Diageo, Mallusk

DAWSON-WAM (DW) was contracted by Graham Construction in 2024 to design and install a permanent contiguous pile wall for Diageo, located in Mallusk, Northern Ireland.
The retaining wall was installed to create a lower-level traffic area and lorry parking bay. In the permanent condition, the wall is designed to act as a free cantilever, retaining the adjacent ground while accommodating the required level difference.

The project comprised the installation of approximately 180 linear metres of retaining wall, formed using 630mm diameter piles. The wall is designed to provide permanent retention of up to 2.8m of ground.

One of the key challenge on the project was the proximity of the wall to two existing large sprinkler tanks. Due to this constraint, the wall was required to be designed to limit lateral deflection to a maximum of 10mm. This stringent requirement was successfully achieved during construction, ensuring the protection and stability of the adjacent structure. To minimise the risk to the adjacent structure, our Cased CFA piling technique – being virtually vibration-free – was particularly beneficial in reducing the vibration-related impacts.
Another challenge for both the piling design and site operations was the significant variation in rock levels across the site.

The underlying basalt was a strong formation, which our Cased CFA technique was able to successfully core into. However, the top of rock was encountered at depths ranging from 1.6m to 10.1m below ground level, requiring careful adaptation of both the design and construction methodology to suit the varying conditions.