Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 1 ENVIRON 

# 6 Air Quality Impact Assessment

On July 23, 2012 , ENVIRON International Corporation (ENVIRON) submitted to EPA Region IV and the U.S. Fish and Wildlife Service (FWS) an Air Quality Analysis Modeling Protocol for the StatOil Gulf Services, LLC (Statoil) OCS P ermitting Project (OCS Project). ENVIRON responded to EPA and FWS comments on the protocol, which was subsequently approved by

FWS on July 30, 2012

. ENVIRON discussed the protocol with Stan Krivo of EPA Region IV on August 28, 2012 and no deficiencies we re mentioned. A copy of the approved protocol is provided in Appendix E (Attachment 1) of this application. ENVIRON followed the approved protocol in performing this air quality impact assessment. Please find attached an electronic copy of all modeling files associated with this analy sis in Appendix E (Attachment 2 )

.

As documented in Section 4.1 of this document the pollutant s subject to Prevention of Significant Deterioration ( PSD ) review for the proposed Statoil exploration activities are NO X 

### and PM 2 .5



### . Direct PM 2.5 

### emissions did not trigger PSD review, but emissions of a PM 2.5 

### precursor (NO X 

### ) is subject to PSD review. ENVIRON applied computer

- based dispersion modeling techniques to simulate dispersion of emissions attributable to the proposed explo ration activities. The results of the modeling are used to assess compliance with the PSD increments, the National Ambient Air Quality Standards (NAAQS) and Significance Impact Levels (SIL) for Class I and Class II areas. ENVIRON also used dispersion mode ling techniques to assess Class I area PSD increments and degradation of regional visibility and other Air Quality Related Values (AQRVs).

The dispersion modeling techniques employed in the analysis follow a basic set of EPA regulatory guidelines (40 CFR Part 51, Appendix W, revised November 9, 2005; referred to as the Guidelines). The Guidelines include recommendations for model selection, data preparation, and model application, but allow flexibility on a case

- by

- case basis.



## 6.1 Dispersion Model Selection
ENVIRON based its selection of the dispersion model on the characteristics of the proposed

emission sources associated with the Maersk Developer and the Transocean Discoverer

Americas drilling vessels and dispersion phenomena that might produce the maximu m ground level concentrations. ENVIRON used the CALPUFF/CALMET modeling system to estimate impacts of air pollutants at discrete receptors placed 25 nautical miles from the States’ seaward boundary, because of its design for long

- range transport applicati ons beyond 50 km. The

modeli ng domain is shown in Figure 4 as the blue box labeled “ Statoil OCS CALPUFF Domain.” ENVIRON also used the VISCREEN model (Version 88341) to perform the visibility analysis for the Additional Impacts Analysis. VISCREEN calcul ates the potential impact of a plume of specified emissions for specific transport and dispersion conditions.

A Good Engineering Practice (GEP) stack height analysis of the sources included in the modeling indicates building downwash would occur under some meteorological conditions. However, given that the nearest receptors are located more than 200 km from the source, building downwash effects will not significantly affect the results and have been ignored.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 2 ENVIRON 100 km

200 km

300 km Full Vistas Domain

Closest Lease Block Statoil OCS CALPUFF Domain

Brigantine Wilderness

Chassahowitzka Wilderness Saint Marks Wilderness

Breton Wilderness

700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

LCC (RPO Projection) Easting, km -1600 -1500 -1400 -1300 -1200 -1100 -1000

-900 -800CC o t g,



### Figure 4

. CALPUFF modeling domain (blue b ox), with “25 mile” receptors (red)Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 3 ENVIRON 

## 6.2 Model Application
ENVIRON applied CALPUFF using CALPUFF input parameters approved by EPA and the

FWS.

6.2.1 Source Characterization

The primary NO X 

### and PM 2.5 

### emission sources associated with the proposed exploration

activiti es consist of diesel

- fired engines on the drilling vessels. Additionally, the OCS air regulations define the OCS source to include direct emissions from vessels servicing the OCS

sources while en route to or from the source when within 25 miles of the fac ility. These rules require Statoil to consider impacts from the associated fleet of vessels that support the drilling

vessel.

Developer emission sources include the following:

• 

### Main Generator Engines (8)

• 

### Emergency Generator Engine (1)

• 

### Cementing Unit Engi nes (2)

• 

### Life Boats (4)

• 

### Rescue Boat (1)

• 

### Support Vessels (e.g. crew boats)

Discoverer Americas emission sources include the following:

• 

### Main Generator Engines (6)

• 

### Emergency Generator Engine (1)

• 

### Life Boats (6)

• 

### Rescue Boat (1)

• 

### Hot Oil Heater (1) 1

• 

### Emergency Air Compressor Engines (2)

• 

### Support Vessels (e.g. crew boats)

The basis for the maximum short

- term and annual emission rates modeled for these sources

are discussed in Section 6.2.4 below.

1 The cargo heater is used only twice per year fo r one hour each time, or only one hour of operation per 180

- day drilling campaign.
It therefore cannot contribute to the Class II 1

- hour NO2, 24

- hour PM2.5 values, or the Class I Visibility value (all 98 th percentile days) nor the Class I PM2.5 Increment (second high day). Its contribution to an nual average emissions is very small, several orders of magnitude smaller than any other emission unit. The cargo heater was therefore not included in the modeling scenario.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 4 ENVIRON 

### 6.2.2 Modeling Scenario

Statoil is permitting the flexibility to use either the Maersk Developer or the Transocean

Discoverer Americas drilling units to conduct exploratory drilling in the OCS of the Eastern Gulf

of Mexico. As outlined in this application, Statoil will only use one drilling vessel at any given time; theref ore, the modeling analysis only addresses one vessel operating at any time. Each drilling vessel and associated support vessels can operate under varying operating scenarios.

Statoil considered multiple operating scenarios for each drilling vessel, incl uding operations under a range of emissions and release parameters (including partial loads) and varying locations of associated support vessels. Statoil evaluated the various potential operating

scenarios to determine which emissions and release paramete rs would result in maximum impact at the modeled receptors. Because of the distance between the closest receptors and
the emissions sources, Statoil determined that maximum impacts would result from the highest

short

- term and long

- term emission rate scena rios . For the short

- term scenario s, this corresponds to the drilling vessels operating at maximum proposed load conditions. It is possible that these sources could operate at less than the maximum proposed load conditions. However, any changes in stack parameters resulting from the lower loads would not result in higher impacts at the modeled receptors. Ultimately, Statoil determined that worst

- case impacts would be represented by the operating scenario described in this section.

For each of the two mai n drilling vessel scenarios ( Maersk Developer or Transocean Discoverer

A m ericas ), Stat o il has two sets of emission rates: short

- term and long

- term.

The short

- term emission rates are used for the following assessments:

• Class II 1

- hour NO 2 

### SIL (NAAQS)

• Class I & II 24

- hour PM 2.5 

### SIL (NAAQS & PSD Increment )

• Class I visibility impairment

The long

- term emission rates are used for the remaining assessments:

• Class II annual NO 2 

### SIL (NAAQS & PSD Increment )

• Class I & II annual PM 2.5 

### SIL (NAAQS & PSD Increment )

• Class I annual NO 2 

### SIL

• Class I annual Nitrogen deposition rate

The EPA has not identified a regulatory

- default model for secondary PM 2.5 

### . Therefore, only concentrations resulting from primary PM 2.5 

### emissions will be compared to the applicable PM 2.5 

### SILs. The D eveloper maximum short

- term emissions modeling analysis is based on five Main Generator engines operating at 60 % load, auxiliary equipment (i.e., emergency generator engine , life boats, fast rescue boat and cementing unit engines) operating at 100% load an d hourly emissions for support vessels (Crew Boats and Supply Boats) are derived from theOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 5 ENVIRON 

### maximum engine operation for the respective vessels. Annual emissions for the annual modeling analysis are based on three Main Generator engines operating at 60 % loa d, all auxiliary equipment at 100% load, and support vessels based on the adjusted fuel usage or adjusted power rating (depending on the vessel type) for the proposed annual run time.

The Discoverer Americas maximum short

- term emissions are based on four M ain Generator engines operating at 80% load. Auxiliary equipment (i.e., emergency generator engine, emergency air compressor engines, life boats and fast rescue boat) operate at 100% load.

Short

- term s upport vessels (Crew Boats and Supply Boats) emission rates are derived from the

maximum engine operating rates for the respective vessels. Annual emissions are based on three Main Generator engines operating at 35% load . Annual emissions also include all auxiliary equipment at 100% load and support vessel s based on the adjusted fuel usage for the proposed annual run time.

