REVISED DESIGNATION

RECOMMENDATION

FOR SULFUR DIOXIDE

Buffalo-Cheektowaga, NY CSA 

2010 Primary National Ambient Air Quality Standard

September 2015

DIVISION OF AIR RESOURCES

Bureau of Air Quality Planning

Albany, NY 12233-3251 

P: (518) 402-8396 | F: (518) 402-9035 | dar.sips@dec.ny.gov

www.dec.ny.gov

Table of Contents

Introduction ..................................................................................................................... 3

Background..................................................................................................................... 4

NAAQS and Designations................................................................................................ 4

EPA’s Data Requirement Rule......................................................................................... 6

SO2 Emissions Monitoring and Monitoring Data ............................................................. 7

New York’s SO2 Emissions Monitoring System................................................................ 7

Figure 1: 2015 Ambient Air Monitoring Network SO2 Monitoring Sites ............................. 7

Monitoring Data ............................................................................................................... 8

Table 1: SO2 Design Values for Monitors of Concern from 2011 through 2014*............... 8

Table 2: SO2 Design Values for Tonawanda Monitors...................................................... 9

TONAWANDA MONITOR STREET ADDRESS............................................................... 9

Table 3: Peak 1-hour SO2 Concentrations for Tonawanda Monitors ...............................10

Supporting Information (Five-Factor Analysis) .............................................................. 11

Factor 1: Dispersion Modeling ........................................................................................11

Factor 2: Emissions-Related Data...................................................................................12

Table 4: SO2 Emissions Trends for Cattaraugus, Erie and Niagara Counties..................14

Table 5: SO2 Emissions (tons): Cattaraugus County Point Sources................................15

Table 6: SO2 Emissions (tons): Erie County Point Sources.............................................15

Figure 2: Sources Emitting Greater Than 40 tons/year of SO2 near Huntley ...................16

Table 7: SO2 Emissions (tons): Niagara County Point Sources.......................................17

Figure 3: Sources Emitting Greater Than 40 tons/year of SO2 near Somerset ................17

Table 8: Cattaraugus County Airports: 2011 Emissions Inventory...................................18

Table 9: Erie County Airports: 2011 Emissions Inventory................................................19

Table 10: Niagara County Airports: 2011 Emissions Inventory........................................20

Factor 3: Meteorology .....................................................................................................21

Figure 4: Wind Roses from Buffalo Niagara International Airport and Niagara Falls 

International Airport.........................................................................................................21

Figure 5: SO2 Pollution Wind Rose for Tonawanda II Monitor .........................................22

Factor 4: Geography and Topography ............................................................................24

Factor 5: Jurisdictional Boundaries .................................................................................25

Recommendations..........................................................................................................26

1 
APPENDIX A: Air Quality Modeling for Huntley Generating Station.............................. 27

APPENDIX B: Air Quality Modeling for Somerset Station ............................................. 28

2 
Introduction

Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as “oxides of 

sulfur.” The largest sources of SO2 emissions are from fossil fuel combustion at power 

plants and other industrial facilities. Smaller sources of SO2 emissions include industrial 

processes and the burning of high sulfur containing fuels by locomotives, large ships, 

and non-road equipment. SO2 is linked with a number of adverse effects on the 

respiratory system. Exposure to sulfur dioxide can cause irritation and/or inflammation 

of the skin and mucous membranes of the eyes, nose, throat, and lungs. The 

respiratory system is particularly affected during heavy physical activity. High 

concentrations of SO2 can affect lung function, worsen asthma attacks, and aggravate 

existing heart disease in sensitive groups, such as children, the elderly, and those with 

chronic lung disease.

On March 2, 2015, the U.S. District Court for the Northern District of California accepted 

as an enforceable order an agreement between the EPA and Sierra Club and Natural 

Resources Defense Council to resolve litigation concerning the deadline for completing 

designations for the 2010 primary SO2 National Ambient Air Quality Standard (NAAQS). 

In the first round of designations to be completed by EPA no later than July 2, 2016, 

EPA must designate two groups of areas: 1) areas that have newly monitored violations 

of the 2010 SO2 NAAQS, and 2) areas that contain any stationary source that, 

according to the EPA’s Air Markets Database, either emitted more than 16,000 tons of 

SO2 in 2012 or emitted more than 2,600 tons of SO2 and had an emission rate of at 

least 0.45 lbs. SO2/mmBtu in 2012 and that has not been announced (as of March 2, 

2015) for retirement. 

EPA has identified two electric power plant sources in New York State (NRG Huntley 

Generating Station (Huntley), Erie County and AES Somerset LLC (Somerset), Niagara 

County) as meeting the first-round criteria established in the court order. Consequently, 

the New York State Department of Environmental Conservation (DEC) is submitting a 

revised designation request for the entire Buffalo-Cheektowaga, NY Combined 

Statistical Area (CSA) for the 2010 primary SO2 NAAQS pursuant to section 107(d) of 

the Clean Air Act (CAA). Since the Buffalo-Cheektowaga, NY CSA also includes 

Cattaraugus County, DEC included an analysis of the attainment status for Cattaraugus 

County.

3 
Background

NAAQS and Designations

On June 2, 2010, EPA strengthened the primary SO2 NAAQS by establishing a new 

1-hour standard at a level of 75 parts per billion (ppb). At the same time, EPA revoked 

the two existing primary standards of 140 ppb evaluated over 24-hours, and 30 ppb 

evaluated over an entire year, because they will not add additional public health 

protection given a 1-hour standard of 75 ppb. The 2010 SO2 standard includes a new 

form; the 3-year average of the 99th percentile of the annual distribution of daily 

maximum 1-hour concentrations. 

DEC submitted New York’s designation request for the 2010 SO2 NAAQS on June 1, 

2011. This request provided details of New York’s SO2 Emissions Monitoring System in 

2011 as well as actual monitoring data for New York and adjacent states. DEC 

recommended that all areas of New York be designated as “attainment”, with the 

exception of the Poughkeepsie-Middletown-Newburgh Core-Based Statistical Area 

(CBSA). DEC recommended that this area be classified as “unclassifiable” since 

sufficient monitoring data was not available at the time to make an attainment 

determination. No area of the State indicated nonattainment based on the monitoring 

data. 

On July 27, 2012, EPA extended the deadline for area designations for the 2010 

primary SO2 standard by approximately 1 year due to comments received on the 

approach for informing initial designations, and remaining uncertainties about the 

analytic approach states would use for designation determinations and for general 

implementation. With this extension, EPA intended to complete initial designations by 

June 3, 2013. 

EPA responded to New York’s June 1, 2011 designation request on February 6, 2013. 

At that time, EPA was only proceeding with designating as nonattainment areas in 

locations where existing monitoring data for 2009-2011 indicated violations of the 1-hour 

SO2 standard. Since EPA’s review of the monitoring data for 2009-2011 showed no 

violations of the 2010 SO2 NAAQS in any areas in New York State, EPA deferred action 

to designate any areas in New York. 

4
Three lawsuits were filed against EPA alleging the agency failed to designate areas by 

June 2013. On March 2, 2015 U.S. District Court for the Northern District of California 

issued an enforceable order under which EPA must complete 1-hour SO2 NAAQS 

designations of the remaining areas of the country in up to three additional rounds: the 

first round by July 2, 2016, the second round by December 31, 2017, and the final round 

by December 31, 2020.

1. In the designations to be completed by July 2, 2016, EPA will designate in two

groups:

1. Areas that have monitored violations of the 2010 SO2 standard based on

2013 –2015 air quality data.

2. Areas that contain any stationary source not announced for retirement that

according to EPA’s Air Markets Database emitted in 2012 either (a) more

than 16,000 tons of SO2, or (b) more than 2,600 tons of SO2 and had an

average emission rate of at least 0.45 lbs. SO2/mmBtu.

On March 20, 2015, EPA notified DEC that two facilities in New York were 

identified as meeting the nonattainment designation criteria for emitting more 

than 2,600 tons of SO2 and having an emission rate of at least 0.45 lbs.

SO2/mmBtu in 2012 and have not announced (as of March 2, 2015) that they will 

be retired. This revised designation recommendation addresses this issue.

2. The court’s order directs the EPA to complete an additional round of area

designations by December 31, 2017 addressing areas where states have not

installed and begun operating a new SO2 monitoring network meeting the EPA’s

specifications referenced in the Agency’s anticipated final titled, “Data

Requirements Rule for the 1-hour SO2 primary NAAQS”.

3. Lastly, the court’s order directs the EPA to designate all remaining areas by

December 31, 2020.

