how did we optimise, earlier?

We were commissioned by McConnell Dowell to support the project team with excavation designs for the three main tunnelling shafts. We produced final design solutions for the main launch shaft which used unreinforced secant piles with 50% less cement and 90% less reinforcement than conventional designs.

At the London Street retrieval shaft, careful logging of the rock face during excavation allowed the 6m high and 7m diameter cavern ‘belled’ cavity in the rock to be constructed completely unlined, resulting in a reduction of over 70% in the face support. Such design optimisations resulted in substantial time and cost savings for the contractor and a significant reduction in disturbance for stakeholders.

Our optimised solution was better for the client, the contractor, the community, and the environment. It was a win all around – with less cost, carbon, time, and less wastewater in the harbour. Who wouldn’t be happy?

St Mary’s Bay to Masefield Beach Water Quality Improvement




project team

Andy O Sullivan had a great understanding of the contractors focus to provide a safe and efficient solution for the shaft works on the Saint Marys Bay Project.  Their willingness to investigate change and be flexible during the construction phase allowed the project to realise opportunities and achieve a successful outcome

Grant McLean – Senior Site Executive, McConnell Dowell