- The document discusses the application of two state-of-the-art air dispersion models, AERMOD and ADMS, to assess compliance with new air quality requirements at Nanticoke Generating Station near Lake Erie and Lake Ontario. - The models were used to model SO2 emissions from eight coal-fired power generation units and produced significantly different outputs due to their different treatment of key parameters like Monin-Obukhov length and boundary layer depth. - Model selection was found to strongly influence the identification of compliance parameters and therefore the cost of achieving compliance. ADMS also offers a shoreline module that AERMOD currently lacks.

1. Paul Complin 1 , Robert Lyng 2 , Hong Liu 3 , Alan Cocks 4 1ORTECH Environmental, [email_address] 2 Ontario Power Generation Inc., rob.lyng@opg.com 3 PhD Candidate, York University, [email_address] 4 EnviroAnalytics, alan.cocks@enviroanalytics.com Application of Two State-of-the-art Dispersion Models

2. Ontario Regulation 419/05 under the Ontario Environmental Protection Act introduced new air requirements including updated air dispersion models. New Ontario Air Regulatory Regime

3. All Ambient Air Criteria Met for current Regime But Preliminary Screening Indicated Potential for Hundreds of Hours of Exceedances SO 2 selected as the basis for assessing compliance risk. Compliance Issue

4. Develop a Risk Based Operational Regime that meets the new Requirements Operational Restrictions Fuel Switching Capital Upgrades (e.g. FGD) Overall Project

5. SO 2 selected as the basis for assessing compliance risk. AERMOD and ADMS selected as the Assessment Models Modelling Project

6. Eight Coal Fired Power Generation Units Range of coal types and blends Two 200 metre stacks with four flues each CEMs measure SO2 emission rates, exhaust velocities, exhaust temperatures Lakeshore site, flat terrain Nanticoke Generating Station

7. Lake Erie Lake Ontario Nanticoke GS Buffalo Toronto Detroit

9. Regulation 419/05 and the Air Dispersion Modelling Guideline for Ontario Issued in 2005, updated March 2009 Screen3/AERMOD as the primary model Regional 5 year Meteorological Data Sets Highest 8 hours Excluded as Outliers Alternate Models ‘If Conditions Warrant’ Modelling Protocol

10. AERMOD Performance

11. Modelling Methodology

12. Two Models: AERMOD & ADMS AERMOD ADMS Both “New Generation” models Components are based on similar sets of state-of-the-art algorithms to describe the state of atmospheric boundary layer Bimodal distribution of turbulent vertical velocities for convective conditions. Regulatory model in US & Ontario and Alternative model elsewhere. Regulatory model in UK and Alternative model in US. Allows vertical profiles of wind and temperature to be input. Requires only one level of near-ground observations to be input, but could take the state of the art ABL as input. Contains shoreline module.

13. Dispersion Factors for Five Scenarios (all units at MCR)

14. Key Model Parameters Monin-Obukhov Length Boundary Layer Depth y

15. Wind Speed versus Dispersion Factor

16. 1/L mo versus Dispersion Factor

17. Model Parameters for 1000 highest Maximum Dispersion Factors Monin-Obukhov Length Boundary Layer Depth

18. Dispersion Factors for Five Scenarios (all units at MCR)

19. Conclusions Two state-of-the-art models were applied in compliance mode to assess their differences. The models' different treatment of key model parameters results in significantly different outputs. The identification of the compliance parameters, and therefore the cost of compliance, can be strongly influenced by model selection. ADMS offers a shoreline module whereas AERMOD currently does not. This difference may be important for facilities near large bodies of water.

20. Paul G. Complin Principal- Compliance and Permitting ORTECH Environmental 804 Southdown Road Mississauga, ON, Canada L5J 2Y4 Phone 905 822-4120 e266 or 877-774-6560 e266 Fax 905 855-0406 [email_address] www.ortech.ca Questions?