Colorado air‑quality officials and GCC representatives briefed the State Land Board on Regulation 27 (GEM rules) and the results of the first GEM‑1 audit cycle.

CDPHE staff explained GEM 1 covers energy‑intensive, trade‑exposed manufacturers and requires five‑year third‑party audits to establish an emissions intensity benchmark and identify best available emissions control technology and energy best management practices (BMPs). Facilities that meet the GEM 1 audit determination must then meet an intensity limit and achieve an additional 5% reduction; only then can CDPHE impose mass‑based limits beyond that floor.

GCC Rio Grande (Pueblo) was determined to be operating at best‑available control levels and satisfies the BMP requirement through its Industrial EnergyStar certification. GCC said it has converted the plant to produce a 1L limestone‑blended cement (reducing CO2 per ton from ~725 kg in 2021 to ~677 kg in 2024), uses roughly 20% alternative fuels (tire‑derived fuel, chipped railroad ties) and is studying higher alternative‑fuel blends, supplementary cementitious materials and carbon capture pathways. CDPHE noted some fuel‑switch scenarios (e.g., full natural gas substitution) remain cost‑prohibitive by standard federal social‑cost‑of‑carbon criteria.