This week in 1939: protective works on underground railways

Britain declared war on Germany in September 1939 and by December around 50 underground stations had been identified as being more at risk from flooding following air raids.

Flooding had already identified as a serious risk in 1938 and work had begun to rectify the situation but the outbreak of hostilities brought forward a temporary solution that saw floodgates closing in one minute or 4.5 minutes if closed by hand.

The solution was designed Mr. W.T. Halcrow, Consulting Engineer and built by Glenfield and Kennedy.

The following excerpt from The Engineer explains exactly how it worked: ‘One problem of some magnitude is the protection of the underground railways from any possible risk of flooding, either from the Thames or from the sewers or water mains, where they are in close proximity to the stations.

‘One method of protection adopted is the installation of floodgates at certain of the stations, and when the works at present in hand are completed, all the stations and sections of the line, at present closed, will be reopened and travel on the Underground will be as safe as hitherto.

‘Until these permanent works have been completed the complete safety of the public is ensured by temporary means.

‘In the accompanying illustration is shown one of the electrically operated operated floodgates which have been installed for the purpose of closing the tunnels in the event of an air raid.

‘These gates are designed to resist a pressure of 800 tons, and each is built up of steel with an overall thickness of 13in. and weighs just under six tons. They are set in a framework of cast iron against the headwall of the station platforms, alongside the tunnel mouth.

‘Under either electric or hand power the gates slide along the framework guides into position across the tunnel mouth. Electrical operation is controlled by push button and alten1ative supplies of power a re available.

‘Within three minutes of receiving orders to close, the gates can be run into the shut position and sealed.

’The actual closing of the gate across the tunnel mouth by power operation takes one minute, and by hand in 4.5 minutes.

‘When an air raid warning is received at the Traffic Controller’s office, the Controller, by means of special electric push-button switches, immediately transmits an instruction to close the gates to the operators of the gates, who have been specially trained and are on duty continuously.

‘This rings an alarm bell at each of the gates and illuminates the word ” close” on indicator panels in the operators’ control cabins. The operators acknowledge receipt of the instruction to ” close” by themselves pushing button switches in their cabins, which cause a sign to be illuminated in the Traffic Controller’s office.

‘In the operators’ control cabins at the ends of the platforms adjacent to the gates there are illuminated diagrams of the section of railway line between the gates, which indicate to the operators the presence of a train in the under-river section.

‘As soon as the operators have satisfied themselves by means of the diagrams that all the trains have cleared the sections of line between the gates -the maximum time for a train to clear would be 2 minutes -  the closing of the gates can be proceeded with.

‘In order to prevent the possibility of a gate being closed while there is still a train in the under-river sections of tunnel, interlocking devices are provided which would prevent the gates being closed in such circumstances. The next stop is to fill in the gaps in the gate sill which provide space for the rails, so that a continuous runway is provided across the tunnel mouth over which the floodgates can slide into position.’