PacifiCorp will dial back the output from Jim Bridger 1 and 2, rather than install pollution control equipment needed to comply with Wyoming's regional haze implementation plan.

The Wyoming Department of Environmental Quality agreed Aug. 23 to allow the utility to meet the state haze reduction rules with an alternative strategy that will limit the capacity factor for all four coal-fired units at Bridger to 76.3 percent, and allow the utility to forgo a capital investment of over $300 million to install selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR) equipment on units 1 and 2.

In a filing, known as a Reasonable Progress Determination, PacifiCorp said the annual cost of installing SCRs, SNCRs, and the Reasonable Progress (RP) Determination Assessment would annually cost $34.8 million, $9.4 million, and $2.1 million, respectively, using a depreciation schedule of 2037 for units 1 and 2.

"Considering the expected remaining useful life of the Jim Bridger plant, neither Jim Bridger Unit 1 nor Unit 2 is expected to operate long enough to justify SCR or SNCR installation," the utility said in the filing.

Under the RP Reassessment, the potential annual CO2 emissions from the Bridger plant would be 16.8 million tons per year, a decrease of 1.7 million tons/year as compared to current operations. The plant would use 8.6 million tons of coal annually using a capacity factor of 76.3 percent, compared to 11.3 million tons annually currently.

PacifiCorp's plan will reduce average annual mass emissions of haze-causing sulfur dioxide plus oxides of nitrogen by nearly 20 percent.

The plan sets a monthly "block-pound-per-hour" of NOx and SO2 emission limits for all four units, according to the filing with DEQ, and set a 12-month rolling limit of 17,500 tons.

"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.

Installation of SCR controls on Jim Bridger units 3 and 4 were completed in 2015 and 2016; units 1 and 2 were scheduled to have the equipment installed in 2022 and 2021, respectively.

"We believe this is a compelling case for compliance with regional haze rules, in a meaningful way across a range of environmental concerns, at a much more reasonable cost for our customers," Dave Eskelsen, spokesman for PacifiCorp, told Clearing Up.

PacifiCorp continues to perform modelling for its 2019 integrated resource plan, which includes reviewing the economic costs and reliability issues associated with potentially closing some of its coal units early.

economic analysis released in December showed that roughly 60 percent of PacifiCorp's coal units could potentially be retired in 2022 and replaced with renewables or natural gas-fired generation (CU No. 1880 [14]).

Bridger Unit 1 appeared several times as part of a cluster of plants in Utah, Colorado and Wyoming that showed the largest potential benefits of early retirement.

Closing Naughton units 1 and 2 and Jim Bridger Unit 1 in 2022 would yield a benefit of $301 million in present value of revenue requirement.

Shuttering Naughton 1 and 2, Hayden 1 and Bridger Unit 1 in 2022 would create $307 million in PVRR savings.

Retiring Naughton 1 and 2, Hayden 1, Bridger 1 and Craig 2 in 2022 yielded $317 million in PVRR savings.

The 2019 IRP is scheduled to be filed on Oct. 18.