A senior councillor has warned of a potential ‘environmental disaster’ if a £76.5m relief road is built over the contaminated land of a former oil refinery in Trafford.

The vice-chair of the authority’s scrutiny committee Cllr John Holden voiced concern the controversial scheme for the Carrington Relief Road could be ‘opening up a Pandora’s box’.

The plan to link the ‘isolated’ areas of Partington and Carrington to Timperley and Altrincham with the new road parallel to the A6144 is seen as key ahead of the development of 5,000 new homes and is included in the Greater Manchester strategic plan for the next 17 years – Places for Everyone (PfE).

A planning application for the new road is expected to be brought before Trafford’s planning committee within the next 10 months.

If approved, it will go through the former Shell Carrington Petrochemical facility.

Already there are plans to prevent surface separate surface water draining from the proposed road mixing with other more toxic chemicals buried under the surface of the site.

Cllr Holden told his colleagues: “Looking at the road, it’s going right through the former Shell site.

“I have read a previous report that was produced and it really made me wish that I had listened more intently nearly 50 years ago when I was doing organic chemistry for A Level.

“Because there were some really nasty sounding things in that report which are going to be disturbed in quantity by the work on that road.”

He went on: “Have we access to sufficient expert advice to avoid creating an environmental disaster in that area? Do we know what Shell has chosen to put into the ground?

“We might be opening up a veritable Pandora’s box.”

The council’s director of growth and regulatory services Adrian Fisher agreed that the contamination issue was ‘recognised and something we are definitely going to have to grapple with and address through the project’.

He said: “We know we are going to have to design a completely separate drainage system to avoid contamination of the groundwater, or cross-contamination.

“It is absolutely an issue of concern. At the moment we feel we’ve got the strategy in place to deal with it, but as things progress it is something we are going to have to make sure we are doing it correctly.

"The Environment Agency, which is the regulator, will be making sure we do what we should be doing.

“We are trying to ensure that the water from the road doesn’t mingle with the groundwater and make an existing situation worse.”

But he also said that currently there was nothing that prevented the contaminated material getting into the groundwater.

Executive member for economy and regeneration Cllr Liz Patel added: “It’s a complex contamination that’s relatively newly understood.”

The Carrington Relief Road is opposed by the Friends of Carrington Moss pressure group, which is worried about the impact on peatland south of the proposed carriageway and the drainage issues.

The group is also campaigning for the reopening of the railway line linking Partington and Carrington with Timperley and Altrincham with the local road system said to be ‘at capacity’.

Cllr Aidan Williams, executive member for climate change, said: “We are not opposed to a reopening the railway line, but it is not in Trafford council’s gift to determine."

He said that former Stretford and Urmston MP Kate Green lobbied for the move ‘on a number of occasions’ but it had not been approved by central government.

“The reality is that we are not going to be able to deliver the residential units we need unless the road is put in place,” he said.

“The existing highway network is at capacity.”