5 
EPA’s Data Requirement Rule 

On April 17, 2014, EPA proposed requirements for air agencies to characterize SO2 air 

quality more extensively for purposes of implementing the 2010 SO2 NAAQS. Air 

agencies would have the flexibility to characterize air quality using either modeling of 

actual source emissions or using appropriately sited ambient air quality monitors. EPA 

intends to use these data in two future rounds of area designations in 2017 and 2020. 

The proposed Data Requirements Rule includes options for emissions thresholds which 

would identify the sources around which air agencies would need to characterize SO2

air quality. To increase public health protection in more highly populated areas, each 

option includes a lower annual emissions threshold for sources located in metropolitan 

areas greater than 1 million in population, and a higher threshold for sources outside 

these areas.

1. Option 1 would cover sources greater than 1,000 tons of SO2 in metro areas with

population greater than 1 million; and sources greater than 2,000 tons

everywhere else.

2. Option 2 would cover sources greater than 2,000 tons of SO2 in metro areas with

population greater than 1 million; and sources greater than 5,000 tons

everywhere else.

3. Option 3 would cover sources greater than 3,000 tons of SO2 in metro areas with

population greater than 1 million; and sources greater than 10,000 tons

everywhere else.

The final proposed Data Requirements Rule was submitted to the Office of 

Management and Budget on May 28, 2015 with a final rule expected in October 2015.

The outcome of the final rule will impact how New York and the EPA proceed with the 

second round of designation recommendations. 

6 
SO2 Emissions Monitoring and Monitoring Data

New York’s SO2 Emissions Monitoring System 

The DEC Division of Air Resources operates an ambient air monitoring network for 

various air contaminants within New York State, including SO2. As required by federal 

regulations, DEC prepares an annual monitoring network plan, which describes in detail 

the specifics of the monitoring network. This plan includes an annual review of the 

existing monitoring network to determine the adequacy of the network and to propose 

any network modifications. Pursuant to the proposed 2015 Annual Monitoring Network 

Plan, which can be found at http://www.dec.ny.gov/chemical/33276.html, New York 

State’s existing SO2 monitoring locations are shown in Figure 1.

Figure 1: 2015 Ambient Air Monitoring Network SO2 Monitoring Sites

7 
Monitoring Data 

The 2010 primary SO2 NAAQS is set at a level of 75 ppb and takes the form of 99th 

percentile of 1-hour daily maximum concentrations, averaged over 3 years. For 

example, the design value for 2014 is calculated using monitoring data from 2012, 2013 

and 2014. Table 1 provides design values for the SO2 monitors in and closest to Erie 

and Niagara counties. When considering all design values from 2011 through 2014, all 

monitors attain the 2010 primary SO2 NAAQS by a large margin with SO2 emissions 

continuing to decline. 

Table 1: SO2 Design Values for Monitors of Concern from 2011 through 2014* 

Monitor County Location SO2 Design Values (ppb)

2011 2012 2013 2014

Rochester Monroe

RG&E Substation

@ 

2 Yarmouth Road

24 23 20 20

Buffalo Erie Trailer @ 

185 Dingens Street 19 17 15 10

Brookside 

Terrace

(Tonawanda II)

Erie 192 Brookside 

Terrace West 32 29 25 22

Dunkirk Chautauqua STP @ 

Wright Park Drive 34 27 22 18

Addison Steuben Pinnacle State Park 16 12 10 9 

Niagara 

Falls* Niagara Frontier Ave. @ 55th Street 17 14 N/A N/A

Source: EPA AQS Design Value Report generated August 3, 2015.

*The Niagara Falls monitor ceased operation at the end of 2012. While not shown in Figure 1, the data

from this monitor is used in the dispersion modeling analysis.

The Erie County monitor now located to 192 Brookside Terrace West (Tonawanda II)

was originally located at 779 Two Mile Creek Road (Tonawanda I). It was moved as 

part of the Tonawanda Community Air Quality Study in 2007 and now borders a 

residential neighborhood and industrial complex approximately 0.2 mile northeast of the 

original site. While this move occurred well before the new 1-hour SO2 NAAQS became 

effective, DEC wants to assure EPA that moving the monitor was not the cause of the 

sharp decline in peak 1-hour SO2 concentrations and design values that occurred 

during the same time period. 

The primary reason for the sharp decline in peak 1-hour SO2 concentrations and design 

values was the precipitous drop in SO2 emissions from stationary sources located in 

Erie County as a result of the PSD (Prevention of Significant Deterioration) Consent 

8 
Decrees involving coal power generating facilities and new regulations taking effect at 

the time, especially 6 NYCRR Part 245, CAIR SO2 Trading Program. Erie County 

stationary source emissions decreased from 11,609 tons of SO2 in 2007 to 7,422 tons 

of SO2 in 2008. Huntley alone decreased from 10,613 tons of SO2 in 2007 to 6,853 tons 

of SO2 in 2008. Additionally, EPA implemented Ultra Low Sulfur Diesel (ULSD) 

standards for on-road diesel fuel. The new requirement of 15 ppm was phased in from 

2006-2010.

Monitoring data shows that the Tonawanda I monitor exceeded the 1-hour SO2 NAAQS 

of 75 ppb in 2007 with a design value of 119 ppb and in 2008 with a design value of 88 

ppb. Since this is the only monitor that exceeded the 1-hour SO2 NAAQS with actual 

monitor data, these values were examined more closely. Because of the Tonawanda I 

monitor’s proximity to the new Tonawanda II monitor location, design values were 

calculated for the years that were missing data at that location by substituting the values 

for the adjacent monitor instead; that allowed DEC to calculate values for all three-year 

Design Value periods, for both monitors. Those three-year design value periods are 

shown below in red in order to distinguish them from the non-substituted values:

Table 2: SO2 Design Values for Tonawanda Monitors

TONAWANDA MONITOR 

STREET ADDRESS

SO2 Design Values (ppb)

2007 2008 2009 2010

192 BROOKSIDE TERRACE 

WEST (Tonawanda II) 88 62 39 36

779 TWO MILE CREEK ROAD

(Tonawanda I) 119 88 65 30

9 
Table 3 provides additional evidence that the monitor site change in Tonawanda was 

not the reason for the sharp decline observed in peak 1-hour concentrations. Both 

monitors were operating for the sixth month period from July 2007 through December 

2007 and showed comparable peak concentrations and a precipitous drop in November 

2007. Sampling at the Tonawanda I monitor terminated on December 31, 2007.

Table 3: Peak 1-hour SO2 Concentrations for Tonawanda Monitors

Month Tonawanda I

(ppb)

Tonawanda II

(ppb)

July 2007 17 40

August 2007 51 39

September 2007 32 35

October 2007 63 58

November 2007 24 18

December 2007 31 25

With a decreasing trend in SO2 values clearly demonstrated for these two monitoring 

locations since 2007, it can be concluded that the Tonawanda II monitoring location 

does not present an area of heightened concern for the 2010 SO2 NAAQS. 

10
Supporting Information (Five-Factor Analysis)

Factor 1: Dispersion Modeling 

DEC performed dispersion modeling to assess the areas around Huntley and Somerset 

in the context of the proposed federal 1-hour SO2 Data Requirements Rule (DRR). 

DEC’s methodology was based on policies and procedures contained in EPA’s 

Guideline on Air Quality Models (40 CFR Appendix W) and DEC’s Air Quality Modeling 

Procedures as outlined in DAR-10 / NYSDEC Guidelines on Dispersion Modeling 

Procedures for Air Quality Impact Analysis, modified by the SO2 NAAQS Designations 

Modeling Technical Assistance Document (Modeling TAD) where applicable.

For the Huntley modeling analysis (2012-2014 time period), included in this report as 

Appendix A, actual hourly emissions data obtained from the facility were matched with 

three years of concurrent surface and upper-air meteorological data from Buffalo

Niagara International Airport to run AERMOD version 14134 using true stack height 

regardless of Good Engineering Practice (GEP). AERMOD calculated impacts show 

that Huntley contributed 44.1 ppb to the 54.3 ppb 4th highest concentration that includes 

seasonally-based hourly background concentrations for SO2. This maximum impact, 

which is located at the southeastern boundary of the facility’s property, falls well below 

the 2010 SO2 NAAQS of 75 ppb. 

For the Somerset modeling analysis (2011-2013 time period), included in this report as 

Appendix B, AERMOD version 14134 was run for two scenarios:

1. Three years of hourly emissions data obtained from the facility were matched

with 3 years of concurrent meteorological data from both Buffalo Niagara

International Airport and Niagara Falls International Airport to run AERMOD

version 14134 using the actual stack height.

