Asbestos removal in the Darwin Tower
January 2017: A description of what will happen during the removal of asbestos from the Darwin Tower
The Darwin Tower has been a major focus for the Asbestos Management team for a number of years. By design, structural steel work was coated with a fire protection product, commonly used in the 1960’s which contained asbestos, an effective fire retardant.
The University has followed the guidance of the Health and Safety Executive (HSE) and managed the asbestos in situ, or carried out localised removals to facilitate refurbishment projects up until now.
The guidance states that asbestos in a good condition is safe and that unless it is foreseeable that it could be disturbed, leaving asbestos in place is usually the most suitable option.
In order to highlight the asbestos the University coated the steel work with a thick specialised encapsulant and painted the steelwork bright (canary) yellow.
The masterplan for the School of Biological Sciences includes the major refurbishment of the Darwin Tower to create a state of the art teaching and research building. In order to transform the building as intended it is foreseeable that the asbestos would be disturbed and as a consequence, the University has opted to carry out a full, stand alone, asbestos removal project as the most effective way of safely removing all the asbestos prior to the main refurbishment of the building.
The University has appointed Forest Environmental (FE) as the Principle Contractor. Forest are well known to the University and are one of the largest Asbestos Removal contractors in the UK with a number of high profile clients.
Prior to any work starting on site, Forest as the asbestos licence holder, submit a 14-day notification to the enforcing authority, the HSE informing them of the works. The HSE have the statutory authority to visit and enter the site without notice to inspect the works.
The University adopts a best practice approach to asbestos removal and have appointed The Institute of Occupational Medicine (IOM) to carry out a range of air monitoring works. IOM are independent of the Asbestos Removal contractor and are on site, full time, to monitor all aspects of the removal works. They provide the University with objective assurance that all works are being carried out safely and in accordance with the Control of Asbestos regulations 2012, the University Asbestos Management Plan and the removal contractors plan of work and method statement.
IOM provide us with written assurance of the integrity of the asbestos enclosure, they will also confirm that it is under negative pressure before any works start. The air monitoring strategy is based on proximity to the enclosure and air-sampling pumps are placed around the perimeter to ensure that ambient background air quality is not altered by the work. Where risk assessment has identified areas where there could be a potential for asbestos fibres to be released into an occupied area, an additional sealed ‘buffer zone’ is created with polythene and timber to segregate both areas.The arrangements for air monitoring during the asbestos removal works is largely dependent on the location within the Darwin Building where asbestos is being removed. All the works are carried out under fully controlled conditions, this means that the area around the asbestos is fully sealed using polythene and timber to form an airtight enclosure. Large HEPA filtered extractor units are then fixed to the enclosure to draw air into the filters and provide negative pressure. This ensures that should any damage occur to the enclosure any asbestos fibres would be drawn in rather than blown out. Access and egress is controlled by way of a ‘3 stage airlock’ which contains a ‘dirty’ stage, a buffer stage and a clean end.
The range of monitoring work is not limited to outside of the controlled area and personal monitoring on Forest operatives will take place regularly to record fibre concentrations within the work zone to ensure that control measures are effective.
It important to remember that the objective of the removal work is to keep fibre concentrations as low as possible within the live asbestos enclosure. A number of techniques will be employed to ensure that fibre release is minimised at source (e.g. fibre suppressant injected into the asbestos to reduce friability). The exposure of the individuals carrying out the work is as important to us as those in the surrounding buildings and our obligations under the Health and Safety at Work Act and Control of Asbestos regulations extend to anyone who may be affected by the work.
One of the most important elements of the removal process is certifying that the asbestos has been removed from the work area and that the enclosure can be removed. Forest are responsible for removing all the asbestos and cleaning the enclosure to a standard where there is no dust or debris (of any kind) present within the enclosure. The Forest supervisor inspects all areas of the enclosure and when satisfied, requests IOM to follow the HSE’s ‘4-stage clearance’ procedure - a legal requirement for all removal of notifiable material. The most important part of this process is a detailed visual inspection of all areas of the enclosure to verify all dust and debris has been removed. This process can take hours or even days and is followed by a ‘disturbance’ air test. This is where IOM sample the air within the enclosure following the visual inspection and following all surfaces being thoroughly brushed. This is designed to ensure single microscopic fibres which may be present are made airborne and be collected by the air sampling equipment.
