TfL report warned of Hammersmith Flyover collapse risk

Hammersmith Flyover is used by 90,000 vehicles a day

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A major London road remained open for weeks after a report warned of a small risk it could collapse at any moment.

Hammersmith Flyover, used by 90,000 vehicles a day, was shut on 23 December 2011 as salt water from gritting had rotted internal steel cables.

But a draft report obtained by BBC London showed months earlier Transport for London (TfL) knew it could have seen a "sudden catastrophic collapse".

TfL said monitoring suggested a "number of years of life" left in the bridge.

The Emergency Preparedness Plan, which was written on 29 October 2011, was obtained through a Freedom of Information request.

It also detailed how TfL would respond to a collapse, outlining co-operation with emergency services, an exclusion zone, debris removal and PR strategy.

'Remote possibility'

The report reads: "The immediate plans are to install some form of temporary structure beneath the flyover, to strengthen it and prevent the likelihood of a sudden collapse, however remote the possibility.

"It is likely to be 3‐4 months before construction can commence.

"Until this structure is in place there is a very remote possibility that Hammersmith Flyover will collapse."

Strengthening work taking place The flyover was damaged by salt water

Not only does the high structure carry heavy traffic, but roads and pedestrians pass underneath.

John Knapton, a highway engineer and concrete expert, said: "The report was saying if the bridge collapsed it would do so without any warning whatsoever - and would be more likely to do so when traffic was there, because of the weight.

"There is also the danger of things going on beneath the flyover. You would expect fatalities."

Mr Knapton, who advised the government on lessons learned from the Twin Towers collapse, argues at the very least TfL should have put in place a 7.5 tonne weight restriction.

But this was not done.

A TfL spokesman admitted a strengthening prop system only came into effect on 27 November.

That means the at-risk bridge was open to all traffic - without additional support - for more than four weeks after the collapse warning.

Mr Knapton said there have been similar "catastrophic" bridge collapses in the US and developing countries.

And Ynys-y-Gwas Bridge in south-west Wales - built to a similar design as the flyover - suddenly collapsed in 1985 after metal tendons corroded.

A motorist whose car tumbled into the river below was lucky to escape.

Bridge collapse Ynys-y-Gwas Bridge collapsed after suffering the same problem that afflicted Hammersmith Flyover

Andy Slaughter, Labour MP for Hammersmith, said: "It horrifies me. They flatly denied what now appears to be the case - that they knew there was this danger, however small, of imminent collapse.

"It is extraordinary and I'm almost lost for words - not so lost for words that I won't be taking this up with them now and asking them to completely come clean."

TfL's surface transport boss Garrett Emmerson said: "There's always a possibility of any structure collapsing, however remote, for whatever reason.

"The monitoring we undertook indicated a number of years of life in the structure, so it could carry on taking heavy goods vehicle loadings."

After inheriting the flyover in 2000, TfL began using audio equipment to monitor cable deterioration.

A spokesman said: "TfL is satisfied it took appropriate action based on the information available at the time to ensure restrictions were not applied unnecessarily."

BBC Inside Out has also obtained the most recent inspection report into all 36 TfL flyovers.

'Possible major accident'

Some 27 were considered a "medium risk", defined as: "Superficial or moderate defects or damage, capacity may be slightly or significantly affected."

Seven flyovers were in "poor" or "very poor" condition, with capacity significantly affected.

Every flyover had non-cosmetic defects, with the BBC counting 541 in all - an average of 15 each.

Restricted report The report was branded "restricted"

Common defects included severe corrosion, flooding, seepage, spalling (crumbling concrete) and exposed metal elements.

Four flyovers were deemed to be in "good" or "very good" condition.

Blackwall Lane Viaduct had the most defects, with 34.

And there were concerning comments on the A406 Flyover. The report notes: "TfL's attention is drawn to the condition of Maurer expansion joints.

"The risk of joint failure is significant and unpredictable, leading to a possible major road accident.