2. A fixed emission rate based on a permit limit to comply with the Mercury Air

Toxics Standards (MATS) was modeled with 5 years of meteorological data and

the GEP stack height.

AERMOD calculated impacts for Scenario 1 show that Somerset contributes 35.1 ppb to 

the 42.6 ppb 4th highest concentration that includes seasonally-based hourly 

background concentrations for SO2. AERMOD calculated impacts for Scenario 2 show 

that Somerset contributes 13.1 ppb to the 20.6 ppb 4th highest concentration that 

includes seasonally-based hourly background concentrations for SO2. The maximum 

impact from both scenarios, which occurs just northeast and southeast of the facility’s 

property, falls well below the 2010 SO2 NAAQS of 75 ppb. Given the recent Supreme 

Court decision1 resulting in an uncertain future for the MATS rule, only Scenario 1 was 

considered in making this designation recommendation. 

1 June 29, 2015: MICHIGAN ET AL. v. ENVIRONMENTAL PROTECTION AGENCY ET AL.

 http://www.supremecourt.gov/opinions/14pdf/14-46_10n2.pdf

11
Factor 2: Emissions-Related Data

Over the years, New York has adopted several regulations that have had a significant 

impact on reducing SO2 emissions. These include:

Regulation Title

6 NYCRR Part 248 Use of Ultra Low Sulfur Diesel Fuel and 

Best Available Retrofit Technology for 

Heavy Duty Vehicles

6 NYCRR Subpart 225-1 Fuel Use and Composition – Sulfur 

Limitations

6 NYCRR Part 245 CAIR SO2 Trading Program 

6 NYCRR Part 249 Best Available Retrofit Technology 

(BART)

6 NYCRR Part 248 (regulation effective 2009) requires the use of Ultra low sulfur diesel 

fuel (ULSD) having a content of 0.0015 percent (15 ppm) of sulfur or less and applies to 

all heavy duty vehicles except for:

(1) locomotives;

(2) alternative fuel vehicles;

(3) any HDV subject to a lease or contract entered into or last renewed prior to 

February 12, 2007; and

(4) any on road vehicle with engine model years prior to 1960.

6 NYCRR Part 248 also requires that on or after December 31, 2013, all diesel powered 

heavy duty vehicles owned by, operated by, or leased by each BART regulated entity or 

which are owned by, operated by, or leased by a contractor and used to provide labor, 

services, materials and/or equipment on behalf of a BART regulated entity to perform 

regulated entity work were required to utilize and maintain BART.

For 6 NYCRR Part 225: 

• 6 NYCRR Part 225-1.2(c) requires owners and/or operators of any stationary

combustion installation in Erie and Niagara Counties that fires solid fuels are

limited to the firing of solid fuel with a maximum sulfur content of 1.7 pounds per

million Btu and an average sulfur content of 1.4 pounds per million Btu on or after

July 1, 2014.

• 6 NYCRR Part 225-1.2(e) requires owners and/or operators of any stationary

combustion installation in Erie and Niagara Counties that fires residual oil are

limited to the purchase of residual oil with a sulfur content of 0.50 percent sulfur

by weight low on or after July 1, 2014, and are limited to the firing of residual oil

with a sulfur content of 0.50 percent sulfur by weight on or after July 1, 2016.

12
• 6 NYCRR Part 225-1.2(f) requires owners and/or operators of commercial,

industrial, or residential emission sources that fire number two heating oil on or

after July 1, 2012 are limited to the purchase of number two heating oil with

0.0015 percent sulfur by weight or less.

• 6 NYCRR Part 225-1.2(g) requires owners and/or operators of a stationary

combustion installation that fires distillate oil other than number two heating oil

are limited to the purchase of distillate oil with 0.0015 percent sulfur by weight or

less on or after July 1, 2014.

• 6 NYCRR Part 225-1(h) requires owners and/or operators of any stationary

combustion installation that fires distillate oil including number two heating oil are

limited to the firing of distillate oil with 0.0015 percent sulfur by weight or less on

or after July 1, 2016.

• 6 NYCRR Part 225-1.2(i) requires owners and/or operators of any stationary

combustion installation that fires waste oil on or after July 1, 2014 are limited to

the firing of waste oil with 0.75 percent sulfur by weight or less.

6 NYCRR Part 245 established an annual SO2 Budget Trading Program for EGU’s 

beginning in 2010 (New York State emissions cap = 135,139 tons) and required further 

emission reductions starting January 1, 2015. However, 6 NYCRR Part 245 has been 

superseded by the federal Cross-State Air Pollution Rule (CSAPR) with a 2015 (Phase 

I) New York State SO2 emissions cap of 36,296 tons. CSAPR Phase II in 2017 has a

New York State SO2 emissions cap of 27,556 tons. In Erie County, Huntley has a 2015 

SO2 allocation of 2,673 tons which is reduced to 1,950 tons in 2017. In Niagara County, 

Somerset has a 2015 allocation of 5,147 tons which is reduced to 3,754 tons in 2017. 

These are substantial SO2 emissions reductions that are expected to have the 

continued effect of lower 1-hour SO2 design values in Erie and Niagara Counties, as 

well as statewide.

6 NYCRR Part 249 restricts the emissions of visibility-impairing pollutants, including 

SO2, by requiring the installation of Best Available Retrofit Technology (BART) on a 

BART-eligible stationary source to reduce regional haze and restore natural visibility 

conditions to Federal Class I Areas. While no BART-eligible stationary sources exist in 

Erie and Niagara counties, reductions in SO2 emissions from BART-eligible stationary 

sources will be realized in other parts of New York State. 

13
Table 4 provides SO2 emissions trends for Cattaraugus, Erie and Niagara counties. All 

three counties exhibit a declining emissions trend from 2005 to 2014, with the exception 

of Niagara County. The 2011 point source emissions for Niagara County was

noticeably higher than previous years because Somerset emitted approximately 10,024 

tons of SO2 that year. Since 2011, Somerset’s emissions have returned to pre-2011 

levels with 2014 emissions being less than half the 2011 emissions. (See Table 7). 

Table 4: SO2 Emissions Trends for Cattaraugus, Erie and Niagara Counties

County Source 

Category

2005

(tons)

2008

(tons)

2011

(tons)

2014*

(tons)

Cattaraugus Point 2.37 0.74 0.36 0.81

Non Point 955.50 405.37 275.64 186.87

On Road 49.51 9.01 10.02 10.02

Non Road 49.73 39.88 1.14 1.14

Total 1,057.11 455.00 287.16 198.84

Erie Point 19,897.63 7,422.75 4,924.42 3,456.11

Non Point 8,918.02 3,849.50 2,824.83 1,808.82

On Road 418.85 102.31 68.26 68.26

Non Road 508.49 78.13 8.49 8.49

Total 29,742.98 11,452.69 7,826.00 4,341.68

Niagara Point 4,255.33 5,058.62 10,759.85 5,855.06

Non Point 2,043.80 1,101.07 853.99 652.20

On Road 73.38 18.83 13.97 13.97

Non Road 379.13 21.26 2.42 2.42

Total 6,751.64 6,199.78 11,630.22 6,523.65

*2014 Point Source Emissions Data is preliminary data. 2014 Non-Point Emissions Data is projected. 2014 On-Road and NonRoad Emissions Inventories are under development, and, because they constitute a small fraction of the total inventory, were 

assumed constant from 2011 for purposes of this analysis.

14
Tables 5, 6 and 7 provide SO2 emissions for point sources in Cattaraugus, Erie and 

Niagara Counties respectively. Generally speaking, there is a downward trend in SO2

emissions from point sources in all three counties.

Table 5: SO2 Emissions (tons): Cattaraugus County Point Sources 

Facility 2007 2008 2009 2010 2011 2012 2013 2014

Indeck Olean Energy Center 1.42 0.74 0.46 0.71 0.36 0.33 0.35 0.81

Laidlaw Energy * 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Total 1.42 0.74 0.46 0.71 0.36 0.33 0.35 0.81

*Laidlaw Energy has not operated during the period of 2007-2014, but still has a valid Title V permit.

