A portion of the million tonnes of rubbish illegally dumped on the banks of the Faughan will remain buried in the ground as an integral part of a flood compensation scheme that will be developed with the Claudy to Campsie section of the A6 road project.
A consultant says it’s environmentally safe to do so provided a trench is put in place along the river to prevent contamination.
Filter drains and membranes will also have to be put in place and the contaminated land will have to be capped with rubble from the road construction.
That’s according to Roads Minister Michelle McIlveen, who has revealed details of plans for the site in response to a series of queries from Green MLA Steven Agnew.
In early 2014 the erstwhile Roads Minister Danny Kennedy said the discovery of a massive illegal dump at Mobuoy Road would not prejudice the new A6 road upgrade.
But he confirmed that part of the site was to be reinstated as a new flood plain to compensate for that lost to the road, which skirts the illegal dump’s eastern peripheries.
Now Ms McIlveen has confirmed: “Consultants experienced in the remediation of contaminated land have advised that the contaminated material can be left in situ provided: a watertight cut-off trench is installed alongside the River Faughan to prevent contaminated groundwater migrating into the river; filter drains are installed within the contaminated material to direct contaminated groundwater to a sump where it can be removed and dealt with offsite; an impermeable membrane is installed over the contaminated area to prevent ingress of rainwater into the contaminated area; and
the contaminated area is capped with surplus excavated material arising from the road construction.
“Item 4 listed above is an integral part of the earthworks for the scheme and is already allowed for in the scheme estimate.”
Part of the existing flood defences are to be altered.
“As part of the compensatory flood plain mitigation it is proposed to lower, but not remove, the river bank bund to accommodate a 1 in 5 year return period flood level.
“To prevent standing water accumulating in the area behind the bund excess material arising from the main scheme will be used to fill the area to a 1 in 5 year flood level,” said Ms McIlveen.