# United States 

# Department ofthe 

# Interior

NATIONAL PARK SERVICE 1849 C Street, N.W. Washington. D.C. 20240
IN REPLY REFER TO: 

## NOV 2 0 

## 2009

N3615 (2350)
Ms. Anita Lee (Air-3) U.S. Environmental Protection Agency Region 9 75 Hawthorne Street San Francisco, California 94105-3901
Dear Ms. Lee:
The National Park Service (NPS) appreciates the opportunity to comment onthe Environmental Protection Agency's (EPA) Advanced Notice ofProposed Rulemaking (ANPR) regarding Assessment ofAnticipated Visibility Improvements at Surrounding Class I Areas and Cost Effectiveness ofBestAvailable Retrofit Technology (BART) for Four Comers Power Plant (FCPP) and Navajo Generating Station (NGS) (74 FR44313). These comments supplement the information we provided in ourJuly 24, 2009, letter to Deborah Jordan regarding visibility impacts and control options for nitrogen oxides emissions in determining BART for the NGS.
Emissions from the FCPP and NGS have significant impacts on numerous, spectacularly scenic Class I areas managed by the NPS, including, Grand Canyon, Canyonlands, Mesa Verde, Bryce Canyon and ZionNational Parks. Emissions also affect other park units with incomparable scenic values, like Glen CanyonNational Recreation Area, Chaco Canyon, and Canyon de Chelly. When we consider the costs ofadditional pollution controls for nitrogen oxides (NOx) in the context ofthe cumulative impacts, we conclude that applying selective catalytic reduction (SCR) to control these emissions is technically feasible, cost-effective, and will substantially improve visibility in many protected areas.
The comments we are providing today focus on 1) issues regarding background ammonia levels used in air quality models, 2) the techniques used to assess the degree ofvisibility improvement expected from application ofcontrol technology, and 3) detailed comments on the BART costs and technologies related to FCPP.
Comments onBackground Ammonia (NH32
The backgroundNH3 concentrations used inthe CALPUFF model need to represent NH3 available to form ammonium nitrate across the transport pathway from the source to the receptors ofinterest, notjustthe NH3concentration at the specific receptor. NPS CALPUFF analyses for NGS and FCPP followed guidance from the Western Regional Air Partnership (WRAP) BART modeling protocol' to use a default value of 1part per billion (ppb) NH3 as a reasonable representation ofNH3

.

1 Western Regional Air Partnership BART Modeling Protocol. 2006. hrtp://pah.cert.ucr.eduJaqrn/308/bart.shtrnl2
Monitoring datato refine the background NH3values are limited. Sather et al. (2008)2 measured NH3at several locations in the Four Comers area and reported that measured NH3values vary spatially withhigher values near oil and gas, mobile, and industrial sources. Values at Mesa Verde National Park were the lowest measured, likely because NH3had already reacted to form ammonium sulfate and ammonium nitrate. NH3values were lower in winterthan summer. We agree with EPA's approach to calculate monthly NH3values for MesaVerde National Park, based onthe range ofmonitored NH3values inthe Four Comers area from the Satherreport (monthly values ranged from 1.0 ppb in winterto 1.5 ppb in summer).
NH3measurements are not available at other Class I areas inthe FCPP and NGS domain. We agree withEPA that available Interagency Monitoring ofProtected Visual Environments (IMPROVE) monitoring data canbe used to estimate a minimum value for the NH3necessary to account for sulfate and nitrate at the monitors. The EPA used NH3 calculations from 14 IMPROVE monitors to derive a reasonable monthly estimate ofNH3available in the modeling domain (ranging from 0.7 ppb inwinter to 1.3 in summer).
The NH3values used in CALPUFF modeling for Arizona Public Service and Salt River Project for the winter months (0.2-0.5 ppb) are too low. Itis necessary to represent not only the ammonia atthe receptor, but also ammonia available along the transport pathway from the
source.
Rather than continue disagreement over the absolute values to represent NH3in the modeling domain, it is important to view the CALPUFF modeling results in a relative sense to consider cumulative visibility impacts across multiple Class I areas and across alternative control options.
Comments on Techniques to Assess Visibility Improvement
We support the EPA's consideration ofthe visibility improvementthat is expected to occur at multiple Class I areas. We believe that all BART assessments should considerthe cumulative amount ofvisibility improvement that control technologies would achieve at all Class I areas affected by emissions from the BART source. While it is appropriate to assess a single Class I area to determine ifa BART-eligible source is subject to BART requirements, the assessment of BART factors, which includes the cost ofemission controls, must weigh the full degree of improvement expected for incurring costs.
To date, most BART assessments we have reviewed provide information onthe change inthe 98th percentile impacts at one or more Class I areas. Itis oftenpossible to use the air quality modeling information developed by states or the sources during the subject-to-BART assessment to compile a measure ofvisibility improvement for Class I areas in the model domain. While this only reflects the change ofthe 98th percentile atthe most affected receptor in the Class I area, it is a useful measure for understanding not only the magnitude ofvisibility improvement, butthe geographic scope ofthe benefit from applying a given set ofemissions controls. The enclosed maps illustrate the visibility improvement at 16 Class I areas affected by the FCPP and at 11 Class I areas affected by NGS inresponse to installation ofSelective Catalytic Reduction (SCR) controls with combustion controls for the 98th percentile impact averaged over 2001-2003 CALPUFF modeling results. The cumulative benefit calculatedbythe NPS for FCPP is 27.25

