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Sun October 20 2019

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Rochester bridge refurbishment

26 Sep An important river crossing in Kent is being refurbished. David Taylor reports

The Old Bridge portico
The Old Bridge portico

There’s been a bridge across the River Medway at Rochester, in Kent, since Roman times. The original bridge – the stone foundations of which were rediscovered by Victorian engineers – was built to carry Watling Street (the Romans’ high-speed link between London and the port of Dover) across the river.

Now, almost two thousand years later, Watling Street (these days better known as the A2 trunk road) still crosses the Medway at the same point, connecting Rochester with the town of Strood on the river’s west bank. In fact, the crossing now comprises not one but three bridges: the ‘Old Bridge’, the 1914 steel reconstruction of a short-lived Victorian cast-iron bridge (itself a replacement for a mediaeval stone structure); the ‘New Bridge’, opened in 1970 to increase capacity, and a service bridge between the two carrying water, gas and telecoms.

The bridges are the property and responsibility of a charitable trust, the Wardens and Assistants of Rochester Bridge, which can trace its roots back to the 14th century and the builder of the original stone bridge, Sir John de Cobham, who instituted the Wardens and Commonality of Rochester Bridge to maintain the structure.

Today the Trust owns and maintains the crossings which are as important for today’s traffic and modern life as at any time in their history. The railway bridge, which crosses the river just a few metres downstream of the road bridges, is owned and operated by Network Rail and is not part of the Trust’s estate.

For the past four years, maintenance of the road bridges has been carried out by FM Conway under a term contract with the Bridge Trust. The work mostly involves routine preventive maintenance and small reactive repair work, says Matt Smith, FM Conway’s structures director, but progressive wear and tear has meant that a more comprehensive refurbishment is now required.

Parapet removal works on the New Bridge
Parapet removal works on the New Bridge

“The work we’ve been doing had been getting more and more intrusive until it reached point where the Trust decided that more major maintenance was required,” explains Smith.

Despite its ongoing maintenance contract, FM Conway was not a shoo-in for the £8.5m refurbishment contract. Instead, this was put out to competitive tender.

“The client has three core objectives which have to be satisfied,” says Smith, “and those are heritage, quality and [minimal] disruption to the public”. The Trust felt the need to go to the market in order to ensure that these criteria would be met, he says.

FM Conway therefore had to jump through several hoops in order to convince the Trustees that it was the right contractor for the job. Post-tender interviews were “intense”, says Smith.

The project involves a range of repairs to the various elements of the bridge, including joint replacement and resurfacing works on the bridge decks, repointing and restoration of the stonework parapets, repairs to the steelwork, new lighting and improved drainage.

The project, which got underway in March, is scheduled to last 18 months during which traffic must be allowed to continue crossing the river with the minimum of delay and disruption. 

The bridges are an important commuter route into Rochester from Strood and other towns to the west of the Medway. And although some delay is inevitable on the bridge where work is being carried out, the Trust insists that no user suffers delay more than once a day. 

“In other words, if they’re held up going to work in the morning, they won’t be delayed coming home in the evening as well,” explains Smith.

FM Conway therefore has to ensure that traffic can flow freely on at least one of the two road bridges at all times. The two bridges act as complementary carriageways, the Old Bridge carrying traffic from Rochester across to Strood (east to west) and the downstream New Bridge taking traffic in the opposite direction, from Strood to Rochester. Much of the work is being done at night when traffic is minimal.

To ensure that one of the two bridges is always fully operational, FM Conway is working on the New Bridge first and only moving on to the Old Bridge once that work is finished. 

“We cannot do any work on the Old Bridge until we are 100% finished on the New Bridge,” comments Smith. “That means everything – including snagging. We won’t even start on the method statements and paperwork for the Old Bridge until everything is finished on the New Bridge.”

Smith admits that, given the choice, most contractors would probably choose to tackle the work differently, making more efficient use of labour and equipment. “The work could be done quicker if it was done differently, but that would be to the detriment of the bridge users and that’s unacceptable,” he explains.

Traffic disruption on the New Bridge has been minimised by removing the pedestrian footpath and shifting the traffic over while resurfacing work is underway. This means that two lanes of traffic can still be maintained while one of the lanes is being worked on. The pedestrian traffic is simply diverted onto the Old Bridge in the meantime.

