In 2007, PJM Interconnection (regional transmission organization serving 51 million people in the 13 states of the District of Columbia) approved the construction of a new high-voltage transmission line from southwestern West Virginia to central Maryland designed to maintain reliability of the regional electric grid. The Potomac-Appalachian Transmission Highline Project (PATH) will help avoid the overload of existing transmission lines, which could threaten the electric power supply and lead to blackouts (August 14, 2003-largest blackout in US history). Allegheny Energy and American Electric Power (AEP) have announced a joint venture to build the project as a backbone expansion to the regional electric transmission system. The project’s estimated cost is $1.8 billion. Targeted for completion in 2013, the PATH project consists of a single 765-kilovolt (kV) transmission line from AEP’s Amos substation near St. Albans, W.Va., to a new substation near Kemptown, southeast of Frederick, Md.