German prosecutor officials are investigating possible criminal falsification of construction survey data on Cologne’s roughly $550 million North-South urban rail project, scene of a building collapse last March.

In parallel, diaphragm walls being used in construction of one the line’s underground stations have been found to be about 80% short of specified dowel bars.

These, as yet unconnected, findings recently emerged from investigations into the March 3, 2009 collapse of the city’s historical archive building. The building was undermined when a section of railroad tunnel under construction in nearby Waidmarkt collapsed. No official cause for the tunnel failure has yet been revealed.

The quality of the contractror’s records was “absolutely unacceptable,” says Herbert Bodner, Chairman of Bilfinger Berger A.G., Mannheim, in a Letter to Cologne’s mayor, Jürgen Roters. Bodner adds: “Despite the inaccurate protocols, no geometric deviations have occurred in the diaphragm walls that would endanger their stability”.

Bilfinger Berger is in the project’s construction joint venture with Wayss & Freytag Ingenieurbau A.G., Frankfurt, and Ed. Züblin A.G., Stuttgart. The joint venture has completed around 80% of its contract with the city’s transportation authority Kölner Verkehrs-Betriebe AG (KVB) to build 3.3 km of twin tunnel and seven stations, says a spokesman.

A number of joint venture supervisors are being investigated over the records, says the spokesman. Police carried out house searches late last month. Suspicions were raised when survey data of diaphragm wall excavations were found to be identical for different locations.

Bodner, in his letter, also decries the omission of dowel bars between diaphragm wall panels. "For me, as an engineer, the failure to install shear inconceivable and something that I have never seen in all my years of professional experience" he writes.

Missing steel bars was first spotted at the Waidmarkt collapse pit late last month, according to KVD. Exploratory cut-outs of diaphragm walling at Heumarket station, started on 10 February, found only 17% of the required steel bars in places, add KVB officials.

The station box has been declared structurally adequate sound. But the joint venture is planning “precautionary measures” in case the ground water should rise, increasing wall pressures.

While Cologne’s prosecutor continues investigations, construction along the line is going on except at the Waidmarkt collapse site. There, the city workers and volunteers are painstakingly recovering thousand of valuable records from the archive ruins.

Over 80% of the records have been recovered but over a third have been severely damaged, according to city officials. They estimate the cost of restoring the archive at up $550 million.