Table 6: SO2 Emissions (tons): Erie County Point Sources

Facility 2007 2008 2009 2010 2011 2012 2013 2014

Huntley Generating Station 10,612.50 6,852.60 6,043.92 6,041.41 4,315.60 2,715.50 3,218.00 3,192.00

PVS Chemical Solutions Inc* 198.38 121.73 96.32 147.88 138.14 109.06 139.29 163.11

3M Tonawanda* 52.96 64.78 41.50 48.90 37.08 43.32 45.33 47.68

Chaffee Landfill 17.99 44.43 47.31 42.54 48.66 49.78 46.39 45.61

Bird Island STP* 4.02 3.67 3.95 3.70 3.69 3.50 3.75 3.84

Tennessee Gas Pipeline Co Comp Stat 229 0.07 0.09 0.14 0.16 0.18 0.14 0.57 2.68

Indeck-Yerkes Energy Services 0.22 0.30 0.27 0.21 0.26 0.29 0.41 0.41

Tonawanda Engine Plant-GM Powertrain 0.26 0.23 0.09 0.20 0.15 0.19 0.17 0.28

Aurubis Buffalo Inc (aka. Luvata Buffalo Inc)* 0.18 0.18 0.15 0.17 0.18 0.18 0.27 0.21

Goodyear Dunlop Tires North America Ltd 153.83 0.20 3.36 0.16 0.16 0.15 0.17 0.19

International Imaging 0.02 0.02 0.02 0.05 0.02 0.02 0.02 0.03

Noco Energy Corp 94.48 16.11 0.32 0.10 0.17 0.05 0.03 0.03

Cello-Pack Corporation of Buffalo 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Whiting Door Manufacturing Corp 0.01 0.02 0.01 0.01 0.01 0.01 0.01 0.01

General Mills Operations LLC* 0.35 0.39 0.07 0.11 0.26 0.09 0.00

Buffalo State College 73.75 30.43 35.91 6.73 0.09 0.09 4.47 0.00

Concord Compressor Station* 0.00 0.12 0.00 0.01 0.01 0.02 0.10 0.00

Lackawanna Plant- Republic Steel* 0.43 0.46 0.29 0.37 0.39 0.41 0.36 0.00

E I Dupont Yerkes Plant* 0.01 0.00 0.00 0.06 1.49 0.34 0.10 0.00

Tonawanda Coke Corp* 353.70 285.85 127.22 378.02 378.01 347.30 401.39 0.00

Buffalo Terminal 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Unicell Body Company Inc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Sunoco Tonawanda Terminal 0.07 0.73 0.05 0.03 0.02 0.00 0.00 0.00

Henkel Corporation 0.01 0.01 0.01 0.00 0.00

QG Printing Corp 0.04 0.03 0.03 0.00

Arcelormittal Lacakawanna LLC 0.44 0.36 0.09 0.00 0.00

Great Lakes MDF 0.00 0.00 0.00 0.00

Quebecor World Buffalo Inc 44.89 0.04 0.03 0.00

Total 11,608.58 7,422.80 6,401.07 6,670.81 4,924.32 3,270.62 3,860.93 3,456.09

* 2014 emission statement is not technically complete (either data not entered or data may change)

15
Figure 2: Sources Emitting Greater Than 40 tons/year of SO2 near Huntley 

16
Table 7: SO2 Emissions (tons): Niagara County Point Sources 

Facility 2007 2008 2009 2010 2011 2012 2013 2014

Somerset (aka AES Somerset LLC) 4,261.62 3,937.74 5,076.81 7,618.01 10,024.21 5,653.36 5,722.67 4,817.21

Globe Metallurgical Inc 0.03 107.38 521.85 601.98 699.01 633.31 572.73

Niagara Generating Facility 544.30 925.70 451.80 1.55 0.00 7.22 48.92 244.03

Covanta Niagara LP 137.67 163.68 145.84 119.68 90.02 87.76 130.91 225.21

Model City Energy Facility 8.29 23.81 25.22 25.91 24.79 25.06 16.55 14.21

TAM Ceramics LLC 0.52 6.45 3.36 0.00 7.73 7.93 6.67 5.28

TN Gas Pipeline CO Comp. Stat. 230-C 0.23 0.14 0.03 0.02 0.00 0.32 4.34 4.31

Metaullics Systems Division of Pyrotek Inc 0.00 7.07 5.94 2.49 2.69 1.60

Dupont (aka Chemours) 0.23 0.22 0.71 0.79 0.03 0.02 0.02 0.19

GM (aka Delphi Thermal Systems) 0.00 0.08 0.00 0.00 0.08 0.09 0.10 0.10

Occidental Chemical Corp - Niagara Plant 0.00 0.01 0.01 0.00 0.00 0.00 0.40 0.07

Lockport Cogeneration Facility 21.32 0.39 0.36 0.00 0.03 0.07 0.02 0.05

Durez Niagara 0.00 0.00 0.20 0.00 0.00 0.03 0.03 0.03

Prestolite Electric NY Inc 0.02 0.02 0.62 0.03

Vandemark Chemical Inc 0.01 0.07 0.05 0.70 0.07 0.07 0.03 0.02

Washington Mills Electro Minerals 0.03 0.01 0.01 0.01 0.01 0.01 0.01 0.01

Modern Landfill Inc 0.25 0.19 0.03 0.33 4.63 0.23 0.05 0.00

Fortistar North Tonawanda Inc 0.24 0.00 0.00 0.70 0.33 1.27 0.91 0.00

Goodyear Chem Plant 0.00 0.00 0.01 0.00

Total 4,974.71 5,058.54 5,818.91 8,290.17 10,759.85 6,484.94 6,567.63 5,885.08

Figure 3: Sources Emitting Greater Than 40 tons/year of SO2 near Somerset

17
Airports also contribute to the total SO2 emissions, and are accounted for in the nonroad mobile inventory. The airport portion of the non-road inventory includes aircraft and 

ground support equipment. 2011 airport emissions are listed in Tables 8, 9 and 10. With 

the exception of Buffalo Niagara International Airport, which emitted 41.3797 tons of 

SO2 in 2011, the emissions from airports is very small. 

Table 8: Cattaraugus County Airports: 2011 Emissions Inventory

Airport SO2 (tons)

Cattaraugus County – Olean Airport 0.1900

Great Valley Airport 0.0511

Randolph Airport 0.0200

South Dayton Airport 0.0126

Giermek Executive Airport 0.0028

Olean General Heliport 0.0013

Hedge Hop Field Airport 0.0005

Reiss Game Farm Airport 0.0005

Berdick Field Airport 0.0004

Neverland Airport 0.0004

Ultralight Port Airport 0.0004

Campbell Field Airport *

Total 0.2800

*No data available

18
Table 9: Erie County Airports: 2011 Emissions Inventory

Airport SO2 (tons)

Buffalo Niagara International Airport 41.3797

Buffalo Airfield 0.3817

Akron Airport 0.3763

Buffalo Lancaster Regional Airport 0.3123

Hamburg Inc Airport 0.0837

Clarence Aerodrome 0.0694

Heussler Hamburg Airport 0.0481

Gowanda Airport 0.0251

Potoczak Airport 0.0022

Bertrand Chaffee Hospital Heliport 0.0013

Buffalo General Hospital Heliport 0.0013

Erie County Medical Center Heliport 0.0013

Gibralter Heliport 0.0013

Mercy Hospital Heliport 0.0013

South Buffalo Mercy Hospital Heliport 0.0013

Tennessee Gas Nr 2 Heliport 0.0013

Women and Childrens Hospital 

Heliport

0.0013

Woodlawn Beach State Park Heliport 0.0013

Ciszak Airport 0.0007

Gentzke Aeronautical Park Airport 0.0007

High Acres Airport 0.0007

Merkle Airport 0.0007

TTT Air 0.0007

Donnelly’s Airport 0.0006

Evans Airways Airport 0.0006

Hilltop Airport 0.0006

Knox Landing Airport 0.0006

Mesmer Airport 0.0006

Basher Field 0.0001

Treichler Farm Airport 0.0000

Total 42.6966

19
Table 10: Niagara County Airports: 2011 Emissions Inventory

Airport SO2

(tons)

Niagara Falls International Airport 1.5598

Royalton Airport 0.0420

North Buffalo Suburban Airport 0.0250

Hollands International Field Airport 0.0173

Best Western Red Jacket Inn Heliport 0.0013

Niagara Falls Memorial Parking Ramp Heliport 0.0013

Rainbow Air Heliport 0.0013

Ross Heliport 0.0013

St. Mary’s Heliport 0.0013

Flying F Airport 0.0006

Smith Airport 0.0006

Hibbards Airport 0.0005

Pendleton Airpark 0.0005

Shear Airport 0.0005

Taylor Johnson Airport 0.0005

Bassett Field Airport 0.0000

Bent-Wing Airport 0.0000

Cambira Airport *

Colonial Airport *

Lockport Cambria Airport *

Olcott Newfane Airport *

Total 1.6538

*No data available

20
Factor 3: Meteorology 

Meteorological data for AERMOD were processed using the AERMET meteorological 

pre-processor along with AERMINUTE and AERSURFACE. Five years of

meteorological data (2010-2014) from Buffalo Niagara International Airport were used to 

obtain the surface data, and upper air data from the same location were used to obtain 

the required vertical profiles. After 5 years of data were processed, both surface and 

upper air meteorological files were truncated to dates that fit the hourly emissions 

records (January 1, 2012 to December 31, 2014). 

