Report on serious incident in the Oppsal tunnel 16 July 2014
Railway report 2015/06
On 16 July 2014, at approximately 1108, metro train 307 on the Østensjø line collided with a set of geotechnical drilling rods in the tunnel by Oppsal station. Mesta AS was in the process of carrying out ground surveys on assignment for Dr. Ing. Aas-Jakobsen AS / Geovita AS relating to Sporveien Oslo AS's upgrading of the line.
In total, boreholes were to be drilled in approximately 100 places, from Godlia towards Mortensrud, and this was one of 25 boreholes that were considered to lie outside the track route. The point at which the borehole was drilled had been planned on the basis of the expectation that the whole length of the Oppsal tunnel was overlaid with rock. The plan was to drill 3 metres into hard rock. It was assumed that the distance down to the tunnel was greater than this, so no maximum depth was set for the drilling. As the ground where the borehole was drilled turned out to consist entirely of loose material, the bore went through the tunnel ceiling and onto the track, very close to the electrified rails where a metro train carrying passengers collided with the drill rods. The first calls that were made to the police indicated that there had been an explosion in the metro tunnel. The passengers described hearing a bang from underneath and alongside the metro train, and sparks were observed. The lights failed and many passengers were frightened by the incident.
In its investigation of the incident, the Accident Investigation Board Norway (AIBN) has concluded that the parties involved had different expectations relating to the information flow in the project. There is also reason to point out that the project's risk assessments were inadequate. The AIBN submits one safety recommendation as a result of the investigation, concerning control of contractors when work is to be carried out on or near the tracks, and the supporting documents that are available to them for the work to be carried out.
Safety recommendation
Safety recommendation JB No 2015/06T
On 16 July 2014, a metro train collided with some drilling equipment that had come down through the tunnel ceiling in the Oppsal tunnel. The drilling equipment was used in connection with geotechnical surveying above the tunnel relating to the upgrading of the Østensjø line. Those involved in the project had failed to identify the risk of drilling through the tunnel ceiling in advance, and no measures had therefore been implemented to ensure the safety of train traffic.
The AIBN recommends that the Norwegian Railway Authority ensures that Sporveien T-banen AS, in its control of contractors, has a process in place to ensure that risk factors in connection with work on or near tracks are addressed, and that suppliers are provided with supporting information of relevance to the work to be carried out.
Facts
| Location | The Oppsal tunnel, Østensjø line |
| Occurrence date | 16.07.2014 |
| Train No | 307 |
| Type of Transportation | Metro |
| Type of occurrence | Collision |
| Rolling Stock | Multippel Unit (MU) |