Statoil is requesting authorization to allow the Maersk or the Transocean drilling vessels and their associated fleet to operate in any of Statoil ’s lease blocks located within the east ern Gulf of
Mexico. As such, Statoil represented worst

- case dispersion conditions as follows: Each lease block has dimensions of approximately five kilometers by five kilometers. The closest point to

shore is the northwest corner of the Desoto Canyon 143 lease block, which lies at 28. 851 o 

### N and

87. 424 o 

### W

. For purposes of this modeling analysis, Statoil modeled all scenarios from this northwest corner. This location has been selected to represent the lease blocks as a whole

because it is the closest locati on to shore and the nearest Class I area (Breton Wilderness). Therefore, Statoil expects these to be the maximum model

- predicted impacts.

The locations of the associated support vessels (i.e, Crew Boats and Offshore Support

Vessels [OSV] ) also can affec t the impacts at the receptors. Statoil has included both a crew

boat and a n OSV in the short

- term modeling scenario.

Statoil modeled the support vessels for each drilling vessel as a series of volume sources placed along a line originating at the drill ing vessel and extending out 25 miles in the direction of the Breton Wilderness. In reality, crew boats and offshore support vessels will likely take a different course than this, and may in fact take a different course when arriving at the drilling

vesse l than when departing from it. Modeling both support vessels ’ emissions as a series of

volume source s , with the worst

- case course (directly toward the Breton Wilderness) is

conservative for the maximum 24

- hour impact. 2



### The line source algorithm in CALPU FF is essentially the same as the Buoyant Line Plume (BLP) model, which was developed to handle the unique situation of aluminum reduction plants. It is not appropriate for modeling the emissions of vessels underway. Instead, the emissions were

distribut ed evenly among a series of volume sources placed evenly along the line. Statoil chose to use 10 volume sources, because 25 miles is approximately 40 km and the CALMET grid (see Section 6.2.7) uses a 4 km grid spacing. Using a finer spacing would have li ttle effect, as all the puffs originating within a grid box would “see” the same meteorology and be treated identically.

2 

### Approach discussed and approved during phone conversation with Mr. Stan Krivo on March 2, 2010.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 6 ENVIRON 

### A summary of the two sets of emission rates used in the modeling analyses by operating scenario are presented below

. It should be no ted that the maximum short

- term emission rates

are used to model 1

- hour NO 2 

### and 24

- hour PM 2.5 

### concentrations at the shoreline and Class I
receptors and assess changes in visibility at Class I area recepto rs . T he maximum annual

emission rates are used to a ssess annual

- average NO 2 

### and PM 2.5 

### concentrations at the

shoreline and Class I receptors and deposition rates at Class I area receptors.

De veloper

 Maximum short

- term ( 1

- hour and 24

- hour) emission rates:

• Five Main Generator engine s at 60 % load

• Auxiliary dri lling vessel equipment (i.e., emergency generator , life boats, fast rescue boat and cementing unit engines) at 100% load

• OSV and Crew vessels present, at 100% load

 Maximum annual emission rates:

• Three Main Generator engines at 60 % load

• Auxiliary drilling v essel equipment (i.e., emergency generator , life boats, fast rescue boat and cementing unit engines) at 100% load

• OSV and Crew vessels present, based on maximum annual operation

Discoverer Americas

 Maximum short

- term ( 1

- hour & 24

- hour) emission rates:

• Four Main Generator engines at 80% load

• Auxiliary drilling vessel equipment (i.e., emergency generator, life boats, fast rescue boat and emergency air compressors ) at 100% load

• OSV and Crew vessels present, at 100% load

 Maximum annual emission rates:

• Three Mai n Generator engines at 35% load

• Auxiliary drilling vessel equipment (i.e., emergency generator, life boats, fast rescue boat and emergency air compressors ) at 100% load

• OSV and Crew vessels present, based on maximum annual operation

6.2.3 Stack Parameters

In a ddition to emission rates, the modeling analysis requires information regarding stack heights, building dimensions, and other exit parameters that characterize exhaust flow from emission points. These release characteristics have an important influence on the results of the analysis. Ultimately, Statoil used emission rates corresponding to the selected worst

- case impact operating scenarios discussed in Section 6.2.2

. Statoil used the stack parameters suchOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 7 ENVIRON 

### as stack heights and other exit parameters that c haracterize exhaust flow from emission points in the dispersion modeling simulations.

For stacks with a vertical discharge, Statoil used available stack parameter data (i.e., stack diameter, stack exit velocity, and stack exit temperature). For stacks w ith horizontal or angled discharges, Statoil adjusted the stack parameters to remove the plume rise due to momentum, but maintain thermal plume rise, by using a stack exit velocity of 0.001 meters per second (m/s). Exhaust stack parameters for the Develop er and Discoverer Americas drilling vessels are listed

in Tables 6. 2. 3

- 1 and Table 6. 2. 3

- 2, respectively. Stack parameters for emission sources

modeled as volume so urces are listed in Table 6. 2. 3

- 3

.

Table 6.2. 3

- 1 **Developer** Point Source Stack Parameters Used in CALPUFF Modeling Analysis

Stack Modeling

ID X

- Coord (LCC) Y

- Coord (LCC) Height (m) Elevation (m) Diameter (m) Exit Velocity

(m/s) Exit Temp (K)

Wartsila Diesel Generator Engine 1 GEN1 941.931

- 1186.229 28.93 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 2 GEN2 941.931

- 1186.228 28.93 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 3 GEN3 941.931

- 1186.229 26.82 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 4 GEN4 941.931

- 1186.228 26.82 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 5 GEN5 941.931

- 1186.300 28.93 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 6 GEN6 941.931

- 1186.302 28.93 0 0.81 0.001 623.15

Wartsila Diesel Generator Engine 7 GEN7 941.931

- 1186.300 26.82 0 0.81 0.001 623.15

Wartsila Diesel
G enerator Engine 8 GEN8 941.931

- 1186.302 26.82 0 0.81 0.001 623.15
Emergency Diesel

Generator Engine EGEN1 942.005

- 1186.225 9.45 0 0.41 0.001 888.15
Lifeboat 1 LB1 942.024

- 1186.260 19.70 0 0.89 0.001 830.15
Lifeboat 2 LB2 942.024

- 1186.270 19.70 0 0.8 9 0.001 830.15
Lifeboat 3 LB3 941.939

- 1186.256 19.70 0 0.89 0.001 830.15
Lifeboat 4 LB4 941.939

- 1186.267 19.70 0 0.89 0.001 830.15

Fast Rescue Boat Engine #1 MOB1 941.927

- 1186.264 19.70 0 1.85 0.001 773.15
Cement Unit Engine (CMU

- 1) CMU1 941.979

- 11 86.304 9.45 0 0.20 0.001 794.15
Cement Unit Engine (CMU

- 2) CMU2 941.981

- 1186.304 9.45 0 0.20 0.001 794.15Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 8 ENVIRON 

### Table 6. 2. 3

- 2
**Discoverer Americas** Point Source Stack Parameters Used in CALPUFF Modeling Analysis

Stack Modeling
ID X

- Coord (LCC) Y

- Coord (LCC) Height (m) Elevation (m) Diameter (m) Exit Velocity

(m/s) Exit Temp

(K)

Gen. Engine 1 GEN1 941.853

- 1186.259 21.33 0 1.00 16.49 640.00

Gen. Engine 2 GEN2 941.852

- 1186.261 21.33 0 1.00 16.49 640.00

Gen. Engine 3 GEN3 941.853

- 1186.262 21.33 0 1.00 16.4 9 640.00

Gen. Engine 4 GEN4 941.853

- 1186.268 21.33 0 1.00 16.49 640.00

Gen. Engine 5 GEN5 941.852

- 1186.269 21.33 0 1.00 16.49 640.00

Gen. Engine 6 GEN6 941.853

- 1186.271 21.33 0 1.00 16.49 640.00

E

- Gen. Engine EGEN 942.063

- 1186.250 21.33 0 0.60 14.1 2 640.00

Lifeboat 1 LB1 942.072

- 1186.283 12.74 0 0.05 0.001 830.15

Lifeboat 2 LB2 942.072

- 1186.247 12.74 0 0.05 0.001 830.15

Lifeboat 3 LB3 942.061

- 1186.283 12.74 0 0.05 0.001 830.15

Lifeboat 4 LB4 942.061

- 1186.247 12.74 0 0.05 0.001 830.15

Lifebo at 5 LB5 941.843

- 1186.282 12.74 0 0.05 0.001 830.15

Lifeboat 6 LB6 941.843

- 1186.248 12.74 0 0.05 0.001 830.15

MOB Engine 1 MOB 942.050

- 1186.285 12.74 0 0.11 0.001 830.15

Air Compressor 1 ACOMP1 941.843

- 1186.282 15.85 0 0.04 0.001 773.00

Air Compres sor 2 ACOMP2 941.843

- 1186.282 1.83 0 0.04 0.001 773.00Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 9 ENVIRON 

