The position of a rail tunnel was not marked on plans used by the piling contractor, developer or local authority involved on the project that damaged the tunnel near Old Street in London last year, according to a Rail Accident Investigation Branch (RAIB) report.
Piling operations 13m above the tunnel resulted in two augers failing through the tunnel crown and landing on the tracks on 8 March last year after the consultation process failed to involve Network Rail.
According to the report, more than half of the planned piles for the site by consultant Elliott Wood Partnership and installed by All Foundation would have intersected with the tunnel because its position was not shown on the site plan, or on any map available to either the developer or the local planning authority.
The incident occurred on the second day of piling work for the foundations for a new seven storey development. During work on the fifth pile, the auger broke through the cast iron lining of the Moorgate down line 420m north of Old Street station. The piling team were unaware that they had penetrated a tunnel and attempted to locate the missing sections of auger by dropping metal bars down the hole.
During its investigation RAIB discovered that the Elliott Wood had failed to identify that an obstruction found by an exploratory borehole by site investigation contractor Site Analytical Services was part of a railway tunnel.
RAIB has said that it is essential that clients and design teams should be aware of the importance of information shown on land ownership records; and those carrying out investigations for proposed developments should be aware that not all railway tunnels are shown on Ordnance Survey mapping.
The report also calls for the railway industry to be more proactive and provide information to organisations undertaking property-related searches; give detail on the location of railway tunnels and associated subterranean structures; and identify development work by third parties.