A U.S. agency will take over some pension plans.

The Pension Benefit Guaranty Corp. agreed to take over pension plans covering an estimated 13,000 retirees of Wheeling-Pittsburgh Steel Corp., officials said. The settlement is a step toward resolving the most costly pension termination by a single employer in the PBGC’s 12-year history, but it leaves unresolved the question of how much Wheeling-Pittsburgh may have to pay to have the agency assume its $475-million unfunded pension liability. The nation’s seventh-largest steel company filed for Chapter 11 bankruptcy reorganization in April, 1985. It later moved in court to terminate the pension plans.