It's complicated

When will the LHC go back on-line?

http://cdsweb.cern.ch/journal/article?issue=35/2009&name=CERNBulletin&category=News%20Articles&number=1&ln=en

Due to the huge amount of inter-dependency between different areas of work in the LHC, even a small change can necessitate a complete overhaul of the schedule. For example, something as simple as cleaning a water cooling tower - required regularly by Swiss law to prevent Legionella - has a huge impact on the planning: "When you clean the water tanks it means we don’t have water-cooling for the compressors, that means we can’t run the cryogenics, so the temperature starts to go up," explains Myers. "If a sector gets above 100 K, then the expansion effects of heating can cause problems, and we could have to replace parts."