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St. John, Virgin Islands 

2002 Regional Haze Base Year Modeling Inventory SIP 

Technical Support Documentation

June 19, 2012
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I. PREFACE

This document is to support EPA's approval of a revision to the Virgin Islands’ State 

Implementation Plan (SIP) which pertains to the following: 

Where applicable, 2002 modeling base year inventory annual emissions for PM2.5, NOx and SO2 

for St. John, Virgin Island (VI) area. Among the topics discussed below are the recent history

and criteria for approval and EPA’s final recommendations.

II. BACKGROUND 

On November 18, 2002, EPA designated the 2002 base year inventory as the inventory for SIP 

planning process to address the pollutants for the eight hour-ozone, PM2.5 and CO national 

ambient air quality standard. Identifying the base year gives certainty to States, and the selection 

of 2002 harmonized the date for EPA’s Consolidated Emissions Reporting rule (See 67 FR 

39602) dated June 10, 2002.) that requires submission of the ozone, PM2.5 and CO emission 

inventories every three years; 2002 is one of the required years for such updates. These 

requirements allow the EPA, based on the state’s progress in reducing emissions, to periodically

reassess its policies and air quality standards and revise them as necessary. Most important, the 

2002 ozone, new PM2.5 and CO inventories will be used to develop and assess new control 

strategies that the states will need to submit in their attainment demonstration SIPs for the new 

national ambient air quality standards for ozone, PM2.5 and CO. The base year inventory may

also serve as part of statewide inventories for purposes of regional modeling in transport areas. 

The base year inventory plays an important role in modeling demonstrations for areas classified 

as nonattainment and outside transport regions. For the reasons stated above, ideally EPA would 

therefore emphasize the importance and benefits of developing a comprehensive, current, and 

accurate 2002 ozone and PM2.5 emission inventories.

III. CRITERIA FOR APPROVAL

There are general and specific components of an acceptable emissions inventory. In general, the 

State must submit a revision to its SIP and the emission inventory must meet the minimum 

requirements for reporting by source category. Specifically, the source requirements are detailed 

below.

The Level I and II review process is used to determine that all components of the base year 

inventory are present. The review also evaluates the level of supporting documentation provided 

by the State and assesses whether the emissions were developed according to current EPA or 

acceptable alternative guidance. The data quality is also evaluated. 

The Level III review process is outlined here and consists of 9 points that the inventory must 
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adequately address. For a base year emission inventory to be acceptable it must pass all of the 

following acceptance criteria: 

Adequate documentation must be provided that enabled the reviewer to determine the emission 

estimation procedures and the data sources used to develop the inventory.

1. Evidence that the inventory was quality assured by the state and its implementation 

documented.

2. The point source inventory must be complete.

3. Point source emissions must have been prepared or calculated according to the 

current EPA guidance.

4. The area source inventory must be complete.

5. The area source emissions must have been prepared or calculated according to the 

current EPA guidance.

6. Non-road mobile emissions were prepared according to current EPA guidance for 

all of the source categories.

8. The method (e.g., HPMS or a network transportation planning model) used to 

develop VMT estimates must follow EPA guidance. The VMT development methods were 

adequately described and documented in the inventory report.

9. The MOBILE model must be correctly used to produce emission factors for each of 

the vehicle classes.

IV. DETAILED ACTION AND EVALUATION

Drafts and final versions of the Emissions Inventory were provided to Region 2 for the following 

documents and program area elements:

Where applicable, 2002 base year inventory annual PM2.5, NOx and SO2 emissions for the area. 

See Tables 1-3 below. This TSD contains a detailed discussion and summary of the review 

conducted by EPA for, where applicable, the 2002 base year inventory annual emissions for 

PM2.5, NOx and SO2 the area.

A. Details on How the Virgin Islands Satisfies Criteria 1 for the Quality Assurance 

Plan
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Quality Assurance Plan Implementation

The Quality Assurance (QA) plan was implemented for all portions of the inventory. The QA 

plan included a QA/Quality control (QC) program for assessing data completeness and standard 

range checking. Critical data elements relative to the inventory sources were assessed for 

completeness. QA checks were performed relative to data collection and analysis, and double 

counting of emissions from point, area and mobile sources. QA/QC checks were conducted to 

ensure accuracy of units, unit conversions, transposition of figures, and calculations. 

The reader is referred to Chapter II of Development of the 2002 Regional Haze Area, Point, 

Nonroad Mobile and Onroad Mobile Source Emission Inventories for St. John, Virgin Islands, 

dated June 2010. The QA plan for the inventory was performed in accordance with EPA 

Guidance.1,2,3

B. Details on How the Virgin Islands Satisfies Criteria 2 and 3 for the Point Source 

Inventory

Point Source Inventory

St. John, VI inventory includes point sources PM2.5, NOx and SO2 emissions for the area.. The 

inventory report describes how point source activity levels and their associated parameters are

developed, and how the data are used to calculate emission estimates. The report references

document for activity level and emission factors used and provides sample actual activity data 

and emissions factors. Information on how control efficiencies are applied and the associated 

sample calculations with numerical values are provided. Where applicable, annual PM2.5, NOx 

and SO2 point source emissions are presented for the area. Plant summary information on 

detailed plant levels is included in the inventory. The reader is referred to Chapter III of

Development of the 2002 Regional Haze Area, Point, Nonroad Mobile and Onroad Mobile 

