DRAFT 

Date: May 25, 2010 

Subject: Model Plant Data Used to Estimate Risk from Chromium Electroplating Sources 

 Emission Standards Technical Support and Post Promulgation Activities 

 EPA Contract No. EP-D-06-118; EPA Work Assignment No. 4-6 

 RTI Project No. 0210426.004.006 

From: Richard Marinshaw 

To: Phil Mulrine, EPA/OAQPS/SPPD/MMG 

The purpose of this memorandum is to provide the basis for the model plant parameter 

data used to assess the risk from chromium electroplating facilities subject to the national 

emission standards for hazardous air pollutants (NESHAP) for Hard and Decorative Chromium 

Electroplating and for Chromium Anodizing Tanks (40 CFR 63, subpart N). Section I of this 

memorandum provides background information on the decision to use model plant data, and 

Section II provides the basis for the data modeled. 

I. Background

There are estimated to be about 1,770 chromium electroplating plants in operation in the 

U.S.1

 This total includes plants that perform hard chromium electroplating, decorative 

chromium electroplating, and chromium anodizing. However, emissions data were available, 

through the NEI database and other plant-specific information on file, for only about 120 plants 

when the initial risk modeling for chromium electroplating was performed. Table 1 shows a 

breakdown of the number of plants by process type and the number with available data. 

Table 1. Availability of Data on Emissions from Chromium Electroplating Plantsa

Process 

Estimated No. of 

plants 

No. of plants with available 

emissions data 

Hard chromium electroplating 790 38 

Decorative chromium 

electroplating 

740 81 

Chromium anodizing 240 5 

Total 1,770 124 

a

 Reference 1. 

In order to better characterize the risk associated with emissions from chromium 

electroplating sources nationwide, the decision was made in July-August of 2009 to model all the 

plants with known addresses using model plant emissions data. The following section describes 

the model plant data used and the basis for the data. 
2 

II. Basis for Model Plant Data

 The first step in this process was to assign emissions to each type of plant to be modeled. 

For the NESHAP, eight model plants had been developed: three plants for hard chromium 

(small, medium, large), three plants for decorative chromium (small, medium, large), and two 

plants for anodizing (small, large).2

 The model plants were based on data collected from more 

than 100 facilities that responded to an information collection request for the chromium 

electroplating industry. Data from site visits and other information also were used in developing 

the model plants. A complete description of the model plants developed for the NESHAP is 

provided in Reference 2, the Background Information Document for the proposed NESHAP 

(Chromium Electroplating BID). 

 The Chromium Electroplating BID included estimates of uncontrolled chromium 

emissions for each type of model plant. Controlled emissions were estimated by applying the 

control efficiencies developed for the NESHAP. For hard chromium electroplating, the control 

efficiency was based on the performance of composite mesh pads; for decorative chromium 

electroplating and for chromium anodizing the control efficiency was based on the performance 

of wetting agent fume suppressants. Table 2 shows the estimated uncontrolled and controlled 

emissions for each type of model plant. 

Table 2. Chromium Electroplating Model Plant Emissionsa

Chromium Compound Emissions, 

lbs/yr 

Process Control level Small Medium Large 

Hard chromium Uncontrolled (0%) 110 926 3,530 

Controlled (99%) 1.1 9.26 35.3 

Decorative chromium Uncontrolled (0%) 13 53 530 

Controlled (99.5%) 0.065 0.27 2.65 

Chromium anodizing Uncontrolled (0%) 7.2 88 

Controlled (99.5%) 0.036 0.44 a

 Reference 2. 

 To model worst-case emissions, consideration was given to modeling all plants using 

data for the "large" size of model plant for each type of process. Based on the available data on 

actual emissions, this approach seemed reasonable for decorative chromium electroplating and 

for chromium anodizing. However, that was not the case for hard chromium electroplating. 

