There鈥檚 been a bridge across the River Medway at Rochester, in Kent, since Roman times. The original bridge 鈥� the stone foundations of which were rediscovered by Victorian engineers 鈥� was built to carry Watling Street (the Romans鈥� 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鈥檚 west bank. In fact, the crossing now comprises not one but three bridges: the 鈥極ld Bridge鈥�, the 1914 steel reconstruction of a short-lived Victorian cast-iron bridge (itself a replacement for a mediaeval stone structure); the 鈥楴ew Bridge鈥�, 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鈥檚 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鈥檚 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鈥檚 structures director, but progressive wear and tear has meant that a more comprehensive refurbishment is now required.
鈥淭he work we鈥檝e been doing had been getting more and more intrusive until it reached point where the Trust decided that more major maintenance was required,鈥� explains Smith.
Despite its ongoing maintenance contract, FM Conway was not a shoo-in for the 拢8.5m refurbishment contract. Instead, this was put out to competitive tender.
鈥淭he client has three core objectives which have to be satisfied,鈥� says Smith, 鈥渁nd those are heritage, quality and [minimal] disruption to the public鈥�. 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 鈥渋ntense鈥�, 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.聽
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.聽
鈥淚n other words, if they鈥檙e held up going to work in the morning, they won鈥檛 be delayed coming home in the evening as well,鈥� 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.聽
鈥淲e cannot do any work on the Old Bridge until we are 100% finished on the New Bridge,鈥� comments Smith. 鈥淭hat means everything 鈥� including snagging. We won鈥檛 even start on the method statements and paperwork for the Old Bridge until everything is finished on the New Bridge.鈥�
Smith admits that, given the choice, most contractors would probably choose to tackle the work differently, making more efficient use of labour and equipment. 鈥淭he work could be done quicker if it was done differently, but that would be to the detriment of the bridge users and that鈥檚 unacceptable,鈥� 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. 鈥淎 lot of it is standard bridge maintenance work, but paramount is absolute respect for heritage and quality,鈥� says Smith; 鈥淭hat鈥檚 the challenge鈥�.
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聽聽bespoke scaffolding supplied by local firm Alltask. 鈥淲e try to use local specialists wherever possible,鈥� says Smith.聽
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: 鈥淲e 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.
鈥淭he advantage of this approach is efficiency 鈥� 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鈥檚 requirement to minimise disruption to road users.鈥�
The Trust employs a resident engineer to oversee maintenance of the bridge 鈥� 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. 鈥淚f there鈥檚 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,鈥� 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.聽
Community relations are of the utmost importance for the Trust and FM Conway is fulfilling its obligations by providing a dedicated聽public liaison officer, Helen McConnell, to maintain dialogue with businesses and residents in Rochester and Strood.聽
鈥淲e 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,鈥� says McConnell. 鈥淚f or when such an occurrence happens I鈥檒l be doing my best to make sure everyone knows what has happened, why, and what that means. It鈥檚 important to me to be approachable and honest, and I hope people will see that as we get to know each other,鈥� she adds.
鈥淲e鈥檙e keen to be seen as part of the community,鈥� says Smith. 鈥淎s part of our tender, we undertook to develop an 鈥榚ducation plan鈥� which will involve us going out to local schools to talk not just about this project, but also about careers in construction and engineering.
鈥淚f you鈥檝e got a big engineering job on your doorstep, why not use it to educate and inform the local community?鈥�
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鈥檚 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.聽
This article was first published in the聽聽(magazine published online,聽25th of each month.)聽
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