Despite mounting frustrations with the rollout of the Chicago Transit Authority's Ventra fare system, Mayor Emanuel on Tuesday stood by CTA President Forrest Claypool; Emanuel said the Cubic Transportation Systems contractor is responsible for the rocky Ventra implementation, not Claypool; Cubic was awarded a $454 million, 12-year contract to install and operate the system, and has spent $92 million on it so far, but has not yet been paid by the city