Bridge over C&O Canal at Dam 4

This stop gate provides an opening for the canal to pass through a guard wall that extends from the abutment of Dam 4 to the adjacent hillside. Large beams stored in the winch house above the gate can be lowered into place to close the gate, if necessary, and hold water back behind it. This would be done if flood waters were getting into the canal behind the guard wall and stop gate so they could not flow through and damage to the canal below the gate and its guard wall. There are a number of stop gates on the canal and any such gate can be closed to hold water back when the water level in the canal below them is being drained or lowered for repairs.