1 February 4, 2011

MEMORANDUM

TO: Docket No.: EPA-HQ-OAR-2004-0305

FROM: Sharon Nizich, Project Lead Risk and Technology Review - National Emission Standards for Hazardous Air Pollutants (NESHAP) for Primary Lead Smelting

SUBJECT: Developments in Practices, Processes, and Control Technologies

The purpose of this memorandum is to present the results of an analysis to identify developments in practices, processes, and c ontrol technologies for ha zardous air pollutants (HAP) emission sources for the Primary Lead Smelti ng source category. This analysis is part of EPA’s review efforts in accordance with se ction 112(d)(6) of the Clean Air Act (CAA).

1.0 BACKGROUND

1.1 Requirements of Section 112(d)(6) of the CAA

Section 112 of the CAA requires EPA to es tablish technology-based standards for sources of HAP. These technology-based standard s are often referred to as maximum achievable control technology, or MACT, standa rds. Section 112 also contains provisions requiring EPA to revisit these standards. Specificall y, paragraph 112(d)(6 ) section states:

(6) REVIEW AND REVISION. – The Admini strator shall review, and revise as necessary (taking into acc ount developments in practi ces, processes, and control technologies), emission standards promul gated under this section no less often than every 8 years.

1.2 Description of Primary Lead Sm elting Source Category and NESHAP Requirements

The Primary Lead Smelting source category incl udes all facilities th at smelt lead-bearing ore concentrates to produce lead metal using pyrometallugical te chniques. The source category does not include secondary lead smel ters, lead remelters, or lead refi ners that are not located at a primary lead smelting facility. Lead is used to make various constructio n and consumer products such as batteries, paint, glass, piping, and filler. Lead sulfide (PbS) ore co ncentrates are the main feed material to primary lead smelters. The primary lead smelting process consists of PbS concentrate storage and handling, sintering of ore concentrates , sinter crushing and handling, smelting of sinter to lead metal, drossing (i.e ., removing the solid oxide deposits), refining and alloying of lead metal, and smelting of the drosses.2 HAP is emitted from primary lead smelting as process emissions, process fugitive emissions, and fugitive dust emissions. Process emissions are associated with the exhaust gases from sinter machines and blast and dross furn aces. HAP expected in process emissions are metals (mostly lead, but also some arsenic, ca dmium, and other metals) and also may include organic compounds that result from incomplete combustion of coke and natural gas combustion. Process fugitive emissions occur at various poin ts during the smelting process (such as during charging and tapping of furnaces) and generally include metal HAP. Fugitive dust emissions result from the entrainment of dust due to mate rial handling, vehicle traf fic, and wind erosion from storage piles. All fugitive dust emissions contain metal HAP. The majority of these fugitive emissions are related to concentrate handli ng, sinter transfer, and si ntering operations.

The NESHAP for Primary Lead Smelting were promulgated on June 4, 1999 (64 FR 30194) and codified at 40 CFR part 63, subpa rt TTT. The Primary Lead Smelting MACT standard applies to affected sources of HAP at pr imary lead smelters. Primary lead smelters are defined as “...any facility engaged in the pr oduction of lead metal from lead sulfide ore concentrates through the use of pyrometallurgical techniques.” At the time of promulgation of the Primary Lead Smelting MACT rule, there were three operating lead sme lters. Today there is one operating facility, The Doe Run Resources Corporation (Doe Run) in Herculaneum, Missouri, that is subject to the MACT standard.

The Primary Lead Smelting MACT standard applies to sinter machines, blast furnaces, dross furnaces, process fugitive sources, and fugitive dust sources. Process and process fugitive emissions of lead compounds from sinter machines, blast furnaces, and dross furnaces are limited to 500 grams (g) of lead emissions per me ga gram (Mg) of lead produced (i.e., 500 g/Mg of lead produced, or 1.0 lb/ton of lead produced). Process fugitive sources that are subject to the MACT standard are dross furnace charging, blast furnace and dross furnace tapping, and the sinter machine (charging, discharge end, crushing , and sizing). Process fugitive emissions must be captured by a hood and ventilated to a baghouse or equivalent control de vice. In addition, the sinter machine area must be enclos ed in a building that is ventilated to a ba ghouse at a rate that maintains a positive in-draft through any doorway opening. The MACT standard also requires the use of bag leak detection systems for con tinuous monitoring of baghouses. For fugitive dust sources, the MACT standard requires that the ow ner or operator prepare and operate at all times according to a standard operating procedures (SOP ) manual that describes in detail the measures used to control fugitive dust emissions from pl ant roadways, material storage and handling areas, sinter machine areas, furnace areas, and refining and casting areas. The work practices outlined in the SOP manual developed for compliance with a state implementation pl an is considered to be compliant with the MACT standard with regard to fugitive emissions work practice controls.

