As mentioned in the linked presentation, they envision using interconnected 300m (1000ft) long segments that can be changed using ROVs, using technology that's

As mentioned in the linked presentation, they envision using interconnected 300m (1000ft) long segments that can be changed using ROVs, using technology that's already available for underwater pipelines. Also mentioned is that the LHC cryostats, some nice illustrations here[1], are very nearly neutrally buoyant. Given these would be built similarly, they wouldn't need significant infrastructure to keep them in place. So no humans would need to go down there, if something breaks they could just replace the broken segment(s) and fix the broken one(s) on the surface. [1]: https://cas.web.cern.ch/sites/default/files/lectures/bilbao-2011/bailey.pdf https://cas.web.cern.ch/sites/default/files/lectures/bilbao-...