MUMBAI, Nov. 25 -- A block of 20-23 hours at Parel seems to be imminent for removing the girders of the partially demolished Elphinstone Bridge over Parel and Prabhadevi railway stations. On Monday, railway engineers visited the spot under the partially dismantled road over bridge (ROB) at the Parel end to inspect the issues that need to be looked into before finalising the block period required for demolition. With certain portions of the overhead electric (OHE) cables, which supply 25,000 volts to trains, welded into the underframe of the bridge, sources said the most critical aspect was the bracket insulators and wires. "Removing and displacing these will be a time-consuming process," said a Central Railway (CR) official. There are two lines each on the fast and slow corridors and an extra line for siding (a short railway track section that branches off a main line) that pass under the over-100-year-old ROB on the CR portion. Each line has one or two bracket insulators welded onto the base of the bridge. Another official said that in this case, the OHE cable could not be slewed into the side and would have to be removed entirely. The average length of the cables runs into two to four kilometres, and they are joined using OHE masts (the tall grey poles seen on the sides of railway tracks) at regular intervals. "For this work, we might have to shift these OHE masts and other equipment to prevent any disturbance to the power supply once the demolition work is complete and construction of the new bridge begins," he explained. Considering the quantum of work, CR officials said they would require 23-24 hours, of which three to four would go into removing the OHE cables. The length of the bridge over the rail tracks on CR and WR is 132 metres, of which 61 metres pass through CR's jurisdiction. In the first phase, mega blocks will be undertaken over the CR lines, followed by the WR ones. Last week, when the demolition plans were first drawn up, CR and the Maharashtra Rail Infrastructure Development Corporation authorities were mulling three options. The first was a continuous single block of 20 hours at the site, during which period all local and outstation trains would be short-terminated at Parel or before it. This idea was initially relegated to the last option, as it meant cancelling several hundred train services that could possibly lead to a chaotic situation in the dispersal of passengers from Dadar railway station and put undue pressure on Prabhadevi station of WR. However, this is the plan that seems likely to prevail. The other potential plans include 15 blocks of four hours each to be carried out over the weekends, mostly at night. This could include a main block for a longer duration although it has not yet been finalised. The third option was a technical one that might require slewing the OHEs. Both these seem to be difficult to implement. Preliminary work on demolishing Elphinstone Bridge, an important east-west connector, began on September 10. The asphalt has been ripped up on the approach roads at both ends of the bridge, and paver blocks on the footpaths have been dismantled....