Forth Estuary Transport Authority (FETA)

Contract detail:
Northbound Carriageway (completed Oct 2007)
Value: £4.00m
Duration: 18 weekends in two work phases
Southbound Carriageway (completed Oct 2004)
Value: £3.24m
Duration: 18 weekends in two work phases

FETA's Project Brief was to avoid carriageway occupation during weekdays and the peak holiday period. To maintain flows of weekday traffic the Works had to be completed in two phases during a series of weekend carriageway possessions.
Possessions were not permitted during the peak holiday period and therefore Phase 1 was completed between April and June with Phase 2 completed during September and October. The Contract required the removal of the bridge deck's surfacing and waterproofing. Any identified remedial works were then undertaken to the steel and concrete decks prior to the application of new spray applied waterproofing membrane and hand laid mastic asphalt surfacing impregnated with pre-coated chippings.

The Works were awarded based on Tarmac's extensive previous experience

Tarmac has a long history of undertaking surfacing works on the Forth Road Bridge, including application trials of a variety of materials such as epoxy asphalt, SMA and mastic asphalt. This previous experience, coupled with a continuity of staff and supply chain partners, has brought continual improvement in all operational aspects and gave FETA the knowledge that the works would be completed on time and to budget.

Each weekend we programmed the Works in set 56 hour working windows. Works were undertaken in full contraflow with all traffic diverted onto the opposite carriageway. Possession times were 20.00hrs Friday until 06.00hrs on Monday and Tarmac were never penalised for late removal of the traffic management.

Experienced employees, including valuable input from our supply chain partners, promoted efficient working outputs during each weekend possession. Any obstacles that we had previously overcome were recognised and programmed into the Works. This ensured a quick progression straight from the onset and avoided any 'learning curves'.

A fine tuned method of weekend working was successfully implemented

By adopting a repetitious method of working each weekend, we were able to improve methods of working and increase outputs. The existing mastic asphalt surfacing was removed by cold milling. Residual mastic and, where required, the existing waterproofing membrane was removed using an innovative system of high pressure water jetting. Following inspection of the exposed area, any necessary concrete repairs (to the side spans) and weld repairs (to the steel main span) were completed. Eliminator HM waterproofing membrane was then spray or hand applied as necessary.

Mastic asphalt was delivered to the site in mixers, discharged and transferred to the point of laying. The material was hand floated to a thickness of 36 mm within 3 no longitudinal bays. Before the finished layer of asphalt cooled, the surface was dressed with pre-coated chippings.

2,500 tonnes of mastic asphalt was mixed and produced off site less than 6 miles away

Permanite manufactured the mastic asphalt base material in Matlock, Derbyshire. All aggregates used in the final mix, together with all pre-coated chippings, were sourced from Tarmac's Cruicks Quarry in Inverkeithing, Fife.

Prior to each weekend possession, base material, in molten form, was transported from Matlock to Tarmac's Hillwood Quarry at Ratho, Edinburgh, located less than 6 miles from the Bridge.

Five hours prior to actual laying, the molten mastic asphalt was mixed with clean, dried and warmed Dolerite aggregate, supplied by Tarmac. At the required time, the mixed and weighed material was transported from Hillwood Quarry to the Bridge. For testing purposes a sample of mixed material was taken from each batch and sent by Tarmac for analysis. Test results were presented to FETA on a weekly basis.

An experienced supply chain ensured both contracts were problem free

We were able to appoint and manage the same team of experienced supply chain partners for both contracts and appreciate that great benefit was derived from the expertise they were able to contribute. New County Road Planing
Alex Ferguson Recovery
C & V Carmichael Ltd
Concrete Repairs Ltd
JB Concrete Protection Ltd
Briggs Roofing & Cladding
Permanite Asphalt Markon Limited

"They (the Contractor) worked like Trojans. This was a complex project which included weld repairs to the bridge's steel deck, concrete repairs, waterproofing, then hand-laying more than 1,000 tonnes of mastic"
Alastair Andrew General Manager - FETA

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Forth Bridge Road (pdf, 390kb)

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