Research and analysis

HS2 review of the proposed tunnel extension through the Colne Valley

This page details a HS2 review of a report prepared for the London Borough of Hillingdon about extending the Northolt Tunnel.



The London Borough of Hillingdon (LBH) commissioned Peter Brett & Associates (PBA) to investigate the extension of the proposed HS2 (High Speed Two) Northolt tunnel to provide an extended tunnel passing under the Colne Valley. The tunnel extension would remove the need for a viaduct across the Colne Valley and its associated environmental impacts.

This report by HS2 provides a detailed review of the LBH proposed tunnel extension, including consideration of the engineering requirements, practicality, cost and programme implications and environmental impacts that would need to be considered.

Published 9 March 2015