The area is approximately 300-m from the Rhine River, and groundwater is very shallow. As noted in another NCE article, the contractor constructed 15 dewatering wells when only 4 were approved. Additionally, the pumping rate being used was 750 m^3/hr, or nearly double the 450 m^3/hr it was pumping in December of 2008. Clearly the groundwater is one component of the failure, but it does not appear that there is sufficient evidence to say exactly what role of the groundwater was or if the shoring walls did in fact fail and lead to the collapse of the Cologne historical archives and the deaths of two people.
Early indications are that a collapse of a subway tunnel station still under construction was to blame for the sinkhole that destroyed Cologne’s Historical Archive, home to documents dating back to 922 A.D. More info after the break. (Photo by DPA via Spiegel Online)