Smoke stacks 500-foot-high stacks that used to spew smoke now exhaust fewer particulates, but still emit carbon dioxide, other pollutants and water vapor. (Angus M. Thuermer Jr./WyoFile)

ROCK SPRINGS — PacifiCorp has chosen to throttle down production at the coal-fired Jim Bridger Plant rather than install expensive clean-coal technology there, and Wyoming regulators are now backing the plan.

Reducing the plant’s electricity output to 76.3% of capacity in lieu of spending $280 million on new pollution controls is the most economical and environmentally sound way to meet federal haze regulations, according to the company. 

The Wyoming Department of Environmental Quality agreed in a 17-minute hearing in Rock Springs on Aug. 23 that the company plan would meet the state-enforced federal haze-reduction rules. PacifiCorp presented its plan in a 25-minute hearing just before DEQ made its finding. 

“The state of Wyoming has determined that no additional controls are necessary,” said Amber Potts, DEQ’s State Implementation Plan and Rules Section Supervisor with the Air Quality Division. The agency found the plan provided “enforceable emission limits” to demonstrate reasonable progress toward state and federal goals to reduce haze pollution.

PacifiCorp will modify operations to meet emission standards, a move that will “effectively decrease the operating capacity of the plant,” according to DEQ documents. The reduced output will cut down on haze-causing pollutants, the regulatory agency wrote.

A supervisor negotiates the catwalks at the Jim Bridger Plant. Behind him new steel that’s part of expensive emission controls on one of the units stands out brighter than structures that make up the original plant. (Angus M. Thuermer Jr./WyoFile)

The move will reduce Jim Bridger Plant to 76.3% of its power output capacity, according to the company’s permit application to the DEQ. Existing permit restrictions already curb the plant’s potential to about 84% of its potential, according to WyoFile calculations from PacifiCorp documents. The new plan would reduce coal consumption by about 9.3% compared to current operations, according to WyoFile calculations.

The Clean Air Act, the federal Environmental Protection Agency’s Regional Haze Rule and Wyoming’s own State Implementation Plan require the company to address pollution from two of the four power-generating units in 2021 and 2022, the company’s environmental director James Owen said at the hearing. Already the company has added expensive haze pollution controls at the other two units and now faces deadlines to bring the rest of the plant into compliance.

But instead of building sprawling and towering additions to the Jim Bridger Plant at a cost of $280 million, PacifiCorp will take a less expensive route that will result in less power output. The plan, which includes “voluntary visibility emission limits,” calls for measuring overall plant emissions — and keeping them lower than what would be generated if the pollution control systems were constructed and the plant operated at a higher capacity.

Regional haze

Pollution-caused haze is a problem addressed by the Clean Air Act that seeks to protect special federal lands like national parks and wilderness areas. Sulfur dioxide and nitrogen oxides — typical power plant emissions — contribute to the formation of fine haze particles, according to the Congressional Research Service.

The EPA’s regional haze program has increased the average view from 90 to 120 miles in some western reserves like Grand Canyon National Park in Arizona, according to Harvard Law School.

PacifiCorp in February reassessed its regulatory obligations and arrived at “an innovative approach,” to the requirements, Owen told regulators in Rock Springs.

Throttling down the plant meets requirements to address costs, deadlines, non-air-quality impacts such as water use and supply and the useful life of the Jim Bridger Plant, Owen told regulators. It also provides “greater visibility improvements,” than would be attained by adding the pollution-control facilities to the Jim Bridger Plant, he said.

The mandate to maintain Class I airsheds in national parks and wilderness areas contributes to the difficulties Jim Bridger Plant has in meeting regional haze rules. (PacifiCorp)

PacifiCorp would establish monthly “block-pound-per-hour” NOx and SO2 emission limits for all four units, DEQ documents state. The plan would set a 12-month rolling limit of 17,500 tons for the two pollutants.

“This combined set of lb/hour and tons/year limits will be enforced in lieu of installation of selective catalytic reduction technology on Units 1 and 2, and will effectively decrease the operating capacity of the plant, thereby reducing its emission of haze-causing pollutants,” a DEQ document states.

The plan will result in “a very significant decrease in cost,” plus increased operational flexibility, Owen said. “It also allows for the company to accommodate renewables,” he said.

The plan will require increased monitoring, he said. “It requires us to be more vigilant.”

PacifiCorp’s plan is better than two other options — selective catalytic reduction technology and non-selective catalytic reduction technology — Owen said. The other options would cost the company and its consumers up to $280 million, he said, compared to between $4 million and $5 million under the proposal.

“Our proposal is better than both by a significant margin,” he told regulators.

DEQ officials said the agency would provide its endorsement of the plan to the federal EPA to show that the state’s implementation plan is meeting federal clean-air rules.

The technical numbers

PacifiCorp’s plan will reduce average annual mass emissions of SO2 plus NOx by nearly 20%, compared to controlling all four units with selective catalytic reductions, the company’s application states.

If the company were to install the addition haze pollution controls, running them would cost the company electricity, the application states. The new plan, however, would direct that power — “enough energy to power approximately 8,761 average homes” — to the grid, the application states.

Mothballed turbines, replaced after they wore out, sit on the plant floor. It is uneconomical to scrap them, a spokesman said. (Angus M. Thuermer Jr./WyoFile)

“Under the voluntary visibility enhancing emissions limits, the Jim Bridger Plant will be prevented from operating at an unrestricted capacity factor and will effectively be limited to a maximum average annual capacity factor of approximately 76.3%,” the application states.

Savings would cascade across plant operations. If the plant were to meet the haze requirements by adding new SRC pollution controls on the two units, it could burn 11.3 million tons of coal per year, the application states.

The plan also would reduce water use by 827 million gallons/year, some 2,540 acre-feet.

CO2 emissions also would decline, according to the application, from 18.5 million tons a year to 16.8 million tons, a 1.7 million ton drop, according to the application.

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“The proposed plantwide voluntary visibility enhancing emissions limits, as opposed to unit specific limits, are useful to provide the entire facility the flexibility to ‘load follow’ or accommodate intermittent influx of renewable energy into the western power grid which has larger scale environmental impacts in Wyoming and across the West,” the application states.

This is one of seven stories in WyoFile’s “Powering Down” special edition. Click the links below to read more:

Powering Down: Examining coal’s shaky ground from Jim Bridger

Jim Bridger: Lighting the country, laboring in the dark 

As coal’s future dims, uneasiness permeates Rock Springs

Life beneath the earth in Wyo’s only underground coal mine

Coal or free-market conservatism? Lawmakers choose coal

Changing blades


Angus M. Thuermer Jr.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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  1. FYI from comments raised by Powder River Basin Resource Council, Sierra Club, and National Parks Conservation Association:

    “The proposed monthly NOx and SO2 limits in the RP [regional progress] reassessment alternative equate to an overall capacity factor at Bridger of 76.3%. However, Bridger already operates at an annual capacity factor of around 55% based on 2018 EPA Air Markets Program Data (AMPD). . . . The RP reassessment not only rolls back the NOx emissions controls contained in the current Wyoming regional haze SIP, but would actually allow NOx emissions at Bridger to increase by almost 50% above current (2018) levels. Setting emissions limits above the current 2018 emission levels at Bridger does not protect or improve visibility, as is claimed under the RP reassessment proposal. “