## Air Quality Modeling Technical Note

Dolet Hills Power Station Mansfield, Louisiana

Prepared for Cleco Power, LLC

and Southwestern Electric Power Company

Prepared by David J. Long, PE and Ashley N. Ullstrom Air Quality Services Section American Electric Power Service Corporation

March 30, 2016i



### TABLE OF CONTENTS

Introduction .............................................................................................. 1 Description of Facility and Area ...................................................... ............... 1 Sierra Club Modeling .................................................................................. 2 Modeling Platform ...................................................................................... 3 Sources Included in this Study...............................................................

......... . 4

Dolet Hills Power Station BPIP Data .............................................

.................. . 4 Background Values .................................................................................... .. 4 Plant Operating Data Considered and Results ..................... ................................. 4

Conclusions ................................................................................................. 6

References ................................................................................................... 7 Appendix .................................................................................................... 8



### LIST OF FIGURES

Figure 1. Dolet Hills Power Station, International Paper an d the nearby area .................... 1



### LIST OF TABLES

Table 1. Summary of Modeled Design Values for All Simulati ons Discussed (Values in ug/m 3
with Background).......................................................................................... 61



### INTRODUCTION

A merican Electric Power Service Corporation (AEPSC) on behalf of Operating Owner Cleco Power LLC and AEP operating company Southwestern Electric Power Company has examined modeling performed by the Sierra Club and performed derivative modeling of the Dolet Hills Power Station located near Mansfield, Louisiana. This Technical Note briefly describes the Sierra Club modeling and outlines issues raised by that modeling that were addressed by the derivative modeling performed as part of this effort. The additional modeling and analysis performed as part of this effort demonstrated that when the stack parameters for Dolet Hills Plant are properly represented in AERMOD, emissions from Dolet Hills Plant and the nearby International Paper Mansfield Mill do not cause or contribute to nonattainment in the area.



### DESCRIPTION OF FACILITY AND AREA

Th e Dolet Hills Power Station is a single unit 650 MW power generating facility. This unit is equipped with a wet scrubber for sulfur and acid gas control, and an electrostatic precipitator for particulate control. The plant is located in DeSoto Parish, Louisiana approximately 11.5 kilometers east of Mansfield, Louisiana and approximately 13.5 kilometers south of an International Paper facility. The elevation of the Dolet Hills Station is 82 meters and the terrain is gently sloping down to the north, east and south of the facility. Figure 1 shows the nearfield view of the area surrounding the Dolet Hills Power Station and the International Paper Mansfield

Mill.

Figure 1. Dolet Hills Power Station, International Paper and the nearby area.

Copyrighted map removed2



### SIERRA CLUB MODELING

As part of a larger program undertaken by the Sierr a Club, the Sierra Club sponsored independent modeling of the Dolet Hills Power Stati on and submitted the results of this modeling to USEPA Region VI. This modeling used su rface and upper air meteorology for the period 2012 – 2014 collected at the Shreveport, Lou isiana national weather service site. The data was processed using the current version of AER MET as of June 2015 with no Beta Options being used.

The receptor set used in the Sierra Club sponsored modeling was developed using AERMET. The only deviation from what would be considered st andard SIP and PSD modeling practice is that the Sierra Club analyst used 1.5 meter tall fl agpole receptors. A test simulation performed as part of this study indicated that the use of the 1.5 meter flagpole receptors served to increase the design value by an insignificant 0.003 ug/m 3

.

The Sierra Club sponsored modeling also endeavored to generate an hourly input file for Dolet Hills Power Station using emissions data sources fr om the USEPA Clean Air Markets Division (CAMD). It does not appear that the Sierra Club Mo deling made any attempt to use CAMD flow data and used a “flat” full load profile based on design conditions likely sourced from permit data that resulted in a flat flow and temper ature profile that was paired with a load varying CEMS based emission rate sourced from CAMD. In doing this, it appears that the Sierra Club analyst did perform some data quality work and reasonably corrected much of the missing,

substituted and troubled data received from CAMD. The potential issues with sourcing modeling data from CAMD data was publically reporte d by Long at the 11 th USEPA Triennial Modeling Conference in August 2015 1

.

The Sierra Club report also raised the following is sues that they claimed caused their modeling to underestimate the actual concentrations present in the area around the Dolet Hills Power

Station 2 :

• Allowable emissions are based on a limitation with an averaging period which is greater than the 1-hour average used for the SO2 air qualit y standard. Emissions and impacts during any 1-hour period may be higher than assumed for the modeling analysis.

