A train derailment that killed three people could have been avoided if a drain had been built correctly, an inquiry has found.

Train 1T08 left the tracks near Stonehaven, Aberdeenshire, on 12 August 2020, after hitting debris that heavy rain had washed onto the line from the drain.

Train driver Brett McCullough, 45, conductor Donald Dinnie, 58, and passenger Christopher Stuchbury, 62, all died from blunt force injuries, while the other six passengers were injured.

A fatal accident inquiry was held earlier this year, and Sheriff Lesley Johnson issued her determination on Wednesday.

She found that the derailment could have been avoided if construction firm Carillion had built the drain in accordance with the design it had been given.

The drain went up in two phases, in 2011 and 2012, and she said it had deviated from the design in “a number of respects”.

The sheriff also said that Network Rail had “failed to ensure” the drain was constructed properly and in line with the drawings.

She said Carillion had failed to prepare “as built” drawings of the finished drain and provide them to Network Rail.

Network Rail, she said, had failed to ensure it was “in receipt” of these.

The determination read: “The drain was not constructed/installed in accordance with the design.

“As a result, the drain was unable to accommodate the flow of surface water during the intense rainfall in the area on August 12 2020.”

Train 1T08 had set out from Aberdeen at 6.38am bound for Glasgow, and had passed the crash site when it was halted for more than two hours because of a landslip further down the line.

The train was authorised to return to Stonehaven around 9.28am, and it struck the “washout” from the drain around 9.37am.

The determination explained: “When the train collided with the washout, it was travelling at around 73mph, just below the normal speed for the line concerned as instructed by the signaller and in accordance with the railway rulebook.

“The collision caused the train to derail and deviate to the left, before striking the parapet of bridge 325 (over Carron water), causing the train vehicles to scatter.”

A criminal prosecution arising from the crash saw Network Rail fined £6.7 million in 2023 after it admitted health and safety failings.

Carillion went into compulsory liquidation in January 2018.

Sheriff Johnson closed her 199-page determination by paying tribute to those directly affected by the crash.

“An inquiry of this kind is focussed upon the individuals who lost their lives in the accident, and establishing the matters set out in section 26 of the Act.

“However, I am mindful of the six individuals who survived the derailment, and whose statements formed a crucially important part of the evidence to this inquiry.”

She added: “Finally, I wish to join all the participants in this inquiry in expressing my sincere condolences to the families and friends of Christopher Stuchbury, Donald Dinnie and Brett McCullough for the tragic and untimely loss of their loved ones.”

She made no recommendations, saying the Rail Accident Investigation Branch (RAIB) previously made 20 recommendations to the railway industry following its “detailed and thorough investigation” into the incident.

She noted that the “vast majority” of these have already been implemented, and that the remaining ones are being “actively progressed”.

Liam Sumpter, Network Rail Scotland managing director, said: “The tragedy at Carmont was a terrible day for our railway and our thoughts remain with the families and loved ones of Brett McCullough, Donald Dinnie, and Christopher Stuchbury, along with all those affected by the derailment.

“Since August 2020, we have been working hard to make our railway safer for our passengers and colleagues, to deliver on the RAIB recommendations and to fully support the FAI process to reach its conclusion.

“We have made significant changes to how we manage the risk of severe weather since the accident and to increase the resilience of Scotland’s railway.”

David Ross, ScotRail chief operating officer, said: “Nobody at ScotRail will ever forget the accident at Carmont, and the tragic loss of Brett McCullough, Donald Dinnie, and Christopher Stuchbury.

“The families and loved ones of all those who have been affected continue to be in our thoughts and prayers.

“The safety of our customers and staff is our priority, and we only operate trains that meet the stringent safety requirements expected of our fleet.”

Laura Buchan, legal director with the Crown Office, said: “Our thoughts remain with the families, friends and colleagues of Christopher Stuchbury, Donald Dinnie and Brett McCullough and everyone affected by this tragedy.

“This inquiry provided a detailed public examination of the circumstances that led to the derailment and the factors that contributed to it.

“The sheriff found that important changes have been made across the rail industry since the derailment and concluded that these measures have addressed the safety issues identified during the inquiry.”

A spokesperson for the national union of Rail, Maritime, and Transport Workers (RMT), said: “RMT was fully involved in the working group set up following the tragic derailment at Carmont which cost the lives of three people and led to serious injury to others.

“RMT general secretary Eddie Dempsey said that the union supported every recommendation which helps make the railway a safer place particularly around drainage, earthworks and weather forecasting.

“We also support the removal of the ancient intercity fleet of rolling stock involved in this crash as it is clearly not up to modern standards.”

Aslef Scottish organiser Kevin Lindsay said: “Our main thoughts today are with the families of Christopher Stuchbury, Donald Dinnie and train driver Brett McCullough who all died following the derailment of the 06:38 Aberdeen to Glasgow service on the line between Dundee and Aberdeen near Carmont, Aberdeenshire on August 12 2020.

“The pain they feel is always with them, and we know the publication of the FAI determination will only add to their grief and sense of loss.

“We have consistently said throughout this process that this tragedy should never have happened.

“The failings of Network Rail and their contractor Carillion, identified by the RAIB report and supported by the FAI determination, represent a staggering level of governance and corporate failure that must never happen again.”