The 18-mile long Aberdeenshire canal, from Aberdeen docks to Inverurie, opened in 1805. It was not a commercial success, so its shareholders were glad to sell their canal to the Great North of Scotland Railway (GNSR) who wanted to build their planned railway on top of it.

In 1854, the GNSR opened its first railway between their Kittybrewster terminus in Aberdeen and Huntly, extending it to Keith in 1856. Two years later, the Inverness and Aberdeen Junction Railway reached Keith, thereby completing the railway between Inverness and Aberdeen.

A further extension, also built on top of the canal, enabled the GNSR to open a new terminus in 1856 at Waterloo, close to Aberdeen’s docks. This became a goods terminus in 1867 after a 1.5-mile line was built through tunnels under the city centre to connect Kittybrewster to Scottish North Eastern Railway’s line from the South. A jointly run city-centre station was also built at the time.

The GNSR gradually doubled its single-track line between Aberdeen and Keith from the 1880s. Of the 20 original stations, 16 were closed by the 1960s. In 1968, the line was singled. The following year the discovery of the Montrose oil field heralded Aberdeen’s oil boom. Although Dyce station, adjacent to Aberdeen airport, re-opened in 1983, the single track north of Aberdeen constrained significant train service improvements.

In the project office, interactive planning sessions use Post-it notes on a large chart.

In the project office, interactive planning sessions use Post-it notes on a large chart.

Redoubling out of Aberdeen

As reported in issue 158 (December 2017), the Aberdeen to Inverness improvement project (A2I) aims to add capacity for commuter services into each city as well as supporting longer-term improvements. Last year’s completion of the new Forres station, as well as signalling enhancements at Elgin, will improve commuter services into Inverness. This was the first part of phase one of the A2I project.

To complete phase one, A2I is now working to improve local train services at the other end of the line to enable the frequency of trains between Aberdeen and Inverurie to be increased from one to two an hour. To do this, 16 miles of track is being redoubled from just beyond the city centre tunnels (1,500 yards) to the loop at Inverurie station (16 miles 1,580 yards), taking in the existing loop at Dyce station (6 miles 242 yards to 7 miles 106 yards). A turnback facility is also to be installed beyond Inverurie station extending to 17 miles 1,100 yards. Distances quoted in this article are those from Aberdeen station.

In the fifty years since the track was singled, it has been given a racing line, numerous assets have been placed adjacent to it and some underbridges only have a single-track deck. Moreover, the original earthworks cannot accommodate a double track in accordance with current standards.

Redoubling this 16-mile corridor therefore requires the virtual reconstruction of the railway corridor, for which a blockade is the only option. This was assessed as six months work. As it was considered unacceptable to close the railway for this time, it was decided that it would be done in two summer blockades, each of about three months, with the loop at Dyce enabling the redoubling to be split into two parts.

Hence, this year saw the line from Aberdeen to Dyce close from 12 May until 19 August for its redoubling. When it reopened, passengers could see the new adjacent line but could not travel on it. Trains will only use this line once it is part of a complete new double-track section between Aberdeen and Inverurie at the end of the 2019 blockade. A 30-minute service should then be introduced in the December 2019 timetable.

Moved from Forres to Inverurie

Rail Engineer visited the redoubling works during week 11 of the 14-week blockade and had an opportunity to meet its programme manager, Colin MacDonald, at BAM Nuttall’s large project office and compound at Inverurie. As Colin explained, much of this compound has been used for the recently completed Forres work, including its 50-bed ‘Hotel BAM’ to accommodate some of the workforce.

Building this temporary accommodation block was one way of addressing some of the issues associated with the project, as it is a three-hour journey from Scotland’s central belt where many of the project personnel are based. For example, as well as overseeing the work on site, the Network Rail project team must liaise with engineers, designers, operational planners and others based in Glasgow.

Network Rail has engaged two contractors for the current A2I work: Siemens for the signalling and telecommunications work and BAM Nuttall for everything else. BAM Nuttall’s main sub-contractors are AECOM and Jacobs for design, Babcock for track work and Stobart Rail for ancillary civil engineering work.

Colin advised that the blockade could be broadly split up into eight weeks of civil engineering work, four weeks of track work and two weeks of signalling. A maximum of 400 personnel per day worked on the blockade. Once the track was all in place, about 60 were on site.

