alt Hacker NewsProbably never. The tunnels cost a lot to build but, once built run almost for free - they're powered by gravity and will keep running for close to a century before major maintained is needed.
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margalabargala • today at 3:45 AM
Close to a century?
There are Roman aqueducts in continuous operation for two millenia.
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Yeah that makes sense but if growth dictates another tunnel... And it takes another 60 years, your capital expense starts to look a lot like an operating expense. Not to mention one of the big stated purposes of this tunnel is actually to facilitate maintenance of the other tunnels. There is probably more operation cost hidden here than seems obvious.