Under a proposed federal implementation plan (FIP), owners and operators of the Navajo Generating Station (NGS) will be required to meet a stringent emissions limit for nitrogen oxide (NOx) by 2018.  However, the EPA is also proposing an alternative that will give the plant an additional 5 years to come into compliance.  According to the Agency, the proposed alternative is appropriate because of unique circumstances surrounding the NGS. The NGS is located on the Navajo Indian Reservation and is jointly owned by the U.S. Bureau of Reclamation and five public and private water and electric utilities.  With a capacity of 2,250 megawatts (MW), the NGS is the largest coal-fired power plant in the West.

Regional haze rules

Under the federal regional haze rules (RHRs), the EPA determines the best available retrofit technology (BART) that must be undertaken by sources to control haze that impairs visibility at Class I national parks, forests, and wilderness areas.  States usually are responsible for implementing the RHRs, but the EPA shoulders the job on Indian reservations.  BART must be installed and operated as expeditiously as possible but no more than 5 years after EPA’s final action identifying BART.
The intent of the NGS FIP is to reduce emissions that contribute to regional haze affecting visibility at 11 national parks and wilderness areas, including the Grand Canyon, which is less than 20 miles from the NGS.  For the NGS, the EPA determined that BART is a combination of selective catalytic reduction and low-NOx burners with separated over-fire air (LNB/SOFA).  According to the Agency, these technologies will enable the NGS to achieve the required plantwide emissions limit of 0.055 pounds of NOx per million metric BTUs (lb/MMBtu) within the required 5-year time frame.   

Possible plant closure

But the EPA has recognized certain special circumstances associated with the NGS.  Primarily, the plant and nearby Kayenta mine, which supplies the NGS with coal, collectively employ nearly a thousand workers, about 90 percent of whom are Native Americans.  Cost estimates to install the LNB/SOFA technologies vary between $500 million and $1 billion.  Faced with that expense over a short 5-year term, the facility owners would need to increase rates by up to 20 percent, according to the Central Arizona Project, a supplier of renewable water in Arizona and the state’s biggest user of electricity.  Also, the federal government relies on the NGS to meet the requirements of water settlements with several tribes.  Conceivably, the cost of the BART requirement could force closure of the NGS and have a devastating effect on the local economy, the provision of water, and the welfare of dependent populations.

Better-than-BART

With those circumstances in mind, the EPA has proposed that the NGS could come into compliance with the RHRs through an alternative to BART.  The NGS would still be required to meet the NOx limit of 0.055 lb/MMBtu.  However, instead of the 5-year compliance deadline for the entire facility, the three units at the plant would be allowed to achieve the emissions limit one unit per year in 2021, 2022, and 2023.  According to the Agency, the alternative is permissible under the RHR’s “better-than-BART” provisions.  Specifically, an extension of the 5-year time frame is allowable if the better-than-BART option results in lower emissions as calculated over a specific number of years, in this case, the 2009 to 2044 period.   The EPA believes this is the case since the NGS undertook voluntary installation and operation of LNB/SOFA between 2009 and 2011.  These actions produced a “credit” of 92,175 tons of NOx reductions that can be used to validate the better-than-BART alternative.
EPA’s proposal includes several additional possible alternatives that would also extend the BART deadline.  The Agency has invited the public to propose other approaches to enable the NGS to meet the NOx emissions limit as required by the RHRs.

Click here for more information on EPA’s proposal.