New Mexico 

ENVIRONMENT DEPARTMENT 

Air Quality Bureau 

1301 Siler Road, Building B 

Santa Fe, NM 87507 

BILL RICHARDSON 

Governor 

Phone (505) 476-4300 RON CURRY 

Secretary 

DIANE DENISH 

Lieutenant Governor 

Fax (505) 476-4375 

www.nmenv.state.nm.us 

JON GOLDSTEIN 

Deputy Secretary 

October 27, 2009 

Ms. Anita Lee (Air-3) 

U.S. Environmental Protection Agency (EPA) 

Region IX RECE'VED 

75 Hawthorne Street 

San Francisco, CA 94105-3901 NOV 0 9 2009 

Permits urtice Air-3 

Re: EPA-R09-0AR-2009-o598 U.S. EPA. Region 9 

Dear Ms. Lee, 

The Air Quality Bureau of the New Mexico Environment Department (NMED) appreciates the 

opportunity to comment on the U.S. Environmental Protection Agency's (EPA) Advanced Notice 

of Proposed Rulemaking (ANPR) for the Assessment of Anticipated Visibility Improvements at 

Surrounding Class I Areas and Cost Effectiveness of Best Available Retrofit Technology 

(BART) for Four Comers Power Plant (FCPP) and Navajo Generating Station (NGS). 

According to the ANPR, based on 2006 emissions data from the EPA Clean Air Markets 

Division, FCPP is the largest source of NOx emissions in the United States (nearly 45,000 tons 

per year (tpy) of NOx). The FCPP is located near the Four Comers region of Arizona, New 

Mexico, Utah, and Colorado, and is within 300 kilometers (km) of sixteen mandatory Class I 

areas: Arches National Park (NP), Bandelier Wilderness Area (WA), Black Canyon of the 

Gunnison WA, Canyonlands NP, Capitol Reef NP, Grand Canyon NP, Great Sand Dunes WA, 

La Garita WA, Maroon Bells-Snowmass WA, Mesa Verde NP, Pecos WA, Petrified Forest NP, 

San Pedro Parks WA, West Elk WA, Weminuche WA, and Wheeler Peak WA. 

Also according to the ANPR and based on the same database, NGS is the fourth largest source of 

NOx emissions in the United States (nearly 35,000 tpy). NGS, in northern Arizona, is located 

within 300 km of eleven Class I areas: Arches NP, Bryce Canyon NP, Canyonlands NP, Capitol 

Reef NP, Grand Canyon NP, Mazatzal WA, Mesa Verde NP, Petrified Forest NP, Pine Mountain 

WA, Sycamore Canyon WA, and Zion NP. 

The determinations of BART at the FCPP and the NGS are very important decisions that will 

affect air quality at a large number of Class I areas. The NMED has received frequent complaints 
Ms. Anita Lee 

October 27, 2009 

Page 2 

about the brownish NOx plume from FCPP which is very visible in the Four Comers area. This 

plume is often visible from Mesa Verde National Park, located approximately 70 miles from the 

FCPP. 

As provided for in 40 CPR §51.308(e)(I)(ii)(B), the determination of BART for fossil-fuel fired 

power plants having a total generating capacity greater than 750 megawatts must be made 

pursuant to the Guidelines in Appendix Y of Part 51. Due to the size of the FCPP and the NGS, 

the EPA must follow the Guidelines in making BART determinations for the BART-eligible 

sources at both plants. 

