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Preparing the ground

ADVANCED WORKS

Clearing the way for the above ground route of the CTRL from the London Tunnels east portal at Ripple Lane to Thurrock has been a major construction project on its own.

In fact it has absorbed nearly a quarter of the £300M allocated to be spent on Section Two before start up of the main contracts.

For much of this section the CTRL will shadow the London Tilbury & Southend Railway, built in the 19th Century across the Essex marshes. Ford arrived in England in the early 20th Century and its motor works at Dagenham spread north from the dockside, completely enveloping the railway which then became an convenient eastwest corridor for utilities as well as trains.

Making space to squeeze the CTRL into this corridor has spawned an extensive series of advanced contracts to clear utilities and ancillary railway infrastructure out of the way from beside the tracks. These have involved demolition, shaft sinking, microtunnelling, large diameter pipejacking, 'stopple' diversions of live 605mm high pressure gas mains, high voltage overhead cable diversions, sewer and sludge main diversions and permanent way construction.

Most of this work is adjacent to a live railway and some tasks require possessions of up to 52 hours. All of it is on a brownfield site which includes unpleasant materials such as 'blue billy', an arsenic compound that is a residue from decades of battery manufacture at the site.

In addition, the road bridges crossing the railway joining the northern and southern halves of Ford's factory have also accumulated an extensive range of utilities for the plant: steam, condensate and gas mains; power and communications cables; and, more recently, fibre optic cables.

Because these bridges at Kent and Thames Avenue had to be raised and extended to make way for the CTRL it was decided to divert all services onto two new structures dedicated to utilities and then rebuild the road bridges. This choice of a robust and flexible solution to dealing with utilities crossing the route has turned out to be fully justified.

Ford is the property owner throughout the central factory area and very close co-operation with RLE has been a feature of all the advanced works. RLE recently reached an agreement with Ford on re-configuration of its freight sidings which have to be moved to make way for the CTRL.

Another new bridge was required for Choats Manor Way to make a new road access west of the Ford works, replacing the level crossing at Dagenham Dock Station. Ground in the area is typically very marshy. It is being strengthened using vibro compacted concrete piles beneath all the earthworks approaches to the Choats Manor Way rail bridge.

The piles are being installed by a Bauer rig which displaces the ground using a huge vibrator hung from a crawler. When the hollow stemmed vibrator reaches 6m depth, concrete is pumped down to the head and the vibrator withdrawn. A single reinforcement bar is pushed manually down the centre of each concrete column as it is completed and a 'biscuit' of concete is cast around the head to assist load transfer when the embankment material is placed.

In addition there was a natural obstruction to the CTRL - Gores Brook. Relocating this innocent looking stream has involved massive sheet piled cofferdams and some intricate rail possession works to insert a large culvert beneath the tracks of the existing live railway. That alone involved a total of 200 hours of railway possesion work and taking down and putting up the catenary five times.

Safety and high qualilty have been the top priorities and can be measured by the 0.75M hours worked since there was a lost time accident.

Advanced Works Contracts:

London East Portal and Ford Motor Works to Thurrock Contract 302 Ford Service Diversions £9.5M Completed by Alfred McAlpine/Amec Joint Venture Contract 303 Advanced Works Bridge Construction.Two Ford bridges and Choats Manor Way £18M Kier Construction Contract 304 Rail Diversons £8.0M Completed by West Anglia Route Modernisation Contract 305 Advanced Pile Testing £1.0M Amec Piling Contract 360 National Grid Diversions £8.5M Completed for Union Railways (North) by National Grid company Contract 361 Advanced Works Utilities Diversion between Ripple Lane and Purfleet Bypass £20M J Murphy & Sons Contract 365 Ripple Lane Undertrack Crossing £1.5M Completed by Amec Civil Engineering

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