Dispersion Modeling of Incinerator Stack Emissions at

Onyx Environmental Services, Inc. 

(formerly Trade Waste Incineration)

Sauget, Illinois

Prepared By: Todd D. Ramaly

_________________________________________

U.S. Environmental Protection Agency

RCRA Programs Section

June 15, 2006
I-1

I. Executive Summary

In November 2000, the United States Environmental Protection Agency (U.S. EPA) began an 

effort to model the dispersion of emissions from the incinerator stacks at the Onyx 

Environmental Services, Inc. (Onyx) facility located in Sauget, Illinois. This effort was 

undertaken in order to gauge whether or not the hazardous waste incinerator requirements under 

the September 30, 1999 Maximum Achievable Control Technology (MACT) Rule (Federal 

Register Volume 64, page 52827 - 64 FR 52827) would be protective of public health and the 

environment in the surrounding community. U.S. EPA used dispersion models recommended in 

the Appendix W of Title 40 of the Code of Federal Regulations Part 51 (40 CFR Part 51) for the 

modeling effort and based the approach on that of the 1998 Draft Human Health Risk 

Assessment Protocol (Draft HHRAP) (U.S. EPA 1998). 

The results of this first round of modeling were used in preparing preliminary operating 

conditions for the incinerators under the facility’s draft RCRA permit which was provided to 

Onyx on June 5, 2003 (U.S. EPA 2003). In response to the draft conditions, Onyx 

commissioned its own dispersion modeling and submitted a report of such on September 8, 2004 

(Onyx 2004). U.S. EPA reviewed Onyx’s dispersion modeling and found some aspects that 

were more appropriate for the site and some that were not supportable. Onyx responded by 

conducting additional stack testing in March of 2005, adding site-specific particle size 

distributions and mercury speciation for the rotary kiln unit. Onyx submitted updated modeling 

incorporating the new stack test results in May 2005 (Onyx 2005a). 

Incorporating appropriate modeling improvements from Onyx’s modeling efforts and the results 

of the stack testing, U.S. EPA prepared a second round of dispersion modeling in May of 2005. 

The results were comparable to those generated by Onyx. In October 2005, Onyx submitted yet 

another version of the modeling differing significantly from earlier versions (Onyx 2005c). The 

differences were the result of updating the modeling to reflect the new HHRAP which had been 

finalized with several significant revisions in September of 2005 (U.S. EPA 2005). Onyx 

incorporated some of the revisions made to the HHRAP.

In April 2006, U.S EPA incorporated recommendations of the finalized HHRAP guidance and 

appropriate inputs from Onyx’s and U.S. EPA’s earlier modeling efforts and performed the 

dispersion modeling documented in this report for use in assessing impacts to public health and 

the environment in the vicinity of the facility and for the development of operating conditions for 

the RCRA permit, if any.
II-1

II. Facility Information

The Onyx facility, located at #7 Mobile Avenue in Sauget, Illinois, is long and narrow and laid 

out from the southwest to the northeast on its longest transect (See Figure II-1). Stacks 2 and 3 

each serve fixed-hearth dual-chamber incinerators located on the northeastern end of the facility

and Stack 4 serves a rotary kiln incinerator located on the southwestern end. The incinerators 

burn a variety of hazardous wastes. The facility is located in the Mississippi River floodplain 

and is surrounded by multiple types of land use. Industrial and commercial businesses comprise 

the immediate vicinity of the facility with residential areas just over a mile away. Nearby 

waterbodies include the Mississippi River to the west and Frank Holten State Park, which 

comprises two lakes to the east. The following stack information was submitted by Onyx in its 

latest modeling report (Onyx 2005c).

Parameter Stack 2 Stack 3 Stack 4

Source fixed-hearth dual-chamber incinerators rotary kiln

Coordinates* 745314.456m E

4275912.275m N

745342.392m E

4275958.041m N

744979.822m E

4275204.979m N

Base Elevation 126.19 meters 126.19 meters 126.49 meters

Stack Height 27.432 meters 27.432 meters 30.48 meters

Stack Diameter 0.6858 meters 0.6858 meters 1.2192 meters

Stack Gas Temperature 463 Kelvin 463 Kelvin 481 Kelvin

Stack Gas Exit Velocity 20.2 meters/second 20.2 meters/second 20.4 meters/second

Emission Rate** 1 gram/second 1 gram/second 1 gram/second

 

* The coordinates appear to be based on the Universal Transverse Mercatur (UTM) 

projection of the 1983 North American Datum (NAD83).

** 1 gram/second is an assumption called unit emission that simplifies modeling. Actual 

emission rates or regulatory limits can be applied to the results of modeling a unit

emission rate after dispersion modeling.
II-2
III-1

III. Meteorological Data

In November 2000, U.S. EPA obtained and prepared five years of hourly meteorological data in 

the vicinity of the Onyx facility for use in the dispersion modeling. A draft report describing the 

source data, input assumptions, and how the data was processed is included in Attachment 1. 

The report includes the original meteorological data processing as well as additional revisions to 

the meteorological processing made in May 2005. 

Onyx’s consultant also prepared five years of hourly meteorological data for use in dispersion 

modeling. U.S EPA noted a number of differences between U.S. EPA’s original air modeling 

and that described in Onyx’s report. Attributes of Onyx’s modeling that differed with U.S. 

