compromise that formed the current system: the California Street line from Cal Cable, the Powell–Mason line already in municipal ownership, and a third hybrid line formed by grafting the Hyde Street section of Cal Cable's O'Farrell-Jones-Hyde line onto a truncated Powell–Washington–Jackson line, now known as the Powell–Hyde line. This solution required some rebuilding to convert the Hyde Street trackage and terminus to operation by the single-ended cars of the Powell line, and also to allow the whole system to be operated from a single car barn and power house. Despite the changes, much of the systems infrastructure remained unchanged from the time of the earthquake. Rebuild By 1979, the cable car system had become unsafe; it needed to be closed for seven months for urgently-needed repairs. A subsequent engineering evaluation concluded that it needed comprehensive rebuilding at a cost of US$60 million (equivalent to $ million in ). Mayor Dianne Feinstein, who took charge of the effort, helped win federal funding for the bulk of the rebuilding job. In 1982, the cable car system was closed for the rebuild which involved the replacement of 69 city blocks' worth of tracks and cable channels, a rebuilding of the car barn and powerhouse within the original outer brick walls, new propulsion equipment, and the repair or rebuild of 37 cable cars. The system reopened on June 21, 1984, in time to benefit from the publicity that accompanied San Francisco's hosting of that year's Democratic National Convention. Recent history Since 1984, Muni has continued to upgrade the system. Work has included rebuilding historic cars, building brand new replacement cars, building a new terminal and turntable at the Hyde and Beach terminus, and a new turntable at the Powell and Market terminus. Between 2017 and 2019, the system received a second, but less extensive rebuild. Over the two-year project, Muni rehabilitated the cable car system's gearboxes, which had been in service since the last rebuild in 1984. The system was shut down in March 2020 to protect operators during the COVID-19 pandemic, as cable cars do not offer a compartment separating them from passengers (unlike Muni buses, which kept running). Limited service on all three lines resumed on August 2, 2021. Full revenue service began on September 4. On September 9, a valve failure caused the fire suppression system in the carbarn to activate, shutting down electric power to the powerhouse. Service resumed on