[js1138]

There are concretes that will set under water. they were used extensively by the Romans. Nothing new.

[antaresequity]

I dont think the flooding of this hole is nearly as troublsome as the possible soil liquifaction between the pit and the river. If you create a low pressure area like this, and the ground water continues to migrate...where as it otherwise would be more or less static....other buildings might be troubled...the ones that lay between the pit and the river...