The 172 MW coal-fired plant is located against the steep canyon walls of the Castle Gate Canyon and does not have the available room to install baghouses and other features needed to meet federal requirements, according to the report.
Carbon Power Plant is Utah’s oldest coal-fired power station and was slated for retirement in several years. According to the report, Rocky Mountain Power decided to decommission the plant several years ahead of scheduled because of the lack of practical options to achieve compliance at the power plant.
The Idaho Public Utilities Commission granted the company's request to transfer the plant's remaining balance and accumulated depreciation into a deferred account and establish a regulatory asset to recover costs after the plant is retired in April 2015 and through final decommissioning in 2020.
Idaho's share in the amount to be recovered from customers will be based on the amount of generation allocated to Idaho a calendar year before the date the plant is removed from service. The impact on customer rates will be minimal, the company maintains, because the expense will be spread over the remaining depreciable life of the plant through 2020.
Rocky Mountain claims it has spent nearly $8 million in environmental compliance expense. Idaho's share is expected to be about $479,000.