"This should be addressed by special investigation as a matter of urgency."

TfL refused to confirm whether this has been addressed.

Meanwhile the assessment of Westway Flyover Section 5 branded it "high risk".

That is defined as: "Severe defects, one or more elements failed, structure unserviceable, possible failure of a critical element, may need to be weight restricted or closed."

The BBC asked John Knapton to carry out a visual inspection of the flyover.

He found numerous vertical cracks with white marks along the concrete - salt that had got into the structure from gritting.

Mr Knapton said the salt was likely to be "in the bridge right now corroding the embedded steel".

There is an alternative to salt grit, a chemical called CMS. But TfL admitted this winter all but one of its flyovers will be laced with salt grit.

A spokesman insisted Hammersmith Flyover was the only structure where CMS was needed.

He said TfL has a programme of inspection and maintenance that will ensure all London's flyovers remain safe for years.

Inside Out tried to obtain reports on London flyovers controlled by the Highways Agency. But the agency refused the Freedom of Information request on cost grounds.

BBC Inside Out is on BBC One in the London region on Monday, 3 December at 19:30 GMT and nationwide on the iPlayer for seven days thereafter.

London's ageing flyovers

Flyover Date inspected Condition of critical elements Risk of critical elements Defects (non cosmetic) counted by BBC

Source: Transport for London

A124 Viaduct

10/09/2011

Good

Medium

10

Angel Road Viaduct

09/03/2012

Very good

Low

6

Barking Viaduct North Approach

11/09/2012

Fair

Medium

18

Barking Viaduct South Approach

23/09/2012

Poor

Medium

12

Blackwall Lane Viaduct

02/09/2009

Reasonable

Medium

38

Bourne Road Flyover

27/01/2011

Fair

Medium

15

Brent Cross Flyover

27/04/2012

Fair

Medium

15

Bricklayers Arms Flyover

28/01/2011

Fair

Does not say

8

Burlington Road Flyover

15/04/2011

Fair

Medium

14

Bushey Road Flyover

15/04/2011

Fair

Medium

15

Coombe Lane Flyover

21/04/2011

Poor

Medium

24

Country Way Viaduct

05/11/2010

Does not say

Medium

17

Cray Viaduct

09/10/2009

Fair

Medium

27

Crittall's Corner Flyover

28/08/2009

Fair

Medium

25

Croydon Flyover

25/07/2011

Does not say

Medium

14

Gallows Corner

14/11/2011

Poor

Medium

14

Greenford Roundabout Flyover

25/10/2011

Fair

Medium

8

Hall Lane Flyover

05/10/2010

Does not say

Medium

10

Hammersmith Flyover

26/03/2012

Poor

Medium

34

Hogarth Flyover

23/11/2011

Fair

Medium

19

Hope and Anchor Flyover

02/08/2011

Fair

Medium

1

Lea Interchange Flyover

01/09/2011

Satisfactory

Does not say

2

Marylebone Flyover

16/03/2011

Good

Medium

10

Rowley Lane Flyover

08/06/2010

Does not say

Low

24

A5 Flyunder

24/08/2011

Fair

Low

7

A406 Flyover

22/02/2012

Fair apart from joints

Does not say

20

West Cromwell Road Viaduct

11/10/2011

Poor

Medium

10

Westhorne Avenue Flyover

17/09/2009

Does not say

Medium

24

Westway Section 1

20/03/2011

Very poor

Medium

14

Westway Torquay Street

30/03/2010

Fair

Medium

17

Westway Section 4

24/09/2012

Satisfactory

Does not say

12

Westway Section 5

22/06/2012

Does not say

High

14

Westway Section 6

22/06/2012

Does not say

Medium

11

Wick Road Flyover

29/06/2011

Good

Does not say

7

Wood Lane Flyover

03/10/2011

Fair

Medium

6

Woolwich Road Viaduct

24/06/2008

Poor

Medium

22

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