Spire Inc. has officially filed at FERC to build its 400,000 Dth/d Spire STL Pipeline, a project planned to tap into the Rockies Express Pipeline LLC (REX) to serve the St. Louis market.

According to a notice filed to the project docket [CP17-40] this week, Spire plans to construct 59 miles of 24-inch diameter pipeline while acquiring and modifying seven miles of the existing Line 880 currently owned by Laclede Gas Co.

The $220 million project would interconnect with REX and run south through Scott, Greene and Jersey counties, IL, and St. Charles and St. Louis counties, MS.

St. Louis-based Spire, which operates natural gas utilities serving 1.56 million customers in Missouri and Alabama, formerly did business as the Laclede Group before changing its name last year.

The company announced an open season for the Spire STL Pipeline last summer.

Management at REX parent Tallgrass Energy Partners LP remarked last year on the growing interest from end-users in tapping the capacity available through its 800 MMcf/d Zone 3 east-to-west expansion, which went fully into service last month.

The 1,713 mile REX stretches from Ohio to Colorado and went into service in 2009. After later being modified to accommodate east-to-west flows, the pipeline has become a major takeaway route for constrained production out of the Marcellus and Utica shales.

REX’s total designed east-to-west capacity out of the Appalachian Basin currently stands at 2.6 Bcf/d and has been running at or near 100% usage, according to NGI‘s daily REX Zone 3 Tracker.