• No consideration of facility operation at less than 100% load. Stack parameters such as exit flow rate and temperature are typically lower at less than full load, reducing pollutant dispersion and increasing predicted air quality imp acts.

• No consideration of building or structure downwash. These downwash effects typically increase predicted concentrations near the facility

.

• No evaluation has been conducted to determine if th e stack height exceeds Good Engineering Practice (GEP) height. If the stack hei ght exceeds GEP, the predicted

concentrations will increase.

• No consideration of off-site sources. These other s ources of SO2 will increase the predicted impacts.3

The work performed as part of this review serves to address all of these issues in a fashion that demonstrates that the impacts of these issues eithe r reduces concentrations or has minimal impact on the final conclusion of the modeling exer cise.

At this point, we will address one of the Sierra Cl ub claims outlined above, that being the GEP Stack Height issue. Under the provisions of USEPA SO 2 SIP Designations Modeling Technical Assistance Document specific to the 1-Hour SO 2 Standard, it is permissible to use the full stack height for modeling of actual emissions, regardless of the GEP status of the stack for purposes of designation modeling of the 1-Hour SO 2 Standard 3 . Therefore, with regards to the actual emissions case, the GEP height of the stack is irre levant to the analysis. We would add that since USEPA made major changes to the formulation of AERM OD regarding downwash in version 11059, it is necessary to include a BPIP parameteri zation in the analysis of all stack emission points. The actual stack height of the Dolet Hills Power Station is 160.02 meters and the BPIP calculated GEP Height 247.85 meters. In order to d etermine what impact downwash would have on the analysis, a simulation was made that added t he BPIP parameterization to the inputs for

Dolet Hills Power Station. The results of this sim ulation were compared to the results of the base simulation performed by the Sierra Club and no change in the modeled design value was noted. Therefore, it can be concluded in the case of Dolet Hills Power Station that the GEP height issue and the lack of BPIP parameterization in the Sierra Club modeling described in the Sierra Club modeling report has no impact on the mo deled design value.



### MODELING PLATFORM USED FOR THIS EVALUATION

The Sierra Club sponsored modeling used the current versions of AERMOD and AERMET as of June 2015, that being version 14134. AERMOD and AE RMET were exercised using none of the Beta Options installed in them. As part of thi s evaluation, the version of AERMOD used was Version 15181, which was issued in July 2015. Agai n, no Beta Options were used in AERMOD and an initial simulation was made using AERMOD Ver sion 15181 that exactly matched the results from the Sierra Club modeling. This allows the conclusion that any changes in the results observed in new modeling simulations performed as p art of this evaluation were due to other changes we introduced into the modeling system and not attributable to the change in the version

of AERMOD.

For purposes of this evaluation, we accepted the 20 12 to 2014 meteorologic files developed in the Sierra Club sponsored modeling effort. The rev iew of these files allows us to conclude that the meteorologic files were developed using proper modeling procedures.

While not a standard SIP or PSD configuration, we a lso are using the Sierra Club developed receptor grid which included 1.5 meter flagpole rec eptors. We have previously noted that the use of the flagpole receptors resulted in an insign ificant difference in modeled design values in this area. This conclusion cannot be applied to ot her work using flagpole receptors of this type that should be evaluated for their impact on a site by site basis.4



### SOURCES INCLUDED IN THE MODELING

The sources included in various simulations conduct ed throughout this work included the Dolet Hills Power Station (all simulations) and the Inter national Paper Mansfield Mill in the final two simulations following the obtaining of appropriate inputs for the International Paper facility.



### DOLET HILLS BPIP INFORMATION

BPIP information for use in this evaluation was sup plied by CB&I, the A/E firm used by Cleco Power for technical services relating to the genera tion units they operate. The information supplied appears to have been done using standard p ractices for developing a detailed BPIP analysis, and was used as received.

This result of inserting this data into the input f iles originally developed as part of the Sierra Club sponsored modeling resulted in no change in th e fourth high values generated by AERMOD at levels that would be of regulatory intere st in the sensitivity simulation performed.



### BACKGROUND VALUES

With the exception of the final simulation performe d under this evaluation that used a seasonal hourly background value developed from the 2013-201 5 Shreveport SO 2 Monitor data by AECOM on behalf of International Paper, all simulat ions used the background value of 31.4 ug/m 3 used by the Sierra Club that are based on air qual ity data monitored during 2011 to 2013 at

an SO 2 monitor located in Bossier Parish, Louisiana.

