A SECOND massive hole has been discovered in the river bed at Tadcaster, which threatened to cause another pier of the bridge to collapse.

More than 50 tonnes of special underwater concrete has now been poured into the scour hole, to protect the pier and allow bridge reconstruction work to be carried out.

Scour holes develop when rapidly-swirling water removes the material below the water, typically around fixed structures such as bridge supports.

A first scour hole which had already been found under one of the piers that collapsed during December's floods, has now been found to have been 2.5 metres deep, and has been filled with one-tonne bags of stones to provide protection should river levels rise again.

Officials initially feared the hole could have been up to six metres deep.

A cofferdam, or temporary enclosure, is also to be created upstream and downstream of the bridge to ensure the pier foundations can be rebuilt in dry conditions. If water goes over the top of the dam in extreme conditions, it will be pumped out.

The developments have been revealed by North Yorkshire County Council, which says it is pressing ahead with the 'complex, painstaking' reconstruction of the partially collapsed road bridge over the River Wharfe.

A spokeswoman said the Government had pledged £3 million to re-build the bridge and the council was hoping this sum would enable improvements such as widening its pavements.

"However, until the foundations have been rebuilt, it will not be possible to confirm whether this can be done within the £3 million budget," she warned.

She said the second scour hole, which 'posed a serious threat to the stability of the fourth pier,' was found by divers working for the council last Wednesday after stones and rubble infill from the bridge were cleared from the river.

"On Monday, the divers poured 22 cubic metres, over 50 tonnes, of special underwater concrete into the scour hole, which will protect the pier in order for reconstruction work to be carried out."

Cllr Don Mackenzie, executive member for highways, said river levels were expected to rise over the next day or two because of heavy rain, which would create pressure against the bridge, and so the stabilisation work had been very timely.

“Our contractors are working very hard to gather the geotechnical information necessary so we can begin to design the new bridge foundations," he said.

"We are pushing ahead, but river levels have been slow to drop and more rains this week will cause some further delay. We are still aiming, however, to complete this complex and painstaking reconstruction within 12 months.”