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 of Air Quality

Department ofEnvironmental Quality

122 W. 25th Street

Cheyenne, WY 82002

Dear Mr. 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 Granger AP-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 our national parks and wilderness areas, of

which Regional Further Progress and the Long Term Strategy are also key components. As

such, the decisions made by the DEQ under the BART process may also affect the other program

elements affecting our nation's ability to improve visibility. With this broader perspective, 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

caused by 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

ofa plume/pufftraveling from any ofthe BART-eligible emission sources near Green River

toward the Fitzpatrick and Bridger Wilderness areas. Emissions of air pollutants originating near

Green River must pass through the atmosphere near the Jonah and Wamsutter oil and gas fields

as they travel toward the Bridger and Fitzpatrick Wilderness areas. The ozone data used 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 winter time 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

certainly raised awareness ofthe complexity of addressing this issue. Unfortunately, the

Pinedale ozone monitoring site was not operating during this study period, so a direct

comparison is not possible. However, the area near South Pass appears to have higher ozone

I Wyoming Oil & Gas Commission.

Caring for the Land and Serving People Printed on Recyded Paper 0
Dear Mr. Finley 2

concentrations than near Pinedale. As such, the FS is concerned that the ozone data used in the

BART modeling is not spatially representative.

The underestimation of ozone concentration affects the model-predicted haze impacts primarily

for nitrates, as follows. Ozone is the primary source ofhydroxyl radicals (OR), which playa key

role in the formation of ammonium sulfate [(NH4)2S04] and ammonium nitrate (NR4N03) in the

CALPUFF model. Ozone serves as the primary source of hydroxyl radicals, which react with

N02to form nitric acid. The nitric acid reacts with ammonia to form ammonium nitrate.

Figure 1 below illustrates the effect of ozone concentration on the formation of nitric acid

(RN03), which is also affected by PG stability class and N02concentration. Underestimating

the ozone concentration by 20 ppb (e.g., 40 ppb instead of 60 ppb), may result in a 50 percent

underestimation in the conversion rate ofN02 to nitric acid, and effectively reduce the modelpredicted haze by half for a given hour.

Figure 1. Effect of Ozone 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:

0 5.0

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 percent best days were

calculated for each Class I area by scaling back the annual average concentrations given in Table

2-1 ofthe EPA document Guidance for Estimating Natural Visibility Conditions Under the

Regional Haze Rule." Additional information is needed to understand and evaluate the use of

scaling factors as applied to the annual average concentrations for calculating background
Dear Mr. Finley 3

concentrations for the 20 percent best days. As this infonnation is used in the quantification of

change in light extinction, which is subsequently compared with thresholds of acceptance, 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 MMBtulhr coal-fired

boilers, each equipped with FGD scrubber and ESP controls.

Given the modeling concerns expressed above, the FS cannot concur with 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 sufficient to bring the model-predicted

98th percentile impact below 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 subject to BART thresholds.

However, recognizing that BART is one ofthree components ofthe Regional Haze Rule that the

State will use to achieve our national visibility goals, we encourage the DEQ to consider the

cumulative impacts ofseveral BART-eligible sources in the Green River area. Consider the

following discussion contained in the preamble to the Regional Haze Rule pp 39120-39121.

"In a regulatory context, we believe that a State's decision as to an appropriate thresholdfor

contribution could depend upon the number ofsources affecting a class I area. To illustrate, if

there were only one emissions source affecting visibility in a class I area, that source could have

a deciview impact only slightly below the perceptibility threshold with out contributing to

noticeable impairment. However, ifthere were 1000 sources each changing visibility by 0.1

deciviews, the total impact would be a 10 deciview change in visibility. In this hypothetical

example, all 100 sources would be contributing in equal amounts to substantial visibility

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 at
Dear Mr. Finley

General Chemical Green River Works facility. Four ofthese seven sources have been

determined to be subject to BART, after refined modeling.

4

The current approach proposed by the DEQ is to reduce emissions from each subject to BART

source to controls, which reduce individual impacts from each source to just below 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

emission reductions.

As already identified by the US Department ofInterior, the costs for implementing controls

beyond the minimum proposed by the DEQ are reasonable. Upon consideration ofthe

cumulative impacts from these sources, additional controls implemented at this time will help the

DEQ move closer toward its reasonable progress goals. Hence, whether these controls are

implemented as part ofBART or under Reasonable Further Progress, 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 of gas routed exhaust through the wet scrubber. However, the

EPA BART rule identifies several other wet scrubber upgrade options, which are not currently

addressed in the DEQ's analysis. These additional upgrade options include installation of liquid

distribution rings; installation of perforated trays; use of organic acid additives; improve or

upgrade scrubber auxiliary system equipment; and redesign spray header or nozzle configuration.

Each ofthese upgrade options should be considered in the BART analyses.

Analysis of Control 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 scrubber upgrades, both without and with a new bypass (S02).

BART Determination:

The DEQ determined that the installation of low NOx burners with enhanced OFA meeting NOx

emission limits of 0.35 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

of 0.3 ~dv in the 98th percent result at Bridger Wilderness Area as compared to the baseline

condition for each unit, and a reduction of 0.2 ~dv in the 98th percent result at Fitzpatrick

Wilderness Area compared 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.
Dear Mr. Finley 5

This determination is based upon considerations ofthe model-predicted change in deciviews

compared to baseline conditions. EPA states in the preamble to its BART Guideline2that "Even

though visibility improvement from an individual source may not be perceptible, it should still

be considered in setting BART because the contribution to haze may be significant relative 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. Boiler C has a

firing rate of 534 MMBtulhr and Boiler D has a firing rate of 880 MMBtulhr. Each boiler is

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 presented below.

Dispersion Modeling:

Please refer to our previous comments on ozone concentrations and use ofscaling factors for

determination ofbackground concentrations.

Effectiveness of Control Technologies: NOx

In its preamble to its BART Guidelines, EPA states, "Many control techniques...can perform at a

wide range of levels.. .It is important, however, that in analyzing the technology, you take into

account the most stringent emission control level that the technology is capable of achieving."

The DEQ identifies the effectiveness of NOx 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. Lower NOx emission rates 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 (equivalent to 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 of 0.136 Ibs/MMBtu. SNCR alone can achieve

between 30-50 percent reductions in NOx4

• SCR can achieve up to 90 percent reductionS.

2 Federal 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.
Dear Mr. Finley 6

The use oflower than best achievable control effectiveness results in lower model-predicted

reductions in haze, and therefore potentially affects the determination ofBART.

Costs:

The costs for applying each ofthese control technologies is higher than typical cost ranges. 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 per ton for Boiler C

and $1433 for Boiler D.

Typical SNCR costs are $500 - $1500 per ton6

, whereas the proposed costs are estimated at

$2712 per ton for Boiler C and $2025 per ton for Boiler D.

Western Backstop Sulfur Dioxide Trading Program:

The DEQ has stated that "General Chemical will not be required to meet either proposed

emission limit under BART. Instead, General Chemical will be required to participate in the

emissions trading program under Chapter 14 ofthe WAQSR should the program be triggered."

Under 40 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 under paragraph 40 CFR 51.309

(d)(4), it is shown that greater reasonable progress will be achieved for these additional Class I

areas (e.g., Fitzpatrick and Bridger Wilderness 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

Jeff A Sorkin

Rick Graw

Scott A Copeland

Ann Acheson

6 Midwest RPO Interim White Paper - EGUs. March 2006