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24 September 2014
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U: Underground

For the first time, television cameras have explored the depths of the disused chalk workings underneath the City of Norwich. Take an online look underground.....
video available. Watch video: Mike Liggins goes underground (Real, G2 3'28")
Download RealPlayer

chalk workings.
Chalk cavern beneath Norwich, pictures and words by Iain Meikle

Norwich is well-known for its miles of disused chalk workings - some dating back as far as the 13th or 14th Centuries.

The mines were sunk to exploit the rich deposits of chalk and flint that run from NW to SE across the county.

The raw mineral was cooked in kilns, fired originally by charcoal, then coal and coke. In a continuous process, new chalk and fuel was added to the top of the kiln in layers. The end result - lime, was removed from the bottom.

Kilns would often burn for up to a year. After cooling, the lime was mixed with animal hair as a binding agent to form mortar for construction.

Click here to read reporter Mike Liggins' description of his journey beneath the city

Click here to read about Mike's visit to a sewerage tunnel and a Victorian reservoir

video available. See video of the tunnel and reservoir (Real, G2, 3'29)

Lime was used elsewhere too. It was spread extensively on farmland, both to neutralise acidity, and to improve the texture of the soil. As rain fell on limed ground, the solution helped draw together clay particles into lumps.

As a result the earth drained much more freely.

A third use for the material was to produce whitewash. The lime was simply added to water, mixed and allowed to settle before being painted on to buildings.

Lime from Norwich produced a brisk trade to London with wherries carrying the mineral down the River Yare to Great Yarmouth.

underground.
City engineer Gary Thompson and the BBC's Mike Liggins in the workings.

The workings are only opened every two years or so to check their condition.

As long the chalk does not dry out too much, the tunnels and galleries remain remarkably stable.

In nearly all the well-known cases of collapse, burst water mains or leaking drains have eroded soil. The resulting cavity has then caved in.

More underground material

Internet links:
Norfolk Industrial Archaeological Society

 

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