## USDA United States 

### :z:-=== Department of Agriculture Forest Service Intermountain Region 324 25th Street Ogden, UT 84401 801-625-5605

File Code: 2580 Date: October 31, 2008 Mr. David A. Finley, Administrator Division ofAir Quality Department ofEnvironmental Quality 122 W. 25th Street Cheyenne, WY 82002

DearMr. Finley: The Forest Service (FS) has reviewed the Department ofEnvironmental Quality's (DEQ) Best Available Retro-Fit Technology (BART) determinations for the BART-eligible emission units at the FMC GrangerAP-6044, FMC Westvaco AP-6045, and General Chemical Green River Works AP-6046 facilities. The BART determination is a critical component ofthe EPA Regional Haze program to improve visibility in ournational parks and wilderness areas, of which Regional FurtherProgress and the Long Term Strategy are also key components. As such, the decisions made by the DEQ underthe BART process may also affect the otherprogram elements affecting ournation's ability to improve visibility. With this broaderperspective, the FS offers the following comments on the DEQ's BART determinations. 

### Dispersion Modeling

- Ozone Concentrations: The FS is concerned that visibility impacts may be underestimated in the refined modeling, as causedby an under-representation ofthe ozone concentration. The ozone data used in the BART modeling is not believed to be spatially or temporally representative ofthe ozone concentration ofaplume/pufftraveling from any ofthe BART-eligible emission sources near Green River toward the Fitzpatrick and BridgerWilderness areas. Emissions ofairpollutants originating near Green River mustpass through the atmosphere nearthe Jonah and Wamsutteroil and gas fields as they travel toward the Bridger and Fitzpatrick Wilderness areas. The ozone dataused in the modeling is from 2001 through 2003. In 2001, there were reported 25,199 oil and gas producing wells in Wyoming. By 2006, this number increased to approximately 38,000 wells state wide l
, with associated increases in air emissions. In 2006, the first-ever wintertime exceedance ofthe ozone standard was experienced in Sublette County. Hence, hourly ozone data used in the refined dispersion modeling for the BART analyses is not temporally representative. Similarly, the spatial distribution ofthe ozone monitoring sites used in the BART modeling analysis is suspect. Recent studies ofmonitoring locations in southwestern Wyoming have certainlyraised awareness ofthe complexity ofaddressing this issue. Unfortunately, the Pinedale ozone monitoring site was not operating during this studyperiod, so a direct comparison is not possible. However, the areanear South Pass appears to have higherozone

I Wyoming Oil & Gas Commission.
Caring for the Land and Serving People Printed on Recyded Paper 

# 0DearMr. Finley 2

concentrations than near Pinedale. As such, the FS is concerned that the ozone dataused in the BART modeling is not spatiallyrepresentative. The underestimation ofozone concentration affects the model-predicted haze impacts primarily for nitrates, as follows. Ozone is the primary source ofhydroxyl radicals (OR), which playakey role in the formation ofammonium sulfate [(NH4)2S04] and ammonium nitrate (NR4 N03) in the CALPUFF model. Ozone serves as the primary source ofhydroxyl radicals, which react with N02to form nitric acid. The nitric acid reacts with ammonia to form ammonium nitrate. Figure 1 below illustrates the effect ofozone concentration on the formation ofnitric acid (RN03), which is also affected by PG stability class and N02concentration. Underestimating the ozone concentration by 20 ppb (e.g., 40 ppb instead of60 ppb), may result in a 50 percent underestimation in the conversion rate ofN02 to nitric acid, and effectivelyreduce the modelpredicted haze by halffor a givenhour. Figure 1. Effect ofOzone Concentration on Nitric Acid 

### Conversion Rate of NOx to HN03 [NOx] 

# =0.025 ppm

(1) 

### 30.0 25.0 

### c: "C 

### 20.0 0 .c: 

### 15.0 

## 'i!!

# - (1) 

# - 10.0 > 

### c: 5.0 0 0 

### 0.0 0.01 0.03 0.05 0.07 0.09 

# F**-ffiT~-2** 1---ffiT=3 

# L ffiT=4

----.--

Ozone Concentration (ppm)

To remedy this issue, the FS is requesting that Wyoming DEQ re-evaluate the more recent hourly ozone data to ensure an appropriately representative value is used, and rerun the BART dispersion modeling analysis. Natural Background Concentration: The DEQ states that "Species concentrations corresponding to the 20 percentbest days were calculated for each Class I area by scaling backthe annual average concentrations given in Table 2-1 ofthe EPA document Guidancefor EstimatingNatural Visibility Conditions Under the RegionalHaze Rule." Additional information is needed to understand and evaluate the use of scaling factors as applied to the annual average concentrations for calculating backgroundDearMr. Finley 

### 3

concentrations for the 20 percentbest days. As this infonnation is used in the quantification of change in light extinction, which is subsequently compared with thresholds ofacceptance, a thorough understanding ofthis approach is needed for concurrence. 

