HARRISBURG — PPL Corp. wants to spend billions of dollars to build a 725-mile system of electric transmission lines that will bring energy from the booming Marcellus Shale natural gas fields to customers on the heavily populated eastern seaboard.

The Allentown-based utility said today the 500-kilovolt line would span Pennsylvania and reach New York, New Jersey and Maryland.

The company says the cost would exceed $4 billion and it’ll probably take a decade to build.

The proposal requires regulatory approval and the precise route hasn’t been determined.

A rough map produced by the company shows a line running from Pittsburgh through Pennsylvania’s rural northern tier and into New York.

A second branches south through the Susquehanna River corridor into Maryland. A third spur runs through the Lehigh Valley and into New Jersey.