INTRODUCTION
SITE MAP
PRINCIPAL FEATURES
BARRIER PROFILES
BARRIER STATISTICS
THE HUNDA BARRIER
THE WORKFORCE: ITALIA IN ORCADIA
BLOCKSHIPS
Further reference:
Allen, Jack, 'Laboratory experiments in connexion with causeways closing the eastern entrances to Scapa Flow', The Institution of Civil Engineers, Maritime and Waterways Engineering Division, Maritime Paper No.4, Session 1945-6, 3-23.
Cormack, Alastair and Anne, Bolsters, Blocks, Barriers, The story of the building of the Churchill Barriers in Orkney (The Orkney View, Kirkwall, 1992 and later editions).
Ferguson, David M et al., The Wrecks of Scapa Flow (The Orkney Press and Stromness Museum, 1985).
Hewison, W S, This Great Harbour, Scapa Flow (The Orkney Press, 1985 and later editions).
King, John Lewis, 'Maintenance of some rubble breakwaters: (a) Scapa Flow Causeways, 1945-50', The Institution of Civil Engineers, Maritime and Waterways Engineering Division, Maritime Paper No.16, Session 1950-51.
MacDonald, James, Churchill's Prisoners, The Italians in Orkney 1942-1944 (Orkney Wireless Museum, 1987 and later editions).
Orkney's Italian Chapel (Chapel Preservation Committee, no date).
Seath, James Abercrombie, 'Causeways closing the eastern entrances to Scapa Flow', The Institution of Civil Engineers, Maritime and Waterways Engineering Division, Maritime Paper No.5, Session 1945-6, 24-65.
Simms, Wilfrid F, The Railways of Orkney (Privately published, Worthing, 1996).
Scapa Flow was ideally suited to serve as the wartime fleet anchorage for the Royal Navy in both World Wars. However, the four main channels on the eastern side of the Flow were known to be weak-spots in its defence, and in the first war blockships were sunk as a protection against enemy submarines and torpedo-carrying craft. The inadequacies of the blockships 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, 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 World War II prompted the construction of permanent barriers across the four channels. 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 under the direction of Professor A H Gibson and Dr Jack Allen. Not finally breaking the surfaces of the channels until 1942-3, 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 2,000. 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 remarkable and pioneering feat of engineering and organisation were Messrs 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, the firm of Balfour Beatty soon moved into civil engineering, and by 1937 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 tight-rope walker, Jean Blondin (1824-97), famous for his high-wire crossings of the Niagara Falls, two of the cableways were paired across Kirk Sound, the deepest of the channels.
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 2.3km 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 18m in depth. In total, the barriers absorbed 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.
ACCOMMODATION
SS ALMANZORA
SHORE CAMPS
- St Mary's, Holm, Rock Works HQ
- Lamb Holm
- Warebanks (North Burray)
- South Burray
QUARRIES
- Grimsetter (Bossack) Quarry (pre-existing)
- Moss Quarry
- Lamb Holm Quarry
- Glims Holm Quarry (abandoned October 1942)
- Warebanks Quarry, superseded by Links Quarry
- Housebreck Quarry, Burray
- Hoxa Quarry, South Ronaldsay
CASTING YARDS AND BLOCKYARDS
- Bossack, Tankerness
- St Mary's, Holm
- Lamb Holm
- Warebanks, North Burray
- South Burray
TRANSPORT
LANDING FACILITIES
- Pier, St Mary's (pre-existing)
- Pier, Lamb Holm
- Pier, Glims Holm
- Pier, North Burray
- Pier, Burray village (pre-existing)
RAILWAYS
Four route miles of two feet, three feet and standard gauge track on Lamb Holm, Glims Holm and (most extensively) North and South Burray, serving piers, quarries and blockyards.
POWER SUPPLY
- Small generating stations on East Mainland at St Mary's and Grimsetter, one 200kw set each
- Principal generating station, Lamb Holm, two 325kw sets
- Generating station, Warebanks, North Burray, one 260kw set
- Generating station, South Burray, one 260kw set
AERIAL CABLEWAYS
- Four electrically-driven cableways (transferred from Kut Barrage on the River Tigris, Iraq), two being paired across Kirk Sound because of its greater depth
- One steam-driven cableway (transferred from Dornie, Wester Ross) used for East Weddel Sound
(reproduced from J A Seath, 'Causeways Closing the Eastern Entrances to Scapa Flow', The Institution of Civil Engineers, Maritime Paper No 5, Session 1945-1946)
TYPICAL CROSS-SECTION
LONGITUDINAL SECTIONS
KIRK OR HOLM SOUND (NO 1 BARRIER)
- Begun with loose rubble July 1940; re-commenced with bolsters and cableways 1941-2
- Reached low water closure by March 1943, high water by April 1943
- Length 2,000 feet, maximum depth 59 feet
- Estimated maximum current velocities 12.2 knots east-going, 2.9 west-going
- Absorbed 219,981 cubic yards of rock
SKERRY SOUND (NO 2 BARRIER)
- Begun with loose rubble July 1940; re-commenced with bolsters and cableways 1941-2
- Reached low water closure by April 1943, high water by June 1943
- Length 2,100 feet, maximum depth 50.5 feet
- Estimated maximum current velocities 7.6 knots east-going, 10.6 west-going
- Absorbed 130,100 cubic yards of rock
EAST WEDDEL SOUND (NO 3 BARRIER)
- Begun June 1941
- Reached low water closure by May 1942, high water by August 1942
- Length 1,400 feet, maximum depth 38.5 feet
- Estimated maximum current velocities 9.0 knots east-going, 5.2 west-going
- Absorbed 62,962 cubic yards of rock
WATER SOUND (NO 4 BARRIER)
- Begun July 1942
- Reached low water closure by March 1943, high water by May 1943
- Length 2,050 feet, maximum depth 41.5 feet
- Estimated maximum current velocities 4.5 knots east-going, 6.5 west-going
- Absorbed 109,045 cubic yards of rock
CONCRETE BLOCKS: COMPOSITION, PRODUCTION AND USE
A concrete mix of 1: 2: 4 was adopted, using Rousay flagstone as aggregate. A typical mix comprised four bags of rapid-hardening cement (112lb), 6.3 cubic feet of sand, 20 cubic feet of crushed stone aggregate, and 25 gallons of water (using salt water at St Mary's and Lamb Holm, and fresh water at the other three yards). Warebanks on North Burray was the first yard to go into production - in September 1942 - and was the last to finish - in October 1944.
