01.01.07
Leven viaduct
Network Rail were responsible for the design and construction of a £13m competitively tendered project with Carillion to reconstruct the superstructure on a 49 span viaduct. The viaduct is located on the Carnforth to Barrow-in-Furness railway line near Ulverston, in the south of the Lake District. The rail line is a strategic route for nuclear trains to Sellafield and an important long distance passenger and freight service route to Manchester and trans-Pennine.
The 49 span, 480 metre viaduct was originally constructed in 1848 and reconstructed in wrought iron in 1880. The viaduct was assessed as approaching the end of its serviceable life and a speed restriction was imposed. Route strategy analysis concluded that allowing the condition of the asset to deteriorate and the imposition of weight restrictions and a further reduction in speed would significantly affect the operating capacity of alternative rail routes and would increase road traffic.
The viaduct crosses Leven estuary which feeds into Morecambe Bay and is included within the limits of the site of special scientific interest, RAMSAR, special conservation area and protected bird areas. These environmental restrictions prevented any access to the viaduct from the estuary bed and effectively reduced the allowable working to the width of the viaduct.
Extensive planning and consultation with the train operating companies and local authorities allowed the railway to be closed for 16 weeks to enable the reconstruction of 48 decks with new steel units whilst span 37, the original shipping channel, was strengthened and refurbished to meet current design loading requirements. A further consideration was the relocation of three 11kV power cables which were located along the full length of the viaduct.
The logistics of the site and the constraints led to an innovative approach whereby the demolition and reconstruction made extensive use of mobile gantries which allowed the demolition and construction activities to run concurrently.
Site access for all major plant and equipment was located three miles away in each direction at Cark and Ulverston stations. The environmental and geographical considerations led to satellite worksites being established and managed.
A 125 strong workforce was employed for the 16 week long blockade which involved the fabrication and erection of 3500 tonnes of new steelwork and over 1km of new railway tracks. All works were successfully complete within the blockade, safely and within budget. The viaduct was handed back into operational service on time, despite delays at the start of the project due to adverse weather and mechanical failures.
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