## Shell Chukchi Sea Exploration Plan
Revision 2 Environmental Impact Assessment

Attachment B
Air Quality Technical Report

On s hore Areas

Prepared for: Bureau of Ocean Energy Management Anchorage, Alaska

On behalf of:
Shell Gulf of Mexico Inc. Anchorage, Alaska

Prepared by: ENVIRON International Corporation Lynnwood, WA

Date:
March 2015

Project Number:
2922291AShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 2 of 35 

## Contents
Page

List of Tables

................................ ................................ ................................ ................................ ................................ 3

List of Figures

................................ ................................ ................................ ................................ .............................. 3

Acronyms, Abbreviations, and Definitions

................................ ................................ ................................ ................ 4

Preface

................................ ................................ ................................ ................................ ................................ ......... 7

1 Summary

................................ ................................ ................................ ................................ ............................... 8

2 Project Descriptio n

................................ ................................ ................................ ................................ ............... 9

2.1 Exploration Program Activity Area

................................ ................................ ................................ ................. 9

2.2 Offshore Drilling Program Activities and Emissions Units

................................ ................................ .......... 11

2.3 Onshore Exploration Program Activities and Emissions Units

................................ ................................ ..... 12

2.4 Spatial and Temporal Relatio nships of Offshore Drilling Program Emission Units

................................ ..... 12

3 Affected Environment

................................ ................................ ................................ ................................ ........ 14

3.1 Ambient Air Quality Standards and Attainment Status

................................ ................................ ................. 14

3.2 Existing Air Quality Conditions

................................ ................................ ................................ .................... 16

3.3 Meteorological Conditions and Climate

................................ ................................ ................................ ........ 18

4 Offshore Exploration Program Analytical Methods

................................ ................................ ....................... 21

4.1 Model Configuration of Emission Units

................................ ................................ ................................ ....... 21

4.2 Dispersion Modeling

................................ ................................ ................................ ................................ ..... 22

4.2.1 Dispersion Model Selection

................................ ................................ ................................ .............. 23

4.2.2 Methods

................................ ................................ ................................ ................................ ............ 23

4.2.3 Domain

................................ ................................ ................................ ................................ ............. 23

4.2.4 Mesoscale Model Interface Format and Weather Research Forecast

................................ ............... 24

4.2.5 Secondary Aerosols

................................ ................................ ................................ .......................... 25

4.2.6 Downwash

................................ ................................ ................................ ................................ ........ 26

4.2.7 CALPUFF

................................ ................................ ................................ ................................ ......... 27

5 Drilling Program Modeling Results

................................ ................................ ................................ .................. 28

6 Onshore Activity

................................ ................................ ................................ ................................ ................. 30

6.1 Construction

- Related Air Quality

................................ ................................ ................................ .................. 30

6.2 Onshore Facilities Analytical Methods

................................ ................................ ................................ ......... 30

7 Cumulative Exploration Program Concentrations

................................ ................................ ......................... 33

8 References

................................ ................................ ................................ ................................ ........................... 34Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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## List of Tables

Table 1. Candidate Drilling Sites 1

................................ ................................ ................................ .......................... 9

Table 2. Applicable Ambient Air Quality Standards for Criteria Pollutants

................................ ........................ 15

Table 3. Maximum Existing Ambient Air Concentrations

................................ ................................ ................... 16

Table 4. Maximum Predicted Concentrations Attributable to Offshore Sources (μg/m3)

................................ .... 28

Table 5. Construction Emissions (tons per year)

................................ ................................ ................................ .. 30

Table 6. Maximum Predict ed Concentrations Attributable to Onshore Facilities (μg/m 3 )

................................ .. 31

Table 7. Summary of Cumulative Modeled Onshore Emissions (μg/m 3 )

................................ ............................ 3 4



## List of Figures

Figure 1. Project Vicinity Map

................................ ................................ ................................ .............................. 10

Figure 2. Regional Air Quality Monitoring Site Locations

................................ ................................ ................... 17

Figure 3. Wind Rose for Shell Burger Lease Area 2009

- 2010

................................ ................................ .............. 19

Figure 4. Wind Rose for Barrow, Alaska 2 008

– 2012

................................ ................................ ......................... 20

Figure 5. Orientation of Model Emissions Sources

................................ ................................ ............................... 22

Figure 6. Onshore Receptors Used in the CALPUFF Modeling

................................ ................................ ........... 24

Figure 7. Locations of Maximum Onshore Concentrati ons

................................ ................................ ................... 29

Figure 8. Receptors Used In Onshore Facility Modeling Analysis

................................ ................................ ....... 32Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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## Acronyms, Abbreviations, and Definitions

Note that in this section and throughout the rest of this report there are active hyperlinks that will jump to

the referenced material or section

. General h yperlinks are formatted like this

. Hyperlinks for tables and figures are highlighted like this

. Air quality standard

................ Health

- based standard representing a pollutant concentration in the ambient air usually over some averaging period (e.g. 1

- hour ) , intended to protect the health and welfare of people with a margin of safety.

Ambient air

............................. the air in outdoor locations to whic h the public has ready access

Area source

............................. an emission source type defined in CALPUFF . Area source emissions

are released from two

- dimensional four

- sided area s

Attainment/Nonattainment

..... a determination and classification made by EPA indicating whether

ambie nt air quality in an area complies with (i.e., attains) or fails to meet (i.e., nonattainment) the requirements of one or more NAAQS

Averaging time

....................... a specific period of time (e.g., 1 hour, 24

- hours, 1 year) over which concentrations of an air pollutant are measured or model

- calculated

. Note that some NAAQSs are also based on multi

- year averages of certain percentiles of measured or calculated concentrations.

BACT

................................ ..... Best Available Control Technology

BOEM

................................ .... Bureau of Ocean Energy Management, the regulatory agency with air quality authority in portions of the Outer Continental Shelf, part of the Department of Interior.

CALPUFF

.............................. Air quality dispersion modeling system used in this analysis. The CALPUFF modeling system consists of pre

- processors, a dispersion model and post

- processors. The meteorological preprocessor (CALMET) was not used to provide meteorological information.

Inst ead meteorological data was provided by the Weather Research and Forecasting Model (WRF) and prepared for CALPUFF input using a specially designed program called the Mesoscale Model InterFace (MMIF).

CO

................................ .......... carbon monoxide, a criteria air pollutant

CO 2

................................ ......... carbon dioxide

CO 2 e

................................ ....... Carbon dioxide equivalents (emissions of all GHGs expressed in terms of their "global warning potential")

Criteria air pollutant

............... an air pollutant specifically governed by the Federal Clean Air Act for which ambient air quality standards have b een set. Criteria air pollutants include carbon monoxide, particulate matter, sulfur dioxide, nitrogen dioxide, ozone, and lead.

Dispersion model

................... A computerized calculation tool used to estimate pollutant concentra

tions in the ambient air based on numeri c simulations that consider the

loca tions and rates of pollutant emissions and the effects of meteoro

logical conditions, usually over specific averaging times (e.g., 8

- hours)Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 5 of 35 EPA

................................ ........ US Environmental Protection Agency

hp

................................ ............ horsepower

Meteorological data set

........... a compilation of meteorological data representing conditions over some period of time and including such things as wind speed and wind direction, and formatted as required by the dispersion model being used. This analysis used a meteorological data set cove ring 5 years.

Micrometer/Micron

................ one millionth of a meter; typically used to distinguish particle size; typical human hair is 100 about microns in diameter

MLC

................................ ....... Mud Line Cellar, an excavation below the level of the sea floor to protect drilling equipment fro m moving ice floes.

MCL ROV System

................. A remotely operated submersible excavation unit proposed for establishing MLCs.

MLC ROV System Vessel

...... A support vessel used to operate and support the MLC ROV System.

Modeling domain

................... the area included in the dispersion

- modeling analysis

Modeling receptor

.................. a theoretical (i.e., often non

- specific) location used in computer modeling at which air pollutant concentrations are calculated. Modeling may also use site

- specific receptors representing individual

locations.

