SUMMARY: In this document, EPA is finalizing the Clean Air Mercury Rule (CAMR) and establishing standards of performance for mercury (Hg) for new and existing coal-fired electric utility steam generating units (Utility Units), as defined in Clean Air Act (CAA) section 111. The amendments to CAA section 111 rules would establish a mechanism by which Hg emissions from new and existing coal-fired Utility Units are capped at specified, nation-wide levels. A first phase cap of 38 tons per year (tpy) becomes effective in 2010, and a second phase cap of 15 tpy becomes effective in 2018. Facilities must demonstrate compliance with the standard by holding one ‘‘allowance’’ for each ounce of Hg emitted in any given year. Allowances are readily transferrable among all regulated facilities. Such a ‘‘cap-and-trade’’ approach to limiting Hg emissions is the most cost-effective way to achieve the reductions in Hg emissions from the power sector.