complicating the approval process and increasing engineering, cost, and environmental challenges. Alternative 2, also known as the Pennsylvania Avenue Extension (PAX) could be built as a separate project and connected to the approved DTX alignment in the future. Under PAX, trains would run in twin bored tunnels from a point near the southern end of the existing 22nd Street station. In addition to the alternative alignments, RAB proposed moving the existing surface railyard, opening up land for potential housing or commercial development, and also proposed loop extensions out of the eastern end of the TTC to allow it to operate as a through-station, rather than a stub-end terminus, increasing capacity by overcoming the limited number of platforms in the train box. The proposed loops could be extended to Oakland and/or Alameda as well, complementing the existing Transbay Tube. The new proposal has an estimated cost of $6 billion and is projected to be complete in 2027. A portion of funds for the project were put on hold in October 2018 due to concerns about the project's governance stemming from cracks discovered in the structure of the Transbay Transit Center. Several San Francisco city departments reviewed the project's governance structure and project delivery methods with the aid of an expert panel, culminating in a report published in October 2019. The report concluded that the governance of the project should shift from the TJPA to a new agency and that the project should be newly pitched to the public as a project of regional importance due to its role as a link in a future regional rail network. References External links Proposed railway lines in California California High-Speed Rail Caltrain Underground commuter rail Proposed public transportation in the San Francisco Bay Area South of Market, San Francisco Tunnels in San Francisco