Manchester's Bank Top Tunnel

A modern view of the later outfall from the tunnel

Source: Nick Rushton via Facebook

It is a failing amongst many writer/researchers to blindly accept what has been written before.

That’s not intended as a slur, though perhaps a little slap on the wrist for laziness.

One that really does take very little to put right but which tends to be repeated sometimes with added research but not even a glance at the basic false premise is the Duke of Bridgwater’s Bank Top Tunnel off the River Medlock in Manchester.

Modern records of this tunnel state that

• It was built to take coal to Bank Top. [near the site of Piccadilly Station]
• It was abandoned after about 11 years because the Medlock silted up, raising the surface level by 8 feet, rendering the tunnel impassable to boats.
• One source, after stating the previous point goes on the state that the Medlock silted up at the rate of half an inch a year, check.
• Most references show a low arch on the River Medlock at Asia House and state this as evidence of the amount of silt accumulation.

There are several other minor points but these will be sorted as I offer my alternative view.

• The low arch on the Medlock is built from modern engineering brick laid with tight joints and is clearly (even from photographs) contemporary with the building of Asia House in the first decade of the 20th century. As such it clearly is of no use as evidence of the state of the Medlock a century earlier. In addition, if you look at maps of the period it is clear that the river was much wider when the tunnel was built. The map in Keith Warrender’s otherwise excellent book Underground Manchester has a modern plan of the tunnel showing a short change in alignment as the tunnel joins the river suggesting that the tunnel was extended when Whitworth Street was built.
• As the Medlock makes an end on connection with the Bidgwater Canal and as no major structural alterations have been made to the canal, it is obvious that the surface level of the Medlock is pretty much the same as it was at the turn of the eighteenth century.
• Considering that both Egerton and his engineer Gilbert were both very clever engineers well used to manipulating water in tunnels, the idea that they intended to rely on legging boats and that they abandoned the tunnel because of silting is not worthy of consideration.
• The tunnel was by all accounts used to transport coal to Bank Top, roughly , to Knowles and Son, colliery owners in the area of the Ashton wharf!

Consider also that these skilled mining engineers in charge of skilled miners, took two years to dig a six hundred yard tunnel. Not likely if the tunnel was indeed intended as a commercial coal carrying enterprise.

In 1767 Brindley surveyed a line for the Rochdale Canal, it is unthinkable that he did not tell Egerton about this and let him go ahead and dig a navigable tunnel that would have a very short life.

I think that this tunnel was cut in the full knowledge that when a canal arrived at Bank Top, as it surely would, there would be a large quantity of water that the proprietors would need to dispose of and Egerton saw that if he had an existing tunnel he could not only secure a water supply but also additional revenue. Hence the two years building, no point in building it too soon before it was needed.

It might be that the Bridgwater enabling act allowed for the building of navigable soughs, but not tunnels though it is far more likely that Egerton threw a red herring, claimed it was a navigable sough to avoid the proprietors of any new enterprise suspecting that they were being held to ransom and refusing the use of Egerton’s sough.

I rather suspect that the idea of the Medlock silting up by eight feet and blocking the Bank Top tunnel is as a result of confusion caused when the Rochdale canal, on its way to Castlefield, cut across the Merchants tunnel at a height of eight feet.

To sum up, there is no evidence that the River Medlock silted up by Eight feet but plenty that it didn’t.

There is no evidence that the tunnel was cut primarily as a navigable tunnel and the date of abandonment does coincide with the opening of the Rochdale Nine.

I'm still surprised at the number of people who insist that the tunnel was abandoned as a result of it silting up!