While the logistics of this contract are challenging, the repair work itself is largely straightforward. “A lot of it is standard bridge maintenance work, but paramount is absolute respect for heritage and quality,” says Smith; “That’s the challenge”.

A fair amount of work needs to be carried out to the bridge piers and the underside of the bridge deck so to access this FM Conway is using  bespoke scaffolding supplied by local firm Alltask. “We try to use local specialists wherever possible,” says Smith. 

The scaffold enables below-deck refurbishment to be carried out on all three bridge structures throughout the project without affecting traffic crossing the river.

Masonry repairs are being carried out not only to the bridge structures but also to the river walls and other structures owned by the Trust at either end of the crossing. Repointing and stonework repairs are being carried out by south London- based Paye Stonework & Restoration.

The element of the works with the greatest potential for causing disruption is probably the deck resurfacing and installation of new deck joints. This will take place on the New Bridge this autumn, and on the Old Bridge in spring 2020.

Smith explains: “We will use a mechanical joint system for the replacement. Joints will be made up of two metal carrier rails running across the width of the deck, with an elastomeric insert linking between the two.

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“The advantage of this approach is efficiency – the team will be able to assemble the system on site and install the joint in phases. It means works can take place outside of peak traffic hours, so meeting the Trust’s requirement to minimise disruption to road users.”

The Trust employs a resident engineer to oversee maintenance of the bridge – a post that in previous eras has been occupied by such well-known figures as Thomas Telford, John Rennie and Sir William Cubitt. Today, the resident engineer is Arcadis, which drew up the specification for the project and with whom FM Conway is, of course, working very closely.

Regular meetings involving engineer, contractor and client ensure that progress is monitored and any issues quickly addressed. “If there’s anything we think is potentially problematic we sit down and carry out a thorough workshop with the Trust and Arcadis and make sure we are all fully agreed on a solution before moving forward,” says Smith.

Progress so far has been uneventful; Conway has removed the upstream parapet (which involved the specialist removal of asbestos contamination from the fixing detail on the parapet upstand) and installed a protective barrier. Work will continue in phases, ending with Rochester Esplanade on the eastern bank of the river. Here, FM Conway is installing land drains and a culvert up to 8m deep. 

Community relations are of the utmost importance for the Trust and FM Conway is fulfilling its obligations by providing a dedicated public liaison officer, Helen McConnell, to maintain dialogue with businesses and residents in Rochester and Strood. 

“We have a carefully-planned programme of works but experience tells me things can change very quickly and are often subject to elements beyond our control,” says McConnell. “If or when such an occurrence happens I’ll be doing my best to make sure everyone knows what has happened, why, and what that means. It’s important to me to be approachable and honest, and I hope people will see that as we get to know each other,” she adds.

“We’re keen to be seen as part of the community,” says Smith. “As part of our tender, we undertook to develop an ‘education plan’ which will involve us going out to local schools to talk not just about this project, but also about careers in construction and engineering.

“If you’ve got a big engineering job on your doorstep, why not use it to educate and inform the local community?”

Site team

Client: The Rochester Bridge Trust

Bridge engineer: Arcadis

Main contractor: FM Conway

Scaffolding: Alltask

Masonry restoration: Paye Stonework

Cast iron: Hargreaves Foundry

Paving (Rochester Esplanade): Hardscape

Lighting (design): DW Windsor

Lighting (manufacture): Metcraft

Esplanade planning & design: Barker Langham

Let there be lights

One of the key elements of the bridge restoration is the replacement of the ornate lighting on the Grade II-listed Old Bridge and Rochester Esplanade.

Hertfordshire-based lighting specialist DW Windsor was asked to produce a selection of prototype designs to the Trust’s specification. The selected designs will be manufactured by Metcraft, a specialist in heritage lighting based in Manchester.

The prototypes have been made from variety of materials: steel, copper, iron and 3D-printed plastic. The latter allows for rapid prototype production and easy design modification, but plastic is unsuitable for the finished units, so these will all be made of metal.

So far, DW Windsor has produced bespoke replicas of the Octagonal Lantern design featured on the Esplanade and Old Bridge Strood approach. 

This article was first published in the September 2019 issue of The Construction Index magazine (magazine published online, 25th of each month.) 

UK readers can have their own copy of the magazine, in real paper, posted through their letterbox each month by taking out an annual subscription for just £50 a year. Click for details.

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