The new owner of the Sparrows Point steel mill has a problem – his plan to construct a museum to house his personal art collection, reportedly worth $500 million, has been stopped by the village of Sagaponack, N.Y.

Ira Rennert, chairman of RG Steel, was given a stop-work order by a building inspector, according to today’s New York Post, for not filing plans with the village for the 10,000-square-foot museum.

The inspector spotted a concrete pumper truck on the reclusive billionaire’s oceanfront property, whose Italianate mansion and auxiliary buildings are believed to be the largest private residential compound in the U.S.

RG Steel purchased Sparrows Point and the Wheeling and Warren steel mills from Severstal in March and is now acquiring raw materials and repairing the “L” blast furnace at Sparrows.

The furnace is expected to be working in the next week or so, signaling the resumption of steel production that was halted last July.