 Not all dams can be replaced. Some do generate power or help control large rivers for navigation. And removing a dam can be controversial, especially when it's been a centerpiece of the community for a century or longer. But replacing a dam is often far less expensive than repairing it, especially with financial help from the state. And once the Rock Rapids are built, people tend to like them. Pine River expanded a city park next to its rapids. Mike Hansen says it's now a gathering place.