Idaho communities push for partial undergrounding of Hailey to Ketchum transmission line

Idaho Power representatives are working with three southern Idaho communities to figure out how to pay for the additional $10m it would cost to place a portion of a planned 12-mile, 138-kV power line underground.

As originally proposed, the project, which would provide a redundant source of power to the southern Idaho communities of Hailey, Ketchum and Sun Valley – currently served by a single radial transmission line – was estimated to cost between $350,000 and $400,000 per mile, or $4.2m to $4.8m, according to the project fact sheet.

Discussions about the preferred route, which are ongoing, are focusing on placing some three to four miles of the line underground. Undergrounding a portion of that line, depending on the final route selected, would increase the cost to $14.3m.

As regulated by the Idaho Public Utilities Commission (IPUC), Idaho Power must build its infrastructure in the most cost-effective manner possible, and “any entity in Idaho that requests anything outside of the standard overhead construction pays the difference,” an Idaho Power spokesperson told TransmissionHub June 28.

“The latest conclusion that everybody is looking at seriously as probably the best solution would be overhead for about nine miles from Hailey to just south of Ketchum, then underground from there” to the Ketchum substation on the Ketchum/Sun Valley border, the spokesperson said.

Such an alignment would comport with city ordinances in Ketchum, which prohibit the installation of new overhead power lines within the city limits.

However, the next hurdle to overcome would be how to pay the additional cost of undergrounding.

The utility is working with the cities of Ketchum and Sun Valley, and Blaine County, Idaho, which all have different permitting requirements and different funding options, including the possibility of utilizing three separate local improvement districts – one in each jurisdiction – to help pay for the additional costs.

In addition to the new transmission line, which would provide additional capacity for future growth as well as redundancy, the project will also involve upgrades to Wood River and Ketchum substations.

The utility expects to file applications for the necessary permits with Ketchum, Sun Valley and Blaine County in early 2014. The project will not require IPUC approval, the spokesperson said.

After that, the project schedule calls for acquiring the needed easements in 2015, and constructing the line in 2016.

The need for the line was initially identified in the Wood River (Idaho) Electrical Plan, which was developed through a collaborative process with Idaho Power and the Wood River Community Advisory Committee (CAC) in 2007.

Idaho Power is a subsidiary of IDACORP (NYSE:IDA).