Document ID: EPA-R10-OAR-2019-0412-0002
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2020-05-19T04:00Z

Design Value for air quality monitors in the
                    Fairbanks, AK PM2.5 Nonattainment Area
                          Technical Support Document

Summary
This document provides the Design Value (DV) computation for the North Pole Hurst Road PM2.5 monitoring site which is currently the defining monitoring site for the Fairbanks Nonattainment Area (NAA).  The computation confirms that the Fairbanks NAA is not attaining the 2006 24-hour PM2.5 NAAQS for 2017-19.
Background
Under EPA regulations at 40 CFR part 50, Appendix N, the 2006 primary and secondary 24-hour PM2.5 NAAQS are met within a nonattainment area when the 24-hour PM2.5 NAAQS DV at each eligible monitoring site is less than or equal to 35 μg/m3. Three years of valid annual PM2.5 98th percentile (p98) mass concentrations are required to produce a valid 24-hour PM2.5 NAAQS DV. 
The EPA's determination of attainment is based upon data that have been collected and quality-assured in accordance with 40 CFR parts 50 and 58 and recorded in the EPA's AQS database.
Data Quality Review
The 2017 through 2019 ambient concentration and quality assurance data has been certified and uploaded to AQS by Alaska DEC. A data quality review of the Fairbanks PM2.5 data was performed, and it found that the samplers and data met or exceeded data quality criteria specified in 40 CFR parts 50 and 58 for precision, bias, and data completeness.  Based on these results the Fairbanks NAA PM2.5 data has been deemed to be of necessary quality for determining valid DVs for the 2017-19 timeframe.
Design Value Computation
For the 2006 24-hour PM2.5 NAAQS, the 3-year Design Value is calculated as the average of annual p98 values, i.e., DV = [(p98 - year 1) + (p98 - year 2) + (p98 - year 3)] / 3.  The p98 values for the Hurst Road PM2.5 monitors in 2017, 2018, and 2019 are 75.5, 52.8, and 78.3 μg/m3 respectively.   The 2017-19 DV would therefore compute to (75.5 + 52.8 + 78.3)/3 = 206.6/3 = 68.9, which rounds to 69 μg/m3.   As this DV is greater than 35 μg/m3, this confirms that the Fairbanks NAA is not meeting the 2006 24-hr PM2.5 NAAQS based on the most recent three years of certified, quality assured data.