Contractors will be using areas alongside it for access of large equipment, and they will do so very carefully. DWU will work closely with the Audubon Society to determine sensitive times and make schedule provisions to minimize any potential impact. They are used for lake level control. If there were a heavy flow and lots of debris, the stop logs could be damaged and possibly fail. The lake level would be drastically affected.
Concrete is much more reliable.
A swale in the new concrete cap would replace the stop logs and channel flows at lower lake levels. Lake levels could be lowered by use of a siphon. The lake level will not be affected by work on the spillway. The contractor will use coffer dams to work on approximately one-quarter of the area at a time. A coffer dam is placed a short distance in front of the permanent dam, and water is pumped out of the area so work can be performed.