Date: November 30, 2009

Subject: Revised Sulfur Dioxide MACT Floor, Data Variability Analysis, and Emission Limit for New Large HMIWI EPA Contract No. EP-D-06-118; Work Assignment No. 3-09; SPPD No. 02/30 RTI Project No. 0210426.003.009

From: Thomas Holloway

To: Ketan Patel OAQPS/SPPD/NRCG (E143-03) U.S. Environmental Protection Agency Research Triangle Park, NC 27711

I. Background

On October 6, 2009, the U.S. Environmental Protection Agency (EPA) promulgated its response to the remand of the new source perfor mance standards (NSPS) and emission guidelines (EG) for hospital/medical/infectious waste incinera tors (HMIWI) by the U.S. Court of Appeals for

the District of Columbia Circ uit (the Court) and satisfied the Clean Air Act (CAA) Section 129(a)(5) requirement to conduct a review of the st andards every 5 years. The promulgated rule

revised the NSPS and EG emission limits for all nine of the CAA Section 129 pollutants--— particulate matter, lead, cadmium, mercury, chlori nated dibenzo-p-dioxins/dibenzofurans, carbon monoxide, nitrogen oxides (NO X ), hydrogen chloride, and sulfur dioxide (SO 2 ). Emission limits were revised for all three HMIWI size subcategor ies (large, medium, and small) for the NSPS and all four HMIWI size subcategories (large, medi um, small, and small rural) for the EG.

Following promulgation of the revised emission limits, an industry representative informed EPA of an error in the published NSPS emission limit for NO X for new large HMIWI, which did not appear to reflect EPA’s de scribed analytical process for adopting the revised standards. 1 On review, EPA staff determined that the published revised NO X NSPS for new large HMIWI indeed

did not reflect EPA’s intent in the fi nal rule. Prior to promulgation, the NO X emission limit for new large HMIWI was tentatively estimated to be 150 parts per million by volume, dry basis (ppmvd), based on test data for the best-performi ng unit and taking into account the variability in

the test data. This tentative NO X emission limit for new large HMIWI would be higher than the corresponding NO X emission limit for existing large HMIWI (140 ppmvd). In order to prevent a

situation where a new source would have a less stringent emission limit than an existing source, EPA decided to assign the NO X emission limit for existing large sources as the NO X emission limit for new large sources. However, a NO X NSPS limit of 130 ppmvd was erroneously published, which did not correspond to EPA’s descript ion of its standard-setting process. EPA is proposing to amend the HMIWI NSPS to include the correct NO X NSPS limit of 140 ppmvd for new large HMIWI, which matches the final NO X EG limit and reflects EPA’s intent in the October 6, 2009 final rule. No further analysis is necessar y, and this issue is not discussed any further in

this memorandum.After receiving industry’s notice about the erroneous NO X emission limit, we reviewed the other NSPS and EG emission limits published in the October 6, 2009 notice to look for any similar errors, and we determined th at the published, revised SO 2 NSPS for new large HMIWI also did

not reflect EPA’s intent in the final rule. Th e purpose of this memorandum is to present the methodology and results of the revised NSPS emission limit determination for SO 2

.

II. SO 2 Emission Limit-New Large Sources

For the large HMIWI size subcategory, the SO 2 emissions estimate associated with the best controlled similar unit is 0.462 ppmvd. In our an alysis for the October 6, 2009 final rule, we

indicated that the SO 2 test run data for the best pe rformer were normally distributed. 2 Based on that conclusion, we estimated a 99 pe rcent upper limit of 1.59 ppmvd for SO 2 and published an

SO 2 emission limit of 1.6 ppmvd for new large HMIWI. 2 However, a closer examination of the

SO 2 emissions data for the best performer indicates that the data ar e actually lognormally distributed. (Note: In the em ission limit determinations conducted for the October 6, 2009 final rule, we erroneously referred to the 99 percent estimated values as “upper confidence limits” or “UCLs.” In this memorandum, we are usi ng the more accurate term “upper limits.”)