EPA’s original approach, but were based on site-specific information and consistent with the 

Draft HHRAP, were adopted by U.S. EPA for the dispersion modeling described herein. These 

instances will be described in detail in subsequent sections where appropriate. 

Ultimately, Onyx’s meteorological data remained different from U.S. EPA’s data in several 

respects (for example, U.S EPA combined upper air data from Salem and Peoria, Illinois for the 

modeling while Onyx used data from Monett, Missouri). Before further investigating these 

differences, U.S. EPA tested the dispersion model for sensitivity to the meteorological data by 

running the dispersion model for a select group of sensitive receptors (primarily the lakes at 

Frank Holten State Park). U.S. EPA discovered that total deposition of particle bound or vapor 

contaminants did not significantly change between meteorological data files (See Table III-1). 

Total deposition of vapor from all stacks combined averaged six percent higher using the Onyx 

meteorological data. Differences in total deposition of particle bound contaminants from Stack 4 

between meteorological data files were less than one percent. The final dispersion modeling 

described herein was prepared using Onyx’s meteorological data.

Table III-1 Deposition Rate Comparisons – U.S. EPA Modeling with Varying Input Options

Meteorological 

Data Source

Particle Data 

Source

Total Particle Bound

Deposition – All Stacks

Total Vapor Deposition 

– All Stacks

Total Particle Bound 

Deposition – Stack 2

U.S. EPA Stack 4 0.00681 0.0176

Onyx Stack 4 0.00680 0.0186 0.0024

Onyx U.S. EPA HHRAP 0.0012

Note: 1) All deposition values in grams/square meter/year

2) Deposition rates here are from provisional modeling runs and differ slightly from the final modeling run 

summarized in the table at the end of the report.

A. Anemometer Height

This is the height of the met station tower above the ground surface. The instrument tower at 

Lambert Field, St. Louis, Missouri, station number 13994, for the period 1984-1989 was 6.096 

meters (20ft) above the ground surface. Onyx’s modeling initially used a value of 10 meters for 

the anemometer height, which corresponds to the current station height. However, at the time of 

the measurements used for the dispersion modeling, the height was 6.096 meters. Subsequent 

meteorological data files prepared by Onyx, including those used in the latest U.S. EPA 

modeling use the correct value.
III-2

B. Surface Roughness Length at Measurement Site

Surface roughness height—also referred to as (aerodynamic) surface roughness length—is the 

height above the ground at which the wind speed goes to zero. Surface roughness affects the 

height above local ground level that a particle moves from the ambient air flow above the ground 

(for example in the plume) into a “captured” deposition region near the ground. That is, ISCST3 

assumes the particle is deposited to the ground at some point above the actual land surface, based 

on surface roughness height. Surface roughness height is defined by individual elements on the 

landscape, such as trees and buildings. The surface roughness over a given area reflects manmade and natural obstructions, and general surface features. The effective surface roughness 

length has been estimated for a number of surface conditions. U.S. EPA originally used a value 

of 0.04, which was an average of all seasonal values for grassland to approximate an airport 

location. Onyx proposed using 0.10 meters (corresponding to grassland during the summer) 

which the Final HHRAP recommends if you are using National Weather Service surface 

meteorological data. The final version of meteorological data used in the dispersion modeling 

used the Final HHRAP recommended value of 0.10 meters.

C. Surface Roughness Length at the Modeled Site

The surface roughness length at the modeled site is a measure of how high above the ground 

surface particles in a plume will transition from plume flow to gravitational deposition. U.S. 

EPA originally used a value of 1.0 meter corresponding to that of an urban area (Draft HHRAP). 

Onyx applied a more site-specific approach, following a Draft HHRAP recommendation to 

divide the area within 3 kilometers of the facility into a number of compass point directions and 

estimate an overall surface roughness based on surrounding land use and wind direction 

frequencies for each compass-point direction. In this manner, Onyx calculated a site-specific 

surface roughness length of 0.62 meters. U.S. EPA conducted an independent calculation using 

digital land use/land cover maps which were revised manually taking into account a 2002 aerial 

photo of the area available on the internet. U.S. EPA obtained the United States Geologic

Survey (USGS) land use/land cover map for St. Louis, Missouri from the 

<http://www.webgis.com> website. The 2002 aerial photo was obtained from the 

<http://www.terraserver.microsoft.com> website. The adjustment was made manually using 

graph paper to assign land use to the areas within a 3-kilometer radius of the facility. 

Attachment 2 contains the figures and spreadsheet output of the calculation. U.S. EPA’s 

calculated site-specific surface roughness length of 0.60 meters was similar to that calculated by

Onyx. The current modeling is based on Onyx’s calculated value of 0.62 meters.

