FOI request detail


Request ID: FOI-4493-1718
Date published: 28 February 2018

You asked

Follow-on from FOI-2983-1718: To assist you with the search the requested information may be contained in a surface ground water design manual or guideline. The question is not really specific to each underpass and tunnel, but more in general what about the design rainfall return period that the surface water drains are designed for, for example a 1:10 year rain event, in order that the road surface does not get inundated with the surface water run-off.

We answered

Our Ref:          FOI-4493-1718

Thank you for your revised request received on 11 February 2018 asking for information about underpasses on the TfL Road Network (TLRN).

Your request has been considered in accordance with the requirements of the Freedom of Information Act and our information access policy.

We do not hold a specific document containing the requested information. As previously stated, to go through each underpasses maintenance manual and or drawings (if they exist) to glean this information would exceed the appropriate limit. The drainage for these structures would have been designed in accordance with the relevant standards within the Design Manual for Roads and Bridges (DMRB) or any previous standards at the time i.e. ‘national guidance’. The design rainfall return period would have been updated and revised over the years, so different return periods are likely to pertain to different structures but would have also followed the relevant standards/guidance at the time.

Please note in regard to our previous response to question two. Our response incorrectly stated that there are 12 tunnel structures maintained by TfL. We have 10 tunnels only that we maintain. We do not maintain Limehouse Link and East India Dock tunnels – these are maintained under the A13 DBFO concession. We do however operate all 12 tunnels, albeit in collaboration with the A13 concessionaire for Limehouse Link and East India Dock tunnels. I apologise for this error.

If this is not the information you are looking for please feel free to contact me.

Please see the attached information sheet for details of your right to appeal.

Yours sincerely

Gemma Jacob
FOI Case Officer
FOI Case Management Team
General Counsel
Transport for London
[email protected]

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