U.S. Environmental Protection Agency 

EPA Docket Center 

Docket: EPA-HQ-OAR-2014-0464 

Mail Code 28221 T 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

RE: Docket ID No. EPA-HQ-OAR-2014-0464 

FILED VIA EMAIL AND U.S. MAIL 

Cleco Corporation- Do let Hills Power Station (DeSoto Parish) 

Comments to EPA Recommendation for S02 NAAQS Designation 

LDEQ Agency Interest No. 585 

Dear Sir or Madam: 

These comments and the attached supplemental modeling and monitoring reports are 

submitted by Cleco Corporation ("Cleco") on behalf of the Do let Hills Power Station located in 

DeSoto Parish, Louisiana. Cleco requests that these comments be included in the administrative 

record for this docket and that these comments be considered by the U.S. Environmental 

Protection Agency ("EPA") when making a final designation related to the 1-hour sulfur dioxide 

("S02") national ambient air quality standard ("NAAQS") for DeSoto Parish. 

As discussed below, Cleco believes EPA should accept the Louisiana Department of 

Environmental Quality's ("LDEQ's") recommendation to designate DeSoto Parish as 

"attainment" for the 1-hour S02 NAAQS. Based on air quality modeling conducted by American 

Electric Power (AEP) and monitoring data derived from a properly-sited air monitor located in 

DeSoto Parish, there is substantial evidence to accept LDEQ's attainment recommendation for 

this area. If EPA does not accept LDEQ's recommendation, a designation of 

"unclassifiable/attainment" is more appropriate for DeSoto Parish than the designation recently 

proposed by EPA. 

Background 

On March 1, 2016, EPA published a "notice of availability and public comment period" 

in the Federal Register for certain state designation recommendations for the 2010 1-hour S02 

NAAQS. See, 81 Fed. Reg. 10,563. This notice relates to a second round of S02 NAAQS 

designations for certain areas of the country as required by a consent decree that included a 

court-ordered designation schedule. Sierra Club v. McCarthy, No. 3-13-cv-3953 (SI) (N.D. Cal. 

Mar. 2, 2015). In response to the above-referenced consent decree, EPA notified the state of 
In response to EPA

s notice letter, the LDEQ submitted a report to EPA Region 6 on 

September 18, 2015 that provided recommendations for designation of the S02 NAAQS for 

Calcasieu and DeSoto Parishes. The LDEQ also submitted a revised recommendation to EPA 

specifically for DeSoto Parish in correspondence dated November 17, 2015. In this letter, the 

LDEQ recommended that DeSoto Parish be designated as "attainment" for the 1-hour S02 

NAAQS. The Sierra Club also provided comments to the LDEQ on September 18, 2015 that 

included air modeling for DeSoto Parish and submitted updated air modeling to the EPA Air 

Quality Policy Division in correspondence dated December 14, 2015 for areas in Texas and 

Louisiana, including DeSoto Parish. 

In response to LDEQ's recommendation, EPA Region 6 provided a notification to the 

state of Louisiana of its intended modifications to the state's proposed recommendations in 

correspondence, dated February 11, 2016 (also known as the "120-day letter"). With respect to 

DeSoto Parish, EPA notified the state that it intended to designate a part of the parish as 

"nonattainment" for the S02 NAAQS, and thereby, did not accept the state's recommendation. 

EPA's 120-day letter attached a Technical Support Document, which included a 

Technical Analysis for the DeSoto Parish, Louisiana Area ("Technical Analysis for DeSoto"). 

See, Letter from Ron Curry to Gov. John Bel Edwards, dated Feb. 11, 2016, pp. 6-19. As 

discussed in the Technical Analysis for DeSoto, EPA proposes to designate a rectangular area in 

DeSoto Parish (shown on Figure 1 (p. 8) of the document) that would include the Dolet Hills 

Power Station and International Paper's Mansfield Mill. 

