Wyoming Power Plant Gets New Emissions Compliance Path
Published Date: 6/8/2026
Proposed Rule
Summary
The EPA is updating air pollution rules for Wyoming’s Dave Johnston Power Plant Unit 3 because the company no longer agrees to shut it down. Instead, the EPA is revising how the plant controls nitrogen oxide emissions to keep the air cleaner. People can comment on these changes until July 23, 2026, and the updates could affect how the plant operates and spends money on pollution controls.
Analyzed Economic Effects
3 provisions identified: 1 benefits, 1 costs, 1 mixed.
EPA Cost Findings for NOX Controls
The EPA re‑ran the cost analysis for post‑combustion NOX controls at Dave Johnston Unit 3 and reports annualized costs of $1,810,782 per year for SNCR and $9,980,337 per year for SCR using a 20‑year life (or $8,862,953 per year for SCR using a 30‑year life). Based on the revised baseline and visibility modeling, the EPA proposes to find SNCR and SCR are not cost‑effective compared to the visibility improvement they would deliver.
Plant Closure Withdrawn; New NOX Limit
The EPA proposes to withdraw the enforceable requirement that Dave Johnston Unit 3 permanently cease operations by December 31, 2027, and remove the interim 0.28 lb/MMBtu (30‑day rolling average) NOX limit tied to that closure. Instead, the EPA proposes a revised NOX BART limit of 0.23 lb/MMBtu (30‑day rolling average) and an associated compliance date for Unit 3.
Baseline Emissions Adjusted to Existing Controls
The EPA is using a post‑combustion control baseline that includes the low‑NOX burners with overfire air (LNB/OFA) installed in 2010, resulting in a baseline NOX level of 2,076 tons per year and an annual average rate of 0.22 lb/MMBtu for the BART cost analysis. The Agency explains this baseline reflects demonstrated emissions after the 2010 controls and will be used in calculating costs and visibility benefits.
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