Talk:Severn Tunnel

message: Please state whether these are US or Imperial gallons, and also express in litres or cubic litres. Not doing so is to assume that only Brits read Wikipedia and is lazy editing. 5.67.59.110 (talk) 06:30, 14 August 2014 (UTC)
thread_title: Water volumes

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thread_title:  External links modified (January 2018) 

message: The claim "a tunnel to shorten journey times" seems to be getting expanded here. However that's not the reason for the tunnel: the tunnel was built specifically for naval steam coal traffic, in time of war. Any advantage for passengers was secondary to this.  The Royal Navy wanted to improve its supply lines from the vast reserves of coal in Wales (much already mined and in wagons) to the demand of Portsmouth and Plymouth. Before the tunnel this had to go via Gloucester and (more limitingly) the Chepstow bridge. Andy Dingley (talk) 16:07, 14 September 2018 (UTC)
replies: text: @Andy Dingley Eminently credible; is there a citation for this so we can include something along these lines in the article? Yadsalohcin (talk) 22:45, 11 June 2021 (UTC)
thread_title:  Reasons for a tunnel 

message: The mention of the "ferry between Portskewett, Monmouthshire and Lew Passage, Gloucestershire" -while an accurate reproduction of the ref cited at engineering-timelines.com must surely be a propagation of a misprint in that ref, as I can find no other mention of 'Lew Passage' on the web, while it is known that the ferry ran via 'New Passage'. At what level of certainty can we override in the article text an apparent misprint in a ref? Yadsalohcin (talk) 22:45, 11 June 2021 (UTC)
replies: text: By using a ref that is regarded as more reliable? See for instance MacDermot (1931) p. 4 Bristol & South Wales Union Railway was opened from Bristol to New Passage with a ferry across the Severn Estuary to Portskewett; p. 5 He [Brunel] decided that the best place [for the ferry] would be at what is known as the New Passage. (itself quoted from ) and finally p. 362 passenger trains began to run between Bristol and Cardiff on the 1st December, whereupon the ferry service between New Passage and Portskewett Piers ceased. --Redrose64 🌹 (talk) 10:33, 12 June 2021 (UTC)
thread_title: Lew (sic) Passage, Gloucestershire

message: I'm wondering about that claim of the tunnel being of danger of "[being] full of water" within 26 minutes if the pumps fail completely. At a very rough guess based on https://www.railwaywondersoftheworld.com/severn-tunnel.html, the tunnel might have a cross-sectional area of roughly 40ish m². Times 7 km length gives a total volume on the order of 280,000 m³. At the same time, the average volume of water being pumped out per day is being given as 50,000 m³, which would mean that completely filling up the tunnel would take several days.
Even if we just want to completely fill the bottom of the tunnel, given a tunnel height above rail level of roughly 6 m and gradients of 1 in 100 to 1 in 90 and ignoring the short level section at the bottom of the tunnel, it would mean effectively filling half the tunnel volume for about 600 – 700 m in each direction. That'd very roughly be around 30,000 m³, which with a somewhat above-average discharge of 60,000 m³ would still take half a day to fill up instead of half an hour. While the discharge of the spring can certainly vary and my estimate for the tunnel's cross-section is relatively rough, I think a factor of 24 seems a bit too much on the high side, which leaves me wondering where that figure of 26 minutes comes from and what it was actually supposed to represent.
Maybe the most reasonable interpretation would be that after 26 minutes the low point of the tunnel becomes sufficiently flooded that it would be unsafe to continue running trains? JanTH (talk) 21:38, 15 October 2022 (UTC)
thread_title:  Flooding danger