National Ambient Air Quality Standards for NO2 and SO2 –

New Modeling ChallengesAugust 4, 2011

Air & Waste Management Association – Southern Section Meeting &

Technical Conference

Justin Fickas, P.E.Managing Consultant

IntroductionsJustin Fickas, P.E.– Managing Consultant

Managing Consultant based in Atlanta Extensive experience serving wood products, pulp

& paper, power, and general manufacturing industries

B.S. Civil Engineering with an emphasis in Environmental Engineering from Purdue University

Professional Engineer registered in Georgia Joined Trinity in July 2010 – 13 yrs of consulting

experience

Presentation Outline Modeling 101 Overview of the New 1-hr NAAQS Case Studies - “Real World” project examples Going forward – Options to consider in assessment

of the new NAAQS Conclusions

Modeling 101

When are Models Needed?

Regulatory - to determine air quality impacts due to sources of air emissions to determine compliance with existing NAAQS

Engineering – to discern viable control and mitigation options in terms of the net change in air quality

Health – to estimate risk and acute effects

Ecological – to calculate effects on soils & vegetation

The General New Source Review (NSR) Permit Modeling Process - NAAQS

Model facility impacts for comparison to Significant Impact Levels (SILs) established for pollutants of interest

If facility impacts do not exceed the SIL, no further action is needed

If facility impacts exceed the SIL Off-site source impacts (inventory) needs to be

evaluated and developed Both your facility and off-site sources are modeled If exceedances of NAAQS are shown, can be

acceptable so long as it is demonstrated that your facility is not significantly contributing to the exceedance

Guideline on Air Quality Models 40 CFR Part 51, Appendix W

Preferred models are AERMOD and CALPUFF

Provides methodologies for regulatory dispersion modeling

Does not directly include procedures to address the new 1-hour NAAQS (NO2 and SO2)

How Do We Choose a Modeling Methodology?

EPA Clearinghouse Memos “Applicability of Appendix W Modeling

Guidance for the 1-hour NO2 National Ambient Air Quality Standard”, June 28, 2010

“Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard”, August 23, 2010

“Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2 National Ambient Air Quality Standard”, March 1, 2011

State Issued Guidance

Overview of the New 1-hr NAAQS

New NO2 NAAQS for 1-hour NO2 Standard

Published in FR on February 9, 2010 Added a 1-hour form of the standard to the

existing annual standard effective on April 12, 2010

NO2 standard is 3-year average of 98th percentile of annual distribution of daily maximum 1-hour concentrations

Interim 1-hr NO2 Significant Impact Level (SIL) issued in EPA Guidance June 2010 – 4 ppb (7.5 µg/m3)

Revised NO2 NAAQS - Implications

New NO2 monitors, likely near major roadways in urban areas To be operational by January 2013

New 1-hour standard problematic for sources required to model compliance with NAAQS Petition filed on April 12, 2010 by UARG and

API for reconsideration and stay of the NAAQS

“Industrial Sprawl”

New SO2 NAAQS for 1-hour SO2 Standard

Published in FR on June 22, 2010 Added a 1-hour form of the standard effective

on August 23, 2010 Revoked both annual and 24-hour standards SO2 standard is 3-year average of 99th

percentile of annual distribution of daily maximum 1-hour concentrations

Interim 1-hr SO2 Significant Impact Level (SIL) issued in EPA Guidance August 2010 – 3 ppb (7.8 µg/m3)

Revised SO2 NAAQS - Implications Nonattainment areas will be defined

based on BOTH monitoring and modeling New near source monitoring required by

January 2013 New 1-hour standard problematic for

sources required to model compliance with NAAQS

Modeling assessments for facilities found to be potentially contributing to monitoring exceedances

“Industrial Sprawl”

Case Study #1 – Site Location Assistance for a

New Greenfield Site

Case Study #1 – Background (1 of 2)

Client interested in siting a new greenfield manufacturing site

Facility will be a large source of NO2 and SO2 emissions Client education needed regarding new 1-hr

NAAQS Assessments recommended to evaluate

source impacts related to new 1-hr NAAQS

Original assessment indicated site impacts well below the new 1-hr NAAQS

Case Study #1 – Background (2 of 2)

Client provided new facility site layout Updated models incorporating new facility

layout indicated 1-hr NO2 and SO2 values had nearly doubled from initial estimates

Close review of model input files could find no errors – same meteorological data, receptor grid, emission units, buildings, etc.