NAAQS

................................ .. National Ambient Air Quality Standard

NSPS

................................ ...... New Source Performance Standard; rules that pertain to air pollution emission sources subject to air quality permits and newly manufactured equipment

NO 2

................................ ......... nitrogen dioxide, a criteria air pollutant

NOx

................................ ........ oxide s of nitrogen, a general class of air pollutant without a specific air quality standard but used in monitoring air quality

Particulate matter (PM)

.......... air pollutant comprised of solid or liquid particles; PM is usually characterized based on the particle size. See also PM10 and PM2.5.

PM10

................................ ...... "Coarse" inhalable particulate matter with an aerodynamic size less than or equal to 10 micrometers ( microns )

PM2.5

................................ ..... "Fine" inhalable particulate matter with an aerodynamic size less than or equal to 2.5 micrometers ( microns )

Point source

............................ an emission source type defined in AERMOD. Point source emissions are released from a single location.

ppm

................................ ......... parts pe r million (a metric used in quantifying concentrations of air pollutants)

Receptor

................................ .. See modeling receptor.

Release height

......................... a CALPUFF term defining the height above ground at which source

emissions are released

SO 2

................................ .......... Sulfur dioxide, a criteria air pollutant

tpy

................................ ........... tons per year, an estimate of annual emissionsShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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– Attachment B Page 6 of 35 μg/m 3

................................ ..... micrograms per cubic meter (a metric used in quantifying concentrations of air pollutants)Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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## Preface

Shell Gulf of Mexico Inc. (Shell) has requested authorization from the United States Department of the Interior, Bureau of Ocean Energy Management (BOEM), to drill exploration wells in the Chukchi Sea beyond the 3

- mile seaward boundary of Alaska. E xploration drilling will consist of the o peration of two
drill ing units with support vessels on the Outer Continental Shelf (OCS) of the Chukchi Sea. Shell already has an approved Exploration Plan (EP) for drilling in the Chukchi Sea at the Burger Prospect (EP Revision 1) , but is making changes to that approved EP

.

This report was deve loped for Shell’s EP Revision 2 and its supporting Environmental Impact Assessment ( EIA ) , for exploration drilling operations for Shell’s future season s of operations. This Air Quality Technical Report presents the analytical methods and results of an analysis to estimate onshore air pollutant concentrations that may result from the drill ing units

, their support vessels , and onshore

sources of air emissions associated with the exploration program

.

BOEM implements its authority to protect air quality under 30 CFR Part 550 Subpart C. This program is referred to as the BOEM Air Quality Regulatory Program (AQRP). BOEM also has the responsibility to

evaluate potential impacts of the exploration drilling pro gram pursuant to the National Environmental Policy Act (NEPA). BOEM Alaska indicates that air quality modeling is required to evaluate potential impacts under NEPA

. 1 This report details the methods, data

, and predicted onshore concentration results

of the NEPA air quality analysis. A separate report, provided in Attachment C of the EIA of EP Revision

2 , details the methods, data, and predicted offshore concentration results of the NEPA air quality analysis.

1 Meeting between BOEM and Shell, May 15, 2013, held in BOEM office, Anchorage, AlaskaShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

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## 1 Summary

Th is air quality analysis of th e Shell OCS Exploration Program described in Shell’s EP Revision 2

identifi e s air pollutant emissions and onshore concentrations that may result from the air emissions from

the exploration program

.

The ai r quality assessment of the exploration drilling program
, as described in EP Revision 2

, include s development of detailed emission inventories based on spatially and temporally distributed emissions from the following emissions units :

Offshore Drilling Program

• T wo drilling units , including

o Main generators

o Propulsion e ngine s

o Small internal

- combustion engines

o Seldom

- used engines

o Heaters and boilers

o O n

- board incinerator s

• I ce

- management vessels (includes anchor handlers) , including

o Propulsion and generator engines

o Boilers

o Incinerators

• Oil spill response vessels

• Offshore supply vessels

• Support tugs

• Oil storage tanker

• S cience vessel s

• MLC ROV System v essel

Onshore Program

• Onshore support activities, including

o Aircraft emissions

o A housing facility including associated generator engines

o A n airport hangar and storage building

o Miscellaneous onshore vehicles

Emissions from these units and activities were evaluated with air quality dispersion modeling. The air quality analysis considered emissions and concentrations of "criteria" air pollutants

, including oxides of nitrogen, oxides of sulfur, particulate matter and carbon monoxide

.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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## 2 Project Description

2.1 Exploration Program Activity Area

Shell proposes to continue the exploration drilling program in the Chukchi Sea, Alaska, that began in the

2012 drilling season and is detailed in EP Revision 1. Shell ’ s proposed exploration drilling operations will take place on federal OCS leases in the vast Chukchi Sea, an area of approximately 230,000 square miles (mi 2 ). Shell ’ s EP Revision 2 proposes to condu ct exploration drilling activities on six lease blocks all located within what is known as the Burger Prospect, acquired in federal OCS Lease Sale 193. The drill sites are remote from any infrastructure or human habitation and are located more than 6 0 mil es offshore in Arctic waters that are inaccessible for eight months or more of the year due to pack ice. Shell’s seasonal exploration drilling operations would begin on or about July 1 st and extend no later than

October 31 st . The sites are identified as “ Burger” A, F, J, R, S and V in Table 1

. The general location is depicted in Figure 1

.



### Table 1

. Candidate Drilling Sites 1

Prospect Well Area Lease

Number Lease

Block Latitude Longitude UTM Coordinates 3

X(m) Y(m)
Burger A 2 Posey OCS

- Y

- 2280 6764 N71° 18' 30.92" W163° 12' 43.17" 563945 7912759 Burger F Posey OCS

- Y

- 2267 6714 N71° 20' 13.96" W163° 12' 21.75" 564063 7915957 Burger J Posey OCS

- Y

- 2321 6912 N71° 10' 24.03" W163° 28' 18.52" 555036 7897424 Burger R Posey OCS

- Y

- 2294 6812 N71° 16' 06.57" W163° 30' 39.44" 553366 7907999 Burger S Posey OCS

- Y

- 2278 6762 N71° 19' 25.79" W163° 28' 40.84" 554391 7914199 Burger V Posey OCS

- Y

- 2324 6915 N71° 10' 33.39" W163° 04' 21.23" 569401 7898125

1 Identified under Table 1.a

- 1 of Chukchi Sea EP Revision 2.

2 Burger A drill site where a partial well was begun in 2012.

3 The Universal Transverse Mercator (UTM) coordinate system quoted here is from BOEM’s OCS Official Protraction Diagram and are based on the North American Datum 1983 (NAD

- 83), zone 3. The actual coordinates shown are the expected drill locations within e ach block.

Shell proposes to support the offshore drilling program with an onshore support facility located in the

Barrow area. The fa cility is discussed in Section 6

.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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– Attachment B Page 10 of 35 

### Figure 1

. Project Vicinity MapShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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### 2.2 Offshore Drill ing Program Activities and Emissions Units

The offshore drilling program will be conducted by two drilling units, the M/V Noble Discoverer ( Discoverer ) and the Transocean Polar Pioneer ( Polar Pioneer ), with support from ice management vessels, anchor handlers, oil

- spill response (OSR) vessels, offshore supply vessels (OSVs), tugs, tankers, science vessels, MLC ROV System vessel, and aerial transport. For the drilling units, the Discoverer and

Polar Pioneer , the actual vessel to be used and the types of emission units on board are defined. Support vessels are contracted on a yearly basis and multiple vessels ar e able to meet the duty requirements for the

needed tasks. As such, it is not certain that the support vessels currently considered for the exploration program will be available . T herefore, for the support vessels, a candidate vessel and the anticipated

emission units are identified

.

The Discoverer is a turret

- moored drilling unit that underwent significant upgrades in 2007 and 2013 so that it could operate in the Arctic

. The Discoverer has its own propulsion engine for self

- transport. The

Discoverer is equipped with electrically powered thrusters, engine

- driven electrical generators for the drilling motors, and other self

- powered equipment such as hydraulic pumps, cranes, boilers, an incinerator, and other (mostly emergency

- related) small sources. T here will be no flares and no hydrocarbon

- venting sources except for minor amounts associated with the drill cuttings.