Based on data provided in the permit application for the Empire Hard Chrome, Kostner Avenue 

plant, located in Chicago, RTI estimated emissions of chromium compounds at the emission 

limit for typical operating hours to be about 31 pounds per year (lbs/yr). Because this facility is 

supposedly the largest hard chromium plant in the U.S., it serves as an upper bound for 

emissions from hard chromium electroplating. However, the estimated emissions for the Empire 

Hard Chrome plant is less than the estimated emissions for a large hard chromium model plant 

(35.3 lbs/yr). As a result, it was considered unreasonable to use the large model plant emissions 

value to estimate emissions for all hard chromium electroplating plants nationwide. Instead, the 
3 

decision was made to model hard chromium plants with the emission rate for a medium-size hard 

chromium model plant (9.26 lbs/yr). The final emissions rates modeled were as follows: 

Hard chromium electroplating: 9.26 lbs/yr 

Decorative chromium electroplating: 2.65 lbs/yr 

Chromium anodizing: 0.44 lbs/yr 

 Based on actual emissions data available, these emission rates seem reasonable for 

representing worst-case emissions. For hard chromium electroplating, the available data are 

generally on the order of a few pounds per year. For decorative chromium electroplating, actual 

data indicate emissions are generally less than 1 lb/yr. No actual data were available for 

chromium anodizing, but those facilities tend to be smaller, and there is no reason to believe that 

the large model plant emissions of 0.44 lbs/yr would not be a good estimate of worst-case 

emissions. 

 The next step was to assign a model plant and emissions to each of the 1,629 plants with 

complete addresses listed in the Electroplating Database.3

 However, there was information on 

the type of electroplating performed for only about half of the plants. Furthermore, the available 

information indicated that some plants performed more than one type of chromium 

electroplating. Therefore, to be consistent with the worst-case approach, the following 

assumptions were made: 

• All plants that performed hard chromium electroplating in combination with decorative 

chromium or chromium anodizing would be modeled as hard chromium electroplating. 

• All plants that performed decorative chromium electroplating in combination with 

chromium anodizing would be modeled as decorative chromium electroplating. 

• All plants for which the process was unknown would be modeled as hard chromium 

electroplating. 

 Table 3 summarizes the final assignment of emissions for each type of plant. The table 

also shows the maximum achievable control technology (MACT) codes used in the modeling. 

Table 3. Modeled Emissions by Chromium Electroplating Process Type 

Process 

MACT 

Code 

Number 

of plants 

Emissions, 

lbs/yr 

Hard chromium electroplating only 1615 301 9.26 

Decorative chromium electroplating only 1610 326 2.65 

Chromium anodizing only 1607 73 0.44 

Hard and decorative and/or chromium anodizing 1615M 115 9.26 

Decorative chromium and chromium anodizing 1610M 11 2.65 

Unknown type of electroplating process 1615D 803 9.26 

Total 1,629 
4 

 Other data needed for the risk modeling file included certain stack parameters. Table 4 

summarizes the values used in the modeling for these parameters, which are also based on the 

model plants developed for the NESHAP, as documented in the Chromium Electroplating BID. 

Table 4. Chromium Electroplating Model Plant Parameters Used for Risk Modelinga

Plant type 

Stack 

Height 

(ft) 

Exhaust Gas 

Temperature 

(°F) 

Stack 

Diameter 

(ft) 

Exhaust 

Gas 

Velocity 

(ft/sec) 

Orientation 

of Emission 

Point 

Hard chromium electroplating only 30 80 3.8 50 Vertical 

Decorative chromium 

electroplating only 17 80 4 29 Horizontal 

Chromium anodizing only 17 80 4 29 Horizontal 

Hard and decorative and/or 

chromium anodizing 30 80 3.8 50 Vertical 

Decorative chromium and 

chromium anodizing 17 80 4 29 Horizontal 

Unknown type of electroplating 

process 30 80 3.8 50 Vertical 

a

 Reference 2. 

III. References 

1. Memorandum from R. Marinshaw, RTI International, to P. Mulrine, EPA/OAQPS. 

Estimated Number of Chromium Electroplating Plants. May 24, 2010. 

2. Chromium Emissions from Chromium Electroplating and Chromic Acid Anodizing 

Operations -- Background Information for Proposed Standards, Volume I (EPA 453/R93-030a). U.S. EPA, Office of Air Quality Planning and Standards. July 1993. 

3. Electroplating Database. RTI International. 2010.