Once the samples have been collected, the filters are mounted and analysed. IOM will count any material present on the slide which meets the definition of a respirable fibre regardless of whether it ‘looks’ like asbestos or not. It is a non-discriminatory count. If fibre levels are below the limit of detection for this method (0.010f/cm3), Forest will be informed and the enclosure can be removed.
Transit and Waste
As detailed above the removal and monitoring within the area is as comprehensive as possible. It should also be noted that the procedures for transiting from the enclosure to the onsite decontamination units, and moving waste from the enclosure to the sealed asbestos skip are also defined in the guidance with recognised procedures for both.
The removal operatives use a colour-coded system of coveralls for each significant phase of their work. These are as follows:
- Red: working within a live asbestos enclosure
- White: Transiting from live enclosure to decontamination unit
- Blue: all other works including movement of asbestos waste.
It is detailed in the guidance that operatives should transit from the work area to the decontamination unit still wearing their respiratory protective equipment (RPE). The transit procedure is clearly detailed within Forests Method Statement/Plan of Work.
The operatives vacuum their coveralls and boots before carrying out primary decontamination in the ‘dirty’ stage of the airlock system. This involves removing all red protective coveralls, gloves, boots etc., wiping down the area around the mask and any exposed skin with a sponge. They then change into their white transit overalls and make their way to the decontamination unit.
The decontamination unit is a powered caravan type trailer with 3-stage system similar to that in the enclosure airlock. Operative enter the dirty end, remove their white coveralls and pass into the middle stage which contains a hot shower. At this point and after immersion in the shower, the operatives can remove their RPE before washing, passing into the clean end and changing into normal clothes.
The reason RPE has to be worn while transiting is that small amounts of dirt, which may contain asbestos, can get lodged between the mask and the face. This gives the potential for small exposures of operatives carrying out this work, should they remove their masks before showering, the guidance specifies the procedure detailed above and should not be a cause for alarm.
Additionally, the operatives moving waste from the work area to the sealed skip will also wear respiratory protection to guard against accidental breakages. The waste is bagged in the enclosure in a red plastic bag, sealed, then wiped down and passed through the airlock and into a clear plastic bag and then sealed again. The waste is then placed into a plastic trolley and wheeled to the skip.
IOM regularly monitor the waste and transit routes to ensure they are clean and free of all dust and debris as inspection of the route forms part of the 4-stage clearance procedure.
This process is carried out for each enclosure, details of the 4-stage clearance procedure can be found in the HSE Guidance: HSG248: Asbestos: The analysts guide for sampling, analysis and clearance procedures.
The guidance for Licenced contractors detailing decontamination procedures can be found in HSE Guidance: HSG247 Asbestos: The licenced contractors guide.
For information purposes there are emergency procedures in place should an elevated fibre reading be recorded out with the Darwin Tower. If this was in a single room, then the room only would be isolated with any occupants asked to leave, the removal contractor would decontaminate the room to the satisfaction of IOM and the University and adjacent rooms would also be inspected. IOM would carry out additional air tests to confirm that air quality levels had returned to expected background levels and would determine in conjunction with Asbestos Manager if there is any ongoing risk prior to an official incident investigation. If any individuals were in the room and fibre levels were in excess of the control limit for asbestos this would be reportable under RIDDOR, treated as a significant incident within the University and likely be further investigated by the enforcing authority.
It should be stressed that the controls being put in place by the asbestos removal contractor to segregate the tower from adjacent buildings and other contractors are comprehensive. There are limited areas of interface between the tower and other buildings, although air monitoring will be carried out, following risk assessment, beyond the buffer zone, as a reassurance exercise in these areas.