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A1 Improvement schemes. Micklefield to Boroughbridge

Note: Many of the schemes described here have subsequently been by-passed by motorway upgrade schemes which are described elsewhere.

Micklefield By-pass

The contractor for the £418,000 Micklefield By-pass were Paviors Construction Co Ltd. Work on construction started in July 1959.

The 1.64 mile by-pass of dual carriageway has similar design features to the Brotherton scheme, including surfacings and involved some 300,000 cu. yds. of cut and fill earthworks.

Special features included the provision of a 6 ft. dia. "Armco" multi plate culvert at Sheep Dyke and the removal of a large quantity of unsuitable material and its replacement with imported boulder fill.

A new railway bridge to the east of Micklefield Station carries the by-pass over the railway. It comprises a composite deck of pre-cast post-tensioned beams and reinforced concrete abutments with cantilevered wing walls.

The by-pass was opened in Dec 1960.

Aberford By-pass

Aberford is an old market town retaining historic features back to the days of Imperial Rome. Samual Hicks, the famous Wesleyan Blacksmith of Micklefield, is buried there. The churchyard at Aberford is approached by a gate boasting a carved mouse running up one of the timbers. This is the trademark of a North Yorks carpenter and it is to be seen wherever he plied his trade.

Micklefield to BoroughbridgeThe by- pass was routed to the east of Aberford. Amongst other requirements was the retention of large stately beech trees in the vicinity of the Cock Beck. Unfortunately, a gale in the winter of 1961 uprooted them, much to the annoyance of the conservationists. Many trees suffered the same fate at Hook Moor further north blocking the A.1.

The contract for the Aberford By-pass was awarded to Dowsett Engineering and Construction Ltd. and commenced in October 1961 and was completed in 1963 at a cost of £741,000.

The Works comprised dual carriageways with a central reservation and grass verges. The verges were hardened with compacted Type 1 sub-base covered with 4in. of top soil.

The construction of the carriageways was experimental having two layers of cement bound granular sub-base (5% cement) laid by Blaw Knox / Barber Greene pavement finishers and compacted by vibratory rollers. An on-site batching plant was used for mixing. The surfacings were two course dense tar.

During excavation of the cutting north of Cock Beck which was composed of silts and gravels, a perched water table was released and moved "like a stream in spate" towards the Beck. The drainage in the cutting eventually dealing with the problem.

Aberford to Wetherby

The Great North Road between Aberford and Wetherby passes several historic sites including that of "the fierce battle of Bramham Moor fought in 1408 during the War of the Roses".

Clifford Mill was recorded in the Doomsday Survey and later developed as a centre of the flax industry. Boston Spa, as the name implies, is a former Georgian spa with the Pump Room and the 18th century houses enhancing the main street.

Bramham Park is the site of a magnificent classic style mansion built 1698 - 1710 by Queen Anne's Lord Chamberlain, Baron Bingley. It is superbly set in French style gardens. The park is the venue for the annual Bramham Horse Trials.

This section between Aberford By-pass and Wetherby By-pass involved dualling of the existing road for a greater part of its length and a new by-pass for the village of Bramham a length of 5¾ miles.

The grade separated junction with the Leeds-York Trunk Road A64, also required the construction of an additional mile of dual carriageway. Grade separation of all junctions was achieved throughout and acceleration and deceleration lanes provided where necessary.

Three major interchanges were required at the junction with the A.64, Tenter Hill, Bramham, and the A.659 at Boston Spa Cross Roads.

The design criteria adopted were the same as those for previous schemes.

The alignment was proved on site by triangulation based on the Ordnance Survey National Grid System. The intersection points were set out on site from local detail and then their respective co-ordinates were found by triangulation from O.S. 'trig' stations. From the co-ordinates the lengths and bearings of the straights between 'I.P's 'were found and the horizontal curve data was worked up. Accurate measurements were then taken from a point of known co-ordinates to control points such as road crossings or buildings close to the improvement and vertical alignment was finalised.

Pavement construction consisted of crusher run stone sub-base in depths of 6 in. to 1 ft. 6 in. according to the C.B.R. values of the sub-grade. In situ marginal haunches were constructed 12 in. wide and 14 in. deep.

