Technical Support Document (TSD)

For the Modeling Portions of the Document Entitled "Lower Beaver Valley Area Nonattainment Area for
the 2008 Lead National Ambient Air Quality Standard", dated January 2015

TSD Prepared June 2015

Timothy A. Leon Guerrero

Office of Air Monitoring and Analysis, 3AP40

U.S. Environmental Protection Agency, Region 3

1650 Arch Street

Philadelphia, Pennsylvania 19103

Reviewed by Alice Chow, Associate Director,

Office of Air Monitoring and Analysis (3AP40)

Date SignedTechnical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 1 of 11 Purpose of the Technical Support Document

This Technical Support Document (TSD) describes the Environmental Protection Agency’s (EPA’s) evaluation of the air dispersion modeling for the Lower Beaver Valley lead nonattainment area. The purpose of this TSD is to provide more detailed information than can be contained in the official notice published in the Federal Register. Readers who need more information than we provide in this TSD or want to review the modeling in more detail are encouraged to review the final State Imple mentation Plan (SIP) submitted by the Commonwealth of Pennsylvania 1

.

Introduction and Regulatory Framework

On October 15, 2008, the U.S. Environmental Protection Agency (EPA) promulgated a revised health

- based primary and secondary N ational A mbient A ir Q uality S tandard s (NAAQS) for lead. The 2008 primary lead NAAQS, which is set at a level to protect public health from adverse effects, is 0.15 micrograms per cubic meter (μg/m 3 ). The secondary standard, which is set at a level requisite to protect the publ ic welfare from adverse effects, is identical to the primary standard.

In November of 2010, the US EPA designated three (3) areas in Pennsylvania as lead nonattainment areas based on 2007

- 09 air quality monitoring data. Vanport and Potter t ownships in Beaver County, PA were designated as the Lower Beaver Valley Nonattainment Area. In January of 2010, the Pennsylvania Department of Environmental Protection ( PA DEP ) commenced operation of a ne w source

- oriented lead monitor referred to as the Beaver Va lley monitor ( AQS 4 2

- 007

- 0007) in Center Township, Beaver County , PA . This new monitor was associated with the Horsehead Monaca Smelter facility in accordance with the network design requirements for the 2008 lead NAAQS

. I n 2011 t he US EPA revised the lead NAAQS nonattainment area based on the 2008

- 2010 monitoring data by adding Center Township to the nonattainment area

. Therefore, effective December 31, 2011, the Lower Beaver Valley

n onattainment a rea was comprised of Vanport, Potter and Ce nter t ownships all located in Beaver County, PA. Figure 1 displays the Lower Beaver Valley, PA nonattainment a rea along with the lead monitor sites

.

1 http://www.elibrary.dep.state.pa.us/dsweb/View/Collection

- 12349Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 2 of 11 Figure 1. The municipal units and lead monitoring sites that are part of the Lower Beaver Valley, PA l ead n onattainment a rea

Lead SIP regulations found at 40 CFR 51.117 require states to employ atmospheric dispersion modeling for the demonstration of attainment for areas in the vicinity of point sources listed in 40 CFR 51.117(a)(1 ). Meteorological and o ther data are ne eded t o complete th e required air dispersion modeling

. EPA notes that 40 CFR 51.117(a) provides that states must include, as a part of their attainment modeling demonstration, an analysis showing that the SIP will attain and maintain the s tandard in areas in the vicinity of certain point sources that are emitting significant emissions of lead and also in ‘‘any other area that has lead air concentrations in excess of the national ambient air quality standard concentration. ” In doing the anal ysis, required under 40 CFR 51.117(a)(2), EPA expects the state will take into consideration all sources of lead emissions within the nonattainment area that may be required to be controlled.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 3 of 11 Overview of Commonwealth of Pennsylvania’s General Modeling Approach

PA DEP examined data from a meteorological monitoring tower located near the Bruce Mansfield Power Station to determine rough transport winds in the Lower Beaver Valley nonattainment area . This meteorological tower is operated by the Beaver Vall ey Nuclear Power Station near Shippingport, PA. The analysis showed predominantly west

- southwesterly winds, which are mainly in response to the Ohio River Valley’s terrain orientation . This wind pattern was generally maintained when looking at winds on the days when the Vanport monitor exceeded the lead NAAQS though wind speeds were generally lower during these times. PA DEP attributed the lower wind speeds to more stable atmospheric conditions during periods of high monitored lead concentrations

. Str onger vertical temperature inversions and light wind speeds probably contributed to high ambient lead levels in the Lower Beaver Valley nonattainment area

.

