2022-12-19_GENERAL DOCUMENTS - C1981010

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in the Yampa River Basin has begun recently, conducted by the Electric Power Research Institute (EPRI) and funded by the Colowyo Coal Company, L.P. and their parent organization, Tri-State Generation and Transmission Association, Inc. Results of that study will aid in planning for the recovery of endangered fish and other listed species potentially affected by mercury contamination in the Yampa and White River Basins. While mercury emission and subsequent deposition occurs at varying spatial scales (i.e., globally, nationally and regionally),this consultation evaluates the potential for mercury emitted from the combustion of Trapper coal at the Craig Generating Station and its possible impact to the Colorado River Fish and their habitat. Two coal fired power plants operate in the region; the Craig Generating Station is located near Craig, Colorado and the Hayden Generating Station is sited approximately four miles east of Hayden, Colorado (21 miles east of the Craig Generating Station). According to the BA,Trapper Mine sends all of its produced coal to the Craig Generating Station; their coal supplies as much as 54 percent of the annual fuel for the Craig Generating Station. In 2014 (the last year data are available), the Craig Generating Station emitted 19.2 kg of mercury. In that year, the total coal consumption rate for Craig Generation Station was about 4.6 million tons (mtpy) of coal,which means that Trapper Mine contributed at a rate of 2.3 mtpy. The Craig Generating Station has three power generating units, and Trapper Mine coal is almost exclusively used at Units 91 and 92. Based on 2014 load data reported to the EPA Clean Air Markets database,Units 91 and 92 represented 63.56 percent of the total electric load generated at Craig Generation Station. If the load and coal consumption are assumed to be directly related, then the coal consumption at Units 91 and 92 would have been 2.92 mtpy in 2014 (63.56 percent of 4.6 mtpy). Using this figure,the 2.3 mtpy contributed by Trapper Mine would have been 78.76 percent of the overall coal consumption at Units 91 and 92. Emissions monitoring data obtained from CDPHE for 2014 show that mercury emissions are substantially less at Unit 91 (2.0 kg) and Unit 92 (2.20 kg) compared to Unit 93 (15.28 kg). This is most likely due to the differences in pollution control systems at the three Craig generating units. Units 91 and 92 each use wet scrubbing systems for sulfur dioxide (SO2) emissions control, compared to a spray dryer absorber(dry scrubbing) at Unit 93. Wet scrubbing systems have been shown to be extremely effective at providing ancillary control benefits for mercury emissions. This is because the oxidized form of mercury (Hg2+) is water soluble and can be readily removed by the wet scrubber technology. Applying the 78.76 percent factor to the reported 2014 mercury emissions listed above,the Trapper contribution to the Craig mercury emissions would be 1.57 kg at Unit 91 and 1.73 kg at Unit 92. Adjusting the mercury emissions estimate to the maximum production rate of 2.6 mtpy under the proposed action would result in mercury emissions of 3.73 kg per year that is attributable to combustion of Trapper Mine coal at the Craig Generating Station. The proposed action assumes a constant rate of mining at Trapper Mine and a stable rate of combustion at the Craig Generating Station each year from July 1, 2015, through the life of the mine in 2024. This would result in a total of 35.06 kg of mercury emitted from the Craig 45