12 May 2016
There is an associated risk whenever there is a requirement to reuse Brownfield sites due to the legacy left by previous occupants as asbestos could be present.
This can be due to a number of factors such as lack of asbestos removal during demolition, illegally burying waste and poor historical on site practices. Due to potential asbestos presence within a majority of Brownfield sites in the UK, there is significant activity ongoing in producing industry guidance to address this problem.
Asbestos in soil is now a major issue affecting the redevelopment of Brownfield sites impacting project costs and programmes especially when it is only identified late in the development process which can lead to very expensive retrospective remediation.
What is the issue of asbestos in soils?
There are two issues that arise during development works; the classification of asbestos in soil for waste disposal and at what levels a human health risk may arise and, as a result, remediation is required.
Waste containing more than 0.1% asbestos is classified as a ‘Hazardous Waste’ in England, Wales & NI and a Special Waste in Scotland, therefore removing this material off site can sometimes render a development uneconomic. The issues around classification have been subject of significant discussion within the Joint Industry Working Group (JIWG) and information can be found here.
It is recognised that even if soils contain <0.1% asbestos there may remain a risk to human health and the development of a new screening value is a subject of research being undertaken by the JIWG and SOBRA (Society of Brownfield Risk Assessors). The Construction Industry Research and Information Association (CIRIA) Guidance C733 Asbestos in soil and made ground: a guide to understanding and managing risks, was published in 2014 and provides consultants with background information on the toxicity and risks related to asbestos and assistance in assessing those risks.
Whilst the waste threshold is important, generally the key consideration is the context of human health and the development, for example, can asbestos in soils be retained on site through the provision of a clean cover system? Soils containing asbestos can be re-used under the CL:AIRE Code of Practice if there is a genuine need for fill provided that in its proposed location it does not represent a potential risk to site users or the wider environment. Therefore placing material in a suitable location on site becomes a viable alternative to an expensive disposal to landfill option.
WYG’s team of asbestos experts worked on a site in central London undergoing redevelopment. During the site investigation chrysotile and amosite asbestos were detected in soil in an area that the client intended to excavate to a depth of ~2m below ground level.
To assess the potential risks to workers who would be undertaking the excavation and subsequent building works, WYG undertook a program of air monitoring to determine if fibres were likely to be released during the works and the need for dampening down the works to prevent fibre release to air.
The results from monitoring at the two locations found air fibre concentrations of 0.0010 fib/ml and 0.0012 fib/ml which is significantly less than 0.01 fib/ml which is the reportable concentration of asbestos in air.
WYG recommended that soil dampening be undertaken during the works which reduced the requirement for remediation thereby saving the client significant programme and cost impacts.
Identifying asbestos in soils & How WYG Can help
To assist consultants and contractors working on sites where asbestos may be present, CIRIA has developed a new site guide which can be referred to and assists them in identifying asbestos which is visual to the eye.
WYG has been a member of the steering committee for this project drawing on our experience of working on asbestos contaminated sites. If remediation works or other excavation works are ongoing on site, it is important that the resident engineer is able to assess the soils and identify the presence of asbestos in order that appropriate action is undertaken and if the asbestos is found to be notifiable, the appropriate paperwork is filed with the HSE and a staff health monitoring program is implemented. WYG site engineers are trained to identify observable asbestos on sites and to implement the appropriate procedures to minimise project programme impacts.
Asbestos in soils can be safely and cost-effectively managed as part of redevelopment if the specialist consultant such as WYG is engaged early in the project. A majority of issues arise when asbestos in soil is identified late in the project and therefore more cost effective remedial options may not be viable due to programme and design restrictions. WYG adopt a phased approach to the investigation, risk assessment and remediation options/design phase to mitigate disruption to a project and ensure a cost effective and regulatory compliant remediation solution is implemented.
Our asbestos consultancy team is UKAS accredited for the provision of asbestos surveys and inspections (ISO 17020) along with air monitoring, 4 stage clearance & bulk analysis (ISO 17025). We are also UKATA certified for the provision of asbestos awareness training.
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