Published on October 12, 2010
Air Modeling for Non-Modelers: What’s Up with the New Ambient Standards? James A. Westbrook October 12, 2010
Agenda: New Ambient Standards • Compliance with ambient standards • Ne ambient standards New • Strategies to pass the standards: – Challenges you may face – Quick refinement techniques to consider – More advanced techniques • Example for the 1-hour NO2 standard p • Conclusions
BlueScape, Inc. • 20 years experience • M More than 100 modeling projects th d li j t • National Experience with AERMOD, CALPUFF, th CALPUFF other models d l • Solve tough air quality modeling issues: - A id modeling requirements Avoid d li i t - Develop meteorological data and monitoring data - Refinement strategies for problem impacts - Agency negotiations and protocols
What is Air Quality Modeling Used For? • Compliance with criteria pollutant ambient standards – 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 workhorse g y
Typical Air Quality Modeling Study • Need a Project • Triggered by exceeding emissions significance levels • Modeling against significant impact levels (SILs), or the full standard • Hourly meteorological data and terrain data • Full impact modeling to meet standards PSD: standards, - Project impacts + - Other facility sources + - Nearby facilities + - Monitored background concentrations
Primary National Ambient Air Quality Standards or NAAQS NAAQS* Averaging Value Pollutant Period (g (g/m3)** ) PM10 24-hour 150 PM2.5 24-hour 35 NO2 1-hour 1 hour 188 NO2 Annual 100 SO2 1-hour 196 SO2 24-hour 367 CO 1-hour 10,000 CO 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/m3 PM2.5, 24 hour • EPA’s unfinished business – PSD SILs increments monitoring thresholds SILs, increments, – Background monitoring data availability – Secondary PM2.5 formation, condensibles www.epa.gov/region7/air/nsr/nsrmemos/appwno2.pdf www.epa.gov/region7/air/nsr/nsrmemos/appwso2.pdf http://bit.ly/9NeHnh p y
New Air Modeling Challenges • C b i sources Combustion - Relatively high NO2 emissions - PM10=PM2.5 • Short engine or vehicle stacks, mean higher impacts • Low significance levels require full modeling • P j t in next 1-2 years? Project i t12 ? - Due diligence modeling - St t i design process Strategic d i - Stay close on EPA / state agency developments
“Quick Fix” Modeling Strategies to Pass g g • Project design changes j g g • Emission limitations - Limit fuel or material throughput - Limit hours of operation - Limit hourly engine testing engine phasing testing, - Voluntary control technology installation • 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 • Monitoring at Point of Maximum Impact • Agency negotiation
Modeling Example • Large gas-fired boiler and emergency g diesel engine • Baseline, all NOx = NO2; high max. 1- hour modeling + max background max. • Refinements: a) H8H of daily maximum 1 hour values 1-hour b) PVMRM with hourly ozone data, in-stack NO2/NOx = 0.2 c) Source test for in-stack NO2/NOx ratio d) Stack height increase, reduce emissions
Baseline 1-hour NO2 Run Impact = 1,132 + 88 = 1,220 g/m3 = FAIL!! 13
Modeling Refinements Impact = 78 + 88 = 166 g/m3 = PASS!! 14
Model Run Summary Baseline H8H Pull the Stops Max. 1-Hour Avg. g 1,132 g/m3 , g 636 g/m3 g 78.3 g/m3 g NOx Concentration w/background 1,220 g/m3 724 g/m3 166 g/m3 88 g/m3 g Form of Result H1H H8H H8H PVMRM Used? No No Yes In-Stack NO2 Ratio -- 0.20 0.10 Engine Stack Height g g 12 feet 12 feet 25 feet % of Max Hour 100% 100% 50% Engine Emission Rate Advanced refinements were needed to pass …. 15
Conclusions • New NO2, SO2 and PM2.5 ambient standards will cause new challenges • E Expect (but confirm) that complicated f ll i t (b t fi ) th t li t d full impact t modeling may be required • Conduct 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 techniques - Interact with state agencies, come with a strategy - Stay on top of developing EPA and state guidance
Next Webinar EPA’s EPA’ GHG R Reporting P ti Program i 2011 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 - EPA software preview, reporting needs and data gap-filling - Alternative calculation methodologies Tuesday, December 7, 9 AM https://www2.gotomeeting.com/register/836647746 p g g g
Contact with Questions James A. Westbrook, President BlueScape, Inc. 858-774-2009 (cell) email@example.com www.bluescapeinc.com p The Webinar presentation will be p p posted on Slideshare and Scribd (search for BlueScape)
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