SCREEN 3 TUTORIAL

ENV 6146:Atmospheric Dispersion Modeling

March, 2010

Presented by:Adeeba Abdul Raheem

Web 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.Html

SCREEN3 Tutorial1

http://www.valleyair.org/busind/pto/tox_resources/Modeling%20Guidance%20W_O%20Pic.pdf/

http://www.epa.gov/ttn/scram/userg/screen/screen3d.pdf

B:Guidance for Air Dispersion Modeling

A: Software

http://www.colorado.gov/airquality/permits/screen.pdf

OUTLINE

Introduction Overview of SCREEN3 Getting started Input data Different interfaces Model description Examples Conclusions

SCREEN3 Tutorial 3

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.

COMPARISON

http://www.trainex.org/web_courses/subpart_x/Encyclopedia%20X%20pdf%20files/Environmental%20Assessment%20pdf%20files/AirDispersionEmissionModelingX.pdf

Spatial and temporal scales of widely used air quality models

http://www.epa.gov/ttn/fera/data/risk/vol_1/chapter_09.pdf

SCREEN3 Tutorial 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 StackHb = Height of BuildingL = 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 31

SCREEN3 USER FRIENDLY INTERFACE

SCREEN3 Tutorial 32

SCREEN3 INTERFACE

SCREEN3 Tutorial 33

SCREEN3 EXAMPLE

SCREEN3 Tutorial 34

THANKS?