### The volume sources used to simulate the crew boat and offshore support vessels within

25 miles of the drilling ves sels require a height, elevation, and initial lateral ( σ y 

### ) and vertical ( σ z 

### ) dispersion parameters. The elevation was taken to be zero (mean sea level). The height of the release was based on SCREEN3 runs performed following the precedents of the Shell C huckchi Sea permitting effort and the Shell EGOM permitting effort. Actual stack parameters, along with ship body dimensions (as building height) were input, along with stability class 4 and a wind speed of 20 m/s. The resulting plume rise is conservativ ely low. The σ y 

### was set to the center

to

- center distance between adjacent volume sources, divided by 2.15. The σ z 

### was taken to be the average height of the offshore support vessels, divided by 2.15.

Maximum short

- term ( 1

- hour and 24

- hour ) and annual emission rates for these sour ces are
summarized in Tables 6.2. 3

- 4 through 6.2. 3

- 13

. Table 6. 2. 3

- 3
Volume Source Stack Parameters for Support Vessels Used in CALPUFF Modeling Analysis

ID X

- UTM Y

- UTM Height (m) Elev (m) Sigma Y (m) Sigma Z (m)

VOL01 901.865

- 1163.096 19.41 0 2 393 13.7

VOL02 906.319

- 1165.671 19.41 0 2393 13.7

VOL03 910.773

- 1168.245 19.41 0 2393 13.7

VOL04 915.228

- 1170.820 19.41 0 2393 13.7

VOL05 919.682

- 1173.394 19.41 0 2393 13.7

VOL06 924.136

- 1175.969 19.41 0 2393 13.7

VOL07 928.591

- 1178.543 19.41 0 2393 13.7

VOL08 933.045

- 1181.118 19.41 0 2393 13.7

VOL09 937.500

- 1183.692 19.41 0 2393 13.7

VOL10 941.954

- 1186.267 19.41 0 2393 13.7Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 10 ENVIRON 

### Table 6.2. 3

- 4
Short

- Term Emission Rates from Stacks Used in **Developer** CALPUFF Modeling Analysis

Source ID NO X 

### (lb/hr) SO 2 

### (lb/hr) PM 2.5 

### (lb/hr)

GEN1 53.53 0.04 0.98

GEN2 53.53 0.04 0.9 8

GEN3 53.53 0.04 0.98

GEN4 53.53 0.04 0.98

GEN5 53.53 0.04 0.98

GEN6 0.00 0.00 0.00

GEN7 0.00 0.00 0.00

GEN8 0.00 0.00 0.00

EGEN1 38.58 0.03 0.99

LB1 0.36 0.0003 0. 02

LB2 0.36 0.0003 0. 02

LB3 0.36 0.0003 0. 02

LB4 0.36 0.0003 0. 02

MOB1 2.01 0.0 02 0. 09

CMU1 5.92 0.005 0. 13

CMU2 5.92 0.005 0. 13



### Table 6. 2. 3

- 5
Short

- term Speciated Emission Rates from Stacks

Used in **Developer** CALPUFF Modeling Analysis

Source

ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PM F (g/s)

GEN1 5.47E

- 03 2.97E

- 03 6.75E+00 0 1.54E

- 04 9.19E

- 02 2.78E

- 02 0 0

GEN2 5.47E

- 03 2.97E

- 03 6.75E+00 0 1.54E

- 04 9.19E

- 02 2.78E

- 02 0 0

GEN3 5.47E

- 03 2.97E

- 03 6.75E+00 0 1.54E

- 04 9.19E

- 02 2.78E

- 02 0 0

GEN4 5.47E

- 03 2.97E

- 03 6.75E+00 0 1.54E

- 04 9.19E

- 02 2.78E

- 02 0 0

GEN5 5.47E

- 03 2.97E

- 03 6.75E+00 0 1.54E

- 04 9.19E

- 02 2.78E

- 02 0 0

GEN6 0 0 0 0 0 0 0 0 0

GEN7 0 0 0 0 0 0 0 0 0

GEN8 0 0 0 0 0 0 0 0 0

EGEN1 3.49E

- 03 3.75E

- 03 4.86E+00 0 1.94E

- 04 1.16E

- 01 3.52E

- 02 0 0

LB1 3.97E

- 05 8.62E

- 05 4.51E

- 02 0 4 .47E

- 06 2.67E

- 03 8.09E

- 04 0 0

LB2 3.97E

- 05 8.62E

- 05 4.51E

- 02 0 4.47E

- 06 2.67E

- 03 8.09E

- 04 0 0

LB3 3.97E

- 05 8.62E

- 05 4.51E

- 02 0 4.47E

- 06 2.67E

- 03 8.09E

- 04 0 0

LB4 3.97E

- 05 8.62E

- 05 4.51E

- 02 0 4.47E

- 06 2.67E

- 03 8.09E

- 04 0 0

MOB1 2.23E

- 04 3.23E

- 04 2.53E

- 0 1 0 1.67E

- 05 1.00E

- 02 3.03E

- 03 0 0

CMU1 6.85E

- 04 4.96E

- 04 7.46E

- 01 0 2.57E

- 05 1.54E

- 02 4.65E

- 03 0 0

CMU2 6.85E

- 04 4.96E

- 04 7.46E

- 01 0 2.57E

- 05 1.54E

- 02 4.65E

- 03 0 0Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 11 ENVIRON 

### Table 6.2. 3

- 6 Long

- Term Emission Rates From Stacks Used In **Developer** CALPUFF Modelin g Analysis

Source ID NO X 

### (tpy) SO 2 

### (tpy) PM 2.5 

### (tpy)

GEN1 

### 115.63 0.09 2.13

GEN2 

### 115.63 0.09 2.13

GEN3 

### 115.63 0.09 2.13

GEN4 

### 0 0 0

GEN5 

### 0 0 0

GEN6 

### 0 0 0

GEN7 

### 0 0 0

GEN8 

### 0 0 0

EGEN1 

### 0.76 0.00 7 0.02

LB1 

### 0.00 2 0.0000 02 0. 0001

LB2 

### 0.00 2 0.0000 02 0. 0 001

LB3 

### 0.00 2 0.0000 02 0. 0001

LB4 

### 0.00 2 0.0000 02 0. 0001

MOB1 

### 0.01 0.0000 1 0. 0005

CMU1 

### 0.18 0.00 02 0.00 4

CMU2 

### 0.18 0.00 02 0.00 4



### Table 6.2. 3

- 7 Long

- Term Speciated Emission Rates from Stacks

Used in **Developer** CALPUFF Modeling Analysis

Sour ce ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PMF (g/s)

GEN1 2.69E

- 03 1.46E

- 03 3.32E+00 0 7.57E

- 05 4.52E

- 02 1.37E

- 02 0 0

GEN2 2.69E

- 03 1.46E

- 03 3.32E+00 0 7.57E

- 05 4.52E

- 02 1.37E

- 02 0 0

GEN3 2.69E

- 03 1.46E

- 03 3.32 E+00 0 7.57E

- 05 4.52E

- 02 1.37E

- 02 0 0

GEN4 0 0 0 0 0 0 0 0 0

GEN5 0 0 0 0 0 0 0 0 0

GEN6 0 0 0 0 0 0 0 0 0

GEN7 0 0 0 0 0 0 0 0 0

GEN8 0 0 0 0 0 0 0 0 0

EGEN1 1.57E

- 05 1.69E

- 05 2.18E

- 02 0 8.74E

- 07 5.22E

- 04 1.58E

- 04 0 0

LB1 5.43E

- 08 1.18E

- 07 6.16E

- 05 0 6.11E

- 09 3.65E

- 06 1.11E

- 06 0 0

LB2 5.43E

- 08 1.18E

- 07 6.16E

- 05 0 6.11E

- 09 3.65E

- 06 1.11E

- 06 0 0

LB3 5.43E

- 08 1.18E

- 07 6.16E

- 05 0 6.11E

- 09 3.65E

- 06 1.11E

- 06 0 0

LB4 5.43E

- 08 1.18E

- 07 6.16E

- 05 0 6.11E

- 09 3.65E

- 06 1.11E

- 06 0 0

MOB1 3.05E

- 07 4.42E

- 07 3.4 6E

- 04 0 2.29E

- 08 1.37E

- 05 4.14E

- 06 0 0

CMU1 4.68E

- 06 3.39E

- 06 5.10E

- 03 0 1.76E

- 07 1.05E

- 04 3.18E

- 05 0 0

CMU2 4.68E

- 06 3.39E

- 06 5.10E

- 03 0 1.76E

- 07 1.05E

- 04 3.18E

- 05 0 0Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 12 ENVIRON 

### Table 6.2. 3

- 8
Short

- Term Emission Rates From Stacks Used In
**Discoverer Americas** CA LPUFF Modeling Analysis

