6 NEW CIVIL ENGINEER 26.11.09 | www.nce.co.uk

NEWS

graphic: www.paulweston.info

Cockermouth R. Cocker

CUMBRIAN MOUNTAINS

Keswick

Whitehaven

Workington

Maryport

SkiddawButtermere

Loweswater

Warm moist airmakes landfall overCumbria. DepositsUK record for rainin 36 hours

EnnerdaleWater

Cockermouth

BassenthwaiteLake

R. Derwent

1 Ground alreadysaturated frompreviousrain

2

Water coming downfrom the fells in theDerwent & Cockerconverges onCockermouth & thenWorkington

3 A number of bridgescollapse and othersbecome unstabledue to shear weightof water & scouringof the foundations

4

CrummockWater

Derwent Water

mm314of rain fell in 24hrs on thefells in Seathwaite

mm10Average daily rainfall forCumbria in November

m2.5Depth of water in Cockermouth town centre during peak

1800Bridges being inspected in Cumbria

bridges29Collapsed or closed in this area

Calva Bridge

Northside road bridge

Railway station

WORKINGTON

Calva Bridge,unstable and tobe demolished

Northside Bridge collapsed

S O L W A Y F I R T H

N

Pier

Area ofscour

Great forceapplied bywater

Scour

Fast-flowing floodwater scours away the riverbed downstream of the bridge piers, eventually destabilising the bridge foundation

Bridge near Keswick, Camerton Footbridge linking Great Clifton with Camerton and the suspen-sion footbridge over River Eamont near Dalemain – had collapsed.

“Masonry arch bridges don’t like being disturbed,” said Capita Symonds structural engineer

Kenny Brooks, who has been assessing much of the damage over the weekend. “They rely on compression and when some-thing moves, the cracking causes distress. They are strong when in place but not adaptable to move-ment. Modern bridges are more flexible. They still fail, but it’s less dramatic.”

Local authority engineers’ body CSS’s bridges group chairman Mike Winter who is also Dorset County Council’s head of engi-neering agreed that the strain on the bridges was excessive when exposed to extreme flooding.

“Bridges are designed to take

loads from above. But the water must have caused immense hori-zontal forces below,” he said.

Brooks confirmed that it was the sheer weight of the water as well as scour which caused the larger road bridges to be swept away. Debris in the flood waters helped cause the collapse of the smaller pedestrian bridges.

“With some of the footbridges, it’s the weight of the water and the debris,” said Brookes. “[It seems] the foundations are still in place, but the deck has gone. Decks have been pushed off the supports.”

Workington’s Calva Bridge on the A596, has been severely

CUMBRIA FLOODSBy Jessica Rowson & Alexandra Wynne

Structural engineers from across the UK were being rushed to Cumbria this week as the local highways authority battled to inspect 1,800 bridges following extreme floods.

Network Rail, the Highways Agency and the Royal Engi-neers have been assisting with inspections and an additional 65 engineers were expected to arrive in the area as NCE went to press.

“Capita Symonds is organising bridge checks and has redeployed some staff [from around the country],” said Cumbria County Council highways network manager John Robinson.

Capita Symonds has been working on Cumbrian highways for the last 10 years.

“Preliminary checks assess which bridges are affected and which ones aren’t,” said Robinson.

Six bridges have already collapsed and many more remain closed while urgent structural checks take place.

Most of the collapsed bridges were masonry arch bridges –some over 100 years old – in the area of Workington and Cockermouth.

Northside Road Bridge at Workington was the first to be swept away in the early hours of Saturday 21 November resulting in the death of PC Bill Barker.

By the end of Saturday five more bridges – Northside Footbridge in Workington, Lorton bridge near Cockermouth, Newlands Beck

Cumbrian bridges ripped out by torrential floodsSix bridges collapsed and 1,800 tobe inspected

ANATOMY OF WEEKEND FLOODS

“We’ve not lost too much stone at the moment but it’s still going down”Andy Dean, Connect

FLOODING

Northside Bridge, Workington Flood water tore bridges down

www.nce.co.uk | 26.11.09 NEW CIVIL ENGINEER 7

graphic: www.paulweston.info

Cockermouth R. Cocker

CUMBRIAN MOUNTAINS

Keswick

Whitehaven

Workington

Maryport

SkiddawButtermere

Loweswater

Warm moist airmakes landfall overCumbria. DepositsUK record for rainin 36 hours

EnnerdaleWater

Cockermouth

BassenthwaiteLake

R. Derwent

1 Ground alreadysaturated frompreviousrain

2

Water coming downfrom the fells in theDerwent & Cockerconverges onCockermouth & thenWorkington