The Polar Pioneer is a semisubmersible vessel designed to operate in the arctic environment. The Polar

Pioneer is transported by a towin g vessel. The Polar Pioneer operates main generator engines, heaters

and an incinerator. There will be no flares and no hydrocarbon

- venting sources except for minor amounts associated with the drill cuttings.

The support vessels a re equipped with diesel

- f ueled primary and emergency power generation engines,

and in some cases incinerators and/or diesel

- fueled boilers

. Ice management vessels and a nchor handler s will assist with management of the drilling unit anchors, bow washing of any ice buildup on the drilling units

, and some ice floe fragmenting in support of the ice management vessel. One anchor handler and one ice management vessel provide primary close support

for each drilling unit with regard to these tasks

. The ice management vessel s are needed when there are ice features that require disruption in their path or fragmentation in order to provide protection for the

drill ing unit , or other assets critical to the safety of the exploration drilling program (i.e., mooring buoys, etc.)

. Up to two ice management vessels may be tasked to fragment any manageable ice flows so that the ice will flow around the drilling units. These ice management vessels may work at distances of 25 miles

or more upwind of the drilling unit to monitor the leading edge of any ice floe of possible concern . These activities are necessary for managing ice at distances that provide adequate response time for drilling units to get off a well and anchor in case of encroaching ice that cannot be manag ed. These response times may vary depending on the drilling stage of the well hole

. Furthermore, the anchor handlers and ice management vessels may have other tasks to conduct beyond 25 miles of the drilling units . This operation is accounted for in the fuel consumption limits used to calculate emissions , but ENVIRON has assumed they will be within 25 miles for the entire season. As discussed below, t his assumption is

conservative and tends to over

- predict onshore concentrations.

An oil

- spill response vessel or vessels will be anchored nearby

, typically between the two drilling units

. During season, these vessels will primarily be used during refueling operations to protect against possible spills and will be located near the refueling Arctic oil fuel storage tanker. The OSR vessels are expected to be used in the unplanned and unlikely event of an oil discharge to the water. These vessels will be

available to both the Discoverer and the Polar Pioneer

.

Other support vessels include those for resupply and material transfer to shore. The OSVs would travel to

the drilling units , then “ park ” in dynamic positioning (DP) mode beside the drilling unit for material orShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 12 of 35 personnel transfer. The OSVs may operate in DP mode beside the drilling unit and w ould remain there

for approximately one day.

It is anticipated that up to t wo science vessels similar to the OSV s will be primarily used to monitor discharges from each drilling unit as required by the National Pollutant Dis charge Elimination System (NPDES) General Permit . These vessels may remain within a few miles of each drilling unit for these sampling periods or conduct secondary tasks, as needed

. Two tugs will be operated in standby mode on

- location in case the Polar Pioneer must leave location quickly because of encroaching ice. Another tug will escort the Discoverer to the drill site

, assist during mooring , and depart during the season to conduct other activities outside the Chukchi Sea

.

A fuel and oil tanker is exp ected to be located in an area between the two drilling units to resupply the drilling units and support vessels

. During the 2012 drilling season, m ud l ine c ellars (MLC) were excavated with large drills aboard the

Discoverer . A s described in Shell's EP Revision 2, an MLC may also be excavated by a separate vessel (MLC ROV System Vessel) supporting a specially designed subsurface excavator. This MLC operation

may proceed ahead of the Discoverer and Polar Pioneer t o future well s ites within the same lease block s
identified in Table 1

. If the ice management vessels or OSVs travel beyond 25 miles from the drilling units , air emissions

would be disperse d to a greater extent than when the vessels are closer to the drilling units. Because the dispersion mo deling conducted in this analysis concentrates all ice management and OSV emissions within 25 miles of the drilling uni ts, it results in predictions that are higher than those expected if some vessels venture outside the 25 mile radius. Consequently, additional modeling of that scenario is not

warranted.



### 2.3 Onshore Exploration Program Activities and Emissions Units

As discus sed further in Section 6 , t here will be onshore support facilities, including housing for employees, hangars and other storage buildings, and transport of supplies and personnel. Onshore

emission units related to the project could include power generation for personnel camps, material storage, helicopter hangers, transport vans and truck s, and helicopters in Barrow

.



### 2.4 Spatial and Temporal Relationships of Offshore Drilling Program Emission Units

For air impact analysis purposes, there are three emission unit groups: the drilling units , the on

- location

support vessel support, and the onshore activities. Emissions units that are physically close together can have additive impacts, whereas, if the same emissions units are located over a large area, the impacts will be smaller at any one location (and distributed over a larger area).

The emission units on the Discoverer and Polar Pioneer are c oncentrated on each drilling unit . The support vessels will be spread over a 25 mile radius of the Discoverer and Polar Pioneer ; therefore,

emissions will be dis pers ed over this large area and wi ll not be concentrated. At large distances from the drilling units, of up to 50 miles , the collective emissions will be well dispersed.

The Discoverer and the Polar Pioneer will operate in separate lease blocks. Based on Table 1 , the distance between drill sites varies from 3 kilometers to 21 kilometers, depending on the two drill sites that are active at any given time. In order to evaluate the greatest potential o nshore impact from the exploration activities, it is assumed that the drilling units are operating at the two lease blocks closest to shore, which are blocks J and V. This assumption will result in an analysis of the greatest potential onshore impacts bec ause at distances larger than a few miles where there is no elevated terrain, air qualityShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 13 of 35 concentrations are inversely proportional to the distance between the emission unit and the receptor. In this instance, the two drilling units are approximately 14 k ilometers apart.

As discussed, the support vessels operate in different locations and operate in different ways over large

areas. The anchor handler and ice management vessels will operate in areas determined by the drilling

unit locations . When they are managing or scouting ice, they may typically be 25 miles or more upwind

of the drilling unit

. When these vessels are not working they could be anchored in warm

- stack mode, transitioning or working in support of activities inside or outsid e of the OCS program area

. The OSR vessels will normally be in an area between the Discoverer and the Polar Pioneer

. These

vessels will be in a stand

- by mode or supporting refueling operations associated with exploration

program.

Some e missions units ma y not operate concurrently. Only emissions units that operate concurrently can

have additive short

- term (1

- hour and 24

- hour) concentrations . Those that do not operate concurrently

will not have additive short

- term concentrations, although all will contri bute to concentrations averaged over the season. Drilling and use of the drilling units’ smaller internal combustion (IC) engines will take place only after the drilling unit is fully anchored and connected to its anchors. The Discoverer ’s propulsion engine will only be used intermittently once it is anchored. The cementing and logging equipment will only be used when setting casing or logging a well when the drilling unit is anchored at a

drill site . None of the small er diesels are operated during ship transit to and from the drill site. None of the smaller IC engines are used more than occasionally. However, since the precise times when individual emission units are expected to operate are not known at present, all units have been conservatively assumed to be operating concurrently in the air quality analysis.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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## 3 Affected Environment

3.1 Ambient Air Quality Standards and Attainment Status

Air quality is generally assessed in terms of whether concentrations of air pollutants are higher or lower than ambient air quality standards set to protect human health and welfare. Ambient air quality standards

are established for what are referred to as "criteria" pollutants (e.g., carbon monoxide

- CO, particulate matter, nitrogen dioxide

- NO 2 , and sulfur dioxide

- SO 2 ). Onshore i n Alaska , two agencies have jurisdiction over the ambient air quality accessible to the general public : the U.S. Environmental Protection Agency (EPA) and the Alaska Department of Environmental Conservatio n (ADEC) . These agencies establish regulations that govern the concentrations of pollutants in the ambient air. A pplicable

state and federal ambient air quality standards are displayed in Table 2 . These standards have been set at

levels that EPA and ADEC have determined will protect human health with a margin of safety, including

the health of sensitive individuals like asthmatics, the elderly, the chronically ill, and the very young. 2

T he ambient air quality standards are commonly used in NEPA assessments to evaluate onshore air quality impacts

.

