Slurry Sealing (AKA micro surfacing) has been used widely for some time to extend the life of bituminous footpaths and roads as it protects the existing surface against further deterioration and the effects of water ingress. It appears, however, that changes in how the surface can be prepared have resulted in non-trivial problems in many parts of Edinburgh. The problem is fully explained in the briefing below which I received from a Council Officer yesterday.
Whilst I welcome the fact that making the work good will be the contractor’s responsibility, we must recognise the inconvenience this will cause residents and Council Officers.
Furthermore, the problem raises fundamental questions about the future viability and cost of using this approach. I have therefore asked Council Officers if the use of Slurry Sealing should now be reviewed.
Weedkilling was carried out several weeks before the slurry surfacing was laid. However, due to environmental legislation we are no longer able to use “residual” weedkillers, which remain active for a period after application, ensuring that the weeds are killed right down to the root and new seeds cannot germinate. We are now only permitted to use “contact” weedkillers which will kill off any visible vegetation but may not always kill the weed down to the root. In addition, it may be possible for seeds caught in cracks in the footway surface to germinate.
At the point when the slurry surfacing was carried out there was no visible signs of weed growth and dead vegetation was removed before applying the slurry. I suspect it is a combination of the above reasons, combined with the wet and mild weather we have recently experienced, that has caused the weed growth to be so prevalent.
The contractor has been instructed to carry out a further application of weedkiller, remove dead vegetation and repair any defects caused by the weed growth. As this is a design and build contract, the contractor will be carrying out the above works at no additional cost to the Council.
The weedkilling is planned to commence on Wednesday 30 August, weather permitting (weedkiller should not be applied when rain or strong winds are forecast), and will take 2-3 days to complete all the sites. The contractor will return after 7-10 days to remove the dead vegetation and apply further weedkiller, if required. They will then repair any damage caused to the slurry surfacing.