To conduct the modeling attainment demonstration, PA DEP had to compile a lead emission inventory f

or significant sources near the noncompliant air monitoring sites. During promulgation of the 2008 standard, US EPA revised the requirements in 40 CFR 51.117(e) for lead nonattainment area SIP inventories from a 5 t ons per year (tpy) threshold associated with the previous standard to a 0.5 tpy threshold. This was the threshold used to identify major lead sources in the vicinity of the Lower Beaver Valley nonattainment area.

PA DEP identified t w o (2) facilities whose lead emissions exceeded 0.5 tpy. Thes e were the Horsehead Monaca Smelter (Horsehead) and the Bruce Mansfield Power Station (Bruce Mansfield). Air

- dispersion modeling done in 2009 for Bruce Mansfield show ed the facility had no impact on the Lower Beaver Valley n onattainment a rea thus it was exclud ed from further analysis. AES Beaver Valley, a coal

- fired power plant in the lead nonattainment area, was included as an other point source in the lead emission inventory though its lead emissions were less than 0.5 tpy . Lead emissions from nonpoint sources and mobile sources were also examin ed but found to be insignificant and while included in PA DEP’s lead inventory they were not included in the lead modeling demonstration. Section 211(n) of the C lean A ir A ct prohibited the use of any gasoline co ntaining lead or lead additives for use as fuel in motor vehicles after December 31, 1995 (42 U.S.C.A. §7545) making mobile source lead emissions much smaller than the point source contribution

. Leaded fuels are still used for some aviation purposes. No airports were located in or near the Lower Beaver Valley nonattainment area so no lead emissions from the aviation sector were included in the modeling analysis. Horsehead and AES Beaver Valley were therefore the only l ead sources included in the final model emission inventory

.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 4 of 11 Lead model emission inventories for the two point sources in the Lower Beaver Valley were constructed for 2010 and 2015. The 2015 lead emissio ns were used in the model attainment demonstration to determine if projected (future) emission rates would comply with the lead NAAQS. Emissions for 2010 were broken down into actual lead emissions and maximum allowable emission rate s. Maximum allowable emission rates we re used in the model attainment demonstration. Table 1 summarizes le ad emissions comp il ed by PA DEP. Horsehead’s 2010 emissions include point and fugitive sources while only point source emissions were calculated for AES Beaver Valley. Roughly 95% of Horsehead’s 2010 lead emissions came from point sources with the balance made up of fugitives, mainly from material handling activities. AES Beaver Valley used maximum throughput numbers and AP

- 42 emission factors to calculate its maximum allowable lead emission rate. This emission rate was used for AES Beaver Valley for both 2010 and 2015 model inventories.

Table 1. Lower Beaver Valley Lead Point Source Emissions Summary

Lead Source 2010 Lead Emissions 2015 Projected Lead Emissions Actual (tpy) Max Allowable (tpy) Max Allowable (tpy) Horsehead 5.5531 12.128 0.1 AES Beaver Valley 1.367 1.367

Horsehead’s 2015 projected (future) lead emissions were substantially reduced through a consent order and agreement (COA) executed between PA DEP and Horsehead o n November 21, 2012

. This COA stated that Horsehead would pe rmanently discontinue production of zinc metal from its Potter Township F urnace Plant, Sinter Plant, and Secondary Materials Operations on or before October 1, 2014. Horsehead would then be subject to an aggregate potential lead emission rate of 0.1 tpy over each consecutive 12

- month rolling period from all of its remaining stationary sources

.