Neither ADEC nor EPA maintain air quality monitoring stations on the North Slope of Alaska in the

vi cinity of the nearest onshore areas to the proposed exploration leases addressed here. In general, air quality monitoring stations are located where there may be air quality problems, and are usually in or near urban areas or close to specific large air p ollution sources. Based on monitoring information for criteria air pollutants collected over a period of years, ADEC and EPA designate regions as being "attainment" or "nonattainment" areas for particular pollutants. Attainment status is therefore a measur e of whether air quality in an area complies with the federal health

- based ambient air quality standards for criteria pollutants. T he North Slope of Alaska is classified as “attainment” or “unclassified” for all regulated air pollutants. In practical term s, “unclassified” areas are treated exactly the same as “attainment” areas. These designations are supported by monitoring data collected by private parties, such as Shell and BP.

2 U.S. EPA, 2008a: Risk and Exposure Assessment to Support the Review of the NO2 Primary National Ambient Air Quality Standard. EPA

- 452/R

- 08

- 008a, November 2008, Available at: http://www.epa.gov/ttn/naaqs/standards/nox/data/20081121_NO2_REA_final.pdf

U.S. EPA., 2008b: Integrated Science Asse ssment for Oxides of Nitrogen

-- Health Criteria.

EPA/600/R

- 08/071. July 2008. Available at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=194645

U.S. EPA, 2009: Risk and Exp osure Assessment to Support the Review of the SO2 Primary National Ambient Air Quality Standards: Final Report. EPA

- 452/R

- 09

- 007, July 2009, Available at: http://www.e pa.gov/ttn/naaqs/standards/so2/data/200908SO2REAFinalReport.pdf

U.S. EPA, 2010: Quantitative Health Risk Assessment for Particulate Matter. EPA

- 452/R

- 10

- 005, June 2010, Available at: http://www.epa.gov/ttn/naaqs/standards/pm/data/PM_RA_FINAL_June_2010.pdfShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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### Table 2

. Applicable Ambient Air Quality Standards for Criteria Pollutants

Pollutant Terms of Compliance (a) Concentration

Inhalable Particulate Matter ( PM 10 )

24

- Hour Average The 3 year average of the 98th percentile of the daily concentrations must not exceed 150 μg/m 3

Fine Particulate Matter ( PM 2.5 ) Annual Average

24

- Hour Average The 3

- year annual average of daily

concentrations must not exceed

The 3

- year average of the 98th percentile of daily concentrations must not exceed 1 2 μg/m 3 (b )

35 μg/m 3

Sulfur Dioxide (SO 2 ) (b)
Annual Average

24

- Hour Average

3

- Hour Average

1

- Hour Average Annual arithmetic mean of 1

- hour averages must

not exceed

24

- hour average must not exceed more than

once per year 3

- hour average must not exceed more than once

per year 1

- hour standard is attained when the three

- year average of the annual, 99th percentile, daily maximum, one

- hour concentration is less than or equal to 80 μg/m 3

365 μg/m 3
1,300 μg/m 3
196 μg/m 3

Carbon Monoxide (CO)

8

- Hour Average

1

- Hour Average The 8

- hour average must not exceed more than

once per year The 1

- hour average must not exceed more than

once per year 10,000 μg/m 3

40,000 μg/m 3

Ozone (O 3 )

8

- Hour Average The 3

- year average of the 4th highest daily

maximum 8

- hour average must not exceed 0.075 ppm (150 μg/m 3 )

Nitrogen Dioxide (NO 2 ) Annual Average

1

- Hour Average The annual mean of 1

- hour averages must not

exceed

3

- year avg. of 98th percentile of daily max

1

- hour averages must not exceed 0.053 ppm (188 μg/m 3 ) 0.1 ppm (100 μg/m 3 )

Lead (Pb) Rolling 3

- month Average Rolling 3

- month average not to exceed 0.15 μg/m 3

Note: μg/m 3 = micrograms per cubic meter; ppm = parts per million

(a) All limits are federal and state air quality standards except as noted. All indicated limits represent "primary" air quality standards intended to protect human health.

( b ) EPA issued a new 12 μg/m 3 annual sta ndard on 12/14/2012 that beca me effective on March 18, 2013; the previous annual

standard was 15 μg/m 3

. The ADEC has yet to adopt the new standard.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 16 of 35 

### 3.2 Existing Air Quality Conditions

There are no e xisting sources of air pollution near the Chukchi Sea lease area because it is more than 60 miles from land and there are no other oil exploration or development sources in the Chukchi Sea at this

time. In the absence of sources of emissions , the air quality in the project area is expected to be good. The points of land nearest the proposed drill sites are in the remote parts of the Arctic coast of Alaska, and are mostly uninhabited except for occasional subsistence hunting and fishing. The nearest native villages are at Wainwright and Point Lay, approximately 66 and 86 nautica l miles away, respectively.

Because t he drill site location will be far from the Alaska shoreline and away from s ignificant sources of pollution, existing air quality concentrations can be represented with a regional value. According to

EPA’s Guideline on Air Quality Models (Guideline) (40 CFR 51, Appendix W, Section 8.2.2c), a “regional site” may be used to determine background concentrations if there are no monitors located in the vicinity of the source . A “regional site” is one that is located away f rom the area of interest, but is impacted by similar natural and distant man

- made sources. The majority of the air quality data on the North Slope have been collected by various industrial developments associated with the oil and gas

resources of the area

.

Shell and ConocoPhillips Alaska began monitoring NO 2 , PM 2.5 , PM 10 , SO 2 , CO, and O 3 concentrations at Wainwright, Alaska in November 2008 and Point Lay, Alaska in June 2010

. Both monitoring station s are remotely located (minimal influence of industry and other human activities) and are representative “regional site s ” on the North Slope for estimating offshore pollutant concentrations in the Chukchi Sea

. However, bo th monitoring sites are located onshore and are located adjacent to villages and therefore may be exposed to high concentrations of pollutants from nearby combustion or unpaved road dust from

vehicles. C onsequently

, it is expected that the measured concentrations of pollutants at these stations are higher than the concentrations that actually occur offshore because the combustion and dust sources are not present on the open sea

. A map of the ambient monitoring stations on the North Slope is provided in Figure 2

.

Table 3 shows a summary of the background pollutant concentrations measured at the Wainwright and Point Lay monitoring station s during the drilling sea son (July 1

– Nov. 3) . Comparison of the measured

concentrations in Table 3 with the National Ambient Air Quality Standards indicates that existing

c oncentrations are all well below ambient air quality standards for all pollutants and all averaging times.



### Table 3

. Maximum Existing Ambient Air Concentrations a

Pollutant Averaging

Period How standard is applied Wainwright

Maximum

Measured

Concentration b
(μg/m 3 ) Pt. Lay

Maximum

Measured

Concentration c (μg/m 3 ) NAAQS (μg/m 3 )

NO 2 1

- hour 3

- year average of 98 th percentile daily maximum 1

- hour averages 40.1 43.8 188

Annual Maximum arithmetic average 1.4 1.4 100

PM 2.5 24

- hour 3

- year average of 98 th percentile daily averages 10.7 5.5 35

Annual 3

- year average of annual arithmetic

averages 2.9 2.0 12

PM 10 24

- hour Not to be exceeded more than once per year (2 nd highs), averaged over 3

years 73.0 23.6 150

SO 2 1

- hour 3

- year average of 99 th percentile daily maximum 1

- hour averages 8.1 11.6 190Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 17 of 35 3

- hour Not to be exceeded more than once per year (2 nd high) 12.8 14.1 1,300

24

- hour Not to be exceeded more than once per year (2 nd high) 2.2 13.4 365

Annual Maximum arithmetic average 0.4 4.8 80

CO 1

- hour Not to be exceeded more than once per year (2 nd high) 953 1490 40,000

8

- hour Not to be exceeded more than once per year (2 nd high) 946 1280 10,000

a Maximum background ambient air concentrations are calculated for the July 1 st

- Nov. 30 th “drill season” period, using the most recent available data from Wainwright and Pt. Lay monitoring stations.

b Maximum c oncentrations measured at W ainwright from 2009 through 2012, as calculated according to the method described in “how standard

is a pplied” column

c Maximum concentrations measured at Pt. Lay monitoring site from 2011 through 2013, as calculated according to the method desc ribed in “how standard is applied” column.



### Figure 2

. Regional Air Quality Monitoring Site LocationsShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 18 of 35 

### 3.3 Meteorological Conditions and Climate

Climate in the project study area i s unique to the polar region . The climate is dominated by severe cold temperatures during win t er and a brief period of warming in late summer and early fall.