D. Minimum Monin-Obukhov Length

U.S. EPA originally based this parameter (pertaining to atmospheric stability) at 50 meters for an 

urban area. Subsequently, U.S. EPA agreed to use the Onyx recommended value, setting the 

minimum Monin-Obukhov Length to 75 meters, the average value for compact 

residential/industrial and commercial (19-40 story) buildings.
III-3

E. Noon Time Albedo

Albedo (the fraction of incoming solar radiation reflected back into the atmosphere) is used in 

calculating the heat balance at the surface of the earth and is used to adjust the Monin-Obukhov 

Length on an hourly basis. The noon time albedo is the value of albedo at midday. U.S. EPA 

originally used a value of 0.18, corresponding to the average of all seasonal values for urban land 

use. Onyx applied the approach used for site-specific surface roughness to noon time albedo for 

different land uses taken from Table 3-5, Albedo of Natural Ground Covers for Land Use Types 

and Seasons, in HHRAP. In this way, Onyx calculated a noon-time albedo of 0.22. U.S. EPA 

applied the same approach and estimated noon-time albedo at 0.26. Since the values are similar 

and the HHRAP indicates dispersion modeling results are not particularly sensitive to this 

parameter, U.S. EPA agreed to use the Onyx-suggested value of 0.22. A sensitivity analysis 

conducted by U.S. EPA Region 6 showed that variations in noon time albedo had only slight 

impacts on dry deposition and no effect on air concentrations or wet deposition (U.S. EPA 1997)

F. Bowen Ratio

The Bowen ratio is the ratio of the sensible heat flux to the evaporative or latent heat flux at the 

ground surface. U.S. EPA initially used a Bowen ratio of 1.625 (an average of all seasonal 

values for an urban area). The HHRAP recommends a Bowen ratio of 2.0 for urban areas where 

annual rainfall exceeds 20 inches. Onyx used a value of 2.0 and the meteorological data used for 

the current modeling uses this value. The sensitivity analysis conducted by U.S. EPA Region 6 

showed that variations in Bowen ratio had only slight impacts on dry deposition and no effect on 

air concentrations or wet deposition (U.S. EPA 1997).

G. Fraction of Net Radiation Absorbed at the Ground

Also used for calculating hourly values of Monin-Obukhov length, fraction of net radiation 

absorbed at the ground is the last component of radiative heat balance. U.S. EPA and Onyx both 

used a value of 0.27 for urban areas, as recommended by HHRAP. The U.S. EPA sensitivity

analysis showed that dispersion modeling results were unaffected by variations in the fraction of 

net radiation absorbed at the ground (U.S. EPA 1997).

H. Anthropogenic Heat Flux

Anthropogenic heat is the surface heating caused by human activity, including automobiles and 

heating systems. It is used to calculate hourly L values (Monin-Obukhov lengths). The HHRAP 

gives a table of values of anthropogenic heat flux for a variety of cities around the world. 

U.S EPA originally applied a linear regression to all the cities in the table located between 34 

and 64 North latitude assuming that anthropogenic heat flux was dependent on population 

density. Using the population density for St. Louis (177 person/square kilometer), U.S. EPA 

calculated a value of 5 Watts/square meter for anthropogenic heat flux. Onyx used a value of 20 

Watts/square meter which is also consistent with the HHRAP recommendation for large urban 

areas. The current modeling used the HHRAP recommended value of 20 Watts/square meter. 

The U.S. EPA sensitivity analysis showed that dispersion modeling results were unaffected by 

variations in anthropogenic heat flux (U.S. EPA 1997).
III-4

I. Incoming Solar Radiation and Leaf Area Index

Incoming solar radiation and leaf area index are used by the dispersion model to calculate a 

varying dry vapor deposition velocity, a key parameter for evaluating dry vapor deposition. The 

latest version of HHRAP recommends evaluating dry vapor deposition for mercury using the 

TOXICS model option in the dispersion model. The option allows the user to enter a constant 

dry vapor deposition velocity or let the model perform complex calculations to derive the 

velocity. Even though U.S EPA and Onyx both used a constant dry vapor deposition velocity, as 

recommended in HHRAP, the meteorological data file must be formatted to include columns for 

incoming solar radiation and leaf area index or the TOXICS model option for dry vapor 

deposition will not run. For all model runs calculating dry vapor deposition, two additional 

columns of blank or zero values were added to the final processed meteorological data file.

J. Pre-processed Meteorological File

The surface weather data from the National Weather Service weather station at Lambert Field, 

St. Louis, Missouri was combined by Onyx with upper air data from Monett, Missouri and the 

parameters above in order to create one combined pre-processed data file. Onyx did so for each 

of five years and ultimately performed five individual sets of dispersion modeling. Jeff Sprague, 

of the Illinois Environmental Protection Agency (IEPA), combined Onyx’s yearly

meteorological files into one concatenated file for a 5-year period. This file was used in the 

current version of dispersion modeling with the exception of the vapor runs wherein placeholder 

columns were added for incoming solar radiation and leaf area index.
IV-1

IV. Study Area

A. Receptor Grid

U.S. EPA modeled dispersion of stack emissions over a 20 kilometer by 20 kilometer area (just 

over 154 square miles) surrounding the facility. Receptor locations were defined every 100 

meters to a distance of four kilometers from the center of the facility (a point set halfway

between Stacks 2-3 and Stack 4). Additional receptors were defined every 500 meters to a 

distance of 10 kilometers from the facility. See Figure IV-1 for the receptor grid.
IV-2

The receptor grid was prepared using AERMOD-View version 5.1, a windows-based interface 

for running U.S.EPA approved dispersion models developed by Lakes Environmental Software 

of Waterloo, Ontario. 

