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A1 Improvement schemes. Newcastle Western By-pass

The Newcastle Western By-pass was listed in the Department of Transports Policy for Roads, England 1980 to link the A69 to the A1(M) to the south. An extension of the by-pass to the north was proposed by the County Council.

One of the much later improvements of the A1, it came after the demise of the Road Construction Units and in a time when government policy brought about the transfer of work from counties to consulting engineers. This scheme was awarded to Bullen and Partners.

When they took over in 1981 the scheme had been in preparation for about four years although the route was first suggested in 1936 and a corridor was reserved in the development plan for the area in 1945. Residential development then took place on either side of the corridor; it was a good example of a far sighted planning judgement long before the days of sophisticated traffic forecasting and cost benefit analysis. After public consultations, a preferred route had been announced in 1981 which linked the Great North Road near Gosforth to Scotswood Bridge across the Tyne. Soon after work started on the scheme, some improvements were made to the design would be worthwhile. In particular, Scotswood Bridge was not in very good condition and the approach roads on the south bank, connecting to the Gateshead Western By-pass were tortuous, substandard for the expected traffic flows. A re-alignment was proposed with a new bridge crossing of the Tyne and a new length of road to the south, providing a much better connection near Gateshead. In due course, after much analysis and scrutiny, the Department accepted this proposal and thus was Blaydon Bridge conceived.

Newcastle Western By-passThe 11km by-pass joins the present trunk roads north and south of Newcastle and Gateshead connecting with the key radial routes from the West such as the A69 and A696. The scheme relieving the existing Tyne Bridge, removed traffic from the town improving the environment, and assisted in the planned urban regeneration.

The alignment follows the western edge of the Newcastle / Gateshead conurbation, from the former A69 River Derwent bridge to the A1 north to Gosforth. Blaydon Bridge was the latest addition to a collection of notable Tyne bridges for which Newcastle is justly famous, and there are seven grade separated interchanges to give access to the existing road network.

The by-pass was designed to carry 50,000 vehicles per day and is dual two lane, with a third lane on each carriageway between interchanges from Scotswood Road to Ponteland Road. All the interchanges are two level and access is via slip roads.

Permanent road signs on gantries and at the side of the road show primary destinations for drivers. Lighting has been provided along the entire length of the by-pass.

It was predicted that the reduction of traffic on adjacent roads would prevent at least two fatalities and thirty serious injuries every year. Ten footbridges and subways separate pedestrians from the traffic on the by-pass and its side roads.

Before construction started, 1200 homes were provided with noise insulation. Earth bunds and concrete screening walls were constructed to reduce traffic noise and there has been extensive planting of trees and shrubs. Although the corridor had been protected for the scheme, designing the road to modern standards required the demolition of 66 houses.

On a historic note, where the route crosses the remains of Hadrians Wall, in conjunction with English Heritage, stone sets and a plaque were provided to mark the line of the wall.

The importance of nature conservation is also reflected in the scheme. At Derwentaugh the embankment has been founded on a 2 m layer of inert rock to prevent contamination of the adjacent Shibdon Pond Nature Reserve.

Diversion of major services were carried out in advance of the main construction contracts at a cost of £12 million.

The total cost of the scheme was some £88 million of which £23 million was provided by the European Community's Regional Development Fund.

Because the project was so large and diverse the construction of the by-pass was divided into four contracts, Contracts 1 and 3 being awarded to Balfour Beatty Construction Ltd, Contract 2 was awarded to Edmund Nutall Ltd and Contract 4 went to Birse Construction Ltd.

Contract 4 was commenced by Birse in Feb 1987 as an advanced works contract in order to prepare a 1km long section of the Contract 3 route at Derwenthaugh, where 8m high embankments were to be constructed over deep deposits of soft alluvial silts and clays. The purpose of the advanced earthworks was to squeeze the ground by surcharging and accelerate its settlement by drainage of water from the clay through vertical sand drains. During embankment construction, 24,000 vertical sand drains with a total length of 210km were installed on a grid layout with instrumentation for monitoring ground behaviour. Until the ground was sufficiently stabilised, the road could not properly be built and it was predicted that the process would take at least six months. On 24th April 1987, the advance works commenced and the project was formally inaugurated by John Moore, who was Secretary of State for Transport at that time.

Contract 1 - Etal Lane to North Brunton started in August 1987. It comprises 5.6km of dual two lane road interchanges at North Brunton, Kingston Park and the A696 Ponteland Road. It was opened to traffic three months early on 1st March 1990 by Robert Atkins, MP, then the Minister for Roads and Traffic.

Newcastle Western By-pass2Contract 1A - Fawdon Railway Bridge. A scheme was proposed which took the road over one of the busy Newcastle Metro railway lines at Fawdon. This was much cheaper than putting the road underneath but required a length of embankment through a sensitive suburb. At the public enquiry local residents and their councillors objected to this intrusion and in his report, the Inspector recommended that despite the increased cost, the underpass arrangement should be preferred, and so it was. Cementation were awarded the contract for its construction.

