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M6 motorway through Lune Gorge
Low Borrowbridge, south of Tebay, Cumbria, UK
associated engineer
Scott Wilson Kirkpatrick & Partners
date  October 1967 - 23rd October 1970
era  Modern  |  category  Road  |  reference  NY607012
The most topograpically difficult section of the M6 motorway is the stretch that runs through the Cumbrian Mountains. And the most spectacular part of the route is the natural gorge of the River Lune, which lies south of Junction 38. Within a 4km length of roadway, there are eight underbridges to the motorway and three bridges for the diverted A685.
The gorge route has been well used since Roman times, when it connected the headquarters of the Roman army garrison on Hadrian's Wall at Carlisle to the legionary fortress at Chester. Joseph Locke also chose it in the 19th century as the route for the Lancaster & Carlisle Railway. The mountains form an east-west barrier and the Lune Gorge is an obvious north-south access way other routes would require tunnelling or viaducts, whether for railways or roads.
A route for what we now know as the M6 was included in the national system of motorways proposed by the Institution of Highway Engineers in 1936. A similar route was proposed by the County Surveyors' Society in 1938. World War II put any further developments on hold for nearly two decades.
When further devlopments did take place, a route via the gorge and Tebay was proposed and surveyed. However, local protests led the Ministry of Transport to consult Scott Wilson Kirkpatrick & Partners in 1959 "to consider all possible and practical alternative routes between the end of the Lancaster By-pass and Penrith, and recommend the one to adopt".
Three potential routes were identified: the Direct Route, the Killington Route and the Lune Valley Route. After consideration the Killington Route, which followed the Lune Gorge, was selected, principally because it did not require tunnelling and was less expensive.
Construction was divided into five contracts, with the Lune Gorge contract having a ten-month lead time over the others owing to the major structures and large amount of rock excavation required. Tenders were called in October 1966 and construction began in October 1967.
Extensive use was made of computers in calculating the alignments of the carriageways and the geometry of the intersections, and computer printout was used in the Contract Documents for the first time in England.
The M6 is fitted into the landscape by stepping the carriageways for 4km south of Killington, and for 5.6km through the Lune Gorge, with a maximum vertical separation of 9.1m. North of Tebay, the carriageways are separated for 7.2km where the motorway crossed the summit. The maximum separation is 24.4m.
Surface water and sub-soil drainage are dealt with separately, the former using specially designed channel sections with slotted steel covers. Follwoing a site trial, the embankments were laid in layers 2.6m thick separated by drainage layers to make use of wet material.
The A685 (Kendal to Tebay) had to be diverted uphill onto an excavated ledge formed by pre-splitting the rock. A pre-constructed haul road was used to provide site access, and the previously little-known technique of rock bolting was used to stabilise the cuttings. Some 750,000 cubic metres of rock had to be excavated. The adjacent West Coast Main Line railway was protected by a temporary safety fence of anti-submarine netting after testing with a 'runaway' D6 tractor.
The M6 (Lancaster to Penrith) has a maximum elevation of 316m and dual three-lane carriageways with hard shoulders and flexible surfacing. It opened on 23rd October 1970, and cost of 11.7m to construct.
Main contractor: John Laing Construction Ltd
Research: PD
bibliography
"The Motorway Achievement Building to Network: The North West of England"
by Harry L. Yeadon, Motorway Archive Trust
Phillimore & Co. Ltd, Chichester, 2005
"A History of British Motorways" by George Charlesworth
Thomas Telford Ltd, London, 1984
www.ukmotorwayarchive.org
Location

M6 motorway through Lune Gorge