On June 22, 2010, EPA published in the Federal Register a revised NAAQS for sulfur dioxide (SO₂).  Previously, EPA had primary standards for levels of SO₂ over 24-hour and annual averaging periods.  However, based on new evidence showing adverse health impacts even after shorter periods of exposure, EPA chose to set a primary NAAQS standard with a shorter averaging time and to eventually revoke the prior primary NAAQS.

The new standard is a 1-hour standard of 75 ppb, calculated as the 3-year average of the 99^th percentile of the annual distribution of daily maximum 1-hour values.  The 1-hour standard became effective August 23, 2010.

DEQ has established this website to inform interested parties on the designation and implementation process for the 1-hour SO₂ NAAQS.  The website will be periodically updated to keep stakeholders advised of the current regulatory requirements, guidance and other data resources that are relevant to the implementation of the NAAQS.  A more detailed description of the designation and implementation process is available here.

Regulations and Guidance

Primary SO₂ NAAQS Final Rule (Adobe pdf) - Federal Register publication of the final rule for the revised SO₂ NAAQS, June 22, 2010.

EPA SO₂ Designation Guidance (Adobe pdf) - EPA issued guidance on March 24, 2011, that includes the schedule and process for designating areas for the 2010 revised primary SO₂ NAAQS. The document also includes guidance on conducting air quality modeling to inform SO₂ designation decisions.

Virginia DEQ Designation Recommendation Letter with Enclosure I and Enclosure II (Adobe pdf) - Pursuant to Section 107 (d) (1) (A) of the Clean Air Act and on behalf of the Governor of the Commonwealth of Virginia, the DEQ submitted the initial recommendations and comments on the designations of areas in Virginia under the 2010 1-hour SO₂ NAAQS.

EPA Acknowledgement Letter (Adobe pdf) - EPA letter acknowledging receipt of the DEQ's initial designation recommendations.  EPA is required to promulgate the final designations no later than two years after the SO₂ NAAQS revision unless there is insufficient information. Those areas with sufficient information will be designated no later than June 3, 2012.

EPA Draft SO₂ Implementation Guidance (Adobe pdf) - This document was released by EPA on September 22, 2011.  This guidance document discusses the Clean Air Act (CAA) statutory requirements that states need to address when implementing the new 1-hour SO₂ NAAQS based on the structure outlined in the CAA and existing rules.  Comments on the draft guidance are due to EPA on or before December 2, 2011.  An extension to the comment period was granted by EPA on October 28, 2011.  The Notice of Availability contains instructions on submitting comments to EPA.

Guideline on Air Quality Models (40 CFR 51, Appendix W) - EPA’s Guideline on Air Quality Models (‘‘Guideline’’) addresses the regulatory application of air quality models for assessing criteria pollutants under the Clean Air Act.

Modeling Information

DEQ SO₂ Modeling Protocol (Adobe pdf) - This document is under development and is expected to be released in early 2012.  The protocol will describe common procedures for carrying out air quality modeling to support Virginia’s 1-hour SO₂ State Implementation Plan (SIP).

Virginia Meteorological Stations (JPEG) - This image provides a graphical representation of the National Weather Service (NWS) stations that provide raw meteorological data that can be used as input to AERMET, the meteorological pre-processor for AERMOD.  Each of these stations provide archived 1-minute winds from the Automated Surface Observing System (ASOS) that can be used to calculate hourly average wind speed and directions.  These data can be used as a supplement to the standard archive of hourly observed winds processed in AERMET.

Meteorological Data - These data are under development.  DEQ intends to provide *.zip files below that contain pre-processed meteorological data for selected NWS stations.  The data will be processed using AERMET.  To access the files you will need to unzip them using a program such as winzip, which is available at http://www.winzip.com.

DEQ Dispersion Modeling Website - This link provides additional guidance on dispersion modeling, which is used to predict the air quality impact emission sources, analyze monitored violations of the NAAQS, and assist in the the planning, and the development of rules.

Monitoring Information

SO₂ Monitoring Network (JPEG) - This image provides a graphical representation Virginia DEQ's SO₂ monitoring network.  The current network consists of eight (8) stations.

SO₂ Hourly Monitoring Data (MS Excel Spreadsheet) - This spreadsheet contains three (3) years of hourly data for Virginia DEQ's monitoring network.  Data is included for the current monitors as well as several discontinued stations.

1-Hour SO₂ Design Values (MS Excel Spreadsheet) - This spreadsheet provides a summary of the 1-hour SO₂ design values for Virginia DEQ's monitoring network.  The data are for the most recent 3-year period at each monitor.

Virginia Ambient Air Monitoring Data Report - The Virginia Ambient Air Monitoring Data Report is a compilation of air pollutant measurements made by the Virginia Department of Environmental Quality, the City of Alexandria, Fairfax County, the U.S. Department of Agriculture Forest Service, and the National Park Service.

Currently Violating Monitors (Adobe PDF) - This image provides a graphical representation of counties with monitors currently violating the revised primary 1-hour SO₂ standard, based on data collected from 2007-2009.

Projected Violating Monitors (Adobe PDF) - This image provides a graphical representation counties with monitors that are projected to violate the revised primary 1-hour SO₂ standard, based on modeling conducted for the year 2020.

Monitoring Requirements (Adobe PDF) - This image provides a graphical representation of the monitoring requirements for the revised primary 1-hour SO₂ standard.

Contacts

Modeling and Monitoring

SIP Development

Permitting and Compliance

 DEQ Regional Offices