Engineered retaining wall and major site excavation

Why the job had not started

We were referred to this project after the client had been unable to get the retaining wall underway with other contractors. The scope was a 20 metre engineered concrete sleeper wall between roughly 2.2 and 3.2 metres high, with significant excavation, spoil removal and adjoining rock walls.

Before quoting we ran a full site assessment to establish the real scope, the access limits and the constraints. We reviewed the existing engineering documentation and identified changes needed to reflect the conditions actually on site. The documentation was amended and finalised before the project was contracted.

As a registered builder we then quoted the documented works, administered the domestic building contract and arranged the required Domestic Building Insurance before construction started.

Working along the boundary

The main wall sat along a neighbouring boundary with a cut reaching about 3.2 metres and structures on the high side.

Bulk excavating the full boundary would have opened a significant cut next to the neighbour for no good reason. Instead we set out the site and progressively trenched the wall alignment and post locations, so the excavation stayed controlled and the boundary was never exposed further than the work required.

The ground was hard enough to need rock capability, and access around the existing house was restricted. Every steel post, sleeper, drainage line and load of aggregate came in through that access, and every cubic metre of spoil went back out the same way.

Building the wall

Footings were excavated into hard ground with our own rock capable equipment. Posts were installed, concreted and set accurately to the engineered heights.

Once the concrete cured the sleepers went in, followed by the ag drain and drainage aggregate behind the wall. Finished length approximately 20 metres, between 2.2 and 3.2 metres high.

Moving the spoil

The wall was part of a broader transformation of the site, including a cut that removed roughly 250 cubic metres.

Trucks could not reach the excavation area, so spoil was progressively moved around the existing dwelling to a loading area. Excavation, material handling and truck movements had to be coordinated as one operation rather than treated as separate packages.

Finishing the site

With the engineered wall and the cut complete, we sourced heavy quarry rock from a local quarry at Launching Place and built the adjoining rock retaining walls.

Those walls taper from about 3.2 metres down to the lower ground level across two sides of the site, tying the structural wall into the surrounding levels.

The result

Despite the scale of the excavation, hard ground, restricted access and wet weather, on site works were finished in under three working weeks.

What the job actually demonstrates is scope. Site assessment, engineering review, formal contracting, Domestic Building Insurance, excavation, structural construction, drainage, spoil removal and final site works, carried by one contractor.