One advantage of blockade working is that noisy activities can be scheduled during the daytime, as can access at sensitive areas. With some minor exceptions, no work was done between 02:00 and 06:00, when plant was refuelled.

From Dyce to Kittybrewster

After a site briefing, project engineer (track) Mark Taylor was the guide for a four-mile inspection of the work at Dyce. At the time, the new Up line was connected to the old Down line immediately south of the Dyce loop points (6 miles 70 yards) by a set of temporary points, which are to be removed at the end of the blockade.

Mark explained that the project has to address the requirements of the Railways (interoperability) Regulations. In doing so, as much as possible of the existing Down line was retained whilst the Up line is entirely new. Hence, subject to their condition, it was possible to re-use some of the Down line’s existing F27 sleepers. To take account of further track renewals, the reused sleepers were grouped together at one location on the re-laid Down line.

About a quarter of the ballast was reused after it had been regraded, washed and screened at the site of an old papermill near Inverurie. Ballast and sleepers were stockpiled at the Raith’s Farm freight terminal, which is connected to the Dyce loop.

Mark advised that staging the track work was highly complex. Amongst other things, this had to consider the requirement to move the existing track, the new long welded rails that had previously been delivered to the site, reusing sleepers at one location, interface with civils work and the need to provide a track to deliver materials. Track relaying was done with a FLASS machine provided by McCulloch Rail, which aligns and spaces sleepers to eliminate the need for manual handling.

Heading towards Aberdeen, underbridge UB40 over Fairburn Road (5 miles 1,590 yards) is one of five that needed structural work to accommodate two tracks. UB40 required new cills and separate Up and Down steel spans and ballast retention units. UB20 and UB22 required re-decking, UB24 was infilled and UB34 required an extension to its concrete deck, which was done during a weekend disruptive possession immediately prior to the blockade. Four other underbridges required parapet alterations.

At the Market Street overbridge (OB38 at 5 miles 170 yards), various types of slope stabilisation could be seen. Immediately north of the bridge, the Up side slope had been regraded using high-friction materials and the Down side slope had soil nails. Beyond this, bridge retention was by interlocking pre-cast concrete blocks and king post retaining walls. These use H piles driven to pre-determined depths into the ground with timbers inserted between the webs of the H section.

Further slope regrading was evident on the embankment south of Stoneywood Road, where high-friction fill had also been used. The project had no powers to acquire land, so the design of such slopes is derived from a risk assessment with the intention of minimising the railway’s footprint. Soon after this, the A2I project has increased this footprint by purchasing an 18 metres long strip of Council land, two metres wide, to ensure signal sighting and provide space for a signalling location case.

Passing signal DY7205 (3 miles 853 yards), Colin explained that the project has an unusual signal-sighting problem as the new Up line will not be used by trains until the end of the 2019 blockade. Until then, what will become the Down line remains as the single bi-directional Up/Down line.

This means that, until the 2019 blockade commissioning, some signals for trains in the Up direction will have to be relocated as temporary signals to the right of the single line as the new Up line prevents them being located on the left. These temporary signals will have to be replaced by new permanent signals to the conventional left of the new Up line when this is commissioned in 2019.

UB40 - removal of steel span. Photo: Peter Devlin.

UB40 – removal of steel span. Photo: Peter Devlin.

Filling in the canal

The new deck on UB22 (2 miles 1440 yards) required the temporary infill of a gulley to position the crane. Unfortunately, this is a scheduled ancient monument as it was part of the old canal that didn’t have the railway on top of it. As a result, Historic Environment Scotland (HES) objected to the planning application for this temporary access. Following consultation with HES, the original application was withdrawn and a revised one submitted. This committed the project to an archaeological written scheme of investigation that had to be approved by the Council prior to any infill work. Due to the resultant delay, it was not possible to re-deck UB22 during the weekend disruptive possession prior to the blockade as originally planned.

This planning application was one of many planning and consent issues that had to be managed by the project team in consultation with numerous stakeholders. This highlights the volume of consents work that is required for major works of this nature.

