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Screen 3 Tutorial. ENV 6146:Atmospheric Dispersion Modeling March, 2010. Presented by: Adeeba Abdul Raheem. Web resources to download SCREEN3 and Modeling Guides:. A: Software. EPA (Dos based program): Http://www.Epa.Gov/ttn/scram/dispersion_screening.Htm. User friendly interface:.

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    1. Screen 3 Tutorial ENV 6146:Atmospheric Dispersion Modeling March, 2010 Presented by: Adeeba Abdul Raheem

    2. Web resources to download SCREEN3 and Modeling Guides: A: Software EPA (Dos based program): Http://www.Epa.Gov/ttn/scram/dispersion_screening.Htm User friendly interface: Http://www.Weblakes.Com/products/screen/index.Html B:Guidance for Air Dispersion Modeling SCREEN3 Tutorial

    3. outline • Introduction • Overview of SCREEN3 • Getting started • Input data • Different interfaces • Model description • Examples • Conclusions SCREEN3 Tutorial

    4. INTRODUCTION • SCREEN3 is a steady-state Gaussian plume model which uses worst-case meteorological data to predict ambient pollutant concentrations resulting from single continuous emission sources SCREEN3 Tutorial

    5. INTRODUCTION • SCREEN3 is the current regulatory screening model for air permitting applications. • The original SCREEN model was released by EPA in 1988 • Based on the same steady-state Gaussian plume algorithms as ISC3 SCREEN3 Tutorial

    6. Overview Screen 3 SCREEN3 can perform all the single source short-term calculations including: • Estimating max. ground-level concentrations • Incorporating the effects of building downwash • Estimating concentrations in the cavity recirculation zone. • Estimating concentrations due to inversion break-up and shoreline fumigation. • Determining plume rise for flare releases. SCREEN3 Tutorial

    7. Comparison

    8. Spatial and temporal scales of widely used air quality models

    9. Getting Started –Screen 3 • Convert all lengths and distances to meters • Convert temperatures to degrees Kelvin • Identify building contributions to air dispersion (stack emissions) SCREEN3 Tutorial

    10. Input data To perform a modeling study using SCREEN3, data for the following input requirements must be supplied: • Source Type (Point, Flare, Area or Volume) • Physical Source and Emissions Characteristics • Meteorology:SCREEN3 can consider all conditions, or a specific stability class and wind speed can be provided. • Building Downwash:If this option is used then building dimensions (height, length and width)must be specified. SCREEN3 Tutorial

    11. Input data(Meteorology options) • Full: complete set of stability - wind speed combinations examined for worst case scenario at each downwind location • Stability class: worst case scenarios for predetermined wind speeds • Stability class - wind speed combination: calculations reported for only the combination specified by user SCREEN3 Tutorial

    12. Input data(Fumigation Option) • Inversion break-up - pollutant release into the radiation inversion layer moves horizontally with little dispersion due to the strong stability of the inversion layer • Shoreline fumigation (sources within 3000 m of a large body of water) • If a source with a tall stack (greater than 65m) is located in a coastal region, then the effects of coastal (or shoreline) fumigation may be significant SCREEN3 Tutorial

    13. Point Source Point sources are typically used when modeling releases from sources like stacks and isolated vents. Input requirements for point sources include: SCREEN3 Tutorial

    14. Input Requirements To Run Screen Models For Point Source • Emission rate (g/s) • Stack Height (m) • Shortest distance to property line • Stack velocity (or volumetric airflow) • Stack gas temperature (K) • Stack Inside Diameter • Building Height, Length, Width SCREEN3 Tutorial

    15. Area Source Area sources are used to model low level or ground level releases where releases occur over an area (e.g., landfills, storage piles, slag dumps, and lagoons). SCREEN3 Tutorial

    16. Input Requirements To Run Screen Models For Area Source • Emission Rate per unit area (g/(s-m2)) • Source Release Height • Larger Side Length of Rectangular Area (m) • Smaller Side Length of Rectangular Area (m) • Receptor Height Above Ground (m or ft.): This may be used to model impacts at “flagpole” receptors. The default value is assumed to be 0.0 m (i.e., ground-level receptors) • Wind Direction SCREEN3 Tutorial

