Where even though a union was decertified, the employer was still obligated to make contributions to its welfare fund until expiration of collective bargaining agreement.The 7th U.S. Circuit Court of Appeals affirmed decisions by U.S. District Judges Milton I. Shadur, John Z. Lee and Amy J. St. Eve.RiverStone Group Inc. is a producer of crushed stone, sand and gravel. RiverStone had a collective bargaining agreement with Local 150 of the International Union of Operating Engineers, AFL-CIO.The latest agreement, approved in …