Appendix 1 

Emissions Inventory Support Memorandum 
Chromium Electroplating 
1

MEMORANDUM 

TO: Anne Pope, EPA 

FROM: Darcy Wilson, ERG 

DATE: July 19, 2010 

SUBJECT: Emissions Data Used in Residual Risk Modeling for Modeling for 

Chromium Electroplating 

The purpose of this memorandum is to provide information on the RTR database used in 

estimating residual risk for the the three Chromium Electroplating Maximum Achievable 

Control Technology (MACT) source categories—Chromic Acid Anodizing, Decorative 

Chromium Electroplating, and Hard Chromium Electroplating. 

BACKGROUND 

Section 112 of the Clean Air Act (CAA) establishes a two-stage regulatory process to 

address emissions of hazardous air pollutants (HAPs) from stationary sources. In the first 

stage, section 112(d) requires the Environmental Protection Agency (EPA) to develop 

technology-based standards for categories of industrial sources. In the second stage, 

known as the residual risk stage, section 112(f)(2) requires EPA to assess the health and 

environmental risks that remain after sources come into compliance with MACT. If 

additional risk reductions are necessary to protect public health with an ample margin of 

safety or to prevent adverse environmental effects, EPA must develop standards to 

address these remaining risks. As part of this second stage, data were gathered to assess 

the residual risks from the three Chromium Electroplating MACT source categories. 

EMISSIONS DATA USED IN RESIDUAL RISK MODELING 

The 2005 National Emissions Inventory (NEI) data served as the starting point for this 

assessment. Using the process MACT code,1 a subset of the NEI was developed that 

contained facility, process, and emissions data for each facility in the Chromic Acid 

Anodizing source category (MACT code 1607), the Decorative Chromium Electroplating 

source category (MACT code 1610), and the Hard Chromium Electroplating source 

category (MACT code 1615). 

 

EPA evaluated the 2005 NEI Chromium Electroplating subset and noted that the NEI had 

a very limited representation of Chromium Electroplating facilities. An additional data set 

of Chromium Plating facilities was developed to address this situation. This information 

was gathered from EPA Regional offices, State and local agencies, EPA and online 

industry databases, and an Information Collection Request (ICR) for the Plating and 

 

1

 Assigning data with MACT codes allows EPA to determine reductions attributable to the MACT 

program. The NEI associates MACT codes corresponding to MACT source categories with stationary 

major and area source data. 
2

Polishing Area Source NESHAP. Emission estimates were developed for over 1,629 

additional “model” plants based on this data set using information known about the type 

of plating operation at each facility, and surrogate stack parameters. Locational 

coordinates were obtained based on the facility address. For 44 of the model plants, EPA 

was able to develop improved emission estimates (rather than using surrogate emission 

estimates) based on compiled process information for the facilities. 

Risks associated with facilities covered by the Chromium Electroplating MACT 

standards were modeled in the initial 2005 NATA risk assessment in June of 2009. 

NATA comments on the initial risk assessment draft that have been incorporated into the 

2005 NEI include revisions to emissions for one chrome plating facility and identification 

of one closed model plant. EPA also made revisions to the emissions estimate for one 

other facility. 

EPA also evaluated the whole facility risks for Chromium Electroplating facilities using 

the 2005 NEI data and risk assessment results that were released in the 2005 NATA Risk 

Preview with State and local agencies in June of 2010. Emission revisions were made to 

for one facility based on the 2005 NATA Risk Preview comments, and 17 model plants 

were identified as having closed. Based on industry contacts, EPA identified two 

additional facilities that have closed, removed one facility from the Chromium 

Electroplating source category, and made revisions to the emission estimates for nine 

facilities. These revisions were not included in the risk analyses, but will be reflected in 

the final NATA risk assessment.