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November 17

Technical Peer Review of Groundwater Settlement Effects

Fraser Thomas Ltd has been providing Auckland Council with Technical Peer Review services concerning groundwater diversion resource consents.

Many large building projects, particularly in the CBD, involve basement excavations that extend below the groundwater level and affect the flow and/or the level of the groundwater. Under the Resource Management Act 1991 (RMA) and the Auckland Unitary Plan, the taking or diverting of groundwater that does not meet permitted activity criteria requires a resource consent.

Taking or diverting groundwater results in groundwater drawdown beneath neighbouring properties, which potentially causes consolidation settlement of the foundation soils to occur. Consolidation settlement, in combination with lateral deflection of the basement retaining walls, potentially causes differential settlement of the ground surface within the neighbouring properties to occur.

Pat Shorten, Director – Geotechnical Engineering of Fraser Thomas Ltd has been peer reviewing selected resource consent applications for Auckland Council.  Fraser Thomas provide Council with a technical memo covering the groundwater consent application, any s.92 requests and responses, and the potential effects on neighbouring properties, as well as a set of draft consent conditions. For some applications, attendance at meetings with an applicant’s technical consultant is also required.

Recent projects that have been peer reviewed by Fraser Thomas include: the CRL tunnel in Albert Street; the redevelopment of the New Zealand Herald site on Albert Street; the SH20A Kirkbride Road grade-separated interchange; and the Commercial Bay redevelopment of the Downtown Shopping Centre, Customs Street West.