




MEMORANDUM

TO:	Mary Johnson, U.S. Environmental Protection Agency, OAQPS/SPPD

FROM:	Eastern Research Group, Inc.

DATE:	June 30, 2016

SUBJECT:	Review of Mercury Data Variability for Coal-fired Area Source Boilers



1.0	INTRODUCTION

      The EPA received a petition asserting that the public lacked an opportunity to comment on a new provision in the February 2013 final amendments to the Area Source Boiler Rule (40 CFR part 63 subpart JJJJJJ) that eliminated further mercury (Hg) fuel sampling at certain coal-fired boilers, if their initial compliance demonstration shows Hg emissions are equal to or less than half of the Hg emission limit. The EPA granted reconsideration on this issue to provide an opportunity for comment on the provision. The EPA requested comment, along with supporting information, on the magnitude and range of variability in Hg content in coal that is likely to be combusted in an individual boiler. This memorandum summarizes the Hg data used to inform the EPA's decision on the Hg sampling provision in its final action on reconsideration.
      To assess the magnitude and range of variability in Hg content in coal that is likely to be combusted in an individual boiler and whether the variability within a specific fuel type or mixture could result in an exceedance of the applicable Hg limit by a boiler in the coal subcategory whose Hg content in their fuel or fuel mixture are demonstrated to be equal to or less than half of the applicable Hg emission limit, Hg data submitted through Information Collection Requests (ICRs) (approved under OMB Control No. 2060-0616) and subpart JJJJJJ reporting requirements were reviewed. Based on the ICR and WebFIRE data reviewed, there are instances where a facility has one sample below half of the emission limit but another sample that exceeds the emission limit.
2.0	ICR Data

      Fuel Analysis for Coal. The ICR emission test database showed 68 Hg fuel analysis samples that could be standardized to units of lb/MMBtu from coal-fired area source boilers. These samples represented coal used at seven different facilities. A ratio of maximum to minimum Hg emission rates was calculated to investigate intra-unit variability. For five of the facilities, the ratios were less than 2. One of the facilities had a ratio of 2.2 and another facility had a ratio of 5.8. On average, the ratio across the facilities was 2.2. Four of the seven facilities had multiple sample dates that ranged from the same day to up to two months. The remaining three facilities had sample dates that ranged from nine months to a little over two years. Therefore, this data does not necessarily show long-term variability of Hg fuel samples. 
      Four of the 68 fuel analysis samples (5.9 percent) from coal-fired area source boilers exceeded the Hg limit and all exceedances occurred at a single facility (IAMidAmericanEnergyRiverside393). Four of the 12 samples (33.3%) at IAMidAmericanEnergyRiverside393 exceeded the Hg emission limit, while six of the samples were less than half of the Hg emission limit. The maximum fuel analysis reading was 5 times higher than the minimum fuel analysis sample at the IAMidAmericanEnergyRiverside393 facility. The list of each of the facilities and the ratios of Hg fuel analysis data are shown in Appendix A-1. Appendix A-1a shows the detailed fuel sampling dates for each facility.
      Performance Tests. In the final Hg MACT floor analysis for area source coal-fired boilers, there were six boilers with Hg performance data to rank. Upon investigation of the ICR emission test database, none of these six boilers had multiple Hg emission tests available to assess intra-unit variability. 
3.0	WebFIRE Data

      Upon downloading the electronic reporting tool (ERT) files for coal-fired boilers reporting test results under 40 CFR part 63 subpart JJJJJJ, 74 different area source coal-fired boilers were identified. Three area source facilities had submitted multiple coal fuel analyses to WebFIRE, for a total of 12 different samples. These data were compared to the area source emission limit. One of the 12 samples (8.3%) exceeded the emission limit of 2.2E-05 lb/MMBtu. This facility (Norfolk Southern Railway Company (Altoona, PA)) had two other samples that were below half of the emission limit. A variability factor was calculated by dividing the maximum fuel analysis sample by the minimum fuel analysis sample. The variability factor at Norfolk Southern Railway Company (Altoona, PA) showed that mercury from the maximum fuel sample value was over 11 times higher than the minimum fuel analysis sample at the same facility. The remaining 11 samples were below the emission limit (as well as below half of the emission limit). One of the facilities had three identical samples, showing no variability, and the other facility had a variability factor of 3. The list of each of the facilities and the ratios of Hg fuel analysis data are shown in Appendix A-2.

