Kokosing Dam was built by the U.S. Army Corps of Engineers for flood control, recreation and wildlife management.  Construction began in June 1970 and was completed in May 1972. The dam has an impervious, waterproof, core with earth-fill and rip-rap rock covering. The dam has an unregulated outlet structure, which means the water can not easily be regulated.  Under normal operation as much water flows out as is flowing in. Only when the inflow of water exceeds the amount the outflow structure can allow to pass through does the water back up into the lake. This prevents downstream flooding.  There is a 3.5 ft wide x 6.75 ft high outlet tunnel that carries the water from the outlet structure through the dam into the stilling basin, from there it flows through a channel to the end of government property, then the stream banks return to normal.  The minimum pool elevation is 1122.0 feet (above mean sea level) and a maximum flood control elevation of 1146.0 feet. After the water reaches this level it will flow through the spillway.  This dam has a 44.5 square mile drainage area.