All railway assets have to be managed so the risk of failure and hazards arising are as As Low As Reasonably Practicable (ALARP). ALARP involves balancing the reduction in risk against the time and cost of achieving the risk reduction. This is the point at which the time, trouble, difficulty, and cost of further measures become unreasonably disproportionate to the additional risk reduction.
Mining features underlie approximately 29% of the railway network in Britain, which includes significant lengths of both the East Coast and West Coast Main Lines. As such, whenever construction takes place on any railway, for example new structures for electrification, the risk from existing infrastructure, such historic mining features, must be managed safely and efficiently to ensure the construction project provides value for money. There are several ways mining risk is managed during construction projects, and it is something which can be very time consuming and expensive.
The North West and Central region of Network Rail is introducing a Guidance Note (GN), ‘NW&C Guidance Note for Electrification in Mining Risk Areas & Associated Civils’, which will provide a more consistent and effective approach to managing mining risk during electrification projects. By adopting ALARP principles which are embedded in the GN, projects have the potential to reduce the cost and time to install new assets associated with electrification, while managing the risks arising from mining.
Naturally, with rail being one of the safest modes of transport, everyone wants to construct a safe railway, but rail needs to be an affordable option for travellers and freight operators, otherwise customers will use other modes of transport which are not as inherently safe or carbon friendly. So overengineering rail assets can result in increasing the overall societal risk of transport. This is why cost must always be a factor in managing safety and is a fundamental of ALARP.
The Construction (Design and Management) Regulations 2015 (CDM 2015) also recognise ALARP. CDM 2015 says that the principal designer must, as far as reasonably practicable, ensure that the design team eliminates the risks associated with design elements. If this is not possible (for instance because of disproportionate costs) then the remaining risks must be reduced or controlled. This is also one of the founding principles behind the management of mining risk for electrification projects set out within the GN.
Early collaboration
Gerry Manley, director CIL Geotechnics, and a very experienced railway geotechnical engineer has prepared the mining GN, with input from a wide range of Network Rail engineers including Mark Banham, programme engineering manager Capital Delivery NW Enhancements. Importantly it has also been subject to a comprehensive and challenging peer review by a group of very well-respected independent industry experts, made up of: Professor Andrew McNaughton; Ady Koe, chief geotechnical Engineer AtkinsRéalis; Chris Milne, senior engineering manager, J Murphy & Sons; and Tim Young, SPL Powerlines UK. It took a year to produce the GN and obtain cross industry support, but Gerry and all involved with its production welcome any feedback and further opportunities to develop additional efficiencies.
The GN encourages collaboration of all stakeholders at the very early stages of a project with a mining risk, so that all stakeholders are consulted and agree that existing and any future residual mining risk can be managed as ‘Business as Usual’ (BAU). This will be supported by a project Mining Risk Assessment (MRA) and Mining Risk Mitigation Remit (MRMR). Early, and continued, collaboration is important, as any change in a project could adversely affect cost and timescales.
In line with NR/L2/CIV/191 Mining Manual, the MRA and MRMR are used to establish a consistent, mature approach on the process and application of relevant standards. The GN reminds everyone that the MRA must consider all relevant mining records and an assessment of the existing mining risks, as well as any changes in risk as a result of the proposed works.
The MRMR will take into account all the locations and work types highlighted within the MRA. All decisions to deal with mining issues must be justified and deliver the agreed outcomes specified by the client, and deliver the best balance between residual risk and cost. The GN also encourages the use of the Mining Risk Ranking System (MRRS), which is an existing Excel-based tool developed specifically for risk-ranking existing known mining hazards that may have an adverse impact on the railway.
Safety consequences
A Common Consequence Tool (CCT) is available to estimate the potential safety consequences (fatalities and injuries to train occupants) arising from a train derailment, independent of the cause of derailment, ranging from 1 (lowest consequence) to 20 (highest consequence). This can be used to consider the impact of projects and to identify any grossly disproportionate safety measure costs. A Decision Support Tool (DST) is an Excel spreadsheet to deliver the outputs of the MRRS to assist in prioritising the investigation and mitigation of mining hazards.
Explicit Risk Estimation (ERE) is a process to assess the risk associated with a given mining hazard, taking into account the likelihood and the severity of the resulting accident, with the risk expressed in Fatalities and Weighted Injuries (FWI) per year. This can be used to identify any grossly disproportionate costs for additional safe measures to mitigate any future mining features failure.
The scope and application of GN was developed for electrification projects carried out under Network Rail’s permitted development rights in the North West & Central region. These include typical works such as: overhead line stanchion foundations; signal foundations; bridge works – re-decking, jacking, and parapet raising; track works; platform refurbishment/extensions; temporary works, compounds, access roads, crane and working platforms; light weight structures such as – undertrack crossings (UTXs), drainage, ducting, equipment locations, ancillary civils bases; and retaining walls. However, the principles of GN have the potential to apply to many other projects and throughout Network Rail.
Summary
The GN is a very welcome initiative to provide a more consistent ALARP and effective approach to managing mining risk during electrification projects, which will hopefully be adopted nationally. It clarifies the process to identify mining risk to the safe operational railway and to avoid grossly disproportionate mitigation costs. The GN does this by requiring early stakeholder engagement with agreement on responsibilities. It promotes the identification of construction and loading risks, and their reasonable mitigation, and encourages best practice management of mining risk during construction.
The GN will encourage all parties to consistently work together to create less uncertainty, better supply chain relations, and reduce consultancy and construction costs. This should increase confidence in programme delivery for the benefit of everyone.
Well done to all involved in producing the GN and providing a mature approach to the management of mining risk when delivering electrification projects.
