By Tony Romeo

HARRISBURG, Pa. (CBS) — Three companies are proposing to build a billion-dollar natural gas pipeline through Pennsylvania and other states to ship natural gas from the Marcellus Shale formation to mid-Atlantic markets.

Valley Forge-based UGI Corporation is one of the three companies that have announced a joint effort to develop and market an interstate natural gas pipeline.

A statement released by UGI says what will be known as the Commonwealth Pipeline will stretch 200 miles from Lycoming County in north-central Pennsylvania, south to access markets in the Philadelphia, Baltimore, and Washington, DC areas.

The pipeline, which will connect those markets to natural gas supplies in the Marcellus Shale region, is expected to interconnect with a number of other interstate pipelines along its route.

The head of UGI Energy Services says gas production in the Marcellus Shale formation has so far been limited by a lack of capacity with existing pipelines.

The new pipeline is expected to be placed in service in 2015.