Phases 3 and 4 2 Second Avenue Subway

as part of phase 3, station built @ second avenue , 23rd street (pictured).

three construction options evaluated during project s environmental impact study portion of line between 11th street , hanover square. 1 option known shallow chrystie option use cut , cover, while deep chrystie street , forsyth options use combination of tunneling earth pressure balance machines (epbms) , cut , cover. shallow chrystie option have used existing confucius plaza tunnel section between canal , division streets, , plan 1970s, there have been cross-platform transfer existing grand street station, transfer expected heavily used. however, option require digging sara delano roosevelt park east chrystie street not wide enough fit 4 tracks. under option, track connection built allow trains second avenue run via manhattan bridge north tracks allow service brooklyn. forsyth option curve below park forsyth street , station built under forsyth street, requiring 200-foot transfer passageway less convenient other options. deep chrystie option have second avenue subway run deeper underground, running underneath existing grand street station, mezzanine in between 2 stations. in order allow sufficient room stairways transfer second avenue line, grand street station widened have twenty foot wide platforms. no track connection built under option, , confucius plaza tunnel section not used subway service, instead might used ancillary subway facilities. currently, preferred option.

south of terminal @ hanover square, 2 tail tracks constructed through use of tbm allow storage of 4 trains. tracks built @ depth of 110 feet (34 m) under water street, allowing line deep enough tunnel under east river possible future extension brooklyn. cut-and-cover used build vent facility @ traffic island located @ water , whitehall streets.