Hull, A.G. 1980 Bench mark stability report, Lyttelton-Westport. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EDS 62 56 p.
Abstract: Part of the continuous Earth Deformation Studies Programme in New Zealand includes precise levelling from Lyttelton to Westport. In order to measure secular and abnormal rates of vertical deformation it is critical that bench marks on all levelling routes are sited in geologically stable foundations. Where pre-existing bench marks are used it has been recommended that their stability be assessed and where necessary bench marks be sited in the most stable foundations available. This report assesses the stability of all existing and proposed bench marks intended to be used on the above levelling route. Also included are bench marks on a loop from O'Sullivan's Bridge - Springs Junction - Inangahua - O'Sullivan's Bridge. The stability assessment has been carried out in four steps, commencing June 1979 and completed September 1980. The Christchurch - Rangiora section has been assessed twice as the initial survey showed potential instability for the entire area between Mt Pleasant and Woodend. The report is divided into sections between fundamental marks, site reports being preceded by a brief outline of the geology of the area and foundation materials encountered. At the end of each section comments and recommendations regarding any unstable, new or additional marks are made. (auth)
