In the fourth part of my summary of the new draft Asbestos Analyst’s Guide from the HSE – I’m concentrating on soils.
For those of you who have read either of my other summaries – this stand-alone article is a continuation.
If you want to read the first three instalments:
Part 1 – Appointing the right asbestos analyst
Part 3 – Reoccupation certificates and clearances
You can download a PDF of the complete white paper on the new analyst guidance here.
This time I am concentrating on the age old, but simultaneously new issue of asbestos in soils.
It should be remembered the HSE’s interest starts and ends with protection of the worker and others directly affected by the project. There is a very real difference between HSE and Environment Agency take on asbestos in soils. Another much more ambitious and targeted document on this other angle is:
‘Asbestos in soil and made ground: a guide to understanding and managing risk’.
CIRIA 733 must be read to gain any proper understanding of the subject.
My usual health warning – this is obviously a summary and clearly not intended to replace the Guide. The appendices contain a lot of important detail and should still be studied to gain the fullest picture. Finally, this is a review of the ‘draft for consultation’ – there may well be changes before final publication.
Asbestos surveys are required under the duty to manage and the current Construction Design and Management (CDM) Regulations. Where there is ‘a reasonable expectation that asbestos would be, present and could present a risk to workers’– surveys must be completed. This is no different for the ground.
This is an area of asbestos analytical work that has been too long ignored, but growing dramatically. Historically – poor surveys and removal projects have failed to identify or remove asbestos containing materials (ACMs). Subsequent demolition would therefore create contaminated rubble to enter the aggregate supply chain. QED. Other than poor practices, there are other reasons:
The guide specifically states that speculative sampling should not be undertaken. We’re told only complete soil investigation if other (desktop) analysis indicates that there is a risk:
However, as I said in the introduction, the potential source of contamination is very broad and could be totally unrelated to the list given us in the guide. I agree – don’t do speculative sampling, but if there is planned ground works – asbestos surveys should be mandatory.
ACMs present in contaminated land can vary from whole sheets of asbestos or sections of pipe insulation to smaller fragments. Clearly, condition will deteriorate over time, leading to the presence of fibre bundles. When lying close to the surface and especially when the ground conditions are dry, fibres can be readily disturbed and released to the air. It is this interface with the air that brings the risk to the worker.
The desktop study and subsequent survey (if deemed necessary) should determine the risk to workers doing the digging. The risk assessment should establish the locations(s) of asbestos in the ground and identify the type, product, condition and amount (e.g. areas/depths). Soil type and moisture content are also key. Adequate controls can then be designed and implemented. Clearly discoveries during the project may require us to revisit the assessment.
The guide suggests a targeted approach.
Careful examination and picking of the area *. This would allow the surveyor to present the lab with larger pieces of ACMs (about 3-5cm2) and smaller pieces of debris and fibre bundles as distinct samples.
*Sieving may also help to separate the coarse fraction (stones etc.). Detailed procedures on decontaminating the sieve to prevent cross contamination of samples is needed.
The team’s task is to hunt out asbestos and only present suspect materials to the lab. To get any type of risk assessment, there would have to be an adjustment factor (suggested at ‘x 0.1’) – this would allow for the fact that the ACMs were collected over a much larger area.
This method has the advantage that a large area of the site can be covered more quickly. Its principal use is to establish if a main survey is needed. It will also allow a main survey to be better planned.
A note of caution – the naked eye, in site conditions, is especially vulnerable to fatigue. When you add the likely requirement for wearing safety glasses – the potential for missing ACMs must be acknowledged.
The guide indicates in the appendix that the targeted method is suited to the Preliminary Survey, but the Main Survey (if needed) would employ the traditional approach.
Select the sample points and carefully map the area (including depth).
The normal approach is to reduce (using coning and quartering) a 1m2 area of soil down to a 1-2 litre or 1-2kg sample. This is a method to reduce the sample size without creating a systematic bias. The technique involves mixing the sample, pouring it into a conical shape, flattening it out into a cake and dividing the sample.
Image courtesy of Eija Alakangas, Technical Research Centre of Finland VTT Ltd.
The exercise should be repeated to get to the end sample size of approximately 1kg.
The soil type at the depth should be detailed to allow greater understanding (i.e. made ground, sandy, clay etc. will all have an influence on the final risk assessment). All should be logged on a site plan. This will allow not only a register of what has been identified – but can also be compared with previous site plans to better target further investigations. E.g. an old site plan indicates that a boiler room used to stand where a few positive samples were taken.
Whichever method is used, the guide highlights an important safety issue in that the activity should be done at the surface and the surveyor should not enter trenches or holes, unless properly shored up.
Laboratory identification of asbestos is obtained using the standard analytical methods. However, there is significantly more preparation required. Concentrations of dispersed fibres down to approximately 0.001% can be identified using the standard method – but I have found that this is very dependent on how long the analyst is prepared to look (20 minutes is suggested).
Quantification is critical to develop an assessment of risk; an appropriately accredited lab must therefore be selected. In such cases, results would be reported as a weight for weight (w/w) percentage of the matrix. Note the current rules for hazardous waste is 0.1% w/w, or (crucially) if any visible fragments of ACM are in of themselves >0.1%. This would mean (taken to extreme) a single 10p sized piece of AIB or cement in an otherwise clean load would render it hazardous waste.
I am not detailing too much that appears in the appendices in this summary – however, there is a table in appendix 2 which seems to contradict this:
The presence of ‘XXX’ indicates it is unfinished, but the guide seems to be adrift of what I understand is the hazardous waste rules.
These surveys, coupled with ‘near source’ and ‘far source’ air testing (see my second summary here), should be used to assess the risk and design the control measures.
As with all asbestos controls, the starting point is don’t disturb it, but as the land is due for remediation this is unlikely to be a solution. The guide states that where there is mostly bound asbestos in soils below 0.1% w/w, airborne levels are unlikely to exceed 0.001f/ml. However, where this is free fibre and especially in dry soils – the fibre release can be greater. Just like with standard asbestos removal suppression is a key element of any designed control.
The guide produces a flow chart to clarify the decision-making process, but I think it will get reworked before final publication. I will not reproduce it here, but the chart indicates that if samples identify asbestos that is buried and unlikely to be disturbed – it should be reported as ‘no asbestos found’ – certainly a typo. The principle will likely be that if the asbestos is buried and unlikely to be disturbed it will present no risk to the workers and therefore as the guide is only interested in these workers – we’re back to where I started – leave it alone.
Because of our historic failures, this whole area of remediation is where the future of the industry lies – as we strive for an asbestos free world.
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