Just days after Williams reached the finish line on its Atlantic Sunrise project, Transcontinental Gas Pipe Line Co. (Transco) has secured 15-year commitments for 100% of the proposed Leidy South expansion, another Marcellus and Utica shale takeaway project designed to serve East Coast markets.

Williams said Tuesday it has binding commitments from Seneca Resources Co. LLC and Cabot Oil & Gas Corp. for the full 580,000 Dth/d of designed capacity on Leidy South, which could start up by the end of 2021.

The project, comprising compression and looping of existing Transco facilities in Pennsylvania, would further expand the pipeline’s ability to deliver Northeast production volumes from the Leidy Hub and Zick interconnects to points downstream in its Zone 6 market area.

“Since 2013 the Transco pipeline’s design capacity has grown by 62%, while its Marcellus takeaway capacity has increased by approximately 3 Bcf/d,” said Williams’ Frank Ferazzi, senior vice president (SVP) of the Atlantic-Gulf operating area. “The Leidy South project allows Williams to continue to grow our strategic footprint in the gas-rich Marcellus region, creating a unique opportunity to expand Transco by leveraging recent expansions on Williams’ Northeast Gathering & Processing assets in Pennsylvania.”

“This and future takeaway capacity helps Williams — and our customers — capitalize on our extensive gathering system, optimizing connectivity with producers strategically positioned throughout the basin, and demonstrating mutual growth,” added Williams SVP Jim Scheel, who heads the Northeast Gathering & Processing operating area. “Projects like Leidy South are a natural [byproduct] of that growth, providing producers with a single, integrated Williams solution to connect abundant, cost-effective Appalachian natural gas supplies with premier consuming markets located all along the East Coast.”

Cabot, an anchor shipper on the Atlantic Sunrise expansion, revealed in an operational update Tuesday it has 250,000 MMBtu/d of firm capacity on Leidy South, a commitment that “provides further visibility into the company’s ability to deliver longer-term growth at attractive netbacks,” according to CEO Dan Dinges.

Earlier this year, Seneca parent National Fuel Gas Co. announced a deal to commit to 300 MMcf/d of firm transportation on a Transco expansion targeting the Zone 6 market area in the New York City region, a move to hedge against the regulatory risks looming over its long-delayed Northern Access natural gas expansion project.

Cabot, a backer of the embattled Constitution Pipeline, is also no stranger to regulatory setbacks.

The 10,000-mile Transco pipeline network, the nation’s largest-volume interstate natural gas pipeline system, spans 1,800 miles from South Texas to New York City, reaching markets in 12 Southeast and Atlantic Seaboard states.

Williams said it plans to initiate the pre-filing process for Leidy South with the Federal Energy Regulatory Commission this month.