Civil Engineering heritage: Scotland - Highlands and Islands

Date 2007

Event ID 963047

Category Descriptive Accounts

Type Publication Account

Permalink http://canmore.org.uk/event/963047

Churchill Barriers, East Mainland – South Ronaldsay, Orkney

(Institute Civil Engineers Historic Engineering Works no. HEW 1984)

Scapa Flow was ideally suited to serve as the wartime fleet anchorage for the Royal Navy in both world wars, but the four main channels on the eastern side of the Flow were known to be weak spots in its defence against enemy submarines and torpedo-carrying craft. In 1915, William (later Sir William) Halcrow was invited to consider the building of permanent barriers across these channels, but sunken blockships were considered to be a more expedient solution. Some of the blockships were later removed or shifted their positions, and their defence inadequacies were exposed in October 1939 when a German U-boat found a way round them in Kirk or Holm Sound, the deepest and fastest flowing of these channels. It torpedoed the battleship HMS Royal Oak, with the loss of 833 lives, and escaped by the same route.

This dramatic episode at the very start of the second world war prompted the construction of permanent barriers across the four channels, a scheme which was finally authorised by Churchill himself after a visit in person in March 1940, hence their name. On-site preparations commenced in May 1940, and during the summer of 1940 limited experiments were conducted on models in the Whitworth Engineering Laboratories at the University of Manchester.

Not finally breaking the surfaces of the channels until 1942–43, the barriers became recognised as causeways for potential civilian use, and a relaxed interpretation of the Geneva Convention allowed the labour force to be augmented substantially by Italian prisoners-of-war from early 1942 onwards. At its peak in 1943 numbers engaged in the operation reached about 2000. Costing some £2 million, the works were effectively completed in September 1944 but were not officially opened until 12 May 1945, four days after VE day.

The contractors for this feat of engineering and organisation were Balfour Beatty & Co. Ltd, the southern section of the southernmost barrier being sub-contracted to William Tawse & Company, Perth. Founded by George Balfour and Andrew Beatty in 1909 as general and electrical engineering contractors, by 1937 the firm of Balfour Beatty had established a major presence on the other side of Scapa Flow, building the additional above-ground oil tanks at

Lyness on Hoy.

The barrier scheme was designed and supervised by Sir Arthur Whitaker, Civil Engineer-in-Chief of the Admiralty, and was carried out under the direction of H. B. Hurst who was succeeded by C. K. Johnstone-Burt, Herbert Chatley and J. A. Seath. Until 1942 the Resident Superintending Civil Engineer was E. K. Adamson, and from 1942 until completion it was G. Gordon Nicol, whose notes and photographs preserved in the Orkney Archives in Kirkwall constitute a valuable record of the work of construction. A special feature was the use of five aerial cableways, four electrically-driven, one steam-powered, by John M.

Henderson & Co. Ltd, Aberdeen. Nicknamed ‘Blondins’ after the French acrobat and tightrope walker, Jean Blondin, two of the cableways were paired across Kirk Sound, the deepest of the channels. Designed to absorb a through 4–5 knot tidal current, the structure of the four barriers consists of a core of rubble bolsters cloaked by 5 ton concrete blocks below the water line. Except in the case of the less exposed Weddel Sound, which is of 5 ton blocks throughout, these are in turn overlaid by 10 ton blocks, the outer skin being laid in ‘pell-mell’ fashion to break the force of the waves.

The barriers measure some 1 1/2 miles in overall length, linking East Mainland to South Ronaldsay via the three islands (north–south) of Lamb Holm, Glims Holm and Burray. The widest and deepest channel was the northernmost, Kirk or Holm Sound between Mainland and Lamb Holm, where the foundations of what became No. 1 Barrier were laid in fast-flowing tidal water up to 59 ft in depth. In total, the barriers consumed about 250 000 tons

of quarried rubble overlaid by some 66 000 concrete blocks from the casting yards at St Mary’s and on Burray.

The sites of the accommodation camps, rubble quarries, the concrete blockyards and the associated railways are still traceable on the ground, and a chapel on Lamb Holm, cleverly wrought out of two Nissen huts, remains a picturesque memorial to the Italian contribution. (G. Stell)

R Paxton and J Shipway, 2007.

Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.