(a) An owner or operator of any gaseous- or coal-fired utility boiler or stationary gas turbine may achieve compliance with the nitrogen oxides (NOX ) emission specifications of §117.1005 of this title (relating to Emission Specifications for Reasonably Available Control Technology (RACT)) by achieving compliance with a system-wide emission specification. Any owner or operator who elects to comply with system-wide emission specifications shall reduce emissions of NO X from affected units so that, if all such units were operated at their maximum rated capacity, the system-wide emission rate from all units in the system as defined in §117.10 of this title (relating to Definitions) would not exceed the system-wide emission specification as defined in §117.10 of this title.
  (1) The following units must comply with the individual emission specifications of §117.1005 of this title and must not be included in the system-wide emission specification:
    (A) gas turbines used for peaking service subject to the emission specifications of §117.1005(g) of this title; and
    (B) auxiliary steam boilers subject to the emission specifications of §117.1005(a), (c), (d), or (e) of this title.
  (2) Coal-fired utility boilers must have a separate system average under this section, limited to those units.
  (3) Oil-fired utility boilers must have a separate system average under this section, limited to those units. The NOX emission specification assigned to each oil-fired unit in the system must not exceed 0.5 pounds per million British thermal units (lb/MMBtu) based on a rolling 24-hour average.
(b) The owner or operator shall establish enforceable emission limits for each affected unit in the system calculated in accordance with the maximum rated capacity averaging in this section as follows:
  (1) for each gas-fired unit in the system, in lb/MMBtu:
    (A) on a rolling 24-hour averaging period; and
    (B) on a rolling 30-day averaging period;
  (2) for each coal-fired unit in the system, in lb/MMBtu on a rolling 24-hour averaging period;
  (3) for stationary gas turbines, in the units of the appropriate emission specification of §117.1005 of this title; and
  (4) for each fuel oil-fired unit in the system, in lb/MMBtu on a rolling 24-hour averaging period.
(c) An owner or operator of any gaseous and liquid fuel-fired utility boiler or gas turbine shall:
  (1) comply with the assigned maximum allowable emission rates for gas fuel while firing natural gas only;
  (2) comply with the assigned maximum allowable emission rate for liquid fuel while firing liquid fuel only; and
  (3) comply with a limit calculated as the actual heat input weighted sum of the assigned gas-firing, 24-hour average, allowable emission specification and the assigned liquid-firing allowable emission specification while operating on liquid and gaseous fuel concurrently.
(d) Solely for purposes of calculating the system-wide emission specification, the allowable mass emission rate for each affected unit must be calculated from the emission specifications of §117.1005 of this title, as follows.
  (1) The NOX emissions rate (in pounds per hour) for each affected utility boiler is determined by the following equation.
Attached Graphic
  (2) The NOX emissions rate (in pounds per hour) for each affected stationary gas turbine is determined by the following equations.
Attached Graphic

Source Note: The provisions of this §117.1015 adopted to be effective June 14, 2007, 32 TexReg 3206