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Let the drain take the strain, argues ORR inspector of railways

Chris Davies, principal inspector of railways at the ORR, debates the often-overlooked importance of drainage in the safe operation of the railway network.

In February 1940, a passenger train on the approach to Watford tunnel struck a landslip containing 800 tonnes of earth then derailed. The impact was such that two carriages were telescoped together and seats thrown through the roof.

One passenger – perhaps unsurprisingly during wartime – thought the train had been struck by a bomb. As a result of the impact, a passenger – a woman on her way home from a wedding – was killed, and several more passengers and members of the crew were injured.

A contributory factor to the landslip was the lack of drainage to move water away from the vulnerable earthwork.

We can be confident of this because, as part of the repair work carried out after the incident, plans were drawn up to install a drainage system to reduce the risk of further failures. Job done, yes?  Well, no. 

Wind the clock forward 76 years. On Friday 16 September 2016, a passenger train heading towards London struck a landslip at virtually the same location. The train derailed but carried on travelling into the tunnel where, seconds later, it was struck a glancing blow by a train travelling in the opposite direction.

A combination of quick action by the drivers and, if we’re honest, luck was all that prevented a head-on collision which could have had catastrophic consequences. As it was, the passengers and crew escaped serious injury.

The Watford derailment in 2016 is a graphic, but unfortunately not isolated, example of what can happen to earthworks that are saturated with water.

A simple way of reducing this risk is to install and maintain a suitable drainage system to move the water somewhere else. That is exactly what is done at many locations.

But, nearly three years on from Watford, there are earthworks at tunnel portals still awaiting review to check that adequate drainage is in place.

More broadly, there is more work to be done to identify the location of all drainage assets on the network.

That is despite the completion of the Integrated Drainage Project (IDP) five years ago, which was intended to have achieved that goal.

Approximately 10 years ago, the Office of Rail and Road (ORR) had gathered evidence of Network Rail’s poor state of understanding of its drainage assets, and consequently sought the progress of the IDP.

Drainage at that time was to an extent a ‘Cinderella’ asset group – largely ignored in favour of other assets with a more immediate claim for attention.

Nevertheless, the IDP progressed and, by 2014, had acquired evidence of a large number of newly-identified drainage assets.

Job done perhaps? Well, as we have seen at Watford tunnel, not necessarily. Fast forward to 2019 and we are still in a situation where Network Rail’s drainage asset knowledge is incomplete.

Our focus over the past three or four years has been on drainage assets in high risk earthworks. That means earthworks that are in such a location or condition that, should they fail, there is a higher than usual likelihood of a catastrophic incident.

So, we issued an Improvement Notice in 2015, requiring Network Rail to identify critical drainage assets in those earthworks and put in place plans for making sure that they are working effectively. Network Rail complied with that Notice in 2016.

And now we are revisiting that topic. In 2019-20 we have decided to focus on the adequacy of drainage at high risk soil cuttings and tunnel portals as the focus of a nation-wide inspection programme.

We want to check that those critical drainage assets are being maintained as promised. Because, if they are not, then the potential for a serious incident increases.

In the event that the drainage management plans drawn up to comply with the Improvement Notice are not being implemented fully, we will expect Network Rail to take action to rectify those failings.

Our work is also expanding to take in the identification and maintenance of culverts. An incident last year at Thorrington, Essex, demonstrated that Network Rail – in at least one route – did not have a full understanding of the location, condition and functionality of the culverts that form a key part of its drainage systems.

That needs to change – there is no point installing effective drainage channels if water is merely diverted to a blocked culvert.

Drainage is not a topic that gets the heart racing. Nonetheless, proper understanding and maintenance of drainage assets is of fundamental, underpinning importance to the safe operation of the railway network.

And that is why ORR continues to focus its resources on helping Network Rail to get this right.

Because provision of effective drainage systems must be a key component in our ongoing work to keep rail travel as safe as possible for everyone.

Read the full piece in our June/July edition of RTM.

(Pictures: Chris Ison/Steve Parsons/PA Images)