2 Sather, M.E. et ai., 2008, J ofEnvironmental Monitoring 10, 1319-1325.3

deciviews (dv) and for NGS is 23.2 dv. The EPA appliedthis samemethodology in Tables 26 and 35 ofthe ANPR. We support this level ofassessment and support using the cumulative visibility impact across all affected Class I areas when assessing a cost-effectiveness measure, such as dollars perdv.
Tables 27 and 36 provide an Alternative Visibility Metric, which takes the 98th percentile change at the most affected receptor and multiplies this value times the land area ofthe Class I area. Wehave concerns regarding this metric. Our first concern is that the 98th percentile change for the most affected receptor is notrepresentative of**chan~es** across the entire Class I land area. To address this concernwouldrequire assessingthe 98t percentile impacts for all receptors in the Class I area and determining the land area associated with eachreceptor. This reveals our second concern that informationrequired to better assess visibility improvement across the entire Class I area goes way beyond that developed bythe states or sources when conducting BART analyses. We also question whether such level ofassessment would improve onthe simple summation ofpeak impacts technique as a means to considermultiple Class I areabenefits when making a BART determination. Furthermore, the Alternative Visibility Metric would value larger Class I areas more so than smaller Class I areas, whereasthe Regional Haze Rule treats all mandatory Class I areas equally. In summation, we believe the technique used to sum impacts shown inTables 26 and 35 should be used to develop a costperdv improvementmeasure to be compared with BART decisions made in developing the EPApresumptive BART emissions rates, as well as with BART decisions completed by other States and otherEPA Regions. Summary ofComments onthe Technical Information for the FCPP BART Determination

We have enclosed detailed comments regarding APS'sproposedNOxBART analyses. These comments are summarized below. According to the EPA's Clean AirMarkets (CAM) database, the FCPP was the second largest stationary source ofNOx inthe U.S. in 2008, at40,311 tons. Because Arizona ArizonaPublic Service (APS) overestimatedthe costs ofSelective Catalytic Reduction (SCR) and underestimated its benefits, we relied primarily upon our own analyses ofthe BART cost and benefit factors. Our analyses indicate that FCPP causes visibility impairment in all 16 Class I
areas within 300km, and that FCPP causes the greatest cumulative impactupon Class I area visibility ofany single source we have evaluated to date. Whenwe considerthe costs ofBART in the context ofthe cumulative impacts from FCPP, we conclude that applying SCRto control these emissions is technically feasible, cost-effective, and will substantially improve visibility in these protected areas. Please notethat we reached a similar conclusion in our July 24,2009, commentsregardingNOxcontrols atNGS, i.e., SCR at NGS is technically feasible, costeffective, and will substantially improve visibility inmultiple Class I areas.
One ofthe options suggestedby the BART Guidelines to evaluate cost-effectiveness is costper dv. Comparedto the typical control cost analysis in which estimates fall into the range of$2,000

- $10,000perton ofpollutantremoved, spendingmillions ofdollars perdv to improve visibility may appear extraordinarily expensive. However, ourcompilation3 ofBART analyses across the U.S. reveals that the averagecost per dv proposed by either a state ora BART source is $10

3 http://www

.wrapair.org/forums/ss jflbart.html4

- $17 million,4 with a maximum ofalmost $50 million per dv proposed by Colorado at the Martin Drake powerplant in Colorado Springs.
We applied this cumulative approach to the FCPP analysis and found that the cumulative impact from the baseline condition on visibility is 46.6 dv across the 16 Class I areas modeled. We compared the visibility improvement resulting from combustion controls and SCRto the range ofcosts we generated for eachunit and found that SCR 

### @0.07 lb/mmBtu (24-hour average) would improve visibility by 27 dv at a Total Annual Cost of$42.3 million 

### (@ 0.05 Ib/mmBtu, annual average). This yields a cost-effectiveness estimate of$1.9

- $2.7 million/dv (depending upon the unit), which is more cost-effective than the $10