The possession limit board was at the Hayton Road pedestrian access point (2 miles 186 yards), adjacent to a re-sited GSM-R mast and UB18 on which new bridge waybeams had been installed, despite this being a mile from the start of the blockade. This was because it was a Wednesday, when a mile of the blockade had to be handed back each week to enable a freight train to access the Waterloo branch under pilotman working at 20 mph.

Four types of slope stabilisation - king post retaining wall, interlocking blocks, soil nailing and high-friction materials. Photo: Peter Devlin.

Four types of slope stabilisation – king post retaining wall, interlocking blocks, soil nailing and high-friction materials. Photo: Peter Devlin.

From Dyce to Inverurie

Next year’s Dyce to Inverurie blockade requires nearly ten miles of new track, almost twice as much as this year’s blockade. This section of the line is largely through farmland, whereas this year’s blockade was through an urban area. To ensure all the work can be completed within this blockade, as much as possible will be done beforehand including devegetation, access works, earthworks, drainage, advance structures works and signalling ancillary civils works. Before the blockade, there will be two weekend disruptive possessions for bridge and other civil engineering work.

One civil engineering challenge is reinstating the Up line on the five-span River Don viaduct (15 miles 1300 yards). This is a combination of superstructure and substructure strengthening works that may require in-river work, which can only be carried out at certain times of the year and could be a significant programme constraint.

Colin expects that the 2019 blockade will start off by completing any remaining civil engineering corridor works, followed by around eight weeks of track work and four weeks of signalling. With the commissioning of the entire new double track and transfer of its control to the Highland workstation at Inverness, this next blockade will also have more signalling work, to include the abolition of Dyce and Inverurie signal boxes together with the provision of a fringe train describer and NX panel alterations at the Aberdeen signalling centre.

In addition, the Inverurie to Insch single line is to be converted from Scottish Region Tokenless block to Track Circuit block with fringe working at Insch to the Highland workstation. Once commissioned, this workstation, which now controls Inverness to Keith, will also control the line between Inverurie and Aberdeen, with the central section of the line remaining under the control of manual signal boxes.

Being a rural area, this section of the line has three user-worked crossings that will be upgraded when the line is doubled. One, at Kirkton of Kinellar, will be provided with both miniature stoplights and power-operated sliding gates. The automatic half barrier (AHB) crossing at Boat of Kintore is also to be upgraded to a manually controlled barrier with obstacle detector (MCB-OD). This will have stopping and non-stopping controls for the future provision of Kintore station.

This proposed new station will have a 166-space car park and be built immediately north of Kintore off the main A96 dual carriageway road on land that is being compulsorily purchased. Its estimated cost is £12 million. The Scottish Government is to provide sixty per cent of this cost with the remainder being provided by the station’s promoters, Aberdeenshire Council and the North East Regional Transport Partnership (NESTRANS). It is expected to open by May 2020 latest, although possibly sooner. Although this station is not part of the A2I project, it is likely some of it will be built during the 2019 blockade.

ScotRail Alliance managing director Alex Hynes helps clip one of the last rails into place. Photo: Peter Devlin.

ScotRail Alliance managing director Alex Hynes helps clip one of the last rails into place. Photo: Peter Devlin.

From Keith to Inverurie

The 108-mile railway journey between Aberdeen and Inverness currently takes around two hours 25 minutes, with an irregular service that is roughly two hourly. The Scottish Government’s long-term aspiration is to deliver a two-hour journey time with an hourly service by 2030.

Achieving this will require the development of A2I phase two, which has yet to be funded. It is likely that this will focus on the route’s central section between Keith and Inverurie. This will probably provide more efficient loop operation and resignalling to remove the remaining mechanical boxes to give the Highland workstation control of the entire line between Inverness and Aberdeen.

Before then, at a cost of £330 million, phase one of the A2I project will, in 2019, deliver the Government’s immediate objective of enhanced commuter services into each city and make use of the 2018 blockade’s double-tracking.

The statistics for this year’s blockade are impressive – 76,000 tonnes of earthworks spoil, 65,000 tonnes of ballast, 19,000 sleepers, 45 miles of new cable in 5.5 miles of new troughing, six miles of new rail and 2.5 miles of new drainage. However, perhaps more impressive is the management, planning and logistics that delivered all of this activity in a constrained corridor with limited access.


Read more: Mark Carne looks back on his time at Network Rail