Case Study – Backhouse

Attenuation tank works

Area: Great Somerford Client: Backhouse Housing

Within our site consisting of 20 units, we were required to carry out the civil works for, and organise the installation of, a 9m x 25m Rigofill Cellular Attenuation Tank. This system is connected via the main storm drainage line within the road, and leads to a new headwall outlet.

Northavon Groundworks Health and Safety Duties:

Due to this sizeable scope of work, it was important for us to ensure maximum safety and security around the perimeter of the excavation, which was over 1.5m deep, we achieved this by forming a heras fencing boundary. It was also important to batter off the ground around the excavation, as well as form temporary steps, for operatives to use as safe access to their working area.

Construction process:

1. Through the use of an in-house engineer, we were able to pin point each corner of the tank prior to excavation. It was vital to ensure the setting out of this area was accurate, due to the further drainage lines that would be connecting into the system.
2. Northavon Groundworks had the responsibility of blinding the base level of the excavation, before installing an impermeable membrane layer, as per the design.
3. We procured a sub-contractor who specialises in the supply and fit of crate systems, which was completed within 3 days.
4. Once the crates were installed, a further impermeable membrane layer was incorporated to wrap the remainder of the system.
5. The remaining perimeter of the system was surrounded with sand, which prepared us for the main concrete pour.
6. A 150mm thick concrete slab, utilising an RC28/35 mix was poured, inclusive of an A393 mesh layer, with 50mm cover within the concrete.

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