UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460 

# FEB222012
OFFICE OF AlA AND RADIATION Ms
. Aletta Belin Counselor to the Deputy Secretary U.S. Department ofInterior 1849 C Street, NW Room 6116 MS 7229-MIB Washington, D.C. 20240 Dear Ms. Belin: Thank you for completing Phase I ofyour study onNavajo Generating Station
. We expect that this report by the U.S. Department ofEnergy's National Renewable Energy Lab (NREL) titled ''Navajo Generating Station and Air Visibility Regulations: Alternatives and Impacts," will provide useful information to consider in the U.S. Environmental Protection Agency's BART analysis for this facility. During our initial review ofthe report after it was released, we discovered that some corrections and clarifications are needed, especially as they relate to the EPA actions. We have spoken to the NREL staffabout these issues and they indicated that they would make the necessary corrections in an errata sheet. However, to further the understanding ofthese complex issues, I am providing the attached list of factual corrections and clarifications to the report. We look forward to seeing the comments your office receives on this report, and to continuing to work together on this complex issue. Ifyou have any questions or concerns, please do not hesitate to contact me at (202) 564-3206, or Ms. Deborah Jordan, Director ofthe Region IX Air Division, at (415) 972-3133
. Sincerely,

Janet McCabe Principal Deputy Assistant Administrator Enclosure
cc: Deborah Jordan, Air Division Director, EPA Region IX

Internet Address (URL) _ http/lwww.epa
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_ Printed with Vegetableon Based Inks on 100"10 Postconsumer, Pr ocess Chlorine Free Recycled PaperEnclosure EPA Corrections to NREL Phase I Study on Navajo Generating Station 1. EPA regulatory actions on pages 12 and 14 are not accurately described. The Report states thatthe plant will be subject to a number ofregulations and implies that they will require additional investments. In many cases, we do not know whetherNGS would be affected (e.g
., in cases where standards have not been set, rules have not been finalized, or designations have not been completed). IfNGS were affected by many ofthese actions, it is likely that actions NGS has already taken or will take for MATS or BART would cover some oftheir obligations. Therefore
. , except in the case offinalized rules, EPA actions should be presented as "potentially affecting NGS," including in the title ofthe table on page 12
. a. Utility Mercury and Air Toxics Standard. The report incorrectly states that MATS sets emission limits for organic compounds. The final rule sets work practice standards for organic compounds. b. Cooling water intake. The rule will "minimize" not "prevent" impingement/entrainment ofaquatic life. c. Coal Combustion Residues. EPA has no public date for finalizing this rule. The status should read "pending". The summary should read "EPA has proposed to regulate coal ash to address the risks from the disposal ofthe wastes, such as residues from the combustion ofcoal in powerplants, generated by electric utilities and independent powerproducers
.The target date for release ofa final rule will be detennined pending a full evaluation ofall the infonnation and comments EPA received on the proposal." d. Ozone and PMNAAQS. The report states that EPA has proposed a revised ozone standard. In September 2011, EPA chose not to finalize that revised standard and instead has begun implementing the ozone NAAQS promulgated in 2008. EPA is also conducting the 5 year review ofthe ozoneNAAQS required by statute and expects a proposal in 2013. As a result, the schedule box for this action should read "pending"
. The text under "summary ofaction" for the PMNAAQS should also be used for the summary ofaction for the ozone NAAQS. Finally, since the ozone and PM NAAQS are the same type ofprocess now, both should be characterized as "reviews" or neither should be characterized as a "review." e. Transport Rule. Also on the table on pg. 12, the Transport Rule II is no longer on EPA's Regulatory Agenda. As a result, this rule should be removed from the table. f. Utility Boiler GHG NSPS. The Summary should read "EPA is under a court settlement to set NSPS standards for this source category for GHG emissions. Under the NSPS provisions, the agency will also establish guidelines for states to use in regulating existing sources such as Navajo GS. This process could lead to GHG requirements for Navajo OS.

