The Milldale Stage 2 & 3 development will form approximately 630 residential and commercial lots. Extensive earthworks and retaining structures will be required to create the proposed landform in the unique and challenging Northland Allochthon geology. The south flank of the dominant easterly trending ridge slopes moderately to the site boundary with a protected area of native bush. To the north, deep, low-lying alluvial deposits exist around a stream which will be retained in the proposed development
- Site investigation including the drilling of machine boreholes, excavation of test pits and cone penetrometer (CPT) testing.
- Development of a ground model, including cross sections and plans.
- Stability, Settlement and Liquefaction Analysis and reporting.
- Working closely with the client to develop a 3-dimensional ground model to enable refinement of the required undercuts and estimation of earthworks volumes.
- Design of retaining structures and an in-ground (palisade) wall.
- Continued liaison with the client and contractor to facilitate the upcoming earthworks program.
The site presented two distinct areas and associated challenges; the southern slopes of the main ridgeline required shear keys / undercuts to stabilise, with the protected bushland at the southern boundary adding to the constraints on possible solutions. The low-lying alluvial soils in the northern portion of the site were found to be up to 15 metres deep and highly plastic and as such, typical methods to accelerate settlement such as pre-loading and wick drains are unlikely to be particularly effective. Mapping of alluvium depth combined with proposed fill depth enabled the client to consider predicted settlements in the development staging.