Specific Comments to EPA 120-Day Letter Related to DeSoto Parish 

Cleco provides the following specific comments in response to EPA's letter from Ron 

Curry to Gov. John Bel Edwards, dated February 11, 2016. Cleco believes these comments and 

the attached modeling and monitoring analyses justify a different designation for the DeSoto 

Parish area than what was proposed by EPA in its 120-day letter. Cleco requests that the EPA 

provide a detailed, written response to each of the following comments. 

1. Supplemental air modeling conducted by AEP demonstrates that S02 emissions from the 

Dolet Hills Power Station and the paper mill are below the 1-hour S02 NAAQS. This 

modeling is more accurate than prior modeling analyses conducted by the Sierra Club 

and the LDEQ and responds to specific issues raised by EPA in its technical analysis. 

In response to EPA's 120-day letter, Cleco worked with the co-owner of the Dolet Hills 

Power Station, AEP, to conduct additional air modeling for the DeSoto Parish area that included 

more accurate emissions data and stack parameters for the coal-fired electric utility and also 

included the paper mill located approximately 14 kilometers north of the utility. Unlike the 
February 2016, and comments made by EPA in the Technical Support Document attached to the 

120-day letter. 

With respect to the emissions modeling parameter, EPA noted in the 120-day letter that 

"continuous emissions monitoring systems (CEMS) data provide acceptable historical emissions 

information when it is available, and that these data are available for many electric generating 

units." Id. at p. 12. EPA further noted in its technical analysis that LDEQ used "normalized 

hourly emissions and actual stack temperature and exit velocity from the CEMS for 2012-2014" 

and that Sierra Club's modeling used "hourly emissions data measured by the CEMS from 

CAMD (2012-2014) and constant stack temperature and exit velocity." Id. at p. 12. Concerning 

the source characterization modeling parameter, EPA stated: 

Sierra Club modeled constant exit flowrate and temperature based on 100% load. 

No consideration was given of facility operation at less than 100% load. Stack 

parameters such as exit flow rate and temperature are typically lower than full 

load, having the effect of reducing pollutant dispersion and increasing predicted 

air quality impacts. In addition, no consideration was given to building or 

structure downwash. Downwash effects typically increase predicted 

concentrations near the facility. The state identified International Paper located 14 

km north of the Dolet Hills facility with annual emissions exceeding 1,300 tpy as 

the only other large nearby emission source. However, no sources other than 

Dolet Hills were included in the modeling performed by the Sierra Club or the 

state. 

Id. at p. 11 (Emphasis added). 

In its supplemental modeling analysis, AEP included more accurate information for three 

specific categories: (1) stack parameters, (2) emissions data, and (3) effects of downwash. With 

respect to stack parameters, AEP reviewed the flat stack exit temperature and exit velocity used 

by Sierra Club and concluded that these were arbitrarily low. Data collected by AEP reveals 

temperatures above 200°F and an exit velocity greater than 90 ft/sec at the low-end of full load 

operating conditions. In contrast, Sierra Club used a temperature of 161 °F and an exit velocity of 

about 85ft/sec. With respect to emissions data, AEP used CEMS data for the Dolet Hills Power 

Station including, heat input (MMBtu/hr) data, flowrate (scfh), and hourly S02 emissions data 

(lb/hr) that was reported to the USEPA Clean Air Markets Division ("CAMD"). In addition to 

these parameters, the temperature data collected by the CEMS (but not reported to CAMD based 

on the 40 CFR Part 75 reporting protocols developed by CAMD) was used to adjust the flow 

data back into actual flow units and the hourly temperature input required by AERMOD. The 

data was processed on a parameter basis in which flowrate was adjusted back to actual hourly 

stack conditions using the temperature data for concurrent hour for which the exit velocity was 
including a proper downwash analysis will increase the predicted impacts. See, Dolet Hills 

Power Station report, dated August 9, 2015, p. 4. Based on AEP's review, this statement is 

generally not correct for emission sources like the Dolet Hills Power Station with a stack that is 

significantly taller than surrounding structures. For this reason, AEP included proper downwash 

in its air quality model and estimated emissions based on actual operating data, which better 

reflects the dispersion of S02 emissions in a given hour. Startup conditions were also reflected in 

the inventory used by AEP based on available information. 

