Deep Well Dewatering - Mersey Gateway Bridge

Temporary dewatering of 3no x 40m diameter bridge pier cofferdams across the River Mersey for new bridge construction

Project Overview

A temporary dewatering system was required for three 40m diameter cofferdams as part of the construction of the Mersey Gateway Bridge. Dewatering was also required to allow construction of the bridge pier cofferdams crossing the Manchester Ship Canal.

Mersey Gateway Bridge Piers

Stuart Wells designed the dewatering system consisting of 6no x 32m deep pumping wells installed around the internal perimeter of each bridge pier cofferdam. Passive pressure relief wells were installed in the central section with an array of vibrating wire monitoring piezometers to monitor and record groundwater levels and pressures. Pumping tests during commissioning confirmed the effectiveness of the design.

Manchester Ship Canal Bridge Piers

Conceptual dewatering models were developed with subsequent undertaking of a pumping test to establish flow, connection with the canal itself and groundwater quality. Further to this an array of internal dewatering wells were located within the sheet pile cofferdam. Dewatering was achieved using a deep well pumping system with continual monitoring of discharge flow and water quality.

Solution

Site investigation data was used to design the dewatering system for the Mersey Bridge piers with pumping tests during the commissioning stage to confirm the effectiveness of the dewatering design. For the Manchester Ship Canal Bridge piers, dewatering was achieved using a deep well pumping system with continual monitoring of discharge flow and water quality.