Air Pollution Alert High Winds
Area of impact: Applies only in West Rapid City beginning at the Gap.
Meteorological Criteria: The following weather conditions need to exist for air pollution alert (dust in west Rapid City) to be called:
- Five consecutive days of 0.02 inches or less of precipitation each day excluding dry snow;
- The forecasted peak wind gust needs to be greater than 40 mph; and
- The forecasted average hourly wind speed needs to be greater than 20 mph.
The air pollution alert will be discontinued when the following weather conditions exist:
- Wind speeds decrease below 12 mph on an hourly average and peak wind gusts are below 30 mph; or
- There is greater than 0.02 inches of precipitation in a 24-hour period excluding dry snow.
Air Pollution Alert issuance: This alert will be issued and discontinued by the National Weather Service. The most recent air pollution alert can be viewed at the National Weather Service website. The National Weather Service will contact the Department of Environment and Natural Resources. The first Department of Environment and Natural Resources contact will be Brad Schultz in Pierre at (605) 773-3151 then Jon Epp in Rapid City at (605) 394-2229. The Rapid City Air Quality staff in Rapid City at (605) 394-4120 will be contacted next if no one is available at the Department of Environment and Natural Resources. The Department of Environment and Natural Resources will contact the industry sources to limit activities during the air pollution alert.
Precautions: The following precautions should be taken during any of these situations. Elderly citizens, young children and individuals with respiratory problems should avoid excessive physical exertion and minimize outdoor activities. Although these people are most the susceptible to health impacts, it is recommended that everyone take precautions to avoid being exposed to these poor air quality conditions.
Voluntary actions to reduce air pollution levels: To minimize pollution levels, it is recommended that any manipulation of soils, such as construction, or industrial or agricultural activity, cease or be minimized during these events. It is also recommended that pollution controls for soil stabilization, process equipment, waste pits, stockpiles and construction sites, such as watering or chemical treatment, be increased.
Basis for criteria selection: High wind/dust conditions typically occur after extended dry periods during the colder months of the year and have on occasion caused air pollution problems during warmer months. Therefore, dust pollution advisories will be called year round. High air pollution levels occur when peak wind gusts reach 40 to 70 miles per hour and average hourly wind speeds are greater than 20 miles per hour for an extended period of time. The high winds strip away the top crusted layer of the soil and suspend the finer dust particles in the air. The high wind events can last from one to eight hours depending on the strength of the storm system.
During these events, the hourly dust concentrations have ranged from 100 micrograms per cubic meter to 900 micrograms per cubic meter per hour. A violation of the dust health standard is a reading over 150 micrograms per cubic meter averaged over a 24-hour period. This standard has been violated during these conditions in West Rapid City. Therefore, an air pollution alert for dust will only be called for the West Rapid City area. A review of monitoring data indicates that high concentrations only occur in this area of town during these high wind events.
Past Air Quality Alerts: Monitoring data from high wind alerts issued during the last year can be viewed at the Department of Environment and Natural Resources website.