuring the ground is kept damp to avoid dust dispersal, protective overalls to avoid skin contact and avoiding any material leaving site on the tyres of vehicles. The final control was a for a static air monitor and individual dose monitor to confirm personnel are not exposed to any of the heavy metals becoming airborne. The results from the monitoring then fed into the hazard identification and controls for the rest of the project.
Although contaminated ground conditions can be costly to mitigate and the potential hazards can appear vague, early engagement with environmental consultants or occupational hygienists can provide an accurate assessment of the hazards and controls. The controls may appear simple, but are based on an understanding of the chemical hazards, and transfer methods (i.e. mercury can be absorbed via the skin). Most importantly, the controls protect the health of personnel working on site or with contaminated ground.
Overarching, through all review and consideration of contaminated ground, is that contaminated ground does not necessarily have to be removed from site. Providing the hazards from contaminated ground to site workers can be adequately managed and there is no residual risk to the permanent users or occupants, then it may be preferential to leave the contaminated ground in place. This may require an adaptation to construction techniques (especially in regard to foundation and/or piling design) or design of the structure. An environmental consultant and thorough analysis of the ground conditions will determine if it is feasible to leave the contaminated ground undisturbed.