Enclosur e to WDNR letter of September 1 6 , 2015

1 

# Analysis to Support a Designation of Attainment for Columbia County

Wisconsin Power and Light Columbia Energy Center

- Portage, Wisconsin September 2015

INTRODUCTION

The Wisconsin Department of Natural Resources (WDNR ) was notified by the United States Environmental Protection Agency (EPA) on March 20, 2015 that Wisconsin Power and Light’s Columbia Energy Center ( also

known as WPL

- Columbia) met the criteria established in the agreem ent between EPA , Sierra Club, and Natural

Resources Defense Council that was accepted as an enforceable order on March 2, 2015 by the U.S. District Court of California. Specifically, during calendar year 2012, Columbia Energy Center reported emissions to the

EPA Air Markets Database of more than 16,000 tons of sulfur dioxide (S O 2 ) and therefore EPA is directed to complete designation of the area relative to the 1

- hour SO 2 National Ambient Air Quality Standard (NAAQS) by July 2, 2016

.

In response to this action, WDNR completed a five factor analysis as described in EPA’s SO 2 area designations guidance and is recommending that EPA designate Columbia County

, Wisconsin as attainment for the 1

- hour

SO 2 NAAQS. T he supporting information inc ludes a dispersion modeling analysis using the regulatory model

AERMOD (AMS/EPA Regulatory Model) that demonstrates the 1

- hour SO 2 NAAQS will b e attained and

maintained in Columbia County

.

AREA CHARACTERIZATION

Columbia Energy Center (part of Alliant En ergy) is located south of the City of Portage along the Wisconsin

River in centr al Columbia County, Wisconsin (refer to Figure 1). Columbia County is located in south central Wisconsin, approximately 45 kilometers north of the Wisconsin State Capitol in M adison. The climate of Columbia County is characterized by variable weather patterns with a large seasonal temperature range and moderate amounts of precipitation. Terrain in Columbia County is generally flat, except in the western part

where the Baraboo Range is the dominant feature. In addition, t he Wisconsin River crosses Columbia County in

a broad

, shallow river valley

.

Columbia Energy Center is a base load electrical generating facility with nominal capacity of 1,054 megawatts that began operation during the 1970’s. The facility consists of two pulverized subbituminous c oal fired boiler/generator sets, each with maximum rated heat capacity of 5,880 million British Thermal Units per hour (MMBtu/hr) . A s of January 1, 2015 the facility is limited by federally enforceable conditions to 3,286 tons of

SO 2 per year , while continuously operating their air quality control system and not exceeding emissions of 0.075 pounds of SO 2 per million Btu ( lbs/MMBtu ) over a 30

- day rolling average.

MODEL & METEOROLOGY

W DNR use d the current regulatory version of AERMOD (15181) in the dispersion modeling analysis

. AERMOD options that are subject to public comment and revision were not u sed

. The area around Columbia Energy Center consists of small farm parce ls, wetland associated with the Wisconsin River, and scattered

residences. Following Section 7.2.3(c) of the current Guideline on Air Quality Models (40 CFR Part 51

,Enclosur e to WDNR letter of September 1 6 , 2015

2 Appendix W

, EPA , November 2005 ) , an assessment of the land use around Columbia Energy Cen ter shows that

less than 50% of the land area within 3 kilometers is industrial, commercial, or dense residential. Therefore, rural dispersion coefficients were used in AERMOD.

Meteorological data w ere processed from 20 12

- 201 4 Dane County Regional Airport (KMSN) surface data with Green Bay upper air data. The raw meteorological data were processed with the regulatory options in AERMET version 15181. Options that are subject to public comment and revision w ere not used. The surface wind data

at K M SN is 2

- minute average speed and direction reported each minute. This minute

- based wind information

was processed with AERMINUTE version 1 4337

. Processing assume d an anemometer height of 10.0 meters (m) above ground.