The ambient air modeling report prepared by AEP, entitled Air Quality Modeling 

Technical Note, Dolet Hills Power Station, Mansfield, Louisiana, is attached to these comments 

in Attachment 1. The modeling files have also been provided to EPA Region 6 personnel for 

further review and examination. The final refined modeling simulation shows that the highest 

concentration due to all sources and the background concentration is 171.0 f.!g/m3, which is 

below the 1-hour S02 NAAQS of 196.5 flg/m3. As discussed in Comment 3 below, a seasonal 

hourly background concentration ranging from 4.88 flg/m3 to 24.85 f.!g/m3 was used for this 

analysis. However, the AEP modeling still demonstrates compliance with the 1-hour S02 

NAAQS if the higher background concentration used by Sierra Club and LDEQ (31.4 f.!g/m3) is 

used. 

Cleco believes that EPA should use the attached modeling report in lieu of prior reports 

submitted by Sierra Club and the LDEQ. As discussed, the AEP modeling analysis used more 

accurate information for stack parameters and emissions data for the Dolet Hills Power Station as 

well as the effects of down wash, and included emissions of the paper mill. Cleco further asserts 

that based on this modeling information alone, EPA should classify DeSoto Parish as 

"attainment" in the final S02 NAAQS designation. As discussed below, this modeling result 

comports much closer to the monitoring data that has been attained for this area in recent 

months. 

2. Emissions from International Paper's Mansfield Mill do not contribute to concentration 

gradients around the Do let Hills Power Station or to the south of this facility as asserted 

in EPA's 120-day letter. Because such emissions have now been adequately considered 

in AEP's modeling analysis, an attainment designation is appropriate. 

The Technical Analysis for DeSoto discussed the fact that neither Sierra Club nor the 

state's modeling included emissions from International Paper's Mansfield Mill. EPA further 

speculated that "when winds are out of the north and resulting in some of the highest values 

modeled around Dolet Hills, the IP source would be upwind and could contribute to 

concentration gradients around Dolet Hills and to the south ofDolet Hills." !d. at p. 10. Based on 

this observation and the proximity between the Dolet Hills Power Station and the Mansfield Mill 

( ~ 14 kilometers), EPA concluded that "it is likely that the source causes concentration gradients 
such that if they were explicitly modeled in accordance with the Modeling TAD 

would likely be shown to contribute to the ambient concentrations that have 

already been modeled to show violations, or near violation, of the NAAQS. 

Inclusion of IP emissions may likely increase modeled values just below the 

standard to exceedance levels. Therefore, our intended area includes portions of 

DeSoto Parish that include the area of modeled exceedances and near 

exceedances as well as the IP facility because of its likely contribution to the 

modeled ambient concentrations resulting in additional potential NAAQS 

violations if IP were included in the modeling. 

The EPA believes that our intended nonattainment area, consisting of the area 

around Dolet Hills and including Cleco, is comprised of clearly defined 

boundaries, and we find these boundaries to be a suitably clear basis for defining 

our intended nonattainment area. 

Id at p. 18 (Emphasis added). As discussed in the prior section, the air modeling performed by 

AEP included the utility and the paper mill, and confirms compliance with the 1-hour S02 

NAAQS. AEP's modeling further reveals that S02 emissions from the Mansfield Mill do not 

contribute to the concentration gradients near the Dolet Hills facility or to the south of the 

facility. 

With respect to modeled emissions for the paper mill, the analysis used a conservative 

representative estimate for the maximum hourly S02 emissions rate for Power Boilers No. 1 and 

2. These rates were developed from a statistical evaluation of the hourly S02 CEMS data 

(lb/MMBtu) for the period 2012-2014. The .factors were then multiplied by the maximum heat 

input of each boiler to obtain the maximum actual S02 emissions rates. All other S02 emissions 

sources were modeled using the maximum permitted emission rates. As noted in the report, 

atypical operating scenarios were excluded from the modeling analysis since they are not 

representativeness of typical mill operation and are not expected . to coincide with the other 

·conservative modeling inputs. To address EPA's comment related to assumptions made in the 

LDEQ and Sierra Club modeling, hourly exit flowrate/velocity data was developed in the refmed 

modeling analysis. 

