An ominous anniversary…

I’ve just blogged about Ramboll UK Limited’s geotechnical survey of Posties Park, and some of the very worrying issues that will surface if any development of the site takes place.  There are eight significant geotechnical risks identified from the survey, but today I’m going to focus a bit on the last one listed – ‘previous landslide/instability of ground‘ :-

Ramboll’s risk register states, “Anecdotal evidence indicated that the former shipbuilding works suffered a historical slope failure with a mass movement of material towards the River Leven.”

Well Ramboll’s researchers were right – there was a historical slope failure.  However, if they’d gone beyond relying on anecdotal evidence they would have discovered just how catastrophic an event this was for the area, and what a troubling omen it is for any future development of this site.

It was exactly 117 years ago today, on Monday 12th October 1896 when a two-acre chunk of the Leven’s bank at Posties, or the Woodyard as it was known then, slipped away into the river, bringing down buildings and creating a huge wash and silt bank across the Leven.  This was the headline in the Glasgow Herald on 13th October :

Image

The Herald article, and a subsequent one in our own Lennox Herald on 17th October 1896, give a very clear picture of the chaos and disruption that this environmental disaster created.  This first excerpt describes the impact on the river :

 “…the bed of the river Leven was violently disturbed, and banks of silt were pushed up and out of the channel and right across the river.  The sand was in such quantities that it is stated by eye-witnesses that at one time it would have been possible to walk dryshod from bank to bank, and across what a few minutes previously was a stream of water about ten feet deep and eighty yards broad.”

The news article also describes the scene on shore :

“On the shore the damage done is much more serious than in the river, the banks for about 300 yards having sunk considerably below high water mark.  Altogether about two acres of ground in the form of a semi-circle, and on which were a number of buildings stored with ships’ fittings, have subsided to an average depth of 10 feet.  The affair occurred immediately prior to the workmen engaged in the yard resuming their duties after the breakfast hour, and happily no lives were lost.  Mr Galbraith, the occupant of the yard, was standing down near the edge of the water, and near to one of the large buildings, when the subsidence occurred, and he states that the ground gave way almost without warning.  He, on feeling the soil slipping from beneath his feet, ran father inshore, and had no more than reached solid ground, when, with a rumble, the slip settled down, and the buildings, along with a chimney stalk 50 feet high, came crashing down.”

It goes on to describe the scene that met the Herald reporter on his arrival :

“Our representative arrived at the yard not many minutes after the land gave way, and the scene that presented itself when he stepped inside the gates was one of the utmost havoc.  The earth lay in large banks or terraces, separated from one another by yawning rents, and intermixed all over with ships’ plates and fittings of all descriptions, and a mass of general debris.  Part of the buildings had sunk bodily, while others lay in a broken-backed condition.   One large stone building had been split completely in two, the one half standing on the bank, while the other lay in a mass of rubbish.  Another large building stands in such a dangerous position that in all probability it will have to be partially razed.”

Anyone interested in finding out more about this event should have a read of ‘Dumbarton: Its recent men and events’ by Donald McLeod.  It’s also available to borrow at Dumbarton Library, and is a really interesting little book.

So it can be seen that the area we know and love as Posties Park has an exciting and infamous past, and whilst the land appears to be relatively stable in its current use, it would seem that the idea of putting a couple of massive buildings housing 1000 kids and 100 teachers on the site would not be without considerable risks.  The following excerpt from Donald McLeod’s book describes the actions of two experienced civil engineers, Mr. Sandeman and Mr. Deas, who surveyed the site after the landslip :

“In accordance with instructions…five bores were made. …These bores showed that in the Woodyard, from about ten feet below its original level, the sub-strata is of a very treacherous kind, consisting principally of very soft mud, practically the same as shown by the bores in the bed of the river; so that, to quote Mr. Sandeman’s report, this ground “has always been in a condition of unstable equilibrium…”

Now, I’m no civil engineer and the detailed technical results from Ramboll’s recent geotechnical survey of Posties Park may as well be written in Sanskrit for all I understand. However, what I do clearly understand is this statement shown on Ramboll’s risk register summary :

“The made ground is not considered as a suitable founding stratum due to the variations of the density, shear strength and consistency in the material.  The Beach and Tidal Flat Deposits are also not a suitable stratum to place foundations on due to the very low shear strength and high compressibility of the material.”

Isn’t this just a verification of Mr. Sandeman’s assessment from 1896?  He called the site “treacherous” and Ramboll say “not suitable”.  Aren’t both these experts, over 100 years apart, effectively saying that building on Posties Park would be folly?

– MAx

(Thanks to Andrew Muir for researching newspaper reports on this event.)

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