Our Ref:          FOI-1045-1819

Thank you for your request received on 14 July 2018 asking for information about subsidence on Chilworth Street.
 
Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy. I can confirm we do hold the information you require. You asked:
 
I would like to see documentation where subsidence has been identified on Chilworth Street and the immediate surrounding area, and comments upon the likely cause of subsidence since the Crossrail works began.
 
Please see the attached sketch plan which shows the 1mm (blue) and 10mm (red) predicted ground settlement contours in the vicinity of the Paddington Box including Chilworth Street. Generally the ground settlement impact assessments (calculated in accordance with the method described in Crossrail’s published Information Paper D12,) for buildings surrounding the Paddington Box, predicted little effect from the station construction works (typically Category 0-negligible). We have also attached a report summarising actual ground settlement measured in the vicinity during Crossrail works, to correlate against predictions.
 
The reports show plots of vertical settlement, derived from satellite distance readings for discrete reflectors (the dots on stable reflective structural building features).
 
Please note:
 
• Representative areas (patches) have been selected to produce averaged time history plots along Chilworth Street and which are also fairly representative of the area generally
• Superimposed are the 1mm and 10mm predicted contour lines
• The time histories are plotted both with and without background settlement estimated effects, to give the best practical estimation of the Crossrail’s net effect
• By inspection it can be seen there is good congruency between the predicted and actual measured settlements. The actuals are notably less than predicted
 
Please also note that the use of the term subsidence in the context of Crossrail is incorrect as there is a controlled and managed ground settlement. Subsidence is the consequence of uncontrolled, large ground movement caused by such things as earthquakes, tree roots, failed foundations etc.
 
If this is not the information you are looking for, or if you are unable to access it for some reason, 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]

Attachments