The second Tyne vehicle tunnel was constructed by digging a trench across the river to hold submerged sections and to cover them with rock. The sections were constructed at the old Neptune Yard at Walker, from where they were floated down the river and submerged in the trench.
Conveniently the redundant dock at Tyne Dock on the South shore needed the dredged sediment to fill it

Specialist dredger Vesalius arrives on Eide Barge 33 -  4th November 2009

Vesalius working on the new Tyne Tunnel - November 2009
It dug out a trench in which the tunnel sections were sunk.

Huge semi-submersible ENTERPRISE taking Vesulius away on completion of its task

The octagonal tunnel sections were constructed in a reopened drydock at Wallsend (see Yards section)
With its ends sealed, the tunnel was floated down in two sections and then submerged in the trench dug by Vesalius.
The first section is seen here floating at Howdon.

Huge floating crane-barge Dina M working

Dredged sediment from the river bed was pumped to Tyne Dock, where it was used to fill the redundant dock.
The utility barge DN20 was used to secure the floating pipes against the tidal currents.