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U.S. Virgin Islands

Area Designations for the 

2012 Primary Annual PM2.5 National Ambient Air Quality Standard

Technical Support Document

1.0 Summary

In accordance with Section 107(d) of the Clean Air Act (CAA), the EPA must promulgate designations for all 

areas of the country. In particular, EPA must identify those areas that are violating a National Ambient Air 

Quality Standard (NAAQS) or contributing to a violation of the NAAQS in a nearby area. Additionally, through 

the designation process, the EPA identifies areas that are meeting the NAAQS and those areas without 

sufficient data for the Agency to make a determination. The EPA uses a designation category of 

"unclassifiable/attainment" for areas where air quality monitoring data indicate attainment of the NAAQS and 

for areas that do not have monitors but for which the EPA has reason to believe are likely to be in attainment 

and are not contributing to nearby violations. The EPA reserves the category of "unclassifiable" for areas where 

the EPA cannot determine based on available information whether the area is meeting or not meeting the 

NAAQS or where the EPA has not determined that the area contributes to a nearby violation. The EPA must 

complete this process within 2 years of promulgating a new or revised NAAQS, or may do so within 3 years 

under circumstances not relevant to these designations.1 This technical support document (TSD) describes 

EPA’s decision to designate the U.S. Virgin Islands as "unclassifiable" for the 2012 primary annual fine particle 

NAAQS (2012 annual PM2.5 NAAQS).2

Under section 107(d), states are required to submit area designation recommendations to the EPA for the 2012 

annual PM2.5 NAAQS no later than 1 year following promulgation of the standard, or by December 13, 2013. In 

February 2014, the U.S. Virgin Islands recommended that the entire Territory identified in Table 1 be 

designated as unclassifiable for the 2012 annual PM2.5 NAAQS because of insufficient air quality monitoring 

data.

After considering these recommendations and based on EPA’s technical analysis as described in this TSD, the 

EPA is designating the entire Territory of the U.S. Virgin Islands as unclassifiable for the 2012 annual PM2.5

NAAQS. Although prior years have indicated minimal potential for violation, because current air monitoring 

data are incomplete EPA cannot determine based on available information whether the territory is meeting or 

not meeting the NAAQS. EPA's technical analysis is provided below.

 

1 Section 107(d) of the CAA requires the EPA to complete the initial designation process within 2 years of promulgation of 

a new or revised NAAQS, unless the Administrator has insufficient information to make initial designation decisions in the 

2-year time frame. In such circumstances, the EPA may take up to 1 additional year to make initial area designation 

decisions (i.e., no later than 3 years after promulgation of the standard).

2 On December 14, 2012, the EPA promulgated a revised primary annual PM2.5 NAAQS (78 FR 3086, January 15, 2013). 

In that action, the EPA revised the primary annual PM2.5 standard, strengthening it from 15.0 micrograms per cubic meter 

(μg/m3) to 12.0 μg/m3.
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Table 1. The EPA’s Designated Unclassifiable Area for the Territory of the U.S. Virgin Islands for the 

2012 annual PM2.5 NAAQS

Area The U.S. Virgin Islands

Recommended Unclassifiable

Area

EPA’s Designated Unclassifiable 

Area

U.S Virgin Islands

St. Croix

St. John

St. Thomas

St. Croix

St. John

St. Thomas

2.0 Technical Analysis 

In this technical analysis, EPA used the latest data and information available to EPA (and to the states and tribes 

through the PM2.5 Designations Mapping Tool3and the EPA PM Designations Guidance and Data web page4) 

and/or data provided to EPA by states or tribes. This technical analysis is limited to an air quality analysis 

which involves examining available ambient PM2.5 air quality monitoring data. This includes reviewing the 

design values (DV) calculated for each monitoring location in the area based on air quality data for the most 

recent complete 3 consecutive calendar years of quality-assured, certified air quality data in the EPA’s Air 

Quality System (AQS). In general, EPA identifies violations using data from suitable Federal Reference Method 

(FRM), Federal Equivalent Method (FEM), and/or Approved Regional Method (ARM) monitors sited and 

operated in accordance with 40 CFR Part 58.5 Procedures for using the air quality data to determine whether a 

violation has occurred are given in 40 CFR part 50 Appendix N, as revised by a final action published in the 

Federal Register on January 15, 2013 (78 FR 3086).6

Figure 1: Map of the Virgin Islands Unclassifiable Area

 

3 EPA’s PM2.5 Designations Mapping Tool can be found at http://geoplatform2.epa.gov/PM_MAP/index.html.

4 EPA’s PM Designations Guidance and Data web page can be found at 

http://www.epa.gov/pmdesignations/2012standards/techinfo.htm.

