The backed-up silt doesn't have to be as much of an environmental problem as some people want to believe. The Corps of Engineers can remove silt before breaching. As a one-time C. of E. hydrographic surveyor, my guess is that they could remove the silt along the old riverbed and banks before the breaching, and then remove more silt after it is high and dry to save $. Yes, I realize it would still be expensive. Hopefully, "they" already have it in their cost estimates.