An analysis was undertaken to estimate the degree to which the impacts of Huntley and 

other nearby SO2 sources are reflected in the measurements from the Tonawanda II 

monitor. Five-years of hourly wind data from Buffalo Niagara International Airport and 

Niagara Falls International Airport were used to create wind roses. The two wind roses 

are very similar at both locations with winds from the southwest quadrant being strongly 

dominant. 

Figure 4: Wind Roses from Buffalo Niagara International Airport and Niagara Falls

International Airport

The similarity between the wind roses from the two locations, as well as the generally 

flat terrain in the area, give confidence that the winds in the Tonawanda area follow a 

similar pattern. 

21
A pollution rose was created using a combination of hourly SO2 concentrations from the 

Tonawanda II monitor and hourly winds from the Buffalo Niagara International Airport. 

Figure 5: SO2 Pollution Wind Rose for Tonawanda II Monitor

This rose shows a strong influence from Huntley and nearby SO2 sources on the SO2

levels at the ambient monitor site. Huntley and the other nearby significant SO2 sources 

are located to the southwest and south-southwest of the monitor site at a distance of 2-

5 km. 

Average SO2 concentrations at the monitor when winds are from the southwest or 

south-southwest are over 3 ppb. By comparison, average SO2 concentrations for winds 

from all quadrants other than southwest are near or below 2 ppb. When winds are from 

the south-southwest (195° to 225°), higher SO2 concentrations correlate with higher 

wind speeds. This provides additional evidence that the impacts of the nearby sources 

are reflected in the monitor data. The stronger winds give the SO2 plumes less time to 

disperse before they arrive at the monitor site, resulting in higher impacts.

For Somerset, five years of meteorological data (2010-2014) from Niagara Falls 

International Airport were used to obtain the surface data, and upper air data from 

22
Buffalo Niagara International Airport were used to obtain the required morning sounding 

profiles. After 5 years of data were processed, both surface and upper air 

meteorological files were truncated to dates that fit the hourly emissions records 

(January 1, 2011 to December 31, 2013). Winds are predominantly from the southwest.

The hourly SO2 data from the Niagara Falls monitor for the period 2010 – 2012 was 

processed to obtain 3-year averages of the 99th percentile concentrations by season 

and hour-of-day pursuant to EPA’s 2011 Memorandum by Tyler Fox entitled “Additional 

Clarification Regarding Application of Appendix W Modeling Guidance for the 1-hour 

NO2 National Ambient Air Quality Standard”. The processed data were included in 

AERMOD in order to add background values to calculated SO2 impacts. Note that the 

Niagara Falls monitor discontinued measuring SO2 beyond 2012 making this period the 

most recent SO2 background data for our modeling analysis. The more urban setting of 

the monitor as compared to the facility as well as the data being a year older when 

trends have been coming down for SO2 makes this a conservative choice of a 

representative background data. The location of the ambient monitor relative to 

Somerset Station is shown in Figure 3. 

DEC determined that it was not necessary to include any nearby sources in Somerset’s 

modeling analysis because the nearest facility emitting greater than 40 tons/year is 

located more than 40 km from Somerset. Additionally, the background monitor selected 

is conservative and reflects the contributions of the nearby sources to the ambient SO2

concentrations.

A complete discussion of meteorology can be found in the modeling reports for Huntley 

and Somerset included in this report as Appendix A and Appendix B respectively.

23
Factor 4: Geography and Topography 

The Niagara Frontier is most commonly referred to as the land bordering the eastern 

Niagara River and southern shores of Lake Erie and Lake Ontario and is part of the 

region known as Western New York State. The Niagara Frontier also forms the eastern 

part of the Great Lakes North Coast, while its southeastern boundary forms what is 

known as ski country. 

There are no mountain ranges or other air basin boundaries that have a distinguishable 

effect on the Niagara Frontier.

24 
Factor 5: Jurisdictional Boundaries 

The United States Office of Management and Budget (OMB) delineates metropolitan 

and micropolitan statistical areas according to published standards that are applied to 

Census Bureau data. The general concept of a metropolitan or micropolitan statistical 

area is that of a core area containing a substantial population nucleus, together with 

adjacent communities having a high degree of economic and social integration with that 

core. Currently delineated metropolitan statistical areas (MSAs) and micropolitan 

statistical areas (mSAs) are based on application of 2010 standards (which appeared in 

the Federal Register on June 2010) to 2010 Census and 2006-2010 American 

Community Survey data. Current MSA and mSA delineations were announced by OMB 

effective February 2013.

Adjacent MSAs and mSAs may become the components of a set of complementary 

areas called Combined Statistical Areas (CSAs). Historically, EPA has used the CSA as 

the starting point for consideration when developing designation recommendations. For 

purposes of this revised designation recommendation, DEC is evaluating the BuffaloCheektowaga, NY CSA, which is comprised of the Buffalo-Cheektowaga-Niagara Falls, 

NY MSA (Erie and Niagara Counties) and the Olean, NY mSA (Cattaraugus County).

25
Recommendations 

DEC recommends that the Buffalo-Cheektowaga, NY CSA (Cattaraugus, Erie and 

Niagara Counties) be designated “attainment” for the 1-hour SO2 NAAQS because: 

1. design values calculated from actual monitoring data demonstrate that all

monitors in both Erie and Niagara counties, as well as the next closest monitors

located in Chautauqua, Monroe and Steuben counties, are well below the

NAAQS of 75 ppb and trending downward, and

2. dispersion modeling performed to assess the attainment status of the area

around Huntley and Somerset, in the context of EPA’s 1-hour SO2 Data

Requirements Rule, demonstrates that Huntley and Somerset do not cause or

contribute to a violation of the 1-hour SO2 NAAQS.

26
APPENDIX A: Air Quality Modeling for Huntley Generating Station

27

Air Quality Modeling 

for 

Huntley Generating Station

Prepared by Impact Assessment and Meteorology Section

New York State Department of Environmental Conservation

July 2015
TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 FACILITY DESCRIPTION 

2.1 FACILITY LOCATION 

2.2 SOURCE PARAMETERS AND EMISSION RATES 

3.0 AIR DISPERSION MODELING ANALYSIS 

3.1 METEOROLOGICAL DATA 

3.2 RECEPTOR GRID 

3.3 AMBIENT BACKGROUND DATA 

4.0 MODELING RESULTS 

5.0 CONCLUSIONS

Appendix A – Modeling Files (on disc)
1.0 INTRODUCTION

The purpose of this document is to present the results of the modeling performed 

to assess the attainment status of the area around Huntley Generating Station (Huntley)

in the context of the 1-hour SO2 Data Requirements Rule (DRR).

The air dispersion modeling methodology that was followed is based on policies 

and procedures contained in the USEPA Guideline on Air Quality Models (40 CFR 

Appendix W) and the New York State Department of Environmental Conservation’s 

(NYSDEC) Air Quality Modeling Procedures as outlined in DAR-10 / NYSDEC Guidelines 

on Dispersion Modeling Procedures for Air Quality Impact Analysis, modified by the SO2

NAAQS Designations Modeling Technical Assistance Document (Modeling TAD) where 

applicable.

