Fugro Seacore Limited (FSCL) was subcontracted by Volker Stevin to assist in the installation of a replacement linkspan within Heysham Harbour. The project involved demolition of the existing linkspan’s foundations, deepening the sandstone seabed surrounding the new linkspan and inserting four pin piles into the seabed as part of the new linkspan’s support structure.
Removal of old foundations
Demolition of existing foundations required explosives to fragment the rock and concrete to enable dredging works to commence. Working from FSCL’s Skate 1 and C5 jack-up barges, over 130 no. 89 mm diameter holes were drilled at various depths into the seabed.
The holes were drilled in a square grid formation covering approximately 900 m². Spacings were critical - they had to be
2.5 m apart for the explosives to fragment the rock/concrete. To assist this and to speed up barge repositioning (hindered by the 8 m tidal range), an RTK positioning system was installed which displayed the barge position in real time on the drilling grid.
After the drilling phase, the holes charged with explosives. Blasting was carried out several times per day over a 2 week period and due to the proximity of nearby buildings, vibrations from each blast were monitored with seismographs to minimise risk of disturbance.