Wyoming Consumer Advocate backs Bridger coal plant retrofits

The Wyoming Office of Consumer Advocate (OCA) said Feb. 1 that it has recommended that Rocky Mountain Power (also known as PacifiCorp) be allowed to proceed with the installation of environmental improvements at Units 3 and 4 of the coal-fired Jim Bridger power plant.

The OCA filed testimony on Feb. 1 with the Wyoming Public Service Commission (PSC). Under air quality permits issued by the Wyoming Department of Environmental Quality (DEQ), Rocky Mountain Power (RMP) must either install the upgrades by the end of 2015 and 2016 for Units 3 and 4, respectively, or cease operation by those dates. The permits were issued under “Regional Haze” rules administered by the U.S. Environmental Protection Agency.

“Without these upgrades Jim Bridger units 3 and 4 will not be able to burn coal beyond the deadlines imposed by the DEQ,” said Bryce Freeman, Administrator of the OCA. “OCA reviewed the Company’s proposal to determine if less expensive compliance alternatives were available and concluded that the upgrades being proposed by the Company are the only way that RMP can comply with current emissions limits. No other technologies will provide the required level of emissions reductions.”

If the units were to cease burning coal:

  • there would need to be a possible conversion of the units to burn natural gas;
  • there would need to be retirements of the units and replacement with new gas-fired generation;
  • there would be a need for purchasing an equal amount of generation from the market; or
  • some combination of these alternatives.

“Our analysis shows that all of those alternatives would be more expensive and riskier than retrofitting the coal plants to be in compliance with the Regional Haze emission limits,” Freeman explained. 

The Bridger units provide electricity 85% to 90% of the year, also known as “baseload” capacity. “Converting the plants to burn natural gas and operating them as base load resources would be enormously expensive because of the amount of gas that would be required, even with current low gas prices,” Freeman stated.

Likewise, converting the units to burn gas and running them on a limited basis during the heaviest load hours, referred to as “peaking capacity,” would require RMP to obtain additional baseload resources, the OCA noted.

Replacing the coal generation with completely new gas-fired generation would require comparatively less gas because new gas-fired generators are more efficient than converted coal units, but would require a capital investment of a billion dollars or more, OCA noted.

Purchasing electricity from the open market over the remaining 24 years that the units are planned to be in operation could be more or less expensive than retrofitting the units as proposed. “Relying on the market to replace the capacity of these units comes with its own set of risks,” Freeman said.

Freeman added: “I am not enthusiastic about recommending PSC approval of an investment that I know will impact customer utility bills in the future. But, it would be worse to oppose the investment and force RMP to replace the Bridger units with some other generation resource or power purchase that would very likely cost customers more than the upgrades being proposed.”

This action covers SCR for two of four Bridger units

Rocky Mountain Power began this Wyoming PSC case, covering new selective catalytic reduction (SCR) systems for NOx control at the two Bridger units, in August 2012. Chad Teply, vice president of resource development and construction for PacifiCorp Energy, said in that opening testimony that the retrofits are driven by EPA’s proposed action on Wyoming’s Regional Haze State Implementation Plan (SIP) as it pertains to NOx. EPA recommends approval of the SCR and low NOx burner installations on Jim Bridger Units 3 and 4 as Best Available Retrofit Technology (BART). EPA’s proposed action on Wyoming’s Regional Haze SIP related to SO2 recommends approval of the state’s SIP in this regard, which incorporates the established emissions limits assigned to the Jim Bridger Units 3 and 4 scrubbers.

PacifiCorp believes that its emissions reduction projects completed to date on Jim Bridger Units 3 and 4 are consistent with the EPA’s Mercury and Air Toxics Standards (MATS). The company will be required to take additional actions to reduce mercury emissions through the installation of controls and use of reagent injection at Jim Bridger 3 and 4 to otherwise comply with the final rule’s standards. Budgeted costs for these additional actions have been incorporated into the financial analyses supporting this CPCN application.

The Jim Bridger plant consists of four coal units which are two-thirds owned by PacifiCorp and one-third co-owned by Idaho Power. The plant is operated by PacifiCorp Energy. Unit 3 began operation in 1976 and Unit 4 followed in 1979. Unit 3 and Unit 4 have nominal net generation capacities of 523 MW and 530 MW respectively, of which the corresponding PacifiCorp two-thirds shares are 349 MW and 353 MW.

Both units are configured with Alstom (formerly Combustion Engineering) controlled circulation, tangentially fired, pulverized coal boilers and General Electric steam turbine-generators. Both units are configured with closed loop circulating water cooling systems that include mechanical draft cooling towers and electrostatic precipitators (ESPs). Unit 4 was originally equipped with a sodium-based wet flue gas desulfurization (FGD) system, and Unit 3 was retrofitted in 1985 with a sodium-based wet FGD.

The plant is adjacent to PacifiCorp’s and Idaho Power’s co-owned Jim Bridger mines, which supply about 6 million tons per year of sub-bituminous coal to the plant along a 2.4-mile long, 42-inch wide overland belt conveyor. An additional approximately 3 million tons per year of sub-bituminous coal is delivered to the plant from other mines in southwestern Wyoming via rail or truck.

Since the Jim Bridger plant is primarily a mine-mouth facility, fuel supply design flexibility has been focused on potential fuel quality ranges from the mine. In addition to existing primary and secondary coal sources, a point of major import to the coal industry is that PacifiCorp is incorporating design parameters into the Jim Bridger SCR systems to accommodate Powder River Basin (PRB) coals to allow future PRB coal switching to remain a viable long-term planning alternative with limited modifications required to the SCR systems.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.