REDESIGN OF a system of rollers used to launch a massive 10.5km subsea sewer across Dublin Bay is under way after the first section of pipe jammed during the maiden launch.
Launching has been halted while a new arrangement of rollers is finalised by contracting consortium Alfred McAlpine, Pierse and Tideway.
The 1.4m diameter submarine sewage pipe will run from Sutton, north of the bay, to Ringsend, where sections are being fabricated and assembled for launch. The pipe will carry wastewater from Sutton to a new plant under construction at Ringsend.
The main pipeline will be pulled by barge starting from Ringsend, but three 300m sections required for the works at the other end were to be launched first and floated into position.
The first of these sections was being launched last week on a series of rollers spaced around 8m apart, with three rollers at each support. The rollers provided a three-point cradle, along the centreline and at around 30infinity to either side.
The pipe launch path is along a vertical and horizontal curve. It is understood that the rigidity of the steel pipe caused it to jam and derail, damaging a number of rollers.
A new arrangement, placing the rollers at the centreline and one either side at 90infinity, is to be installed so that rolling can restart next week.
The project is immensely complex, with the submarine pipe being launched in the path of Dublin Port's busy shipping lanes, while the curved configuration also poses technical challenges.
The £26M contract is due for completion in November.