From an air pollution perspective, the most important meteorological parameters are wind speed and direction because they determine the transport and dispersion of airborne contaminants. Wind conditions are commonly represented by a figure known as a wind rose. Figure 3 and Figure 4 depict wind rose s constructed from the meteorological data used in the offshore drilling program and onshore program air quality analys e s , respectively . The figure s ha ve a series of bars ema nating from the center of the drawing. The bars represent the relative frequency of wind directions with the length of each bar representing the relative frequency of the wind direction. Figure 3 and Figure 4 indicate the most frequent wind directions at the Burger Lease area and in Barrow are from the east

- northeast.

The colors in the figure illustrate the relative frequencies of wind speeds at the project site. The color code in the figure can be used to interpret the wind speeds.

Wind roses are indicative of dominant wind directions and thus also, the most frequent transport directions of air pollutants. Due to the higher transport frequencies, in many cases peak long

- term average concentrations can be found downwind in these directions, because they occur more often and when averaged over a longe r period of time can typically have higher average concentrations. This is not always the case, as other factors can contribute to the determination of peak downwind concentrations, such as the presence or absence of receptors in each downwind direction, terrain elevations in the downwind directions, wind speeds associated with each wind direction and air turbulence associated with each wind direction. Thus wind roses are useful when interpreting long

- term average concentrations, with the above qualifiers

. However, the wind rose gives little information on the peak short

- term (e.g., hourly or daily) concentrations . As Table 1 shows, air quality is regulated on a variety of averaging

times. Short

- term impacts can occur in any wind direction, regardless of how common or frequent the wind direction is. As a result, in many air quality studies the peak short

- term impacts are not at the same locations as the long

- term concentrations , and are not necessarily aligned with the most common wind

directions.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 19 of 35 

### Figure 3

. Wind Rose for Shell Burger Lease Area 2009

- 2010Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 20 of 35 

### Figure 4

. Wind Rose for Barrow, Alaska 2008

– 2012Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 21 of 35 

## 4 Offshore Exploration Program Analytical Methods

An air quality impact analysis includes two basic steps: (1) development of an emission inventory t hat

identifies short

- term and annual emissions related to the explorati on drilling program , and (2) dispersion modeling to estimate resulting air contaminant concentrations in the ambient air. Appendix K of EP Revision 2 provides detailed documentation of projected emissions, including the basis for all calculations, attribut able to the exploration activities described in EP Revision 2. Please refer to Appendix

K of EP Revision 2 for further details. The following sections discuss the methods employed and the critical assumptions involved in the dispersion modeling analysis , w hich are based on the information provided in Appendix K of EP Revision 2

. A separate air quality modeling study was conducted for the onshore program located in the Barrow area. As discussed in Section 6, there are emissions associated with the onshore program but they represent only a small fraction of the total emissions. The emissions and setting associated with onshore program facilities ( the Barrow personnel camp, the hangar and the helicopter usage) are very different from those associated with the offshore drilling program. Because the onshore fa cilities are located in Barrow, the

emission units are much closer to the general population and therefore it is not appropriate to use the same methods of analysis for both offshore drilling activities and onshore activities. A ccordingly, this section focuses mainly on the offshore drilling program emissions units (the Discoverer , the Polar Pio neer , and the support vessels), and the methods discussed in this section are those used in the evaluation of the

offshore sources. Chapter 6 addresses the on

- shore emissions units and modeling assessment.



### 4.1 Model Configuration of Emission Units

All of t he emission units associated with the exploration drilling program are to some extent mobile . The

most stationary of the units are those on the drilling units . During the drilling of any individual well, the drilling unit remains fixed over the well. However, the Discoverer rotates about the drilling stem, placing the bow of the ship in the direction of the oncoming wind, which is usually also the direction any moving

ice would come from. The Discoverer does not rotate a s a result of the wind acting on it, but rather is moved by a cranking system aboard the Discoverer . As the vessel is rotated, the locations of many or all

the emission units on the drilling unit are moved. The Polar Pioneer does not rotate with the wind

. Although the Discovere r emission units are mobile, for purposes of the modeling study, bo th drilling units are assumed to be point sources at a fixed location. Given that the nearest onshore receptors are
more than 100 kilometers from the Discoverer , th e effect of the actual rotation of the ship is insignificant

in the modeled concentrations. Hence the drilling unit is assumed to be pointing in the direction of the prevailing wind for the entire drill season. The prevailing wind direction was assumed t o be coming from 60 degrees measured clockwise from north based on buoy measurements taken at the Burger site during July to November 2009.

In contrast to the drilling unit s , the support vessel emissions units are much more mobile. Section 2.4

describes the various types of movement and operation from each type of support vessel.

Given the highly mobile nature of these support vessels it is inappropriate to model them as fixed point sources, but rather as area sources where emissions are distributed over an area. For the ice management vessels, the area source is modeled as a large triangular area approximately 25 miles long and located upwind of the drilling unit . For the other vessel s, a square area source, 2 kilometers on each side

, is assumed to repr esent the remaining emission units. It is recognized that ice management vessels may be located further from the drilling units when managing ice, but the dimensions and locations used for these vessels have been selected to conservatively represent the s patial extent of their emissions.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 22 of 35 Figure 5 is a schematic drawing that shows the location of these point and area sources. Note that the large triangular areas are intended to represent the ice management vessel emissions. The four smaller square areas shown in the figure are used to represent the support vessels. One of these square areas is used to represent the MLC ROV Sy stem and its associated MLC ROV System vessel. The two areas shown directly downwind of the Discoverer and Polar Pioneer represent the close support vessels including the science vessel and any tugs dedicated to the drilling unit. The central area source , located

between the two d r illing units is the common fleet, including the Oil Spill Recovery vessels and the oil supply tanker.



### Figure 5

. Orientation of Model Emissions Sources

4.2 Dispersion Modeling

ENVIRON International Corpo ration ( ENVIRON ) used air quality dispersion modeling simulations to

estimate ambient concentrations attributable to emission units associated with the exploration program

. This section discusses the methods used to develop these simulations.

Air quality m odels are computer programs designed to mathematically represent atmospheric transport and dispersion of airborne contaminants. The purpose of the proposed air quality modeling in this impact analysis is to provide estimates of ambient concentrations of air pollutants emitted by the various engines

boilers , and other emission units that are part of the exploratory drilling program described in EP

Revision 2

.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 23 of 35 4.2.1 Dispersion Model Selection

The two air quality models most commonly recommended in the Guideline for industrial sources of emissions are the AERMOD model and the CALPUFF model. The AERMOD model is recommended by EPA for computation of concentrations within 50 kilometers of a source, while the CALPUFF model is

recommended for locations farther than 5 0 kilometers from a source. Discussions with BOEM 3 indicated the agency’s intention to follow EPA’s Guideline on Air Quality Models. While the Guideline provides no specific guidance on modeling offshore vessels, the guidance does suggest that when source

- receptor distances are more than 50 kilometers, CALPUFF should be used.

ENVIRON applied CALPUFF to predict pollutant concentrations from emissions associated with Shell’s

offshore drilling program in the Chukchi Sea. The CALPUFF predictions were used to di splay potential regional pollutant concentrations, assess compliance with the NAAQS on shore, and to predict concentrations at selected towns and villages or other locations of interest. The remainder of this section describes the long

- range transport disp ersion modeling techniques.

4.2.2 Methods

ENVIRON applied the regulatory version of the CALPUFF modeling system to simulate emissions from

the offshore drilling program described in EP Revision 2 . CALPUFF (Version 5.8) is the EPA recommended dispersion model fo r long

- range transport analyses and source

- to

- receptor distances beyond 50 km. 4 For the application of CALPUFF, Shell followed the techniques recommended by the Federal Land Managers for Class I area assessments with a few modifications for Arctic conditi ons and available datasets. The simulations were performed based on a representative set of meteorological conditions from July to November 2007, 2008, and 2009 , so as to best reflect drilling season conditions

. EPA and ADEC practice is to accept meteorolo gical data sets less than 10 years old for use with air dispersion modeling. Shell considers this data set to be representative because meteorology does not change dramatically on short time scales. The methods used to prepare the meteorological fields a nd perform the dispersion model analysis are described below.

