SAN DIEGO — The U.S. Department of Justice has unsealed eight indictments in San Diego and elsewhere detailing a massive narcotics trafficking operation by the new bosses of the Beltrán Leyva organization, once one of Mexico’s most powerful drug cartels. The announcement Wednesday came the same day the U.S. Coast Guard unloaded more than 18,000 pounds of seized cocaine at the 10th Avenue Marine Terminal in the Barrio Logan neighborhood of San Diego. Officials said the two events were unrelated, as the cocaine offloaded by the Coast Guard was seized over the past two months, while the alleged c…