, g. California Senate Bill 1368. The California OHO emission perfonnance standards does not impose any requirements on NOS, rather it affects one ofthe co-owners of NOS (Los Angeles Department ofWater and Power). We suggest the textbe adjusted to reflect this.
22 .
. The discussion on MATS onpage 51 is not current
- it describes the potential need for baghouses and sorbent injection to control SO) and sulfuric acid mist (both contribute to the condensable fractions ofparticulate matter). The final MATS rule set a filterable only PM limit of0.03 IbIMMBtu, therefore, discussion ofSO) and sulfuric acid controls is not relevant for MATS implementation and should not be characterized as such. EPA notes that source tests show that NGS generally already achieves 0
.03 Ib/MMBtu (filterable PM). Additionally, references to proposal and final rule dates associated with MATS are inconsistent in the report and do not correctly distinguish between signature dates and publication dates. The publication date ofthe final MATS rule in the Federal Register is February 16, 2012
. 3. In Table 3-11 on page 51, the costs labeled "SCR with sorbent injection and polishing baghouse" appearto be consistent with Sargent and Lundy cost estimates for SCR and DSI only (i.e., polishing baghouse not included)
. As noted above, theses costs are unlikely to be applicable to MATS implementation based on the final MATS rule
. 4
. Page 88
. Most sources will have 4 years to comply with MATS, until early 2016 (3 years available to all sources 

### + 4thyear that EPA expects to be widely available from permitting authorities to enable sources to complete compliance activities)
. 5. Table 5-1 on page 75 reports emissions ofNOx and S02 emissions that are identical. This appears to be a typographical error. 6. The narrative describing Table 5-6 on page 84 and the numerical values in the table are inconsistent. The narrative describes a reduction in nitrate concentrations overtime, but the values in the table shows a dramatic increase. Additionally, the percentreduction numbers do not seem to reflect the actual values in the table. 7. On page 93, the statementthat Mohave Generating Station in southeastern Nevada closed at the end of2005, due 

### largely to the cost ofretrofitting the power plant with S02 scrubbers is misleading. EPA understands that the spray dryers with high velocity baghouses were expected to cost $250 million, and that additional expenses at the time that were unrelated to the new scrubbers included a new slurry pipeline ( $250 million) and upgrades/life extension ofthe plant ($500 million) were three times higher than the cost ofnew controls
. Therefore, Mohave closed 

### inpart, due to the cost ofnew air pollution controls, but many other factors existed that affected decisions related to closure. 8. On page 101, the report is misleading in its description ofthe permitting ofDesert Rock. Although EPA requested a voluntary remand ofthe final permit to incorporate new applicable requirements, the project applicant has not responded to our multiple requests for an amended permit application; we most recently sent a letter in December 2011 and will follow up with another letter providing a deadline after which we will consider the application withdrawn. 9. Table 3-4 on page 45, should also list Springerville Units 3 and 4 as plants with installed SCRtechnology. Although Springerville is operated by Tucson Electric Power, Unit 4 is owned by SRP. These units came on line in 2007 and 2009. 10. The information on pages 45-47 should include any available cost information for the planned retrofit ofUnit 2 at Coronado Generating Station

- another SRP facility. The Consent Decree for Coronado requires the SCR be installed and operational by June 1, 2014.311. On pg. IV ofthe Executive Summary, the report states that LNB with SOFA have reduced NOx emissions at the plant by 40% relative to the plant's air pennitbefore controls were added. The percent control would be lower (-30% reduction from LNB/SOFA) ifthe calculation was done comparing pre-project actual emission rates to limits after installation ofLNB/SOFA. 12. On pg IV ofthe Executive Summary, the report then cites a 78% reduction ifSCR were installed and 50-60% reduction ifSNCR were installed
. A control efficiency of50-60% from SNCR is higher than typically cited for SNCR alone. SRP recently estimated SNCR could achieve 0.15

- 0.18 IblMMBtu atNOS (a 25

- 38% reduction on top ofpennitted levels of 0.24 IblMMBtu with LNB/SOFA). Because LNB/SOFA is already installed and operational at NOS, control efficiencies from SNCR and SCR alone should either be calculated using a baseline of0.24 IbIMMBtu, or if0.35 IblMMBtu is used as the baseline, should be reported as a control efficiency based on SNCR + LNB/SOFA or SCR+LNB/SOFA (i
.e., to be more consistent with values reported in Table 3-2 ofNRELreport).

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