norwegian kilometre railway tunnel norway oslo longest railway tunnel norway forms section double track electrified permitting speeds kilometres hour mph construction started plans open rest oslo airport october lakes open august leaks increased cost tunnel nok billion nok billion main contractor tunnel originally owned owned tunnel allows long distance regional bypass old line reducing journey times oslo minutes background tunnel constructed high speed runs oslo oslo airport tunnel makes kilometre section station built bypass dates despite older line double track capacity reached limit combination trains making stops allow higher speeds decreasing travel time minutes decision build taken october opening planned years later october alternative airport site proposed south west oslo chosen necessary airport express train planning documents recommended construction proceed ease traffic congestion north oslo tunnel trains including airport express regional express trains continue local trains line north use tunnel use limited freight trains commuter trains stops route construction construction started august tender won collaboration original contract price nok million average man years expended construction work involved removal million tonnes rock excavation points located oslo border outside tunnel kilometres long cross section making longest tunnel norway opened second longest opening road tunnel allows speeds mph slope upwards provides natural direction horizontal ventilation system needed work opposite direction supplemented vertical ventilation shafts tunnel metres metres ground deepest vicinity trains tunnel capable minimum speed kilometres hour mph tunnel overhead wires railway electrification tunnel needed pass recreational area east oslo geology area unstable ideal tunnel boring pressure completion coincide opening new airport resulted tunnel excavation proceeding maximum speed adequate measures exclude water resulted leaks houses route tunnel damaged water levels lakes reduced including lakes damage discovered february legal actions initiated requiring measures halt worst rate tunnel litres imp gal gal water minute process stop leaks investigation revealed contain toxic substance called caused health problems tunnel workers removal replacement concrete resulted additional delays addition extensive permanent pumping system installed restore maintain lake levels leaks cleaning contamination delayed tunnel completion year finally opened august entire process complicated conflicts retrospective surveys showed lack control reporting procedures incidents addressed taken seriously compensation paid approximately houses damaged result tunnel construction evaluation showed nok million spent fixing leaks report claimed large extent waste money resulting inefficient engineering procedures report criticized planning organization construction entire railway total extraordinary additional costs tunnel totaled nok billion delay new airport opened october airport express trains started operating immediately airport onwards tunnel finished trains required use old trunk line diversion express trains switched completed section new oslo airport regular operations started august
Romerike Tunnel