Duke Energy plans to replace two units at the Jocassee Dam with new turbines that will increase generating capacity by 50 megawatts, The giant turbines are 23 feet in diameter and weigh 150 tons. They will be hauled to the Jocassee power station using a 20-axle, dual-lane trailer that is about 250 feet long snarling traffic along the interstates and in the Lake Jocassee area this month.

The first unit is due to arrive near Salem on Aug. 9 and the second in early September. Both units will make the seven-mile trek on winding mountain roads to the lake shortly afterward. The units will be escorted by walk along personnel from Guy M. Turner, Inc., the contractor tasked with delivering the massive power generators.

Duke will notify residents before the units are moved and emergency vehicles may need to find alternative routes during daylight hours during the two-day move to the power station.

It will be the first upgrades to Jocassee units one and two since the station began commercial operation in 1973. Units three and four were upgraded several years ago. Each new unit will increase the maximum generating capacity from 170 megawatts to 195 megawatts.

They will also increase pumping capacity by 37 megawatts. The Jocassee power station operates as a pump storage power generator as well as a traditional hydro station. During periods of low demand the turbines are used to pump water back up into Jocassee from Keowee. The water is then released during periods of peak demand.

During installation Jocassee’s surface level will be at least four feet below full pond. The decreased levels are planned for September 2010 through May 2011.