Dispersion Modeling for the Model Attainment Demonstration

PA DEP performed a n air

- dispersion modeling analysis for the Lower Beaver Valley

n onattainment a rea. The air

- dispersion modeling analysis was completed for base year and future year emission inventories representing two (2) facilities, Horsehead and AES Beaver Valley, with reported lead emissions in 2010 and projected (future) emissions for 2015 . The modeling was conducted in accordance with 40 CFR Part 51, Appendix W

– Guideline on Air Quality Models

.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 5 of 11 The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) was utilized for the model attainment demonstration

. T h ere are t wo (2) input data
preprocessors that need to be run to util ize the AERMOD modeling system; AERMET, which preprocesses representative meteorological data and AERMAP, which preprocesses terrain data from the United States Geological Survey (USGS) Digital Elevation Data. In order to diagnose building downwash effects, the Building Profile Input Program for Plume Rise Model Enhancements (BPIPPRM) was executed. Since the current regulatory version of AERMOD is incapable of calculating the rolling th ree

- month average concentrations necessary for demonstrati ng lead NAAQS compliance, the EPA post

- processor LEADPOST was used. In its three

- month average calculation, LEADPOST utilizes monthly average file s created by AERMOD.

A summary of the model versio ns used in PA DEP’s model attainment demonstration is presented in Table 2. Generally, the most recent versions of the AERMOD and its related preprocessors were used in the air

- dispersion modeling analysis.

Table 2. Summary of AERMOD Used in PA DEP’s Mo deling Analysis

Model Version Description AERMOD 14134 Regulatory Air Dispersion Model BPIPPRM 04274 Building Downwash Calculations for AERMOD AERMET 14134 AERMOD Meteorological Data Preprocessor AERSURFACE 13016 Preprocessor for AERMET using1992 Land Use/Land Cover AERMAP 11103 Terrain Processor, Preprocessor for AERMOD Lead Post 13262 Post Processor for AERMOD, Lead NAAQS Calculator

Air

- Dispersion Model Meteorological Data Development

The Lower Beaver Valley modeling analysis utilize d a 5

- year (2006

- 2010) surface meteorological dataset from the Beaver Valley Nuclear Power Station (BVNPS) along with a concurrent 5

- year (2006

- 2010) surface meteorological dataset from the Automated Surface Observing System (ASOS) at the Pittsburgh Interna tional Airport (KPIT). BVNPS is located approximately 9 kilometers southwest of the Horsehead facility and KPIT is located approximately 23 kilometers south of the Horsehead facility. The analy sis also utilizes morning
upper

- air soundings from KPIT. Bot h meteor o logical data sets were reviewed for completeness and representativeness of the Lower Beaver Valley nonattainment area. The meteorological dataTechnical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 6 of 11 sets were found to meet the completeness requirements outlined in section 5.3.2 of EPA’s Meteorological Monitoring Guidance for Regulatory Modeling Applications ( EPA

- 454/R

- 99

- 005 , February 2000) and are representative of atmospheric conditions in the vicinity of Horsehead and the Lower Beaver Valley nonattainment area.

Surface meteorological data from the BVNPS included wind and temperature measurements from multiple heights (10.7 meters, 45.7 meters and 152.4 meters). Additionally, measurements of standard deviation o f the horizontal wind direction and vertical temperature differences were used. ASOS win ds, temperatures, surface pressure and sky cover were processed using AERMET as well as morning soundings from KPIT

. The meteorological data was process in AERMET such that the ASOS wind data was not substituted for any missing BVNPS wind data.

In additi on to the meteorological data, AERMET needs surface characteristic information including surface roughness, albedo and Bowen Ratio. This information was construct ed using AERSURFACE (version 13016 ) which extracts this information from the USGS N ational Land Cover Database (N LCD

, 1992 )

. AERSURFACE was run at a seasonal resolution using a default 1

- kilometer radius with twelve 30

- degree sectors for surface roughness length. S urface moisture condition s were used in the Bowen R atio calculation and were bas ed on averaged precipitation data for Pennsylvania Climate Division 9. Specific seaso nal surface moisture conditions were derived from precipitation data and comparing it to a 30

- year climatological average to determine if a particular season was consider ed dry, average or wet. Snow cover information was also examined to ensure there was no continuous snow cover occurring on a seasonal basis.

