NZS 3404 and the NZGS Module 5 guidelines set the framework for ground improvement in New Zealand, but applying them in Blenheim demands a specific understanding of the Wairau Plain. The loose alluvial silts and fine sands deposited over millennia create a profile where static settlement and cyclic liquefaction are both credible concerns. Most commercial and viticulture-related structures around Blenheim sit within 3 km of the active Wairau Fault, so a conventional footing rarely meets performance expectations without some form of treatment. A liquefaction assessment quantifies the residual strength of the interbedded layers, and when the factor of safety drops below 1.2, stone column design becomes the logical path to densify the matrix, install drainage paths, and transfer load past the weakest silts. The team works with NZS 1170.5 spectral demands and site-specific borehole data to set column diameter, spacing, and depth—normally between 6 and 14 metres in the Blenheim basin.
Thirteen metres of interbedded silt and sand with groundwater at 1.5 metres: that is the standard Blenheim profile where stone columns earn their place on the design register.