Source Emission Inventories for St. John, Virgin Islands, dated June 2010. Thus, the point 

inventory was developed in accordance with section 5.3 of EPA Guidance.1,2,3

C. Details on How The Virgin Islands Satisfies Criteria 4 and 5 for the Area Source 

Inventory

Area Source Inventory

The inventory lists the source categories that are included in the area source inventory. Area 

source emissions are presented on a source category, county basis. Where applicable, annual 

emissions are provided for PM2.5, SO2 and NOx for the area. Inventory documentation includes

emissions factors, activity levels and sample calculations. Referenced information for the input 

values to equations is included. Point source contributions have been correctly factored out of 

the area source category totals where appropriate. Control efficiency and rule penetration are
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correctly applied for source categories. The reader is referred to Chapter IV of Development of 

the 2002 Regional Haze Area, Point, Nonroad Mobile and Onroad Mobile Source Emission 

Inventories for St. John, Virgin Islands, dated June 2010. Thus, the area source inventory was 

developed in accordance with EPA Guidance.1,2,3

D. Details on How The Virgin Islands Satisfies Criteria 6 for Non Road Mobile Source 

Inventory

Commercial Marine Vessel Emissions

Commercial marine vessel (CMV) emissions for PM2.5, NOx, and SO2 and NH3 are prepared by 

EPA contractor. The inventory report relied on actual operational data and then used local 

activity parameters. From this information, emission estimates are prepared based on estimated 

activity by mode, engine power by vessel, time in mode..etc. Where applicable, annual 

emissions are provided for PM2.5, NOx, and SO2 for total combined nonroad mobile sources for 

the areas. CMV source emissions are presented on a source category basis.

The reader is referred to Chapter V of Development of the 2002 Regional Haze Area, Point, 

Nonroad Mobile and Onroad Mobile Source Emission Inventories for St. John, Virgin Islands, 

dated June 2010. CMV source emissions was developed in accordance with EPA Guidance.1, 

2, 3

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E. Details on How The Virgin Islands Satisfies Criteria 8 and 9 for the Onroad Source 

Inventory

Onroad Mobile Source Inventory

The Virgin Islands’ mobile source inventory was developed by using 2002 annual vehicle miles 

traveled (VMT) inventory from a surrogate area of Kauai, Hawaii by using VMT data from 

Kauai and population data from Kauai and St. Johns, VI to develop VMT estimates by county, 

geographic component (urban, small urban and rural) and functional classes. 

Mobile 6 model for PM2.5, NOx and SO2 was used to generate emission factors for onroad 

vehicle emission estimates. The report also explains how Mobile 6 emission factors are used, in 

conjunction with VMT data, to estimate mobile source emissions for the inventoried areas. It 

provides the sources for the key inputs into the Mobile model. Key assumptions are also 

included. The methods used to determine on-road emission estimates are explained in the EPA’s 

Documentation for the Onroad NEI for Base Years 1970-2002, dated January 2004. Where 

applicable, annual emissions are provided for PM2.5, NOx and SO2 the area. The breakdown of 

annual emissions by highway vehicle classifications is included in the inventory. The inventory 

was developed in accordance with EPA Guidance.1,2, 3
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2018 Emissions Inventory

Unfortunately, not enough is known about possible growth on St. John to use growth factors.

Growth of population and sources may be restricted, as a result of the small size of the island and 

the large amount of land included in the National Park. There is not enough information 

available for the motor vehicle fleet on St. John, and projections based on vehicle turnover may

be very different from reality in an isolated location such as St. John and no interstate highways 

to bring outside traffic through. Therefore, no growth factors were applied to the area, nonroad 

mobile and onroad mobile source inventories from base year 2002 to 2018. See 2018 Modeling 

inventory below in Tables 1-3.
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Table 1: Sulfur Oxides Emissions from Point, Area and Mobile Sources on St. John, Virgin 

Islands (tons per year)

Source Sector Baseline 2002 2018 (with measures for RPG)

Point 43.11 43.11

Area 0.05 0.05

Non-Road Mobile 17.89 17.89

On-Road Mobile 1.61 1.61

Marine Vessels 94.06 14.11

Total 156.72 76.77

Table 2: Nitrogen Oxide Emissions from Point, Area and Mobile Sources on St. John,

Virgin Islands (tons per year)

Source Sector Baseline 2002 2018 (with measures for RPG)

Point 477.66 477.66

Area 3.69 3.69

Non-Road Mobile 2.07 2.07

On-Road Mobile 25.03 25.03

Marine Vessels 318.23 63.65

Total 826.68 572.1

Table 3: Direct Emissions of Particulate Matter from Point, Area and Mobile Sources on 

St. John, Virgin Islands (tons per year)

Source Sector Baseline 2002 2018 (with measures for RPG)

Point 34.33 34.33

Area 38.32 38.32

Non-Road Mobile 1.93 1.93

On-Road Mobile 0.73 0.73

Marine Vessels 8.57 1.28

Total 83.88 76.59
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Table 5: Emissions from HOVENSA (in tons per year)

Sulfur Oxides Nitrogen Oxides Particulate Matter

HOVENSA Base 2002 12,778 26,362 2,207

HOVENSA Future 2018 9,318 21,331 2,192
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Conclusion

Virgin Islands has a SIP that demonstrates the requirements for emission inventory measures and 

reporting are adequately met. To comply with the emission inventory requirements, the State 

must submit a complete inventory containing an implemented Quality Assurance Plan, point, 

area, on-road, and non-road mobile source data, and accompanying support documentation.

Recommendation

EPA is approving this SIP submittal because it meets the essential reporting requirements 

for an Emissions Inventory. 
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Emission Inventory Guidance Documents

1

Emission Inventory Guidance for Implementation of ozone and Particulate Matter NAAQS and 

Regional Haze Regulation, September 2005

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Example Documentation Report for 1990 Base Year Ozone and Carbon Monoxide State 

Implementation Plan Emission Inventories, March 1992

3Guidance on the Use of Models and Other Analyses for Demonstration Attainment of Air 

Quality Goals for Ozone, PM2.5 and Regional Haze, dated April 2007