GEO-Instruments teamed up with Balfour Beatty on a monitoring scheme for operations taking place at Avonmouth docks as part of the Hinkley Point C project.

GEO-Instruments HLC Hinkley Dock Edge Engineer
An engineer making final checks to the HLC system near to one of the waiting outfall heads.

The project

Tier 1 Contractor Balfour Beatty has built six concrete structures; four 5000 tonne intake heads and two outfall heads at Avonmouth that will be connected to five miles of underwater tunnels to supply cooling-water to the new power station.

In order to transport the structures offshore, along the Bristol Channel to their final position on the seabed, they first had to be loaded onto barges from the docks at Avonmouth, then need to be lowered into place via a complex and precise lifting operation.

The challenge

The loading out process from the dock to the barges was a slow and careful operation. The intake heads were gradually transferred from the dock edge via ramps onto the barges. A Hydrostatic Levelling Cell (HLC) system was installed to observe the effect the operation had on the dock edge. Acting principally as a means of Design Verification Monitoring, the HLCs monitored for slight changes in vertical movement of the dock.

The heavy-duty nature of the works meant significant risk of damage to the system, therefore measures had to be taken to protect the cells and tubing during the loading out works. Metal coverings and sandbags were used across most of the circuit and sensor positions were chosen carefully.

The solution

GEO-Instruments installed a total of 10 HLCs, with one positioned away from the works area to function as a stable reference. HLCs detect settlement or heave by measuring changes in pressure in a continuous fluid circuit and comparing those to the Reference cell. HLC systems are capable of sub-millimetre accuracy at high frequencies with data automatically collected 24 hours-a-day.

Effective collaboration with Balfour Beatty allowed the installation and monitoring of the operations to run as smoothly as possible and led to successful delivery of the project.

GEO-Instruments HLC Hinkley Dock Edge Loading out
One of the four intake heads ready to be loaded onto a barge
GEO-Instruments HLC Hinkley Dock Edge Design
A sketch showing the design of the monitoring system along the dock edge

Project facts


Hinkley Point C

Keller business unit(s)


Main contractor(s)

Balfour Beatty