NONO22 Increment Consumption Increment Consumption

Study in Southwest WyomingStudy in Southwest Wyoming

Ken RairighKen RairighState of Wyoming DEQ - Air Quality DivisionState of Wyoming DEQ - Air Quality Division

WESTAR Oil and Gas WorkshopWESTAR Oil and Gas WorkshopPinedale, WyomingPinedale, Wyoming

September 13, 2007September 13, 2007

BackgroundBackground

• Concerns about cumulative impact of new oil & gas development on air quality in SW WY, especially in Bridger and Fitzpatrick Wilderness (Class I areas)

• Significant growth in O&G production in Sublette Co. in last couple of years, and lots more on the way!

• Cumulative increment consumption demonstration needed NOW (Dec. 2004) to inform decision making on pending permits and future development plans

Goals & OutcomesGoals & Outcomes• Evaluate NO2 increment in Class I areas

• Evaluate impacts due to ongoing oil and gas development in Sublette County

• Evaluate significance of non-road, on-road, and oil and gas NOx sources w.r.t. increment cons.– what level of refinement is needed for the emission

inventories ?

• Develop a manageable analysis

Goals & Outcomes Cont’d.Goals & Outcomes Cont’d.

• Evaluate ISCST3, ISCLT3 and CALPUFF model predictions in near-field and “mid-field” applications– Source-Class I receptor distances = 18 -70 km

• Look at NOx sources out to 300 kilometers – current “limit” of CALPUFF based on EPA guidance

• Develop a model-ready database for ISC3 models and CALPUFF modeling system

• Produce scientifically-credible results

Regulatory Guidance Used to Regulatory Guidance Used to Develop AnalysisDevelop Analysis

• Developed all phases of NO2 increment analysis (Task 1 – Task 4) using EPA guidance:

– Revised Guideline on Air Quality Models (April 2003) *– EPA NOx increment analysis memo (~ 1993)– IWAQM Phase 2 (December 1998)– Revised Guideline on Air Quality Models (Nov. 2005)

Used current (2005) version of EPA models *

Wells and Point Sources

What is Increment ?What is Increment ?

• Developed to keep air quality in clean areas from deteriorating to ambient standards

• For NO2: Minor Source Baseline Date = Feb 26, 1988

– Changes in actual emissions from all sources after this date affect the available increment

• Increment consumption determined through dispersion modeling analyses– Pairing of model predicted concentrations in space and time

(current – baseline)

Calculation of NOCalculation of NO22 Increment Increment

• Snapshot approach:

– Model Current year (CY) annual average NO2 concentrations from all sources in EI

– Model Baseline year (BL) annual average NO2 concentrations from all sources in EI

– Subtract (CY – BL) conc. at each model receptor

NONO22 Increments Increments

• NO2 PSD Increments

– Class II: 25 ug/m3 annual average

– Class I: 2.5 ug/m3 annual average

• NO2 Ambient Air Quality Standard

– NAAQS/WAAQS: 100 ug/m3 annual average

Inside-Out MethodologyInside-Out Methodology

• Tasks 1-4 developed as modular components– Emissions Inventory was broken into “pieces”

• NO2 increment calculated for each “piece” - additive, moving outwards from the receptor grids/Sublette County

• Allowed us to:– Evaluate significance of modeled NO2 concentrations

from each source category in key areas– Vary the resolution of area sources, receptor grids, and

meteorology using key source categories in sensitivity analyses

–Minimize model run times => get answers to the boss !

D1

D2

D3

D3

D2

D3

D3

D1

NONOxx Emissions Inventory Emissions Inventory

Sublette CountySublette County

• Stationary Sources– Point Sources - Sublette County NOx sources – 2002/2004 emissions inventories– Separate source groups “actual 2004” and permitted, NYC

• Area Sources– Petroleum Field Sources– 2002/2004 Sublette County emissions by well– Drill rig emissions in Pinedale field were limited to May – Nov 15

Other Pinedale source emissions - year-round– Drill rig emissions in all other fields - year-round

NOx Emission InventoryNOx Emission Inventory Sublette County Sublette County

• Oil & Gas Production (well sites)– Actual 2002 (Task 1) and 2004 (Tasks 2-4) and 1987 inventories