A composite base of 7 in. of lean concrete and 3 in. of tar bound base was used, followed by rolled asphalt base course 2¼ in. thick and 1¼ in. wearing coarse asphalt with ¾in. precoated chippings.

The earthworks involved approximately 550,000 cu. yds. of imported granular filling material which includes pulverised fly ash. The drainage was generally a piped system on fill and french drains in cutting.

The bridges on the contract included a four span overbridge at Bramham Cross Roads carried the A.1 over the Leeds-Tadcaster Road (A.64). The deck of inverted pre-tensioned T-beams and in situ deck slab was constructed in two halves making a total width of 88 ft. The decks were supported on slender reinforced concrete wall type piers and skeleton abutments concealed beneath the approach embankments.

Micklefield to Boroughbridge2At Bowcliffe Hall a single span accommodation bridge was constructed to give access to this historic house. This bridge was similar to Rawfield Lane Bridge at Brotherton, but the three main post-tension deck beams were cast and stressed in situ.

Tenter Hill underbridge consisted of a pre-tensioned deck slab transversely stressed with Macalloy bars and supported on mass concrete abutments with reinforced concrete cantilevered wing walls.

Millthorpe Lane underbridge was similar in construction to Tenter Hill but without transverse stressing and the abutments were constructed on the counterfort principle.

At Boston Spa the intersection between the A.659 and A.1 consisted of two three span bridges constructed with post-tensioned T-beams traversely stressed supported on reinforced concrete abutments. These two bridges carried the A.1 over the A.659.

Throughout the scheme abutment finishes and artistic treatment to fascia beams were similar to those used for the Brotherton-Micklefield Improvement Scheme, again with the help of the County Surveyor's wife in choosing the colours!

An "Armco" culvert 280 ft. long was used to bridge the stream at Bramham Beck. This culvert was 13 ft. in diameter and the No.1 gauge multiplate pipe was protected with two coats of heavy grade bitumastic paint applied during and after erection.

The contract, awarded to A. Monk and Co. Ltd., commenced on 8th April 1963. The cost of the works was in the order of £2.4 million.

The whole of this section of the A1 was replaced in the upgrading to motorway status carried out in the 90's and will be returned to later.

The Wetherby By-pass and Wharfe Bridge

The small and ancient market town of Wetherby is situated on the north bank of the River Wharfe. There has been a bridge across the river since 1233. The original three arch hump backed bridge was 11 ft. wide.

The by-pass of Wetherby, was opened to traffic on the 26th October 1959. It was the first planned improvement scheme in the country on the Great North Road.

Some 2¼ miles in length, the by-pass starts with the bridge over the River Wharfe and rejoins the Great North Road near the famous Wetherby Race Course.

The contract for the by-pass was let to Crowley Russell and Co. Ltd. In Oct 1957 for the sum of £493,000. The sub-contractors for the Wharfe Bridge were the Cementation Co. Ltd.

Micklefield to Boroughbridge3The Wharfe Bridge was the first new major bridge to be built in the West Riding. The bridge is of balanced cantilever and suspended span construction, with two side spans each of 96 ft. and a central span of 160 ft., the length of the cantilevers being 45 ft. each with a suspended span of 70 ft.

The bridge was designed in accordance with the requirements of the Ministry of Transport for 45 units of abnormal loading.

The bridge has an angle of skew of 13 degrees. It carries two 24 ft. carriageways, two 8 ft. footpaths, not being a motorway, and a central reservation 10 ft. wide, the width between parapets being 74 ft.

The design for the elevation of the bridge was approved by the Royal Fine Art Commission who took a keen interest in its appearance as the bridge occupies a commanding position in a setting of considerable rural beauty.

The anchor spans and cantilever arms were constructed in reinforced concrete, the deck slab being similarly constructed, and cantilevered out to carry part of each footpath and forming a feature of the elevation.

The central suspended span comprised of pre-stressed post-tensioned concrete beams, with a reinforced concrete deck. Two rectangular fascia beams have curved soffits in profile with the cantilever arms.

The bridge was designed to give a permanent downward force at the abutments under working loads. For ultimate load conditions, 2 in. diameter mild steel eyebolts were provided, dowelled into the mass concrete of the abutments but free to move with expansion and contraction of the bridge. The abutments and wing walls were constructed of mass concrete, taken down to a rock foundation, and faced where exposed with squared snecked rubble masonry.

