Official Fire Report
The transcript of the Fire Brigades' report on the 1970 fire gives a vivid account of what occurred on the night of May 23rd.
CAERNARVONSHIRE COUNTY COUNCIL
JOINT REPORT ON A FIRE IN THE BRITANNIA TUBULAR BRIDGE, MENAI STRAITS, ON SATURDAY – MAY 23rd, 1970
DESCRIPTION OF BRIDGE
The Britannia Tubular Bridge connects Caernarvonshire with Anglesey and it was erected and opened by Robert Stephenson in 1850.
The bridge consists of two wrought iron tubes, rectangular in section. Through which are laid the up and down lines of the main London to Holyhead Railway. The tubes are 10 feet apart and are supported by 5 masonry towers, 2 of which are entrances, 2 intermediate and a main tower in the centre of the Menai Straits. The tubes are approximately 150 feet above the level of the Straits at low water mark, and are each nearly 1/3rd of a miler long, and 30 feet high by 15 feet wide. The tubes are continuous in length from tower to tower. The entrances to the tubes are remote and inaccessible from highways.
The location of the Bridge is such that it is in a very exposed position, unsheltered by any land mass from the prevailing winds, and some time after it was erected it was deemed necessary to cover both tubes with a common roof, either to protect the twin tubes from strong eddying winds or the elements or both. This roof was supported on angle iron bridgework, supported by the tubes and on the bridgework was built a roof of one inch thick pine boards supported on heavy wood purlins. The pine boards were tongued together by metal strips. Superimposed on the 40ft wide roof was a 12 foot wide walking platform for maintenance purposes. The whole roof was covered with a hessian material and over the years had been continuously coated with tar. The roof over the twin tubes was continuous for the whole length of the bridge and was not broken even to go through the supporting towers. The void so formed between the wrought iron tubes and the roof was approximately 2 feet 6 inches high.
The main access to the roof was by way of a staircase from the tube entrance, which gave access to both the walkway over the roof and the void below the roof. Access to this roof by unauthorised persons was barred by a heavily padlocked door at the top of the stairway.
The centre supporting tower contained a main store and workshop for maintenance purposes and contained stores of timber, paints, and tar and other necessary materials. Access to the stores was by way of a metal door leading from the tubes.
With the highly inflammable nature of the tarred coating of the tubes, its flue-like construction and a moderate breeze, coupled with the forming of air currents by the exposed position of the structure, it is not difficult to imagine that an accidental ignition of the tarred surface would rapidly turn a small fire into a major conflagration.
At the time of writing, the cause of the fire is not certain, but it is believed to be that it is the result of a Nature Expedition that went wrong. Two youths are believed to have lit paper for illumination to look for birds nests and bats at a point about 12 yards inside the tube entrance, where the main wrought iron tube terminates and the stonework of the entrance commences. The jointing at this point is of timber covered by tarred hessian. The ignition of this timber gave rise to rapid direct burning in a upwards direction to the roof void, and the roof forming the protective covering of the tubes.
An eye witness in the early stages of the fire stated that molten burning material was falling from the roof of the tunnel on the North side to the base of the tube.
FIRE FIGHTING OPERATIONS (CAERNARVONSHIRE)
The initial call to Bangor Fire Station was received at 2143 hours, and response was made by the turnout of a Water Tender and a Water Tender Escape. The travelling distance was 4 miles, and the final 3/4 mile was down rough track. On arrival at the entrance to the tunnel the Sub Officer in charge of the first appliance found the entrance tower well alight, with fire to be seen in the entrance of the tube below the tower. The fire was already spreading rapidly over the roof of the first span of the bridge. Jets were got to work from the appliances and a message was radioed back to Fire Control “Make pumps three”. This message was wired at 2207 hours.
There are no pressure water supplies in the area, and the nearest static water was the Menai Straits approximately 450 yards away down gradients of one in three, and very difficult of access.
In response to the Sub Officer’s request, a further pump was sent on , and two senior officers went on to the scene. The first attending crews carried feather-weight pumps down to the water’s edge to relay water to the major pumps at the tunnel entrance.
At 2224 hours the Divisional Officer who had taken charge radioed a message to Fire Control “Make pumps six”. Main jets were increased to four, but owing to the intensity of the fire in the entrance tower, the branchmen were having great difficulty in maintaining their positions at the access to the entrance tower. Branches were then positioned to work over the buttresses of the tower through a gap were the roof over the tunnel had burned away.
It was decided that if fire fighting efforts were to be successful the fire on the roof of the entrance tower had to be extinguished first, before access to be gained to the roof and voids over the tubes, and this could be only gained through an aperture 3 feet high.
