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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. EPA must complete 

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

circumstances not relevant to these designations.1 This technical support document (TSD) describes the EPA’s 

intent to designate areas in 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 based on insufficient air quality monitoring 

data.

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

EPA intends to designate the areas listed in Table 1 as unclassifiable for the 2012 annual PM2.5 standard.

 

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 U.S. Virgin Islands’ Recommended Areas and EPA’s Intended Designated Areas for the 

2012 annual PM2.5 NAAQS

Area The U.S. Virgin Islands

Recommended Unclassifiable

Counties

EPA’s Intended Unclassifiable 

Counties

U.S Virgin Islands

St. Croix

St. John

St. Thomas

St. Croix

St. John

St. Thomas

Even though air quality data from prior years have indicated minimal potential for violation, EPA intends to 

designate the entire Territory of the U.S. Virgin Islands as “unclassifiable” for the 2012 annual PM2.5 NAAQS 

because current air quality data from monitoring sites are incomplete. Because the current data are incomplete, 

EPA cannot determine based on available information whether the ambient air concentration of PM2.5 in this 

area is at, above, or below the NAAQS.

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. Because EPA determined that 

the air quality data for this area was not complete and thus could not determine whether the area was attaining 

or not attaining the standard, and due to the isolated location of the Virgin Islands, EPA did not in this case go 

on to analyze any of the other four designation factors to determine whether any nearby areas were contributing 

to any potential violations. This air quality analysis 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

 

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 
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Figure 1 is a map of EPA’s intended unclassifiable boundary for the U.S. Virgin Islands. 

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 depends on 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 

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

 

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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PM2.5 Design Values and Total Mass Measurements - 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 designations analysis, EPA 

used data for the 2011-2013 period (i.e., the 2013 design value), which are the most recent years with fullycertified air quality data. 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). Table 2 identifies the 

current design value(s) (i.e., the 2013 DV) and the most recent three design values based on all monitoring sites

in the area of analysis for the U.S. Virgin Islands intended unclassifiable area.7In fact, the EPA concluded that 

there were no available design values for the St. Croix monitor, the only FRM monitor in the Virgin Islands, 

due to incomplete data. There are no other FEM/FRM/ARM monitoring sites in the Virgin Islands. St Thomas

currently has a TEOM8 monitor9, which was most recently operational in 2008; however this monitor, by 

regulation10, cannot be used for designations purposes

Table 2. Virgin Islands Regulatory Monitor Design Values (all DV levels in μg/m3)

Conclusion for the U.S. Virgin Islands Area

Based on the assessment described above and the fact that the air quality monitoring data from the St. Croix, VI 

regulatory monitor is incomplete, EPA intends to conclude that the entire Virgin Islands Territory should be 

designated unclassifiable. Because the current data are incomplete, EPA cannot determine based on available 

information whether the ambient air concentration of PM2.5 in this area is at, above, or below the NAAQS.

 

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 described in 

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

8 Tapered element oscillating microbalance

9 TEOM monitors are not considered FEM, FRM, or ARM site, and could not be used for designations.

10 Appendix N to 40 CFR Part 50 – Interpretation of the National Ambient Air Quality Standards for PM2.5

County, 

State

Monitor 

Site ID

State Recommends

Nonattainment?

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