# SIERRA CLUB I · 0 U N lH D I 8 92 September 17, 2015 Sco tt Mathias Associate Dir ector Air Quality Policy Di,,is ion U.S . Enviro nmental Protection 1 \gency Re se arch Triangle Park , C 277 1 1 Re: Air Dis persi o n Modeling of Ohio Sulfur Dioxide P ollution Dear Associate Director Mathias, S i

erra Club urges the U.S . Environmental Pro tection Age nc y to de s i gnate the areas s urrounding the Gavin and Zimme r coal

- fired p owe r plants as nonattainment under rhe sulfur dioxide ("S O t) ational Ambie nt Air Qualit y Sta ndard ("NA.AQS") . 

### Air dispe rs ion modeling recendy conducted by Wingra Engineering, S.C. o n behalf of Sierra Club demo nstrates that ambient air concentrations in these areas exceed d1e N , \t\ Q , whic h is d1e maxin1um conce ntratio n of air pollution allowed to protect public health. First, air disper s ion modeling demo n strates that S0 2 emissions from the Gavin coal-fired power p l ant in Ohio have caused downwind S0 2 amb ient air concentration s to exceed the 196.2 micrograms per cubic meter AAQS. In particular, the modeling of actual emissions from this facility alone s how s peak conce ntrati ons as hi g h as 291.5 micrograms pe r cubic meter. \%en the actua l emiss ions from othe r large so urces of S0 2 d1at arc located ,vidun 50 kil o meters of the Gavin power plant arc included, the peak concentrati o n is as high as 318.5 microg rams per cubic meter. Accordingly, d1e U.S . E nvironmental Protection r\genc y s hould designate the area surro undin g the Gav in coal

- fired power plant as nonattainment under the NAAQS. Second, air di s pers ion modeling demon stra te s that S0 2 emissions from the Zin1mer coal

fired power plant, along \Vid1 actua l CnUSSion S from o ther large $02 SO urCC S that are widUn 50 kilometers of dle plant , ha, ·c caused downwind 

# so 2 ambient air concentrations to exceed the AAQS . Specifically, d1 e modeling shows cumulative peak concentration s for the Zi mmer power plant as high as 519.2 microgra ms per cubic meter. T he U . S . Environmental Pro tection AgencyLetter to Assoc i ate Director

**Iathia s**  September 1 7, 20 1 5 Page 2 sho uld dms des ignat e the areas s urroundin g th e Z immer coal-fired pow e r plant s a s nonattainment under the NAAQS . E ncl ose d , please find d 1e r esults of the m o de ling analrses, along wit h d1e co rrespon ding modeling input and output files . S i

e rra Club urges the U.S. Environmental Protection Age nc y to consider this information as it und e rtake s area d es i gnations 

### in Indi ana for the 20 10 r evi se d prima ry S0 2 NAAQS . This inf or mation is b e in g provid ed to both EPA Regi o n 

### 5 and to appropriate p e rso nnel at the Ohio E nvironme n tal Protectio n .Age nc y. In the mean tim e, pl ease let u s kn ow if we ca n provi de any additio nal information. Thank yo u for yo ur atte ntio n to and co n s i de ration of 

### this matte r, and please d o n ot hesitate to contac t us i f yo u wou ld like to di sc u ss fur th e r. Sinc e rely,

Kristin A . H e nry Sierra Club 85 Seco nd Street, 2"d Floo r Sa n Francisco, 

### CA 94105 415

- 9 77-57 16 kristin.henry@sicrrncluh.c>rg Tony Mendoza Sierra C lub 85 Sec on d Street, 2"d Floor San Fran ci s co, CA 941 OS 415-977-5589 to ll ) ' .menc.loza (g{s icrra c l u b.org