Scope of works

As part of our groundworks and civils package for Orbit Homes at Smee Lane, Bateman Groundworks delivered the installation of two wet wells to manage foul water and stormwater from the development. Located at the lowest point of the site, close to the woodland and lagoons, the works involved an excavation approximately 15 metres long, 8 metres wide and 8 metres deep, together with temporary works, precast concrete chambers, associated pipework, valve chambers, backfilling and compaction. The works were programmed over approximately eight weeks, with the main installation completed ahead of the anticipated programme.

The installation itself went really well. With an excavation of this size and depth, there’s a lot to coordinate between the temporary works, plant, deliveries and the different teams involved. We had a few delays with materials arriving, but nothing that changed the way we approached the job. The ground conditions were good, we had no significant issues with water ingress and, ultimately, we completed the main installation ahead of programme.

Our approach

At eight metres deep, this wasn’t simply a case of digging a big hole and dropping the chambers in. The excavation needed a substantial temporary works system to keep the working area safe and supported throughout the installation. An NTS shoring system was installed progressively as we went deeper, with safe access provided using a ladder, davit bar, harness and winch. We also needed clear access around the full excavation for lifting, deliveries, plant and material movement – all while keeping the rest of the site moving.

The size and weight of the precast components dictated the plant too. A 37-tonne excavator was brought in to handle the temporary works and lift components including valve chambers weighing around 11 tonnes each. FP McCann supplied the precast chamber sections, which were installed progressively along with the bases, valve chambers and connecting pipework. Once everything was in position, the excavation was backfilled and compacted in approximately 300mm layers using a RAMMAX roller, ready for the next stage of the installation.

Key stats

8m Deep Excavation: The excavation reached approximately eight metres below ground level, requiring a staged temporary works system and controlled access throughout the installation.

15m x 8m Working Area: A sizeable excavation at the bottom of the development, with enough surrounding space maintained for heavy plant, lifting operations, deliveries and movement of materials.

37-Tonne Excavator: Brought onto site to provide the lifting capacity needed for the shoring equipment and heavy precast components, including valve chambers weighing approximately 11 tonnes each.

Challenges faced and overcome

Deep Excavation

At approximately eight metres deep, the excavation needed careful sequencing and robust temporary works. The NTS shoring system was installed progressively as the excavation developed, with controlled access using a ladder, davit bar, harness and winch.

Heavy Lifting

With valve chambers weighing around 11 tonnes, the right plant was essential. A 37-tonne excavator provided the capacity needed to handle the temporary works and position the heavy precast components safely and accurately.

Keeping the programme moving

Delayed deliveries were the main challenge on the job. The team coordinated the arrival of the shoring equipment, precast chambers and other components around the installation sequence, keeping the works moving without changing the original plan and completing the main installation ahead of programme.

2 Wet Wells: Separate underground systems were installed for foul water and stormwater, forming an important part of the permanent drainage infrastructure serving the Orbit Homes development.

11-Tonne Valve Chambers: Individual valve chambers weighed approximately 11 tonnes, making lift planning and the choice of plant a key part of the installation process.

300mm Compaction Layers: Once the chambers and associated pipework were installed, backfill was placed and compacted progressively in approximately 300mm layers using a RAMMAX roller.