5 Suitable monitors include all FEM and/or ARMs except those specific continuous FEMs/ARMs used in the monitoring 

agency's network where the data are not of sufficient quality such that data are not to be compared to the NAAQS in 

accordance with 40 CFR part 58.10(b)(13) and approved by the EPA Regional Administrator per 40 CFR part 58.11(e).

6 As indicated in Appendix N to 40 CFR part 50, Interpretation of the National Ambient Air Quality Standards for PM2.5, 

section 3(a) indicates “Except as otherwise provided in this appendix, all valid FRM/FEM/ARM PM2.5 mass concentration 

data produced by suitable monitors that are required to be submitted to AQS, or otherwise available to EPA, meeting the 

requirements of part 58 of this chapter including appendices A, C, and E shall be used in the DV (design value)

calculations. Generally, EPA will only use such data if they have been certified by the reporting organization (as prescribed 

by § 58.15 of this chapter); however, data not certified by the reporting organization can nevertheless be used, if the 

deadline for certification has passed and EPA judges the data to be complete and accurate.”
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Air Quality Data

All data collected during the year are important when determining contributions to an annual standard such as 

the 2012 annual PM2.5 NAAQS. Compliance with an annual NAAQS is dependent upon monitor readings 

throughout the year, including days with monitored ambient concentrations below the level of the NAAQS. For

the 2012 annual PM2.5 NAAQS, the annual mean is calculated as the mean of quarterly means. A high quarter 

can drive the mean for an entire year, which, in turn, can drive an elevated 3-year DV. 

PM2.5 Design Values – As part of the designation process, EPA calculated DVs based on air quality data for the 

most recent 3 consecutive calendar years of quality-assured, certified air quality data from suitable 

FEM/FRM/ARM monitoring sites in the EPA’s Air Quality System (AQS). For this designation analysis, EPA 

used data for the 2011-2013 period (i.e., the 2013 design value). A monitor’s DV is the metric or statistic that 

indicates whether that monitor attains a specified air quality standard. The 2012 annual PM2.5 NAAQS is met at 

a monitoring site when the 3-year average annual mean concentration is 12.0 micrograms per cubic meter 

(μg/m3) or less (e.g., 12.1 μg/m3 or greater is a violation). A DV is only valid if minimum data completeness 

criteria are met or when other regulatory data processing provisions are satisfied (See 40 CFR part 50 Appendix 

N). The regulatory monitor in the U.S. Virgin Islands did not have complete monitoring data for the 2011-2013 

period. Therefore, EPA could not calculate a valid DV. Table 2 summarizes the available data for the 
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monitoring site in the area of analysis for the U.S. Virgin Islands.

7 There were no other FEM/FRM/ARM 

monitoring sites in the Virgin Islands. 

Table 2. Air Quality Data collected at Regulatory Monitor

Conclusion for the U.S. Virgin Islands Area

Based on the assessment described above, EPA is designating the entire Territory of the U.S. Virgin Islands as

"unclassifiable" for the 2012 annual PM2.5 NAAQS because current air quality data are incomplete. There is 

not sufficient data for EPA to make an attainment or nonattainment designation.

 

7

In certain circumstances, one or more monitoring locations within a monitoring network may not meet the network 

technical requirements set forth in 40 CFR 58.11(e), which states, “State and local governments must assess data from 

Class III PM2.5 FEM and ARM monitors operated within their network using the performance criteria described in table C4 to subpart C of part 53 of this chapter, for cases where the data are identified as not of sufficient comparability to a 

collocated FRM, and the monitoring agency requests that the FEM or ARM data should not be used in comparison to the 

NAAQS. These assessments are required in the monitoring agency's annual monitoring network plan des cribed in 

§58.10(b) for cases where the FEM or ARM is identified as not of sufficient comparability to a collocated FRM....”

County, State Monitor 

Site ID

State Rec 

NA?

2009-2011

Design

Value

2010-2012 

Design

Value

2011-2013 

Design

Value

2011

Complete 

Quarters

2012

Complete 

Quarters

2013

Complete 

Quarters

St. Croix, VI 780100012 No

Not 

Valid

Not 

Valid

Not 

Valid

0 4 0