What happened?

Building/Downwash Influences?

Two Different Site Orientations With Different Results (1 of 2)

Two Different Site Orientations With Different Results – No Buildings (2 of 2)

Plume Visualization (1 of 3)

Plume Visualization (2 of 3)

Plume Visualization (3 of 3)

What Does All This Mean? (1 of 2)

Greenfield Sites Site orientation could have a significant

impact on 1-hr modeling results Could site layout/orientation be revised to

improve modeling results Existing Sites

Review existing site layout – can have a significant impact on 1-hr modeling results

What Does All This Mean? (2 of 2) Items “commonly” considered when

looking for modeling result improvements Stack height Stack diameter Stack flow/velocity Stack temperature Distance of source to the facility fence

line New additional issues to focus on

Building setup/orientation Meteorological data

Case Study #2 – Existing Facility Considering a PSD

Project

Case Study #2 – Background Client interested in modifying several

facility combustion units Due to new regulatory applicability, etc.

looking at possibility of PSD avoidance through installation of emission controls

Assessments recommended to evaluate off-site source impacts related to new 1-hr NAAQS

The problem came with off-site sources of NO2

Off-Site Only Impacts Due to 1-hr NO2

Cause or Contribute AnalysesWind from Southwest Wind from Southeast

What Does All This Mean? Greenfield Sites

Review of the proximity of large off-site sources of 1-hr NO2 and SO2 a must as part of site selection process

Existing Sites Prior to consideration of a large project,

review existing site impacts and off-site impacts (if known) in comparison to the 1-hr NAAQS

Even with the inherent “difficulty” in pairing violations in time and space, can still cause issues given the proper source/wind alignment

Accuracy of modeling inventories more critical

Going Forward

Reduction in Receptor Grid

Discussed in EPA 3/1/11 memo Reduction in receptors to only those receptors

which exceed the 1-hr NAAQS interim SIL Solves one portion of the “temporal and

spatial” test for cause and contribute analyses

Can be helpful in assessment of source contributions to the new 1-hr NAAQS Reduction in number of receptors necessary

to evaluate culpability for modeled violations MAXDCONT processing requirements

Limitations in Hourly Emissions

“Emergency” Units discussed in EPA 3/1/11 memo

Hour of day function in AERMOD model Worst case modeling impacts, due to

meteorological conditions, can occur during non-daylight hours for fugitive or low dispersion point sources

Restricting emissions to daylight hours, or equipment “testing” to certain hours, can show modeled improvements

Including “Inventory Problem Source” Site Specific Information

Inclusion of facility fenceline? Inclusion of facility buildings and

downwash influences? Actual emission point locations? Review of problem source permit

documentation essential

Additional Possible Strategies Consideration of background?

Use of higher background in place of modeled sources?

Selection of background value sources? Additional guidance regarding the “need”

for modeling for the 1-hr NAAQS? Has there been an actual/potential hourly

emissions increase? Offsets – “net air quality benefit” Modeling actual vs. potential emissions

Conclusions When assessing the new 1-hr NAAQS for

NO2 and SO2, there are additional items to consider that may not have been considered before

The new 1-hr NAAQS can play an integral role in project planning

Cooperation and sharing of ideas/solutions will be beneficial to all

We need to consider thinking “outside the box” for solutions to our current modeling difficulties

Contact Information

Justin Fickas53 Perimeter Center EastSuite 230Atlanta, GA 30346Office: (678) 441-9977Cell: (678) 549-9755Fax: (678) 441-9978http://www.trinityconsultants.com/atlanta/jfickas@trinityconsultants.com