The blocks were of three different sizes and weights: 10-ton blocks measuring 7 x 5.5 x 4 feet; 5-ton blocks 5.5 x 3.5 x 4 feet; and 4.8-ton roadway blocks, 7 x 3.5 x 3 feet. Total production of each of the three sizes amounted to 15,036, 34,384 and 2,206 respectively.
PERFORMANCE OF THE BARRIERS
It was acknowledged that the demands of wartime had limited the amount of experimentation that could be conducted prior to commencement of the works. It had also meant that in the actual construction much of the quality of the rubble core material was inferior to that which would otherwise have been used. Under these circumstances it was always anticipated that there would be considerable settlement or consolidation in the rubble embankments, at least for the first few years, especially given the flexibility of the novel design which allowed water to flow through it between different tide levels on either side, and especially given the effects of severe wave action driven by fierce winter storms in these latitudes.
From 1945 until 1947 the performance of the barriers was thus closely monitored, and it was found that especially in causeways 1 and 4 (across Kirk and Water Sounds) there had been an alarming degree of settlement which, on investigation, was found to coincide with areas of silt-like crushed or laminated rock on the sea-bed, not anticipated in the original geological survey. The worst section of No 1 was reconstructed in the summer of 1947; the remainder of it was undertaken in 1948, and work on 2 and 4 followed in 1949 and 1950 respectively. Settlement on No 3 causeway was so slight that no reconstruction was considered necessary. In the rebuilding, only 70% of the original hardcore was considered fit for re-use. On this occasion, before the upper, pell-mell blocks were replaced, marine asphalt was used to bind the rubble core and to better protect it from scouring and erosion.
THE HUNDA BARRIER
Built close to the line of a natural reef or ayre between Burray and Hunda, this structure was begun in March 1940 and was completed in the autumn of 1941 by Messrs Balfour, Beatty & Co Ltd under a separate contract pre-dating the main group of barriers. Unlike them, it is a solid stone embankment sealed with a concrete skin, and it appears to have been designed and built - evidently at some expense - both as a barrier and a causeway from the outset, perhaps in connection with un-realised defence works on Hunda. About 1,800 feet in length with sloping flanks, it incorporates an open 'carriageway' some 10-12 feet wide, capable of taking vehicles (but only just - as the writer can testify!) and standing well above mean high water levels. The bulk of the stone came from a quarry on Hunda which is visible on the right-hand of this view, just beyond the western end of the causeway.
THE WORKFORCE: ITALIA IN ORCADIA
Because of the sheer amount of other war work being undertaken elsewhere in Orkney, labour was generally in short supply and often of indifferent quality. From the outset the workforce had to be imported and had to be accommodated in four main camps built for the purpose: St Mary's, Holm (the Rock Works HQ); Lamb Holm; North Burray (Warebanks); and South Burray (Burray village). In the first phase of the work from 10 May 1940 some 250 men and essential stores and plant were landed from the SS Almanzora, a veteran 16,000-ton ocean liner from the Royal Mail Service. Three piers had to be built as a matter of urgency, and during this phase some of the men lived in tents on Lamb Holm and Glims Holm. By mid-September 1940, however, hutted shore camps had been established and the Almanzora was released for other duties.
As is well known, the workforce was substantially augmented as a result of military success in North Africa which led to the importation of the first 600 Italian prisoners-of-war from January 1942 onwards. They were specially selected because of their skills and housed in two camps created for them: Camp 60 on Lamb Holm; and Camp 34 at Warebanks on North Burray. After some initial difficulties, a relaxed interpretation of the Geneva Convention allowed the barriers to be recognised as causeways for potential civilian use, appropriate for PoW work, and the two British camp commanders subsequently did much to sustain morale among the Italians. Continuing as employees after the capitulation of Italy in September 1943, the Italians finally left Orkney in the following September when the construction work was to all intents and purposes complete. At maximum, in 1943, some 1,200 Italians and about 520 British were engaged in the work, the normal respective strengths being about 920 and 350.
Famously, thanks to the inspired artistry of one of their number, Domenico Chiocchetti (1910-99), and his team of craftsmen, they bequeathed surviving monuments at Camp 60 on Lamb Holm in the form of a statue of St George, created out of a cement-covered framework of barbed wire, and a charming little chapel completed in 1944 out of two Nissen* huts laid end to end, a perfect evocation of Italy under cold, northern skies. A less elaborate chapel at Camp 34 on Burray was removed after the war, but a few illustrations of it can still be seen at the Fossil Museum on Burray.
One official report registers 10 fatalities which occurred during the course of the works and the clearing-up operations, seven of which were due to drowning.
*Named after the creator of this type of prefabricated structure, Peter Norman Nissen (1871-1930), American-born (of a Norwegian father and English mother) British army officer and mining engineer. See Fred McCosh, Nissen of the Huts (B D Publishing, Bourne End, 1997).
(reproduced from D M Ferguson et al., The Wrecks of Scapa Flow (Stromness, 1985)