A DISUSED nuclear shelter built underneath the former headquarters of two councils will have to be filled in before the site can be sold – and that will slash the cash they can raise from its sale.

County Hall, in Cwmbran, which was shared by Monmouthshire and Torfaen councils, closed in March because the building has ‘concrete cancer’. With rain penetrating the cladding and rusting steel supports, it would have cost £30 million to repair.

At last week’s meeting of Monmouthshire Council, held at the Shire Hall, Monmouth, councillors were told that a void in the ground underneath the site is part of the reason that the value of the land has reduced by £675,000 since valuations were lastt made.

In 2008 the Argus reported that Monmouthshire and Torfaen councils hoped to get around £4 million each when the site was sold – but land prices have since plummeted.

The council’s deputy leader, Cllr Bob Greenland, said the 34-year-old County Hall site at Cwmbran has recently been re-valued and is no longer worth the £900,000 since estimated.

He said: “Investigations at County Hall discovered a void underneath that is so large that when it is demolished we would have to import large amounts of soil to flatten off the site.”

The bunker forms only a part of the void so council needs to carry out investigations to find out how big it is and what else is down there.

Cllr Greenland said that as a consequence the Estates team revised the asset valuation to £275,000.

Referring to the audit of financial statements report, he said: “The asset valuation of County Hall is overstated by £675,000.

“The council no longer uses County Hall at Cwmbran as an operational asset, and as a consequence Estates have only recently revised its land valuation for the site to £275,000.”

He said that Torfaen council is proposing that affordable housing be created, which could mean the valuation changes again.

Cllr Greenland stressed the figure is not a market valuation but an accounting valuation and will not affect this year’s financial statement.