The steps taken to conduct the air-dispersion modeling analyses are summarized below:

• Compile information on the parameters and characteristics for Huntley;

• Obtain and prepare hourly emissions data for HGS for the period 2012-2014;

• Develop a comprehensive receptor grid to capture the maximum offsite impacts

from the main stack;

• Process three years of meteorological data (as available from a local,

representative meteorological station) using the meteorological pre-processor

AERMET along with AERMINUTE and AERSURFACE;

• Obtain and prepare appropriate SO2 background data from the nearest

representative monitor;

• Complete an ambient air quality modeling analysis using USEPA’s regulatory

dispersion model, AERMOD (version 14134);

• Summarize the results in tabular format and compare the results with the 1-hour

SO2 ambient air quality standard.
The next section provides a description of the facility and the emissions included

in the modeling. Model selection and the methodology used in the modeling are described 

in Section 3. The modeling results are presented in Section 4. 
2.0 FACILITY DESCRIPTION

The Huntley Power Station is located on the shore of the Niagara River in the 

Town of Tonawanda, Erie County, NY. The electrical generating facility consists of two 

pulverized coal, dry-bottom, tangential-fired boilers that primarily fire sub-bituminous 

coal and can produce up to 400 megawatts of electricity. The boilers fire distillate oil 

during various startup modes. Boilers 67 and 68 have a maximum heat input of 1836 

MMBtu/hr each and exhaust combustion gases through a common stack. Steam from 

each boiler is used to power a dedicated steam turbine-generator set that is capable of 

generating 200 megawatts of electricity. Combustion Engineering manufactured unit 67 

in 1957 and unit 68 in 1958. Units 67 and 68 are tangentially fired dual furnace boilers, 

where there are two separate fire boxes and a common primary steam header for each 

boiler. For each boiler one furnace produces the superheated steam while the other 

furnace creates reheat steam. Both units use fabric filters to control particulate 

emissions, dry sorbent injection to control acid gases, selective noncatalytic reduction 

(SNCR) to control nitrogen oxide emissions, and activated carbon injection to control 

mercury emissions. Each emission control system is used as needed to meet the 

appropriate emission limits.
2.1 FACILITY LOCATION

Huntley Generating Station is located approximately 10.5 km north-northwest of 

Buffalo, NY. The plant is on the east bank of the Niagara River, adjacent to the southern 

end of Grand Island. Figure 2-1 displays an aerial image of the area around Huntley

Generating Station, with the facility’s property outlined in yellow. Figure 2-2 is a photo of 

the facility, showing the operating stack on the left. The other stack in the photo is no 

longer in use. The Universal Transverse Mercator (UTM83) coordinates of the

operational stack are approximately 668784.63E, 4759614.9N (Zone 17). The base 

elevation of the stack is 174.9 m.

Figure 2-1: Aerial Photograph of Huntley Generating Station
Figure 2-2: Photograph of Huntley Generating Station
Figure 2.3 – Detailed Aerial View
2.2 SOURCE PARAMETERS AND EMISSION RATES

Source parameters and emission rates for the two boilers at the facility were 

obtained from Roger Caiazza of the Environmental Energy Alliance of New York. 

The hourly values of SO2 emission rates, stack flow rates and stack temperature 

for 2012-2014 were received in three excel files and subsequently converted into units 

and file format appropriate for AERMOD use. The stack height is 106.7 m, and the exit 

diameter of the stack is 5.72 m.
2.3 BUILDINGS and FENCELINE

Building height information was obtained from Patrick Yough, Environmental 

Manager at NRG. The building footprints used for downwash calculations, as well as the 

fenceline, are based on the Google Earth image of the facility. BPIP-Prime was run to 

prepare the building files needed for AERMOD run.

Figure 2-4: Building Layout and Fenceline used for Analysis
3.0 AIR DISPERSION MODELING ANALYSIS

The Modeling TAD describes two types of modeling: using the allowable emission 

rate along with 5-years of meteorological data and GEP stack height, or, as a refinement, 

3-years of actual hourly emissions data along with 3-years of concurrent meteorological 

data, using the true stack height regardless of GEP. For this modeling analysis, the 

second option was exercised. Actual hourly emissions data obtained from the facility were 

matched with 3 years of concurrent surface and upper-air meteorological data from 

Buffalo Niagara International Airport to run AERMOD version 14134. 
3.1 METEOROLOGICAL DATA

Meteorological data for AERMOD were processed using the AERMET (version 

14134) meteorological pre-processor along with AERMINUTE (version 14337) and 

AERSURFACE (version 13016). Five years of meteorological data (2010-2014) from the 

Buffalo Niagara International Airport were used to obtain the surface data, and upper air 

data from the same location were used to obtain the required vertical profiles. After 5 

years of data were processed, both surface and upper air meteorological files were

truncated to dates that fit the hourly emissions records (1/1/2012 to 12/31/2014).

Prior to processing the meteorological data with AERMET, the land-use within 1 

km of the meteorological tower at Buffalo Niagara International Airport was analyzed 

using the AERSURFACE pre-processor. AERSURFACE uses land cover data from the 

National Land Cover Data (NLCD) 1992 database to determine three key surface 

parameters needed for modeling: surface roughness albedo, and the Bowen ratio. For 

this modeling, the 1-km radius circular area centered at the meteorological station site 

was divided into 12 equal 30-degree sectors. For the Bowen ratio calculations, the land 

use values can be linked to three categories of surface moisture corresponding to 

average, wet, and dry conditions – depending on the site and meteorological data period. 

For this site and data period, the “average” surface moisture option was applied.

The AERSURFACE results are used as input into the AERMET meteorological 

data processor. Additionally, 1-minute ASOS wind data, collected at the Buffalo airport

meteorological tower, were processed using the AERMINUTE pre-processor for 

AERMET. Figure 3-1 presents a wind rose for the 3 years of meteorological data 

processed for the modeling analysis. Figure 3-2 shows the relative locations of Huntley 

Generating Station, the meteorological data collection site, and the ambient background 

monitor (see Section 3.3) used in the modeling. 
Figure 3-1: Wind Rose for Buffalo Niagara International Airport
Figure 3-2: Locations of Facility, SO2 Monitor, and Weather Station
3.2 RECEPTOR GRID

A comprehensive polar receptor grid extending to 20 km from the Huntley

Generating Station was used in the AERMOD modeling to assess maximum ground-level 

SO2 concentrations. The receptor grid consisted of the following receptor spacing: 

• 100 m spacing extending from the source to 2 km;

• 250 m spacing extending from 2 km to 5 km;

• 500 m spacing extending from 5 km to 10 km; and

• 1000 m spacing extending from 10 km to 20 km

Receptors were placed on 36 radials 10 degrees apart and the grid was centered on the

emission source. Receptors within the Huntley fenceline were eliminated and special 

receptors were placed along the fenceline at every 25 m. This grid contained a total of 

1369 receptors.

The base elevation and hill scale parameters for all receptors were assigned using 

AERMAP (version 11103) based on data obtained from the National Elevation Dataset 

website. The receptor grid used in modeling is shown in Figure 3-3 below.
Figure 3-3 
3.3 AMBIENT BACKGROUND DATA

An analysis was undertaken to estimate the degree to which the impacts of Huntley

and other nearby SO2 sources are reflected in the measurements from the Tonawanda II

(also known as Tonawanda – Brookside Terrace) ambient air monitoring station. Fiveyears of hourly wind data from Buffalo-Niagara International Airport and Niagara Falls 

International Airport were used to create wind roses. The two wind roses are very similar 

(Fig. 3-4) -- at both locations, winds from the southwest quadrant are strongly dominant. 

The similarity between the wind roses from the two locations, as well as the generally flat 

terrain in the area, give confidence that the winds in the Tonawanda area follow a similar 

pattern. A pollution rose (Fig. 3-5) was created using a combination of hourly SO2

concentrations from the Tonawanda II monitor and hourly winds from the Buffalo-Niagara 

International Airport. This rose shows a strong influence from Huntley and nearby SO2

sources on the SO2 levels at the ambient monitor site. Huntley and the other nearby 

significant SO2 sources are located to the southwest and south-southwest of the monitor 

site at a distance of 2-5 km (map, Fig. 3-7). Average SO2 concentrations at the monitor 

when winds are from the southwest or south-southwest are over 3 ppb. By comparison, 

average SO2 concentrations for winds from all quadrants other than southwest are near 

or below 2 ppb. Table 3-1 shows that when winds are from the south-southwest (195° to 

225°), higher SO2 concentrations correlate with higher wind speeds. This provides 

additional evidence that the impacts of the nearby sources are reflected in the monitor 

data. The stronger winds give the SO2 plumes less time to disperse before they arrive at 

the monitor site, resulting in higher impacts.
Fig. 3-4: Wind Roses from Buffalo and Niagara Falls airports

Fig. 3-5: SO2 pollution rose for Tonawanda II monitor site (Buffalo airport winds) 
Labels indicate rounded average SO2 concentration for the indicated wind 

direction. Color bars indicate the frequency of the indicated concentration for that wind 

direction.

Table 3-1: Tonawanda 2012-2014 SO2 concentration as a function of wind speed

 and direction

SO2

Concentration

Wind Direction (degree)

0 30 60 90 120 150 180 210 240 270 300 330

Wind

Speed

Knots

0-1 1.76 1.35 1.77 1.65 1.67 2.47 1.48 1.8 1.53 1.59 2 1.45

1-4 1.68 1.42 1.56 1.44 1.35 1.41 1.61 1.83 2.55 1.94 1.87 1.48

4-7 2.38 1.54 2.22 2.12 1.94 1.8 2.12 2.76 2.96 2.24 2.16 1.68

7-11 3.01 1.85 2.53 2.73 2.7 1.57 2.14 3.97 3.23 2.55 1.82 1.52

11-17 2.93 1.3 1.5 2.55 4.49 2.85 2.9

Since the monitor data already to a large degree reflect the contributions of Huntley

and nearby sources to the SO2 concentration, it was not necessary to include emissions 

from sources other than Huntley in the modeling. All of the available monitor data was 

used in calculating the seasonal/hourly background values, including the time periods 

when the nearby sources were impacting the monitor. As such, the modeled 

concentrations, which include seasonal/hourly 99th percentile background, can be 

expected to be highly conservative. 