    17. Volume Source Volume source is used to model releases from a variety of industrial sources, such as building roof monitors, fugitive leaks from an industrial facility, multiple vents, and conveyor belts. SCREEN3 Tutorial

    18. Input Requirements To Run Screen Models For volume Source • Emission Rate in grams per second (g/s). • Source Release Height above ground surface • Initial Lateral Dimension(m) • Initial Vertical Dimension(m) • Receptor Height Above Ground [m or ft] SCREEN3 Tutorial

    19. Input Requirements To Run Screen Models For volume Source SCREEN3 Tutorial

    20. Flare Source Flare sources are used as control devices for a variety of sources. SCREEN3 supports flares directly through its flare source type. SCREEN3 Tutorial

    21. Input Requirements To Run Screen Models For Flare Source • Emission Rate in grams per second (g/s). • Flare Stack Height • Total Heat Release Rate in calories per second (cal/s) for the flare. • Receptor Height Above Ground • EPA’s SCREEN model assumes stack gas exit velocity (Vs) = 20m/s, stack gas exit temperature (Ts) of 1,273K calculates an effective stack diameter based on the heat release rate. SCREEN3 Tutorial

    22. Building Downwash • Buildings and other structures near a relatively short stack can have a substantial effect on plume transport and dispersion, and on the resulting ground-level concentrations that are observed. SCREEN3 Tutorial

    23. Building Downwash • Building downwash can occur when HStack= HS< Hb + 1.5L HStack= Height of Stack Hb= Height of Building L = lesser of Hb or PBW PBW = Maximum Projected Building Width • Screen model will do this calculation when the building downwash option is used. If HS> Hb + 1.5L, then building downwash will not be shown in SCREEN results SCREEN3 Tutorial

    24. Input Requirements To Run Screen Models For Building Downwash • Building Height(m) • Minimum Horizontal Building Dimension(m) • Maximum Horizontal Building Dimension (m) SCREEN3 Tutorial

    25. SCREEN3 Non-regulatory options • An alternative mixing height algorithm (Brode, 1991) • Optional input of an anemometer height in place of the default height of 10 meters. • An alternative building cavity algorithm (Schulman and Scire, 1993) SCREEN3 Tutorial

    26. Brode algorithm for mixing height • The alternative mixing height is determined by using the maximum of a predetermined mixing height or a value adjusted slightly higher than the plume height, whichever is greater. • Selection of this algorithm results in concentrations that are generally more conservative than output from the ISCST3 model. SCREEN3 Tutorial

    27. Anemometer height ≠ 10 m • The optional input of an anemometer height in place of the default height(10 m) affects the stack top wind speeds for Choice of Meteorology selections 1 and 2 • For Choice of Meteorology selection 3, the user is prompted to enter a 10 meter wind speed which is unaffected by any optionally entered anemometer height SCREEN3 Tutorial

    28. Schulman and Scire Building Cavity Algorithm • The published concentration results using this algorithm model the sampled wind tunnel test concentrations better than the regulatory algorithm for the range selected. SCREEN3 Tutorial

    29. Important information: • The complex terrain algorithms in SCREEN3 are for point and flare sources, not area/volume sources. • It is usually recommended that the receptor height be set to 0 meters (e.g., ground-level) • In simple terrain areas, SCREEN3 calculates 1-hour concentration estimates. In complex terrain, the model provides 24-hour concentration values. (Conversion tables will be provided in the class) SCREEN3 Tutorial

    30. Important information: • Automated Distances Option:It gives the user the option of using a preselected array of 50 distances ranging from 100 m out to 50,000 m (50 km) using the following increments • Discrete Distances Option:The Discrete Distances option allows the user to find the maximum impact at specific locations of interest, such as nearby residences, hospitals, or schools. SCREEN3 Tutorial



    33. SCREEN3 EXAMPLE SCREEN3 Tutorial

    34. THANKS? SCREEN3 Tutorial