### USDA Forest Service Comments on BART Determination for FMC Granger The FS understands that two BART-eligible units were evaluated and deemed exempt from BART based upon refined dispersion modeling. These two units are 358.5 MMBtulhrcoal-fired boilers, each equipped with FGD scrubber and ESP controls. Given the modeling concerns expressed above, the FS cannot concurwith the DEQ's detennination that these BART-eligible units are not subject to BART at this time. 

### USDA Forest Service Comments on BART Determination for FMC Westvaco Facility AP-6045 The FS has reviewed the DEQ's proposed BART detennination for the three BART-eligible emission units at FMC's Westvaco facility. We understand that one ofthese units, the naturalgas fired boiler (PH-3), has been detennined not to be subject to BART based upon the results of refined dispersion modeling. The remaining two units NS-1A and NS-1B, both coal-fired boilers, are subject to BART. In making its detennination, the DEQ recognized and relied upon the fact that applying the recently installed low NOx burners and OFA for NOx is sufficientto bring the model-predicted 98th percentile impactbelow the 0.5**~dv** threshold. As such, the DEQ recommends that no additional controls are warranted. The FS acknowledges this approach, as many BART-eligible sources are using federallyenforceable controls to reduce model-predicted impacts below the subjectto BART thresholds. However, recognizing thatBART is one ofthree components ofthe Regional Haze Rule that the State will use to achieve ournational visibility goals, we encourage the DEQ to consider the cumulative impacts ofseveral BART-eligible sources in the Green River area. Considerthe following discussion contained in the preamble to the Regional Haze Rule pp 39120-39121. "In a regulatory context, we believe thata State's decision as to an appropriate threshold for contribution coulddepend upon the numberof sources affecting a class Iarea. To illustrate, 

## if there were only one emissions source affecting visibility in a class Iarea, thatsource couldhave a deciview impactonlyslightly below theperceptibility thresholdwith outcontributing to noticeable impairment. However, 

## if there were 1000sources each changing visibility by 0.1 deciviews, the total impact wouldbe a 10deciview change in visibility. In this hypothetical example, all 100sources wouldbe contributing in equalamounts to substantialvisibility impairment. " Currently, there are two BART-eligible sources at the FMC Granger facility, three BARTeligible sources at the FMC Westvaco facility, and two BART-eligible sources located atDearMr. Finley

General Chemical Green River Works facility. Four ofthese seven sources have been determined to be subjectto BART, afterrefined modeling. 4

The current approachproposed by the DEQ is to reduce emissions from each subjectto BART source to controls, which reduce individual impacts from each source tojustbelow the 0.5**~dv** threshold. Our general comments regarding the dispersion modeling apply to this facility. As such, the model-predicted impacts may be underestimated, which ifthis is the case, would warrant further emissionreductions. As already identified by the US Department ofInterior, the costs for implementing controls beyond the minimum proposedby the DEQ are reasonable. Upon consideration ofthe cumulative impacts from these sources, additional controls implemented at this time will help the DEQ move closertoward its reasonable progress goals. Hence, whetherthese controls are implemented as part ofBART or underReasonable FurtherProgress, such controls are viewed as reasonable. S02 Controls: The S02 controls identified for the two coal-fired boilers in DEQ's analysis are limited for two options for increasing the amount ofgas routed exhaust through the wet scrubber. However, the EPA BART rule identifies several otherwet scrubberupgrade options, which are not currently addressed in the DEQ's analysis. These additional upgrade options include installation ofliquid distribution rings; installation ofperforatedtrays; use oforganic acid additives; improve or upgrade scrubber auxiliary system equipment; and redesign spray header ornozzle configuration. Each ofthese upgrade options should be considered in the BART analyses. Analysis ofControl Technologies in the Visibility Modeling: In evaluating the effectiveness ofthe various control options in reducing haze, it would be helpful ifthe modeling results were presented for the combination ofLNB/OFNSNCR (NOx) and scrubberupgrades, both without and with a new bypass (S02). BART Determination: The DEQ determined that the installation oflow NOx burners with enhanced OFA meeting NOx emission limits of0.35 Ib/MMBtu (30-day rolling average), represents BART for each ofthe coal-fired boilers. The DEQ states that this determination is based on the results ofthe visibility analysis, which show that FMC's proposed BART control option results in an average reduction of0.3**~dv** in the 98th percentresult at BridgerWilderness Area as compared to the baseline condition for each unit, and areduction of0.2**~dv** in the 98th percentresult at Fitzpatrick Wilderness Areacompared to baseline conditions. The 98th percentile values for both units NS-IA and NS-IB were below 0.3**~dv** increase from background conditions for all 3 years of meteorology.DearMr. Finley 5

