Section 40. Episode determination

A. A condition justifying the proclamation of a watch, alert, warning or emergency stage shall be deemed to exist whenever the board determines that the accumulation of one or more air pollutants in any place, locality, county or other area in the state may attain, is attaining or has attained levels which could, if such levels are sustained or exceeded, lead to a threat to the public health. In making this determination the conditions specified in subsections B, C and D of this section shall be used as guidance.

B. Episode criteria.

1. Watch stage. An internal administrative watch shall be declared by the board whenever the national, local or department meteorologist issues a forecast indicating an atmosphere stagnation will cover any substantial portion of the state for an extended period. Such a weather forecast will indicate meteorological conditions which are expected to inhibit pollutant dispersion. The watch shall be in effect for those areas of the state covered by the weather forecast and it shall continue throughout the atmospheric stagnation period. Such weather forecasts indicating atmospheric stagnation will take the form of:

a. A regional air stagnation advisory, including any substantial part of the state, issued by the National Weather Service; and

b. A forecast by the department meteorologist indicating local meteorological conditions which inhibit dispersion for an extended period of time.

2. An alert stage shall be declared by the board when any one of the following pollutant levels is reached at any monitoring site concurrent with:

a. Consultation with the national, local or department meteorologist which indicates that an atmospheric stagnation exists; or

b. A determination by the board that the pollutant level is representative of air quality in an air quality control region and the concentrations of pollutants can be expected to remain at the following indicated levels for 12 or more hours or increase, or in the case of ozone, the situation is likely to recur within the next 24 hours unless control actions are taken. Consultation with the air pollution control agencies of the affected jurisdictions will be accomplished to help evaluate local situations.

POLLUTANT  AVERAGE  šg/má3ã  ppm 

                                 

SOå2ç      24 hour    800     .3 

PMå10ç     24 hour    350    N/A 

CO         8 hour   17,000   15.0

Ozone      1 hour     400     .2 

NOå2ç      1 hour    1,130    .6 

           24 hour    282    .15 

3. A warning stage shall be declared by the board when any one of the following pollutant levels is reached at any monitoring site concurrent with:

a. Consultation with the national, local or department meteorologist which indicates that an atmospheric stagnation exists; or

b. A determination by the board that the pollutant level is representative of air quality in an air quality control region and the concentrations of pollutants can be expected to remain at the following indicated levels for 12 or more hours or increase, or in the case of ozone, the situation is likely to recur within the next 24 hours unless control actions are taken. Consultation with the air pollution control agencies of the affected jurisdictions will be accomplished to help evaluate local situations.

POLLUTANT  AVERAGE  šg/má3ã  ppm 

                                 

SOå2ç      24 hour   1,600    .6 

PMå10ç     24 hour    420    N/A 

CO         8 hour   34,000   30.0

Ozone      1 hour     800     .4 

NOå2ç      1 hour    2,260   1.2 

           24 hour    565     .3 

4. An emergency stage shall be declared by the Governor of the Commonwealth of Virginia when any of the following pollutant levels is reached at any monitoring site concurrent with:

a. Consultation with the national, local or department meteorologist which indicates that an atmospheric stagnation exists; or

b. A determination by the board that the pollutant level is representative of air quality in an air quality control region and the concentrations of pollutants can be expected to remain at the following indicated levels for 12 or more hours or increase, or in the case of ozone, the situation is likely to recur within the next 24 hours unless control actions are taken. Consultation with the air pollution control agencies of the affected jurisdictions will be accomplished to help evaluate local situations.

POLLUTANT  AVERAGE  šg/má3ã  ppm 

                                 

SOå2ç      24 hour   2,100    .8 

PMå10ç     24 hour    500    N/A 

CO         8 hour   46,000   40.0

Ozone      1 hour    1,000    .5 

NOå2ç      1 hour    3,000   1.6 

           24 hour    750     .4 

5. Termination of any existent stage of air pollution episode shall be declared by the Governor of the Commonwealth of Virginia or the board based on:

a. Consultation with the national, local or department meteorologist which indicates that the atmospheric conditions justify termination; or

b. Appropriate reduction in pollutant levels. As the criteria for a given stage are no longer being met, the lowest appropriate stage will be assumed.

C. When the board determines that a specified criteria level is being approached and may be reached at one or more monitoring sites solely because of emissions from a limited number of sources, it may act to prevent the attainment of the episode level by notifying such sources that the preplanned abatement strategies of Table VII-A, B or C or the standby plans are required, insofar as it applies to such sources, and shall be put into effect until a satisfactory reduction in the ambient pollution concentration has been achieved.

D. The alert, warning and emergency stages may be activated on the basis of deteriorating air quality alone (i.e., an air stagnation advisory need not be in effect) subject to the determination specified in subdivisions B 2 b, B 3 b and B 4 b of this section.

Historical Notes

Derived from VR120-07-04, eff. July 1, 1991; amended, Volume 15, Issue 12, eff. April 1, 1999.

Statutory Authority

§ 10.1-1308 of the Code of Virginia.