First try Google Scholar. The first time you use Google Scholar it's a good idea to customize it so you can access Wentworth materials. Click on settings, library links, and add Wentworth. Enter the term cologne archive collapse. I've attached one article that looks particularly useful below.
There are some articles on the internet that claim the Reine River broke through and undermined the foundation of the building. Other articles point to the possibility of corruption. You could also take a look at the Construction Management Research Guide (Business Ethics tab).
You can go to the Internet and search for the publication ENR. Enter the term Cologne. You will need the library password to access the articles or a reference librarian can email them to you. Contact us if you decide you need them. You can call 617-989-4040 from the outside to reach us.