Abbotsford not site of unstable clay warning

Press, 30 August 1979, Page 16

Abbotsford not site of unstable clay warning

A Press Association message from Wellington, printed in “The Press” on August 10, the day after the Abbotsford slip, and headlined “Abbotsford’s shaky geology known in 1962,” quoted from a book a passage which in fact referred to another area. The quotations came from the second (1962) edition of a technical book on international geology by a Canadian, Robert Legget. This updated an earlier edition from before World War 11. The Press Association report said that the book describes Abbotsford as having unreliable mudstone rock, and a sisnificant fault running across the whole building area.

Legget was also quoted as saying that when a 240 ha coastal site a few miles down the coast from Dunedin was proposed for .a psychiatric . hospital, Sir

James Hector, at that time director of the New Zealand Geological Survey, had said: “The clay would move like any other plastic substance, with an almost molecular motion.” These passages in the book are in fact referring to an area north of Dunedin, notably the area of Seacliff Hospital. Discussing the abandoned Puketeraki- tunnel, about 40km north of Dunedin, Legget says that trouble with movements was experienced soon after the tunnel was opened. He says that by 1934 a resultant total movement of 17.9 in had been measured and that the only course was to abandon the tunnel. He then says that a few miles down the coast is the site of a large mental hospital. This reference is to Seacliff Hospital. After reporting Sir James Hector's warning. Legget says; “Unfortunately, as Ater

geological studies have shown, the entire site is underlain not only by the Burnside mudstone, but beneath it by the Abbotsford mudstone, an equally unreliable rock, with a major fault zone running across the building area. “The weak character of the mudstones has led to severe slumping, so that much of what appears to be solid ground is merely surface evidence of successive slump scarps. Serious movements have therefore affected the hospital from its earliest days; the first main building had to be completely demolished a few years after its erection because of serious and irremedial cracking.” So although the material mentioned in the Press Association report was correctly described as Abbotsford mudstone, the references were to its existence in the Seacliff area and not in Abbotsford itself.