Temporary tarmac repairs to granite cobbles approved at committee

Councillors today approved that tarmac can be used for temporary repairs to granite cobbles and pre-cast block roads.

The members of the operational delivery committee heard a further report will be brought to committee to outline the permanent repair options and associated costs.

A report to committee said tarmac is the best material for a temporary repair as it can be ‘unstuck’ from the cobbles (also known as setts locally) more easily than other materials such as concrete, for when the permanent repair is carried out.

Councillors also agreed lock block is replaced with the same or similar materials where it is feasible to do so.

Aberdeen City Council transport spokesman Councillor Ross Grant said: “We of course want to have permanent repairs to setts and lock block roads however we have limited resources and there are less numbers of people who can carry out this specialised work across the country.

“We are looking into training for some of our own staff for this specialist work and in the meantime, we have a statutory duty for repair of safety defects of our roads so a temporary repair using the best material is the most sensible option.

“While we appreciate tarmac repairs can look unsightly, it is better to have carried out a temporary repair using the material while waiting for the permanent repair, than not repair at all.”

The report said Aberdeen City Council, as a Roads Authority, has a statutory obligation under the Roads (Scotland) Act 1984 for the management and maintenance of its road network.

In the city, there are currently approximately 80 roads and large areas laid out in setts, as well as approximately 110 roads laid in precast block and many small areas featuring setts, such as at the edging of some roads.

The report said where a safety defect is minor, for instance where one or two setts or blocks have worked loose, it may be possible for the squad responding to the defect to reset the setts on initial visit with the area coned off.

The nature of the work required to make an ‘as was’ repair to a sett or lock block road will, however, often require traffic management or full road closure and the report said ACC’s Roads Service currently has a limited resource for carrying out some of these specialist repairs, some of which may have to be carried out by a specialist contractor. Training to upskill a group of operatives in this area is currently being investigated, potentially in collaboration with other Scottish Roads Authorities.

Following a repair, as per the Councils’ specification, up to four weeks may be required for the mortar mix used to secure the setts to set prior to any vehicular traffic being able to drive over the repaired area.

Given the statutory requirement to resolve any safety defects in a timescale that cannot be achieved where any form of traffic management or reconstruction is required, the Roads Service will in the first instance repair any safety defects using bituminous material, such as tarmac.

This bituminous material, in hot or cold form, is currently used to fill gaps where setts or blocks have been removed or where an area has suffered movement or become depressed, thus restoring a level surface and removing abrupt level changes that may cause a safety defect. Bituminous material may additionally be used to stabilise areas where its use will prevent further deterioration of the setted or precast block asset.

The Roads Service acknowledge that this style of repair may be perceived to be of poor aesthetic appearance. It is, however, the only practical method which allows it to fulfil its statutory requirement to maintain a safe road infrastructure. The Roads Service will continue to monitor the marketplace should any better solution become available.

By making temporary repairs in bituminous material, the Roads Service seeks to minimise the work required to complete a permanent repair at a later stage.

The report said tarmac can be broken up and removed in a manner that is easier and less labour intensive than other materials, such as cementitious material, and the inflexible nature of cement also makes it a poor choice of repair material in certain sett areas where the surface is designed to have an element of movement and will very quickly crack. The use of epoxy mortars would be of benefit, however they are extremely difficult to remove prior to carrying out a permanent repair, the report said.

Where traditional setts are removed to complete a temporary repair, these will be numbered, catalogued and retained in order that they may be reinstated at the time of a permanent repair being made.

The requirement for traffic orders, road closures, specialist materials and labour, along with the high associated cost of such repairs requires that permanent repairs will require to be added to programmed future works.

A further report will be brought to the Operational Delivery Committee to outline the permanent repair options and associated costs, and this report is currently scheduled for spring 2019.