Source ID NO X 

### (lb/hr) SO 2 

### (lb/hr) PM 2.5 

### (lb/hr)

GEN1 127.04 0.08 1.85

GEN2 127.04 0.08 1.85

GEN3 127.04 0.08 1.85

GEN4 127.04 0.08 1.85

GEN5 0 0 

### 0

GEN6 0 0 

### 0

EGEN 49.90 0.03 1.21

LB1 0.44 0.0004 0.03

LB2 0.44 0.0004 0.03

LB3 0.44 0.0004 0.03

LB4 0.44 0.0004 0.03

LB5 0.44 0.0004 0.03

LB6 0.44 0.0004 0.03

MOB 2.61 0.002 0.11

ACOMP1 0.62 0.0005 0.03

ACOMP2 0.84 0.0007 0.04



### Table 6.2. 3

- 9
Short

- Term Speciated Emission Rates From Stacks
Used In **Discoverer A mericas**  CALPUFF Modeling Analysis

Source ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PMF (g/s)



### GEN1 1.03E

- 02 5.58E

- 03 1.60E+01 0 2.89E

- 04 1.73E

- 01 5.24E

- 02 0 0



### GEN2 1.03E

- 02 5.58E

- 03 1.60E+01 0 2.89E

- 04 1.73E

- 01 5. 24E

- 02 0 0



### GEN3 1.03E

- 02 5.58E

- 03 1.60E+01 0 2.89E

- 04 1.73E

- 01 5.24E

- 02 0 0



### GEN4 1.03E

- 02 5.58E

- 03 1.60E+01 0 2.89E

- 04 1.73E

- 01 5.24E

- 02 0 0



### GEN5 0 0 0 0 0 0 0 0 0



### GEN6 0 0 0 0 0 0 0 0 0



### EGEN 4.24E

- 03 3.63E

- 03 6.29E+00 0 1.88E

- 04 1.13E

- 01 3.41E

- 02 0 0



### LB1 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### LB2 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### LB3 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### LB4 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### LB5 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### LB6 4.93E

- 05 8.54E

- 05 5.59E

- 02 0 4.43E

- 06 2.65E

- 03 8.01E

- 04 0 0



### MOB 2.90E

- 04 3.35E

- 04 3.29E

- 01 0 1.74E

- 05 1.04E

- 02 3.14E

- 03 0 0



### ACOMP1 6.85E

- 05 7.91E

- 05 7.77E

- 02 0 4.10E

- 06 2.45E

- 03 7 .42E

- 04 0 0



### ACOMP2 9.31E

- 05 1.08E

- 04 1.06E

- 01 0 5.57E

- 06 3.33E

- 03 1.01E

- 03 0 0Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 13 ENVIRON 

### Table 6.2. 3

- 1 0 Long

- Term Emission Rates From Stacks Used In **Discoverer**
**Americas** CALPUFF Modeling Analysis

Source ID NO X 

### (tpy) SO 2 

### (tpy) PM 2.5 

### (tpy)

GEN1 

### 140.8 0.08 1.75

GE N2 

### 140.8 0.08 1.75

GEN3 

### 140.8 0.08 1.75

GEN4 

### 0 0 0

GEN5 

### 0 0 0

GEN6 

### 0 0 0

EGEN 

### 1.0 0.0007 0.02

LB1 

### 0.003 0.000002 0.0002

LB2 

### 0.003 0.000002 0.0002

LB3 

### 0.003 0.000002 0.0002

LB4 

### 0.003 0.000002 0.0002

LB5 

### 0.003 0.000002 0.0002

LB6 

### 0.003 0.000002 0. 0002

MOB 

### 0.02 0.00001 0.0007

ACOMP1 

### 0.002 0.000002 0.00008

ACOMP2 

### 0.003 0.000002 0.00011Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 14 ENVIRON 

### Table 6.2. 3

- 1 1 Long

- Term Speciated Emission Rates From Stacks Used In
**Discoverer Americas** CALPUFF Modeling Analysis

Source

ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PMF (g/s)



### GEN1 2.21E

- 03 1.20E

- 03 4.04E+00 0 6.23E

- 05 3.72E

- 02 1.13E

- 02 0 0



### GEN2 2.21E

- 03 1.20E

- 03 4.04E+00 0 6.23E

- 05 3.72E

- 02 1.13E

- 02 0 0



### GEN3 2.21E

- 03 1.20E

- 03 4.04E+00 0 6.23E

- 05 3.72E

- 0 2 1.13E

- 02 0 0



### GEN4 0 0 0 0 0 0 0 0 0



### GEN5 0 0 0 0 0 0 0 0 0



### GEN6 0 0 0 0 0 0 0 0 0



### EGEN 2.00E

- 05 1.71E

- 05 2.97E

- 02 0 8.89E

- 07 5.31E

- 04 1.61E

- 04 0 0



### LB1 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05E

- 09 3.62E

- 06 1.09E

- 06 0 0



### LB2 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05 E

- 09 3.62E

- 06 1.09E

- 06 0 0



### LB3 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05E

- 09 3.62E

- 06 1.09E

- 06 0 0



### LB4 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05E

- 09 3.62E

- 06 1.09E

- 06 0 0



### LB5 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05E

- 09 3.62E

- 06 1.09E

- 06 0 0



### LB6 6.74E

- 08 1.17E

- 07 7.64E

- 05 0 6.05E

- 09 3.62E

- 06 1.09E

- 06 0 0



### MOB 3.97E

- 07 4.58E

- 07 4.50E

- 04 0 2.37E

- 08 1.42E

- 05 4.30E

- 06 0 0



### ACOM

P1 4.68E

- 08 5.40E

- 08 5.31E

- 05 0 2.80E

- 09 1.67E

- 06 5.07E

- 07 0 0



### ACOM

P2 6.37E

- 08 7.35E

- 08 7.22E

- 05 0 3.81E

- 09 2.28E

- 06 6.89E

- 07 0 0Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 15 ENVIRON 

### 6.2.4 Building Downwash (Prime Algorithm)

Building downwash is the effect of nearby structures on the flow of emissions from their respective sources. However, as discussed in Section 6.1, ENVIRON did not account for building downwash effe cts as part of the 25

- mile receptor modeling approach. Given that the nearest receptors are located more than 150 km from the source, building downwash effects will not significantly affect the modeled results. The FLMs typically do not request downwash b e included, and neither “downwash” nor “BPIP” are mentioned in either FLAG (2000) or FLAG (2008). Table 6.2

. 3

- 12
Short

- Term Speciated Emission Rates From Volume Sources Used In **Developer** and
**Discoverer Americas** CALPUFF Modeling Analysis

Source

ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PMF (g/s)

VOL01 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL02 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL03 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL04 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL05 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL06 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL07 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL08 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL09 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0

VOL10 2.44E

- 03 1.42E

- 03 2.66E+00 0 7.35E

- 05 4.39E

- 02 1.33E

- 02 0 0



### Table 6.2. 3

- 13 Long

- Term Speciated Emission Rates From Volume Sources Used In **Developer** and
**Discoverer Americas** CALPUFF M odeling Analysis

Source

ID SO 2 (g/s) SO 4 (g/s) NO x (g/s) HNO 3 (g/s) NO 3 (g/s) EC (g/s) SOA (g/s) PMC (g/s) PMF (g/s)

VOL01 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL02 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL 03 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL04 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL05 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL06 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL07 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL08 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL09 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5.75E

- 03 1.74E

- 03 0 0

VOL10 3.20E

- 04 1.86E

- 04 3.49E

- 01 0 9.61E

- 06 5. 75E

- 03 1.74E

- 03 0 0Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 16 ENVIRON 

### 6.2.5 Receptor Locations

EPA has established a policy for EGOM of using receptors placed 25 nautical miles from the nearby States’ seaward boundaries. These discr ete 25

- mile receptors were generated using the State seaward boundaries for Louisiana, Mississippi, Alabama, and Florida. The boundaries

exte n d for up to the three nautical miles for Louisiana, Mississippi and Alabama and up to nine

nautical miles for Flor ida 3 

### . ENVIRON placed discrete receptors approximately 1 km apart. The location of these receptors is shown in Figure 4 above as red dots (Note: receptors may appear

as a solid red line in Figure 4 due to low resolution). All of these receptors are over wat er ;

t herefore, terrain elevations were not used for the Class II analysis . A ll receptors were assigned an elevation of 0 m (i.e., sea level).

