INDEX TO SECTIONS
Aust to Almondsbury (J21 to J20) - Almondsbury Four Level Interchange (J20) - M4 Almonsbury to Tormarton (J20 to J18) -
M4 Tormarton to Wooten Bassett (J18 to J16) - M4 Wootton Basset to Liddington (J16 to J15) - M4 Liddington To Wickham (J15 to J14)

Aust to Almondsbury (J21 to J20) Richard Costain Ltd were awarded the contract for this 4.5 miles section of motorway at an estimated cost £3 million and commenced work in August 1963. The section was constructed as dual 24ft carriageways to complement the Severn crossing with cycle tracks from the Bridge as far as the Aust interchange. A feature of the length is the additional mile long "Crawler lane" at the approach to the Almondsbury Interchange. At the Aust interchange with the A403 and B4061 a Service Area was constructed by Higgs and Hill Ltd. On this section there are thirteen bridges over or under the motorway and two pedestrian underpasses. Four large Armco steel culverts carry water courses under the road .Over a section of about 1.5 miles the ground below embankment was of poor bearing value and this area was surcharged with ten feet of fill for a period of a year to preconsolidate the ground before construction of carriageway work. Over the whole contract there was a surplus of excavated material amounting to approximately 1 million cubic yards of which 400,000 was used at the Almondsbury site.

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Almondsbury Four Level Interchange (J20) The design of this interchange has been the subject of a Paper presented to the Institution of Civil Engineers by O.A. Kerensky CBE and N.J. Dallard on 19th November 1968 and reported in the Proceedings Volume 40 pages 295 to 321 and volume 43 pages 483 to 495. The interchange was a novel design at the time providing high speed freeflow all-directional movements between the two motorways by means of roads at four levels. The Abutments to the bridges are skew and the columns are articulated by means of spherical bearings at each end. The contract included about 2.5 miles of dual carriageway motorway and 4.5 miles of slip roads. It also included the M5/A38 (J16) interchange and the 36 ft wide collector/distributor roads between the two junctions. Contractor Richard Costain Ltd. was awarded the contract at an estimated cost of £1.9m and commenced work in May 1964. The ground conditions at the site, which were in various stratas of marls, lias and limestone, were troublesome and had to be blasted on excavation. However the works were completed in time for the opening ceremony undertaken by Her Majesty the Queen in September 1966. There are a number of documents referring to the interchange including newspaper cuttings, photographs, papers given to associations and pictures of the opening ceremony. An interesting newspaper article from the Western Daily Press concerns Oleg Kerensky who was the Partner in charge of the project for Freeman Fox and a visit he paid to the contract with his 84 year father Mr. Alexander Kerensky better known as the Russian Leader who endeavoured to build a liberal Russia after the fall of Czar Nicholas II in 1917.

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M4 Almonsbury to Tormarton (J20 to J18) This section of the M4 was let in three separate contracts. The first was from Almondsbury to Hambook including the interchange and the Hambrook Spur road and its connection to the Bristol Ring Road. This contract was awarded, in April 1964, to Sir Alfred McAlpine & Son Ltd.- Leonard Fairclough(AMEC) Ltd. for the sum of £2,342,000 and the works were completed in the contract period of 21 months. The imposing Winterbourne underline steel portal frame bridge carrying the main railway line from London to South Wales was located on this length of the motorway. This was designed by Harry Brompton and Partners and let as a separate contract to A E Farr Ltd in the sum of £ 348,355. With such a busy Railway line which also served Bristol and the North the whole structure had to be rolled into place with limited line occupation. The contract covering the section from Hambrook to Tormarton was also awarded in April 1965 to Sir Alfred McAlpine & Son Ltd.- Leonard Fairclough(AMEC) Ltd. in the sum of £5,277,000 with a contract period of two years. In fact the contract was accelerated so that the road was opened to traffic six months early in tune with the Severn Bridge and the Almondsbury Interchange. On both roadworks contracts the contractor obtained suitable rock for crushing to produce granular sub base and opened borrow pits adjacent to the motorway to win suitable filling materials. The heavy earthworks required at the Cotswold Escarpment were a feature of the second contract where the combination of variable strata in a very deep cutting necessitated the installation of berms for drainage and maintenance purposes.

