The Denver metropolitan area is expected to meet the 2008 federal ozone standard of 75 parts per billion (ppb), officials at the Regional Air Quality Council (RAQC) said recently, but it may turn out to be too little too late, since the Obama administration has already raised the standard.
Denver now faces a more stringent new ozone cap of 70 ppb -- set in October 2015 -- which it almost certainly cannot meet. It is a standard that is troubling not just to Colorado, but other state and industry officials throughout the West.
At a Nov. 17 hearing of state air-quality regulators, RAQC Executive Director Ken Lloyd testified on the details of a proposed state implementation plan (SIP) for attaining the 2008 standard of 75 ppb. Lloyd told the regulators that the SIP meets all the federal Clean Air Act requirements, and will result in significant emissions reductions. Attainment demonstrations predicted ozone levels at or below the 2008 standard next year, Lloyd said, but his assessments did not account for migrating ozone concentrations moving across western states.
In the western United States, "background" ozone comes into the country from other nations and from natural sources such as wildfires, and prevailing winds transport this background ozone from state to state. Lloyd estimated that 75% of Denver's ozone comes from outside the metro area, citing a federal study that said locally produced ozone amounts to less than 20 ppb.
While Colorado officials and stakeholders acknowledge that the state has made steady progress in air quality over the past 30 years, some environmental groups are critical of where the state is in terms of ozone mitigation. The Denver Post has criticized the American Lung Association's support of the more stringent 70 ppb standard, which has also been criticized by business and industry.
In the meantime, even the U.S. Environmental Protection Agency, which set the tougher standard, has said 70 ppb is unreachable for Denver.
Colorado's two top Democrats -- Gov. John Hickenlooper and U.S. Sen. Michael Bennet -- have expressed serious reservations about the new 70 ppb standard. Hickenlooper has called for the new ozone limit to be suspended, leaving the 75 ppb standard in place until the background ozone issue can be properly addressed.
At the state hearing earlier this month to approve new measures for reaching 75 ppb, the business community questioned the soundness of rewriting all the rules in an attempt to reach 70 ppb. Putting together the plan for 75 ppb already was a very complex task involving many months of work by state regulators, local officials and representatives from impacted sectors of the economy, according to officials with the Colorado Association of Commerce and Industry.