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.
The proposed railway tunnel will link Spain and Morroco underneath the Straits of Gibraltar. The depth of the straits ranges from 1,000-ft to nearly 3,000-ft. To put that in perspective, the English Channel is only 150-ft deep, and the Chunnel is another 130-ft below the sea floor. (Photo by chodaboy)