• Process Heaters• Drill Rig Emissions • Well Completions/recompletions/testing

• Mobile (on-road & off-road), Agriculture, Rec Marine, Cities– Actual 2002 and 1987 (baseline) inventories

• Point Sources Sublette County (compressor stations)– Actual 2004 and 1987 (baseline) inventories– Allowable emissions for sources permitted, but not yet constructed

NOx Emissions Summary Sublette County (TPY)

Source Category 2004 1987

Pinedale drill rigs 1,804 0

Jonah-Pinedale oil & gas (except, Pinedale drill rigs) 1,104 9

Other Sublette Co. oil & gas 1,383 445

Operating (“actual”) point sources 1,039 910

Point sources, permitted but not yet constructed 563 0

Agricultural equipment 1611 182

Recreational equipment (marine and other) 58 55

Other urban area sources 59 86

On-Road vehicles 5151 766

TOTAL (TPY): 6,686 2,453

1 2002 emissions

Model Selection ??

EPA GAQM References on EPA GAQM References on Model SelectionModel Selection

– “EPA completed limited evaluation of several long range transport (LRT) models … Based on the results, EPA concluded that long range and mesoscale transport models were limited for regulatory use to a case-by-case basis.”

– “It was concluded from these case studies that the CALPUFF dispersion model had performed in a reasonable manner, and had no apparent bias toward over or under prediction, so long as the transport distance was limited to less than 300 km.”

EPA GAQM References on EPA GAQM References on Model SelectionModel Selection

• “CALPUFF is intended for use on scales from tens of meters from a source to hundreds of kilometers.”

• “CALPUFF is appropriate for long range transport (source-receptor distances of 50km to 200km) of emissions from point, volume, area, and line sources.”

EPA GAQM References on EPA GAQM References on Model SelectionModel Selection

• … “there are certain applications containing a mixture of both long range and short range source-receptor relationships in a large modeled domain.”

• “To properly analyze applications of this type, a modeling approach is needed which has the capability of combining, in a consistent manner, impacts involving both short and long range transport.”

Model SelectionModel Selection

• ISCST3, ISCLT3, and CALPUFF models– ISC3 and CALPUFF models have EPA Guideline Model

status

– ISCST3 currently has “alternative” model status under GAQM

– ISCST3 and ISCLT3 models use nearly identical algorithms to handle pollutant transport and dispersion

– CALPUFF applies puff-based advection scheme, chemistry & deposition

Task 1 ModelingTask 1 Modeling

• Initial model runs were needed to jump start IC analysis:

– 2002 EI (including Bridger and Naughton power plants in SW WY)– Existing met data for ISC3 models (Jonah site: 1999-2003)– Existing 1995 wind field (SWWYTAF study)– 4 km receptor grids in Class II areas– 2 km spacing along boundary of the Bridger-Fitzpatrick Class I areas

(as used in previous PSD increment modeling studies)– NPS receptors in the interior of the Bridger-Fitzpatrick Class I area

• Compare CALPUFF/ISC3 model predictions (annual ave.)• Evaluate Model run times

MM5 and CALMET Domains

MM5 60 km MM5 20 km

SWWYTAF CALMET

Class I Receptor Grids

540 560 580 600 620 640 660 680

4680

4700

4720

4740

4760

4780

4800

4820

NPS Class I Receptors

540 560 580 600 620 640 660 680

4680

4700

4720

4740

4760

4780

4800

4820

SWWYTAF Class I Receptors

~ 1 km spacing(http://www2.nature.nps.gov/air/Maps/Receptors)

2 km interior spacing

Class II Receptor Grids

Task 1 ModelingTask 1 Modeling

– Ran ISCST3, ISCLT3, and CALPUFF models• Modeled identical emission sources and emission rates in all

model simulations and sensitivity analyses• Compared effects of using 5 years of hourly meteorological data

1999-2004 (ISCST3) against an “annualized” version of this meteorological data (ISCLT3), and 1995 CALMET 4 km

– Obtained results within 7 weeks of contract initiation– Similar results from all three (3) models in most all cases

• Max annual NO2 (CALPUFF no-chemistry)

