MISO has selected Ameren Transmission Co. of Illinois (ATXI) to build a third transmission project stemming from the RTO’s long-range transmission portfolio. 

ATXI will oversee construction of the $273 million Denny-Zachary-Thomas Hill-Maywood (DZTM) 345-kV project in Missouri, part of MISO’s first, $10 billion long-range transmission plan (LRTP) portfolio. It’s the most expensive project MISO has evaluated for competitive selection. 

It’s the third time MISO has opted for ATXI after LRTP project solicitations. In December, MISO decided Ameren’s transmission arm will build a $23 million, 345-kV line segment from the Iowa-Illinois border to the Ipava substation in Illinois. (See MISO Selects Ameren, Dairyland to Build 3rd and 4th LRTP Competitive Projects.) 

Last year, MISO also awarded ATXI construction rights on the $84 million, 345-kV Fairport-Denny project, which extends to the Iowa-Missouri state border and links up with the DZTM project. (See MISO Selects Ameren to Build 2nd Competitive LRTP Project.)  

MISO’s DZTM selection announcement marks the final time MISO will compare bids on a competitive project from the first LRTP portfolio. Only five of the 18 projects were up for competitive solicitation. 

MISO said ATXI “conducted the most engineering and surveying of any developer, and its routes had the least environmental impact.”  

“It also more clearly detailed its construction activities and access plans, and showed how it could modify construction activities based on the in-service date of Denny substation,” MISO wrote in the selection report.  

MISO said it received six proposals from four developers, including two from ATXI and the remainder from LS Power, NextEra Energy Transmission Midwest and Transource Energy, with implementation costs ranging from $265 million to $486 million. MISO originally estimated project costs would exceed $500 million. ATXI was the only developer that offered to cap project costs, MISO said.  

“The selected proposal had a substantially lower cost than that of the next-closest developer,” Jeremiah Doner, MISO’s director of cost allocation and competitive transmission, said in a press release. “ATXI’s proposal also features strong cost containment, sound design, and robust operations and maintenance plans.” 

The DZTM project encompasses two new single-circuit 345-kV transmission lines at 162 miles and a new, 42-mile 345-kV conductor-only circuit that will share structures with an existing 161-kV line. The project will connect four substations. 

As with its Fairport-Denny project, ATXI’s DZTM proposal includes a partnership with The Missouri Joint Municipal Electric Utility Commission. ATXI plans to sell 49% of the project to the state utility agency before the project is placed into service.