The instrumentation tower at K MSN is 40 kilometers south

- southeast of Columbia Energy Center and is considered representative of meteorological conditions around the facility. Dane County Regional Airport is at the northern boundary of the City of Madison, Wisconsin, and is surrounded by small farm fields and wetlands,

similar to the land cover around Columbia Energy Center

. Surface characteristics around K MSN w ere generated using AERSURFACE version 13016 following the methods described in the AERMOD Implementation Guide. Specifically, s now cover for each month during the period 20 12

- 201 4 w as derived from

National Snow Analyses maps from the National Operational Hydrologic Remote Sensing Center

. AERSURFACE w as run both for snow and no

- snow conditions . T he albedo , Bowen ratio, and surfac e roughness were adjusted based on the number of days with snow cover during each month. Soil moisture conditions for each year were a weighted average of the monthly Palmer Drought Severity Index obtained from

the National Centers for Environmental Infor mation . The months of May, June, July, and August w ere weighted twice as high as the other months to account for the importance of soil moisture during the traditional growing season.

EMISSIONS INVENTORY

When determining attainment boundaries, EPA evaluates actual SO 2 emissions from sources located in and around the area characterized, according to the Updated Guidance for Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality Standard ( EPA , Mar 20, 2015) . The Updated G uidance describes how data from the latest National Emissions Inventory or other relevant data would be reviewed. In support of the recommendation that all of Columbia County be designated attainment for the 2010 SO 2 NAAQS, WDNR

considered known SO 2 emiss ions in the county.

Columbia Energy Center has the largest emissions of SO 2 within Columbia County. In addition to the two coal power boilers, Columbia Energy Center also operates a limited use, fuel

- oil fired, 182 MMBtu/hr auxiliary

boiler. This unit i s used in boiler operator training and to provide small amounts of heat for the facility. The

SO 2 emissions from the unit are, at maximum, 0.3 lbs/hr and these emi ssions vent from a 78 m (256 fee t) tall, unobstructed stack. A screening level dispersion modeling analysis was perform ed to assess the impact of the auxiliary boiler SO 2 emissions to ambient air, and it was determined that modeled concentrations at all locations

are below the 1

- hour SO 2 significant impact level (SIL).

The following table li sts all other point sources of SO 2 in Columbia County based on the 2014 emission inventory data. The location of these sources is shown in the attached Figure 1.Enclosur e to WDNR letter of September 1 6 , 2015

3 COLUMBIA ENERGY CENTER

- PORTAGE Emissions Inventory

FACILITY NAME 2014 TONS SO 2

Cardinal FG 61.6

United Wisconsin Grain Producers 8.5

Fall River Foundry 2.3

The data shows no other major (greater than 100 tons per year) sources of SO 2 emissions within Columbia County or within 5 0 kilometers (km) of Columbia Energy Center

. Fall River Foundry is located 31 km

southeast of Columbia Energy Center and the SO 2 emissions result from brass and bronze induction melting.

United Wisconsin Grain Producers is 30 kilometers northeast of Columbia Energy Center and t he SO 2 emissions

resul t from drying of distiller grain solubles. Due to the ir distance, the impacts of both Fall River and UWGP do not result in a significant concentration gradient around Columbia Energy Center and are ass umed to be included in the background concentration used in the analysis (refer to the Background Concentration section)

.

SO 2 emissions are also reported from Cardinal FG in Portage, approximately 10 km north

- northwest of Columbia Energy Center

. In 2014, Cardinal FG reported 61.6 tons of SO 2 emitted fr om the glass furnace stack. The glass furnace stack is 61 m (200 feet) tall with an unobstructed, warm gas flow. A screening level dispersion modeling analysis was performed to assess the impact of the potential SO 2 emissions from Cardinal

FG to ambient air. The maximum modeled impact of Cardinal FG is well below the 1

- hour SO 2 standard and southwest of the facility in an area of elevated terrain . Further review of the Cardinal FG screening level modeling results reveals that the impact is above the 1

- h our SO 2 SIL only in the areas of elevated terrain. For all other receptors, including the area around Columbia Energy Center , the modeled impact of Cardinal FG in Portage is below the 1

- hour SO 2 SIL.

