Revision of Emission Factors for AP-42 Section 11.9 Western Surface Coal Mining Revised Final Report For U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Emission Factor and Inventory Group Research Triangle Park, NC 27711 Attn: Ron Myers (MD-14) EPA Contract 68-D2-0159 Work Assignment No. 4-02 MRI Project No. 4604-02 September 1998 Revision of Emission Factors for AP-42 Section 11.9 Western Surface Coal Mining Revised Final Report For U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Emission Factor and Inventory Group EPA Contract 68-D2-0159 Work Assignment No. 4-02 MRI Project No. 4604-02 September 1998 NOTICE The information in this document has been funded wholly or in part by the United States Environmental Protection Agency under Contract No. 68-D2-0159 to Midwest Research Institute. It has been reviewed by the Office of Air Quality Planning and Standards, U. S. Environmental Protection Agency, and has been approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. iii PREFACE This report was prepared by Midwest Research Institute (MRI) for the Office of Air Quality Planning and Standards (OAQPS), U. S. Environmental Protection Agency (EPA), under Contract No. 68-D2-0159, Work Assignment No.4-02. Mr. Ron Myers was the requester of the work. Approved for: MIDWEST RESEARCH INSTITUTE Roy Neulicht Program Manager Environmental Engineering Department Jeff Shular, Director Environmental Engineering Department July 1998 iv TABLE OF CONTENTS Page Section 1 Introduction ...................................................... 1 Section 2 Revision of AP-42 Section on Western Surface Coal Mining .................. 2 2.1 Background .................................................... 2 2.2 Recommended Changes to AP-42 Section .............................. 4 2.3 Revisions to AP-42 Section ......................................... 5 Section 3 References ....................................................... 11 v Section 1 Introduction The EPA's Office of Air Quality Planning and Standards (OAQPS), Emission Factor and Inventory Group (EFIG) develops and publishes emission factors for various applications. Factors are used by states, industry, consultants, and others in the air quality management process. The purpose of this work assignment is to assist EPA in the improvement and documentation of emission factors contained in AP-42, Compilation of Air Pollutant Emission Factors. Section 234 of the Clean Air Act Amendments (CAAA) places certain responsibilities on EFIG to develop improved emission factors for activities at western surface coal mines. Over the past 3 years, a series of studies were undertaken first to review and then to expand/improve the measured emission factor data base for western surface coal mines. The objective of this work assignment was to incorporate the results of those studies in the AP-42 Section 11.9 on western surface coal mining. The remainder of this report is structured as follows: Section 2 describes the revisions made to the surface coal mining section; References are given in Section 3; the appendices contain the revised AP-42 section and supporting information. The principal pollutant of interest is particulate matter (PM), with special emphasis placed on PM-10--particulate matter equal to or less than 10 micrometers in aerodynamic diameter (µmA). PM-10 is the basis for the current NAAQS and thus represents the size range of the greatest regulatory interest. However, much of the historical surface coal mine field measurement data base predates promulgation of the PM-10 standard; thus, most of the test data reflect particulate sizes other than PM-10. Of these, the most important is TSP, or total suspended particulate, as measured by the standard high-volume (hi-vol) air sampler. 1 Section 2 Revision of AP-42 Section on Western Surface Coal Mining Section 234 of the CAAA directed EPA to examine available emission factors and dispersion models to address potential overestimation of the air quality impacts of surface coal mining. Over the past 4 years, a series of studies have not only reviewed available emission factors but also collected new field measurements at a mine in Wyoming's Powder River Basin against which those factors could be compared and revised as necessary. This section describes how AP 42 Section 11.9—"Western Surface Coal Mining"— has been revised in response to the newer studies. The section begins with a brief overview of the recent studies. Particular emphasis is placed on changes that have occurred in "typical operating practices" since the time that the original data base supporting the current AP-42 emission factors was assembled. For example, common haul truck capacities are now two to three times greater than those represented in the old emission factor data base. 2.1 Background The current version of AP-42 Section 11.9 (included as Section 8.24 in earlier editions) was first drafted in 19834 and made use of field data collected during the late 1970s and early 1980s.5,6 Minor changes to this section were subsequently made; the changes were related to (a) emissions from blasting and (b) estimating PM-10 emissions. As noted above, Section 234 of the CAAA directed EPA to examine available emission factors and dispersion models to address potential overestimation of the air quality impacts of surface coal mining. An initial study1 thoroughly reviewed emission factors either currently used for or potentially applicable to inventorying particulate matter emissions at surface coal mines. For each anthropogenic emission source, the current emission factor was reviewed. The report concluded that additional source testing was necessary to address major shortcomings in the data base. Table 1 summarizes recommendations made in Reference 1. A second planning program2 recommended an "integrated" approach to field measurements and combined extensive long-term air quality and meteorological monitoring with intensive short-term, source-directed testing. This approach would have effectively isolated separate steps in the emission factor/dispersion model methodology. As a practical matter, funding was inadequate to support the integrated approach. Under the revised multiyear approach, source-directed measurements were to be conducted first. 2 TABLE 1. RECOMMENDATIONS MADE IN REFERENCE 1 Source Category Recommendations General • Recommended collection of field test data specific to the PM-10 size fraction. • Stressed need for independent test data against which the performance of various emission factors could be assessed. Light- and medium-duty vehicular traffic • Noted that, when applied to independent data, vehicular traffic the current emission factor could overpredict by an order of magnitude. • Recommended collection of newer, independent field data at surface coal mines. Haul trucks • Noted important changes in -- size of haul trucks commonly used -- degree of dust control/compaction of permanent haul roads since the time that the test data supporting AP42 were collected. • Recommended that collection of new haul truck emission data form a central focus of any field study. Scrapers • Stressed need for independent test data to assess emission factor performance. Coal/overburden material transfers (e.g., shovel, • Stressed need for independent test data to truck unloading, dragline, etc.) assess emission factor performance. Testing occurred during the fall of 1992 at the Cordero Mine in Wyoming's Powder River Basin.3 Thirty-six PM-10 emission tests, distributed over various sources and five test sites, were performed. In keeping with priorities established in the earlier emission factor review,1 a majority of the field effort was devoted to emissions from haul truck traffic. A fairly broad spectrum of haul road dust control was tested, ranging from essentially unimproved overburden haul routes to extremely well-controlled coal haul roads. TSP emission tests were run concurrently with 22 of the PM-10 tests. In addition, three PM-10 and three TSP tests of light-duty captive traffic on permanent coal haul roads were completed. These tests were performed to quantify the importance of light-duty versus haul truck traffic on the roads. Finally, two tests of scraper travel also were conducted. 3 2.2 Recommended Changes to AP-42 Section This section discusses how changes to Section 11.9 originated. In general, there were three sources of recommended changes: A. The 1992 field study3 provided independent test data and produced the following set of recommended changes in the AP-42 section for western surface coal mining: A.1 The "generic" unpaved road emission factor equation in Section 13.2.2 was recommended for use in estimating emissions from light- to medium-duty vehicles at surface coal mines. A.2 The current haul truck emission factor could not accurately predict the new emission test data. Consequently, revision of the haul truck emission factor was necessary. B. The EPA EFIG staff requested that: B.1 Quality ratings in Section 11.9 be thoroughly reviewed. B.2 Typographical errors--which arose in January 1995 when Section 8.24 was reformatted for inclusion on the CHIEF web site as Section 11.9--be corrected. B.3 A reference to the wind erosion emission estimation procedures included in Section 13.2.5 will be included in this section. C. Early in the work assignment, MRI sent a summary of planned changes to Section 11.9 to a representative of the mining