IUC adopts new rules to minimize transmission project impacts on Iowa landowners

The Iowa Utilities Commission (IUC) has adopted new rules that will minimize impacts of large-scale electric transmission lines planned in Iowa. The rules took effect July 29, and today the IUC sent a letter to the Midcontinent Independent System Operator (MISO), the electric grid operator that serves a majority of Iowa, which is currently reviewing competitive proposals for new transmission lines. 

The revised IUC rules govern the electric transmission line franchise process under 199 Iowa Administrative Code (IAC) chapter 11 and set new safety standards in the Iowa Electrical Safety Code, 199 IAC chapter 25, for lines operating at a maximum voltage of 170,000 volts or greater. The change will apply only to petitions filed after January 1, 2027. 

The IUC initiated the rulemaking on March 5 with MISO Tranche 2.1 long-range transmission planning projects serving as a catalyst. The 765 kV lines included in Tranche 2.1 represent the largest scale of transmission infrastructure ever built in Iowa and were identified by MISO to serve as an efficient backbone for the region.

The new rules address safety and technical issues and set restrictions on noise, electric field strength, and guy wires:

• 25.6(1) - Establishes an audible noise limit of 55 decibels for more than 50% of a one-hour measurement period, taken at the edge of the total combined right-of-way. 
• 25.6(2) - Limits the electric field strength to no more than 6,000 volts per meter when measured one meter above the ground anywhere within the right-of-way. 
• 25.6(3) - Prohibits transmission structures supported primarily by guy wires from being constructed on crop and pasture land unless an agreement with the landowner specifically allows such structures.  

The letter to MISO encourages the grid operator to consider Iowa’s rules when awarding Tranche 2.1 projects. 

“We believe that evaluating proposals according to these standards can ensure MISO’s competitive process will be effective, the most viable project will be chosen, and the final selection will be aligned with Iowa’s regulatory environment,” the IUC’s Commissioners said in the letter.

The IUC gathered stakeholder comments during the rule review period and made revisions according to that feedback. A public hearing on the proposed rules was held on April 29, and the IUC issued an order adopting the amendments on May 19.