Based on that additive nature of percentile statist ics, the 31.4 ug/m 3 which is noted in the Sierra Club report as representing the 99 th percentile value at the selected monitor results i n the pooled modeled and monitored value representing the 99.99 th percentile value of total impact, a value

that is much more restrictive than the actual 1-Hou r SO 2 Standard. Please refer to the presentation of Sergio Garcia at the 11 th USEPA Modeling Conference 4 for more information on

this calculation.



### PLANT OPERATING DATA CONSIDERED AND RESULTS

In the Sierra Club supported modeling of the Dolet Hills Power Station, the modeling study used both the permit limits for Dolet Hills and a proces sed version of the CAMD based emission data to generate an hourly emissions file for the period 2012-2014. The emissions portion of this file appears to have been inspected and corrected to rem ove missing, substituted, and otherwise invalid data that is reported to CAMD under the req uirements of 40 CFR Part 75, but that is not reasonable for use in air quality modeling in a rat ional manner. However, the inputs for exit velocity (based on flow) and temperature are fixed at values that are represented as being full load values. The study admits that it does not acc ount for reduced load operation, but states that they believe that this serves to reduce the modeled impacts from the study.5

As the evaluation progressed, a limited amount of a ctual operating data became available for comparison to the values used by the Sierra Club an d it became apparent that the current full load operating conditions were significantly differ ent than were used by the Sierra Club. This brief evaluation suggested that the temperature use d as a full load representation may be on the

order of at least 40 F low and the flows and exit v elocities would be higher due to the temperature induced differences in volume. In orde r to not overstate the changes in the initial test of this theory, the second lowest temperature was used and a low end flow value was selected and then corrected for temperature to be u sed as constant inputs as was done by the Sierra Club. This resulted in a 39 F temperature i ncrease to 200 F from 161 F and an increase in exit velocity from 25.84 m/sec to 27.71 m/sec. Thi s hourly file was then run with the BPIP inputs and the resulting model output found the mod eled design value reduced from 218.7 ug/m 3
in the Sierra Club modeling to 188.8 ug/m 3 . While, this was not viewed as a definitive resul t, it did lead to a recommendation that a full actual ope rating inventory be built and run to see if the actual operating conditions would also give a compa rable result. This recommendation was accepted and the full CEMS based operating record f or heat input, flow, SO 2 emissions, and temperature was supplied by CLECO Power to allow th e development of a CEMS based hourly inventory for use in this exercise.

The hourly CEMS based inventory developed by AEPSC as part of this exercise used the principles we have established during the developme nt of a number of CEMS based hourly emissions inventories for some 11 AEP Operated or a ffiliated sites, to date. These principles are discussed in a paper to be presented by David Long at the AWMA Specialty Conference on Air Quality Models in April 2016 in Chapel Hill North C arolina 3 . Once the full data set was received from CLECO Power through their consultant CBI, an AERMOD ready CEMS based hourly inventory was prepared.

When this inventory was run in AERMOD, the result w as further reduced from the test value of 188.8 ug/m3 to 185.8 ug/m 3 , much lower than the Sierra Club generated 218.7 u g/m 3 . Since this case used a fully developed actual operating based hourly inventory this result was viewed as a

robust and credible demonstration that Dolet Hills Power Station did not violate the 1-Hour SO 2 Standard under its actual operating conditions. Th is result also serves to rebut the view of the Sierra Club that moving from their flat full load p arameterization to an actual hourly parameterization that properly reflected reduced lo ad and startup operations would serve to

increase the modeled concentrations. In this case it significantly reduces the modeled concentrations, which in our experience is not an u ncommon outcome when compared to a flat operational profile.

With this information in hand, the only question re maining was what interactive impacts would

Dolet Hills Power Station have with the one other s ignificant source of SO 2 emissions in DeSoto Parish. That source being the International Paper Mansfield Mill approximately 13.5 kilometers

to the north of Dolet Hills. After some discussion s with International Paper, we were able to obtain a modeling inventory that they were using in an effort to potentially demonstrate that DeSoto Parish should be split with the portion of t he county they are located in deemed as being

in attainment with the 1-hour SO 2 Standard. We did not use their Dolet Hills invent ory since it was not based on full operating data from CEMS due to the CAMD data source not containing6

the concurrent temperature data used to adjust the flow data from actual stack conditions to standard conditions (CAMD does not collect this dat a). The information supplied by International Paper also contained a more detailed analysis of background data from a monitor in the Shreveport area that allowed the generation of a seasonal hourly background value. In addition to using the 31.4 ug/m 3 background value developed by the Sierra Club, we also ran the more detailed background data to allow a comparison of a more robust background analysis to the more simple single value that had been used.

