▁over ▁the ▁Nem unas ▁river ▁started ▁on ▁ 4 ▁February ▁ 1 8 6 2 . ▁The ▁tunnel ▁started ▁operating ▁in ▁spring , ▁ 1 8 6 2 . ▁ ▁Operation ▁history ▁The ▁tunnel ▁was ▁opened ▁for ▁traffic ▁in ▁ 1 8 6 2 . ▁It ▁was ▁on ▁the ▁L ent var is ▁- ▁Ka unas ▁- ▁Vir bal is ▁branch ▁towards ▁Pr uss ia , ▁of ▁the ▁Saint ▁Petersburg - W ars aw ▁railway . ▁The ▁tunnel ' s ▁gauge ▁was ▁re built ▁to ▁standard ▁gauge ▁by ▁the ▁Germ ans ▁during ▁World ▁War ▁I . ▁The ▁Ka unas ▁tunnel ▁was ▁bom bed ▁by ▁the ▁retre ating ▁armed ▁forces ▁of ▁Germany ▁on ▁ 3 0 ▁July ▁ 1 9 4 4 . ▁The ▁biggest ▁explos ion ▁de formed ▁a ▁ 1 0 0 - met re - long ▁section ▁of ▁the ▁tunnel . ▁The ▁Soviet ▁army ▁re built ▁the ▁tunnel ▁in ▁ 1 , 5 ▁months ▁later ▁in ▁ 1 9 4 4 . ▁The ▁explos ions ▁changed ▁the ▁hydro log ical ▁condition ▁of ▁the ▁tunnel . ▁ ▁Water ▁began ▁to ▁de form ▁the ▁tunnel ▁in ▁ 1 9 4 7 - 1 9 4 8 . ▁Minor ▁reconst ruction ▁was ▁carried ▁out ▁in ▁ 1 9 4 9 . ▁A ▁train ▁accident ▁occurred ▁in ▁the ▁tunnel ▁in ▁ 1 9 6 3 . ▁It ▁was ▁determined ▁to ▁leave ▁one ▁rail ▁track , ▁instead ▁of ▁two ▁in ▁ 1 9 6 4 . ▁Pass enger ▁locomot ives ▁were ▁completely ▁replaced ▁by ▁electric ▁locomot