(CN) - The 9th Circuit refused to "rubber stamp" the Environmental Protection Agency's approval of California's plan to clean up the air in San Joaquin Valley, finding that the agency ignored recent ozone emissions data.
     The Sierra Club and four other environmental groups successfully argued to the three-judge panel that the EPA relied on outdated vehicular emissions calculations from 2004, rather than the more recent 2007 emissions data, according to the ruling.
     California struggled to meet EPA air guidelines after the valley was classified as a "serious" nonattainment area under the 1-hour ozone standard in 1991, Judge Ronald Gould writes.
     The EPA finally approved the 2004 state implementation plan (SIP) for the San Joaquin Valley in March 2010 - almost six years after the state's original submission and just eight months before California is supposed to meet the attainment deadlines under the plan, according to the ruling.
     The environmental groups claim the agency used data from 2004 that is no longer relevant.
     Judge Gould agrees, finding that the EPA ignored disparities in emission calculations between the 2004 SIP and the 2007 SIP, and then failed to explain why it didn't consider the more recent data.
     "For example, the 2004 SIP emission inventory estimate for total Valley [nitrogen oxides] emissions
     in 2008 was 429.1 tons per day, but the same estimate for 2008 rose to 597.8 tons per day in the 2007 SIP," the judge writes.
     The San Joaquin Unified Valley Air Pollution Control District argued that the EPA was not required to analyze the 2007 emissions report because it was based on 8-hour ozone data, the ruling says. The district claims it would not be an "apples to apples comparison" to the 2004 1-hour ozone report, according to the ruling.
     While the judge admits that there may be variations in the two reports' conclusions, he says the 2007 data showed much higher expected emissions.
     "Given [nitrogen oxides'] integral role in the creation of harmful ground-level ozone, this disparity should have alerted EPA to the possibility that the 2004 Plan may have been significantly flawed," the judge writes.
     "The EPA seems concerned that requiring States to rework previously submitted or recently approved SIPs whenever a new model becomes available would pose an obstacle to EPA approval," Gould writes.
     However, the agency should not be allowed to lean on "stale" data when newer data is on hand, the judge writes.
     The circuit remands the case back to the EPA so that the agency can review the plan using the more current emissions data.
     According to the Hanford Sentinel, the Valley had a perennial ozone standard violation in 2010 that triggered a $29 million federal air pollution penalty. As a result, motorists must reportedly pay $12 as part of their vehicle registration fees to cover the cost of the fine.
     Sierra Club, along with Medical Advocates for Healthy Air, Committee for a Better Alvin, Comite Residentes Organizados al Servicio del Ambiente Sano and the Association of Irritated Residents, also listed EPA Region IX Regional Administrator Jared Blumenfeld as a defendant.
     "This is a real-world problem, not a legal game," attorney Paul Cort of Earthjustice Legal Defense, who represents Sierra Club and Medical Advocates, told the Fresno Bee. "These peak levels of ozone are dangerous."