Where there are a sufficient number of datapoints for the best performer, we have used the

skewness of the data to determin e the distribution of the data. 2 Because normal distributions typically have a skewness of zero, we have concluded that those data sets with a skewness less than 0.5 are normally distributed, while those with a skewness of 0.5 or gr eater are lognormally

distributed. Closer examination of the SO 2 emissions data for the best performer shows the skewness of the data to be 0.54, which indicates the data are actually lognormally distributed. The skewness of the data was calculated by applying the Microsoft Excel SKEW function to the SO 2 test run data for the best perfor mer. (See Appendix A at the end of this memorandum for the test run data.)

We calculated the 99 percent upper limit for SO 2 using the following Microsoft Excel equation, based on a lognormal distribution of the SO 2 test run data for the best performer:

Lognormal distribution: 99% upper limit = EXP{[AVERA GE(Natural Log Values of Test Runs for Best Performer)] + [STDEV(Natural Log Valu es of Test Runs for Best Performer) x TINV (2 x probability, n -1 degrees of freedom)]}, for a one-tailed t-value (with 2 x probability), probability of 0.01, and sample size of

18

Using this equation, we estimated the 99 percent upper limit for SO 2 for new large HMIWI to be 8.04 ppmvd. (See Table 1 below.) As with the other emission limits, we determined the SO 2 emission limit by rounding up the upper limit to tw o significant figures, in accordance with standard engineering practices. We estimate the SO 2 NSPS emission limit should be 8.1 ppmvd, if our standard-setting process is to be correctly followed. EPA is proposing to amend the HMIWI

NSPS to include the correct SO 2 limit of 8.1 ppmvd for new large HMIWI, which reflects EPA’s intent in the October 6, 2009 final rule.

23 Table 1. Summary of SO 2 MACT Floor Results for New Large HMIWI

Parameters SO 2 , ppmvd

No. of sources = 1 Top performer = 0.462

Skewness = 0.54

Kurtosis = -1.57

Distribution = Lognormal

No. of test runs = 18 99% upper limit of top performer (test runs) = 8.04 Limit (based on 99 % upper limit) = 8.1

III. References

1. E-mail from Lindsey W. Kroos, ALL4 Inc., to Ketan Patel, EPA. October 27, 2009. “Question Around Final HMIWI NSPS Emission Limit.”

2. Memorandum from Thomas Holloway, RTI, to Katen Patel, EPA. July 2, 2009. Revised MACT Floors, Data Variability Analysis, and Emission Limits for Existing and New HMIWI.Appendix A New Sources / Current Large Subcategory

MACT Floor Unit and Test RunsTable A-1. SO2MACT Floor Unit – New Sources / Current Large SubcategoryFACIDUNITIDFacility nameUnit no.CityStateabbrCategoryAPCDcodeSO2,ppmvd120120--2Waste Management Resource Recoveryand Recycling CenterUnit 2AnahuacTXLDIFF0.462Note: L = Large HMIWI; DIFF = Dry sorbent injection/fabric filter.Table A-2. SO2MACT Floor Test Runs – NewSources / Current Large SubcategoryFACIDUNITIDFacility nameUnitno.CityStateabbrCategoryAPCDcodeSO2test dateParam-eterSO2,ppmvdln(SO2)120120--2Waste Management ResourceRecovery andRecycling CenterUnit2AnahuacTXLDIFF9/20/02Run 10.896-0.11024Run 20.886-0.1205Run 30.933-0.0694710/15/02-10/16/02Run 10.952-0.04913Run 20.943-0.05868Run 31.020.02181911/10/04Run10.2-1.60944Run 20.2-1.60944Run 30.2-1.6094412/5/05-12/8/05Run 10.2-1.60944Run 20.2-1.60944Run 30.2-1.6094412/4/06-12/9/06Run 20.02-3.91202Run 31.260.231112Run 40.02-3.9120212/3/07-12/5/07Run 10.06-2.81341Run 20.06-2.81341Run 30.06-2.81341Notes: L = Large HMIWI; DIFF = Dry sorbent injection/fabric filter.