B. Terrain

Elevated terrain in the vicinity of the stacks can have a significant impact on the results of air 

modeling. Onyx’s stacks are located on Mississippi River bottomland with nearby bluffs rising 

as much as 150 feet (44 meters) above the top of Onyx’s highest stack. In order to properly 

handle terrain effects, each receptor point must have a corresponding elevation. 

USGS 7.5 Minute Digital Elevation Models (DEMs) with 30 x 30 meter samples (of elevation) 

were used to obtain the elevations and were already available on the Agency’s server. The 

following specific DEMs were used: Cahokia, IL; Clayton, MO; French Village, IL; Granite 

City, IL; Monks Mound, IL; and Webster Grove, IL. The Clayton, French Village, and Monks 

Mound DEMs were found to be in a different projection than the default projection selected for 

the modeling (NAD83). 

U.S. EPA used ARCGIS version 8.3 (a computer based Geographical Information System – GIS 

– developed by ESRI of Redlands, California) to convert the DEMs from the 1927 North 

American Datum (NAD27) to NAD83. ARCGIS was also used to ensure that elevation values in 

the DEMs were in the same units (meters). The DEMs were sampled in ARCGIS to derive an 

elevation for each receptor point. The UTM coordinates of the receptor grid points were 

combined with their respective elevations into a text file which was used to import elevations 

into the dispersion model. See Figure IV-2 for elevations in meters within the receptor grid. 
IV-3
V-1

V. Dispersion Modeling

U.S. EPA used the Industrial Source Complex – Short Term model, Version 3 (ISCST3) to 

model dispersion of stack emissions from the Onyx facility. ISCST3 is a steady-state Gaussian 

plume model which can be used to assess pollutant concentrations and/or deposition fluxes from 

a wide variety of sources associated with an industrial source complex. The model was 

embedded within AERMOD-View which was used for the current modeling runs.

A. Partitioning of Pollutant into Different Phases

Hazardous constituents are assumed to be emitted and dispersed from the stack in three different 

ways. Volatile contaminants are expected to be emitted in the vapor phase. Some non-volatile 

contaminants are expected to be emitted as particles and others are expected to be emitted while 

absorbed onto the surface of particles (known as particle-bound). The three types of emissions 

were modeled assuming a unit emission rate (1 gram/second). The dispersion results were scaled 

to reflect actual emissions or regulatory limits as part of the risk assessment.

B. Particle Emissions

U.S. EPA selected the following model options to model particle emissions:

wet deposition (particles brought to the ground by precipitation);

dry deposition (particles fall to the ground by gravity);

total deposition (wet and dry added together); and 

wet and dry plume depletion (deposited particles are subtracted from the plume mass).

In order to run these options, ISCST3 requires a particle size distribution of stack particles and 

and an estimate of their density. In March of 2005, Onyx conducted stack testing on the rotary

kiln and stack 4 for particle size distribution. Stacks 2 and 3, however, were not tested. On 

October 14, 2005, Onyx submitted a detailed rationale for applying the stack 4 particle data to 

stacks 2 and 3 based on similarities in air pollution control systems (Onyx 2005b). U.S. EPA 

ultimately used the particle data from the stack 4 test in part because it resulted in more 

conservative particle bound deposition (see V.C. below). The following table of particle data is 

from the October 2005 Onyx Report:
V-2

Table V-1 Onyx Environmental Services Rotary Kiln and Fixed Hearth Incinerators Human Health Risk 

Assessment Report, October 2005, Franklin Engineering Group, Inc.

C. Particle Bound Emissions

U.S. EPA selected the same modeling options for the particle bound emissions as were selected 

for particle emissions:

wet deposition (particles brought to the ground by precipitation);

dry deposition (particles fall to the ground by gravity);

total deposition (wet and dry added together); and 

wet and dry plume depletion (deposited particles are subtracted from the plume mass).

The amount of a particle bound pollutant present on a given particle is assumed to be directly 

proportional to surface area since the contaminant is absorbed to the surface. In order to account 

for this, HHRAP recommends that the particle size distribution be adjusted for relative particle 

surface area assuming the particles are spherical. The column in Table V-1 labeled Fraction of 

Total Surface Area is based on this adjustment and is entered as the mass fraction for particle 

bound contaminants.

Based on the March 2005 stack 4 sampling and analysis for particle size distribution and 

mercury speciation and the detailed rationale submitted in October, Onyx recommended 

applying the stack 4 particle data to stacks 2 and 3. U.S. EPA believes there are still too many

differences in the design and operation of the incinerators (rotary kiln versus dual-chamber/fixed 

hearth for example) to completely accept this rationale. U.S. EPA tested stack 2 and 3 particle 

bound deposition results using stack 4 particle data and an example of particle data from 

HHRAP consistent with combustion facilities equipped with either electrostatic precipitators or 
V-3

fabric filters. The site-specific particle size distribution (adjusted for surface area) from stack 4 

resulted in higher total deposition rates at the Lakes at Frank Holten State Park (the critical 

receptor location for mercury emissions) than the example particle size distribution in HHRAP. 

In the absence of stack-specific data for stacks 2 and 3, U.S. EPA used the particle data which 

resulted in higher deposition at the lakes, the stack 4 data, for the current round of modeling. 