Barring access to this gap in the stonework were 2 sets of 4 15 feet cast iron girders supporting the tubes. These girders were red hot and the application of water caused on of them to snap in half, it was thus feared that if further girders should snap the stability of the bridge might be affected. Every effort was made to avoid this danger, but by the time it was possible to get to the gap in the stonework the whole of the first span was intensely involved, so precluding firemen advancing on to the roof of the tunnel. Jets were then directed in an effort to keep the wrought iron of the tubes as cool as possible.
On the advice of one of the Bridge engineers, a line of hose was run through the tubes to the Central Tower workshops, and on opening the Metal door to gain access it was found that flames were enveloping the tube and the upper part was a raging inferno, notwithstanding that no fire was visible on the outside of this span of th Bridge. Strong jets were applied, but they had no extinguishing effect.
The greatest difficulty in tackling the fire was lack of access to the underside of the common roof spanning both tubes, and the 10 feet gap between the tunes allowing the wind to assist spread of fire to the Anglesey side of the Bridge.
Owing to the height above ground level, it was not possible to get branches to work from ladders.
A ground monitor was got to work in an endeavour to stop the fire spreading through the first intermediate tower, but falling baulks of timber precluded the positioning of the monitor to get best advantage of the its striking jet. A continuous downpour of burning tar set alight trees and undergrowth below the bridge which further impeded operations.
When it was seen that the fire had not been stopped at the first intermediate tower the Divisional Officer sent a further message to Fire Control at 2244 hours stating “Fire spreading rapidly. Request Anglesey Fire Service to send 5 pumps to the Anglesey side of the Tubular Bridge.”
FIRE FIGHTING OPERATIONS (ANGLESEY)
Fed by high winds the fire was racing towards the Central tower and the Chief Officer of Caernarvonshire sent two of his pumping appliances to assist the Chief Officer of Anglesey. It was hoped that with the extra assistance it might be possible to stop the fire at the Central Tower.
The Chief Officer of Caernarvonshire found that the Chief Officer of Anglesey was organising his crews to run lines of hose over the roof of the bridge to get jets to work of the Central tower, but the high wind was taking the heat, smoke and flames directly through the tubes and over the roof to the Anglesey side of the Bridge and concentrating at the entrance of the tubes through which access had to be made to the roof of the Bridge. This was a most dangerous operation which necessitated the wearing of Breathing Apparatus. This was achieved by B.A. teams working in relays. Notwithstanding the dangers, the crews succeeded in running hose on to the roof and getting jets to work on their target.
For a considerable time it appears that the efforts of the Anglesey firemen would be successful, but the fire in the roof void was so severe that it broke out on to the surface of the roof behind the point where the fireman were operating, and the Chief Officer gave instructions to withdraw all firemen from the roof as there was great danger of lives being lost.
It was not possible to retrieve hose and breathing apparatus sets.
Although fire-fighting operations continued through the night, the fire was not contained until it reached the entrance tower in the Anglesey side of the Bridge. Fire fighting crews were occupied throughout the following day in extinguishing fires in the hollow masonry of the towers which were started by baulks of timber falling from the Bridge to the base of the towers.
Fire fighting operations were jointly directed by the Chief Officer of Caernarvonshire in whose territory the fire commenced, and the Chief Officer of Anglesey into whose area the fire spread.
The main contribution to the destruction of the bridge was the design of the roof, and the high inflammability of the material in which it was made. The cavernous nature of the structure allowed fire to travel in all directions and made fire extinguishing impossible.
The terrain, and the height of the bridge was such that there was only one means of getting at the fire, through the room on the entrance tower, with only the frontal attack possible, side attacks to the fire ware not possible and the fire continued unabated.
With the one continual void throughout the whole length of the roof, without any adequate fire blocks in it, it allowed the fire to under-travel in an unchecked manner.
Finally, the fact that there were no pressure water supplies available in the area caused a delay to occur in getting a continuity of water supply on to the fire after the initial supplies of the fire appliance had been utilised.
The Secretary of State for Wales – the Rt. Hon. George Thomas. M.P. visited the scene and inspected the fire damage on Sunday, and asked the Chief Officers concerned to pass on his congratulations to the fireman of both brigades for the brave and courageous manner in which they fought and tackled the fire, and endeavoured to save this vital communications link between the mainland and the county of Anglesey.
Other letters and message of congratulations have been received from the Prime Minister through the Secretary of State for Wales, from Lord Snowdon, Local Authorities and others.
One estimate puts the fire damage at over £1,000,000.