As discussed, the refined modeling analysis shows that the highest concentration due to 

both sources plus monitored background is below the 1-hour S02 NAAQS. In addition, the 

contribution of emissions sources at the Mansfield Mill to the total modeled concentration is 

extremely low (approximately 0.4 11g/m3). This refutes any supposition in EPA's 120-day letter 

that the Mansfield Mill "could contribute to concentration gradients around Dolet Hills and to the 

south of Dolet Hills" in any meaningful way. Instead, the refined modeling shows that the 

highest concentrations associated with the Mansfield Mill sources are at the facility boundary 
classify all of DeSoto Parish as 

attainment

 in the final S02 NAAQS designation. 

3. A more representative background concentration should be used for the DeSoto Parish 

area modeling analyses than what was used by the Sierra Club or LDEQ. 

Ambient air quality data is typically used · to represent the contribution of non-modeled 

sources to the total ambient air pollutant concentrations for a NAAQS analysis. With respect to 

background concentration, EPA's Technical Analysis for DeSoto references that 31.4 d llg/m3 

was used by the LDEQ and Sierra Club in their respective modeling analyses. This was 

purportedly based on the "99th percentile of the annual distribution of daily maximum 1-hour 

concentrations averaged across 2011-2013 for the Bossier Parish monitor -the lowest measured 

background concentration in the state." Id. at p. 14. Thus, the Sierra Club and LDEQ analysis 

used monitored data from a monitor located in Shreveport, Louisiana approximately 54 

kilometers north of the Do let Hill Power Station. 

Although EPA states in the TAD that the Shreveport monitor has ."the lowest measured 

background concentration in the state," this monitor is the most representative monitor available 

for any modeling analysis and likely conservative. The Mansfield Mill and Dolet Hills facilities 

are surrounded by rural land use generally consisting of agricultural and undeveloped forested 

and grassland areas, whereas the Shreveport monitor is in a more urban/developed area 

consisting of commercial and compact residential land uses. A wind rose of the Shreveport 

meteorological data indicates winds in the region are predominantly from the south. Thus, S02 

are likely transported from both the power station and th~ paper mill toward the Shreveport 

monitor. Therefore the use of this monitor may result in some double counting of emissions in 

the analysis. For these reasons, the Shreveport monitor should be conservative to represent 

background in the vicinity of the Mansfield Mill and Do let Hills. 

EPA's recommends a tiered approach for adding monitored background concentrations 

(representing non-modeled sources) in the NAAQS analysis. As noted in the Technical Analysis 

for DeSoto, the first tier approach is conservatively based on adding the monitored design value 

(3-year average 99th percentile daily 1-hour maximum concentration) to the modeled design 

value. The second tier uses a temporally varying approach, based on combining the monitored 

concentrations, by hour of day and season, with the hourly modeling results. The total hourly 

modeled plus monitored concentrations are then used to determine the design concentration for 

comparison to the NAAQS. These computations are all done within AERMOD. 

Rather than conservatively adding the modeled design concentration with the monitored 

design concentration for this analysis, the second tier refinement should be used. Under this 

approach, the ambient background concentration should be combined with modeled 

concentrations on a seasonal hour-of-day basis in accordance with EPA guidance as outlined in 
Based on the foregoing, Cleco believes EPA should accept the seasonal hourly 

background concentrations developed by AECOM/Intemational Paper ranging from 4.88 IJ.g/m3 

to 24.85 IJ.g/m3 based on 2013-2015 data for the Shreveport monitor. This background 

concentration is based on an actual three years of data (not an extrapolation of one year) and a 

more recent period. As discussed in Comment 1 above, the AEP modeling still demonstrates 

compliance with the 1-hour S02 NAAQS ifthe higher background concentration used by Sierra 

Club and LDEQ (31.4 IJ.g/m3) is used. Nevertheless, the use of the lower background 

concentration is justified in this instance. 

