SCRCA Note: A change of plan for the south end of Blea Moor Tunnel

Submitted by mark.harvey / Sat, 23/11/2019 - 19:21
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F.S. Williams' well respected (and usually extremely accurate) contemporary account of the construction of the Settle and Carlisle Railway includes the following short paragraph:

We can now see through the “spectacles” of the powerful little engine which is drawing us, that we are approaching the mouth of what may perhaps be more strictly called the "covered way" that leads to the famous Blea Moor Tunnel. It was intended to make the entrance some distance farther north; but eventually it was thought safer (in order to avoid any slipping of earth down the mountain or down the sides of the cutting, which would have been nearly 100 feet deep) to cover in the cutting, and, in effect, to commence the tunnel 400 yards farther south.

Source: "The Midland railway: its rise and progress. A narrative of modern enterprise" by Frederick Smeeton Williams, published by Strahan & Co London (1876), page 499.

If this paragraph is factually correct, it would provide us with interesting and extremely valuable information about the method used to construct the southern end of Blea Moor Tunnel and about the location of its South Portal. But is this paragraph factually correct?

The location of the South Portal

The South Portal of Blea Moor Tunnel was originally planned to be located at the site of Shaft A. This intention is supported by the fact that Shaft A marks the summit of the 'The Long Drag' (the almost continuous fifteen mile long, 1-in-100 climb up Ribblesdale from Settle Junction) and the fact that the tunnel from Shaft A northwards is dead straight. However, in the extract quoted above, F.S. Williams states that the tunnel's southern entrance was moved approximately 400 yards further south to address concerns about rockfalls and landslides. This change of location for the South Portal is fully supported by all of the currently available information.

The method used to construct the south end of the tunnel

The wording of Williams' account (as quoted above) implies that the railway between Shaft A and the South Portal was constructed using the 'cut-and-cover' technique. However, the following all combine to cast doubt on whether this really was the case:

  • the stated depth of the required cutting (up to 100 feet),
  • the course of Little Dale Beck (which crosses the railway alignment here) and
  • the general form of the present-day landscape.

The course and form of Little Dale Beck are especially thought-provoking. If the ground above the railway alignment really had been back-filled (as Williams' statement implies), it is highly likely (almost inevitable) that at least some of the water flowing along Little Dale Beck would disappear into it, then emerge in large and troublesome quantities within the tunnel itself. The Midland Railway Company expended a considerable amount of time, effort and money channelling and taming nearby Force Gill. If the 'cut-and-cover' technique really had been adopted for the southern end of the tunnel, similar arrangements would almost certainly have been needed for Little Dale Beck.

There is also at least one contemporary document that casts doubt on the 'cut-and-cover' theory. The author has seen a very poor quality reproduction of an engineer's drawing that shows the rate of progress with the tunnelling at Blea Moor. Unfortunately, the progress dates on this document are illegible and the section showing the South Portal itself has been omitted from the reproduction. However, this document does show Shaft A and it does include a depiction of the land surface on either side of Little Dale Beck. It also seems to provide 'progress information' for a short section of tunnel to the south of Shaft A and it does so in a way that suggests construction was via traditional tunnelling methods.

If traditional tunnelling methods were used for this quarter-mile long 'extension', it could also account for the two 'missing' shafts implied by the frequently cited statistics from F.S. Williams' contemporary account:

By such an arrangement, seven shafts and two tunnel entrances would give sixteen tunnel faces...[1].

If a pair of additional temporary shafts were sunk in this area (to minimise the amount of time needed for tunnelling), they would have been small in both circumference and depth. They were not needed for long-term ventilation purposes, so they would have been lined with timber initially, then in-filled and 'capped' when the tunnel's brick-arch roof was constructed. The absence of any spoil tips associated with these hypothesised shafts is easily explained as most of the spoil from this area was used to construct the enormous embankments further south. Finally the small circumference and shallow depth would give limited scope for subsequent settlement, thereby making the locations of these abandoned structures extremely difficult to spot in this rough terrain. Unfortunately, proving or disproving this hypothesis will be difficult as there is no sign of these shafts above ground and railway sources have advised that there is no sign of them within the tunnel either.