The main problem with inserting a bridge in a railway line is keeping the trains running without interruption. This usually means that the new bridge has to be rolled into position sideways and the line quickly reconnected during a short period when there are no trains. British Rail had employed them on several occasions, in particular during the construction of the M56 and the Weaver Viaduct. In those days, the customary method involved supporting the rail tracks on steel beams across trenches or pits protected by sheet piling, in which the bridge foundations could be built below. The new deck would be built alongside on temporary tracks and rolled sideways, often on steel balls. During the 70's a new technique had developed, based on a system of thrust boring started by Jim Thompson and his firm, Tube Headings, who were ultimately merged with Cementation Projects Ltd. Originally intended for jacking concrete pipes and subways, the system was developed and extended to railway bridge construction. Large square or rectangular concrete boxes, with steel cutting edges were constructed in pits below the railway line and installed under the track by progressive jacking and excavation using tunnelling methods. Cementation had patented a simple but effective refinement, not hitherto spotted by their competitors. Friction was substantially reduced during the jacking process by progressively unrolling a reinforced rubber or plastic sheet, (for example, conveyor belting) between the top of the box and the soil. As a result, Cementation had successfully completed a number of bridges for British Rail and with their patented system, gained a near monopoly in this small but specialised market.

It was decided that the safest, surest and least expensive way of implementing the work would be for Cementation Projects to design and construct the bridge. The Department of Transport were vigorously opposed to the idea that a contract should be let without competition. It took a lot of verbal and written persuasion to secure the required result. Ultimately, it was agreed that Bullens would employ Cementation as sub-contractors for the design and would retain full responsibility. Cementation would be managing contractors, with a negotiated fee but would sub-contract the whole of the civil engineering work by competitive tendering. A contract was let on this basis in November 1987, the work proceeded well and the bridge was rolled in during March 1989, the programmed date, with no interruption to commuter services.

Contract 2 - Blaydon Bridge and Blaydon Haughs Viaduct commenced in November 1987. Blaydon Bridge is a five-span pre-stressed concrete structure, constructed using the balanced cantilever technique, with a main navigation span over the Tyne of 108m.

Newcastle Western By-pass3Several possible designs were prepared, evaluated and compared. Some were discarded on account of unsatisfactory appearance and the final choice for the river bridge was between a steel cable stayed bridge and a prestressed concrete box structure. The concrete alternative was thought to be slightly cheaper to build and was selected.

A similar comparison was made of designs for the approach viaduct and the final choice was a system of welded steel plate girders with a reinforced concrete deck. At the end of the day, choosing the design for a major bridge structure is a matter of engineering judgement, perhaps influenced by personal preferences. Although it is essential to estimate quantities of materials and costs, other factors, including appearance and ease of building, are equally important. Although the costs of the selected design when built are precisely known, the estimated cost of an unbuilt alternative concept remains theoretical and untested. Contractors are nowadays free to offer and alternative design at the tender stage and are frequently successful, as was the case for the Tweed bridge at Berwick.

When the job was put out to tender in August 1987 one firm offered a steel bridge but the purported price margin was slim, the appearance unsatisfactory and the projected costs of maintenance too high. So Edmund Nuttall Ltd. were awarded the contract and commenced work in November 1987, working exactly to the contract drawings. The inevitable unexpected happened during the excavation, in a cofferdam, for the southern main pier, whose foundation was planned to sit on sound sandstone rock below the river bed. In two corners, totalling about a quarter of the load bearing area, the rock was not good enough. It was broken up and mixed with sand and clay, probably the result of ancient glacial activity; It was decided that the pier foundation would be strengthened by piling. The preferred solution was a large number of mini-piles using small drilling rigs which could operate from the bottom of the hole, inside the cofferdam.

The consequences of the unforeseen change of design were considerable. There could be a delay of about six months, prejudicing the 1990 completion date, and costs would increase substantially. However, Edmund Nuttall Ltd were authorised to increase resources to recover lost time although this would incur further expense. The work proceeded satisfactorily, and the construction of the superstructure by cantilevering followed.

Newcastle Western By-pass4Blaydon Haughs Viaduct is a 17-span steel viaduct carrying the by-pass over A695 Chainbridge Road and the Newcastle-Carlisle railway line. It is 530m long and the deck incorporates 2,100 tonnes of structural steelwork, supported on 3,500 tonnes of steel H-piles.

Contract 3 - Derwenthaugh to Etal Lane commenced in June 1988. This is the largest contract on the by-pass, extending north and south of the River Tyne and 40% of its £25 million tender value was for structures. These included seven road bridges, eight footbridges, eight subways and over 3km of retaining walls. The wall of Scotswood slip road is 12m high and of ''reinforced earth'' construction using compacted pulverised fuel ash reinforced with polypropylene strips. There are interchanges north of the Tyne at Stamfordham Road, the A69 West Road and Scotswood Road and south at the Tyne and Derwenthaugh Road.

Newcastle Western By-pass5Coal mining is an important feature of Tyneside's history and extensive old mine workings have been encountered along the by-pass route.

Shallow seams were excavated and filled with compacted soil and deeper workings drilled and injected with cement and pulverised fuel ash grout. Old mineshafts were filled and capped with reinforced concrete.

On 1st December 1990, Her Majesty the Queen, on her way to launch a ship at Wallsend, formally opened the Newcastle Western By-pass and unveiled a plaque, midspan over the River Tyne, at the boundary of Newcastle and Gateshead, to christen Blaydon Bridge.