Class I receptors for the Breton Wilderness were taken from the NPS website 4 

### , and include elevations ranging from 0.021 to 0.375 m. These are the FLM

- specified receptors.

6.2.6 Meteorological Data

Stat o il used a three

- year meteorological CALMET dataset (2001

– 2003) which was prepared for the Visibility Improvement State and Tribal Association of the Southeast (VISTAS)

– Best Available Retrofit Technology (BART) modeling. Specifically, the 4

- km VISTAS Domain 2 dataset was used for the modeling analysis , for both the Class I and Class II assessments . The three year CALPUFF

- ready meteorological dataset was provided by the No rth Carolina Department of Environment and Natural Resources (NC DENR). This is the most recent version developed by the FLMs

, using the currently approved regulatory version of CALMET (Version 5.8, level 070623). The CALPUFF computational grid was taken to be a subset of the full VISTAS grid, using points 1 to 186 in the X direction (East) and points 56 to 163 in the Y direction (North). This sub

- domain, along with the full VISTAS domain, is shown in Figure 4

, and includes a 50 km buffer past the Class I area. The domain was extended far enough to the

East to include the 25

- mile receptors along Western Florida, and far enough South to include a 100 km buffer around the drill rig location to allow for re

- circulation of puffs.

6.3 Project Impact Assessment

T his section assesses the magnitude of concentration impacts resulting from emissions from the proposed Statoil exploration activities at the discrete shoreline receptors. If a pollutant’s calculated concentration exceeds the EPA SIL for that pollutant, th e impacts of the facility must

be assessed in the context of other increment

- consuming sources to evaluate total increment consumption. Exceeding a SIL also requires that the facility’s compliance with the applicable NAAQS be evaluated, taking into accoun t background concentrations and the contributions of significant regional sources.

As discussed previously, ENVIRON applied the CALPUFF/CALMET modeling system to simulate pollutant dispersion for three years of hourly meteorological data. ENVIRON

determin ed the highest concentrations for each discrete receptor. This section discusses the results of the modeling assessment.

3 U. S. Commission on Ocean Policy. Primer on Ocean Jurisdictions: Drawing Lines in the Water. Final Report.

4 http://www.nature.nps.gov/air/maps/Receptors/index.cfmOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 17 ENVIRON 

### 6.3.1 Criteria Pollutant Concentrations

ENVIRON modeled the criteria pollutant concentrations using the emission rates presen ted

above in Tables 6.2. 3

- 4 through 6.2. 3

- 7 and Tables 6.2. 3

- 8 through 6.2. 3

- 11 for Developer and

Discoverer Americas drilling vessels , respectively, for comparison to the SIL and SMC for NO 2 

### and PM 2.5 

### . Tables 6.2. 3

- 12 through 6.2. 3

- 13 presented above list the short

- t erm and annual

emission rates for modeled volume sources associated with the crew boats and OSV’s used in the CALPUFF modeling analysis.

In order to assess the significance of the predictions, ENVIRON compared the maximum criteria pollutant concentrations at the discrete 25

- mile receptors predicted by CALPUFF with the Class

II PSD SIL for NO 2 

### and PM 2.5 

### . These Class II receptors with concentrations below the SILs are considered to be “insignificantly affected” and these pollutants do not require assessment s of
the Class II increments or NAAQS. 5



### Similarly, ENVIRON compared the maximum criteria pollutant concentrations at the discrete shoreline receptors predicted by CALPUFF with the applicable SMC for NO 2 

### and PM 2.5 

### . If the highest modeled concentration c aused by the proposed significant emissions increase is above the SMC, then a demonstration of pre

- construction ambient NO 2 

### or PM 2.5 

### levels would be required. However, no monitoring is required if modeling results of the significance analysis are

below th e defined SMC for NO 2 

### and PM 2.5



### .

The results of the CALPUFF modeling analysis are compared to the SIL and SMC in Table

6.3.1

- 1 . Because the maximum predicted concentration s on 1

- hour, 24

- hour, and annual

average are less than the applicable SIL s , the proj ect is deemed to not cause or contribute to a violation of the NAAQS or PSD increments for these pollutants. Furthermore, the maximum predicted concentrations are less than the applicable SMC; therefore, no monitoring is required.

5 It has been EPA's longstanding policy under the New Source Review and PSD programs to allow the use of

Significant Impact Levels (SILs) to assess whether a proposed new or modified stationary source causes or contributes to a violation of the NAAQS or PSD Class II increments (40 CFR 51.165 (b)(2)). Sources with pollutant concentrations under the SILs are considered insignificant, whether or not background or other increment consuming sources affect the applicable pollutant concentration and averaging pe riod of concern. The SIL criteria are only intended to apply to the ambient standards and Class II increments, not the Class I increments or the need to conduct an AQRV analysis (see, for example, Calcagni, 1991). Note that the use of the term "significan t" impact level in the PSD program does not imply a “significant adverse impact” in a NEPA sense, nor does it imply exceedances of ambient standards established to protect health and welfare.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 18 ENVIRON 

### Table 6.3.1

- 1

Maximu m CALPUFF

- Predicted Class II Concentrations

Criteria
Pollutant Averaging
Period **Developer**
Max.
Concentration (μg/m 3 

### ) **Discoverer**
**Americas** Max.
Concentration (μg/m 3 

### ) Modeling Significance
Level (μg/m 3 

### ) Monitoring
DeMinimus
Concentration (μg/m 3 

### )

NO 2 a 1

- hr b 3.4 5.0 7.5 c None c

Annual 0.01 0.01 1.0 14

PM 2.5 24

- hr b 0.10 0. 07 1.2 4

Annual 0.001 0.001 0.3 None

Not

es:

a NO X was assumed to be 100 percent converted to NO 2

.

b 100 th percentile (maximum) values are presented (not 98 th percentile) using direct PM 2.5 emissions only.

c Interim SIL, established June 28, 2010 in the memo “Guidanc e Concerning the

Implementation of the 1

- hour NO2 NAAQS for the Prevention of Significant Deterioration Program. The 1

- hour NO 2 Monitoring DeMinimus levels have not yet been proposed.

.



### 6.4 Class I Air Quality Related Values Analysis
PSD guidance require s an analysis of potential impacts to AQRVs in Federal Class I areas within 100 km (62.1 miles) of the facility from pollutants emitted by the project subject to PSD review. However, Federal Land Managers (FLMs) typically request analyses of AQRV impacts for Class I areas within 200 km (124 miles) of the site. BART exemption and determination modeling under EPA’s Regional Haze Regulations require that Class I areas within 300 km (186 miles) be included. A larger domain similar to that developed for BART modeling was used for this analysis, resulting in the inclusion of Class I areas beyond those usually required for a PSD analysis. Figure 4 presented above documents the CALPUFF modeling domain with

the selected Class I area.

As shown previously in Figu re 4 , there is one Class I area within 300 km of the facility. The nearest Class I area, the Breton Wilderness Area, is located at a distance of 175 km ( 109 miles) from the nearest proposed OCS Project lease block area. Statoil contacted the FWS to discu ss the proposed OCS Project and AQRV analysis. Statoil also submitted the modeling protocol to
the FWS on July 23, 2012 , which was subsequently approved on July 30, 2012

. 6



### The distances from the proposed Statoil exploration activities to the four closest Class I areas considered in this analysis are listed in Table 6.4

- 1

.

6 Email correspondence from Jill Webster, dated July 30, 2012.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 19 ENVIRON 

### Table 6.4

- 1 Nearest Distance to Class I Area from Proposed Project

ID Class I Area Distance 1 

### (Km)

BRET Breton Wilderness Area 175

BRBA Bradwell Bay Wilderness Area 307

STMA Saint Marks Wilderness Area 313

CHAS Chassahowitzka Wilderness Area 641

Notes:

a Distance to the northwest corner of Desoto Canyon 143 lease block (28. 85064 o N and

87. 42378 o W)



### The Breton, Chassahowitzka

, and Saint Marks Wilderness Areas are managed by the F WS. The Bradwell Bay Wilderness Area is managed by the FS. The AQRVs of concern include visibility, soil, flora, fauna, and aquatic resources. The CALPUFF modeling system is currently recommended for evaluating impacts to AQRVs in Class I areas affected by long

- range transport. Potential impacts are characterized based on predictions of total nitrogen and/or sulfur deposition flux, change in light extinction, and pollutant concentrations. Pollutant concentration predictions were also used to assess Cla ss I area increment consumption for pollutants subject to PSD review.

