The Menai Bridge - Telford's wonderful design
The need for a new design
The Menai Straits, separating Anglesey (Ynys Mon) from the Welsh mainland, are narrow but treacherous. The tide races in from both ends, creating fast currents and whirlpools (swillies) that can easily swamp a small boat. Crossing the Straits was therefore extremely hazardous before it was bridged, with drovers being forced to swim their cattle ashore at low tide.
The strategic importance of Anglesey, being the closest part of either England or Wales to the Irish capital of Dublin, became even greater after 1800, when Ireland became united with Britain to form the United Kingdom. The port of Holyhead, at the northwestern tip of Anglesey, could only reach its full potential with a bridge across the Menai Straits to carry traffic along Telford's route from London that today carries the designation of the A5.
Thomas Telford (1757-1834) was a Scottish engineer who had built many roads, canals and bridges before the Menai bridge project presented itself, and he was the obvious candidate for the job. At the same time, he was working on the coast road from Chester to Bangor, and his bridge at Conwy was opened in the same year as the Menai bridge.
The particular problem with the Straits was that tall-masted sailing ships also needed to navigate the Straits and, given the difficulties presented to sailing vessels in this narrow channel, the bridge span needed to be wide enough to accommodate two vessels passing each other, one of them beating against the wind. At the same time, the roadway needed to be level to suit horse-drawn vehicles hauling heavy loads. An arched bridge was therefore not desirable, given the span to be crossed.
The solution was a suspension bridge. Although the principle of the suspension bridge was well known at the time, nothing had previously been attempted on this scale. The span was to be 580 feet and the height above the water 100 feet.
Building the bridge
Construction began in 1819 with the stone piers and arches that stride part of the way into the water from each side. These were completed in 1824, then tunnels were driven into the rocks on either side to anchor the chains that would support the rods holding the roadway. The connection of the first chain was made to great applause and the accompaniment of a fife and drum band. A further 15 chains followed.
The roadway, originally made of wood, was eventually lifted into place to complete the bridge, which was opened to travellers on 30 January 1826.
Various changes have been made over the years to strengthen the bridge and allow it to carry heavier loads. The most recent of these projects was in 1999, and the bridge's metal parts were last repainted in 2005.
However, Telford's design, ideal for 1826, is not so well suited to modern traffic. The narrow entrance arches to each single carriageway make it unsuitable for today's juggernauts, which in any case had to negotiate the narrow streets and awkward bends of Bangor, just a mile or so from the bridge.
A disastrous fire in 1970 on the Britannia railway bridge, just a mile along the Straits, proved to be a blessing in disguise, as its reconstuction could then include a roadway running above the rail tracks. This is now the preferred route, leaving Telford's bridge to carry local traffic. The Menai Bridge is, however, still an elegant addition to Britain's industrial heritage.