Concrete Canvas Channel Lining at Avoca Mines

During health and safety works that were being carried out by Civil and Environmental Engineering Contractor, Priority Construction Ltd., it was identified that the former mining site was impacting the quality of the water in the Avoca River. Water dischargers from abandoned copper and sulphur mines were acidic and metal laden, contaminating the nearby river water.

It was decided that the spoil areas would need to regraded and capped, with drainage channels to redirect upstream drainage around the site, instead of through it. Whilst the original design used a combination of precast concrete channels and HDPE liner, there were concerns around the long lead in times for the precast concrete and the construction risks associated with steep slopes. Instead, Priority Construction Ltd. proposed the use of Concrete Canvas.

At Concrete Canvas, we offer Geosynthetic Cementitious Composite Mats (GCCMs), which are an alternative to traditional concrete methods. Unlike most concretes, our GCCM uses a specialist high early strength concrete, with a limited alkaline reserve. This means it has a very low wash out rate and can be directly discharged into the water course, without the need for prior treatment, making it an ideal solution for channel lining.

For this project, we recommended the use of CC13^™, which is our thickest type of GCCM. However, before the installation process could begin, the channel needed to be excavated and compacted to profile. A 250mm x 250mm anchor trench was then built on either side of the channel to allow the leading edge of the GCCM to be buried, preventing any undermining. Once the channel was prepared, the CC13^™ was mounted onto a spreader beam and hung from an excavator, allowing it to be easily unrolled. Each piece of CC13^™ was cut to a specific profile length and dragged into place, minimising material waste.

As the channel was located on a steep hill, concrete steps were installed to dissipate the water energy. Due to the flexibility of CC13^™, it was able to be laid over each step and pinned into the vertical interface of the steps using Hilti anchors. After each day of work, the CC material was hydrated using a hose and a 6000ltr water carrier.