Wastewater system gets helping hand at sea

Port Rodie, Stranraer

Project Overview

Location	Port Rodie, Stranraer
Sector	Water
Products	Groundworks Cofferdams

Stranraer is the second largest town in the rural landscape of Dumfries and Galloway and it sits on the bank of Loch Ryan, a sea loch humming with Scotland’s only natural oyster bed. The wastewater system for Stranraer and the surrounding areas was deemed outdated and in need of replacement.

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.

Modernising Stranraer’s Wastewater System

Stranraer, in Dumfries and Galloway, required a major upgrade to its outdated wastewater treatment works at Port Rodie. The existing facility discharged treated water into Loch Ryan, prompting the need for a new solution to transfer final effluent to the Irish Sea.

Harbour-Side Cofferdam Design

As part of Scottish Water’s project, we were appointed by George Leslie and MWH Constructors to design a bracing frame for a cofferdam constructed in the sea near the harbour wall.

Heavy-Duty Bracing Solution

Using our Supershaft Plus system, we delivered a twin-level bracing arrangement spanning 32m by 5.2m, supported by eight Super Bracing Struts, designed to withstand loads of 211kN/m.

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.

Learn more about our groundworks

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.

“ Mabey Hire’s Customer Product Specialist provided not only useful but invaluable design input to install the frame to what was a revised cofferdam. Very impressed and would recommend in future.”

Stevan Foster

Project Manager, ABCO Marine Ltd