Due to the screening analyses de scribed , it was assu med that the selected background concentration provides adequate representation of additional distant SO 2 emissions, so only the two main Columbia Energy Center boilers were explicitly included in the modeling analysis

.

INPUT PARAMETERS

Modeled s tack parameters and buil ding downwash data for Columbia Energy Center w ere taken from the most recent WDNR analysi s for the facilit y, with additional information provided by WPL/Alliant

. Modeled

e mission rates reflect ed both the highest potential sh ort

- term ho urly rate corresponding to the maximum heat input and the normal or typical scenario corresponding to the most common heat input. Columbia Energy

Center is a base load plant, so there are minimal variations in the heat input throughout the year. For each

modeled scenario (maximum or normal) , the representative exhaust gas flow rate and temperature w ere provided by WPL/Alliant as derived from actual performance during calendar year 2015

. BPIP

- PRIME w as

a lso be used to prod uce the building downwash informa tion from facility provided plot plans

.

The federally enforceable emission limit for Columbia Energy Center is based on the 30

- day average of 0.075 lbs/MMBtu. To conservatively estimate a comparable hourly emission rate, the method outlined in Appendix B

of the Guidance for 1

- Hour SO 2 Nonattainment Area SIP Submissions ( EPA

, Apr 23, 2014) was followed. From

the 2015 emission data captured on the continuous emission monitors at Columbia Energy Center , the 99 th
percentile of the hourly mass (lbs) value was divided by the 99 th percentile of the 30

- day average hour mass (lbs) value. The ratios for each unit were calculated separately and the higher ratio was determined to be 5.67

. After rounding this value up to 6.0, t he Columbia Energy Center 30

- day emissions limit of 0.075 lbs/MMBtu was multiplied by 6.0 resulting in a maximum hourly emission rate estimate of 0.45 lbs/MMBtu (0.075 * 6.0 =Enclosur e to WDNR letter of September 1 6 , 2015

4 0.45). This value w as then used in both the maximum and normal model scenarios to calculate a representat ive, conservative estimate of potential hourly emissions from both stacks based on boiler heat input

.

Note that in comparison to Appendix D of the Guidance for 1

- Hour SO 2 Nonattainment Area SIP Submissions

, the scaling factor of 6.0 is much higher than wh at would be expected. Based on the information provided in Appendix D, the scaling factor of 6.0 is more than two standard deviations from the average scaling factor of 1.6. Considering that Columbia Energy Center has just recently begun using the contro l devices on the boilers, it is expected that the actual scaling factor will be lower than 6.0, thus confirming the conservative nature of this dispersion modeling analysis.

RECEPTOR GRID

The receptor grid used in the analysis will consist of a series of nested rectangular grids with terrain derived from AERMAP using National Elevation Dataset information (refer to Figure 1).

 50 meter spacing to 1000 meters from the stacks

 100 meter spacing to 10 kilometers

 Additional 100

- meter spaced points on the Bara boo Range (west of the facility), extending to 30 km

Individual receptors will be removed where it is not feasible to place a monitor following the recommendations

in the SO 2 NAAQS Designations Technical Assistance Document s ( EPA , December 2013)

. Receptors located immediately adjacent to Columbia Energy Center that are inside the fence line or are not considered ambient air

will be removed from the modeling analysis . In addition, using WDNR geographic information service (GIS) data, receptors loca ted over the permanent wetlands between Columbia Energy Center and the Wisconsin River, or over any open water body in the modeling domain

, will also be removed from the modeling analysis

.