– Class I IC ~ 0.5 ug/m3

– Class II IC ~ 6.4 ug/m3

Task 2 ModelingTask 2 Modeling

• Updated O&G EI – 2004• Ran additional sensitivity analyses using higher

resolution terrain data• Varied area source and meteorological grid sizes• Added more receptors• Used CALPUFF to evaluate sources located within

200 km of Bridger and Fitzpatrick Class I areas• ISC/CALPUFF comparisons limited to Sublette Co

D1 Oil & Gas Area Sources - 2004

D1 Oil & Gas Area Sources - 1987

Oil & Gas Area Sources

Sensitivity AnalysesSensitivity Analyses

• Chemistry Modules

• Area source resolution

• Grid cell (meteorological) resolution

• Receptor grid resolution

• Puff splitting

• Terrain elevation (DEM) data

Chemistry ModulesChemistry Modules• Conducted CALPUFF model runs using:

1) Inert (“no chemistry”) and no deposition

2) Inert with dry NOx deposition turned on

3) MESOPUFF II chemical module

(NOx concentrations only)

4) RIVAD/ARM3 chemical module

=> NO, NO2 and NOx concentrations

Chemistry ModulesChemistry Modules

• Using RIVAD chemical module => average NO to NO2 conversion factors vary from 60% to over 90% depending on source – receptor distance

• Results from Task 2 show that the RIVAD NO to NO2 rate is higher than the rate obtained using MESOPUFF II

• Guidance on use of chemistry module is not specific to increment modeling

Area Source ResolutionArea Source Resolution

• Sensitivity analyses - CALPUFF and ISC3– combined effect of using:

• 1 km area sources• 1 km receptor grid

– Nearly always produced the highest near-field concentrations

• No significant difference in modeled conc. at Class I areas

Grid Cell ResolutionGrid Cell Resolution

– Near-field maximum area source NO2 impacts not sensitive to the choice of 4 km or 1 km for the grid cell resolution

– Within the Class I areas, NO2 concentration differences using 1 km and 4 km were small

– Use of 1 km grid cells to model geographic areas outside of Sublette County

=> long CALPUFF run times

ISC NO2 = 0.75 * NOx CALPUFF NO2 (RIVAD chemistry)

Maximum values unpaired in space

Class II Impacts: (ISC Vs. CALPUFF)

High spatial correlation in annual average results

CALPUFF predicts ~ 30% higher near-source maximum NOx concentrations (puff recirculation ??)

Increment consumption largely independent of year-to-year meteorological variations

Need monitoring data for model performance evaluations

CALPUFF Vs. ISCConclusions

Task 2 Modeling Results• Maximum annual NO2 – CALPUFF

– 4 km meteorological data resolution– 1 km area source resolution– RIVAD chemical mechanism– No puff splitting

• Class I NO2 Increment Cons ~ 0.14 ug/m3

• Class II NO2 Increment Cons ~ 11.5 ug/m3

Selected Model Configuration Selected Model Configuration Task 3 and 4Task 3 and 4

• RIVAD chemistry module • 1 km resolution for area sources inside Sublette County,

4 km everywhere outside• 4 km grid cell (meteorological) resolution• 4 km receptor grid over all of Sublette Co. and 1 km

receptor grid over highest areas of NOx emissions

• Use NPS receptor grid in Class I areas• Puff splitting option turned off• 7.5 minute DEM data for terrain in WY

NOx Inventory by DomainCurrent

  D1 D2 D3 NWP Totals

Oil and Gas 4,635 10,222 2,647 17,504

Point Sources 1,602 60,953 4,628 6,027 73,210

On-Road 428 17,475 17,861 35,764

Locomotive 12,632 34,463 47,095

Other Area 281 2,538 5,621 8,440

Totals 6,946 103,820 65,220 6,027 182,013

Baseline

  D1 D2 D3 NWP Totals

Oil and Gas 455 2,043 1,818 4,316

Point Sources 910 57,595 894 9,224 68,623

On-Road 592 18,091 20,033 38,716

Locomotive 10,114 26,546 36,660

Other Area 324 3,211 7,580 11,115

Totals 2,281 91,054 56,871 9,224 159,430

           

% Change above Baseline 67% 14% 15% (53%) 14%

BASELINE OIL & GAS AND POINT SOURCES

CURRENT OIL & GAS AND POINT SOURCES

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km)

