WHITEBRIDGE UNDERPINNING AND SCOUR PROTECTION

WHITEBRIDGE UNDERPINNING AND SCOUR PROTECTION

Following large scale flooding across the east of Ireland, Wicklow County Council called in Norfolk Marine Ltd to carry out an underwater inspection of the road bridge at Whitebridge on the Avoca River.

The inspection was to establish if the flood waters had damaged the bridge as water level had risen to by over 4m at the site causing damage to local properties and reaching the underside of the bridge deck.

A full underwater survey was carried out from Norfolk Marine’s mobile dive spread and a report prepared for the County Councils Chef Engineer. The survey revealed that the West Pier supporting the bridge had been under scoured and nearly 50% of its footprint was unsupported. The East Pier and both abutments were found to be in good condition with no under scour present. Although the bridge structure showed no signs of stress follow up inspections showed the under scour of the west pier was getting worse.
 

Norfolk Marine was tasked with find a solution to underpin the west pier and stabilise the structure wile taking in to account the environmental concerns of the Eastern Regional Fisheries Board. Designs were submitted and a Licence granted for the propose scour protection works.

A fabric formwork mattress was fabricated and install along with a temporary support system to hold the fabric formwork in place during filling and curing of the concrete. The works were completed over two days window wile the rivers flow rate was low. The works were carried out with the minimum disturbance to the river bed and without the need to operate any plant in the river itself. Under the watchful eye of the client the concrete was pumped in to the formwork with no discernable discharge in to the water course and no effect on the fish happily swimming under and around the bridge.

Following completion of the works the County Council placed rock armour around the brige pier to reinstate the bed level.