STB greenlights UP's proposed 6-mile Arizona rail line

The Surface Transportation Board last week authorized Union Pacific Railroad's request to construct and operate a 6-mile rail line that will serve Commercial Metals Co. in Mesa, Arizona.

UP in June 2022 filed a petition to build the line in connection with the Pecos Industrial rail access and train extension project. The line will connect the Pecos advanced manufacturing zone to the UP main line west of the project area and provide service to Commercial Metals, as well as to future shippers, according to the STB decision document.

The board received no comments opposing UP's transportation service. In May 2023, the board's Office of Environmental Analysis issued a draft environmental assessment (EA) examining potential impact of UP's operation. The OEA discovered there had been significant ground disturbance and damage to National Register of Historic Places-eligible (NHPA) archaeological resources within the proposed right-of-way. Following briefing on the issue, the board was unable to reach a majority decision on whether a violation of NHPA had occurred, and the historic review process under NHPA resumed. On Feb. 27, 2026, OEA issued a final EA updating the environmental analysis and responding to comments received on the draft EA. 

In its final decision, the board determined that it would grant UP's petition subject to the environmental and historic preservation mitigation measures cited in the final EA.

Meanwhile, the STB also last week denied Metra's request to set conditions and compensation for the use of terminal facilities on three UP-owned rail lines over which the Chicago commuter railroad operates.

On Nov. 13, 2025, UP and Metra jointly reported that they had exchanged proposals regarding the conditions and compensation for Metra’s use of the UP lines and that, although they had not reached agreement, negotiations continued. On Dec. 1, 2025, Metra informed the board that while progress in the negotiations had been made, Metra officials didn't expect a final agreement would be made on remaining issues.

In its March 12, 2026, decision, the board determined that Metra's request was premature and set a 60-day negotiation period to expire May 12, after which UP and Metra should file a joint status report.