A chartered civil engineer, Mitchell became bridge master ten years ago. Working in highways and transportation for the former Avon County Council, local government reorganisation saw him looking for a new challenge.

"I didn't think I would get this job," Mitchell recalls. "But I am really glad that I did. It's been a great job for me." Previously, all the work on the Grade 1 listed structure had been handled through a local office of former consultant Kellogg, Brown & Root, but a management report for the bridge trustees proposed the formation of a bridge master role, and required that the successful candidate should be chartered.

Mitchell describes himself as the 'chief executive' of the in-house team now working on the bridge. Three operatives perform a range of maintenance tasks on the structure alongside thirteen full-time bridge attendants, three office staff to process tolls, and a visitor services manager.

The maintenance crew and attendants provide 24-hour coverage on the structure, with two attendants present in the tollbooths at either end at any one time. KBR retained a professional services role, including a regular inspection, although this has now been re-tendered, since the consultant is moving out of the bridge sector.

"This must be one of the longest consultancies I can think of," Mitchell says, "Howard Humphries was employed by the bridge in 1910, I think, and it was subject to takeover after takeover until it reached KBR. There is a tremendous archive at the office which will need to come here. "It's not a massive amount of work by any means," he adds, "but the people at KBR have loved working on the bridge. It a very nice job for a consultant." The contract for regular inspections and structural engineering advice has just been awarded to Flint Neill Partnership, whose director Ian Firth is looking forward to being involved in the first inspection.

It is testament to Brunel's vision that Clifton Bridge has not posed any great headaches in terms of maintenance. But this is no excuse for complacency on such a significant structure. Generating all its revenue from tolls, the trust has a major maintenance fund in place.

"This is a substantial amount of money that is set aside and not touched," Mitchell explains. "It is there to cover major works such as a tower shearing or an anchorage slipping. Situations like this would obviously force us to close the bridge, and this is time with no income."

The insured value of the bridge is approximately US$72 million, which equates to the rebuild cost. Mitchell adds that the maintenance fund is roughly a third of that, although the structure is in excellent shape. Mitchell says that fatigue testing shows that the bridge 'could be good for a thousand years' while the attention of the trust and consulting engineer have kept corrosion largely at bay. Lead oxide primers and bitumen top coats have protected the ironwork while in more recent years the longitudinal and cross-girders were taken back to the bare metal and zinc sprayed before coating with twin pack epoxy paints. Mitchell adds that the whole structure needs repainting every 25 years or so.

The masonry, though, has not received similar attention and, following the celebrations this year, resources and effort will be expended here.

"Repairs have been done with cement mortar over the year and our staff have been down to repoint some of the masonry at the base of the abutment which can take time. But next year we will be looking to tender for a contractor to work on one tower, assess them on the basis of this work and extend the contract accordingly."

Other structural 'housekeeping' includes work on the bolts at the top and bottom of the rods, the middle third of them having been replaced with stainless steel fixings due to wear. Rivets on the structure also fail from time to time due to loading, particularly on the parapet girders.

But the majority of day-to-day maintenance concerns, Mitchell notes with a chuckle, are generally restricted those items that have been added to the bridge to cater for the demands of current users.

The two elements that occupy most of the maintenance crew's time are the tolling machines and the lights. Tolls were collected manually from the opening of the bridge and applied to 'pedestrians, horse drawn vehicles, animals and mechanically propelled vehicles'. Automated toll collection began in the 1970s for vehicles, with pedestrians able to use the bridge for free, and this technology has been replaced twice.

Some 10-12,000 vehicles now use the bridge each day either by cash payment or via prepaid cards for local, regular users. The automated system has brought considerable efficiency savings for the operation of the bridge, but the units need constant maintenance. As Mitchell points out, it is far from ideal for one of the toll machines to fail during peak.

Even some of the more menial maintenance tasks bring with them the ever-present challenge of access. Mitchell reflects on 'considerable changes in attitude, legislation and regulation' regarding health and safety at work. If the Clifton bridge were to be built again, current standards would apply and the access issues would be largely 'designed out'. As it stands, CDM requirements have to be overcome now, and can prove to be a considerable challenge for the in-house team and specialist contractors working on the bridge.

The access problems are brought into sharp focus following the 'discovery' of vaults in the bridge abutments (readback). Previous bore tests had concluded that these were of solid construction, but further investigation proved otherwise.

"It's really exciting when you find these things," Mitchell adds. "There's almost a sense of euphoria. Then, 12 months later when you know the extent of these structures, you realise that this is a major maintenance liability."

Mitchell explains that it cost £30,000 to have a door fitted to give workers access to the vaults. Power and light have also been installed. However, workers still have to gain access to the door via the aid of a rope.

"The lower level vaults are still presenting problems," Mitchell adds. "We really do need to inspect them properly and we will need some specialist camera investigation equipment to do it, I think."

In all these works, though, Mitchell has to be aware of what the bridge means to the people who use it every day, and for those who travel from all over the country and further afield to gaze at the structure. He is painfully aware of the impact major scaffolding works will have on people's experience.

"We believe 500,000 people a year come here to see the bridge," Mitchell adds. "We don't know for certain as we don't charge pedestrians, but there's no doubt that we are quite an attraction for the region."

Keeping the bridge open is also essential as it is the Trust's source of revenue and, although not serving the strategic function it once did, many people still rely on it for their daily travel requirements.

The troubled route from vision to reality:

1753: Alderman of Bristol, William Vick, dies and leaves a £1,000 legacy to Bristol's Society of Merchant Venturers. It is suggested that once this sum has grown to £10,000 through interest, a stone bridge spanning the Avon Gorge should be built to improve city communications and trade prospects.

1829: The fund grows to £8,000 and the Venturers launch a competition despite the projected costs of the bridge being in the region of £90,000. By the closing date, 22 plans have been submitted and, prolific as ever, Brunel provides four designs. Spans range from 760 to 1,180 feet, considerably wider that the suspension bridge 'record' of the time, Thomas Telford's Menai Bridge. Despite a number of novel features, competition judge Telford insists his Menai span is the greatest that can be achieved and deems Brunel's structures unsafe. A design provided by Telford is found to be too expensive.

1830: A second competition is held. Again Brunel enters and, assisted by his father, provides a design of reduced span (630ft, but still longer than Telford's 'record') but which still clears the gorge. Brunel's design is successful and he is appointed project engineer.

1831: Foundation stone is laid.

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