Air

- Dispersion Model Receptor Grid Development:

PA DEP developed g round

- level model receptors for areas defined as “ambient air” in accordance with 40 CFR §50.1(e). These mode l receptor points, once defined, are used by AERMOD to calcul ate air concentrations from lead emission sources

. Facilities that have sufficient limitations on public access to their sites , a fence or other suitable physical barrier, do not have to establish model receptor points within their property boundary . Horsehead has sufficient restrictions to public access and therefore model receptors were not placed within these
restr icted areas except for a portion of I

- 376 that crosses over the eastern section of Horsehead’s property (where public access would occur)

. AES Beaver Valley d id not have sufficient public access limitations so model receptors were placed within this facil ity’s property line in accordance with EPA’s June 22, 2007 memorandum entitled “Interpretation of ‘Ambient Air’ In Situations Involving Leased Land Under the Regulations for Prevention of Significant Deterioration (PSD) ”

.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 7 of 11 PA DEP limited its model receptor grid to the three (3) townships that make up the Lower Beaver Valley nonattainment area. This configuration appears to be sufficient to allow the dispersion model (AERMOD) to calculate the maximum projected (future) modeled concentration , which o ccur within 50 meters of Horsehead’s southern ambient

- air boundary

.

A Cartesian grid

, centered on Horsehead

, was used in the development of the model receptor grid. Model receptor points were placed along Horsehead ’ s ambient

- air boundary (and a section

o f I

- 376 ) at a 25 meter spacing. A fine Cartesian 50

- meter spaced grid extended from Horsehead’s ambient

- air boundary out to 2 kilometers. Grid spacing increased to every 100 meters from 2 to 5 kilometers from Horsehead’s ambient air boundary and then eve ry 500 meters for areas beyond 5 kilometers that were still within the Lower Beaver Valley nonattainment area. The model recept or grid ( see Figure 2 ) contains nearly 7,000 grid points.

Once the model receptor grid was established, it was run through AERM AP to determine each receptor’s elevation and terrain height scale, a parameter needed by AERMOD. These values were calculated from terrain data generally provided and maintained by the U.S. Geological Survey or USGS. PA DEP utilized the USGS National Elevation Dataset (NED) with a resolution of one

- third arc

- second (approximately 10 meters).Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 8 of 11 Figure 2. AERMOD Model Receptor Grid for the Lower Beaver Valley, PA Lead Nonattainment Area

Lead Emission Rates and Building Downwash Development

Projecte d lead emissions from the Horsehead facility were based on the November 21, 2012 COA

, which contains a plant

- wide lead emission limit of 0.1 tpy

. As stated previously, Horsehead agreed to permanently discontinue production of zinc metal from its F urnace Plant, Sinter Plant, and Secondary Materials Operations on or before October 1, 2014. These operations appeared to have shut down in the second quarter of 2014. Lead emissions from AES Beaver Valley were based on AP

- 42 factors and maximum throughput info rmation.

A total of eight (8) point sources were modeled for the projected (future) case; four (4) from Horsehead and four (4) from AES Beaver Valley. Since material handling operations atTechnical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 9 of 11 Horsehead have ceased, no fugitive lead emissions were carried fo rward into the projected (future) modeling case.

Projected building and stack configurations at Horsehead and AES Beaver Valley were run through EPA’s BPIP program to determine building downwash parameters to be used in AERMOD. BPIP requires building loc ations and heights as well as stack height information to determine building downwash parameters. Downwash output from BPIP is then used as input into AERMOD.

AERMOD Results Summary

Two pieces of information are needed to determine if a nonattainment ar ea will meet the lead NAAQS. These include a modeled lead concentration from an air dispersion model like AERMOD and a representative background lead concentration. A dispersion model like AERMOD will estimate the ambient lead concentrations based on hou rly lead emissions that are included as model inputs . The purpose of a representative background lead concentration is to account for minor ancillary sources that may not be explicitly modeled

.

