Just before construction began in 2012, the start of revenue service on the Central Subway extension was scheduled for December 2018. When the main contract was awarded to Tutor Perini in May 2013, schedule float (the amount of time set aside for delays) was reduced from 14.8 months to 5.2 months. In 2014, the San Francisco Controller's Office audited the project and predicted it would be completed on schedule in December 2018 and slightly under budget. Tunnel boring completed in June 2014, a month ahead of schedule and under budget.