As a habitat, that area is probably gone for good.

Or at least it will be soon. If you study the population over a few years time, you would probably notice a shift in the age class structure. Fewer and fewer young individuals would be found, indicating that fewer of them are born. That's not the problem, it's a symptom. The cause of this could partially be roadkills, collecting and intentional killing (all associated with human presence), but it's more likely that the food source has been knocked out. If that food source is amphibians, this would happen by degradation or destruction of their spawning pools in the area and that's something that occurs far more often than not, when new urban areas are built.

Just sell the extra offspring as pets or food, or euthanize them. But releasing them, no matter how well-meaning it is, can introduce pathogens into a remaining wild population and help deplete an already dwindling food supply and is not going to help.