D. Vapor Emissions

U.S. EPA originally modeled only wet deposition of vapor. The finalized HHRAP included a 

protocol for modeling dry deposition as well. The new protocol, using the TOXICS model 

option in ISCST3, is run with some chemical specific data. Since mercury emissions are the 

primary concern and no other volatile emissions were risk drivers, the new dry vapor deposition 

modeling was focused on emissions of divalent mercury vapor. To run the model, HHRAP 

recommends that a constant dry vapor deposition velocity be entered. According to HHRAP, a 

default value of 2.9 centimeters/second for divalent mercury can be used. U.S. EPA found the 

approach acceptable and attempted to model dry vapor deposition based on input files prepared 

by Onyx. It was discovered that these files contained a unit error. ISCST3 requires that the 

deposition velocity be entered in meters/second whereas the guidance refers to 

centimeters/second. The Onyx input files were prepared with a value of 2.9 as opposed to the 

correct value of 0.029. U.S. EPA made the correction for this round of modeling. The 

correction resulted in a decrease of vapor deposition at the Lakes of Frank Holten State Park. 

U.S. EPA attempted to evaluate possible site specific dry vapor deposition velocities, however, it 

became apparent that the default value would be slightly more conservative and U.S. EPA 

retained the Onyx suggested value of 2.9 centimeters/second (entered as 0.029 meters/second).

E. Dispersion Coefficients

ISCST3 requires the user select rural or urban dispersion coefficients. HHRAP recommends that 

the selection be based on surrounding land use. Urban land use is typically defined by land use 

that has less than 35% vegetative cover. Many different land use types are then divided into 

urban and rural on this basis. As recommended by HHRAP, the surrounding land use is 

considered urban if it is greater than 50% of the total. Onyx conducted this procedure and 

concluded that the land use was close to 50% urban, making it difficult to assign the dispersion 

coefficients. Onyx agreed to evaluate both conditions for all of its modeling runs. U.S. EPA 

independently conducted a similar analysis and concluded the area was urban (57%). U.S. EPA 

further reviewed the land use upwind of the stacks from the perspective of the Lakes at Frank 

Holten State Park. For the purpose of dispersion coefficients, and other parameters that 

influence the wind profile, it is recommended that the upwind fetch be used to determine the 

value, especially for elevated sources like stacks. Essentially, the plume behavior is assumed to 

be more dependent upon the profile of the wind arriving at the stack from upwind so the upwind 

land use is used for these determinations. U.S. EPA determined that the upwind land use (to the 

west) was decidedly urban. Therefore, the current modeling runs were based on urban dispersion 

coefficients.
V-4

F. Input and Output

As stated previously, U.S. EPA prepared the modeling input files based on those provided by 

Onyx. A new receptor grid was generated and terrain was reimported. The only other change 

was the correction of the dry vapor deposition velocity as described in V.D. above. The model 

generated 1-hour and annual plotfiles for air concentration, wet deposition, dry deposition, and 

total deposition each for vapor, particle and particle bound. The files are included on a CD in 

attachment 3. The following table demonstrates the changes in air concentration and deposition 

estimates as the modeling was revised and corrected over time. The results are focused on the 

lakes and Frank Holten State Park since the risk assessment was most sensitive to mercury

impacts through contaminated fish consumption.
V-1

Average Annual Air Concentrations and Deposition Fluxes for 11 locations over the 2 lakes at Frank Holten State Park.

Modeling Date Stack 4 Stack 2 or 3α

Particle-Bound Vapor Particle-Bound Vapor

Air 

Concentration

(μg/m3)

Total 

Deposition

(g/m2/yr)

Air 

Concentration

(μg/m3)

Total 

Deposition

(g/m2/yr)

Air 

Concentration

(μg/m3)

Total 

Deposition

(g/m2/yr)

Air 

Concentration

(μg/m3)

Total 

Deposition

(g/m2/yr)

January 2001 0.013 0.0013 0.0133 0.00035 0.009 0.00585 0.01122 0.00052

June 2005 0.0089 0.0023 0.0094 0.00042 0.0106 0.0016 0.011 0.00048

October 2005 0.0104 β0.00250 β0.01077 0.00047

0.0104 γ0.00156γ

April 2006 0.0096 0.0021 0.0062 0.0058 0.0111 0.00246 0.00694 0.0065

α results from stacks 2 and 3 are considered comparable because each serve nearly identically designed and operated incinerators and are located only

54 meters apart

β based on stack 4 particle data 

γ based on HHRAP example particle data
VI-1

VI. References

Onyx, 2004, Onyx Environmental Services Rotary Kiln and Fixed Hearth Incinerators, 

Screening Level Human Health Risk Assessment Report, Onyx Environmental Services, 

Inc., September 8.

Onyx, 2005a, Onyx Environmental Services Rotary Kiln and Fixed Hearth Incinerators, 

Screening Level Human Health Risk Assessment Report, Onyx Environmental Services, 

Inc., May.

Onyx, 2005b, Correspondence with T. Ramaly, U.S. EPA via electronic mail with attached 

document Determination of Appropriate Particle Size Distribution and Mercury 

Speciation to be Utilized for the Fixed Hearth and Rotary Kiln Incinerators, David 

Klarich, Onyx Environmental Services, Inc., October 14.

