The secret tunnel system of the Foundation of Honour as mentioned in the Adam Cranford series of books need to be diverted. The Foundation has discovered the plans of the National Grid will run extremely closely to one of the Foundation's main tunnels and subterranean rail system hidden under London in the UK. The Cross Rail project comes close to one of the Foundation's tunnels, but no work will be necessary to avoid conflict.
These tunnels were mentioned in the book Company Mole but do not appear on the official records and plans It is likely that the National Grid and the Foundation tunnels will not actually intersect, but the Council of Elders have chosen to divert the existing system.
Work has already commenced to resolve this problem. I'll probably include a mention of this work in the next Adam Cranford book which is work in progress. There will be no interruption of tunnel transport services and telecommunication services during the works.