Client: Whitford Investments Ltd
Location: Flatbush, Auckland
The site is 25.74ha and located at 571 Ormiston road, Flatbush. It was run as a farm lifestyle block, predominately covered in pasture with pockets of native bush mostly located in the gully areas.
The project required 46 Lots ranging from 2000m2-8200m2 in Stage 1 and 8 Lots ranging from 2500m2-5000m2 in Stage 2.
The site topography ranges from rolling to steep, there are three steep gullies with ridgelines that access the top and bottom. The underlying soil is more or less weathered mudstone/sandstone and the gullies are wet with isolated springs present.
The roads, accessways and Lots are within close proximity to identified headscapes and shallow seated slumping. A mix of palisade retaining walls, geotechnical underfill drainage (Counterfont drains) and buttressed fill was required to ensure inherent stability for these components of the project to mitigate any risk.
Key components of the project were:
Ø Cut/Fill on steep undulating terrain, 65,000m3
Ø Counterfont Drains, 535M 0 to 5M + deep
Ø Pallisade Walls, 2020m
Ø Geotech Benches, 14,000m2
Ø 1 x 18M single lane bridge
Ø 1800m2 of reinforced concrete accessway
Ø 20 x Wetland swales incorporating weirs, spillway, rock baffles, scruffy dome discharge chamber and planting.