Case Study – Concrete Canvas GCCM at the Avoca Mines
26 June 2018
The finished channel
In June 2017, Concrete Canvas® (CC) Geosynthetic Cementitious Composite Mat (GCCM) was used to line a series of drainage channels at the Avoca Mines in Co Wicklow. The site had a long history of mining, with copper mining activities having been reported as far back as 1720 in the Avoca River Valley.
This area was overlain by waste material contaminated with heavy metals from the old mining activities and the close proximity of the spoils to the river had had a detectable, negative impact on water quality. The drainage channels were engineered to divert surface water around the former contaminated spoils zones. As part of the remedial works, the contaminated spoils zones were regraded and capped with clay soil and the drainage channels were installed at the boundaries of the site to redirect upstream drainage around the capped areas.
Managing installation risks
The original design used a combination of precast concrete channels and a high-density polyethylene liner and rip-rap channel. This plan presented some installation risks (due to steep slopes and the need for heavy equipment) as well as a long lead time due to the precast concrete. The contractor, Priority Construction Ltd, proposed concrete canvas as an alternative solution for lining the drainage channels.
This suggested offered a number of advantages. The CC bulk rolls could be cut to the exact section of any given channel, eliminating wastage. It could easily accommodate variations in the site profile. It also offered significant speed and ease of installation, cost savings, heightened durability, and greater environmental friendliness than conventional concrete.
Low washout rate
Unlike most concretes, CC uses a specialist, high early-strength concrete with a limited alkaline reserve. It has a very low washout rate. When combined with the volume of water required for hydration, these characteristics mean that CC run-off can be directly discharged into the local water course without the need for prior treatment.
It was an ideal solution for protecting local waters from the contaminated spoils. In total, 1,520m2 of CC13 (13mm) was installed within two weeks and will provide long-term scour protection and erosion control for the network of drainage channels on the site. Following a recent site visit one year after the installation, the material is performing as intended and the client and consulting engineer are impressed and very happy with the durability and performance of the GCCM.
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