In the Spring 1999 issue of Cuttings a print of the Sankey Viaduct was reproduced in the centre pages. It dated from the 1850’s, but the picture varied from other prints from around the Railway’s 1830 opening in that it showed the western approach to the stone viaduct as consisting of open wooden trellis-work. The question was posed - could anyone explain this? Using information in RHH Thomas’ book "The Liverpool and Manchester Railway", Peter Keen advances the following explanation:

In order to maintain minimum gradients, the railway builders, like their canal counterparts, would use the spoil from cuttings in the construction of embankments. The Railway was effectively split into Western and Eastern sections by the Sankey Valley, so that bulk material could not cross the valley until very late in the construction period. Spoil for the viaduct’s western approach could therefore only come from the west, but the matching of embankment and excavation does not always balance out.

In the far west the excavation of Wapping Tunnel yielded large quantities of material which was carefully graded, with the larger stones going as sleeper blocks and other railway uses, whilst the small stone and rubble went to levelling up building sites in the expanding town of Liverpool. Clay deposits went to the brickworks at Edge Hill, then back as bricks to line the tunnel.

Further excavations took place at Edge Hill, where a deep cutting was required to cater for the running rails and the stationary engine and its winding gear, needed to raise and lower the trains between there and Crown Street Station. Again, the good stone was used elsewhere, and the rubble went into the Roby embankment once the Olive Mount Cutting was opened.

Olive Mount Cutting, made through solid rock, was nearly a mile long, 70’ deep, and initially 20’ wide. It produced large amounts of material, much of which was far too valuable to use as rubble, and was used at the rate of 500 cubic feet per week in the construction of Liverpool Docks. Smaller stones and rubble were used in building the western end of the Roby embankment, with the eastern end being made up of spoil from the Huyton Cutting.

The next devourer of spoil was the embankment across Parr Moss. Although not on the same scale as the notorious Chat Moss, it nevertheless consumed all the spoil from the Sutton cutting, leaving insufficient for use on the Sankey Viaduct. To achieve its height of 60’, the embankment called for 200,000 cubic feet of spoil. Fields alongside the line were bought, and soil transferred, but it would seem that there were limits to the amount available for extraction.

The timberwork shown in the CUTTINGS illustration is probably a temporary structure supporting the tracks until a source of infill became available from the eastern side of the valley once traffic could traverse the viaduct.

Ironically, the Kenyon Cutting, east of the Newton Viaduct, yielded 750,000 cubic yards of material. Some went into the Newton and Brosley embankments, but there was no means of taking it to the west of the Sankey Valley at the time, so fields were bought to act as dumping grounds for the excess spoil.

We know the link across the Valley was finished late in the construction period because William Huskisson MP visited the site in August 1829, and ‘he crossed the Sankey Viaduct, a temporary path having been laid across the one unfinished arch’. Since the complete line was open for the Rainhill Trials between the 6th and 14th of October 1829, the link would have been completed between those dates, but taking spoil across to complete the embankment may have been a low priority. As long as there was support of some kind for the tracks, traffic could move. In fact, the Viaduct was not finally completed until July 1833, when the top copings were installed.

In early 1829 Telford inspected the works, and was critical of Stephenson’s method of building embankments by which the spoil wagons were "brought to the top level and tipped down the whole height" of the incline. He preferred to build embankments up layer by layer, allowing for greater consolidation. There is insufficient detail in the drawing to say whether it illustrates a stage in the top-level filling process. There are slopes from both east and west, but neither seems to be the correct, steep profile for such a method of tipping loose materials.

In December 1831, 15 months after the Railway was opened, it was reported that the north-west wing wall and abutment of the viaduct were settling, and the stability of the structure was questionable. It was inspected in May 1832, and Stephenson was instructed to carry out the necessary "remedial work", but this is not described in any detail. If the embankment had to be cut back to allow access to the brickwork, a temporary trestle would have been necessary to maintain traffic flow, but the gap illustrated would seem rather excessive for this purpose.

Logically, the trestles were only a temporary measure, and would be used only if other, more permanent methods wee not available. Since access became available for spoil to be brought from the east as soon as the cross-valley link was completed, the drawing was probably made late in the construction process, somewhere between 1829 and 1831, possibly as the filling-in process was taking place. Photographs exist of navvies converting a trestle river-crossing at Accrington into an embankment by simply shovelling earth out of stationary wagons on the line above. If this method was being used, this would account for the somewhat irregular profile of the embankment below the trestles.

Editor’s comments: I still wonder the engravings in both Shaw’s and Bury’s "Views" of the Railway both show the embankments as complete, with no trestle-work. Both books claim that the artists made their drawings "on the spot" (though the east-coast sailing vessel on the Sankey Canal in Bury’s depiction leads one to conclude that embellishment followed back in London!). The drawing in question showing the trellis was published in 1850, and a similar one in 1833. That would seem to fit with the works necessary to carry out the "remedial works" begun in 1832, despite the misgivings mentioned above.