Northern Ireland's Roads Service has ordered a review of the contract let to build a new underpass, as it was submerged under 7m of water just weeks after it opened to traffic.
Severe floods swamped parts of Northern Ireland over the weekend, but the flooding of the Westlink has prompted the Regional Development Minister Conor Murphy to order an investigation.
Contractors for Belfast's Westlink, Highway Management Construction (HMC), have defended the design of the £104M scheme. Deputy project Martin O’Neill was adamant that the flooding was "not a design issue".
The flooding occurred when the Clowney Water overflowed, overwhelming the new culvert for the underpass.
"Over 70mm of rain in 12 hours in Belfast over the weekend and the Clowney was recorded running up to 600mm higher than it has ever been recorded; we designed the redirected culvert to withstand a 1:100 flooding event but you can’t legislate for 20M gallons [90.2M litres] of water in the space of a few hours," said O’Neill.
The review will examine, "the design, operation and management aspects of the Clowney Water system with the DBFO Co who are responsible for the design and construction of the M1/Westlink Scheme.
"This review will examine the short and longer term arrangements associated with the rivers which resulted in the flooding in this area," said a Department of Regional Development spokesman.