Onyx, 2005c, Onyx Environmental Services Rotary Kiln and Fixed Hearth Incinerators, 

Screening Level Human Health Risk Assessment Report-Revised, Onyx Environmental 

Services, Inc., October 27.

U.S. EPA, 1997, Model Parameter Sensitivity Analysis, U.S. EPA Region 6 Center for 

Combustion Science and Engineering, Dallas, Texas, May 23.

U.S. EPA, 1998, Human Health Risk Assessment Protocol for Hazardous Waste Combustion

Facilities, Peer Review Draft, Office of Solid Waste and Emergency Response, EPA530-

D-98-001A, July.

U.S. EPA, 2003, Letter to Onyx with attached draft permit, U.S. EPA, R5, Waste Management 

Branch, June 5.

U.S. EPA, 2005, Human Health Risk Assessment Protocol for Hazardous Waste Combustion

Facilities, Office of Solid Waste and Emergency Response, EPA530-R-05-006, 

September.
Attachment 1

TWI-incinerator, Sauget, Illinois

Air Modeling
2

TWI-incinerator, Sauget, Illinois

Air Modeling

Creating met data files for TWI

April 2000

Downloaded Samson files for St. Louis (Lambert Field) for 1985-1989

Stl-85.dat

Stl-86.dat

Stl-87.dat

Stl-88.dat

Stl-89.dat

Downloaded SCRAM upper air files from Salem, Illinois for 1985-1987

03879-85.txt

03879-86.txt

03879-87.txt

Downloaded SCRAM upper air files from Peoria, Greater Peoria Airport for 1988-1989

14842-88.txt

14842-89.txt

November 2000

1) Filled in missing data point in Stl-85.dat - new file Stl-85A.dat

5/19/85 0600hrs - missing dew point - extrapolated 0400-0700hrs - 10.0C

2) Prepared TWI85.met file using RAMMET-View using Stl-85A.dat and 03879-85.txt

Options for wet deposition:

anemometer height = 6.096m

Monin-Obukhov length = 50m (urban)

Surface Roughness Length (measurement site) = 0.04m (average of all seasonal grassland 

values to approximate an airport)

Surface Roughness Length (application site) = 1.00m (urban)

Noon-time Albedo = 0.18 (average of all seasonal urban 

values)

Bowen Ratio = 1.625 (average of all seasonal urban 

values under average conditions)

Anthropogenic Heat Flux = 5 W/m2(linear regression of population 

density vs. flux for locations of mid to high 

latitudes)

The St. Louis metropolitan area has a population reported by the U.S. Census Bureau of 

2,444,099 and a population density of 177 persons per km

2

. The population density was input to 

a linear regression of the flux and population density values provided as examples. Hong Kong 
3

and Singapore were not used as they appeared to be outliers in this comparison. The remaining 

dataset comprised cities within 34 to 64 N latitude.

Fraction of Net Radiation Absorbed at Ground = 0.27 (urban)

3) Filled in missing data points in Stl-86.dat - new file Stl-86A.dat

2/1/86 0100hrs - missing ceiling height - extrapolated 2400-0200hrs - 1145m

2/22/86 1300hrs - missing ceiling height - extrapolated 1100-1500hrs - 77777m

4) Prepared TWI86.met file using RAMMET-View using Stl-86A.dat and 03879-86.txt. Same 

options for wet deposition as for 1985.

5) Filled in missing data points in Stl-87.dat - new file Stl-87B.dat

12/30/87 2400hrs - 12/31/87 2400hrs - missing wind speed and wind direction - extrapolated 

linearly from 12/30/87 1100hrs - 1/1/88 1200hrs (no other pattern, daily or otherwise apparent)

12/31/87 2400hrs - missing dew point - extrapolated 12/29/87 - 1/2/88 - 9.5C

12/31/87 2400hrs - missing visibility - extrapolated 2300hrs - 1/1/88 0100hrs - 24.1 km

12/31/87 2400hrs - missing ceiling height - extrapolated 2300hrs - 1/1/88 0200hrs - 77777m

6) Prepared TWI87.met file using RAMMET-View using Stl-87B.dat and 03879-87.txt. Same 

options for wet deposition as for 1985.

7) Filled in missing data points in Stl-88.dat - new file Stl-88A.dat

12/31/88 2400hrs - missing wind direction - extrapolated 2000hrs - 1/1/89 0300hrs - 298

12/31/88 2400hrs - missing wind speed - extrapolated 2100hrs - 1/1/89 0300hrs - 2.5m/s

12/31/88 2400hrs - missing dew point - extrapolated 2300hrs - 1/1/89 0100hrs - 0.9C 

12/31/88 2400hrs - missing visibility - extrapolated (logarithmic) 2000hrs - 1/1/88 0400hrs - 2.6 

km

12/31/88 2400hrs - missing ceiling height - extrapolated 2000-2300hrs - 90m (low ceiling gave 

way quickly to clear skies by 0100 1/1/89. . . couldn’t extrapolate. Other trends in weather data 

seemed to indicate that the weather change happened after 2400 based on visually examining

graphs of the data, therefore, the clearing sky was also assumed to happen after 2400hrs)

8) Prepared TWI88.met file using RAMMET-View using Stl-88A.dat and 14842-88.txt. Same 

options for wet deposition as for 1985.

