Three investors are backing a 349-mile underground transmission project being developed by Direct Connect Development Co. LLC that will run along the route of an existing railroad, linking Iowa and Illinois.

Copenhagen Infrastructure Partners K/S, Jingoli Power LLC and Siemens Financial Services Inc. are investing in the SOO Green Renewable Rail project, a 2,100-MW, 525-kV high-voltage direct current transmission line which will run from Mason City, Iowa, to the Chicago metropolitan area, linking the Midcontinent ISO and PJM Interconnection markets.

"The successful deployment of this HVDC technology along railroads will create a market segment that doesn't exist today, and [Direct Connect Development] believes that the SOO Green project will set the standard regarding how transmission lines are developed and constructed in the U.S.," Direct Connect Development CEO Trey Ward said in a March 11 news release.

The transmission line will allow "a large number of renewable energy buyers and sellers to enter into standard transactions," Direct Connect Development said, adding that the environmental impact of the project will be limited due to boring under sensitive habitats.

According to project developers, the SOO Green line is the first to adopt the rail "co-location model" used to build the U.S. fiber optic system. Most of the line will run alongside track owned by Canadian Pacific Railway Co.

Siemens will be responsible for the project's system design and for its engineering and installation, including the commissioning of HVDC converter stations.