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CONSERVATION GROUPS’ COMMENTS <br />UNCOMPAHGRE FIELD OFFICE RMP AND DEIS <br />70 <br /> <br />Assuming a lower-bound leak rate of 1%—which is approximately one-third lower than <br />the EPA estimate of methane emissions in the Inventory of U.S. GHG Emissions and Sinks: <br />1990-2011 229—methane emissions from gas production by the proposed action could represent a <br />meaningful contribution of emissions over the life of the developed field.230 Assuming an upper- <br />bound leak rate of 12%—the high end of the rate found in a 2012 study using air sampling over <br />the neighboring Uinta Basin 231—methane emissions from gas could be truly significant indeed. <br />Although there is substantial variability between the 1% and 12% emission leak rates—and, even <br />without specific data from the proposed action, we can assume leakage somewhere between <br />these two extremes—even at the low end emissions would not be trivial. <br /> <br />The BLM discloses estimated annual methane emissions from the proposed action to be <br />135,083 metric tons. See DEIS (Table 4-9). However, BLM does not disclose what leak rate this <br />calculation represents. Furthermore, the BLM underestimates the climate impact of these <br />emissions. Specifically, BLM uses a global warming potential (GWP) of 21 over a 100-year time <br />horizon (meaning that methane is assumed to be 21 times as potent as CO2 over a 100-year time <br />horizon). DEIS at 4 -38. This assumption is derived from a 1996 report from the <br />Intergovernmental Panel on Climate Change (“IPCC”). However, the 100-year GWP for <br />methane was updated by the IPCC in a 2013 Report to reflect that methane is 36 times as potent <br />as CO2. Additionally, the IPCC’s new research has calculated that methane is 84 times as potent <br />as CO2 over a 20-year time horizon.232 Furthermore, recent peer-reviewed science demonstrates <br /> <br />(attached as Exhibit 118); Anna Karion et. al., Methane Emissions Estimate from Airborn <br />Measurements Over a Western United States Gas Field, 40 Geophysical Research Letters 4393 <br />(2013) (finding emissions of 6 to 12 percent, on average, in the Uintah Basin) (attached as <br />Exhibit 119); Gabrielle Pétron et al., A New Look at Methane and Nonmethane Hydrocarbon <br />Emissions from Oil and Natural Gas Operations in the Colorado Denver-Julesburg Basin, 119 <br />Journal of Geophysical Research: Atmospheres 6836 (2014) (finding leak rates averaging 4% in <br />the Denver-Julesburg Basin) (attached as Exhibit 120); see also Joe Romm, Study of Best <br />Fracked Wells Finds Low Methane Emissions But Skips Super-Emitters, ThinkProgress <br />(September 19, 2013), https://thinkprogress.org/study-of-best-fracked-wells-finds-low-methane- <br />emissions-but-skips-super-emitters-1d20bb873fc8#.hb1wfflq6; U.S. Gov’t Accountability <br />Office, GAO-11-34, Opportunities Exist to Capture Vented and Flared Natural Gas, Which <br />Would Increase Royalty Payments and Reduce Greenhouse Gases 25 (October 2010) (using a <br />conversion factor of .4045 MMTCO2e/Bcf for vented gas) (attached as Exhibit 121). 229 See U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and <br />Sinks: 1990-2011 (April 2013) (attached as Exhibit 122). 230 See U.S. Environmental Protection Agency, Greenhouse Gas Equivalencies Calculator, <br />available at: http://www.epa.gov/cleanenergy/energy-resources/calculator.html. 231 See Brian Maffly, Uinta Basin gas leakage far worse than most believe, THE SALT LAKE <br />TRIBUNE (Aug 05, 2013), available at: http://www.sltrib.com/sltrib/news/56692751-78/basin- <br />carbon-emissions-gas.html.csp (“Between 6 percent and 12 percent of the Uinta Basin’s natural <br />gas production could be escaping into the atmosphere.”). 232 G. Myhre et al., Anthropogenic and Natural Radiative Forcing, in INTERGOVERNMENTAL <br />PANEL ON CLIMATE CHANGE, Working Group I Contribution to the IPCC Fifth Assessment