THE ICONIC Iron Bridge in Shropshire, England, has been lit up as part of a £3.6 million conservation project.
The structure is the first bridge in the world to be made of iron and as the forebear of modern metal framed buildings, is the worldwide symbol of the industrial revolution.
Whilst the edifice has been lit since the late 1970s, the 40-year-old floodlights were outdated, only lit one side of the bridge and were regularly flooded by the River Severn.
The lighting scheme – designed by Liz Peck of LPA Lighting and Bob Bohannon of LuxRapide – was required to celebrate the conservation project and the 50th anniversary of Telford new town.
The project seemed relatively simple at the outset. A feasibility study had determined that the flood risk was regularly in the region of four metres, but could be as high as seven metres as seen after storms Ciara and Dennis in February 2020.
Columns, resistant to that level and force of water were essential.
English Heritage’s clear instruction as the bridge’s guardians was that nothing could be mounted on or underneath it; cables could not be run through or across it; and the daytime visual intrusion of any installation must be minimal.
The client, Telford and Wrekin Council, wanted not only a new scheme, but one which would extend the economic day of the towns of Ironbridge and Telford, to illuminate the downstream side which had previously been left dark from a key viewing point and crucially, to celebrate the magnificence of the history of the crossing.
The original concept for the mid-grey painted bridge was to deliver a white-light scheme for weekdays, a special effect on the weekend and the opportunity to have colour-changing for special occasions.
The weekend effect was inspired by a quote from Morgan Cowles, head of conservation and heritage at English Heritage, in the Sunday Times: ‘Imagine the effect of the bridge lit at night by the fires from the furnaces and forges of Coalbrookdale, the structure glowing a demonic red’ – the weekend effect would thus become ‘furnace’.
This design could be achieved using unobtrusive columns with integrated RGB floodlight heads to deliver both schemes and enable Telford and Wrekin Council to colour-change on special occasions.
Lee Engineering specified and commissioned the control system, a Pharos LPC (lighting playback controller) which allowed for the integration of photocell sensors and was compatible with Lumenradio’s wireless DMX for communicating to the lights across the river.
The combination of the technologies overcome the cabling restrictions and the 4G router allows Telford and Wrekin Council to change programmes from any computer or smartphone.
The LPC 1 unit controls 17 light fittings and supports the final lighting effects: a warm white light scheme during the week and an innovative, dynamic blend of red and amber overlaying a dimmed white scheme for the weekend.
This stylised animated scheme was designed to replicate the historic furnaces and forges that once glowed in the surrounding area and is affectionately called ‘furnace mode’.
The visual is created by altering the intensity of the red and amber floodlights across the bridge.
A laser-cut model of the structure was procured from the Ironbridge Enginuity Museum to physically demonstrate beam angles on spill light and light pollution to over 20 stakeholders, including Telford and Wrekin Council, English Heritage, Enterprise Telford, Historic England and the Unesco World Heritage Site steering group.
During the conservation project, English Heritage discovered patches of the original paint colour: a red-brown, mahogany shade and decided to repaint the bridge this colour; thus mid-way through the lighting design, with budgets outlined and equipment sizes approved, the paint finish changed from a 25 per cent reflective mid-grey tone, receptive to most colours, to a 5 per cent reflective red-brown.
To maintain the required luminance with a much lower reflectance would require projectors with much higher lumen packages, these being commensurately larger, more expensive and needing larger, more visible columns.
Instantly a relatively straightforward project became three years of careful negotiation and the overcoming of numerous challenges.
Among these were the geotechnical issues surrounding installing the now heavier columns into unstable gorge sides in a Unesco World Heritage Site cut through by the River Severn.
Someone once commented that ‘everything moves in the gorge, it’s just a question of how much and how fast’.
With the bridge shrouded in scaffold and plastic sheeting for the conservation project, site trials were out the question, so metal sheets and tins of the new paint were acquired to determine the optimum colour temperature and to test that the furnace effect would still work, having acknowledged that RGB was now out of the question.
Detailed computer models were made to determine quantities and aiming angles to ensure uniformity, whilst minimising glare and spill light through the filigree structure.
To gain planning permission, with the support of Historic England, the use of wooden columns was proposed to soften the daytime appearance.
These had bespoke brackets to bunch the projectors tightly together to reduce height, and bespoke bases to ensure that the wooden shafts were well above extreme flood levels.
These were then located in as unobtrusive places as possible. The floodlights are mainly narrow beam, cross aimed horizontally to capture as much light as possible on the solid stone abutments to minimise glare and spill light.
To overcome cabling restrictions, the automatic controls talk across the river by radio, whilst GSM links enable Telford and Wrekin Council to change programmes from any computer or smartphone, with a backup system in place to ensure system robustness in case of signal failure.
The final effect delivers a warm white light scheme during the week and the innovative dynamic ‘furnace mode’ of red and amber overlaying a dimmed back white scheme for the weekend; the dynamism is created by altering the intensity of the red and amber floodlights, creating the movement of the light from the fiery skies of Coalbrookdale.
The scheme was launched during the Ironbridge Festival and has been applauded by all who have seen it since.
‘It’s amazing to see it finally come to life’, said Peck. ‘It’s been one of the most challenging, yet ultimately rewarding projects of my life.’
There were many days when we didn’t think we’d get to this point, not least when we all witnessed the flood waters in February this year push back the flood barriers in the town, soon followed by national lockdown.
‘The response from everyone in the town has been terrific and we believe this wonderful bridge now has a lighting scheme befitting of its historic significance.
‘It couldn’t have been achieved without the partnership with Bob Bohannon and our brilliant clients at Telford and Wrekin Council, who supported us magnificently throughout.’
‘It’s been a very special project to us,’ said Bob Bohannon, lighting design partner.
‘These projects are always a team effort, so huge thanks are owed to acdc lighting, Aubrilam, Lee Engineering and Nick Gibbons at e-on for their respective hours of help.’
‘Everyone seems blown away by it all,’ said Kathy Mulholland, team leader investment and funding at Telford and Wrekin Council.
‘Particularly of course the furnace effect – and the fact that local residents and businesses are hugely supportive is a clear sign that you’ve got it right.’
THE TECHNICAL SPECIFICATION IN FULL:
- ACDC Fusion 48 projectors, 3000k warm white LED, with anti-glare cowls and louvres
- ACDC Fusion 48 projectors, bespoke red & amber LED boards, with anti-glare cowls and louvres
- Aubrilam bespoke Moshi wooden columns with, lengthened flange bases for flood resistance and bespoke twin projector mounting brackets to limit visual clutter.
- Pharos Controller, photocell sensors, 4G Lumen Radio communication across the river; separate Nicoluadie controller and light sensor for the downstream side, all supplied and commissioned by Lee Engineering.