4.2.3 Domain

The area included in the dispersion

- modeling analysis (i.e., the CALPUFF mode ling domain ) is shown in Figure 6 . The Burger site, several villages, and a 4

- km receptor grid mesh size are posted on the domain plot. The 4 kilometer grid size for receptors was selected in order to give coverage to the entire domain while still giving adequate resolution to concentrations. The analysis assume s the Discoverer and Polar

Pioneer are located at the anticipated drill sites in Lease Block s V and J, respectively. The CALPUFF domain is a rectangular 167

- by

- 118 grid with a horizontal mesh size of 4 km and 10 vertical layers ranging geometrically from the surface to 4,000 m. A Polar Stereographic (PS) projection was used for the coordinate system with an origin at ( 70 N, 155 W) and standard latitude of 70 N. Receptors were also placed along the shoreline at a spacing of 1

- km, at the villages, and places of interest shown on Figure 6

, in keeping with BOEM recommendat ions at Shell’s meeting with BOEM on May 15, 2013.

3 Meeting between Shell and BOEM held on May 15, 2013 at BOEM’s offices in Anchorage Alaska.

4 40 CFR Part 51 Appendix W: Guideline on Air Quality ModelsShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 24 of 35 Note : Receptor locations indicated in blue.



### Figure 6

. Onshore Receptors Used in the CALPUFF Modeling

4.2.4 Mesoscale Model Interface Format and Weather Research Forecast

The CALPUFF model requires meteorological data inputs to predict on

- shore concentrations

. This is achieved through the use of a meteorological data set and a preprocessor that prepares the information in a format that CALPUFF can accept. ENVIRON used the Weather Research Forecast (WRF) model to construct the meteorological fields and the Mesos cale Model Interface Format tool (MMIF) 5 to process and reformat the WRF output for input to CALPUFF. EPA provided ENVIRON with WRF model

simulations for the Chukchi Sea, which were then processed with MMIF (Version 2.3)

. These WRF simulations for July t o November of 2007 to 2009 supported previous ConocoPhillips permitting

activities in the Chukchi Sea. 6 The WRF simulations have the three domains with grid mesh sizes of

5 Brashers, B., and C. Emery, 2013. Draft User’s Manual: The Mesoscale Model Interface Program (MMIF), Version 2.3, 2013

-

4

- 30. Prepared by Environ International Corp. for U.S. EPA, OAQPS, Air Quality Assessment Division, Air Quality Modeling Group, Mail Code C439

- 01, Research Triangle Park, NC, 27771, Accessed at http://www.epa.gov/ttn/scram/dispersion_related.htm#mmif

.
6 McNally, D. and Wilkinson, J.G., 2011. Model Application and Evaluation

– ConocoPhillips Chukchi Sea WRF Modeling

Application, Prepared by Alpine Geophysics, 7341 Poppy Way, Arvada, CO, 8007, November 21, 2011.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 25 of 35 36/12/4

- km and 37 vertical levels. The boundary layer, nudging and other options sel ected for the WRF simulations are based on comparisons to Arctic meteorological data and the results of ongoing studies sponsored by BOEM. 7

The WRF meteorological dataset for the Chukchi Sea has been evaluated against surface and upper air

observations wi thin the model 4

- km domain including analyses focused on the coastal stations as a group, and at Wainwright and Barrow individually. The WRF simulations replicated observed temperatures, mixing ratios, wind speeds, wind directions, and precipitation totals within well

- established model performance benchmarks. 6 WRF also predicted the observed atmospheric structure aloft when compared to the observations at Barrow. The developers of dataset found the overall WRF model performance was better than previous datasets they evaluated for the intermountain west, Gulf Co ast or eastern seaboard of

the United States. 6

ENVIRON used the following MMIF options, which are typical of most uses and follow model

- guidance, to process and reformat the WRF meteorological fields for CALPUFF:

• Use only the 4

- km WRF inner domain ;

• Select the GOLDER option for calculation of the Pasquill

- Gifford stability class ;

• Use layer mapping of the 37 vertical WRF levels to 10 layers with tops of 20, 40, 160, 320, 640, 1200, 2000, 3000, and 4000m ;

• No recalculation of the mixing height, the WRF diagnostic output will be used directly ; and

• Trim five cells along from the outer edge of the WRF 4

- km mesh size domain to account for potential edge eff ects in the WRF simulations

. ENVIRON used MMIF to prepare daily input files for CALPUFF to account for changing sea

- ice coverage in the Arctic Ocean. The corresponding changes to the hourly energy fluxes and other important variables predicted by WRF governing dispersion and transport are already incorporated directly into the MMIF data provided to CALPUFF. However

, several algorithms in CALPUFF (e.g. deposition velocity calculations) need to distinguish between over water and over land characteristic s based on land use that is only provided at the start of each meteorological input file. Surface roughness changes from hour to hour over the water and seasonally over the land. Daily input files allow CALPUFF

to consider more refined changes to land us e for these algorithms. It should be noted that the surface roughness is calculated independently by WRF based on a two dimensional representation of the surface and is different for every grid cell in the surface domain.

4.2.5 Secondary Aerosols

CALPUFF incorporates algorithms to consider secondary aerosols formed by interaction and chemical

transformations of emitted NO X and SO 2 . Total PM 10 and PM 2.5 were calculated from the sum of the emitted primary species, ammonium nitrate, and ammonium sulfate. Th e primary PM 10 emissions for each source were divided into six species, including: soot or elemental carbon (EC), fine soil particles (PMF), coarse particles (PMC), organic carbon (OC), sulfate (SO 4 ), and nitrate (NO 3 ). PMC fractions

were calculated from the difference between PM 10 and PM 2.5 emission rates. PM 2.5 emissions were categorized into the remaining five species using the source profiles for diesel engines and incinerators

7 Zhang, J., Liu, F., Krieger, J., Tao, W, and X. Zhang, 1981. Project Report for the 5

- year Experimental Mesoscale Meteorology

Reanalysis for the Beaufort/Chukchi Seas for Beaufort and Chukchi Mesoscale Meteorology Model Study. Prepared for US DOI, Bureau of Ocean Energy managements, Alaska Outer Continental Shelf Region, Anchorage Alaska, Contract

0106CT397 87, November 2011.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 26 of 35 based on profiles recommended by the EPA for the Community Multi

- Scale Air Quality (CMAQ)

model. 8

Reaction rates and aerosol formation in the CALPUFF chemistry algorithms are influenced by background ozone and ammonia concentrations. ENVIRON used the maximum hourly ozone observations from the NOAA Barrow Observatory and BP’s Pad A monitoring site to represent background ozone concentrations in the simulations. The background ammonia concentration was assumed to be 0.5 ppb for all hours based on the Alaska Regional Haze Best Available Retrofit Technology (BART) modeling simula tions. 9

ENVIRON used the above quantitative methods to assess the contribution of emitted SO 2 and NOx emissions to form secondary aerosols and assess PM 2.5 concentrations. Although OCS activities in the

arctic are not under EPA’s jurisdiction, EPA Guidance for PM 2.5 Permit Modeling recommends an assessment of secondary aerosols when PM 2.5 precursor emissions (NOx and/or SO 2 ) emissions are greater than 40 tons per year

. 10 EPA

- recommended procedures include both quantitative and qualitative analyses. EPA’s Guidance provides a qualitative example based on a Region 10 Office assessment of

Shell’s Discoverer drill ship and support fleet in the Chukchi Sea. EPA’s qualitative assessment:

“examined the regional background PM 2.5 monitoring data and aspects of secondary PM 2.5 formation from existing sources; the relative ratio of the combined modeled primary PM 2.5 impacts and background PM 2.5 concentrations to the level of the NAAQS; the spatial and temporal correlation of the primary and secondary PM 2.5 impact s; meteorological characteristics of the region during periods of precursor pollutant emissions; the level of conservatism associated with the modeling of the primary PM 2.5 component and other elements of conservatism built into the overall NAAQS complianc e demonstration; aspects of the precursor pollutant emissions in the context of limitations of other chemical species necessary for the photochemical reactions to form secondary PM 2.5 ; and an additional level of NAAQS protection through a post

- construction monitoring requirement.”

