U.S. EPA FACT SHEET
Proposed Rule: Coronado Generating Station - Reconsideration of Emission Limits and
Compliance Method
March 13, 2015
Summary of Action:
EPA is proposing to revise the Coronado Generating Station section of the Arizona Regional Haze
Federal Implementation Plan (FIP).
On December 5, 2012, the Arizona Regional Haze FIP established requirements for Best Available
Retrofit Technology (BART) for the Salt River Project Agricultural Improvement and Power District
(SRP) Coronado Generating Station, Units 1 and 2. A plant-wide limit for the averaged NOx emissions
from Units 1 and 2 was established as 0.065 lb/MMBtu.
On February 4, 2013, SRP, the owner/operator of Coronado, petitioned EPA for reconsideration.
EPA is proposing to replace a plant-wide compliance method with a unit-specific compliance method
for determining compliance with the best available retrofit technology (BART) emission limits for
nitrogen oxides (NOx) from Units 1 and 2 at Coronado. Specifically EPA is:
•	Proposing a unit-specific limit of 0.065 lb/MMBtu for Unit 1 and 0.080 lb/MMBtu for Unit 2
(both on a rolling 30-boiler-operating-day basis).
•	Proposing to remove the affirmative defense for malfunctions included in the RH FIP.
•	Proposing to revise the work practice standard in the FIP for Coronado.
Background:
The Clean Air Act (CAA) establishes as a national goal the prevention of any future and the remedying
of any existing man-made impairment of visibility in 156 national parks and wilderness areas
designated as Class I areas. It also directs states to require use of BART at certain larger, older
stationary sources in order to address visibility impacts from these sources.
The main feature of today's proposal is the change from a plant-wide compliance method and emission
limit to a unit-specific compliance method and separate emission limits for NOx on Units 1 and 2 at
the Coronado Generating Station. This change will allow for a slight increase in NOx emissions, but is
not expected to impact the projected visibility improvement at the 16 Class I areas within 300 km of
the plant. Visibility impacts are measured in deciviews. A source with an impact of 0.5 deciviews is
considered to contribute to visibility impairment, while a source with an impact of 1.0 deciviews or
more is considered to cause visibility impairment.
Next Steps:
The Federal Register notice will be published in approximately 2 to 3 weeks. There will be a 45-day
public comment period on this action.
More Information: http://www.epa.gov/region9/air/az/haze/index.html

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