The two piers are constructed of mass concrete, taken down to a rock foundation just below the level of the river bed. The surface finish to the piers consists of a multiple needle point tooled finish to the concrete which had previously been left with a textured surface provided by means of a special plastic lining to the shuttering.

The balanced cantilever beams, eight in number, are 4 ft. in width and about 17 ft. deep at the piers tapering to the depth of 6 ft. at each abutment and 8 ft. at the outer ends. They are fixed in position at the piers but have freedom of rotation.

The external treatment for the bridge is also a multiple needle point tooled finish.

The deck slab is 12 in. thick throughout being doubly reinforced, and projecting beyond the fascia beams about 4 ft.

The falsework for the cantilever arms was built up on a staging of steel beams carried on timber piles driven into the hard bottom of the river bed. This falsework consisted of tubular steel scaffolding which carried the timber bearers for the cantilever soffit shutters.

The falsework for the anchor arms was of similar construction except that timber piles were only used to carry the scaffolding over the low ground adjacent to the piers. Over the remaining area the tubular scaffolding was built up on mass concrete foundations, or on higher ground, near the abutments, on timber sleepers.

The pre-stressed post-tensioned I-beams were manufactured on site, all cables being pre-stressed before erection except in the case of the outer beams which were partially stressed before erection and finally stressed after construction of the deck slab.

Micklefield to Boroughbridge4Positioning of the beams was carried out by means of a temporary launching girder. Each beam was carried out on bogies and jacked down into its final position after removing the launching girder sideways.

After the erection of the I beams, transverse diaphragms were cast between the beams and pre-stressed using straight cables. Pre-stressing with the Gifford-Udall system of 0.276in. diameter wires was used throughout.

The eight main beams are supported at mild steel rocker bearings, housed in prefabricated mild steel boxes set into the abutments. The rocker boxes were filled with a soft bitumen to prevent corrosion of the rockers yet allow movements due to temperature changes.

The centre span beams are carried at the fixed end by a pair of 2 in. thick mild steel plates, the lower plate being shaped convexly and fitted with a locating key. At the expansion end, the beams are supported by mild steel rocker bearings. They are housed in bitmen filled prefabricated boxes and set into the transom beam of the cantilevers.

Three expansion joints are provided in the structure, one at each abutment and one at the free end of the 70 ft. suspended span. The expansion joints in the carriageways and footpaths consists of a 2in. butyle rubber strip between two mild steel angles which was compressed until the gap was reduced to 1½ in.

Concrete was made with Quartzite gravels from the Doncaster area from a single source to avoid unpleasant differences of colour and to obtain an appearance after tooling which would blend with the stone of the district.

The exposed faces of the piers and bridge elevations were given a silicone treatment, used for the first time in the West Riding to reduce the effects of grime and road dirt. The damaging effects of the use of de-icing salts not yet having been recorded!

The entire surface area of the deck slab, footpath and central reservation, was covered with a ½in. thick asphalt waterproofing upon which was laid a protective layer of concrete averaging 3in. in thickness.

The construction of the roadworks was not without its problems. Scott records "the ground north of Sandbeck Lane was so bad that we did not strip the turf or top soil. The area was covered with magnesian limestone waste from an old quarry at Collingham which included large blocks of stone.

North of this fill area we went into cutting about 20 ft. deep. When excavating the drainage trench at a depth of 6 to 7 ft. we came across a strong spring which would have been 25 to 30 ft. below the original surface. We put a hopper bottom manhole cover over the spring to collect the water and let it run down the completed drain to the outfall.

The outfall drain was through very bad ground and was laid on a bed of straw and brushwood as it was below the water table. Only two pipe lengths at a time were excavated as the trench would not stand."

The carriageway was surfaced with 3¼ in. of hot rolled asphalt and the footpaths with 1 in. thickness of ¾in. single course tar macadam with a top course of ¼in. fine cold asphalt. In the central reservation the base course consisted of ¾in. single course tar macadam laid 1¼ in. thick.

With the opening of the by-pass in 1959, who could have foreseen that this was to be by-passed some 29 years later in 1988. The final cost of the works was £571,000.

One other event is recorded. The railway bridge adjacent to the Wetherby Racecourse was altered to provide additional clearance for electrification of the Wetherby - York line. The line was closed by Beeching about the time the by-pass opened.

Wetherby to Allerton Station

Although there is little on record of this scheme, it, nevertheless, involved the improvement of the Great North Road from the Wetherby By-pass to Allerton Station.

The contract awarded to Crowley Russell & Co. Ltd. for £488,000 started in Feb 1959 and was completed in August 1960.

The construction included the provision of a second 24 ft carriageway over a distance of 4 miles and included the widening by some 20 ft of existing Walshford Bridge which carried the A1 over the River Nidd. This is an open spandrel skew arched bridge in reinforced concrete.

The company had to pay cash for everything delivered to site and was in undoubted financial difficulties. Although completing the contract the company did eventually fail.

The construction of a new bridge to carry the A1 over the Harrogate and York Railway line at Hopperton was still under design when this contract was underway. The scheme for this bridge known as Hopperton Station Diversion was let as a separate contract being awarded to Dowsett Engineering Construction Ltd.

Hopperton Station Diversion

The geological map of the area showed silty sand overlying up to 35 ft. of boulder clay giving way to stiff clay in Bunter Sandstone. The soil survey indicated a high water table.

British Railways did not normally allow driven piles adjacent to its tracks, but as the West Riding Bridges Section had encountered serious difficulties with bored piles on other projects in similar strata a case was presented for the use of comparatively light BSP cased piles.

The driving equipment comprised a timber piling trestle and a 3 ton cylindrical hammer driven from a 38 RB machine.

Following satisfactory results for the test piles loaded with kentledge to over 100 tons, the remainder of the piles were ordered in lengths corresponding to the test depths driven.

During piling operations British Railways imposed a 20 mph speed limit on both tracks, and particular attention was paid to this stretch of line by the plate layers for the duration of the piling operation, some 96 piles being driven.

The blinding concrete through which the piles were driven on completion was found to have risen 18 in.

The scheme undertaken by Dowsett Engineering Construction Ltd was opened to traffic in 1962 at a cost of £245,000.

Allerton Park Flyover Scheme

Micklefield to Boroughbridge5The Allerton Park scheme replaced the staggered junction of the A59 with the Trunk Road A1 some 5 miles north of Wetherby.

The works designed in the late 60's consisted of re-alignment of the A59 and included the crossing of the Harrogate-York railway at Goldsborough Station and the A1 at Allerton Park.

Although the Road Construction Units were now in operation the scheme was designed in the Highways and Bridges Department of the West Riding County Council.

The contract was awarded to A. Monk and Co. Ltd and the total cost was approximately £1,000,000. General roadworks amounted to £760,000 and the Allerton Park Flyover and Goldsborough Station Bridge accounted for the balance of £240,000 of which some £88,000 was expended on piling works. Construction started in July 1969 and was completed in 1971.

Allerton to Boroughbridge

Boroughbridge was once the place at which Edinburgh stagecoaches diverted through North Allerton. The Great North Road met the old Roman road from York on the south side of the River Ure. The old arch river bridge was built by 'Blind' Jack Metcalfe, the Yorkshire road engineer who as already mentioned preceded Telford and McAdam in the design of road pavements. A trio of megalithic stones, "The Devil's Arrows", adjacent to the modern highway has been ascribed to a meeting place for the celebration of Druid rites.

The last of the West Riding major improvement schemes on the Great North Road before crossing the County Boundary into the North Riding was that between Allerton and Boroughbridge and included several diversions.

The scheme consisted basically of the duplication of the existing single carriageway by the construction of a new 24 ft wide carriageway for a length of 3¼ miles between Allerton Station and Gibbet Hill. Also included were three dual carriageway diversions at Allerton Grange, Claro House and the White Gables Café for a length of 1¾ miles.

The final surfacings were 1¼ in. thick high stone content hot rolled asphalt on a 2¼ in. thick hot rolled asphalt base course.

The earthworks involved some 225,000 cu. yds. of cut and fill.

The contract was awarded to A. Monk and Co. Ltd and was completed in Nov. 1960 at a cost of £586,000.

With the exception of the Allerton Park Flyover Scheme, all schemes described so far, amounting to some £12 million, were undertaken by the Highways and Bridges Department of the West Riding County Council as Agent to the Ministry of Transport.