Pinal County Air Quality April 3, 2009 PM 10 Natural/Exceptional Event

April 3, 2009 Strong cold front moved into the area. Winds associated with the front transported dust into Pinal County. The Maximum winds reached 40 mph and three PCAQCD monitors exceeded the 24-hr PM 10 NAAQS. Site24-hr PM 10 Conc. (ug/m 3 ) –PCH (TEOM)381.0 –Stanfield (TEOM)209.9 –Cowtown (TEOM)199.4

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Gusty winds, blowing dust close I-40 near Flagstaff by Drew Engelbart - Apr. 3, :51 AM The Arizona Republic Strong winds, reaching up to 50 mph or more, are expected throughout Arizona on Friday, and have caused an Interstate to close. The strong winds and blowing dust has caused low visibility and forced the closure of a 41-mile stretch of Interstate 40, according to the Arizona Department of Transportation. It is closed between Winona, which is just east of Flagstaff, and Winslow. The Transportation Department says the interstate is being closed as a precaution and there were no reports of collisions. No timetable has been set for the reopening of I-40, and drivers are advised to avoid the area. Visibility is expected to worsen, as they are anticipating stronger winds in the afternoon. Most of the state will be experiencing either a wind advisory or high wind warning throughout the day, according to the National Weather Service. A wind advisory will be in effect in the Phoenix area from 1 p m. to 10 p.m., with wind gusts expected to reach 50 mph. A high wind warning is in effect in the northern part of the state until midnight, with the possibility of 60 mph winds. The high winds are not expected to be as strong as the destructive storm the Valley experienced last week, NWS meteorologist Paul Iniguez said. Temperatures and wind speeds should drop on Saturday with highs in the low 70s. Sunday is expected to be a little warmer with highs in the upper 70s. It is expected to warm back up by next week with temperatures reaching the mid 80s.

4/3/09 “But for” Test PCH (TEOM) had the following 24-hr PM 10 concentrations before/after the 4/3/09 natural/exceptional event –4/2/09 – 66.1 ug/m 3 –4/4/09 – 51.2 ug/m 3 Stanfield (TEOM) –4/2/09 – 57.7 ug/m 3 –4/4/09 – 57.1 ug/m 3 Cowtown (TEOM) –4/2/09 – 71.1 ug/m 3 –4/4/09 – 95.5 ug/m 3