Thames River Crossing – Caversham Lock

The Reading Hydro community project is a Community Benefit Society, set up to raise funds from shareholders to build a twin Archimedes Screw hydroelectric turbines by Caversham Weir, to take advantage of the power of the River Thames. When operational, the power from the turbines will supply customers and the profits from the sale os the power will be invested back to the shareholders and into a number of community projects in the area. The turbines will produce 320 Mw/h per year. 

Gmac Utilities Ltd were contracted to drill a 140m shot and pull a 125mm SDR11 duct into place, under the River Thames from Kings Meadow to View Island, where the turbine house for the project is located. This is to bring the power from the turbines, to the Thames Lido building.

The client was able to establish from records that the piles alongside the lock, which was to be drilled under, were approximately 6m deep. Based on this the first shot by the Gmac team at approximately 13m below the lock failed as the drilling rig encountered a pile at that depth.

After further planning with a Slimdrill steering engineer, it was determined to move the rig back 20m and have a second attempt, this time at 17m. Using the profile designed by the engineer, the drill made it safely under the piles and across the 50m river, onto the island and right into the planned reception area. 

One of the biggest challenges for the crew was tracking the drill position as it crossed the 50m span of the River Thames. This is where the Digitrak Falcon F5+ proved its metal and capability. Despite the depth of the drill and the span of the river, the F5+ maintained contact with the drill head at all times during the crossing, meaning accuracy was maintained and the target reception area was struck.

The ground was a mostly clay but there was a difficult gravel section of a few meters depth each end of the shot, testing the Ditch Witch JT60’s ability. The gravel proved to be little problem for the seasoned Gmac team as their experience proved the ground was no match for good planning and skilled operators. 

With the pipe welded to length and ready to pull, the JT60 made light work of the task, pulling the pipe through within just a few hours with no problem from the gravel sections. 

Once through the team were able to tidy and backfill the site and pits and hand over to the client who manually, with a team of 56, pulled the cable through the duct and into position along their open cut trench.