The hourly SO2 data from the Tonawanda II monitor for the period 2012 - 2014 

were processed to obtain 3-year averages of the 99th percentile concentrations by season 

and hour-of-day. These calculations were made according to the method specified in

EPA’s 2011 Memorandum by Tyler Fox, “Additional Clarification Regarding Application 

of Appendix W Modeling Guidance for the 1-hour NO2 National Ambient Air Quality 

Standard”. Missing data were treated conservatively by using the first-highest value 

(rather than the second-highest) for season/hour combinations with less than 82.2% data 

completeness. The processed data (shown in figure 3-6) were included in the AERMOD

input file in order to add background values to calculated SO2 impacts. 
Figure 3-6: 

The design value, depicted here by the gray line, is the mathematically determined 

pollutant concentration at a particular site that is used for comparison to the National 

Ambient Air Quality Standard (NAAQS) in order to assure attainment. The design value 

may be calculated based on ambient measurements observed at a local monitor over a 

three year period, or on model estimates.
Figure 3-7: Map of Monitor Location relative to SO2 Sources
4.0 MODELING RESULTS

Table 4-1 shows AERMOD calculated impacts that include seasonally-based hourly

background concentrations. 

Table 4-1: Modeled 3-year Average Impacts

Pollutant Averaging 

period

4th highest 

concentration, 

Huntley 

contribution

4th highest 

concentration, 

including 

background

SO2 NAAQS

(ppb) 

SO2 1 hour 44.1 ppb

(115.5 μg/m3) 

54.3 ppb

(142.3 μg/m3) 

75

Figure 4-1 shows the nearby impacts of the facility (not including background) on 

the 1-hour SO2 design value over the 2012-2014 period in μg/m3. The maximum impact 

is located at the southeastern boundary of the facility’s property.
Figure 4-1: Modeled Impact of Huntley on 1-hour SO2 Design Value
5.0 CONCLUSIONS

The modeling performed demonstrates that Huntley Generating Station does not

cause or contribute to a violation of the 1-hour SO2 NAAQS. Therefore, an attainment

designation for the area around the station is recommended. 
APPENDIX B: Air Quality Modeling for Somerset Station

28

Air Quality Modeling for Somerset Station

Prepared by Impact Assessment and Meteorology Section

New York State Department of Environmental Conservation

July 2015
TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 FACILITY DESCRIPTION 

2.1 FACILITY LOCATION 

2.2 SOURCE PARAMETERS AND EMISSION RATES 

3.0 AIR DISPERSION MODELING ANALYSIS 

3.1 METEOROLOGICAL DATA 

3.2 RECEPTOR GRID 

3.3 AMBIENT BACKGROUND DATA /NEARBY SOURCES

4.0 MODELING RESULTS 

5.0 CONCLUSIONS

6.0 REFERENCES

Appendix A – Modeling files (on disc)
1.0 INTRODUCTION

The purpose of this document is to present the results of the modeling performed 

to assess the attainments status of the area around Somerset Station in the context of 

the 1-hour SO2 Data Requirements Rule (DRR).

The air dispersion modeling methodology that was followed is based on policies 

and procedures contained in the USEPA Guideline on Air Quality Models (40 CFR 

Appendix W) and the New York State Department of Environmental Conservation’s 

(NYSDEC) Air Quality Modeling Procedures as outlined in DAR-10 / NYSDEC Guidelines 

on Dispersion Modeling Procedures for Air Quality Impact Analysis, modified by the SO2

NAAQS Designations Modeling Technical Assistance Document (Modeling TAD) where 

applicable.

The steps taken to conduct the air-dispersion modeling analyses are summarized 

below: 

• Compile information on the parameters and characteristics for Somerset Unit 1;

• Obtain and prepare hourly emissions data for Somerset Unit 1 for the period 2011-

2013;

• Develop a comprehensive receptor grid to capture the maximum offsite impacts

from the main stack;

• Process five years of meteorological data (as available from a local, representative

meteorological station) using the meteorological pre-processor AERMET along

with AERMINUTE and AERSURFACE;

• Obtain and prepare appropriate SO2 background data from the nearest

representative monitor;

• Complete an ambient air quality modeling analysis using USEPA’s regulatory

dispersion model, AERMOD (version 14134);

• Summarize the results in tabular format and compare the results with the 1-hour

SO2 ambient air quality standard.
The next section provides a description of the facility and the emissions included

in the modeling. Model selection and the methodology used in the modeling are described 

in Section 3. The modeling results are presented in Section 4, and references are 

provided in Section 5.
2. FACILITY DESCRIPTION

Somerset Generating Station, located in Somerset, NY, is a 675 megawatt (MW) 

electric generating facility. The primary fuels combusted by the main boiler are bituminous 

coal and petroleum coke (petcoke). The coal may contain a latex dust suppressant as 

supplied. Associated with the boiler is a coal handling system (unloading and conveying 

coal and petroleum coke, etc.), a No. 2 fuel oil system (tanks and piping) which is used 

for startup and flame stabilization, a limestone handling system (unloading and 

conveying, etc.), and other miscellaneous sources and activities related to the operation 

of an electric generating station. The station also includes two oil fired boilers that are 

used for start-up of the main boiler and one diesel-fired emergency electric generator.

2.1 FACILITY LOCATION

Somerset Generating Station is located approximately 35 miles north-northeast of 

Buffalo, NY and 50 miles west-northwest of Rochester, NY. The plant is on the south 

shore of Lake Ontario. Figure 2-1 displays an aerial image of the area around Somerset 

Generating Station. Universal Transverse Mercator (UTM83) coordinates of the center of 

the plant are approximately 694200E, 4803100N (Zone 17). The base elevation of the

main stack is 292 feet (89 m). Figure 2-2 shows a closer areal look at the facility and 

buildings layout. Both photos were provided to us by Environmental Resources 

Management (ERM).
Figure 2-1 Aerial Photograph of Somerset Generating Station
Figure 2-2 Somerset Buildings Layout - Areal View; Building key: 1-Boiler 

buiding; 2-Turbine building; 3-Administation building; 4-Water prep; 5-Water 

treatment; 6-EPRI; 7-ESP; 8-ID fan; 9-16 tiers of FDD building; 17-LCRH; 18-CCH
2.2 SOURCE PARAMETERS AND EMISSION RATES

Source parameters and emission rates for the Main boiler at the facility (Unit 1) 

were obtained from John Marabella, Environmental Director at the Upstate New York 

Power Producers. The hourly values of SO2 emission rates, stack flow rates and stack 

temperature for 2011-2013 were received in three excel files and subsequently converted 

into units and file format appropriate for AERMOD use. For hours where the provided files 

contained missing data (N/A values) numbers were substituted with following criteria:

1) If all three variables (SO2 emission rate, stack flow and temperature) were ‘N/A’ it

was assumed the unit did not operate and all three were replaced by zeros.

2) If any of the three variables was measured (not ‘N/A’) it was assumed that only the

CEM instrument was off and all three were replaced with the most conservative

(maximum) value measured over the three years (SO2 emission of 6010.46 lb/hr

and corresponding flow rate of 108679.2 kscfh and T=123.3F

For quality assessment purposes, the hourly emissions data were reviewed and 

compared to Clean Air Market Data (CAMD). The Somerset Unit 1 stack height is 186.84 

m and the stack exit diameter is 8.129 m. 

There are four additional sources of SO2 emissions at Somerset: two oil-fired 

auxiliary boilers and one diesel-fueled emergency engine. In accordance with the facility’s 

Title V permit, the auxiliary boilers do not operate when the main boiler is online and 

therefore can be excluded from cumulative modeling with the Unit 1 boiler. The 

emergency generator testing can also be excluded from the modeling based on USEPA 

guidance provided in the 1 March 2011 memorandum “Additional Clarification Regarding 

Application of Appendix W Modeling Guidance for the 1-hour NO2 National Ambient Air 

Quality Standard” for intermittent sources such as emergency generators. As noted in the 

clarification letter this interim guidance can be extended to 1-hour SO2 applications. 

