The Federal Emergency Management Agency announced yesterday that it is rolling out a plan to waive debts for many victims of Hurricane Katrina and other disasters who may have mistakenly received millions of dollars in aid. The debts, which average about $4,622 per recipient, represent slightly less than 5 percent of the roughly $8 billion that FEMA distributed to victims of Katrina and other 2005 storms. Some of the overpayments were caused by FEMA employees’ own mistakes, ranging from clerical errors to failing to interview applicants, according to congressional testimony.