Permit Guidance: Modeling Guidelines (Environmental Evaluation)

Revised 09/2008

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INTRODUCTION

This document provides general guidelines to individuals preparing to submit modeling protocols and air dispersion models in support of air quality permit applications. An air quality modeling analysis (e.g., dispersion modeling demonstration) is generally required by air quality management agencies to assess the likely air quality impacts from operations at a stationary source, and to show whether the stationary source will be able to operate in compliance with applicable ambient air quality standards under the proposed permit conditions. An air quality modeling analysis is an integral part of the environmental evaluation requirement in NAC 445B.308. The air dispersion modeling impact assessment provides the technical basis for NBAPC decision-making with respect to the issuance of stationary-source air quality permits.

MODELING PROTOCOLS

Prior to performing and submitting an air quality modeling analysis, the Nevada Division of Environmental Protection-Bureau of Air Pollution Control (NBAPC) recommends that the applicant prepare and submit a modeling protocol prior to submitting the actual permit application and environmental evaluation. A modeling protocol is a detailed plan on how the applicant intends to perform an air dispersion modeling analysis, which is the primary component of the overall environmental evaluation submitted with an air quality permit application. When renewing permits, applicants are bound by regulation to submit complete applications within certain specified timeframes. As such, we recommend that permit holders submit modeling protocols well ahead of the statutory deadlines in which Class I and Class II permit renewal applications are to be submitted.

There is no regulatory timeframe the NBAPC has to meet for review of modeling protocols. The NBAPC recommends that applicants plan for a 30-day review period, once the protocol is received by the NBAPC. Subsequent to the review, the NBAPC will issue a letter to the applicant that includes comments and recommendations on how the modeling analysis might be improved, and/or to specify concurrence with individual components of the applicant’s modeling approach.

Although submission of a modeling protocol is optional, the applicant benefits from a preliminary review of their modeling approach by the NBAPC, because problems can be vetted and corrected prior to submittal of a formal permit application.

We remind all applicants that submission of an incomplete or inconclusive modeling analysis may result in the NBAPC either deeming the application incomplete, or denial of the permit application.

The NBAPC is prohibited from approving an air quality permit application if, after independent review of the environmental evaluation and modeling analysis, it determines that operation of the stationary source, under the proposed permit conditions, will result in a negative air quality impact. A negative air quality impact is defined as an exceedance of any applicable air quality standard, as demonstrated through dispersion modeling or direct measurement of the concentrations of regulated pollutants in ambient air.

As part of the technical review of a permit application, the NBAPC performs an internal critique of all modeling analyses, prior to making a final decision on whether to issue or deny an application for an air quality permit. In the event that the NBAPC is obligated to prepare the modeling analysis and environmental evaluation, the applicant must provide all required information so that the NBAPC can perform its own independent modeling analysis. The required information includes, but is not limited to, the following:

• A proposed emission inventory of all regulated air pollutants including those from insignificant activities;
• Stack parameters (e.g., height, diameter, flowrate, temperature, location, etc.);
• Locations of emission units in Universal Transverse Mercator (UTM, meters, NAD 83) coordinates;
• Facility plot plans (with scale bar and north arrow);
• Building locations (in UTMs) and dimensions;
• The coordinates of the property fenceline and/or property boundary limits (in UTMs);
• Terrain features (Digital Elevation Models, DEMs);
• Raw and processed meteorological data.

The NBAPC does not provide training on air dispersion modeling. It is the applicant’s responsibility to understand and follow correct modeling procedures and to know how to use the appropriate regulatory dispersion models. Therefore, the time and expense of preparing an environmental evaluation is the obligation of the applicant.

Please click on the link below to download the entire modeling guidelines.

Modeling Guidelines ( File is in PDF format )
File	Size (kb)
Modeling Guidelines	297

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