On December 11, 2013, the Colorado Department of Public Health (CDPHE) issued its Draft Colorado Greenhouse Gas Inventory – 2013 Update (the GHG Update); a report required every five years. The GHG Update summarizes all of Colorado's GHG emissions and sinks from 1990 to 2030. To generate the GHG Update, CDPHE used the Environmental Protection Agency's (EPA's) model for assigning emission factors and making emission projections. EPA's model contains Colorado-specific default values, but still relies on numerous assumptions and uncertainties that affect the accuracy of the projections. For example, CDPHE states that for the final inventory, it "will consider how to customize values to more accurately reflect Colorado GHG emissions." For affected industry participants wishing to comment on the GHG Update, comments on the report are due January 31, 2014.