Therefore, both auxiliary boilers and emergency generators were excluded from this 

modeling. 
2.3 BUILDINGS and FENCELINE

Building information was obtained from a BPIP-Prime input file received from John 

Marabella. The building locations were verified based on Google Earth image of the 

facility as was the fenceline. BPIP-Prime was re-run to prepare the building files for 

AERMOD run. Structures included in Somerset BPIP-Prime run and GEP analysis are 

shown in Figure 2-3.
Figure 2-3 Structures Included in Somerset GEP Analysis
3.0 AIR DISPERSION MODELING ANALYSIS

The Modeling TAD describes two types of modeling: using the allowable emission 

rate along with 5 years of meteorological data and GEP stack height, or, as a refinement, 

3 years of actual hourly emissions data along with 3 years of concurrent meteorological 

data along with the true stack height regardless of GEP. In this modeling analysis, 

AERMOD version 14134 was run for the following two scenarios:

• Three years of hourly emissions data obtained from the facility (as described in 

Section 2.2) were matched with 3 years of concurrent meteorological data from 

Niagara Falls/Buffalo airports and modeled with the actual stack height (186.84m).

• A fixed emission rate based on a permit limit to comply with the Mercury and Air

Toxics Standards (MATS) was modeled with 5 years of meteorological data and 

the GEP stack height of 170.36m. Modeling parameters and emission rates for 

Unit 1 stack were obtained from 26 April 2011 effective Title V permit (9-2938-

00003/00002). This included the SO2 emission rate of 1,256 lb/hr, stack exhaust 

temperature of 405.15K and exit velocity 16.11m/s.

3.1 METEOROLOGICAL DATA

Meteorological data for AERMOD were processed using the AERMET (version 

14134) meteorological pre-processor along with AERMINUTE (version 14337) and 

AERSURFACE (version 13016). Five years of meteorological data (2010-2014) from the 

Niagara Falls International Airport were used to obtain the surface data, and upper air 

data from Buffalo-Niagara International Airport were used to obtain the required morning

sounding profiles. After 5 years of data were processed, both surface and upper air 

meteorological files were truncated to dates that fit the hourly emissions records (1/1/2011 

to 12/31/2013).

Prior to processing the meteorological data with AERMET, the land-use within 1 

km of the meteorological tower at Niagara Falls International Airport was analyzed using 

the AERSURFACE pre-processor. AERSURFACE uses land cover data from the 

National Land Cover Data (NLCD) 1992 database to determine three key surface 
parameters needed for modeling: surface roughness, albedo and the Bowen ratio. For 

this modeling, the 1-km radius circular area centered at the meteorological station site 

was divided into 12 equal 30-degree sectors. For the Bowen ratio calculations, the land 

use values can be linked to three categories of surface moisture corresponding to 

average, wet, and dry conditions – depending on the site and meteorological data period. 

For this site and data period, the “average” surface moisture option was applied.

The AERSURFACE results are used as input into the AERMET meteorological 

data processor. Additionally, 1-minute ASOS wind data, collected at the Niagara Falls 

meteorological tower, were processed using the AERMINUTE pre-processor for 

AERMET. Figure 3-1 presents a wind rose for the 3 years of meteorological data 

processed for the modeling analysis. Figure 3-2 shows the relative locations of Somerset 

Generating Station, the meteorological data collection site, and the ambient background 

monitor (see Section 3.3) used in the modeling.
Figure 3-1 Wind rose for Niagara Falls International Airport (2011-2013)
Figure 3-2 Relative Locations of Somerset Generating Station, Niagara Falls 

International Airport, and SO2 Ambient Monitor
3.2 RECEPTOR GRID

A comprehensive polar receptor grid, extending to 20 km from the Somerset 

Generating Station was used in the AERMOD modeling to assess maximum ground-level 

SO2 concentrations. The receptor grid consisted of the following receptor spacing: 

• 100 m spacing extending from the source to 2 km;

• 250 m spacing extending from 2 km to 5 km;

• 500 m spacing extending from 5 km to 10 km; and

• 1000 m spacing extending from 10 km to 20 km

Receptors were placed on 36 radials 10 degrees apart and the grid was centered on the 

Unit1 emission source. Receptors within the Somerset fenceline were eliminated and 

special receptors were placed along the fence line at every 50 m. This grid contained a 

total of 1723 receptors.

The base elevation and hill scale parameters for all receptors were assigned using 

AERMAP (version 11103) based on data obtained from the National Elevation Dataset 

website. The receptor grid used in modeling is shown in Figure 3-3. 
Figure 3-3 Receptors used in the Somerset Air Dispersion Modeling analysis
3.3 AMBIENT BACKGROUND DATA

The hourly SO2 data from the Niagara Falls monitor for the period 2010 – 2012

was processed to obtain 3-year averages of the 99th percentile concentrations by season 

and hour-of-day following EPA’s 2011 Memorandum by Tyler Fox “Additional Clarification 

Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2 National 

Ambient Air Quality Standard”. The processed data (shown in Figure 3-4) were included 

in AERMOD in order to add background values to calculated SO2 impacts. Note that the 

Niagara Falls monitor discontinued measuring SO2 beyond 2012 making this period the

most recent SO2 background data for our modeling analysis. The more urban setting of 

the monitor as compared to the facility as well as the data being a year older when trends 

have been coming down for SO2 makes this a conservative choice of a representative 

background data. 

Figure 3-4 Niagara Falls One-hour SO2 concentrations for 2010-2012 period. The design 

value, depicted here by the gray line (DV), is the mathematically determined pollutant concentration at a particular site that is used for 

comparison to the National Ambient Air Quality Standard (NAAQS) in order to assure attainment. The design value may be calculated 

based on ambient measurements observed at a local monitor over a three year period, or on model estimates.
Figure 3-5 shows a map with relative locations of Somerset Generating Station, 

the Niagara Falls SO2 monitor as well as any Title V facilities emitting more than 40 

tons/year of SO2 within a 50 km radius of Somerset Station. We determined that it was 

not necessary to include any nearby sources in our modeling analysis since the nearest 

facility emitting greater than 40 tons/year is located more than 40 km from Somerset 

Station. In addition, the background monitor selected is conservative and reflects the 

contributions of the nearby sources to the ambient SO2 concentrations. 

Figure 3-5 Niagara Falls Monitor Location Relative to Sources Emitting more than 

40 tons/yr of SO2 within 50 km radius of Somerset Generating Station. 
4.0 MODELING RESULTS

Table 4-1 shows AERMOD calculated impacts for the scenarios including hourly 

emission values and seasonally-based hourly background concentrations. These results 

were calculated with the actual stack height and downwash option in AERMOD. 

Table 4-1 Modeled 3-year Average Impacts

Pollutant Averaging 

period

4th highest 

concentration, 

Somerset 

contribution

4th highest 

concentration, 

including 

background 

SO2 NAAQS

SO2 1 hour 35.0 ppb

(91.9 μg/m3) 

42.6 ppb 

(111.7 μg/m3) 

75 ppb

(196 μg/m3) 

Figure 4-1 shows the nearby impacts of the facility (not including background) on 

the 1-hour SO2 design value over the 2011-2013 period in μg/m3. The highest impacts 

occur just northeast and southeast of the facility’s property. 
Figure 4-1 Modeled Impact of Somerset Station 1-hour SO2 over 2011-2013.

AERMOD was also applied with single emission value (based on the MATS emission 

limit), GEP stack height and 5 years of meteorological data to determine the future

potential maximum impacts from the Somerset Station. The resulting maximum modelpredicted 1-hour SO2 impact of Somerset Unit 1 was 34.2 μg/m3 (13.0 ppb). Even with 

the ambient background concentration added to the Unit 1 impacts, the total 

concentrations are well under 50% of the NAAQS. 
5.0 CONCLUSIONS

The modeling performed demonstrates that Somerset Generating Station does not

cause or contribute to a violation of the 1-hour SO2 NAAQS. Therefore, an attainment

designation for the area around the station is recommended. 
6.0 REFERENCES

New York State Department of Environmental Conservation: DAR -10 / NYSDEC 

Guidelines on Dispersion Modeling Procedures for Air Quality Impact Analysis, May, 2006

U.S. Environmental Protection Agency: (USEPA 2011) USEPA memo entitled “Additional 

Clarification Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2 

National Ambient Air Quality Standard”, USEPA, Office of Air Quality Planning and 

Standards, Raleigh, NC. 1 March 2011.

U.S. Environmental Protection Agency: (USEPA 2009) AERMOD Implementation Guide, 

AERMOD Implementation Workgroup. 19 March 2009.

U.S. Environmental Protection Agency: (USEPA 2005) Guideline on Air Quality Models 

(GAQM, 40CFR Appendix W), November, 2005