4. EPA accepted similar air modeling in Arkansas that used better site data and more closely 

adhered to EPA's technical assistance document. For consistency, EPA should also 

accept the attached modeling report that demonstrates attainment with the S02 NAAQS. 

In the February 11, 2016 notification by EPA to the Governor of Arkansas of its 

designation intention for Jefferson County, Arkansas, a Technical Assistance Document (TAD) 

was included which discussed the reasoning behind EPA's intention. This discussion mainly 

focused on the White Bluff Steam Electric Station ("White Bluff') and the dispersion modeling 

of the plant by both the Arkansas Department of Environmental Quality ("ADEQ") and Sierra 

Club. EPA wrote in the paragraph titled Other. Relevant Information (page 18 ofthe TAD) that it 

had identified multiple errors in stack parameters, as well as less-refined modeling approaches as 

compared with the state's submittal (e.g., variable stack velocity and temperature were not 

included). With respect to the less-refined modeling approaches, EPA stated: 

Sierra Club also did not include the additional refinement of variable stack 

parameters, as allowed by the modeling TAD, and was not as representative of 

daily operations when compared with the state's analysis. The state's modeling 

was determined to follow the modeling TAD more closely, and is more 

representative of actual operation conditions at White Bluff station. Therefore, our 

intended unclassifiable/attainment designation for Jefferson County is based on 

the state's analysis. 

Letter from Ron Curry to Gov. Asa Hutchinson, attaching Technical Analysis for Jefferson 

County Arkansas Area, dated Feb. 11, 2016, p. 18. 

Similar to the modeling conducted by ADEQ, the AEP modeling analysis for Desoto 

Parish used variable stack parameters as allowed by EPA's modeling TAD. Sierra Club's 

modeling of Desoto Parish, like its modeling of Jefferson County, Arkansas, did not use variable 

stack parameters and, therefore, is not as representative of daily operations as AEP's modeling. 

Therefore, as it did in Arkansas, EPA should base its designation of Desoto Parish on the 
that the 1-hour S02 NAAQS has been satisfied for a representative period. At a 

minimum, the monitoring data demonstrates that not enough data exists to classify the 

area as nonattainment. 

On July 8, 2015, representatives of Cleco, EPA and the LDEQ met to discuss issues 

related to the S02 NAAQS designation for DeSoto Parish, including the installation of a S02 

ambient air monitoring system to characterize the quality of the ambient air near the Do let Hills 

Power Station. On August 19, 2015, Cleco submitted a report to the LDEQ and EPA entitled, 

Siting for Source-Specific S02 Ambient Monitoring for Dolet Hills Power Station." Cleco's 

consultant used a "normalized design value" (NDV) approach to determine an acceptable SOz 

monitoring location based on EPA's guidance document entitled, S02 NAA QS Designations 

Source-Oriented Monitoring Technical Assistance Document, dated December 2013. 

Cleco subsequently installed a S02 ambient air monitoring system based on the results of 

the siting analysis prepared by CB&I. The LDEQ referenced the use of data from the ambient air 

monitor in its S02 NAAQS recommendation letter to EPA, dated September 18,2015, and noted 

that the "data provided by the new monitoring station will allow for an accurate characterization 

of air quality nearest the source of S02 without ambiguity." See, p. 3 of DeSoto Support 

Document attached to LDEQ letter to EPA. Representatives of LDEQ have reviewed the data 

collection and processing for this ambient air monitor since installation. 

CB&I submitted a S02 Ambient Monitoring Quarterly Report to the LDEQ on February 

26, 2016 that provided monitoring data from October 23, 2015 through January 31, 2016. Thus, 

the statement by EPA on page 8 of the technical analysis that "there are no S02 air quality 

monitors in DeSoto Parish" is not accurate. All data collected for this period demonstrates 

compliance with the 1-hour S02 NAAQS. The report dated February 26, 2016 noted that the 

highest daily maximum one-hour concentration from October 23, 2015 through January 31, 2016 

was 32.6 parts per billion (ppb). The average daily maximum 1-hour concentration for this 

period was only 3.5 ppb and the 99th percentile daily maximum 1-hour concentration was 25.6 

ppb. The ambient air monitoring report prepared by CB&I are attached to these comments in 

Attachment 2. 

