A geotechnical study of ground conditions in Whakatāne’s central business district will provide useful information to help building owners achieve the Government’s future seismic resistance requirements.
The study is part of a Whakatāne District Council initiative which aims to facilitate the strengthening of earthquake-prone commercial buildings in the CBD area. General Manager Planning and Regulatory Services, David Bewley, says the study provides reliable information to assist engineering professionals undertake detailed seismic assessments of earthquake-prone buildings.
“The study findings have now been validated and modelled by GNS Science and, in conjunction with the infrastructure guidelines developed by the Earthquake Commission, Ministry of Business, Innovation and Employment and the Christchurch Earthquake Recovery Authority, will provide invaluable information to assist building owners make informed decisions about seismic strengthening solutions or asset replacement,” he says.
“We now know the soil class properties of the CBD area and can link that information to the data developed after the Christchurch earthquake. That confirms that in our CBD, retrospective strengthening solutions can be readily achieved in most circumstances.”
New Zealand subsoil classes range from A (strong rock) to E (very soft soil) and the study indicates that the majority of the land falls within the NZ subsoil class C – shallow soil – or better. Those findings are similar to those in many urban centres, including Tauranga, Hamilton, Auckland, Wellington and Nelson.
Mr Bewley says that Class C soils may be subject to liquefaction and lateral spreading as a result of a very strong earthquake, but both hazards are “readily manageable”.
“As a result of the ground study, we are likely to incorporate MBIE’s guidance in our future planning when replacing underground infrastructure, and when requiring geotechnical investigations for the design of new building foundations. The information provided by those investigations will add to our existing database, which will continue to grow in value.”
The ground study findings were received by the Council’s Projects and Services committee Thursday, 28 May, and together with the 3-dimensional geological model produced by GNS Science will be made available via the Council’s website by the end of June. That information will reduce the cost of the detailed seismic assessment process for building owners and assist in the development of effective and economical earthquake strengthening options.