VISIBILITY REGULATORY TIMELINE
1977 – Congress substantially amended the Clean Air Act. The amendments included section 169A, which declared "as a national goal the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory class I Federal areas," such as national parks. Congress required EPA to adopt regulations to assure "reasonable progress toward meeting th[is] national goal." Measures for achieving reasonable progress were to include best available retrofit technology or "BART" for certain existing stationary sources and a long-term strategy.
1979 – EPA identified 156 mandatory class I Federal areas, including Grand Canyon National Park.
1980 – EPA adopted visibility regulations under section 169A of the Act. The regulations adopted a "phased approach to visibility protection." Phase I was directed at visibility impairment "that can be traced to a single stationary facility or a small group of stationary facilities." EPA required all states to submit revised visibility implementation plans within nine months. Most states failed to do so. EPA deferred addressing other types of visibility impairment, such as "regional haze" caused by a multitude of sources.
1982 – Environmental groups sued EPA to compel it to adopt federal implementation plans for those states that had failed to submit revised state plans. The parties reached a settlement agreement in 1984 that required EPA to review all state implementation plans for deficiencies and allow states to cure those deficiencies. If the states failed to cure the deficiencies, the consent decree required EPA to issue its own visibility implementation plans for such states.
1987 – EPA disapproved the state implementation plans of 29 states, including Arizona, for failing to comply with the visibility regulations. Over the next few years, EPA investigated visibility impairment at several class I areas, including Grand Canyon National Park.
1990 – Congress again amended the Clean Air Act, adding section 169B, which required, among other things, that EPA undertake research to identify "sources" and "source regions" of visibility impairment in class I areas and establish a visibility transport commission for Grand Canyon National Park. EPA established the Grand Canyon Visibility Transport Commission (GCVTC) in 1991.
1991 - EPA proposed to revise the federal implementation plan for Arizona to address wintertime visibility impairment at the Grand Canyon that it claimed was associated with sulfur dioxide (SO2) emissions from Navajo Generating Station (NGS). In October of that year, EPA issued a final rule that required a 90 percent reduction in SO2 emissions from NGS. The Central Arizona Water Conservation District (CAWCD), which operates the Central Arizona Project (CAP), challenged that rule, but the rule was upheld by the United States Court of Appeals for the Ninth Circuit. In order to comply with the rule, Salt River Project, the operator of NGS, installed SO2 scrubbers at NGS at a cost of over $400 million.
1996 – The GCVTC issued its report to EPA. The report included a series of recommendations for reducing visibility impairment attributable to man-made sources.
1997 – EPA issued a notice of proposed rulemaking for regional haze, and received more than 1,300 comments on its proposed rule.
1999 – EPA issued its final regional haze rule. The rule required that all states submit an implementation plan that provides for reasonable progress toward achieving "natural background conditions" in national parks and wilderness areas by 2064. The rule required that the states identify those sources that are subject to BART requirements and then determine what constitutes BART for such sources.
2002 – The United States Court of Appeals for the District of Columbia Circuit found EPA's regional haze rule contrary to the Clean Air Act in important respects, including because it forced the states to require BART controls at sources without any empirical evidence of the particular source's contribution to visibility impairment in a class I area.
2005 – EPA revised its regional haze rule and issued guidelines for making best available retrofit technology determinations. The rule calls for imposition of BART if a source "may reasonably be anticipated to cause or contribute to any impairment of visibility in any mandatory class I Federal area." In determining what constitutes BART for a particular source, the states (and EPA) must consider five factors, including the cost of compliance and the degree of visibility improvement which may reasonably be anticipated to result from the use of the technology. The guidelines include presumptive limits for nitrogen oxide (NOx) emissions from large coal-fired power plants, and say that these presumptive limits "are extremely likely to be appropriate" for such plants. "Based on our analysis of emissions from power plants," EPA said, "we believe that applying these highly cost-effective controls at the large power plants covered by the guidelines would result in significant improvements in visibility and help to ensure reasonable progress toward the national visibility goal." EPA's presumptive limits are based on the use of combustion controls, such as low-NOx burners, at such plants.
2008 – Salt River Project submitted its BART analysis for NGS to EPA. Based on an evaluation of the five statutory factors, SRP concluded that BART for NGS can be achieved by installing Low-NOx Burners and Separated Overfire Air (LNB/SOFA) on all three units at NGS. The primary basis for this conclusion is that the cost of the more stringent NOx control option, selective catalytic reduction (SCR), is more than 10 times the cost of LNB/SOFA, and is only predicted to result in a small visibility improvement relative to LNB/SOFA. Accordingly, SRP concluded that SCR cannot be justified as BART.
2009 – EPA issued an advance notice of proposed rulemaking (ANPR) for Navajo Generating Station and Four Corners Power Plant (FCPP). The ANPR sought comment on the propriety of several BART controls options under consideration by EPA for reducing NOx emissions from the two plants, including combustion controls and much more expensive post-combustion controls, such as selective catalytic reduction. CAWCD and Salt River Project submitted extensive comments on the ANPR, noting among other things that the NGS participants were already in the process of voluntarily installing combustion controls on all three units at NGS, and that such controls would reduce emissions to levels that are below EPA's presumptive NOx emission limits. The two organizations also argued that post-combustions controls were not cost effective and would not result in meaningful improvements in visibility beyond that achievable with combustion controls alone. NGS is the principal source of power for pumping Colorado River water through the Central Arizona Project, and CAWCD argued that a requirement to install post-combustion controls at NGS would at best increase costs to CAP water users substantially and at worst could lead to plant closure. The Navajo Nation and the Hopi Tribe argued that a requirement to install post-combustion controls at NGS would cause the two tribes enormous harm if that led to plant closure.
2011 – In February, SRP submitted to EPA, for its consideration in developing a BART proposal for NGS, a report on the results of additional visibility modeling using the newest version of the accepted visibility model. The upgraded model predicts less visibility benefit from SCR than the previous modeling conducted by SRP. A deciview (dv) is a standard measure of visibility impairment. It is generally thought that a one deciview change in visibility is at the limit of human perceptibility. SRP’s most recent studies show that the installation and operation of LNB/SOFA at NGS will produce, on average, about a third of a deciview (0.37 dv) improvement in visibility in nearby class I areas. Installation of SCRs, in addition to LNB/SOFA, would produce an incremental improvement in visibility, on average, of less than two tenths of a deciview (0.12 dv) – an imperceptible additional improvement – at a cost of another $500 million to $1 billion in capital expenses alone. This further supports SRP’s conclusion that SCR cannot be justified as BART.
2018 and beyond – The regional haze rules do not require maximum possible reductions in visibility impairing emissions during each 10-year review period but rather seek to achieve an even rate of visibility improvement in class 1 areas from the baseline visibility level to the goal of achieving visibility equivalent to natural conditions in 2064. To that end, the states (and in the case of facilities on Native American lands subject to EPA regional haze plans, such as NGS and FCPP, EPA) must complete revised regional haze plans in 2018 and every 10 years thereafter. States must also submit progress reports on “reasonable progress” goals and strategies in 2013 and every 5 years thereafter (See http://www.epa.gov/ttn/oarpg/t1/fr_notices/implemnt.pdf ).
[Prepared 6-1-11]