the western headhouse incorporates a granite element similar to the adjacent State Street Block, while the sloped eastern headhouses include bricks matching the adjacent Marriott Long Wharf. The lower part of the platform walls are covered by Currents (originally Untitled Wall), a pair of -long black-and-white tile mosaics by Jun Kaneko. They were installed as part of the Arts on the Line program. Water issues Since the 1996–2003 reconstruction, Aquarium station has been plagued by water leaks, which may have been caused either by the renovation or by adjacent Big Dig construction. (Leakage was noticed in the station even before its 1906 opening, albeit at a much smaller rate.) The location of the east headhouse near Boston Harbor has resulted in additional flooding during king tides and storm surges. On January 4, 2018, the station was flooded with ocean water associated with the surge from the January 2018 North American blizzard. It was closed "indefinitely" but ultimately reopened the next day. A nor'easter that March caused flooding that again briefly closed the station. These floods damaged elevators and escalators at the station, leaving them out of service for months. In 2019, the MBTA began using temporary barriers to control flooding at Aquarium during storms. A permanent fix for both leaks and flooding is estimated to cost $20–40 million. A 14-day closure of the Blue Line for maintenance work in May 2020 included drainage work at Aquarium. A $1.7 million project, which took place from August 2020 to March 2021, added supports for aluminum planks that can be temporarily installed during high water events. Central Station proposal The North–South Rail Link (NSRL) is a proposed railway tunnel which would link the two halves of the MBTA Commuter Rail system between North Station and South Station under downtown Boston. It was originally proposed to run deep beneath the Central Artery, passing under Aquarium station at a depth of . In 2003, the MBTA released the Major Investment Study/Draft Environmental Impact Report, which considered two-track and four-track NSRL designs with or without an intermediate Central Station. The station would have platforms between State Street and Broad Street. It would have four headhouses—two just north of Milk Street, and two just south of India Street and East India Row—plus a direct connection to Aquarium station. The report estimated that adding Central Station would increase commuter rail ridership by between 3,500 and 12,800 daily trips