Region 10 found the formation of secondary aerosols would be limited in the Arctic and the NAAQS would be protected accounting for both the primary PM 2.5 impacts and potential contributions due the

PM 2.5 precursors from the Discoverer and Associated Fleets. 10 These same qualitative arguments apply to the exploration activities examined in this study.

4.2.6 Downwash

The ten dency for exhaust plume rise to be reduced by wind flowing across nearby structures is referred to

as downwash. Because the nearest receptors are located more than 100 km from the source at the shoreline, building downwash effects will not significantly a ffect the modeled results. However, previous modeling analyses for the Shell exploration program have developed building downwash parameters. The modeling did use the previous downwash values developed for the Shell exploration program in the

8 CMAQ is the preferred regulatory model for PM 2.5 and regional haze simulations. The EPA website containing PM speciation

by source categories is: http://www.epa.gov/ttn/chief/emch/speciation/

.
9 The Alaska BART and Regional Haze programs are described at http://www.dec.state.ak.us/air/anpms/rh/rhhome.htm . In the

original BART simulat ions a background of 0.1 ppb was assumed. In the more refined simulations performed by applicants seeking exemption from BART, a more conservative 0.5 ppb ammonia concentrations was assumed.

10 EPA, 2014. Guidance for PM 2.5 Permit Modeling. U.S. EPA, Office o f Air Quality Planning and Stan dards, Air Quality

Assessme nt Division, Research Triangle P ark, NC , EPA

- 454/B

- 14

- 001, May 2014.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 27 of 35 CALPUFF mod eling analysis for the Discoverer sources. New downwash parameters were created for

the Polar Pioneer sources using EPA’s Building Profile Input Program (BPIP).

4.2.7 CALPUFF

ENVIRON performed six CALPUFF simulations using short

- term and annual emissions for each July to November period of 2007 to 2009. Short

- term and annual emissions are used in the analysis to address the different averaging periods of the NAAQS for each pol lutant. The respective short

- term and annual

emission rates for emission units included in the simulations are presented in the emission inve ntory in Chapter 2.4 of Appendix K of EP Revision 2

. It should be noted that d rilling may occur between July 1

and November 30 (153 days) , but each drillin g season is limited to 120 days

. As the critical impacts are short term ambient standards and increments, not annual averages, Shell wanted to address concerns that drilling could occur at any time during the five month window. Therefore, in order to make certain the peak meteoro logical scenarios were evaluated

, s hort

- term emissions were conservatively modeled to

occur during all 3,672 hours in the July 1 to November 30 drilling season for each of the three years in the

simulations

. It should be noted that CALPUFF addresses all pollutants in a combined single run. The interactions between pollutants, such as the secondary aerosol formation of particulate matter from gaseous oxides of nitrogen or sulfur are treated as chemical transfo rmations in the model . These non

- linear processes are modeled dynamically by CALPUFF for each hour and no aggregate or averaging method s are used.

The second ary aerosol is most commonly sulfates and nitrates, formed from sulfur dioxide and nitrogen

oxides

. To address secondary aerosol formation, ENVIRON applied POSTUTIL a program developed by the EPA, that converts particulate species such as sulfate and nitrate into the most common solid forms of these species, ammonium sulfate and ammonium nitrate, by c onverting mass to account for the difference in molecular weight between sulfate and ammonium sulfate, and nitrate and ammonium nitrate. It then sums all the particulate species to give total concentrations of PM 10 and PM 2.5

. U.S. EPA regulatory default dispersion options used for long

- range transport modeling were selected by invoking the MREG=1 switch within the input files. The CALPUFF utilities POSTUTIL and CALPOST were used to manipulate the large CALPUFF output files and summarize the results for comparison with the NAAQS.

CALPOST (Version 6.221) was used to calculate the annual average and maximum concentrations for each averaging period and pollutant. Consistent with statistical format of the PM 2.5 ambient standard, t he

8 th highest daily PM 2.5 concentration for each year of the simulations was calculated with CALPOST. For comparisons to the recent 1

- hour NAAQS for SO 2 and NO 2 , ENVIRON converted hourly time

- series from CALPOST to files that mimic the output files from AERMOD. ENVIRON then applied a program

to calculate the 8 th highest daily 1

- hour concentration and 4 th highest daily 1

- hour concentration, for NO 2 and SO 2 , respectively , to match the statistical format of these ambient standards

. ENVIRON conservatively a ssumed all NO X predicted at downwind receptor s is NO 2 for comparisons to the NAAQS. A second tier approach assuming a conversion factor of 0.8 is also appropriate and could be applied in any future analyses. It should be noted, although not performed her e, a Tier 3 approach can be used to limit the potential formation of NO 2 by the amount of ozone available. The Ozone Limiting Method (OLM) could be applied by post

- processing the CALPUFF output files and assuming a constant

NO 2 /NO X in

- stack ratio, an equi librium ratio of 0.8. The amount of NO 2 formed will be limited using the same hourly ozone input file used in the CALPUFF simulations.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 28 of 35 

## 5 Drilling Program Modeling Results

A s depicted in Figure 6

, 5,034 receptors were selected to evaluate onshore a ir quality

. Maximum predicted concentrations from all 5,034 receptors are presented in Table 4 for each pollutant and averaging time

.


### Table 4

. Maximum Predicted Concentrations Attributable to Offshore Sources (μg/m3)

Pollutant Averaging

Time Modeled

Concentration 1 Background

Concentration 2 Total

Concentration

NO 2 1

- hour 36 44 80

Annual 0.0 3 1.4 1

PM 10 24

- hour 4 24 28

Annual 0.0 2 NA 0.0 2

PM 2.5 24

- hour 4 5.5 10

Annual 0.0 2 2.0 2

CO 1

- hour 12 1490 1502

8

- hour 8 1280 1288

SO 2 1

- hour 0.1 11.6 12

3

- hour 0.1 14.1 14

24

- hour 0.03 13.4 13

Annual 0.0002 4.8 5

1 Averaged over a 20 square kilometer area

2 See Table 3.1.3

- 1 of the EIA in EP Revision 2

. Point Lay selected as a representative site for background values for all categories except 1

- hour and 3

- hour SO 2 (Wainwright selected for these categories).

The most representative maximum background air quality values availa ble were selected for this evaluation. As depicted in Figure 7, m aximum onshore concentrations determined by CALPUFF occur on the shoreline between Wainwright and Point Lay. The background concentrations from the nearest monitoring station to the modeled m aximum concentration for each pollutant and averaging period were selected to estimate total concentrations reported in Table 4.1.1

- 1. Point Lay was the nearest monitoring station for all pollutants and averaging times except for peak 3

- hour and 1

- hour SO 2 concentrations (Wainwright background values selected for these two categories). Although PM modeled peaks are nearer to Point Lay, Wainwright PM backgrounds were not considered representative because of contamination from road dust from the adjacent unp aved road discussed in SLR (2011) and SLR (2012).Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 29 of 35 

### Figure 7

. Locations of Maximum Onshore ConcentrationsShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

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Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 30 of 35 

## 6 Onshore Activity

The air quality issues for the onshore program facilities (the Barrow personnel camp, the hangar and the helicopter and aircraft usage) are very different from those associated with the offshore drilling program. The onshore program includes on

- going operation of equipment associated with onshore program

facilities. Additionally, as the onshore facilities are located in Barrow, the scale of potential air issues is

much more local than for the drilling locations and the use of CALPUFF is not common for close distances. As discussed previously, the AERMOD model is recommended by EPA for computation of concentrations within 50 kilometers of a source, while the CALPUFF model is recommended for

locations farther than 50 kilometers from a source.



### 6.1 Onshore Facilities Analytical Methods

Shell proposes to support the offshore drilling program with an onshore support facility located in the Barrow area. The exact details of the facility are uncertain at this time, but some elements are known. From an air emissions and modeling perspective, the facilities include:

• A sup port personnel camp, housing 75 persons in Barrow ;

• A kitchen, dining and recreation facility adjacent to the 75

- person camp in Barrow ;

• A hangar and warehouse at the Barrow airport with a boiler for heating ; and

• Helicopter and fixed

- wing aircraft operations at the Barrow airport for transport of personnel and some equipment to vessels at the Burger Prospect and for marine mammal surveys, and ice

surveys

. Air Sciences, Inc. developed an estimated inventory of air quality emissions for the proposed o nshore operations assuming maximum levels of activity and equipment. Details of these calculations can be found in Attachment B to Appendix K of EP Revision 2

.



