President Bush on Aug. 17 signed into law a measure that he called "the most sweeping reform of America's pension laws in over 30 years...." It includes major changes for 1,600 multi-employer plans, about half of which are in construction. The law requires ailing multi-employer plans to take steps to improve their health. It also allows plans to build up reserves for leaner times by raising the tax-deductibility limit to 140% of current liability, from 100% now.