Langham's Leaks
New Technology Pioneered on the Leicester Line
the second of three articles by Dave Goodwin reprinted (slightly edited) with permission from the Old Union Canal Society Magazine
Autumn 1998
The technology of casting a concrete channel to form a leak-proof bed to the canal was pioneered by Canal Manager Millner in 1916 along a leaky section of the Leicester Line above Tythorn Lock. His success was then repeated further afield - on the notoriously difficult Buckingham Branch of the Grand Junction Canal, and again on the mainline nearer London. I followed this project through his old letters in 'Foxton Locks & the GJCCo', but plans showing the leaks on to 'Mr Langham's land' at Warwick Record Office now reveal much more of this fascinating story.
Ground Conditions
It is doubtful if the original constructors realised that two distinct 'lime stone layers', as Millner called them, existed fairly near to the surface on the valley side around Tythorn Hill. They would have dug and puddled past this spot in the ordinary way. If leaks developed later - in the form of 'pipes' leading down through the rubbley layers - they would have been probed for, and packed with more puddle clay. (In other trouble spots - including that classic site at Mountmill, before the 1919 repair, where the rock strata was a little thicker - the way would be to de-water, clear off the area, clean out the fissures and pour in concrete). By its broken nature, however, the stony layers at Tythorn would have been very difficult to deal with.Gordon Thomas
In 1911, the GJ Engineer, Gordon Thomas, ordered Thomas Holt to dig a trench to intercept the Langham Leaks, filling it with concrete to form a massive 'deep well' against the (downhill) towpath bank. It reached down 11'6' below weir level! The work started about 130ft above the lock head, and ran for 47ft. Despite its size, it did not cure the leaks, and as Millner's 1916 drawing indicates , the rubble layers went deeper still in some places. Thomas can be forgiven, since modern geology maps fail to do more than indicate roughly the limits of localised strata. Bumblebee Lock (1/4 mile below and nearer Kilby), is shown as sitting on ancient Lower Lias Clay. Turnover Lock (1/4 mile uphill, nearer Newton), is sited on Ice-Age Boulder Clay. Tythorn Lock itself is 'borderline' and may actually have been leaking into the contact face between these major strata, which could have been formed as wash-out deposits on the valley side.Thomas Holt
Holt retired as manager of the Leicester Line in 1914. By 1916 Gordon Thomas had left the Company under a cloud (more of these stories are told in the book mentioned). One of Millner's proteges 'Young Walker' (Bert), had been installed at Kilby Bridge, and Millner himself was being considered for G. Thomas' old job as Company Engineer. Thus Millner had practically a free hand at this time, before William Yates was eventually appointed to the Engineer's post.Millner's Solution
Rather than continue with a deep(er) wall, Millner proposed 'a section of shallow walling and invert in concrete forming a basin over the leaky section of the pound'. 'It will take considerably less material than the deep wall and I feel quite satisfied of its success in stopping the leakage', he wrote to London H.Q. He estimated '£4 per yard forward at less than the cost of the deep wall'. He got Walker to draw sections across the canal at about 45ft either side of the Thomas wall, and further up the canal. He finally decided on a complete channel for just over 80ft above the Thomas work, plus another slightly longer section on the valley (towpath) side only.Work Details
A ' reversible stank' was to be employed to close off one half of the canal at a time to keep traffic moving - another Millner introduction. Walker's cross-sections show considerable erosion had taken place on the offside. Once the canal had been stanked off and pumped dry, the silt would have been dug out until a suitable profile had been achieved. The new invert or floor would then have been cast in situ, the sides formed of concrete slabs, packed with rough concrete behind. Different grades and thicknesses were employed, topped off with a 1'6' wide coping, again in concrete. Each of the three sections took something under a month, the work being complete on October 16th.Later Concrete Work
The First World War saw the introduction of concrete as a construction material. Stone had become too costly for other than prestige projects, and bricks were slow to lay. Millner cast concrete blocks by the hundred for use in coping and bridge building work. Bridge 72 at Saddington Tunnel (rebuilt 1917), and Bridge 66 at Debdale Wharf (1922) both made use of this technology, although they have the overall appearance of brick structures from a distance. Kilby Bridge, however, is a late 1930's all-concrete-cast structure.1930's Works
The early 1930's saw the introduction of cast-in-situ concrete literally by the the mile, and there are many dated examples along the Leicester Line. The wide-locked route up Hatton and Knowle into Birmingham was a creation of this era. Strange that it all was started so long before by a local man on our own canal - even stranger that it happened during a World War, when capital works in general were severely restricted. 'Langham's Leaks' must have represented a considerable problem, vital to cure if the canal was to remain open as a strategic artery of trade. In the '30's more of the short pound above Tythorn was worked on, and in the late '80's a persistent leak was to be seen right beside the lock approach, feeding a large wet patch in the field below. Landowner Langham may be long gone, but clearly the problem still lingers.Website design by Jeremy Cooper at oliomedia