Comparison Between Bored Tunnel and Immersed Tunnel Options Developed for the Silvertown Tunnel Beneath the River Thames

摘要

The need for a new road crossing at Silvertown is the result of three key drivers:- Severe congestion and delay at the Blackwall Tunnel and surrounding road network; A lack of network resilience and reliability resulting from a lack of alternative road crossings in east London and the impacts of unplanned closures; and The need to support substantial economic development in east and south-east London (jobs and homes)These drivers directly informed the main objectives for a road-based river-crossing solution.The traffic-related problems at Blackwall Tunnel are long-standing and before Transport for London (TfL) assumed control for the strategic road network in London in 2000 the Department for Transport (formerly Dept of Transport) had investigated various relief options including a third tunnel bore and new bridge. This resulted in a new crossing alignment being safeguarded (by direction of the Secretary of State for Transport) and this was refreshed in 2001 in favor of TfL. In recent years (since 2009) TfL as part of the East London River Crossings Programme has undertaken detailed optioneering and feasibility work to address the above 'need'. This led to the conclusion that a new road tunnel would offer the best solution in preference to bridge, ferry or demand management options. In 2012, in response to a formal request by the Mayor of London, the Secretary of State for Transport confirmed a new road crossing at Silvertown as a Nationally Significant Infrastructure Project (NSIP) by Section 35 direction under the Planning Act 2008. This NSIP designation meant that TfL as scheme promoter must comply with the National Rail and Road Networks National Policy Statement (NNNPS) and must seek the necessary powers to build and operate the crossing by means of a Development Consent Order (DCO) under the Planning Act 2008.