# SIERRA CLUB FOUNDED 1 892 September 17, 2015 Scott Mathias 1 \ sso ciate Director Air Quality Policy Division U.S. Environmental Protection Agency Research Triangle Park, NC 27711 Re: 

### Air Dispersion . Modeling of tvfissouri Sulfur Dioxide Pollution Dear Associate Director Mathias: Sierra Club urges the U.S. Environmental Protection Agency to designate the areas s urroundin g the Labadie and Sibley coal
- fired power plants as nonattainment under the s ulfur dioxide ("S O z") National Ambient 

### Air Quality Standard ("NAA QS") . Air dispersion modeling recently conducted b y Wingra Engineering, S.C. on behalf of Sierra Club demo nstrates that ambient air concentrations in both areas exceed the NAAQS, which is the maximum co ncentration of air pollution allowed to protect public hea lth. First, air dispersion modeling demonstrates that S0 2 emissions from the Labadie coal-fired power plant in Missouri have caused downwind S0 2 ambient air concentration s to exceed tl1e 196.2 micrograms per cubic meter NAAQS. In particular, tl1e modeling shows p ea k c oncentrations as high as 235 .7 micrograms per cubic meter. This is consistent wiili tl1e tvlissouri Department of Natural Re source s m o deling re sults, which found emissions from tlUs facility exceeded ilie NA.AQS. Accordingly, ilie U.S. Environmental Protectio n Agency s hould de signate tl1e area surrounding tl1e Labadie coal
- fired power plant as n onattainment und er the NA 1 \Q S . Eve n thoug h l\.f.issouri Department of Natural Resources' modeling f o und emis sions from ilie Labadie plant exceeded the NAAQ S, it pre sented anoilier option to nonattainmeot demonstration-unclassifiable. The agency suggested tlUs option because iliree month s of data from a monitor recently installed b y Ameren do not s how violations of the NAAQS. U.S . E PA s hould not consider tlUs a viable option becau se the monitor is not located at ilieLetter to Associate Director Mathias September 17, 2015 Page 2

area of peak concentration and because three years o f quality-assured monitoring data are required in order to determine whether an area complies with the 1
- hour S02 NAAQS. In addition, Ameren presented modeling to the Missouri Department of Natural Re so urces which purportedly showed no violations of the NAAQS. U.S. E P A sh ou l d no t rely on Ameren's modeling as it was able to «e ngineer'' these results because it modified tluee important inputs . Sierra Club submitted comments to the agency, with copies to EPA Region 7, about w hy an unclassifiable designation was inappropriate and about why Amercn's m o deling wa s deficient. Sec attac hed comment letters, which include copies of its modeling for the agency's consideration. Sierra Club intends to supplement its comments with a further critique of Ameren's Labadie modeling as there was not enough time to comprehensively review the modeling before the comment deadline. Sierra Clu b will copy EPA Region 7 and EPA's Office of Air Q u ality Planning and Standards on this comment s upplement . Second, air di spersion modeling demonstrates that S0 2 emission s from the Sib l ey coal
- fired power plant in : Missouri, along with other large sources of S0 2 that are located within 

## so kil ometers of the p lant, have caused downwind 

# so2 ambient air concentrations to exceed the NAAQS. In particular, the modeling shows peak concentratio n s as high as 43S.2 micrograms per cubic meter. The modeling results are consistent w ith the o nly monitor located in the modeled S02 plume . The 2012-14 de sign value measured at monitor #7290 9S0034 was 1 SO ppb or 392.4 micrograms per cubic meter. Based on actual hourly emissions from the S i bley plant and other regional sources, the modeling analys is predicted a concentration near the monitor location of 382.5 micrograms per cubic meter. Since the predicted and actual measured design values are in close agreement, this comparison s upp o rts the accuracy of Sierra C lub 's modeling .results . Therefore, the U.S. E nvironmental Protection Agency s hould also designate the area surrounding the Sibley coal
- fired power p lant as nonattainment under the NAAQS . Enclosed, please find the results of the modeling ana l yses, along with the corresponding modeling input and output file s and comments Sierra Club submitted to 1\f.isso uri Department of Natural Rcs o u.rc es . Sie .r.ra C lu b urges the U.S . Environmenta l Protection 1 \ gency to consider this inf or

mation as it undertakes area designations in l\lissouri for the 2010 r evised primary 

# so2 NAAQS . This information has already been pro vided to : Missouri Department of Natural Resources and is also being provided to EPA Region 7. In the meantime, please l et us know if we can provide any additional information.Letter to Associate Director**~vfathias** September 17, 2015 Page 3

Thank you for your attention to and consideration of this matter, and please do not hesitate to contact us if you would like to discuss further . Sincerely,

Kristin 

### A. Henry Sierra Club 85 Second Street, 2"d Floor San Francisco, CA 94105 415
-977
- 5716 kristin.hcnry @s ierraclub. o rg Sunil Bector Sierra Club 85 Second Street, 2"d Floor San Francisco, CA 94105 415
-977
- 5759**~u nil.bcctor** **@1~ em** **tclub. rg**  Maxine I. Lipeles Director, Interdisciplinary Environmental Clinic Senior Lecturer in Law Washington University School of Law One Brookings Drive
- Campus Box 1120 St. Louis, 'tviO 63130 314-935-5837 milipele@wu srl. ed u