Web UI SpinnerHow Do They Do It?My List Outline IconAdd to My ListShare IOS IconShareS12:E20 - Power Tunnel and MoreDocumentary · 2015 · 22 min · 7 SeasonsTV-PGSubtitles IconMassive tunnels are built to prevent blackouts in a major city.EpisodesDetailsSeason 12Arrowhead Down IconSeason 4Season 6Season 9Season 10Season 11Season 12Season 13Play IconS12:E20 - Power Tunnel and More22 minTV-PGMassive tunnels are built to prevent blackouts in a major city.GenresDocumentarySubtitlesEnglishTV-PGThis program contains material that parents may find unsuitable for younger children.