PA DEP reviewed monitoring data from the Shippingport monitor in Potter Township to determine the maximum 3

- month lead concentration to be use d as a background concentration in the model attainment demonstration. It found the maximum 3

- month lead concentr ation at Shippingport between 2010 and 2013 was 0.08 μg/m 3 . After reviewing the data

, PA DEP determined that there were times during this 3

- month period where emissions from Horsehead significantly impacted the monitor ’s lead concentration. The max imum c oncentration was then

re

- averaged to exclude these periods when Horsehead was impacting the monitor to remove the possibility of “double counting” since Horsehead emissions would be included in both the background concentration and the modeled concentratio n. The final adjusted background lead concentration was 0.05 μg/m 3

.

AERMOD does not directly calculate 3

- month lead concentrations in the form of the lead NAAQS

. LEADPOST must be run using specific output files generated by AERMOD t o calculate a modeled 3

- month lead concentration . L EADPOST takes AERMOD output files and calculates a rolling 3

- month average lead concentration . This modeled concentration is then added to th e background concentration and compared with the lead NAAQS to determine compliance

.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 10 of 11 The highest projected 3

- month modeled lead concentration from LEADPOST was 0.0274 μg/m 3

. Projected (future) modeled 3

- month maximum lead concentrations are shown in Figure 3. Again, this was based on the remaining projected lead sources and emission r ates at Horsehead after its COA took effect along with lead emission rate s from AES Beaver Valley. The final modeled lead concentration is the maximum projected 3

- month lead concentration from LEADPOST plus the background monitored concentration from the Shippingport monitor. This yields a projected lead concentration of 0.02 74 μg/m 3 plus 0.0 5 μg/m 3 , or ~0.08 μg/m 3 , which is significantly lower than the lead NAAQS of 0.15 μg/m 3

. This indicates that projected lead concentrations based on current operations at Horsehead and AES Beaver Valley (plus a representative background co ncentration ) will meet the 2008 lead NAAQS.

Figure 3. Projected (future) maximum 3

- month lead concentrations from PA DEP ’s AERMOD analysis. The peak receptor is highlighted and is located within 50 meters of

Hors e head’s southern ambient air boundary.Technical Support Document for the Modeling Portion Of the Commonwealth of Pennsylvania ’s

Lead State Implementation Plan (SIP) entitled Lower Beaver Valley Area Nonattainment Area for

the 2008 Lead National Ambient Air Quality Standard dated January 2015

Page 11 of 11 Summary of EPA’s Technical Findings

EPA has reviewed PA DEP’s modeling analysis for the Lower Beaver Valley lead nonattainment

area. PA DEP conducted air dispersion modeling using EPA’s AERMOD modeling system. I n general, PA DEP followed procedures out lined in 40 CFR Part 51, Appendix W

– Guideline on Air Quality Models. Meteorological data met data completeness requirements, was representative of atmospheric conditions in the Lower Beaver Valley nonattainment area and was properly processed using AERM OD’s preprocessors AERMET and AERSURFACE. The model receptor grid was designed to capture the maximum projected (future) modeled concentrations and properly processed using appropriate terrain information via AERMAP. Projected (future) lead emission inve ntories were developed for use in AEMOD along with source building and stack configurations to calculate building downwash conditions. An appropriate representative background lead concentration was determined using monitoring data from the Shippingport

m onitor.

PA DEP’s projected maximum rolling 3

- month modeled lead concentration was added to the 3

- month background concentration from the Shippingport monitor. The final projected model concentrations was 0.0274 μg/m 3 . This concentration was added to the background lead concentration of 0.0 5 μg/m 3 to yield a total projected (future) 3

- month lead concentration of 0.0 8 μg/m 3 . This projected (future) lead concentration is well below the 2008 lead NAAQS (0.15 μg/m 3 ) and demonstrates that Low er Beaver Valley nonattainment area will reach attainment with the lead standards established by the US EPA.

Recommendation of Approval of PA DEP’s Model Attainment Demonstration

EPA has evaluated the information provided in PA DEP’s lead SIP and concludes that the Commonwealth’s model attainment demonstration shows current lead control and emission limit s will provide for attainment of the 2008 lead NAAQS

.