On March 10 the Rail Accident Investigation Branch (RAIB) published its report 02/2022 into the accident that occurred at around 09:37 on the morning of Wednesday 12 August 2020, when a passenger train derailed at Carmont in Aberdeenshire resulting in three fatalities. A briefing for the media took place in Aberdeen on 10 March with Simon French, RAIB’s chief inspector making a presentation and answering questions.
The 20 recommendations indicate that radical action is needed by most of the organisations involved and hopefully this will be stimulated by the actions of the Office of Rail and Road (ORR), Procurator Fiscal so that the Great British Railway (GBR) organisation is more successful.
The wording of the preface to RAIB’s reports is especially relevant. It states that: “It is inappropriate that RAIB should be used to assign fault or blame or liability, since neither the investigation nor the reporting process has been undertaken for that purpose. RAIB’s findings are based on its own evaluation of the evidence that was available at the time of the investigation and are intended to explain what happened and why, in a fair and unbiased manner.” Other investigations by Police Scotland with British Transport Police and the ORR will be of interest to the Procreator Fiscal in Aberdeen.
Not constructed as designed
RAIB’s investigation found that the accident was caused by a French drain and the ground immediately surrounding it; installed in 2011/12 as part of a scheme to address earthwork stability problems. The drain was a 450mm diameter perforated pipe with a gravel filled trench. It ran for 306 metres alongside a field edge at the top of the slope and then downwards at a one in three gradient for 53 metres to track level. Catch pits were sited at intervals for inspection and maintenance.
On 12 August 2020, two inches of rain fell between 05:50 and 09:00, a one in a hundred-year frequency event. RAIB’s report states bluntly that “the drainage system was not installed according to the design drawings”. A low artificial ridge or bund was constructed which concentrated the water flow into a short length of gravel filled trench. Consequently gravel, and stony material was washed out. The drainage pipe trench was filled with 20-40 mm gravel and “its use in such a steeply sloping trench increased the likelihood of it being washed away.”
Aecom (appointed by RAIB) advised that the drainage system as designed would have safely accommodated the water flow on the morning of 12 August. But Carillion did not construct it in accordance with the design. The most significant difference was the bund which was built outside Network Rail’s land and diverted water into a gully, increasing the likelihood of a gravel fill washout. No evidence was found of Network Rail being notified of this bund’s construction.
Unnotified design changes
Additionally, RAIB uncovered other differences between the designs and the drainage system that was installed including: Pre 2010 drainage not connected into 2011/12 drainage at catchpit 18; catchpit 18 being relocated; lack of textile lining to drainage trench (used to prevent fines clogging up the drain in the area of the washout); holes cut in catchpit sides significantly larger than entering pipes; and a pipe bend not coinciding with a catchpit just a metre downslope of catchpit 18. No evidence was found of any of these changes being referred to the designer.
Arup was the designer and Carillion was responsible for delivering the works as designed. Any changes should have been notified to Arup but none of them were. The report says that Network Rail’s project team was probably unaware that the 2010/11 drain differed significantly from the design and were not required to check it by Network Rail’s business processes.
Seven years but no inspections
As built drawings were a requirement, but the RAIB investigators found no evidence of their being provided. They are used to assist with future maintenance and are required by the Construction (Design and Maintenance) Regulations 2007. RAIB sample-checked 64 projects and discovered that “more than half of them were missing any trace of a Health and Safety file”. Of 11 sampled drainage projects, five were not transferred into the Network Rail asset management system.
In December 2012 the adjacent landowner visited the sloping drainage system and took a picture of the steeply sloping drain uphill of catchpit 18. This showed slight erosion to the drain’s gravel surface. Copies were passed to both Carillion and Network Rail.
Network Rail’s Ellipse system holds drainage information and is used for inspections and maintenance, but when the work at Carmont ended no entry was made into Ellipse. Consequently, no inspection regime was established for the upper section of drainage and RAIB found no evidence of any inspections between March 2013 and August 2020.
12 August 2020
At 09:00 there was flooding and a landslip at Ironies Bridge, flooding at Newtonhill (north of Carmont) and another landslip near Laurencekirk Station to the south, but no instruction was given to the driver or signaller for either reduced speed running or for the line to be examined. RAIB found that the controllers had not been given sufficient guidance or training. It questions whether Network Rail “appreciated the risk from very heavy rainfall to earthworks and associated drainage” and whether its management realised that risk mitigation measures had not been effectively implemented in Route Control.
The report states that “despite awareness of risk Network Rail has not completed implementation of additional control measures following previous events involving extreme weather; they still have to complete actions to enhance the capability of operating staff to manage complex incidents.”
RAIB’s “causal factors” are summarised as: (i) the gravel in the drainage trench was vulnerable to washout if large flows of surface water concentrated into a short length of drain; and (ii) Carillion did not construct the drain in accordance with the designer’s requirements.
As a consequence of this accident, RAIB has made 20 recommendations for the improvement of railway safety to the ORR, requiring them to consider each one and where appropriate take action and report back to the RAIB.
The areas covered include: (i) better management of civil engineering construction activities by Network Rail and its contractors; (ii) additional standards and guidance on the safe design of drainage systems; (iii) improved operational response to extreme rainfall events; (iv) enhancing the capability of route control offices to effectively manage complex events; and (v) measures to prevent derailed trains from deviating too far from the track.
The full report and all 20 recommendations can be found at: https://www.gov.uk/government/news/report-022022-derailment-of-a-passenger-train-at-carmont.
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