- $17 million per deciviewthat, on average, states and sources have determined was cost-effective for their chosen BART strategies.
S02BART
In the late 1990's, APS initiated a dialog with four environmental interest groups involved in environmental issues in the western United States: Environmental Defense, the Grand Canyon Trust, Western Resource Advocates and the New Mexico Citizens for Clean Air and Water. The dialog focused on the issue ofvisibility inthe western United States, and on improved S02 control primarily because that pollutant had much higher visibility impactthanNOx emissions. In 2003, APS and the environmental groups agreed on a proposal geared to further reduce S02 emissions at the FCPP utilizing an l8-monthtest program. The test program involved certain phased operational changes and scrubber chemical process changes to increase annual S02 control levels from 72% to 85% withouttriggering operational problems. APS and the environmental groupsjointlypresented thatproposal to the EPA, the Navajo EPA and the NPS. Withthe support ofthese groups, APS initiated the test program in early 2004. The test program was completed during the summer of2005. APS prepared a report concluding that the plant was not only able to meet the goal set in the proposal, but could also improve the annual average S02 controls to an 88% removal efficiency. Atthat elevated control level, the plantwas able to cut its annual S02 emissions by more than 55%, comparedto the pre-test level.
Afterthe testing program, the Navajo Nation and the stakeholders group requested that EPA include these negotiated, additional S02 emissions reductions into a source-specific Federal Implementation Plan (FIP) for the FCPP. APS agreed to increase the amount ofS02 emissions it was eliminating from its exhaust stream from 72% to 88%, thereby reducing its annual emissions ofS02 to the atmosphere by about 25,000 tons per year. APS and the environmental groups then worked with the reviewing agencies to incorporate the higher sulfur dioxide controlleve1 as an enforceable emission limit for the plant through the FIP. The FIP, published inthe May 7,2007, Federal Register, provides EPA's policy on whetherthe agreed-upon S02 controls are BART equivalent, with excerpts provided here:
"APS, in partnership withthe Navajo Nation, several environmental groups and Federal agencies, conducted a test program to determine ifthe efficiency ofthe existing scrubbers at FCPP could be improved from the recenthistorical level of72% S02removal to 85%. The test program, which was completed in spring of2005, was successful and the plant

4 For example, PacifiCorp has stated in its BART analysis for its Bridger Unit #2 that "The incremental cost effectiveness for Scenario I compared with the baseline for the Bridger W A, for example, is reasonable at $580,000 per day and $18.5 million per deciview."

### 5

was able to achieve a plant-wide annual S02 removal of88%. The parties involved inthe test program have agreed that this rule should propose to require 88% efficiency for the FCPP.
The EPA believes thatthe S02 controls proposedtoday for FCPP are close to or the equivalent ofa regional haze BART determination for 802. For example, the BART Guidelines published by EPA in 2005 establish a presumption for the control ofS02 from uncontrolled large utility boilers ofeither 95% control or 0.15 IbslMMBtu, but suggest that for electric generating units with pre-existing post-combustion S02 controls ofat least 50% removal efficiency, states consider cost effective scrubber upgrades designed to improve the system's overall S02 removal efficiency, 70 FR 39104,39171 (July 6, 2005). The conclusion that the S02 controls proposed today are close to or the equivalent ofBARTtakes into consideration not only the BART Guidelines but also the early reductions for Regional Haze thatthis action will achieve through the modifications to the existing S02 scrubbers. As explained intoday's companion notice for NGS published elsewhere inthis Federal Register, EPApreviously determined thatthe S02 emission limits in the 1991 FIP for NGS provide for a greater degree ofreasonable progress toward the Regional Haze national goal than would BART. See 56 FR 50172. As a result, EPA does notconsider it necessary or appropriate to develop a regional haze planto address the BARTrequirements under 40 CFR 51.308 for the Navajo Reservation for S02." (emphasis added)
While we agree with the overall premise that 88% emission control is likely to represent BART on a plant-wide basis, we believe that EPA must follow its own BART Guidelines and its fivestep BARTprocess, and make formal BART determinations for each unit at FCPP to showhow the 88%-control target, with appropriate emission limits, represents a solutionthat is more than "close to" BART. As we commented in a letterto EPA onNovember 6, 2006, onthe previous Federal Implementation Plan (FIP) actions, we do not believe that the previous FIP actions satisfy the BART requirements.
Overthe past several months, we have worked with your staffto evaluate FCPP and NGS under EPA's BART Guidelines, and we are very appreciative oftheir expertise and assistance. We look forward to continuing this cooperative working relationship as this process advances. We believe that good communication and sharing ofinformation will help expedite this process, and suggest that you contact Don Shepherd (don shepherd(i{inps.gov, or 303-969-2075) ifyouhave any questions regarding these or ourJuly 24, 2009, comments. Sincerely,

Michael D. Snyder Regional Director
Enclosures7



### Colleen McKaughan US EPA Region 9 75 Hawthorne Street San Francisco, CA 94105
Ken Cronin Tribal Caucus Coordinator/ Regional Planning Organization Specialist (WRAP) National Tribal Environmental Council 4520 Montgomery Blvd. Suite 3 Albuquerque, NM 87109

IMR: John Reber GRCA: Martha Hahn MEVE: George San Miguel ARD: Julie Thomas-McNamee FWS: Tim Allen ARD-DEN: Permit Review Group, Reading and ProjectFile, Chris Shaver ARD-DEN: bpolkowsky:bp:x6944: 10/26/2009: