The contract for this 7 mile section of the motorway was also awarded to W & C French in the sum of £10.125 million, and was the largest ever undertaken by the company, and commenced on the 1st June 1970.
The Outlane to Hartshead section, traverses the Elland escarpment along which, because of its numerous steeps cloughs, the motorway passes alternately from short deep cuts onto short but high embankments, and extensive benching of the embankments into the steep hillside was required. Along this length is situated the Ainley interchange which, because of the difficult terrain, has had to be situated away from the existing roads which serve it. For this reason a new dual carriageway link road was built to a new roundabout constructed on the A629 Huddersfield - Elland class I road.
Leaving Ainley Top, the motorway passes through a large cutting at Fixby and then drops 480 ft. in elevation over the next 2½ miles before it crosses the River Calder, a canal and a railway by means of the Kirklees viaduct. Because of the sharp drop in altitude, the carriageways are at the maximum allowable gradient and the alignment has been chosen to keep cut and fill areas to a minimum as far as possible; but even so, one of the embankments rises to a height of over 50 ft.
From the Kirklees viaduct the motorway crosses an area where sand and gravel had been extensively worked and the remaining silt filled lagoons were filled with rock before embankments were built over them. At this point the Clifton Interchange, connects with the diverted A644 Brighouse - Dewsbury Class I road. Immediately following the interchange, the motorway passes from high embankment in the 55 ft. deep Clifton cut, where, because of its complex geological formation, which includes many old slip planes, special earthwork and drainage works were included in the contract for this cutting.
After Clifton the motorway crosses Hartshead Moor, where 32 acres of land were acquired for the construction of a service area. Because this was the only suitable site for a service area between Lancashire and the M1, two high pressure gas mains which crossed the site were diverted around the perimeter to allow its full utilisation. The contract for the Service Area was let to Clugston Construction Ltd in the sum of £0.49 million but not until 1971.
The main contract included the construction of the two interchanges, referred to, one at Ainsley Top providing access to the A629 Huddersfield - Elland Road and the A643 County Road and the second at Clifton providing access to the A644 County Road.
The nineteen structures constructed on this contract included Kirklees Viaduct and Whitehaughs Arch.
Kirklees Viaduct carries the motorway over the Mirfield to Brighouse railway, the Calder and Hebble Navigation Canal, and the River Calder. The bridge has six continuous skew spans of 115, 142, 150, 151, 176 and 133 ft. (20 degree skew) and varies in width from 136 to 212 ft. to accommodate the slip roads. The construction consisted of longitudinal fabricated structural steel box and through girders and transverse Universal Beam cross girders. The steelwork acts compositely with an 8 in. reinforced concrete deck. The deck is supported in hexagonal columns, a reinforced skeleton abutment and a reinforced/mass abutment.
Whitehaughs Arch carries the motorway over the realigned Huddersfield Road A629 to Elland at a skew angle of approximately 10 degrees. The bridge is an in situ reinforced concrete fixed arch with a clear span between abutment faces of approximately 88 ft. at springing level and a rise from road level to the crown of approximately 37 ft. The arch is approximately 443 ft. long and is constructed to a horizontal curve of 716 ft. radius and carries a 20 ft. embankment above the crown.
The arch was designed using the West Riding Arch Design Suite of computer programs. The main problem of construction was to maintain traffic flow on the A629 which it spanned. The scheme adopted used two sets of travelling centrings, constructed in two halves, each with a portal frame for through traffic. The arch was constructed in 13 ft. bays with 3 ft. infill gaps. The centring was raised or lowered by means of screw jacks and moved to the next pour on skates.
Thermocouples were cast into test pieces to investigate stress changes due to heat of hydration in the concrete at various stages of construction.
Demec gauges were attached to the centring to monitor loading, and vibrating wire strain gauges were cast into the arch to determine the strains during construction, backfilling and when under traffic. The pattern of behaviour agreed well with design calculations and also enabled the striking of shutters in three days.
Blakelaw Lane Bridge is similar to Hunsworth Lane Bridge on the next contract and has three continuous spans and crosses the motorway at a skew of 30 degrees. The construction is of twin longitudinal steel box girders with a precast composite reinforced concrete deck slab constructed in sections. The deck is supported on reinforced concrete piers and abutments.
This bridge was constructed after the Kirklees Viaduct and although requiring additional steel to meet the Merrison design rules it was possible to introduce most of the modifications at the works.
A start was made on the 1st June 1970, some record of progress is to be found in French's in-house magazine. "Since the official starting date approximately one million cubic yards (760km³) of muck and rock have been shifted, using four 657's, four TS14's and four 769 Dumptrucks with the 988 Loader. In addition, 10,700 lin. yds. (9,784 lin. m) of pre-earthworks drainage has been laid, a start made on five structures and the Kirklees Viaduct.
The contract, running east-west between Huddersfield and Halifax, turns northwards to the east of the River Calder and finishes 1½ miles (2km) beyond the river at Hartshead Moor. Total length is 7 miles (11km), average width 129 ft. (39.3 m) with 15 ft. (4.5 m) central reserve. Heavy earthworks of approximately six million cubic yards (4,580km³) are involved, over 50 per cent of the material to be excavated being rock.