9) Filled in missing data points in Stl-89.dat - new file Stl-89A.dat

12/31/89 2400hrs - missing wind direction - extrapolated 1900-2300hrs - 237

12/31/89 2400hrs - missing wind speed - extrapolated 1900-2300hrs - 3.5m/s

12/31/89 2400hrs - missing dew point - extrapolated 1900-2300hrs - -1.9C 

12/31/89 2400hrs - missing visibility - set equal to 2300hrs (no trend noticed) - 24.1 km

12/31/89 2400hrs - missing ceiling height - extrapolated 1900-2300hrs - 1349m

10) Prepared TWI89.met file using RAMMET-View using Stl-89A.dat and 14842-89.txt. Same 

options for wet deposition as for 1985.

11) Re-prepared met files for 1988 and 1989 changing the station location number in the upper air 

files from Greater Peoria Airport, Peoria, Illinois to match the Salem, Illinois upper air files. 

RAMMET-View would not combine the five years into one file if the same upper air stations 

hadn’t been used throughout. Upper air files 14842-88.txt and 14842-89.txt were changed to 
4

03879A88.txt and 03879A89.txt, respectively. 

12) A five-year met file, TWI85-89.met, was created by a RAMMET-View utility from TWI85.met, 

TWI86.met, TWI87.met, TWI88A.met, and TWI89A.met.

May 2005

Based on information provided by Onyx/TWI, including more site specific met processing information, 

the MET data was updated for new modeling runs. The met data was reviewed again for missing data and 

re-processed with the following parameters changed from those originally used in step 2) from November 

2000 above:

Monin-Obukhov length was changed from 50m (urban) to 75m (average of urban - 50m and commercial -

100m)

Surface Roughness Length (measurement site) was changed from 0.04m (average of all seasonal 

grassland values to approximate an airport) to 0.10m (HHRAP recommendation for airports)

Surface Roughness Length (application site) was changed from 1.00m (urban) to 0.62m based on 

surrounding land use (Onyx/TWI referred to HHRAP methodology).

Noon-time Albedo was changed from 0.18 (average of all seasonal urban values) to 0.22 based on 

surrounding land use (Onyx/TWI referred to HHRAP methodology).

Bowen Ratio was changed from 1.625 (average of all seasonal urban values under average conditions) to 

2.0 (Onyx/TWI referred to HHRAP methodology).

Anthropogenic Heat Flux was changed from 5 W/m2(linear regression of population density vs. flux for 

locations of mid to high latitudes) to 20 W/m2(HHRAP default for urban areas).

1) Surface and upper air data for 1985, Stl-85.dat and 03879-85.txt, were checked for missing data 

using using Rammet-View version 4.8, a Meteorological Pre-Processor developed by Lakes 

Environmental Software of Waterloo, Ontario. The met files were checked for missing data using 

Rammet View’s “grid-preview” feature. The “grid-preview” feature allows the user to review the 

data and sort the columns numerically, so that blanks or a field of nines (commonly used to 

designate missing data) could be identified. Missing data was identified and remedied as follows 

(in accordance with Procedures for Substituting Values for Missing NWS Meteorological Data 

for Use in Regulatory Air Quality Models, Atkinson, Dennis, and Russell F. Lee, July 7, 1992). 

No critical missing data were identified. The surface and upper air files for 1985 were combined 

into combined met file <NewTWI85.met>.

2) Surface and upper air data for 1986, Stl-86.dat and 03879-86.txt were checked for missing data in 

the same manner and two data points were missing. Ceiling height for 0100hrs, 2/1/86 was filled 

in with the ceiling height from the preceding hour, 1,070m, since cloud cover was greater than 

nine tenths. Ceiling height for 1300hrs, 2/22/86 was filled in with the ceiling height representing 

unlimited ceiling, 77,777m, since cloud cover was less than five tenths. The updated surface file 

was labeled <Stl-86B.dat> and the combined processed met file <NewTWI86.met> was 

generated from the surface and upper air files.

3) All wind speeds and wind directions on 12/31/87 were missing from the surface data file. U.S. 

EPA decided to try to find another complete year rather than try to fill in so many missing hours. 
5

Accordingly U.S. EPA downloaded the Samson file, <13994_84.sam>, already converted to 

ASCII format, from the WebMet web site <http://www.webmet.com/> for the St. Louis (Lambert 

Field) Airport, station number 13994 for 1984. U.S. EPA obtained the upper air file, <14842-

84.txt> from the WebMet web site <http://www.webmet.com/> for the Greater Peoria Airport, 

Peoria, Illinois, station number 14842 for 1984 since the Salem site data was limited to 1985 

through 1987. A check using Rammet-View revealed no missing critical data from either file. 

All station information within the Peoria upper air file were changed to match the station ID at 

Salem, Illinois in order to avoid problems when combining the whole 5 years of met data. The 

upper air file was also renamed <03879A84.txt> and was combined with <13994_84.sam> into 

the processed file <NewTWI84.met>.

