Salt Caverns

Hawke's Bay Herald-Tribune, Issue 69, 8 April 1937, Page 13

Salt Caverns

Subsidence an old Problem for England.

"JTOW and again fresh interest ls anoused by the reporfc *of some new subsidence in the land over the great Cheshire salt-beds, &s, for instance, when not many days ago a chimney at Rode Heath dlsappeared into old mine workings. This ls by no means a new problem. Serious subsidence has been going on for almost two hundred years, and has become an increasing meoace to land and property. This vast and apparently lnexh&ustible salt-bed is of great value and importance. It now supplies the raw material for the blg ctamical wofks of Mid-Cheshire, and on it depends much of the industrial prosperity of the.coqnty, but its history goes back long before the beginnings of big industries and can be traced for at least a couple of thousand years. When the Romans reached £heshire they foUnd that salt was being manufactured from brine springs at Northwich. In the past salt was an important article of commerce, as it is in Central Africa to-day, and Mid-Cheshire became the centre -of this trade. In Domesday Book the number of "wlches," as the places of salt manufacture were called, was already large; and the extent of the trade may be judged from the place-names on roads radiating from this centre, which show the routes by which salt was carHed to more distant paris of the country— such as Saltersford on the -River Weaver and another Saltersford in the East Cheshire hiUs. WIDE AREA. rFHE main salt districts are centred in Northwich and Winsford, and the aalt-beds stretch from Heatley in the north, through Tabley, Flumbley, and Northwich, and then run up the valleys of the rivers Weaver and Wheelock to include Winsford and Middlewich and a distrlct near Sandbach and Lawton, where the recent Rode Heath collapse occurred. It is in the Northwich and Winsford areas that the main subsidences, known as "flashes," have formed, though the effects are felt in some places miles distant from the chief scene of action, and thus disprove the old contention that the collapses were caused only by the falling-in of old mines; the pumping of brine may cause collapse far from the actual site of the pump. There have for long been two methods of getting salt. There is the old system of using the brine springs which flow naturally— a system which was known to the Romans, — and it is by pumping brine that the salt used in the works of the Imperial Chemical Industries is obtalned. Another method was to hew the salt in rock-salt mines, but in moet places this has fallen into disuse. It was not till 1670 that rock-salt was found at Marbury, near Northwich, and from then till quite recently mining for rock-salt was an important lndustry. As the rock was hewed out pillars of salt were left standing to support the roof of the mine, and an illuminated mine was a show-place of some beauty. The miners were a race to themselves and, though the, work was. hard, regrets that lt has been given up may still be taard. The main and most far-reaching cause *

\ , of subsidence is undoubtedly the pumping of brine, but the rock-salt mines when abandoned and not filled in became an added danger. The pillars of salt proved to be less permanent than Lot's wife herself; water got into the old workings and dissolved them; the crust of land above the mine fell in, and so new subsidences began. I well remember the sudden disappearance of the water in a flash known as Marston Hole Some twenty-five years ago. It ran away through a gap in the bottom into an old rock mine below, leaving steep banks some seventy feet and more deep— mud and clnders covered with tin cans and other odds and ends heaved into the flash by passers-by and the local villagers. STILL GROWING. /^REAT efforts were made to stop the leak by dropping into it bags of cement or something of the kind, but after remaining low for a long time water evidently fllled the old mines below and the flash resumed its former level. Slnce then lt has grown and grown, and land and cottages, have dlsappeared. By the roadside stood the Townshend Arms, an inn known locally as the "Witch and Devil," which once provlded a passing motorlst of my acquaintance with bread, cheese and beer of satisfactory quality as he stopped there at the beginning of his short hpliday. It had gone altogether when he called on hls way home and he had to take his custom and his thirst elsewhere. Although brine-pumping in the immediate area round Norwich has almost ceased and the main supply is drawn from H&lford, near Plumbley, yet the flashes stlll expand and every year there is a bigger area of water, and it will be long enough before a condition of stability is reached. QUICK SUBSIDENCE. T OCAL inhabitants, many of them men of only middle age, will point to some spot in the middle of a great lake and tell how they used to work in the mines below not so many years ago. The Rhode Heath cavity, as seen to-day, is a puny and meagre affair in comparison with some of the holes with which the Norwich distrlct ls familiar. It ls not many yards across and already the bottom is covered with muddy water. For the sake of the owners of the canal, that runs hard by, and house property along the highway, it is to be hoped that it has done its worst and will spread no farther. We must, however, confess that there are some compensatlons for the destructlon of hundreds of acres of land and the formation of big lakes ln their place, for they are beloved of the flsherman whose "patlent angle" fllls many a good basket. They are, too, the haunt of a great diversity of water-birdsr the greatcrested grebe and little grebe, the wild duck and coot, the redshank and sandpiper breed there; and there come passing migrants and strangers, such as a whooper swan,, a fulmar petrel, or a whiskered tern; and on any day in the year seagulis show that they have found a good use for what man has destrhyed.