You cant get Dredge Building Material. i have destroyed the building over 200 times already for the past year and tried to interact with the building but nothing.
Is it bugged or just Insanly low drop rate?
Are you sure you're at the right building? (The South-East Dredge armoury)
I don't have the collection open, but the interact is there. https://imgur.com/a/8IgZD
Better get a wriggle on.
I believe it is on the left side when I did it but I also wasn't sure if it was random.