Mount Pleasant staff brief council on transmission‑line plans, Rocky Mountain Power outage and leaking hydro gearbox

Mount Pleasant — City utilities staff briefed the City Council on engineering and schedule details for a planned Fairview–Mount Pleasant transmission line, ongoing voltage concerns tied to a Rocky Mountain Power mobile substation, and mechanical problems at the city’s hydro generator unit.

Shane, the utilities staff member who presented the update, said council approval of a $385,000 requisition to TRC will unlock engineering work. He described a recently held kickoff meeting and said the engineering firm indicated it could apportion fees roughly 60/40 between Fairview and Mount Pleasant so each jurisdiction pays its share. Shane said the construction target is “probably January, February, 2027,” but material lead times and grant Buy‑American requirements may extend the schedule; the project window discussed in the packet runs through December 2028.

On power quality, Shane said a temporary mobile substation installed by Rocky Mountain Power following an outage produced sustained low voltage on the city feed. He said the mobile unit later failed and service was switched back to the permanent transformer, but that the transformer’s load‑tap changer (LTC) had been locked at a fixed setting and wasn’t functioning as expected. That forced the city’s regulators to run near their limits to maintain acceptable voltages. Shane said Rocky Mountain Power will need to either restore the LTC or replace the transformer; the city has coordinated with neighboring jurisdictions and is asking Rocky Mountain Power for additional outages only as needed to remedy the issue.

On municipal generation, staff reported Unit 4 is back online but its gearbox is leaking oil on both drive and non‑drive sides. The gearbox was rebuilt previously; Shane said the unit was returned under warranty but that the vendor (National Gear Repair) has not yet responded to repeated contact attempts. A vibration specialist from PDM performed tests and reported the hydro and generator vibration appeared satisfactory, but PDM flagged “serious issues” with the gearbox and plans further analysis. Shane said on‑site replacement of failed seals would save disassembly and realignment costs (he estimated about $5,000 in avoided alignment costs if the vendor will send a technician to work on‑site), but shipping and some warranty conditions remain unresolved.

Shane said staff plans to continue pursuing the vendor for warranty work and, if unsuccessful, will consider calling in Energy Management or Prime Machine to diagnose and perform repairs. He said the gearbox is a longstanding vulnerable component for the hydro unit and that the city previously spent about $180,000 on a prior rebuild including high‑grade bearings.

Why it matters

Low distribution voltages and generator gearbox failures can affect local reliability, raise repair costs and require coordination with the regional utility and outside contractors. The transmission‑line engineering and substation siting are intended to reduce load on existing feeders and expand service capability to western growth areas; how the city manages vendor warranties and schedule risks will affect future costs and downtime.

Follow up and next steps

- Utilities staff will continue attempts to obtain warranty service from National Gear Repair and will report back with PDM’s analysis and repair options. - Staff will notify council and the public before any planned outages by Rocky Mountain Power related to corrective work. - Council was told TRC will provide a phased engineering schedule and that staff will track GL numbers for grant accounting.

Ending

Council members asked to be kept informed about vendor responses, vibration analysis results and any planned outages so they can relay information to affected residents and coordinate any necessary public notices.