Editing Flytoget (section)

===Challenges===
{{Main|Romerike Tunnel}}
[[Image:Lutvann.jpg|thumb|Lake [[Lutvann]] was partially drained due to construction problems during the digging of the [[Romerike Tunnel]]]]
The greatest challenge was the need to build the {{convert|14580|m|ft|adj=on}} [[Romerike Tunnel|Romerike railway tunnel]] – Norway's longest – beneath the geologically highly unstable [[Østmarka]] area between [[Etterstad]], close to Oslo Central Station, and Lillestrøm.<ref name=jbvstat45 /> During construction, in 1997, the water level in some lakes above the tunnel, including [[Lutvann]] and [[Nordre Puttjern]], sank dramatically. After the leaks were discovered on 3 February 1997, sanctions were imposed by the [[Norwegian Water Resources and Energy Directorate]] requiring the elimination of all leakages. At its worst, the tunnel was leaking {{convert|3000|L|impgal}} of water per minute.<ref name=romeriksporten>{{Cite web |url=http://www.regjeringen.no/nb/dep/sd/dok/NOUer/1999/NOU-1999-28/4/2/6.html?id=355320 |title=Særskilt om Romeriksporten |author=[[Norwegian Ministry of Transport and Communications]] |year=1999 |access-date=2008-09-13 |language=no |url-status=dead |archive-url=https://web.archive.org/web/20120329010543/http://www.regjeringen.no/nb/dep/sd/dok/NOUer/1999/NOU-1999-28/4/2/6.html?id=355320 |archive-date=2012-03-29 }}</ref>

[[Rhoca-Gil]] sealant was used in an attempt to fix the leaks, but failed to work properly. Not only did it not polymerise, and therefore failed to staunch the leaks, but it also poisoned its surroundings with [[acrylamide]]. Manual fixing with concrete became necessary; the fixing and cleaning up of the toxin delayed the building of the tunnel by one year.<ref name=romeriksporten /> Further complications arose due to conflicts between NSB Gardermobanen and the construction company, Scandinavian Rock Group, with the latter at one instance stopping work for three weeks while the parties quarrelled in court.<ref>{{Cite web |url=http://tekst.aftenposten.no/tekstcgi/tekst.cgi?stdsok=atekst&base=AFT97&q1=AFT9704140240 |title=NSB og SRG barket sammen i namsretten |author=[[Aftenposten]] |date=1997-04-14 |language=no }}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Reports have shown a lack of inspection and reporting procedures during incidents that should have been addressed – but were never taken seriously – in 1995. Construction of the tunnel caused damage to around sixty houses and an evaluation by the [[Norwegian Ministry of Transport and Communications|Ministry of Transport and Communications]] showed that NOK 500&nbsp;million was spent on fixing the leaks and claimed that this was to a large extent an unnecessary expenditure which  more efficient engineering procedures would have avoided. The report also criticised the administrative planning and organisation of the overall construction of the railway.<ref name=romeriksporten />

Airport Express Trains began operating as soon as the new airport (and the Lillestrøm to Gardermoen stretch of the new high-speed line) opened on 8 October 1998; however, for more than ten months they had to use the old Hovedbane (Trunk Line) between Oslo S and Lillestrøm, which restricted their frequency to just two trains per hour. Regular operations at full capacity, using the Romerike Tunnel, did not commence until 22 August 1999.<ref name=history />