1 September 1 , 2010

MEMORANDUM

TO: Phil Mulrine

FROM: Sandy Burns

RTI International

SUBJECT: Maximum Achievable Control Technology (MACT) Allowable Emission

Estimates

Section 112(f)(2) of the Clean Air Act (CAA) directs EPA to assess the risk remaining (residual risk) after the application of maximum achievable control technology (MACT) standards under section 112(d). EPA is to promulgate more stringent standards for a category or subcategory of sources subject to MACT standards under se ction 112(d) if promulgation of such standards is necessary to protect public health with an ample margin of safety or to prevent (taking into consideration various factors) adverse environmental effects.

For the most part, the emissions values from the EPA National Emissions Inventory ( NEI ) represent actual emission levels for steel pickling and HCl acid regeneration operations

. T he use of actual emissions versus the use of “MACT allowable” emissions for residual risk

assessments was discussed both in the final Coke Oven Batteries residual risk rule (70 FR

19998

- 19999, April 15, 2005) and in the proposed and final Hazardous Organic N ational emission standard for hazardous air pollutants (HON) residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76 609, December 21, 2006, respectively). In those previous actions, EPA noted that assessing the MACT allowable levels of emissions (i.e., the highest emission levels that could be emitted while maintaining the same activity level and still complying with t he NESHAP requirements) is inherently reasonable since they reflect the maximum level sources could emit and still comply with national emission standa rds. I t is reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis, in accordance with the Benzene NESHAP. (54 FR 38044, September 14, 1989). S ources typi cally seek to perform

better tha n required by emission standards to allow for variability in manufacturing processes and control device performance. Con sidering only “MACT allowable” emissions data in developing risk estimates would unrealistically inflate estimated risk levels.

T he most prudent approach to a risk assessment of the steel pickling industry is to

consider both the actual emissions and the “MACT allowable” emissions. Hydrochloric acid (HCl ) steel pickling lines are subject to a numeric emission limit of 18 parts per million by2 volume (ppmv) for HCl; HCl regeneration facilities are subject to numeric emission limits of 25 ppmv for HCl and 6 ppmv for chlorine (Cl)

.

Because NEI emissions data are in tons per year (tpy), they cannot be directly compared to allowable emissions. The NEI data set does not contain enough detailed process information to calculate emissions in ppmv (e.g., flow rat e, velocity, operating hours ). Therefore we searched

the permits of steel pickling facilities and HCl regeneration facilities from states that have their permits available online

. We were unable to find an HCl regeneration facility with the appropriate dat a to calculate emissions in ppmv. Out of five steel pickling facilities whose permits we were able to obtain, only one, Charter Steel in Saukville

, Wisconsin, had test data and enough additional process information to calculate emissions in ppmv. We calcul ated actual emissions for this facility at two pickling lines over three years (2007, 200 8, and 2009)

. The

emission concentration of HCl is presented in Table 1, and ranged from 4.63 ppmv to 17.36 ppmv. This level of variability is typical of the industry, and coincides with the variability seen in the NEI data for this source category.

Based on this limited data, and the fact that the allowable emissions for steel picking

facili ties is 18 ppmv, we conclude that actual and allowable emissions are equivalent for this

source category.

Table 1. Calculated HCl concentration from Charter Steel Pickle Line Acid Scrubber Stacks

Device 1

Year HCl concentration (ppmv)

P2 2007 4.63

P3 2007 8.4 0

P2 2008 5.24

P3 2008 17.34

P2 2009 5.36

P3 2009 17.36

References
1. State of Wisconsin Department of Natural Resources, Bureau of Air Management. Charter Steel Emission Summaries, 2007

- 2009. Available at: http://dnr.wi.gov/cias/am/amexternal/AM_PermitTrackingSearch.aspx