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
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 www.wyvisnet.com.
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 http://deq.wyoming.gov/aqd/ and