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M4 Tormarton to Wootton Bassett (J18 to J16) Let in July 1969, under the auspices of Sir Alexander Gibb & Partners, this was the first contract on the section to complete the M4 between Tormarton and the Maidenhead Bypass. The successful contractor for the 19.2 mile length was Sir Alfred McAlpine and the tender sum was £8,886,105 for a 27 month contract period. The contract included some 3,500,000 cu.yds of earth moving and 1,500,000 cu.yds of imported filling materials. As the contractor decided to obtain quarry materials from the quarry opened on the previous length of motorway the construction commenced with earthworks at the western end. As the start of works was in July every effort was made to progress earthworks rapidly and so much earth moving equipment was brought onto the site that the payment certificates for the September and October amounted to over £1 million. (approaching a quarter of the contract price). At the time the comment was made "No other earth moving equipment is available it's all on "Mc's job"! Another feature of the contract was the 28 bridges which were required. Access in many cases was difficult and the designs relied heavily on precasting of the Superstructure. The process of building therefore demanded highly detailed planning and scheduling of manufacture and delivery. In the words of Bill Egerton "It was a nightmare at times". It is recalled there was a measure of controversy during the design about the merit of using precasting techniques for most of the superstructure of bridges. Whilst the Chief Bridge Engineer in the Ministry of Transport (David Holland) favoured the concept, others considered it more costly and complicated and not so aesthetically pleasing. The progress on the contract was excellent and by early summer 1970 the remaining earthwork was a high embankment at the eastern end where the Motorway crossed the railway. Unfortunately foundations here were very weak and a major ground failure occurred under the embankment which required complete reconstruction with subsequent delay. The first part of the contract was opened in June 1971 to the interchange on the A429 near Hullavington and the remainder opened with the rest of the M4 in December 1971.

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M4 Wootton Basset to Liddington (J16 to J15) This section covered a distance of 11.2 miles and included interchanges with the A420 and A345 near Swindon. The contract was let in July 1969 to W.C.French (Construction) Ltd. for a tender price of £6,457,208. It included 2,134,000 cu.yds of excavation and 950,000 cu.yds of imported material. The soil conditions on this section near Swindon included some Kimmeridge Clays, Gault Clays and Greensands and at the eastern end Upper, Middle and Lower Chalks. The Consulting Engineer reported that the Kimmeridge Clay was suitable for filling material but the surface layers were too wet. The handling characteristics of the chalk are not referred to at length but it is known that forming embankments with upper and middle chalk posed problems due to pulverization and high inherent moisture content. The lower chalk was much harder and approached the consistency of rock; a fact born out by the section of cutting east of junction 15 near Liddington where the lower chalk stands almost vertically some thirty years later. To the South of Swindon, in the Kimmeridge Clays, the planned profile of the Motorway required the contractor to excavate into the toe of a slope on side long ground in an area of ancient land slips, or solifluction deposits. These materials were highly disturbed and saturated at the edge of the chalk. The excavation gave rise to a massive slip in the hillside which, at one stage, flowed across the width of the motorway at about one foot per hour. The remedial works on this part of the contract were considerable; necessitating the construction of a split level road with the west bound carriageway raised so that the embankment buttressed the toe of the unstable hillside. In addition an existing road was carried across the Motorway on a viaduct to clear the new motorway profile and a footbridge had to be redesigned. Reference to these problems is included in the Archive in the copy of W.C. French’s house newspaper of the time.

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M4 Liddington to Wickham (J15 to J14) This contract was let to Arthur Monk and Co Ltd. at the end of December 1969 for the tender sum of £7,196,155. The length was 12.2 miles and the tender period was 24 months. The works were located entirely in chalk and required approximately 3,250,000 cu.yds of excavation and over 200,000 cu.yds of imported material. The work was situated high in the Wiltshire and Berkshire downs and included the interchange with the A388 and the Membury Service Area. Monks were an experienced Motorway Contractor, having carried out a number of Motorway projects and their Director, R, Whittle was well known in the Industry as a very knowledgeable contractor. Their Project Manager, Reg Castell, also was well known and had come originally from a structures back ground, having worked for a number of contractors including Tarmac Civil Engineering (now Carrilion Construction) on M5 in Worcestershire. Chalk country is characterized by swallow holes in the strata and this length of Motorway had examples which had to be dealt with. At one bridge site excavations for the foundations exposed a vast cavity which it was decided was a chalk mine and which had to be remedied with large quantities of concrete. No other information of note has been obtained about the difficulties or the success of this section. A more detailed description of the section of the M4 between Holyport (Junction 8/9) and Tormarton (Junction 18), summarised from the opening brochure, can be accessed by clicking here.

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