There is a second possible explanation for the origin of the shaft count of 'seven'. When building any long tunnel, the Victorian contractors would have been keen to begin work on the 'headings' as quickly as possible. In order to create a working face at the location of a tunnel portal, it is possible (and given what we know about the sinking of Shaft A, perhaps likely) that the contractor would have sunk a small temporary shaft immediately in front of the portal location so that work could begin on the 'heading' while the approach cutting was being excavated more fully. If this approach was adopted, the temporary access shaft would have been gradually enlarged sideways in three directions to form the approach cutting. Once the portal structure itself had been constructed, there would be no trace remaining of the initial access shaft. The only long-term evidence in the landscape would be a spoil heap with a clear focal point at the head of what had been the original shaft, although even this would not exist if the spoil had been removed for use elsewhere. With regards the South Portal of Blea Moor Tunnel, there is a feature in the landscape (and depicted on the 1912 land plan) that we have interpreted as a spoil tip (see Location ID 249280). If this feature really is comprised of spoil, it would support this interpretation of the working method used to gain access to the working face at the South Portal. If a similar technique had been adopted at the North Portal, this would give us the shaft count of 'seven'. However, if this explanation for the number of shafts is correct, the second part of the quote must be inaccurate.

It is possible that we will find documentary and / or physical evidence that resolves this question once and for all. However, it is also possible that the question will remain unanswered.

The photograph below shows the Blea Moor landscape directly above the line of the tunnel. It was taken from a position near, but slightly to the north of the South Portal. Little Dale Beck is clearly visible in the middle ground, meandering in a reasonably natural manner across the alignment of the tunnel. The green railing fence marks the location of Shaft A (with its spoil tip to the left). The spoil tips associated with Shaft 1 and Shaft 2 are clearly visible further up the hill, linked by the alignment of the construction era tramway. If the south portal approach cutting had been excavated to its originally planned extent, it would have run from the bottom-right of the image to the base of Shaft A. (NB: The photograph was taken using a telephoto lens, so the various structures appear to be much closer together than they are in reality.)

Photograph as per caption.
Little Dale Beck and three of the spoil tips associated with the construction of Blea Moor Tunnel.
Photo courtesy of and © John A. Harrison (2004).

Conclusions and a request for information

Conclusion 1: F.S. Williams' assertion that the position of the tunnel's South Portal was altered is fully supported by the evidence currently available to the SCRCA Project Team.

Conclusion 2: F.S. Williams' assertion that the southern end of the tunnel is a "covered way" (constructed using the cut-and-cover technique) is almost certainly incorrect.

Conclusion 3: F.S. Williams' statistics for the number of construction shafts and working faces remain uncorroborated and are still open for debate.

As with all aspects of the SCRCA Project, additional research will be carried out on this topic as and when resources permit[2]. In the meantime, if you have any plans, photographs or information that might help us to improve these notes, please get in touch via the project's dedicated 'Contact Us' form.


[1] This phrase can be seen in context in the fourth paragraph of the extract at "SCRCA Primary Reference: Review of F.S. Williams (1876) for Blea Moor Tunnel". There are five confirmed shafts associated with Blea Moor Tunnel, plus the two portals (south and north), leaving two shafts unaccounted for. The confirmed shafts are:

[2] One of the outstanding - and increasingly urgent - tasks for an SCRCA Project volunteer is a visit to the National Archives at Kew[3]. If you think you might be able to help with this task, please review the 'Getting involved' page (especially item 7), then get in touch via the project's dedicated 'Contact Us' form.

[3] The National Archives at Kew houses a wealth of primary reference material relating to the construction and operation of the Settle and Carlisle Railway, including records of the Parliamentary process, minutes of the Midland Railway Company's Construction Committee and plans of the bridges and stations. Unfortunately, these records are not available online. However, links for some of the potentially relevant catalogue entries are provided on the Reference Sources page.


Text by Mark R. Harvey (© Mark R. Harvey, 2019). Photo by John A Harrison. Supporting information kindly supplied by Nigel J. Mussett and Tony Freschini.