The consortium responsible for a £186 million scheme to improve Belfast’s Westlink motorway could have to carry out major repairs to the road if it is found that the drainage system cannot take the contractual design requirement of a “one-in-100-year” flood.
A report from the Northern Ireland Audit Office will today confirm that new detailed investigations are underway after the Broadway Underpass flooded in August last year following a deluge of rain. A consortium of Irish contractors Graham Construction and Northstone, and major civils firm Bilfinger Berger, were responsible for the work.
While the consortium has already footed some of the costs from the flood, including the clean up, repair costs and replacement of lighting, the report said: “If it is discovered that the drainage system cannot take a ‘one-in-100-year’ flood event, then the Northern Ireland Roads Service will require the consortium to undertake rectification work to provide for this.”
The NIAO also urged public sector organisations affected by the floods or road unavailability, including the emergency services, to investigate the potential to recoup costs from the consortium.
The report said an independent advisor had already conducted one investigation into the circumstances surrounding event, which found the flow of water entering the drainage system was less than its design capacity should have allowed for.
The NAO said: “However, this was based on theoretical calculations and it was recommended that a hydraulic model be commissioned.
“Roads Service told us that this recommendation, together with other recommendations in the report, have been implemented and that it will work in partnership with the Rivers Agency and the consortium to identify further measures to prevent reoccurrence.”
At one point during the floods, the road was under 6m of water.
But the consortium claimed a design fault at the Broadway Underpass was not to blame for the flooding and said to get almost one month’s rain in 12 hours was exceptional rainfall.
The M1/Westlink and M2 Improvement Scheme also included slip roads on the M2 at the Antrim Hospital, widening of the M2 from the Sandyknowles to Greencastle junctions and network maintenance over a 30-year period.
The report praised the department for procuring the work for £186 million after originally estimating the project would cost £250 million to complete.
Work began on the whole Westlink development in January 2006 and the final phase was completed in May this year, three months ahead of schedule.
The NIAO added: “This has delivered benefits to Roads Service both in terms of value for money and affordability.”
Financing for the project included sums from the European Investment Bank and the use of index-linked bonds – a first for Northern Ireland.