BACKGROUND CONCENTRATION

The closest representative SO 2 monito ring location to Columbia Energy Center is the Horicon (Dodge County) monitor located 65 kilometers east of the facility. Columbia Energy Center is the only major (100 tons per year)

SO 2 source within 65 kilometers of the Horicon site, which uses high sen sitivity equipment to detect low SO 2 concentrations. The 2012

- 2014 Horicon design value of 7 ppb (18.3 μg/m 3 ) is used as background concentration for this analysis. The modeling analysis includes all known point sources of SO 2 within Columbia County and within 5 0 kilometers of Columbia Energy Center , and the monitor location is similarly affected by

distant SO 2 sources (in central, southern, and eastern Wisconsin). Nationally, the impact from locomotives and

trucks has been minimized as the sulfur content in diesel fuel has been reduced to 0.015%, and the local impact

of these vehicles is even smaller as Columbia Energy Center is located outside of any incorporated city or village

.Enclosur e to WDNR letter of September 1 6 , 2015

5 MODELING RESULTS

The stack parameters and emissio n rates for the dispersion modeling analysis are provided in the table.

WPL COLUMBIA

- PORTAGE

Point Source Stack Parameters & Emission Rates

ID LOCATION (UTM83) HEIGHT (M) HEIGHT (ft) DIAM (M) VELOCITY (M/S) TEMP (K) SO 2 Rate (#/HR)

S11Max 304248, 4817601 152.4 500.0 6.401 29.49 350.0 2700

S11Norm 304248, 4817601 152.4 500.0 6.401 23.04 343.0 2025

S12Max 304248, 4817675 198.1 650.0 6.401 30.55 359.0 2648

S12Norm 304248, 4817675 198.1 650.0 6.401 21.88 350.0 1800

The impact of Columbia Energy Center in relation to the 1

- hour SO 2 NAAQS is calculated f or each scenario (maximum and normal) with both stacks operating . The regulatory default option in AERMOD w as selected

and results compiled consistent with the f orm of the 1

- hr NAAQS , i.e. t he thre e

- year average of the fourth

highest daily max

- hour was computed for each receptor and added to the background concentration.

The result from the analysis shows concentrations below the NAAQS assuming either maximum or normal load

conditions Columbia Ener gy Center . Results are presented both in micrograms per cubic meter 

### ( μg/m 3 ) and in parts per billion (ppb), assuming a conversion factor (1 atm, 20 o C) of 1 ppb = 2.616 

### ( μg/m 3 )

.

WPL COLUMBIA

- PORTAGE Modeling Results (Concentrations in μg/m 3 )

1

- Hour SO 2 Maximum Heat Input 1

- Hour SO 2 Normal Heat Input

Modeled Impact 140.7 124.2

Background Concentration 18.3 18.3

Total Impact 159.0 142.5

NAAQS 196 196

WPL COLUMBIA

- PORTAGE Modeling Results (Concentrations in ppb )

1

- Hour SO 2 Maximum Heat Input 1

- Hour SO 2 Normal Heat Input

Modeled Impact 53.8 47.5

Background Concentration 7 7

Total Impact 60.8 54.5

NAAQS 75 75Enclosur e to WDNR letter of September 1 6 , 2015

6 CONCLUSION

The impact of the SO 2 sources in Columbia County is not predicted to result in a violation of the 1

- hour SO 2 NAAQS in any part of the county. Columbia Energy Center , the main source of SO 2 in the county, was explicitly modeled following the procedures in the Guideline on Air Quality Models (40 CFR Part 51, Appendix
W, EPA , November 2005) and the SO 2 NAAQS Designations Technical Assistance Document s ( EPA , December 2013)

. The other smaller sources of SO 2 emiss ion s in the county were appropriately considered in the selected background concentration or otherwise demonstrated to have a small impact relative to Columbia Energy

Center

. This analysis supports WDNR ’s recommend ation that EPA designate all of Columbia County

, Wisconsin as attainment for the 1

- hour SO 2 NAAQS.Enclosure to WDNR letter of September 18, 2015

Figure 1

– Columbia County Emissions and Columbia Energy Center Modeling Domain