6.4.1 Model Selection
On April 15, 2003, EPA adopted the CALPUFF modeling system as the EPA’s preferred model for long

- range transport assessments and for evaluating potential impacts to Cla ss I areas by including CALPUFF in Appendix A of the Guidelines. Features of the CALPUFF modeling system include the ability to consider: secondary aerosol formation; gaseous and particle deposition; wet and dry deposition processes; complex three

- dimensi onal wind regimes; and the effects of humidity on regional visibility. As is currently required, CALPUFF Version 5.8 (release date June 23, 2007) was used.

6.4.2 Modeling Procedures
The modeling procedures used for the Class I area analyses followed the recomme ndations of the Interagency Agency Workgroup on Air Quality Modeling (IWAQM) and the FLM Air Quality Related Values Workgroup (FLAG), outlined in the FLAG Phase I Report

- Revised (June 2008). EPA endorsed these procedures in advance of the IWAQM Phase II report (December 1998), and reiterated this endorsement in the April 15, 2003 Federal Register notice (Volume 68, Number 72) that adopted CALPUFF as a Guideline model. EPA further clarified their required CALMET setting in a memo issued on August 31, 200 9 (Fox 2009). 7



### 6.4.3 Model Setup and Application

The CALPUFF modeling system is equipped with a host of modeling options, but, as stated in the previous section, ENVIRON used the procedures and defaults recommended by the FLAG

7 USEPA Memorandum. Clarification on EPA

- FLM Recommended Settings for CALMET. August 2009.

http://www.epa.gov/ttn/scram/CALMET%20CLARIFICATION.pdfOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 20 ENVIRON 

### Phase I Report. Any deviations fr om the defaults were approved by the FLM. CALPUFF control parameters are listed in Appendix A of the Modeling Protocol.

For the regional haze assessment using the CALPUFF modeling system, particulate matter emission rates must be speciated into six fracti ons: soot or elemental carbon (EC), PM fine (PMF), PM coarse (PMC), organic carbon (OC), sulfate (SO 4 

### ), and nitrate (NO 3 

### ). Table s provided in Section 6.2.3 presented the speciated particulate matter emission rates used in the analysis. The speciation was based on speciation profiles recommended for aerosol modeling by the EPA. 8 

### Sources in the database are referenced by Source Classification Code (SCC), and the database provided information for speciating the fine fraction into the other components requi red by CALPUFF. All the emission units are diesel

- fired and appropriate SCC codes were

chosen.

The CALPUFF modeling conservatively used the maximum short

- term emission rate (1

- hour)

for the short

- term assessment assessments. As previously discussed, the maximum short

- term emission rates for support vessels are based on maximum 24

- hour fuel usage. Maximum short

term emission rates for main engines on the drill rigs are based on maximum expected hourly operating loads, as discussed in Section 6.2.3.

6.4.4 Averag ing Periods

CALPUFF

- predicted hourly pollutant concentrations were averaged for comparison with applicable 1

- hour and annual NO 2 

### and 24

- hour and annual PM 2.5 

### Class I SILs and PSD increments. Predicted extinction coefficients and total deposition fluxes we re calculated as 24

- hour and annual averages, respectively. In all instances, comparisons with regulatory criteria were based on the highest model

- prediction of the three

- year simulation for the averaging period.

6.4.5 Chemical Transformations

The NO X 

### chemistry in CALPUFF depends on the ambient ammonia concentration to establish the equilibrium between gaseous nitric acid and ammonium nitrate. However, ambient ammonia concentrations are not explicitly simulated by CALPUFF and the user must select an appropriate background concentration. The IWAQM Phase II Recommendations suggest typical ammonia concentrations as: 10 parts per billion (ppb) for grasslands, 0.5 ppb for forests, and 1 ppb for arid lands during warmer weather. Given the low background concentratio n over the Gulf of Mexico and as requested by the FLM, ENVIRON used a background ammonia concentration of 3 ppb.

Reaction rates in the CALPUFF chemistry algorithms are also influenced by background ozone concentrations. ENVIRON used hourly ozone data for 2 001

- 2003 to represent background ozone concentrations for the modeled years. This data was included in the VISTAS CALMET data. CALPUFF uses a background ozone value (BCK03) for hours when none of the supplied

ozone stations have valid data. A conservativ e value of 65 ppb was specified, to avoid artificially limiting chemical transformations (e.g. NO X 

### titration).

8 USEPA website containing PM speciation for source categories: http://www.epa.gov/ttn/chief/emch/speciation.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 21 ENVIRON 

### 6.4.6 Domain and Receptors
The domain for the CALPUFF simulations is shown in Figure 4 . The 740 km

- by

- 428 km domain is large enough to include the C lass I areas of interest with at least a 50 km allowance for complex flows that might cause recirculation of plumes originating at the lease block Desoto Canyon (DC) 143

. A Lambert Conformal Coordinate (LCC) system was used for the

coordinates.

The CALPUF F dispersion model simulations assessed AQRVs at discrete receptors obtained from the National Park Service. Figure 4 also shows the discrete receptor locations within the

Breton Class I area. 9 

### Gridded receptors were turned off in the CALPUFF runs to mak e the

runtimes more reasonable.

6.4.7 Emission Rates and Stack Parameters

Modeled emission rates are discussed in Section 6.2. 3 above.

6.4.8 Meteorological Data

Preprocessed VISTAS

- BART 4 km Domain 2 CALMET data was used for modeling. This data was provided by the N orth Carolina Department of Environment and Natural Resources (NCDENR). Data from 109 surface stations, 10 upper air stations, nine overwater stations and 96 precipitation stations was used to process the 2001 CALMET data. Data from 100 surface
stations, 1 0 u pper air stations, nine overwater stations and 92 precipitation stations was used to process the 2002 CALMET data. Data from 116 surface stations, 10 upper air stations, nine overwater stations and 103 precipitation stations was used to process the 2003 CALMET data.

This is the most recent version developed by the FLM using the currently approved regulatory version of CALMET (Version 5.8). For the current analysis the 4

- km mesh size simulations were used in order to better resolve the flow in the compl ex terrain.

CALMET (Version 5.8), the meteorological preprocessor component of the CALPUFF system,
was used to combine the MM5 simulation data, surface observations, terrain elevations, and land use data into the format required by the dispersion modeling component CALPUFF. In addition to specifying the three

- dimensional wind field, CALMET also estimates the boundary layer parameters used to characterize diffusion and deposition by the dispersion model.

Selected hours of the three

- year CALMET/MM5 three

- di mensional data set were examined by extracting data from the CALMET output files and plotting the meteorological fields with the CALDESK software package. Wind vector plots were examined for different times of year, different times of day, and for all 10 vertical levels.

6.4.9 AQRV Calculation Procedures

The CALPUFF modeling system was used to predict criteria pollutant concentrations, total deposition fluxes, and light extinction coefficients attributable to project emissions in regional Class I areas. These p arameters were calculated from CALPUFF output files using the post

processor programs CALPOST and POSTUTIL.

9 http://www2.nature.nps.gov/air/Maps/Receptors/index.cfmOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 22 ENVIRON 

### Predictions of NO 2 

### and PM 2.5 

### concentrations in the Class I areas of interest were extracted from

the annual and short

- term emission cases using the CALPOST post

- processor. Total nitrogen deposition fluxes are calculated by summing and converting the various species included in the wet and dry deposition CALPUFF output files. The nitrogen deposition fluxes include the nitrogen from the background amm onia to some extent. For comparison to FLM deposition criteria, the fluxes were converted to kilograms per hectare per year.

6.4.10 FLAG 2008 (CALPOST Method 8)

In order to provide further information, extinction coefficients were calculated using the 2008

propo sed revisions to the FLM FLAG procedures. The revised procedures employ the IMPROVE extinction equation to calculate b ext 

### (invoked with MVISCHECK=1 in CALPOST). This updated equation for extinction uses monthly relatively humidity adjustment factors with relative humidity capped at 95%. It uses annual background aerosol concentrations recommended by the FLMs for the Class I area of concern, and assesses the visibility using the

98 th 

### percentile modeled values at each receptor. In order to use Method 8, CA LPOST

Version 6.221 (Level 080724) was used to post

- process the CALPUFF output files.

