HomeMy WebLinkAbout20090396.tiffSTATE OF COLORADO
Bill Ritter, Jr., Governor
James B. Martin, Executive Director
Dedicated to protecting and improving the health and environment of the people of Colorado
4300 Cherry Creek Dr. S.
Denver, Colorado 80246-1530
Phone (303) 692-2000
TDD Line (303) 691-7700
Located in Glendale, Colorado
http://www.cdphe.state.co.us
January 19, 2009
Laboratory Services Division
8100 Lowry Blvd.
Denver, Colorado 80230-6928
(303) 692-3090
Board of County Commissioners, Weld County
915 Tenth Street
P. O. Box 758
Greeley CO 80632
Colorado Department
of Public Health
and Environment
Re: Meteorological and Mobile Source Information, 8 -Hour Ozone Non -Attainment Area
Dear Commissioners,
Following -up on my presentation to you on January 12, 2009 discussing Ozone Non -Attainment under
the federal Clean Air Act, as requested I am providing current meteorological data reflecting wind
direction and flow in Weld County. The attached "wind rose" reflects actual recorded wind direction
and speed data from the National Weather Service's Greeley meteorological station for afternoons
during the summer months, when ozone is of concern, over 5 years (June through August, 2002 - 2006,
noon to 7:00 p.m.). As reflected in these data, while wind directions vary there is frequently a wind
flow from the northeast, north and east across Weld County, which serves to flow into the Platte River
basin, and into and across the Ozone Non -Attainment Area. If you have questions about this
meteorological information, please let me know.
I also attach for your use a copy of the power point presentation that I spoke to when we discussed
Ozone Non -Attainment on January 12, 2009. I would like to clarify from my presentation that motor
vehicle emissions in Weld County are an important contributor to ozone precursor emissions, which
affect Weld County and also influence ozone in the Non -Attainment Area. In the attached power point
presentation, slide 15 - 2010 Apportionment Modeling Results, Greeley, 7/29/10 (87 ppb) reflects an
emissions apportionment graph from our modeling data indicating that motor vehicle emissions are the
second largest contributor of ozone precursor identified at the Weld County monitoring station on that
representative day. While oil and gas emissions are the largest emissions source noted on the
apportionment graph for this monitor on that representative day, those emissions will be significantly
reduced as a relative source of ozone precursor emissions based on the Air Quality Control
Commission's December 12, 2008 adoption of the Ozone State Implementation Plan, which approved
emissions reductions from a number of oil and gas sources that will go into effect starting in 2009. It is
also important to note that the Volatile Organic Compounds (VOCs) emitted from motor vehicles are
highly -reactive for ozone, meaning under the right conditions they quickly convert with nitrogen oxides
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2009-0396
(NOx) to form ozone, so they are very important air emissions to understand and address in the
management of ozone. Motor vehicles are also the largest source of VOC and NOx emissions in the
Non -Attainment area. If the state hopes to come into attainment with the new federal health based
standard for ozone (EPA, March 2008, 8 -Hour average of 0.075 parts per million (75 parts per billion)),
it will be critical to understand, address, and where necessary reduce and manage emissions from the
each of the major source categories, including motor vehicle emissions.
If I did not discuss this thoroughly when we spoke on January 12`h, I wanted to take a moment to clarify
these important points regarding vehicle emissions. I trust you find this information helpful. Please do
not hesitate to call me with any further questions at (303) 692-3113.
Sincerely;
Michael Silverstein, Deputy Director
Air Pollution Control Division
cc: Paul Tourangeau, Director
Air Pollution Control Division
Trevor Jirecek
Weld County Health Department
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