Slide 1Slide 2outlineINTRODUCTIONINTRODUCTIONOverview Screen 3ComparisonSpatial and temporal scales of widely used air quality modelsGetting Started –Screen 3Input dataInput data(Meteorology options)Input data(Fumigation Option)Point SourceInput Requirements To Run Screen Models For Point SourceArea SourceInput Requirements To Run Screen Models For Area SourceVolume SourceInput Requirements To Run Screen Models For volume SourceInput Requirements To Run Screen Models For volume SourceFlare SourceInput Requirements To Run Screen Models For Flare SourceBuilding DownwashBuilding DownwashInput Requirements To Run Screen Models For Building DownwashSCREEN3 Non-regulatory optionsBrode algorithm for mixing heightAnemometer height ≠ 10 mSchulman and Scire Building Cavity AlgorithmImportant information:Important information:SCREEN3 USER FRIENDLY INTERFACESCREEN3 INTERFACESCREEN3 EXAMPLETHANKS?SCREEN 3 TUTORIALENV 6146:Atmospheric Dispersion ModelingMarch, 2010Presented by:Adeeba Abdul RaheemWeb resources to download SCREEN3 and Modeling Guides:EPA (Dos based program):Http://www.Epa.Gov/ttn/scram/dispersion_screening.HtmUser friendly interface:Http://www.Weblakes.Com/products/screen/index.HtmlSCREEN3 Tutorial1http://www.valleyair.org/busind/pto/tox_resources/Modeling%20Guidance%20W_O%20Pic.pdf/http://www.epa.gov/ttn/scram/userg/screen/screen3d.pdfB:Guidance for Air Dispersion ModelingA: Softwarehttp://www.colorado.gov/airquality/permits/screen.pdfOUTLINEIntroductionOverview of SCREEN3Getting startedInput dataDifferent interfacesModel descriptionExamplesConclusionsSCREEN3 Tutorial3INTRODUCTIONSCREEN3 is a steady-state Gaussian plume model which uses worst-case meteorological data to predict ambient pollutant concentrations resulting from single continuous emission sourcesSCREEN3 Tutorial4INTRODUCTION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 ISC3SCREEN3 Tutorial5OVERVIEW SCREEN 3SCREEN3 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 Tutorial6COMPARISON http://www.trainex.org/web_courses/subpart_x/Encyclopedia%20X%20pdf%20files/Environmental%20Assessment%20pdf%20files/AirDispersionEmissionModelingX.pdfSpatial and temporal scales of widely used air quality modelshttp://www.epa.gov/ttn/fera/data/risk/vol_1/chapter_09.pdfGETTING STARTED –SCREEN 3Convert all lengths and distances to meters Convert temperatures to degrees KelvinIdentify building contributions to air dispersion (stack emissions)SCREEN3 Tutorial9INPUT DATATo 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 Tutorial10INPUT 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 Tutorial11INPUT 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 Tutorial12Point SourcePoint sources are typically used when modeling releases from sources like stacks and isolated vents. Input requirements for point sources include:SCREEN3 Tutorial13Input 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, WidthSCREEN3 Tutorial14Area SourceArea 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 Tutorial15Input 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 DirectionSCREEN3 Tutorial16Volume SourceVolume 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 Tutorial17Input 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 Tutorial18Input Requirements To Run Screen Models For volume SourceSCREEN3 Tutorial19Flare SourceFlare sources are used as control devices for a variety of sources. SCREEN3 supports flares directly through its flare source type.SCREEN3 Tutorial20Input 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 Tutorial21Building DownwashBuildings and other structures near a relatively short