Over 3200 high explosive bombs of all sizes were dropped on and around the viaduct. The German bomb disposal organisation estimated that approximately 380 (12%) of these failed to explode.
A number unexploded bombs were cleared between raids but local authority records did not make clear how many remained to be cleared by the end of the war.
A grid system and metal detectors, effective to 7m, were used to locate and record the position of unexploded bombs. The work was greatly aided in 1963 when pin sharp stereoscopic aerial photographs were released to the German authorities. Every bomb crater and small hole left by an unexploded bomb could clearly be seen. However, even with this meticulous approach a number of unexploded bombs remained undetected.
As late as 1984 a number of bombs were found during a routine check of the area. To the consternation of the local populace these unexploded bombs were buried only 1.5m deep and a few metres from footpaths that had been built around the viaduct!
A bureaucratic mixup had occurred and the whole area was rechecked. In July 1984 the Regional President came to witness the 75th (and final) defusing of a WW2 bomb. However, members of the Bomb Disposal Unit believe that there are still bombs that will (hopefully) remain undiscovered.