WAC 173-433-140. Criteria for impaired air quality burn bans

Ecology or a local air authority may call an impaired air quality burn ban as follows: (1) Stage 1 impaired air quality burn ban: (a) Ecology or the local air authority may call a stage 1 impaired air quality burn ban when they predict that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty-five micrograms per cubic meter within forty-eight hours. (b) Pierce, Snohomish, and Yakima counties each contain at least one area at risk for nonattainment. In these counties, the local air authority may call a stage 1 impaired air quality burn ban when they predict that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty micrograms per cubic meter within seventy-two hours. (2) Stage 2 impaired air quality burn ban: (a) Ecology or the local air authority may call a stage 2 impaired air quality burn ban when all of the following conditions exist: (i) A stage 1 impaired air quality burn ban is already in effect and has not reduced the trend of rising PM-2.5 levels adequately. (ii) The twenty-four hour average of PM-2.5 levels have already reached or exceeded twenty-five micrograms per cubic meter. (iii) Ecology or the local air authority expects that PM-2.5 levels will remain above twenty-five micrograms per cubic meter for twenty-four hours or more from the time PM-2.5 levels reached the trigger in (a)(ii) of this subsection. (b) Ecology or the local air authority may call a stage 2 impaired air quality burn ban without calling a stage 1 impaired air quality burn ban when all of the following conditions exist: (i) The twenty-four hour average of PM-2.5 levels have reached or exceeded twenty-five micrograms per cubic meter. (ii) PM-2.5 levels have risen rapidly. (iii) Ecology or the local air authority predicts that the twenty-four hour average of PM-2.5 levels will exceed thirty-five micrograms per cubic meter within twenty-four hours. (iv) Weather conditions alone are highly unlikely to help decrease PM-2.5 levels sufficiently. (c) Pierce, Snohomish, and Yakima counties each contain at least one area at risk for nonattainment. In these counties, the local air authority may call a stage 2 impaired air quality burn ban without calling a stage 1 impaired air quality burn ban when all of the following conditions exist: (i) The twenty-four hour average of PM-2.5 levels have reached or exceeded twenty-five micrograms per cubic meter. (ii) PM-2.5 levels have risen rapidly. (iii) The local air authority predicts that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty micrograms per cubic meter within twenty-four hours. (iv) Weather conditions alone are highly unlikely to help decrease PM-2.5 levels sufficiently. (3) Ecology or the local air authority may call an impaired air quality burn ban for areas smaller than a county, when and where feasible.