3 A number of bridgescollapse and othersbecome unstabledue to shear weightof water & scouringof the foundations

4

CrummockWater

Derwent Water

mm314of rain fell in 24hrs on thefells in Seathwaite

mm10Average daily rainfall forCumbria in November

m2.5Depth of water in Cockermouth town centre during peak

1800Bridges being inspected in Cumbria

bridges29Collapsed or closed in this area

Calva Bridge

Northside road bridge

Railway station

WORKINGTON

Calva Bridge,unstable and tobe demolished

Northside Bridge collapsed

S O L W A Y F I R T H

N

Pier

Area ofscour

Great forceapplied bywater

Scour

Fast-flowing floodwater scours away the riverbed downstream of the bridge piers, eventually destabilising the bridge foundation

By Jo Stimpson

Temporary bridge specialist Mabey is in talks with Cumbria County Council to replace the 80m long condemned Calva Bridge after military solutions were deemed unsuitable.

The council has met with Mabey Bridge, Mabey Hire Serv-ices and the Royal Engineers, said Mabey Bridge UK director Alex Smale.

“We are in some discussion in terms of temporary bridges for Cumbria,” he said.

Mabey Hire Services director for bridges Chris Carter said no fixed plans for Calva were in place yet. “We are doing an early feasi-bility study for them but I believe that there are other options they

are discussing,” he said.Calva Bridge is the “first one to

look at”, he said, and the council has not yet approached the company about any other cross-ings.

“We are waiting for Cumbria [County Council] to assess all the structures and make its decision,” said Carter.

Council officials consulted

the Royal Engineers about Calva Bridge but it was decided that military solutions were unneces-sary, said a Ministry of Defence spokesman.

Ministry of Defence regional community relations officer for Cumbria and Tynedale Carol Bell said a small team of Territo-rial Army specialists were tasked with helping assess damage to Calva Bridge in the early hours of Sunday morning.

They were “asked to ascertain whether a solution using mili-tary equipment could be used to span the River Derwent”, she said. Carter said Mabey’s pre-engi-neered steel modular truss Delta Bridge and heavy duty modular design Universal bridge were most likely to be used at Calva, because they can be built quickly and are available from stock.

Cumbrian bridges ripped out by torrential floods

By Alexandra Wynne

Network Rail was this week scram-bling to build a new temporary railway station for cut-off resi-dents of flood-torn Workington in Cumbria.

It said that it intended to begin construction on Tuesday night and would construct a two platform station, linked by a foot-bridge, with lighting, a waiting room and a gravel car park.

The operator vowed to have the facility built and open by the weekend.

The town has been split in half following flood damage to the footbridges and road bridges in the area.

Aerial surveys helped to identify

possible sites before the operator settled on an area of wasteland 800m north of the existing station, off the A596 and on the north side of the River Derwent.

Network Rail then came to an agreement to lease the site from Allerdale Borough Council for two years.

“We have a wealth of experience

and engineering expertise that we felt should be put at the disposal of the Cumbrian authorities,” said Network Rail director opera-tions and customer services Robin Gisby. “Our people will work round the clock to build a tempo-rary rail station to help reconnect the town and ease people’s travel problems.”

One option for Network Rail could be to deploy an innovative new modular railway station it has been investigating and testing with Dean & Dyball Rail.

In addition, Network Rail said it was working with local operator Northern Rail to bolster serv-ices by adding carriages where possible.

The operator has also asked the council to work the station into local bus routes.

Mabey in talks to supply temporary replacement for damaged Calva Bridge

Temporary railway station for Workington

Modular: Possible station solution

Calva bridge: Condemned structure

affected by the floods. Its condi-tion is being monitored by Balfour Beatty which manages that stretch of highway as part of the Connect consortium.

“There is no doubt the integ-rity has been compromised,” said Connect general manager Andy Dean. “One of the piers of the masonry arch is sinking.

“It’s moved so significantly that it’s caused structural cracking under the arch. We’ve not lost too much stone at the moment, but it’s still going down.”

A full inspection will only be possible when water levels recede.