London Power Tunnels -Leak Sealing London Power Tunnels is a major construction project currently being carried out on behalf of the National Grid. Churchill have been employed by Costain to undertake the design and installation of a bespoke access and leak sealing solution There are twelve number individual access shafts measuring approx. 13 metres in diameter and some 40 metres deep, providing access into the tunnel network. The shaft is made up of interlocking concrete ring sections. During a heavy period of sustained rain the rings were seen to be leaking groundwater at various locations around the circumference of the shaft. The rings required injection polyurethane leak sealing. Prior to Churchill’s involvement the client considered installing a fully independent sca?old access syste

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