The Transbay Joint Powers Authority (TJPA) proposes to extend the Caltrain commuter rail line from its current terminal station at Fourth and King Streets to the multi-modal Salesforce Transit Center in downtown San Francisco. The Project includes construction of the underground guideway using both cut and cover and mined tunneling methods, tunnel ventilation and emergency egress and two underground stations. The project also includes installation of train control, signals, a communication system, and retrofitting 23 of Caltrain’s electric multiple unit trainsets and several non-revenue maintenance of way vehicles.