CONTRACTORS IN charge of upgrading the M5 Avonmouth Bridge were fined £500,000 at Bristol Crown Court last week for breaching the 1974 Health & Safety at Work Act and ordered to pay £525,000 costs.
Senior managers at Costain and Yarm Road - formerly Kvaerner Cleveland Bridge - were called to account for long running and ultimately fatal safety lapses.
Four men plunged 25m to their deaths on 8 September 1999 (NCE 16 September 1999) when the underslung gantry from which they were working collapsed. They were replacing runway beams from which the gantry was suspended.
Judge Justice Owen said the accident had been caused by 'widespread failings of the most serious nature'.
The £500,000 fine, one of the highest awarded for an industrial accident, was designed to 'be large enough to matter to shareholders as well as to management', he added.
Costain and KCB were blamed equally for the deaths of Paul Stewart, 24, from Newcastle, Ronald Hill, 39, from Glasgow, Jeffrey Williams, 42, from Newport, and Andrew Rogers, 40, from Middlesbrough.
'Responsibility lies at high levels in both cases, ' Justice Owen said.
He blasted the defendants for allowing gantries to operate unsafely for at least seven months before the collapse.
An investigation by the Health & Safety Executive had found fault with 'every aspect of safety management'.
Prosecuting, Philip Mott QC said unsafe working practices endangered those using the gantries, as well as other workers and people on footpaths, a railway line and local roads under the bridge.
Costain and KCB failed to train workers properly, Mott said.
The four workers killed were blame free, he added. They did not know how to operate the gantry correctly.
Guidelines for operating suspended gantries were ignored.
The high risk strategy of operating a gantry suspended from beams with sections cut out was approved by senior managers, yet far safer working methods could have been adopted.
Cutting out sections of the old runway beams before the replacement beams were completed meant that beam trolleys could fall off the exposed beam ends, causing the gantry to collapse.
Operating gantries was forbidden in wind speeds greater than 48km/h, but this limit was regularly exceeded as on the day of the accident.
Wind speed monitoring equipment was broken or poorly calibrated and readings were often inaccurate.
Gantries were blown along the rails by strong gusts of wind at least five times before the accident, yet security was not improved.
A similar accident almost happened in February 1998 when one of the two wheels of a beam trolley fell off an open rail end. A memo reporting the incident was ignored.
The judgement also pointed to use of inadequate equipment.
Clamps used to brake the beam trolleys and as end stops could not be tightened enough to prevent movement of the gantries and beam trolleys under high wind load.
What went wrong
THE FOUR steelworkers flung to their deaths from a maintenance gantry suspended beneath Avonmouth Bridge's east side cantilever on 8 September 1999 were replacing a pair of I-section gantry runway beams.
They were moving the gantry when it was caught by a gust of wind and blown along the beams.
The trailing pair of beam trolleys, from which the gantry was suspended, dislodged temporary beam clamps which were meant to prevent them moving and fell through a 3.2m gap where old beam had been removed and not replaced.
Running the length of the bridge along side and central cantilevers, runway beams are welded to transverse members in the bridge's steel deck. Costain/Kvaerner Cleveland Bridge's replacement strategy involved 'working across a discontinuity' with the leading pair of trolleys running on old beams and the trailing pair on new beams, while a 3.2m section of beam was removed and replaced.
The gantry was fitted with four steel ropes controlled by tirfors - manual winches. These were designed to be hooked diagonally to cross members, enabling the gantry to be hauled along the rails.
Tirfors would also brace the gantry against uncontrolled longitudinal movement, caused by wind loading or gravity. But it was vital they were used in opposition and moved only one at a time.
An investigation by the Health & Safety Executive revealed at the time of the accident that just one tirfor had been attached, to resist gravity - the slope of the bridge was one degree off horizontal.
There were no tirfors in place to restrain the gantry against longitudinal wind loads.