TfL Ref: FOI-0081-1718
Thank you for your clarification received by Transport for London (TfL) on 11 April 2017 asking for information about the DLR
Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy. I can confirm we hold some of the information you require. You asked:
It is our understanding that you have now provided formal approval the developers plans to construct a large building on the site of which beneath the train shallow tunnels run.
DLR has not.
There has been a suggestion that the site is now not going to be piled and means that the weight of the building will be carried by the DLR tunnels. If true, we would like you to explain what analysis has been done to persuade you that the tunnels are capable of carrying this load? And why would you put at risk a public facility in this way?
This has not been decided. DLR does not intend to place its infrastructure, staff or customers at risk.
What is the lowest depth that the subsoil of the foot tunnels is owned by DLR?
DLR does not own any foot tunnels.
How deep are each the passenger tunnels at the lowest point from the top soil?
Approximately 15m
How far will you allow the developers to bore holes given that the Calders Wharf site subsoil is predominately above tunnels with hardly any space to construct columns?
A borehole was previously undertaken with no objection. No further boreholes are proposed at present. The detailed design has not as yet been produced including piling.
What weight are the passenger tunnels designed to withstand?
The tunnels are designed to withstand the worst soil and hydrological conditions on the lowest point of the alignment plus 50kN/m2 imposed at ground level over the footprint of the development.
Are you aware that any such ground movement / pressure surrounding the tunnels would result in the tunnels to "pop". Please can we see the copies of your reports as they affect public safety on a huge magnitude?
As stated above, the detailed design has not been undertaken or therefore not provided yet in order to be reviewed.
Subsequently, please also reconfirm that you are happy for the developer to bore of holes around foot tunnels during train operational hours?
As stated above the DLR does not own any foot tunnels.
Who appointed the surveying company to carry out the assessment on the effect on the tunnels to confirm that boring holes above the tunnels is perfectly safe?
The developer has appointed professional advisors to assess the impact of the proposed development on the tunnels. When the detailed design is available DLR, its operational partners and appointed engineers will review and assess.
Have you checked that the developer does not have a conflict of interest / history of working with with this particular company/ies previously?
DLR cannot comment on the appointments made by the developer, but is satisfied that any advice DLR will receive will be unbiased.
Has this company got a proven history of surveying such a complex design over DLR tunnels?
Some of the advisors appointed have experience of sites around DLR. We believe they all have experience of and around tunnels.
Just by the very nature of the risk, did the DLR independently seek the professional opinion of more than one certified and chartered structural engineering company?
Yes we did
Did the advisors inspect the site / tunnels for unexploded devices which are common in this area? Regardless of the developer carrying out the works, DLR has a moral obligation to ensure passenger safety.
By unexploded devices, we think you are referring to unexploded ordnance most of which relates to World War II. DLR has procedures in place for ensuring its infrastructure is safe. The tunnels post date World War II significantly and we believe that unexploded ordnance surveys for the construction of the tunnels will have been undertaken prior to the construction of the tunnels. We do not require advisors to check the tunnels themselves for unexploded ordnance. The developer is and has been required to undertake unexploded ordnance surveys of its land.
If this is not the information you are looking for, or if you are unable to access it for some reason, please do not hesitate to contact me.
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Yours sincerely
Lee Hill
Senior FOI Case Officer
FOI Case Management Team
General Counsel
Transport for London
