Client: Brett
Contractor: MMC Diving Services
Duration: 6 weeks
Date posted: 11-03-2022
Chalk Lake is a disused quarry in Kent, it is owned and operated by Brett Aggregates, it is linked to a privately owned quarry next door called Buckland's South. They are joined via a large cliff with two underwater tunnels passing through. These tunnels were originally used to transport materials by trains. Over the years they have filled with fresh water and become lakes.
Brett Aggregates needed to drain the quarry so it could be backfilled & the land reclaimed using materials excavated and removed from the London's HS2 project. Due to the x2 old train tunnels linking the lakes, back filling could potentially cause cross contamination. This would also drain the privately owned Buckland's South private quarry currently used for fishing and scuba diving.
Brett aggregates appointed MMC divers to come up with a solution, and after x7 years of planning and return visits, in April 2021 the project started!
X2 train tunnels underwater linking x2 lakes or disused quarries resulting in the need for them to be plugged. Working closely with Pro-serve and SLR consultancy, a series of heavy anchors were installed with cranes, lowered to the bed, then our divers used lift bags to float them into the tunnel and resin bolt or weld them into position.
Diver excavation was undertaken using the FDS diver dredging system to enable a clear bed for the bag and plug placement. Debris was removed clearing the tunnel and underwater cutting and burning was required to remove the old train tracks.
Layer by layer, bags were positioned and filled with concrete on both sides of the tunnels. Large key sheer pins were drilled and resined into the tunnel walls and floor between the new bag walls. Finally, a large concrete pour was undertaken between the bags to create a plug. 450 cubes of concrete or 1,090 tonnes of concrete was used to complete this project.
