Competitive Power Ventures, Inc. (CPV) selected as a preferred site for a proposed 580 MW combined cycle power plant a location in Warren County, VA based on its proximity to transmission and natural gas lines and within an area of projected electric power need. However, this site location, only 7 kilometers (km) from the northern tip of Shenandoah National Park (SNP), a mandatory Federal Class I area, was not optimal or preferred as it presented major technical permitting issues due to strict Clean Air Act requirements that apply to major sources of emissions locating within 10 km of a Class I area. The challenges faced by the project, in addition to the typical New Source Review, Prevention of Significant Deterioration (PSD) permitting requirements, included requirements to address impacts on Air Quality Related Values, such as sulfur and nitrogen deposition and visibility impacts within the near-field and far-field observer locations within the Class I area. The near-field visibility analyses required the evaluation of potential impacts on visibility due to plume impairment from the project emissions, a demonstration which had not been previously attempted for a major source at the relatively close proximity to a Class I area. Also, due to the proximity of the emission sources to the Class I area, predicted impacts of certain criteria pollutants were determined to be significant at Class I receptors, thus a multi-source PSD increment analyses needed to be performed.
TRC’s solutions to the challenges presented by the project location and project
specific requirements were rooted in a commitment to work together with the
permitting agencies, e.g., EPA and VADEQ, and the federal land managers for SNP
to identify and resolve technical issues related to modeling of predicted impacts
and refine many of the overly conservative assumptions inherent in then prevailing
accepted modeling guidance. TRC modeling staff evaluated the model codes of the
approved models, including the recommended plume impairment model PLUVUE II,
and developed alternative application recommendations and appropriate model code
in the form of postprocessors to address the limiting factors in the modeling analyses.
The resulting model enhancements and new model application guidance were
presented in a modeling protocol that was subsequently approved by the EPA, FLMs
and VADEQ permitting staff. TRC also provided recommendations for developing
multisource modeling inventories that could be reasonably implemented without
causing concern regarding the veracity of the modeling results.
The ultimate benefit of the work effort performed by TRC was the issuance of a
construction permit by VADEQ for the project which withstood the challenges and
critical review by interveners and project opponents on a scientific basis. Collateral
benefits of the project have been advancements in modeling technology, especially for
plume impairment analyses, and guidance for modeling major sources in the vicinity
of sensitive protected Class I areas that have been recognized by permitting agencies
and FLMs and have been successfully applied on other projects.