### 6.1.1 Dispersion Modeling

The air quality modeling for the onshore facilities was separate d from the modeling of the offshore drilling program for two reasons:

• The distance between the drill sites and the onshore facilities is over 135 statute miles, so no significant overlap in the impact areas of the two operations is expected.

• The areas of potential im pact for the onshore facilities are very close to those facilities, on the order of a mile or less, while the point of land nearest the drill sites is more than 60 miles away.

As a result of these two factors, the air quality modeling for the onshore facil ities was performed separately, using a more appropriate air quality model, meteorological data, and receptors.

The onshore facilities were modeled with the EPA’s AERMOD model. AERMOD is recommended by EPA and other regulatory agencies as the appropriate model when the distance between the emission sources and the receptor is less than 50 kilometers. 11 Because the proposed onshore facilities are located

near the Barrow airport , meteorological data from the Barrow Airport were the most appropriate for use in the modeling analysis. A five year data set covering the period from 2008 through 2012 was obtained

11 40 CFR Part 51 Appendix W: Guideline on Air Quality ModelsShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 31 of 35 for the Barrow Airport and processed through the AERMET meteorological p re

- processor in preparation for running AERMOD. The Barrow a irport collects both surface data and upper air data, and both data

sets were used. Figure 4 is a wind rose depicting the Barrow airport data.

Because some of the activities take place at the Barrow airport, while others take place at the 75

- person camp site to the north and east of Barrow, the modeling domain covered the entire Barrow area wit h the exception of two areas, one at the 75

- person camp and one detailing the restricted area of the Barrow airport, that were eliminated from the grid because they are not considered ambient air due to restriction of access by the general public . A total 5, 690 receptors were placed on a 100 meter

- spaced grid covering the modeling domain. An additional 582 receptors were placed along the ambient air boundaries at a spacing of 10 meters. Figure 8 depicts the location of the receptors used in the onshore facility modeling analysis.

Emission unit s were modeled using a combination of point and area sources. The emissions from the

camp a rea were modeled as three point sources reflecting the three generators that would be present at full

build

- out for the camp. A separate point source was used for the hangar /storage building, which could have a boiler for space heat. Finally, two area so urce s w ere used for the helicopter emissions and fixed

wing aircraft emissions

. The Emission and Dispersion Modeling syste m (EDMS) is a computer program commonly used for airports where aviation emissions are of interest. The EDMS has the capability to both calculate emissions and perform dispersion calculations of ambient concentrations. The EDMS model was used here only to calculate the emissions from the helicopter activity . EDMS also has the ability to implement the AERMOD model, entering runway and taxiway emissions as a series of area sources at different heights. Given the low level of emissions and simplicity of the Barrow Airport setting, AERMOD was applied directly with the emissions entered in two single area source s
, one 702 meters long and 4 3 meters wide located at the center of the runway for the fixed

- wing aircraft and a separate area source 119 meters long by 78 meters wide to represent the helicopter emissions near the hangers. EDMS was only used for

calculation of emission rates

.



### 6.1.2 Ons hore Program Modeling Results

The maximum predicted concentrations fall well below the NAAQS , as shown in Table 5

.


### Table 5

. Maximum Predicted Concentrations Attributable to Onshore Facilities (μg/m 3 

### )

Pollutant Averaging

Time Modeled

Concentration Background

Concentration 1 Total

Concentration NAAQS

NO 2 1

- hour 94 40.1 13 4 188

Annual 1 1.4 2.48 100

SO 2 1

- hour 19 8.1 27 196

3

- hour 30 12.8 43 1300

24

- hour 8 2.2 10 365

Annual 0.01 0.4 0.4 80

PM 10 24

- hour 6 23.6 30 150

Annual 0.03 NA NA NA

PM 2.5 24

- hour 6 5.5 11 35

Annual 0.03 2.0 2 12

CO 1

- hour 1,198 953 2151 40,000

8

- hour 326 946 1272 10,000

1 Wainwright selected as a representative site for background values for all categories except PM (Point Lay selected for PM)

. Wainwright particulate matter backgrounds were not considered representative because of contamination

from road dust from the adjacent unpaved road discussed in SLR (2011) and SLR (2012).Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 32 of 35 Note : Receptor locations indicated in blue . Sources of emissions indicated in green

.



### F igure 8

. Receptors Used In Onshore Facility Modeling AnalysisShell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 33 of 35 

## 7 Cumulative Exploration Program Concentrations

Although no significant overlap is expected between concentrations of air pollutants resulting from the

off

- shore drilling emission sources and those from the on

- shore sources due to the large separation distance, a brief examination of potential cumulative concentrations is provided. This analysis is provided as a conservative over

- statement of potential peak concentrations because it assumes meteorological conditions would occur simultaneously that produced the peak concentrations from the

off

- shore drilling program and the on

- shore emission units , which does not occur in the meteorological data set. The current analysis is provided only because overlapping impacts, even computed by these unrealistic assumptions, are still below criteria, and thus provides a screening analysis, and eliminates the need for a more comprehensive analysis of cumulative impacts.

Concentrations at receptors in Barrow computed by the CALPUFF model for the drilling units and support vessels emission units were examined to determine the potential for overlapping concentrations. These would generally not be additive with the onshore facility concentrations for the short

- term averaging times (1

- hour, 3

- hour, 8

- hour an d 24

- hour), because the meteorological conditions that produce peak concentrations from the off

- shore emissions units are not the same as the conditions that produced peak concentrations from off

- shore emission units. Highest concentrations from the off

- shore sources in

Barrow for 1

- hour NO X were predicted to be 8 μg/m 3 . Highest 1

- hour CO concentrations are at most 3 μg/m 3 from off

- shore sources. All other pollutants and averaging times show off

- shore source impacts in

Barrow of less than 2 μg/m 3

. Adding these concentrations to those predicted for the on

- shore sources would not result in totals that exceed the NAAQS. Table 6 includes a summary of the impacts modeled onshore from sources of

emissions offshore and onshore. The total concentration s do not necessarily indicate that dispersion

model ing for a particular receptor location provided results that were additive. As stated, overlap of

short

- term concentrations is not expected to occur due to the large separation distances and prevailing meteorological conditions.



### Table 6 Summary of Cumulative Modeled Emissions Onshore (μg/m 3 )

Pollutant Averaging

Time Modeled

Concentration

from Offshore

Sources Modeled

Concentration

from Onshore

Sources Background

Concentration Total

Concentration 1 NAAQS

NO 2 1

- hour 8 94 40.1 142 188

Annual 0. 008 1 1.4 2 100

SO 2 1

- hour 0. 03 19 8.1 27 196

3

- hour 0.02 30 12.8 43 1300

24

- hour 0. 006 8 2.2 10 365

Annual 0.000 04 0.01 0.4 0.4 80

PM 10 24

- hour 1. 40 6 23.6 31 150

Annual 0.00 8 0.03 NA NA NA

PM 2.5 24

- hour 1. 40 6 5.5 13 35

Annual 0. 00 8 0.03 2.0 2 12

CO 1

- hour 3. 3 1,198 953 2154 40,000

8

- hour 1. 9 326 946 1274 10,000

1 Offshore concentrations are not expected to be additive with the onshore facility concentrations for the short

- term averaging times (1

- hour,3

- hour, 8

- hour and 24

- hour), because the meteorological conditions that produce peak concentrations from the off

- shore emissi ons units are not

likely to be the same as the conditions that produced peak concentrations from off

- shore emission units.Shell Chukchi Sea Exploration Plan Revision 2 Air Quality Technical Report

– Onshore Areas March 2015

Shell Chukchi Sea Exploration Plan Revision 2 March 2015 Environmental Impact Assessment

– Attachment B Page 34 of 35 

## 8 References

US Environmental Protection Agency (EPA)

2004. AERMOD User's Guide . EPA

- 454/B

- 03

- 001. September 2004

CALPUFF User’s Guide