For FLAG 2008, a Project’s extinction is calculated using the revised IMPROVE reconstructed mass extinction equation as follows:

b project 

### = 2.2 × f S 

### (RH) × [Small Sulfate] + 4.8 × f L 

### (RH) × [Large Sulfate]
+ 2.4 × f S 

### (RH) × [Small Nitrate] + 5.1 × f L 

### (RH) × [Large Nitrate] + 2.8 × [Small Organic Mass] + 6.1 × [Large Organic Mass] + 10 × [Elemental Carbon] + 1 × [Fine Soil] + 0.6 × [Coarse Mass]
+ 1.7 × f SS 

### (RH) × [Sea Sal t] + Rayleigh Scattering (Site Specific) + 0.33 × [NO 2 

### (ppb)] {or as: 0.1755 × [NO 2 

### ( μ g/m 3 

### )]}
Where: [ ] indicates concentrations in μg/m 3 

### f S 

### (RH) = Relative humidity adjustment factor for small sulfate and nitrate
f L 

### (RH) = Relative humidity adjustmen t factor for large sulfate and nitrate
f SS 

### (RH) = Relative humidity adjustment factor for sea salt For Total Sulfate < 20 μg/m 3 

### : [Large Sulfate] = ([Total Sulfate] / 20 μg/m 3 

### ) × [Total Sulfate] For Total Sulfate ≥ 20 μg/m 3 

### : [Large Sulfate] = [Total Sul fate]
And: [Small Sulfate] = [Total Sulfate]

– [Large Sulfate] To calculate large and small nitrate and organic mass, substitute ({Large, Small, Total} {Nitrate, Organic Mass}) for Sulfate.

6.4.11 Analysis Results
The CALPUFF modeling system was used to predic t concentrations of NO 2 

### and PM 2.5 

### in the

Class I area of interest. Table 6.4.11

- 1 summarizes the predicted maximum NO 2 

### and PM 2.5 

### concentrations and compares them to the Class I SILs. At this point, there are two sets of Class I SILs: those proposed by E PA, and those recommended by the FLMs. These proposed andOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 23 ENVIRON 

### recommended SILs were obtained from the Federal Register, Vol. 61, No. 143, p. 38292, July
23, 1996. As shown in Table 6.4.12

- 1 , the CALPUFF simulations indicate neither the SILs nor

the increment s will be exceeded.

Table 6.4. 1 1

- 1

Maximum Predicted Class I Concentrations

Criteria Pollutant Averaging Period **Developer**
Max.
Concentration (μg/m 3 

### ) **Discoverer**
**Americas**
Max.
Concentration (μg/m 3 

### ) EPA SIL (μg/m 3 

### ) FLM SIL (μg/m 3 

### )

NO 2 a Annual 0.003 0.003 0.1 0.03

PM 2.5 b 24

- hr 0.04 0. 0 3 0.07

--

Annual 0.0005 0.000 2 0.06

--

Notes:

a NO X was conservatively assumed to b e 100 percent converted to NO 2

.

b 100 th percentile (maximum) values are presented (not 98 th percentile) using direct PM 2.5 emissions only.



### CALPUFF was also used to predict the impacts of acid

- forming compounds emitted by the project on soils and vegetat ion in the Class I area of interest. The deposition analysis results

are shown in Table 6. 4.11

- 2 . The National Park Service (NPS) has established Deposition Analysis Threshold (DAT) for nitrogen of 0.010 kg/ha/yr for Class I areas to the east of the

Missi ssippi river. 10 

### These “thresholds” are based on natural background deposition estimates culled from various research efforts, a variability factor, and a safety factor that accounts for cumulative effects. The DATs are not adverse impact thresholds, but are intended as conservative screening criteria that allow the FLMs to identify potential deposition fluxes that require their consideration on a case

- by

- cas e basis. As shown in Table 6.4. 11

- 2 , predicted maximum nitrogen deposition fluxes do not exceed th e DATs.

Table 6.4. 11

- 2 Predicted Class I Area Deposition Fluxes

**Developer Discoverer Americas** 

Class I Area of Interest Nitrogen Deposition Nitrogen Deposition

Breton Wilderness 0.0013 0. 001 4

NPS DAT 0.010 0.010



### Comparison with FLM

- recommended cri teria for regional visibility impacts is shown by calculating the change in 24

- hour extinction for each Class I receptor. The FLMs recommend in the FLAG Phase I Report that a five percent change in extinction be used to indicate a “just

10 Guidance on Nitrogen and Sulfur Deposition Analysis Thresholds, available on the FLAG internet site at

http://www2.nature.nps.gov/ard/flagfree/NSDATGuidance.htmOuter Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 24 ENVIRON 

### perceptible” change to a landscape. The CALPUFF modeling system was used to predict both the extinction coefficient attributable to emissions from the project as well as the background

extinction coefficients for that day’s meteorology. As is required, all days with more t han five percent change in extinction are disclosed. However, most of these days were likely impacted by natural obscuration (fog, drizzle, etc.). As shown in Tables 6.4. 11

- 3 and 6.4. 11

- 4 , and

summarized in Table 6.4.12

- 5 , the 98 th 

### percentile predicted c hange in extinction at Breton Wilderness using Method 8 was 4.17 percent for the Developer , and 5. 14 percent for the

Discoverer Americas emissions scenario. These results are less than the ten percent threshold established by the FLMs, indicating complian ce with the criteria.

Table 6.4.1 1

- 3 Predicted Extinction Change for Breton Wilderness, Method 8, Maersk

Date b ext a (1/Mm) Change b ext by Component c (1/Mm)

Project Bckgrnd b Total (%) SO4 NO3 OC EC PMC PMF NO2

12/08/01 3.539 23.365 26.904 15.15 0.076 3.152 0.025 0.243 0 0 0.044

02/28/01 2.421 23.114 25.535 10.48 0.071 2.134 0.015 0.149 0 0 0.052

02/19/03 2.351 23.114 25.465 10.17 0.047 2.052 0.019 0.19 0 0 0.043

11/22/03 2.104 23.235 25.339 9.06 0.052 1.765 0.025 0.246 0 0 0.015

02/27/01 1.966 23.1 14 25.08 8.51 0.048 1.791 0.011 0.104 0 0 0.011

02/21/01 1.762 23.114 24.876 7.62 0.028 1.559 0.011 0.105 0 0 0.059

03/16/03 1.748 23.085 24.834 7.57 0.031 1.61 0.009 0.089 0 0 0.01

05/01/03 1.739 23.246 24.985 7.48 0.061 1.494 0.016 0.159 0 0 0.01

04/ 05/01 1.713 23.042 24.754 7.43 0.036 1.354 0.022 0.215 0 0 0.086

02/20/03 1.667 23.114 24.782 7.21 0.019 1.449 0.013 0.126 0 0 0.061

02/20/01 1.554 23.114 24.668 6.72 0.031 1.342 0.013 0.125 0 0 0.044

12/07/01 1.551 23.365 24.916 6.64 0.028 1.381 0.011 0.102 0 0 0.03

01/28/02 1.547 23.376 24.923 6.62 0.033 1.343 0.012 0.12 0 0 0.038

11/20/02 1.4 23.235 24.635 6.03 0.016 1.295 0.006 0.061 0 0 0.023

09/17/01 1.38 23.493 24.873 5.87 0.086 0.96 0.03 0.293 0 0 0.011

04/13/02 1.199 23.042 24.241 5.21 0.029 1.114 0.005 0.046 0 0 0.005

Notes:

a Project and background extinction values for daily period that resulted in the maximum percent change in extinction.

b Background extinction derived from default annual average extinction compone nts provided
in FLAG 2010 Tables.

c Extinction coefficient components are: SO4 = fine sulfate, NO3 = fine nitrate, OC = fine organic carbon, EC = fine elemental carbon, PMC = coarse mass, PMF = fine crustal mass, NO2 = nitrogen dioxide.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 25 ENVIRON 

### Table 6 .4. 11

- 4 Predicted Extinction Change for Breton Wilderness, Method 8, Transocean

Date b ext a (1/Mm) Change b ext by Component c (1/Mm)

Project Bckgrnd b Total (%) SO4 NO3 OC EC PMC PMF NO2

12/08/01 4.574 23.365 27.938 19.57 0.01 0 4.295 0.02 0.192 0 0 0.057

02/19/03 2.914 23.114 26.028 12.61 0.007 2.68 0.015 0.15 0 0 0.061

02/28/01 2.774 23.114 25.888 12 .00 0.006 2.58 0.011 0.111 0 0 0.065

11/22/03 2.606 23.235 25.841 11.21 0.009 2.364 0.02 0.191 0 0 0.022

02/21/01 2.244 23.114 25.358 9.71 0.004 2.07 0.0 08 0.083 0 0 0.079

02/27/01 2.231 23.114 25.345 9.65 0.004 2.127 0.008 0.076 0 0 0.016

05/01/03 2.241 23.246 25.487 9.64 0.007 2.075 0.014 0.132 0 0 0.014

02/20/03 2.147 23.114 25.261 9.29 0.004 1.949 0.01 0.102 0 0 0.08

04/05/01 2.115 23.042 25.157 9. 18 0.007 1.804 0.017 0.169 0 0 0.116

03/16/03 2.008 23.085 25.093 8.7 0 0.003 1.91 0.007 0.068 0 0 0.019

02/20/01 1.989 23.114 25.103 8.61 0.005 1.813 0.01 0.1 0 0 0.062

01/28/02 2.011 23.376 25.388 8.6 0 0.005 1.848 0.01 0.097 0 0 0.051

12/07/01 1.928 2 3.365 25.293 8.25 0.004 1.792 0.009 0.085 0 0 0.038

11/20/02 1.717 23.235 24.952 7.39 0.002 1.634 0.004 0.044 0 0 0.033

09/17/01 1.636 23.493 25.129 6.96 0.012 1.35 0.024 0.235 0 0 0.014

04/13/02 1.566 23.042 24.608 6.8 0 0.002 1.516 0.004 0.038 0 0 0.00 7
01/29/02 1.371 23.376 24.747 5.86 0.005 1.165 0.01 0.098 0 0 0.093

