42 U.S.C. § 7651f — Nitrogen oxides emission reduction program

(a) Applicability. The moment a coal-fired utility unit becomes an "affected unit" for sulfur dioxide purposes under section 7651c, 7651d, or 7651h — or the moment a unit under section 7651c(d) or 7651h(b) has to start meeting its sulfur dioxide reduction requirement — that same unit also becomes an affected unit for nitrogen oxides, and must follow the nitrogen oxide limits set out below. (b) Emission limitations. Within eighteen months of November 15, 1990, the Administrator had to set, by regulation, annual nitrogen oxide limits for certain boiler types, not to exceed: 0.45 lb/mmBtu for tangentially fired boilers, and 0.50 lb/mmBtu for dry bottom wall-fired boilers that do not use cell burner technology. The Administrator can set a higher rate for a boiler type if low-NOx burner technology cannot actually achieve the listed rate. After January 1, 1995, any affected unit of these types must not exceed the rate the Administrator sets. By January 1, 1997, the Administrator also had to set annual-average nitrogen oxide limits, by regulation, for wet bottom wall-fired boilers, cyclones, units using cell burner technology, and all other boiler types not already covered. These rates must be based on the best continuous-reduction technology that can be retrofitted, considering available technology, cost, and energy and environmental effects — and the cost must be comparable to the cost of the controls required under the paragraph above. By that same date, the Administrator may also tighten the rates for tangentially fired and dry bottom wall-fired boilers if better low-NOx burner technology becomes available — but that tighter rate cannot be applied to a unit that is already an affected unit under section 7651c and already subject to the original 0.45 or 0.50 lb/mmBtu limits. (c) Revised performance standards. By January 1, 1993, the Administrator had to propose updated nitrogen oxide standards, under section 7411, for fossil-fuel-fired steam generating units — both electric utility units and other units. The Administrator had to finalize these updated standards by January 1, 1994. They must reflect improvements in ways to cut nitrogen oxide emissions. (d) Alternative emission limitations. If a unit cannot meet its assigned nitrogen oxide rate — because a unit under the first set of limits above cannot get there using low-NOx burner technology, or a unit under the second set of limits cannot get there using the technology the Administrator assumed — the permitting authority must, on request, allow it a looser limit instead. To qualify, the owner or operator must show, following regulations the Administrator had to issue within eighteen months of November 15, 1990: that it properly installed the right control equipment; that it ran that equipment for fifteen months (or another period the Administrator sets) and has data proving the equipment still cannot meet the assigned rate; and that it has identified a rate the unit actually can meet on an annual-average basis. The permitting authority then issues a permit that allows the higher rate during that fifteen-month test period, and afterward revises the permit to reflect the alternative rate the owner demonstrated. A unit under the first set of limits that gets an alternative rate does not have to install anything beyond low-NOx burners — though nothing stops an owner from installing better technology anyway. If an owner of a unit under the first set of limits shows the Administrator that the needed technology simply is not available in time to install and run it, while keeping the power grid reliable, by January 1, 1995, the Administrator must push that unit's deadline back by fifteen months. Any owner can ask the Administrator to make this finding, and the Administrator must grant or deny the request within three months. (e) Emissions averaging. Instead of meeting the nitrogen oxide limit unit by unit, an owner of two or more units subject to the limits described above can ask the permitting authority to approve one combined limit across those units. This is allowed only if the actual combined rate — pounds of nitrogen oxide per million Btu, averaged across the units — would be no higher than the combined rate would have been if each unit had met its own individual limit on its own. If the permitting authority, following regulations the Administrator had to issue within eighteen months of November 15, 1990, finds that this test can be met, it issues permits allowing the combined limit. That combined-limit arrangement only stays in effect while every unit in the group keeps operating under the terms of its own permit.