The challenge
Situated at Port Rodie on the harbour front, the wastewater treatment works (WwTW) for Stranraer is a primary treatment facility with underground settlement tanks and no sludge treatment facilities (processes used to manage and dispose of sewage sludge produced during sewage treatment), which led to water being discharged into Loch Ryan. In one of the final operations of Scottish Water’s project, they were to construct a new pipe to transfer final effluent to the Irish Sea, removing completely the discharge to Loch Ryan.
We were contacted by sub contractors George Leslie and MWH Constructors to design a frame for the cofferdam, located in the sea close to the harbour wall. The frame was required to withstand a customer calculated loading of 211kN/m; this was achieved by using our Supershaft Plus bracing system. Twin level bracing was installed at 32m long by 5200m wide, along with eight Super Bracing Struts.
Our solution
Our Customer Product Specialist worked along with ABCO workforce to assist with the installation. Working day and night to tie in with the tidal flow. An 800 diameter pipe was bored from the harbour out under the railway and then into the cofferdam. The pipe was approx. 1m below the finished level in the cofferdam and it was then turned 45 degrees and out in to the loch.
The contract period experienced some bad weather conditions, causing crews to stand down when it was too dangerous to work. The project was successfully completed on time with the removal of the frames.