4) Missing data for 1988 was filled in the same manner as originally described above except that the 

ceiling height for 2400 hrs, 12/31/88 was filled in with the ceiling height from the preceding hour 

since cloud cover was greater than nine tenths. The updated surface file was labeled <Stl88B.dat> and the combined processed met file <NewTWI88.met> was generated from the surface 

and upper air files. Note, the upper air file for 1988 was for data collected at the Greater Peoria 

Airport, Peoria, Illinois, station number 14842 since the Salem site data was limited to 1985 

through 1987. All station information within the Peoria upper air file were changed to match the 

station ID at Salem, Illinois in order to avoid problems when combining the whole 5 years of met 

data. The upper air file was also renamed <03879A88.txt> before being processed with the 

surface file.

5) The existing missing data remedies completed for the 1989 files completed in November 2000 

were retained as is. A new met file <NewTWI89.met> was generated from the updated files 

<Stl-89A.dat> and <03879A89.txt>. Note that the upper air data was collected at the Greater 

Peoria Airport, Peoria, Illinois, station number 14842, since the Salem site data was limited to 

1985 through 1987. All station information within the Peoria upper air file were changed to 

match the station ID at Salem, Illinois in order to avoid problems when combining the whole 5 

years of met data.

6) The processed met data from 1984, 1985, 1986, 1988, and 1989 were combined into one 5-year 

file, <TWI8489.met>.
Attachment 2

Independent Calculation of Site-Specific Surface Roughness Length

Figures and Spreadsheet
2

Title: Land Use/Land Cover

Legend: pink urban, commercial, or industrial areas

yellow agricultural

blue water

green striped wetland

green deciduous forest

brown barren land
3

2002 Urban Areas Aerial Photo from < http://www.terraserver.microsoft.com>
4

Modified land use/land cover based on 2002 aerial photo and superimposed with a 3-

kilometer radius circle divided into 16 compass point directions.
5

Onyx/TWI Surface Roughness, Noon Time 

Albedo

Using Land Use/Land Cover updated by Urban 

Areas Aerial Photo

surface 

roughness

annual 

average

http://www.terraserver.microsoft.com urban 1 barren land 0.2625

as 

desert

0.161

deciduous 

forest 0.9 wetland 0.1625

39.174 blocks per slice 0.04025

confirerous 

forest 1.3 water 0.0001

agricultural 

land 0.0725 grassland 0.04025

compass 

point

urban 

blocks percent

forest 

blocks percent

agricultural 

blocks percent

wetland 

blocks percent barren percent

water 

blocks percent grassland percent total

Compass 

Point 

Wind 

Frequency Compass Point 

direction

Surface 

Roughness

(blowing 

from)

Surface 

Roughness

Weighted for 

Wind 

Frequency

N 14 35.74% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 18 45.95% 7.174 18.31% 39.174 0.36 4.09% 0.0149

NNE 13.67 34.90% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 25.504 65.10% 39.174 0.38 3.62% 0.0136

NE 31.17 79.57% 0 0.00% 1 2.55% 0 0.00% 0 0.00% 0 0.00% 7.004 17.88% 39.174 0.80 3.67% 0.0296

ENE 29.174 74.47% 0 0.00% 1 2.55% 0 0.00% 0 0.00% 0 0.00% 9 22.97% 39.174 0.76 3.03% 0.0229

E 17.924 45.75% 0 0.00% 0.25 0.64% 0 0.00% 0 0.00% 1 2.55% 20 51.05% 39.174 0.48 4.12% 0.0197

ESE 12.174 31.08% 0 0.00% 17.5 44.67% 0 0.00% 0 0.00% 0 0.00% 9.5 24.25% 39.174 0.35 6.39% 0.0225

SE 14.674 37.46% 0 0.00% 12.5 31.91% 0 0.00% 0 0.00% 0 0.00% 12 30.63% 39.174 0.41 7.36% 0.0302

SSE 28.674 73.20% 0 0.00% 5 12.76% 0 0.00% 0 0.00% 0 0.00% 5.5 14.04% 39.174 0.75 7.85% 0.0586

S 26.174 66.81% 0 0.00% 13 33.19% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 39.174 0.69 10.06% 0.0696

SSW 9.674 24.69% 0 0.00% 27.5 70.20% 2 5.11% 0 0.00% 0 0.00% 0 0.00% 39.174 0.31 5.21% 0.0160

SW 8.174 20.87% 5 12.76% 8 20.42% 9 22.97% 0 0.00% 9 22.97% 0 0.00% 39.174 0.38 5.54% 0.0208

WSW 22.174 56.60% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 17 43.40% 0 0.00% 39.174 0.57 6.77% 0.0383

W 34.424 87.87% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 4.5 11.49% 0.25 0.64% 39.174 0.88 6.63% 0.0583

WNW 34.424 87.87% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 4 10.21% 0.75 1.91% 39.174 0.88 9.23% 0.0812

NW 34.424 87.87% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 4 10.21% 0.75 1.91% 39.174 0.88 7.30% 0.0642

NNW 32.174 82.13% 0 0.00% 0 0.00% 0 0.00% 0 0.00% 6 15.32% 1 2.55% 39.174 0.82 4.55% 0.0375

95.42%

363.102 57.93% 5 0.80% 85.75 13.68% 11 1.75% 0 0.00% 63.5 10.13% 98.432 15.70% 626.784 0.598 meters

total 

blocks

wind frequency 

weighted 

surface 

roughness
Attachment 3

Air Modeling Files – Electronic Format