Air Modeling for Non-Modelers:What’s Up with the New Ambient Standards?

James A. WestbrookOctober 12, 2010

Agenda: New Ambient Standards• Compliance with ambient standards

Ne ambient standards• New ambient standards• Strategies to pass the standards:

– Challenges you may face– Quick refinement techniques to consider– More advanced techniques

• Example for the 1-hour NO2 standardp• Conclusions

BlueScape, Inc.

• 20 years experience M th 100 d li j t• More than 100 modeling projects

• National Experience with AERMOD, CALPUFF th d lCALPUFF, other models

• Solve tough air quality modeling issues:A id d li i t- Avoid modeling requirements

- Develop meteorological data and monitoring data- Refinement strategies for problem impacts- Refinement strategies for problem impacts- Agency negotiations and protocols

What is Air Quality Modeling Used For?

• Compliance with criteria pollutant ambient standardsstandards– Permits, minor source NSR, PSD major source– Environmental Impact Reports (EIRs)

• Human Health and Ecological Risk Assessments

• Accidental chemical spills• Long-range visibility impacts• Toxic tort litigation• AERMOD is the regulatory workhorseg y

Typical Air Quality Modeling Study

• Need a Project• Triggered by exceeding emissions significance

levels• Modeling against significant impact levels (SILs), or

the full standardthe full standard• Hourly meteorological data and terrain data• Full impact modeling to meet standards PSD:• Full impact modeling to meet standards, PSD:

- Project impacts + - Other facility sources +Other facility sources - Nearby facilities +- Monitored background concentrations

Primary NationalAmbient Air Quality Standards or NAAQS*Ambient Air Quality Standards or NAAQS

PollutantAveraging

PeriodValue

(g/m3)**(g )PM10 24-hour 150PM2.5 24-hour 35NO2 1 hour 188NO2 1-hour 188NO2 Annual 100SO2 1-hour 196SO2 24-hour 367CO 1-hour 10,000CO 8-hour 40,000,

* Partial List** Equiv. units; state agencies may have different standards

See: www.arb.ca.gov/research/aaqs/aaqs2.pdf for standards

New Ambient Standards • EPA has released three policy memos:*

– New NO2, 1-hour average, 100 ppb or 188 g/m3– New SO2, 1-hour average, 75 ppb or 196 g/m3– Justify PM10 as a surrogate for PM2.5 or model

PM2 5 24-hour average of 35 g/m3PM2.5, 24 hour average of 35 g/m3• EPA’s unfinished business

– PSD SILs increments monitoring thresholdsPSD SILs, increments, monitoring thresholds– Background monitoring data availability– Secondary PM2.5 formation, condensibles

www.epa.gov/region7/air/nsr/nsrmemos/appwno2.pdfwww.epa.gov/region7/air/nsr/nsrmemos/appwso2.pdfhttp://bit.ly/9NeHnhp y

New Air Modeling ChallengesC b i• Combustion sources- Relatively high NO2 emissions- PM10=PM2.5

• Short engine or vehicle stacks, mean higher impactsimpacts

• Low significance levels require full modelingP j t i t 1 2 ?• Project in next 1-2 years?- Due diligence modeling

St t i d i- Strategic design process- Stay close on EPA / state agency developments

“Quick Fix” Modeling Strategies to Passg g

• Project design changesj g g• Emission limitations

- Limit fuel or material throughputLimit fuel or material throughput- Limit hours of operation- Limit hourly engine testing engine phasing- Limit hourly engine testing, engine phasing- Voluntary control technology installation

Stack height increases• Stack height increases• Increase gas flow rate and temperature

Advanced Strategies to Pass• PVMRM, OLM and ARM for NO2, as limited

by ozone• Source Test for in-stack NO2/NOx ratios• Modify the PM2.5 fraction in PM10, if relevant• Review / adjust meteorological data• Spatial / temporal modeling

- Show project does not cause or contribute to significant impacts

Consider only periods that contribute to high values- Consider only periods that contribute to high values • Monitoring at Point of Maximum Impact

Agency negotiation• Agency negotiation

Modeling Example

• Large gas-fired boiler and emergency diesel engineg

• Baseline, all NOx = NO2; high max. 1-hour modeling + max backgroundhour modeling + max. background

• Refinements:a) H8H of daily maximum 1 hour valuesa) H8H of daily maximum 1-hour valuesb) PVMRM with hourly ozone data, in-stack

NO2/NOx = 0.2c) Source test for in-stack NO2/NOx ratiod) Stack height increase, reduce emissions

12

Baseline 1-hour NO2 Run

13Impact = 1,132 + 88 = 1,220 g/m3 = FAIL!!

Modeling Refinements

14Impact = 78 + 88 = 166 g/m3 = PASS!!

Model Run Summary

Baseline H8H Pull the Stops

Max. 1-Hour Avg. 1,132 g/m3 636 g/m3 78.3 g/m3gNOx Concentration

, g g g

w/background88 g/m3

1,220 g/m3 724 g/m3 166 g/m3g

Form of Result H1H H8H H8H

PVMRM Used? No No Yes

In-Stack NO2 Ratio -- 0.20 0.10

Engine Stack Height 12 feet 12 feet 25 feetg g

% of Max HourEngine Emission Rate

100% 100% 50%

15Advanced refinements were needed to pass ….

Conclusions• New NO2, SO2 and PM2.5 ambient standards will

cause new challengesE t (b t fi ) th t li t d f ll i t• Expect (but confirm) that complicated full impact modeling may be required

• Conduct modeling due diligence early to troubleshootConduct modeling due diligence early to troubleshoot problems

• Hire an expert modeling consultant- Experience with the latest tools and guidance- Experience passing the standards using advanced

techniquestechniques- Interact with state agencies, come with a strategy- Stay on top of developing EPA and state guidance

Next Webinar

EPA’ GHG R ti P i 2011EPA’s GHG Reporting Program in 2011: Are You Ready?

- What do I need to do to prepare?- Key reporting timelines- What are the roles and responsibilities?

Comparison and overlaps with state requirements- Comparison and overlaps with state requirements- EPA software preview, reporting needs and data gap-filling- Alternative calculation methodologies

https://www2.gotomeeting.com/register/836647746Tuesday, December 7, 9 AM

p g g g

Contact with Questions

James A. Westbrook, PresidentBlueScape, Inc.

858-774-2009 (cell)jwestbrook@bluescapeinc.com

www.bluescapeinc.comp

The Webinar presentation will be posted on p pSlideshare and Scribd (search for BlueScape)