The NMED is concerned that the EPA may have underestimated the emissions reduction possible 

from selective catalytic reduction (SCR) installation on Units 1-5 at FCPP. Appendix Y provides 

guidance on how to evaluate control techniques with a wide range of emission performance 

levels. Specifically, Appendix Y provides that: 

[I]in analyzing the technology you take into account the most stringent emission control 

level that the technology is capable of achieving. You should consider recent regulatory 

decisions and performance data (e.g., manufacturer's data, engineering estimates and the 

experience of other sources) when identifying an emissions performance level or levels to 

evaluate. (Emphasis added) 

The EPA cites the Arizona Department of Environmental Quality's recent determination that 

75% control from SCR (following upstream reductions by low NOx burners) was appropriate for 

the Coronado Generating Station in Arizona. The NOx emission rate at the Coronado Generating 

Station is 0.080 pounds per million British thermal units (lb/mmBtu) on a 30-Day Rolling 

Average. This rate was the result of a settlement agreement between the EPA and the 

Department of Justice and the Salt River Project Agricultural Improvement and Power District to 

resolve Clean Air Act violations at the Coronado Generating Station. As such, it represents a 

negotiated emissions reduction rather than the maximum emissions reduction achievable from 

SCR controls. It is therefore not necessarily the appropriate starting point for a BART 

determination. 

The ANPR does not provide sufficient detail on how the NOx emission rate for the Coronado 

Generating Station was achieved; therefore, the NMED cannot determine whether or not the rate 

is appropriate for the retrofit SCR installation at the FCPP. If the NOx emission rate submitted in 

the BART analysis for the FCPP was based on a vendor guarantee, the NMED believes that the 

BART Guidelines require that EPA use the vendor's guaranteed rate unless it is demonstrated 

that the rate is not achievable. 

The NMED also encourages additional review of the particulate matter controls at Units 4 and 5 

at the FCPP. It appears that because these units are already controlled by baghouses, no 

additional BART review was conducted on additional control technology on these units. This 

contradicts the BART Guidelines, which state that for units subject to a BART review that have 

control measures or devices already in place, it is important to include control options that 
Ms. Anita Lee 

October 27, 2009 

Page 3 

involve improvements to existing controls and not to limit the control options only to those 

measures that involve a complete replacement of control devices. Additional or more effective 

control technology on these units, as well as additional improved control technology on Units I 

through 3 at the FCPP and Units I through 3 at the NGS could achieve additional visibility 

improvements at mandatory Class I areas. Doing so would also achieve the co-benefit of 

additional mercury reductions. 

The NMED agrees with EPA that the estimated total annual cost of the NOx and particulate 

matter (PM) control technologies should be adjusted based on an annual-to-capital cost ratio of 

15%, to be consistent with annual costs estimated by other facilities. 

Regarding the modifications to emission rate inputs at the FCPP, the NMED considers it 

reasonable that EPA used the NOx emission data for the highest emitting days that occurred in 

2001. The NMED also believes it is reasonable to use sulfur dioxide (SOz) emission data 

(reduced with an 88% control efficiency) from a more recent period (2006 - 2007), rather than 

using the SOz data from the 2001 - 2003 meteorological periods. The modified SOz inputs 

appear reasonable to the NMED because the controlled SOz emission rates more accurately 

reflect the facility's current control technology. 

Regarding the inclusion of hydrochloric acid (HCI) and hydrogen fluoride (HF) in PM modeling, 

the EPA's method of including these pollutants is more reasonable than Arizona Public Service's 

(APS) assumption that sulfuric acid (HzS04) is the only contributor to condensable inorganic 

PM. However, it is likely that the inclusion doesn't make a substantial difference in visibility 

modeling results. This is because the impact of the pollutants is relatively small in comparison 

with other condensable inorganic PM, including nitrate and sulfate. Additionally, as EPA notes, 

the amount of HCI and HF is less than 0.01 % by mass and such a small amount has a negligible 

impact in degrading visibility in Class I Areas. 

The NMED supports a rigorous application of the BART Guidelines to select retrofit 

technologies that are truly the "best available," and to set emission limits that are clear, federally 

enforceable, and legally defensible. We appreciate your consideration of the above comments as 

part ofthe EPA Region 9's review of BART for the FCPP and NGS. 

Sincerely, 

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MaryUhl 

Bureau Chief 

Air Quality Bureau