This determination is based upon considerations ofthe model-predicted change in deciviews compared to baseline conditions. EPA states in the preambleto its BART Guideline2that "Even though visibility improvement from an individual source may notbe perceptible, it should still be considered in setting BART because the contribution to haze may be significantrelative to other source contributions in the Class I areas." Given the proximity ofthe two boilers, the combined effect ofrequiring more stringent controls, such as LNB/OFA with SNCR, will likely allow the State to reach its reasonable progress goals 

### USDA Forest Service Comments on BART Determination for General Chemical Green River Works AP-6046 The FS has reviewed the DEQ's proposed BART determination for the two BART-eligible emission units at General Chemical Green River Works. We understand the two units are tangentially fired boilers using in-line pulverizers to burn low sulfur subbituminous coal, which supply power and process steam to the mining and ore processing operations. BoilerC has a firing rate of534 MMBtulhr and Boiler D has a firing rate of880 MMBtulhr. Each boileris currently equipped with a hot-side ESP to control particulates, overfire air and low excess air used to reduce NOx, and no add-on controls for S02. Our comments are presentedbelow. 

### Dispersion Modeling: Please referto ourprevious comments on ozone concentrations and use ofscaling factors for determination ofbackground concentrations. 

### Effectiveness ofControl Technologies: NOx In its preamble to its BART Guidelines, EPA states, "Many control techniques
...can perform at a wide range oflevels
.. .It is important, however, that in analyzing the technology, you take into account the most stringent emission control level that the technology is capable ofachieving." The DEQ identifies the effectiveness ofNOx controls as follows: low NOx burners (LNB) with separated overfire air (SOFA) achieve 30 percent control; SNCR achieves 50 percent control, and SCR achieves 80 percent control. LowerNOx emissionrates are achievable. Low NOx burners with advanced over-fire air, tangentially-fired boilers are able to achieve NOx emission rates between 0.14 and 0.39 Ibs/MMBtu (equivalentto 20-77 percent control)3. Similar emission rates were found in the NETL coal plant database. For example, the Ameren Rush Island Facility in Missouri is able to achieve annual average NOx emission rates of 0.089 Ibs/MMBtu, and 0.0941bs/MMBtu for its two boilers. Ameren's Newton, Illinois, facility is able to achieve an annual average NOx emission rate of0.136 Ibs/MMBtu. SNCR alone can achieve between 30-50 percent reductions in NOx4• SCR can achieve up to 90percentreductionS.

2Federal RegisterNol. 70 No. 128/Wednesday, July 6,2005. Page 39129 3 Aistom TFS 2000R Low NOx Control Systerm 4 U.S. EPA Air Pollution Control Technology Fact Sheet: Selective Non-Catalytic Reduction. EPA-452/F-03-031. 5 U.S. EPA Air Pollution Control Technology Fact Sheet: Selective Catalytic Reduction: EPA-452/F-03-032.DearMr. Finley 

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The use oflowerthan best achievable control effectiveness results in lowermodel-predicted reductions in haze, and therefore potentially affects the determination ofBART. 

### Costs: The costs for applying each ofthese control technologies is higherthan typical costranges. For example, ultra low NOx burners with advanced over-fire air, tangentially-fired boilers cost between $300 and $1200 per ton, whereas the costs are estimated at $1332 perton for BoilerC and $1433 for BoilerD. Typical SNCR costs are $500

- $1500 per ton6
, whereas the proposed costs are estimated at $2712 perton for Boiler C and $2025 per ton for BoilerD. 

### Western Backstop Sulfur Dioxide Trading Program: The DEQ has stated that "General Chemical will not be required to meet eitherproposed emission limit under BART. Instead, General Chemical will be required to participate in the emissions trading program under Chapter 14 ofthe WAQSR should the programbe triggered." Under40 CFR 51.309 (g)(2)(ii), the requirement under 51.308(e) related to BART for regional haze is deemed to be satisfied for pollutants addressed by the milestones and backstop trading program if, in establishing the emission reductions milestones underparagraph 40 CFR 51.309 (d)(4), it is shown that greaterreasonable progress will be achieved for these additional Class I areas (e.g., Fitzpatrick and BridgerWilderness Areas) than would be achieved through the application ofsource-specific BART emission limitations under 51.308 (e)(l). Additional information supporting this demonstration is required, otherwise the S02 emission limits established under BART will be in effect. We appreciate your consideration ofthese comments. Should you have questions regarding these comments please contact Bud Rolofson, FAA Staff, at (303) 275-5752. Sincerely,

/s/ Brent Larson (for) HARV FORSGREN Regional Forester

cc: Mike Dudley Bud Rolofson JeffA Sorkin Rick Graw ScottA Copeland Ann Acheson

6 Midwest RPO Interim White Paper
- EGUs. March 2006