**nrg**

-:- December

1, 2015 Certified Mail: Return Receipt Requested Ms. Janet G. McCabe Assistant Administrator, Office of Air and Radiation U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, NW Washington,
DC 20760 Re: NRG Texas Power LLC Supplemental Reports

NRG Texas Power LLC 1000 Main Houston

,Tx 77002 Demonstrations

of 1-Hour S02 NAAQS Attainment Status Limestone and W.A. Parish Power Plants Dear Ms. McCabe: NRG Texas Power LLC ("NRG Texas") respectfully offers the attached supplemental reports for the Limestone and W.A. Parish facilities regarding United States Environmental Protection Agency (EPA) proposed actions onthe 1-hour S0 2 National Ambient Air Quality Standard (NAAQS)

in Texas. NRG Texas
is a subsidiary
of NRG Energy, Inc.,
aFortune 250 Company and oneof the country's largest power generation and retail electricity bus

i nesses

.NRG Energy's power plants prov

i de about 52

,000 megawatts
of generation capacity and its retail businesses servemorethan
3 million customers throughout the country. In Southeast Texas, NRG Texas ownsmorethan 11,000 MW of generation capacity from nine electric generating stations

.NRG supportsclean energyresourcesand technologies critical toourtransiti on to a sustainabl e,low carbon society. We believe that the areas surrounding the Limestone and Parish plants should be designated attainment
orunclassified/attainment

for the 1-hour S0 2 NAAQS, which
is consistent with EPA's updated designations guidance for S0 2dated March 20, 2015, which states that In the absence of information that clearly shows attainment

or nonattainment,
the EPA intends
to designate
anarea unclassifiable/attainment. Monitoring data is necessaryfor accurate characterization of actual air quality for attainment and nonattainment designations.
We notethat all regulatory-quality
S02 monitoring data in Texas currently reflects attainment
of the NAAQS, and thus available monitor-based evidence supports attainment
or unclass

i fiable/designations. As atechnical supplement

tothe S0 2 dispersion modeling analyses provided toEPA on September 17, 2015, weare providing the attached reports. These modeling results and supplemental reports provide further confirmation that, based on representative actual emissions and stack conditions, the emissions from NRG's -1-Limestone and Parish plants cannot reasonably

be anticipated

to causeor contribute
to nonattainment
for the S02 NAAQS. These demonstrations have been made in amannerconsistent with EPA and Texas Commission
onEnvironmental Quality (TCEQ) air quality regulations and modeling guidelines, and in accordance with EPA's S02 NAAQS Designations Modeling Technical Assistance Document (Draft)," December 2013. NRG appreciates yourconsideration

of this information. Please contact meat 832-357-5291

or craig.eckberg@nrg

.comif youhave any questions
or require additional information. Sincerely,

)

, /)
()u **(/\~?sc- ~**  Craig Eckberg Director, Environmental Services NRG Energy, Inc Attachments(2) Cc: Steve Hagle, TCEQ Guy Donaldson, EPA R6 -2-Attachments A. Supplemental S02 Air Dispersion Modeling Report for W.A. Parish Generating Station (November, 2015) ("Parish Report"). B. Supplemental S02 Air Dispersion Modeling Report for Limestone Generating Station (November, 2015) ("Limestone Report"). -3-