More ‘ozone outlooks’ posted

A potential

for high hourly ozone levels is predicted

again in the Upper Green River Basin from

Thursday on through to Tuesday, March 19.

Wednesday, the Wyoming Department

of Environmental Quality had changed its

usual “green” for good air-quality status to

yellow for “moderate” at the Daniel South

and Juel Spring sites, on the verge of being

“unhealthy for sensitive groups.”

At that time on the DEQ’s Air Quality

Division home page for www.wyvisnet.

com, the Daniel South site registered 55

parts of ozone per billion for the previous

eight hours. Juel Spring’s eight-hour average

was 57 ppb. The federal ozone standard

for good air quality is 70 ppb for an eighthour


On Thursday, the Daniel and

Juel Spring sites were again colored


Boulder, where most of this winter

ozone season’s high hourly levels have

exceeded the national standard, the previous

day’s eight-hour average was 54

ppb for the previous eight hours.

The AQD had issued an “ozone action

day” notice for Tuesday, March

12, after several days of rising groundlevel

ozone measurements.

On an “ozone action day,” the energy

industry and public put into place

contingency plans to reduce groundlevel

emissions that form the pollutant.

Since mid February, the AQD has issued

alerts for potentially high hourly

levels of ozone.

The “winter ozone season” is observed

from January through March

when winter conditions include high

amounts of snow cover, bright sunlight,

temperature inversions, volatile

organic compounds and nitrogen oxides.

Earlier on Sunday, March 10, the

AQD had not forecasted high levels –

but Boulder’s hourly ozone spiked to

just below 120 ppb and the eight-hour

average to 90 ppb – the highest in the

Upper Green River Basin this winter.

Tuesday brought higher numbers at

Big Piney, almost 65 ppb for hourly

and 58 ppb for its high eight-hour levels.

Daniel South, where eight-hour

levels have rolled between 45 and 55

ppb the past week, also had its highest

hourly numbers for this winter on

Tuesday, just over 65 ppb. As of Thursday,

eight-hour levels topped at 75 ppb

and showed a downward trend.

Juel Spring’s data show information

gaps for Sunday, Monday and Tuesday

and on Wednesday started the day at

65 ppb, rose slightly and then declined.

The Pinedale station’s highest

hourly ozone levels for this week measured

below 65 ppb and levels declined


The ozone contingency plans are

voluntary and are observed to reduce

the ozone precursors of volatile organic

compounds and nitrogen oxides.

Current information on ozone levels

at AQD monitoring stations at Boulder,

Pinedale, Daniel South, Big Piney and

Juel Spring is at

To see previous 1-hour and 8-hour levels

at any site, plot “recent data” for the

appropriate time period.

More on ozone and its health effects

are at and

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