05/26/02 1.358 23.246 24.604 5.84 0.004 1.258 0.008 0.079 0 0 0.01

07/08/03 1.291 23.733 25.024 5.44 0.008 1.036 0.015 0.15 0 0 0.081

11/26/03 1.219 23.235 24.454 5.25 0.004 1.077 0.0 1 0.095 0 0 0.032

01/17/02 1.214 23.376 24.591 5.19 0.003 1.149 0.006 0.054 0 0 0.003

03/11/01 1.187 23.085 24.272 5.14 0.002 1.093 0.006 0.055 0 0 0.032

10/26/02 1.186 23.221 24.407 5.11 0.002 1.044 0.004 0.04 0 0 0.095

04/24/01 1.158 23.042 24.2 5.03 0.003 1.025 0.007 0.072 0 0 0.05

Notes:

a Project and background extinction values for daily period that resulted in the maximum percent change in
extinction.

b Background extinction derived from default annual average extinction componen ts provided in FLAG
2010 Tables.

c Extinction coefficient components are: SO4 = fine sulfate, NO3 = fine nitrate, OC = fine organic carbon, EC = fine elemental carbon, PMC = coarse mass, PMF = fine crustal mass, NO2 = nitrogen dioxide.



### Table 6.4. 11

- 5 Maximum Predicted Extinction Change for Breton Wilderness, Method 8 Summary

Criteria **Developer Discoverer** 
**Americas**

Highest Value 15.15 19.57

Number Days > 5% change 16 24

Number Days > 10% change 3 4

98 th Percentile Change, 2001 5.87 6.96

98 th Perc entile Change, 2002 4.06 4.93

98 th Percentile Change, 2003 4.19 4.31

98 th Percentile Change over 3 years 4.17 5.14Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 26 ENVIRON 

### 6.5 Additional Impacts Assessment
An additional impacts analysis was performed in accordance with PSD requirements (40 CFR 52.21(o)). The an alysis evaluates the potential impacts that the proposed Statoil exploration activities could have on growth, soils, vegetation, and visibility in the area surrounding the proposed drilling locations.

6.5.1 Growth Analysis

Statoil examined the potential growth in industrial, commercial and residential sources as a result of the proposed DeSoto Canyon and Lloyd Ridge drilling exploration activities and determined that no growth is expected. This determination was reached based on Statoil ’ s deep understand ing of the robust and well developed oil and gas industry that currently supports exploration activities in the area just west of the proposed drilling activities. It is expected that the current infrastructure is more than adequate to support the propos ed drilling activities and thus no growth is expected.

6.5.2 Soil and Vegetation Impacts

The PSD draft guidelines prescribe that the potential impacts of the proposed project on the soils and vegetation in the vicinity of the facility should be considered. As approved in the modeling protocol

, due to the location of the proposed exploration activities in the eastern Gulf of Mexico, no impact to local soils or vegetation is expected.

6.5.3 Local Visibility Impairment

Local visibility analysis was conducted u sing the EPA plume impact screening model (VISCREEN, version 1.01). VISCREEN calculates the potential visual impact of a plume of specified emissions for specific transport and dispersion conditions. A VISCREEN Level I analysis was conducted to estimate if the proposed exploration activities could result in an adverse impact on visibility for the closest Class II area receptor. The closest Class II area receptor to the lease block in the Gulf of Mexico was located on the edge of the Mississippi
Delta, ov er 50km away. To maintain a conservative analysis , and because VISCREEN is not applicable beyond 50km , 50km was used as the source to class I area distance. Level I analysis utilizes particulate matter and NO

x 

### emission rates as inputs, while using defaul t values for background ozone, stability class and wind speed. The default background ozone concentration is 0.04 ppm, while default stability and wind speed are 6 and 1 m/s, respectively. The model conservatively evaluates whether a plume from Developer or Discoverer Americas drilling vessels and associated support vessels is perceptible to an observer under worst case meteorological conditions from a known distance. Several angles between the observer’s line of sight and the sun’s radiation (θ) are consi dered. The input emission rates for Developer or
Discoverer Americas drilling vessels and associated support vessels are listed in Tables 6.5.3

- 1

and 6.5.3

- 2. The default input parameters are listed in Table 6.5.3

- 3.Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 27 ENVIRON 

### Table 6.5.3

- 1
Level I **Developer** VIS CREEN Analysis Input Parameters 

### Developer Short

- Term Emission

Rates Emissions ( lb/hr )

Particulate Matter 15.67 NOx (as NO 2 

### ) 778.20 Primary NO 2 

### 0 (default)

Soot 0 (default) Primary SO 4 

### 0 (default)

Table 6.5.3

- 2
Level I **Discoverer Americas** VISCREEN A nalysis Input Parameters



### Discoverer Americas Short

- Term

Emission Rates Emissions ( lb/hr )

Particulate Matter 15.67 NOx (as NO 2 

### ) 778.20 Primary NO 2 

### 0 (default)

Soot 0 (default) Primary SO 4 

### 0 (default)

Table 6 .5.3

- 3
Level I **Developer** and **Discoverer A mericas**  VISCREEN Analysis Input Parameters 

### Input Parameters Background Ozone (ppm) 0.04 Background Visual Range (km) 20 Distance: Source to Closest Class I Area (km) 50

Distance: Source to Farthest Class I Area (km) 50

Source

- Observer Distance (km) 5 0

Plume

- Source

- Observer Angle 11.25 Stability 6.0 Wind Speed (m/s) 1.0

The VISCREEN model is designed to determine whether the plume from an emission source has the potential to be traceable to an untrained observer under reasonable worst case

conditio ns. Two screening criteria are used to carry out the analysis and if either criterion is exceeded, more comprehensive analyses should be carried out. The first criterion, delta E, known as the plume perceptibility parameter is based on the difference in co lor and brightness between the plume and the background. It is also known as the color difference parameter and depends on three factors, namely, brightness (L), color hue (a) and color saturation (b).

Mathematically,

ΔE = [(ΔL) 2 

### + (Δa) 2 

### + (Δb) 2 

### ] 1/2Outer Continental She lf PSD/Title V Permit Application

Air Quality Impact Assessment 6

- 28 ENVIRON 

### T he default threshold for delta E is 2.0

The second criterion is called the green contrast value (C plume or 

### C p 

### ). C p 

### is defined as the contrast of a plume against a viewing background such as the sky or a terrain feature. Change is measured in terms of gree n color (wavelength=0.55 microns). The default threshold for C p 

### is 0.05. Level I screening results are listed in Table 6 .5.3

- 4 and Table 6 .5.3

- 5.

Table 6 .5.3

- 4
Level I **Developer** VISCREEN Results



### Background θ Distance (Source

- Observer) (km) Delta E Contrast

Critical Plume Critical Plume Sky 10 50 2.00 0.969 0.05

- 0.005 Sky 140 50 2.00 0.300 0.05

- 0.006

Terrain 10 50 2.00 0.058 0.05 0.001

Terrain 140 50 2.00 0.018 0.05 0.001

Table 6 .5.3

- 5
Level I **Discoverer Americas** VISCREEN Results



### Background θ Distance (Source

- Observer) (km) Delta E Contrast

Critical Plume Critical Plume Sky 10 50 2.00 1.337 0.05

- 0.008 Sky 140 50 2.00 0.415 0.05

- 0.009

Terrain 10 50 2. 00 0.082 0.05 0.001

Terrain 140 50 2.00 0.025 0.05 0.001

As listed in Table 6 .5.3

- 4 and Table 6 .5.3

- 5 above the default threshold for delta E and Cp was not exceeded for both sky and terrain backgrounds for either Developer or Discoverer Americas ; ther efore, the proposed exploration activities are not expected to impair the local visibility. VISCREEN modeling outputs are included in Appendix E (Attachment 3 )

.