In the latest of a series of pieces exploring sector-specific challenges, we look at some characteristics specific to rail projects, both overground and underground.
Access to the rail network
One challenge in many rail projects is simply gaining access to the track. As a design consultancy, WCS of course doesn’t need to be on site every day, but there are reasons why we do need to attend:
- Desk research often results in partial information, with site visits needed to answer specific, identified questions
- Official sources of information can be wrong, so there is always a need to check that reality matches theory
- As well as design consultancy work, WCS personnel are often asked to take on additional roles such as Lead Civil Engineer or Temporary Works Coordinator
Railways are a dangerous place to work. All staff must complete formal training in PTS (Personal Track Safety), before attending trackside. In addition to other restrictions, the contracting party may have their own rules, so our staff can find themselves on projects where they are simply not permitted to cross the track, despite Network Rail employees crossing routinely nearby. Fundamentally, we realise these rules are there for the strongest of reasons, but it does make for a complex landscape.
Access in principle is highly formalised. Typically, we will liaise with the full-time Access Planner employed by the principal contractor, who will negotiate access for agreed, specific time slots. Each access may require isolation of an overhead line or a third rail, as well as discussion with those who manage signalling and other equipment, so there are multiple reasons why it is such a structured system. In addition to technical and safety considerations, residents and environmental restrictions can of course play a role.
This was the case with our work at Midland Mainline – Key Output 1A (KO1A). At Braybrooke ATFS, the substation modular building had to be lifted in by crane, due to site constraints. This had to be completed during a Saturday night possession of the railway. Although it went very well the costs associated with using a large crane at night with all the enabling works are significant. On another substation install on the same project, Napsbury TSC – the site access had fewer constraints and we were able to design a temporary works scheme to support a gantry lifting system to lift the substation modular building off the low loader and place straight on the foundation, without the use of a crane. This meant that the works could be carried out during the daytime, whilst the trains were still running, reducing costs and reducing the impact on the operational railway.
With us typically getting access only for limited periods, there is no easy way to ‘pop back’ if some measurement has been missed, so preparation and experience are key. WCS does specialise in rail projects, so the primary way of addressing these challenges is to ensure the supervising engineer here has great experience of such work, and then for senior WCS staff to oversee the preparation for each access, something that is always done on the basis of formal, written company procedures.
Challenges encountered underground
Quite a number of our projects are on the London Underground system. This is an environment with its own, specific difficulties, as well as those applicable to rail projects in general.
A key point to note about the underground is the density of use – the system is very crowded and very busy. Space throughout the network is always at a premium, meaning it isn’t just the platforms that are crowded – the tunnels can be quite packed with cables and other equipment.
A project to support modern trains with air conditioning, replacing older stock, may sound innocuous, but typically the new trains will require significantly more power, meaning that existing cabling and substation equipment must be entirely replaced, not augmented. Generally, there is no option of taking a line out of use, so work may need to be completed during the early hours of successive mornings, with no realistic possibility of removing old equipment and installing new in one night.
Overground, there will often be space within a substation, or adjacent, to install old and new equipment side by side. When underground, there may be a need to design and create a new temporary space, before carefully replacing old infrastructure items with new, perhaps one by one on different days. Completing a cable route can often involve overhead or under-track crossings, simply to reach a less congested section of wall, with a single under-track duct requiring digging, laying down, and then backfill and reinstatement of the track, in plenty of time for first morning use of the line.
The land above the London Underground system is at a premium too, of course. Stations on the new Elizabeth Line (Crossrail) have been designed with much heavier foundations than apparently necessary, since the right to build something additional above the stations will always be sold.
In other parts of London, accessways may be squeezed in amongst other buildings. One WCS engineer relates the story of attending a site near the Bank of Canada, in the City of London. On the street above, he was astonished to see a davit crane swing out from behind a large bank logo, this and a pavement trapdoor being the only way to move equipment in or out of the area below.
Whatever the specific challenges of each new project, we at WCS know we have a wealth of rail experience, and stand ready to tackle the next task with confidence.