Guidelines-8-1741-0090-R1

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1 09.07.07 Reaffirmed and Reissued DDC DRC HOD

0 29.07.02Issued for Implementation (after revising to meet

ISO-9001,2K version requirements) DDC DRC HOD

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by

Template No. 5-0000-0001-T1 Rev. 1 Copyrights EIL – All rights reserved

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Guidelines For Assessment of

Ground Level Concentrations from

Continuous Point Sources

GUIDELINES FOR ASSESSMENT OF GROUND

LEVEL CONCENTRATIONS FROM

CONTINUOUS POINT SOURCES

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Abbreviations:

ISCST-3.0: Industrial Source Complex Short Term Model – 3.0

EIA: Environmental Impact Assessment

Document Drafting Committee Members:

Mr. R.S.Prasad, Dy. Manager

Mr. B.Ravi Kumar, Dy.Manager

Dr. D.Bandopadhyay, Dy. Manager

Document Review Committee Members

Mr. B.B.Lal, AGM

Mr. V. S. Chhaya, AGM

Mr. Susheel Sadh, Sr. Manager

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CONTENTS

CLAUSE NO. TITLE PAGE NO.

1. PURPOSE 4

2. SCOPE 4

3. REFERENCES 4

4. DEFINITIONS 4

5. METHODOLOGY 4

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1.0 PURPOSE

This document gives guidelines for assessment of ground level concentrations ofpollutants resulting from emission of various continuous point sources.

2.0 SCOPE

This document is useful while preparing Environmental Impact Assessmentreport.

3.0 REFERENCES

3.1 “Assessment of Impact to Air Environment” published by CentralPollution Control Board.

3.2 “Guidelines for conducting air quality modelling” published by IndiaMeteorological Department.3.3 User Manual of Trinity’s Breeze Air Dispersion Model.3.4 Manual of “Industrial Source Complex Short Term Model – 3.0”

published by U.S. Environmental Protection Agency.

4.0 DEFINITIONS

Nil

5.0 METHODOLOGY

EIA involves identification, prediction, assessment and evaluation of impacts onenvironment due to proposed activities. Assessment of ground levelconcentrations of various pollutants due to proposed activities is one of theimportant exercises involved in preparation of EIA report. This guideline gives adetailed information about the model used for assessing air quality due torelease of continuous point sources.

The model used for assessing air quality study is ISCST–3.0, which is one ofthe United States Environmental Protection Agency's (USEPA) UNAMAP seriesof air quality models. It is to be noted that the basic equations used in thismodel and the equations specified in the Central Pollution Control Board’smanual are same.

The Industrial Source Complex models are used to predict pollutantconcentration from continuous: point, area and volume sources. These versatilemodels are preferred by the USEPA because of many features that enable theuser to estimate the concentrations from practically any type of source emittingnon-reactive pollutant.

The ISCST-3.0 model for stacks uses steady state Gaussian Plume equation forthe continuous elevated source. For cross wind and down wind distances, themodel uses either polar or rectangular Cartesian coordinates as specified by theuser. For wind speed profile, wind power law is used to adjust the observed

wind speed to the stack or release height. For computation of plume rise, Briggsplume rise formula is used. The distance dependent momentum plume riseequations are used to determine if the plume is affected by the wake region for

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the building downwash calculations. In order to consider the stack tipdownwash, modification in stack height is performed using Briggs (1974).

The point source dispersion parameters are computed using the Turners (1970)equation that approximately fits the Pasquill-Gifford curves. In order to take inaccount for the wake effect, plume dispersion theory of Huber (1976) andSynder (1977) has been used. The buoyancy-induced dispersion has beenconsidered using the Pasquill method. The vertical term and dry depositions arealso taken into account by this model.

Besides the above, depending on the land use category, the model can be usedfor employing Urban or Rural dispersion coefficients. The model also calculatesthe ground level concentrations due to stack tip downwash as well as in thebuilding wake and the fumigation conditions. Option for simulation of differenttype terrains, viz. flat, simple, intermediate and complex terrains is also built in.

The input requirements for running the above model using computer programconsist of four categories of information:

- Hourly meteorological data- Source data- Receptor data- Program control parameters

Meteorological inputs required by the program include hourly estimates of thewind direction, wind speed, ambient air temperature, atmospheric stability,mixing height, wind profile exponent and vertical temperature gradient. Some ofthe data required as mentioned above e.g. vertical temperature gradient, windprofile exponent and mixing depths call for a detailed study in itself, which inthis case was not possible. Therefore, USEPA approved default values of windexponents and temperature gradient as available in ISCST-3.0 can be used.

The input data requirements for each source include data specific to the sourceand its type (whether point, area or volume source). The source inputrequirement for running the program are the emission height, location, exitvelocity, exit temperature and strength.

The receptor data can be given either as polar, rectangular Cartesian ordiscrete ones. In the cartesian system the x-axis is positive to the east of a

user-specified origin and y-axis positive to the north. In the polar system, r isthe radial distance measured from the origin and angle is measured clock wisefrom the north.

Program control parameters include number of model and logic operations likerural or one of three urban options, selection of plume rise due to momentumand buoyancy as a function of downwind distance, multiple point sources,concentration estimates for 1 hr to annual average, grid / discrete receptors etc.

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