Adding the emissions from International Paper resul ted in a domain wide design value of 186.2 ug/m 3 , an increase of 0.4 ug/m 3 when the International Paper facility with what ar e viewed as

reasonable emissions are included in the model. Th e final simulation in this evaluation replaced

the fixed SO 2 background value from the Sierra Club modeling with the AECOM/International Paper developed seasonal hourly background. This c hange resulted in a further reduction in the peak design value from the 186.2 ug/m 3 to 171.0 ug/m 3 . This outcome was expected as the hourly SO 2 concentrations used for background varied from 1.86 7 ppb in hour 7 in the Fall season (4.88 ug/m 3 ) to 9.500 ppb during hour 10 in the Summer season (24.85 ug/m 3 ), all below the constant 31.4 ug/m 3 used in all of the preceding simulations.

The results of these two simulations containing bot h Dolet Hills and International Paper serve to refute the Sierra Club contention that considering the emissions from other significant sources in the area would further serve to significantly incre ase modeled SO 2 values in the area, generating a more widespread nonattainment problem in the DeSo to Parish area. These simulations clearly

demonstrate modeled attainment with the 1-Hour SO 2 Standard under actual operating conditions

at both Dolet Hills Power Station and International Paper. Table 1, below, consolidates all of the simulations discussed into a single table showing h ow the changes made in the modeling platform changed the results in ways that generally contradict the claims made by the Sierra Club sponsored modeling study and show that when actual conditions are properly represented in the model, the area demonstrates modeled attainment wit h the 1-Hour SO 2 Standard. The modeling files used for all simulations except the Initial S ierra Club Model are included in electronic form as an appendix to this document.

Table 1. Summary of Modeled Design Values for All Simulati ons Discussed (Values in ug/m 3
with Background). Facility Initial

Sierra

Club

Model Updated

to
AERMOD

15181 Added

Dolet

Hills

BPIP

Data Dolet Hills Temp/Flow Sensitivity Dolet

Hills

Actual Temp

and

Flow Added

International Paper Updated to

AECOM/IP

Seasonal Background

Dolet Hills 218.7 218.7 218.7 188.8 185.8 185.8 170.5

International Paper NA NA NA NA NA 113.0 95.2

Combined NA NA NA NA NA 186.2 171.07



### CONCLUSIONS

The additional modeling done to support this effort demonstrates that there are significant shortcomings in the Sierra Club’s modeling analysis . This work further demonstrates that the

claims of conservatism made in the Sierra Club mode ling report are not well-founded and are generally inaccurate when the specific issues are a ddressed. Further, this work demonstrates that EPA should make a final designation of attainm ent for DeSoto Parish for the1-hour SO 2 standard.



### REFERENCES

1. Long, David
, The Use of CAMD Data in Air Quality Modeling, 11 th USEPA Triennial Modeling Conference, Research Triangle Park, NC, Au gust 12 – 13, 2015.

2 . Klafka, Steven, Dolet Hills Power Station Mansfi eld, Louisiana – Evaluation of Compliance

with the 1-hour NAAQS for SO 2 , Revised December 2015, page 4.

3 . U.S. EPA, Office of Air Quality Planning and Sta ndards, Air Quality Assessment Division, SO2 NAAQS Modeling Technical Assistance Document , page 22.

4. Garcia, Sergio, Background Concentrations and the Need for a New Sy stem to Update

AERMOD , 11 th USEPA Triennial Modeling Conference, Research Tria ngle Park, NC, August 12 – 13, 2015.

5. Long, David, The Use and Processing of USEPA Clean Air Markets D ivision CEMS Data for Air Quality Modeling and Other Applications , To be presented at The Air and Waste Management Association Specialty Conference The Gui deline on Air Quality Models: The New Path, Chapel Hill, NC, April 12 – 14, 2016.8 

### APPENDIX Modeling Inputs for the Reported Simulations in Ele ctronic Form