The above monitoring data, based on an ambient air monitoring station (properly sited 

using EPA's source-oriented monitoring technical assistance document) demonstrates that actual 

S02 concentrations are well below the 1-hour S02 NAAQS. This information further supports 

the modeling analysis prepared by AEP that shows the design value to be below the standard. 

Cleco believes that the use of both sets of data justify an "attainment" designation. At a 

minimum, Cleco believes the S02 monitoring ·data for this representative period justifies a 

designation of "unclassifiable/attainment." EPA should not make a premature and unwarranted 
not yet been identified to support an attainment or nonattainment designation.

 See, 80 Fed. Reg. 

51,084. In this case, we believe there is sufficient information for EPA to make a fmal 

designation of "attainment" or "unclassifiable/attainment." Likewise, in light of conflicting 

modeling reports, there is not enough information for EPA to make a definitive determination 

that any part of DeSoto is not attaining the standard. EPA is clearly authorized to consider this 

monitoring data and should do so in this case: (1) because it was properly located using EPA 

guidance documents, (2) because it demonstrates monitored attainment with the S02 NAAQS, 

and (3) because it substantiates AEP's modeling analysis which also confirms compliance with 

the standard. 

6. Based on the available information, EPA should allow more time to evaluate the 

monitoring data before designating any part of DeSoto Parish as nonattainment. 

Sufficient data does not exist to make a conclusion that the DeSoto Parish area is not 

meeting the 1-hour S02 NAAQS. 

With respect to NAAQS, the federal Clean Air Act defines an area as "nonattainment" as 

"any areas that does not meet (or that contributes to ambient air quality in a nearby area that does 

not meet) that national primary or secondary ambient air quality standard for the pollutant." See, 

42 U.S.C.§ 7501(2) and 42 U.S.C.§ 7407(d)(l). Implicit in this statutory definition is the criteria 

that . enough significant data exists (in the case of the 1-hour S02 NAAQS through either 

monitoring or modeling) for EPA to conclude that an ambient air quality standard has been or is 

being violated in a particular geographic area. With respect to DeSoto Parish, Cleco believes that 

EPA has not presented enough data in the 120-day letter to designate any portion of the parish as 

nonattainment. Rather, this data more properly leads to a designation of "unclassifiable" if 

LDEQ's air modeling analysis is disregarded by EPA. 

However, based on the AEP modeling results that use significantly more accurate 

emissions and source parameter data for the Do let Hills Power Station and International Paper's 

Mansfield Mill, enough data exists to designate DeSoto Parish as "attainment," which is defined 

in the federal Clean Air Act as "any area . . . that meets the national primary or secondary 

ambient air quality standard for the pollutant." Id. This higher-quality modeling analysis is 

further supported by recent ambient monitoring data that confirms that the anticipated highestmodeled area near the Dolet Hills facility is well within the 1-hour S02 NAAQS. EPA clearly 

has the authority to consider this data (hence, the non-mandatory solicitation for public 

comments by EPA in the March 1, 2016 Federal Register notice) before a final designation is 

made. Based on this clear and overwhelming information, Cleco urges the EPA to designate 

DeSoto Parish as attainment by July 2, 2016. At a minimum, the data justifies a recommendation 

of "unclassifiable/attainment" for this geographic region. 
major S02 sources located in this region meets the 1-hour S02 NAAQS. This conclusion is 

further supported by data from the properly-located ambient air monitoring station currently 

operating in DeSoto Parish. 

We appreciate your review of these comments and look forward to EPA's written 

response. If you have any questions, I can be reached at (318)484-7718. 

Respectfully submitted, 

Bill Matthews 

Director---: Environmental Policy and Planning 

Attachments 

cc: Mark Hansen, U.S. EPA Region 6 

Tegan Treadaway, LDEQ Air Permits Division 
Attachment 1 
Attachment 2