State regulators have fined PG&E for their role in the fatal gas-pipeline explosion in San Bruno. The incident killed eight people in September 2010. In the years following the blast, the Public Utilities Commission was criticized for not penalizing PG&E.  Yesterday, the PUC agreed to fine the utility $1.6 billion for failing to comply with mandated federal and state pipeline safety requirements. PG&E officials say they will not appeal the penalty.