Opinion ID: 786322
Heading Depth: 2
Heading Rank: 2

Heading: New York's Plan

Text: 12 Although New York submitted a plan in the past, it was required to revise that plan to comply with the Clean Air Act's 1990 amendments. The present dispute concerns New York's 1998 submission of its one-hour ozone attainment demonstration for the New York City air quality control region. Approval and Promulgation of Implementation Plans, New York, 64 Fed.Reg. 70,364, 70,375 (proposed Dec. 16, 1999). EPA's one-hour standards for ozone — the maximum average concentration of ozone measured over a one-hour period — is 0.12 parts per million (ppm). 40 C.F.R. § 50.9. For models using three digits, EPA uses rounding conventions to permit up to 124 parts per billion (ppb). 2 13 New York's attainment demonstration used a type of EPA-approved photochemical grid modeling called the Urban Airshed Model to predict the concentration of ozone levels in 2007, following EPA's protocols in the application and validation of the model. 40 C.F.R. pt. 51 app. W. Using meteorological data from two extreme ozone events in 1988 and 1991, New York's model predicted that comparable weather events in 2007 would create measurements of 171 ppb based on the 1988 conditions and 169 ppb based on the 1991 conditions. Each of these results significantly exceeds the maximum permissible level of 124 ppb. 14 Recognizing that these results were too high and believing that the Urban Airshed Model contained inaccuracies that tended to produce high results, New York applied weight of the evidence analysis to adjust the high test results. Weight of the evidence analysis is essentially a totality of the circumstances approach, one that considers all available data to evaluate the reasonableness of the modeled results and which supplements those results. The agency views weight of the evidence analysis (or supplementary analysis) as helpful to addressing uncertainties that exist in the photochemical grid modeling. In a 1996 manual used to guide attainment of national air quality ozone standards, it reasoned, First, photochemical grid models require a great deal of information. Much of this information is uncertain. Further, model formulation reflects limits imposed by existing scientific knowledge as well as by computational necessities. Uncertainties in model inputs and limitations in model formulation lead to uncertainties in model predictions. This uncertainty requires a revised attainment test. A second finding from recent model applications is that controls estimated as necessary to attain the [national air quality standards] can be very high. Despite such estimates, monitored ozone data reflect downward trends in many areas over the past 10 years (U.S. EPA, 1994). Monitored data are the definitive means for classifying an area's attainment status. Office of Air Quality Planning and Standards, U.S. EPA, Guidance on Use of Modeled Results to Demonstrate Attainment of the Ozone NAAQS, EPA-454/B-95-007, at § 1.2 (June 1996) [hereinafter Guidance on Modeled Results]. 15 It is now thought that the modeled attainment test may be too conservative. Because of the inherent imprecision of the model other means must be looked at to determine if a plan's controls will lead to attainment. 16 The process by which this is done is called a weight of evidence (WOE) determination. Under a WOE determination, a state can rely on, and EPA will consider in addition to the results of the modeled attainment test, other factors such as other modeled output ( e.g., changes in the predicted frequency and pervasiveness of 1-hour ozone NAAQS exceedances, and predicted change in the ozone design value); actual observed air quality trends ( i.e. analyses of monitored air quality data); estimated emissions trends; and the responsiveness of the model predictions to further controls. 17 Approval and Promulgation of Implementation Plans, New York, 67 Fed.Reg. at 5175. 18 After New York conducted its weight of the evidence analysis, it concluded that the adjusted results were in the range of 118 to 122 ppb, and New York therefore believed it had satisfied the attainment requirements. EPA independently considered the results of New York's tests. Its Urban Airshed Model test results, like New York's, yielded results well beyond permissible levels, but, applying its own weight of evidence analysis lowered its 2007 predictions to 129 ppb, slightly above the required air quality standards. 19 EPA and New York offer two reasons for New York's high results from the model. First, they assert the output of the model does not match the applicable air quality standard. The actual standard, which determines attainment, allows a certain number of episodes exceeding the 124 ppb requirement. These are called exceedances. The control area measured over a three-year period is permitted up to three exceedances during this period. Thus, the fourth highest reading during that period, known as the design value, is the crucial result to determine whether attainment has been achieved. Because the computer model only predicts peak readings, it does not ascertain what is the area's all-important design value. 20 Second, the agency and New York maintain the model's results were inconsistent with other evidence. In particular, they observed that the model predicted nearly equivalent results in 2007 as the results measured in the period 1995-98. Because several emission control strategies implemented after 1999 were not included in the model, EPA and New York believed the model over-predicted the 2007 results. Noting there is limited data on how accurate the model is in predicting future ozone levels, EPA and New York both determined that further weight of the evidence analysis was warranted. 21 Even after the supplementary analysis, New York's predicted ozone level was still slightly above the air quality standards. In response to this shortfall, New York offered commitments to adopt and submit additional control measures by October 31, 2001. As part of the commitment, New York submitted reports detailing some of the steps it would take, including reducing emissions of ozone precursors and adopting six emission reduction measures recommended by the Ozone Transport Commission. The state concedes that it missed its deadline, but it continued to update EPA on its progress, and both New York and EPA insist the delay would not prevent New York from attaining the ozone standards by 2007. 22 EPA approved New York's plan after public notice and an opportunity for comment. Approval and Promulgation of Implementation Plans, New York, 67 Fed.Reg. 5170. The agency formally approved of the use of weight of the evidence analysis to supplement the results of the photochemical grid model. It also accepted New York's enforceable commitments to close the gap and excused the late submission of those commitments, determining that New York was sufficiently on track so that it would attain required air quality standards by the attainment date. Id. at 5188.