-20

0

20

40

60

80

100

LC

Py

(km

)

0

0.5

1

1.5

2

2.5

3

4

5

6

8

ug/m3

Class II area max NO2

Baseline NO2 ConcentrationAll Wyoming (D1xx and D2) and non-WY Sources

** 1995 LCP Meteorology **

Maximum Modeled NO2 Conc = 8.87 ug/m3

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km)

-20

0

20

40

60

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100

LC

Py

(km

)

0

0.5

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1.5

2

2.5

3

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ug/m3

Class II area max NO2

Current Year NO2 ConcentrationAll Wyoming (D1xx and D2) and non-WY Sources

** 1995 LCP Meteorology **

Maximum Modeled NO2 Conc = 14.29 ug/m3

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km)

-20

0

20

40

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100

LC

Py

(km

)

-0.5

0

0.5

1

1.5

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2.5

3

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5

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ug/m3

Class II area max NO2 increment consumption

NO2 Increment ConsumptionAll Wyoming (D1xx and D2) and non-WY Sources

** 1995 LCP Meteorology **

Class II NO2 Increment = 25 ug/m3

Class II NO2 Increment Consumed = 13.22 ug/m3

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km )

-20

0

20

40

60

80

100

LCP

y (k

m)

Baseline N O 2 C oncentrations: B ridger-F itzpatrick W ilderness A reasA ll W yom ing (D 1xx, D 2) and non-W Y Sources**1995 LC P M eteoro logy**

ug/m 3

C lass I A rea M ax Value

0

0.05

0.1

0.15

0.2

0.25

0.3

0.4

0.5

Maximum Modeled NO2 Conc = 0.41 ug/m3

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km )

-20

0

20

40

60

80

100

LCP

y (k

m)

C urrent Year N O 2 C oncentrations: B ridger-F itzpatrick W ilderness A reasA ll W yom ing (D 1xx, D 2) and non-W Y Sources**1995 LC P M eteoro logy**

ug/m 3

C lass I A rea M ax Value

0

0.05

0.1

0.15

0.2

0.25

0.3

0.4

0.5

Maximum Modeled NO2 Conc = 0.66 ug/m3

-160 -140 -120 -100 -80 -60 -40 -20

LCPx (km )

-20

0

20

40

60

80

100

LCP

y (k

m)

N O 2 Increm ent C onsum ption: B ridger-F itzpatrick W ilderness A reasA ll W yom ing (D 1xx, D 2) and non-W Y Sources**1995 LC P M eteoro logy**

ug/m 3

C lass I A rea M ax Value

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

Class I NO2 Increment = 2.5 ug/m3

Class I NO2 Increment Consumed = 0.26 ug/m3

CALPUFF Run Times

0

20

40

60

80

100

120

140

160

180

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

No. of Receptors

Ho

urs

234 Sources465 Sources36 Sources

y = 0.0441x + 5.2514R2 = 0.8516

0

5

10

15

20

25

30

35

0 100 200 300 400 500 600 700No. of Sources

Wa

ll C

loc

k D

ay

s t

o C

om

ple

te

CALPUFF Run Times

Final ResultsFinal Results

Bridger/Fitzpatrick Class I Areas

Class II Areas

Final Results

ResourcesResources• Class I NO2 Increment Consumption:

– D1 (Sublette Co.) sources = 82 % of “the answer”– D1 sources = 4% of the total CY emissions inventory

– D2 (SW Wyoming) sources = 13% of “the answer”– D2 sources = 57% of the total CY emissions inventory

– D3 (Western WY) sources < 1% of “the answer”– D3 sources = 36% of the total CY emissions inventory

• Model run time ~ 1 week

• Model run time ~ 1 month

• Model run time ~ 3 months

ConclusionsConclusions

• NO2 Class I and Class II increments not threatened

• NO2 increment consumption between 1987 and 2004 in the analysis area predominately due to the oil & gas field sources in SW WY, reflecting the increased development during this period– Bulk of which occurred in the JPDA– Oil & gas sources are largest contributors to NO2 increment consumption in

Class I area and Class II areas

• Growth in point sources further contributed to increment consumption

• Need to continue tracking increment as O&G development progresses

• Focus on sources located in D1 and D2

Questions