Other metal HAP emitted from the primary lead smelting processes (arsenic, cadmium, cobalt and nickel) are covered by the MACT standard by the re gulation of lead, which is a surrogate for all other nonvolatile metal HAP. Lead is not a surrogate for mercury. However, mercury emissions are not a concern for this s ource category because the mercury content of the lead sulfide ore and other materi als that could introduce mercury into the process is below the detection limit. Organic HAP are emitted in very small quantities from the incomplete combustion of small amounts of coke in the bl ast furnace and natural gas combustion sources3 such as space heating and genera tors. Although they were consider ed in the development of the 1999 MACT rule, they were not regulated because they are emitted at a rate so low as to be unreliable to measure and infeasible to re duce. A more detailed discussion of EPA’s consideration of VOC and organic HAP emissions in this review is presented in Attachment 1. Acid gas HAP were not identified and, therefore, were not regulated in th e original MACT rule. More recent emissions data indicate that acid gas HAP are not emitted by the lead smelting
process.

2.0 DEVELOPMENTS IN PRACTICES, PROCESSES, AND CONTROL TECHNOLOGIES

For the purposes of this technology review, a “development” was considered to be any of the following:

 Add-on control technology or other e quipment that was not identified and considered during the development of the NESHAP for the source category;

 Improvement in add-on control technology or other equipment that was identified and considered during NESHAP developm ent for the source category that could result in significant additi onal HAP emissions reductions;

 Work practice or operational procedure th at was not identifie d and considered during NESHAP development for the source category; and

 Process change or pollution prevention alte rnative that could be broadly applied that was not identified and considered during the development of the NESHAP for the source category.

To identify developments in practices, pr ocesses, and control technologies, we conducted searches of EPA’s RACT/BACT/LA ER clearinghouse and the internet for information on primary lead smelting. We also reviewed the state permit, state implementation plan (SIP) and the informa tion collection request (ICR) response from the one remaining primary lead smelting facility. The search results are summarized below.

At the time of the MACT rule promulga tion, HAP emissions from the primary lead smelting source category were primarily lead but also included small amounts of arsenic, cadmium, cobalt, and nickel, and low levels of combustion related organics. Emissions data from a 2010 ICR response from the onl y remaining primary lead smelter (1) confirmed that, with the exception of the leve l of emissions, the emissions profile for the facility has not changed, with lead accounting for about 99 pe rcent of the HAP emissions. Therefore, this technology review focused on developments in prac tices, processes, and control technologies applicable to lead emission sources.

2.1 Clearinghouse and Internet Searches

RACT/BACT/LAER Clearinghouse The terms “RACT”, “BACT”, and “LAER” are acronyms for different program requirements under EPA’s New Source Revi ew (NSR) program. Under EPA’s New4 Source Review (NSR) program, if a company is planning to build a new plant or modify an existing plant such that air pollution emi ssions will increase, the company must obtain an NSR permit. The NSR permit is a construction permit which requires the company to minimize air pollution emissions by changing th e process to prevent air pollution and/or installing air pollution control equipment. RACT, or Reasonabl e Available Control Technology, is required on sour ces in areas that are not meeting national ambient air quality standards (i.e. non-attainment ar eas). BACT, or Best Available Control Technology, is required on major new or modified sources in attainment areas. LAER, or Lowest Achievable Emission Rate, is required on major new or modified sources in nonattainment areas. BACT and LAER (and sometimes RACT) are determined on a caseby-case basis, usually by State or local permitting agencies. EPA established the RACT/BACT/LAER Clearinghouse, or RBLC, to provided a central database of air pollution technology information (including pa st BACT and LAER decisions contained in NSR permits) to promote the sharing of information among permitting agencies and to aid in future case-by-case determinations. Ho wever, data in the RBLC are not limited to sources subject to RACT, BACT, and LAER requirements. Noteworthy prevention and control technology decisions and information are included even if they are not related to past RACT, BACT, or LAER decisions.

The RBLC contains over 5,000 air pollution control permit determinations that can help indentify appropriate technologies to mitigate most air pollutant emission streams. It was designed to help permit applicants and reviewers to make pollution prevention and control technology decisions fo r stationary air pollution sources, and includes data submitted by several U.S. territo ries and all 50 States on over 200 different air pollutants and 1,000 i ndustrial processes.

The RBLC was searched for facilities that conduct primary lead smelting as well as for facilities in other nonferrous ma nufacturing industries. No facilities were identified during the search and no new contro l technologies or developments in existing control technologies were id entified to further reduce em issions from primary lead smelting facilities.

Internet Search A general search of the internet was conducted for information on new processes and control technologies for primary lead smelting. The search identified one new technology, a hydrometallurgical process, whic h could potentially be used in lieu of pyrometallurgical smelting to produce lead metal from lead sulfide ore. The hydrometallurgical lead processing t echnology is under development and uses electrolysis and electrowinni ng to produce lead from lead ore. This technology, however, is currently only in demonstration project status and not commercially available. Therefore, it is not a proven technology and currently cannot be considered a replacement technology for primary lead smelting operations.

2.2 State SIP and ICR5 Based on our review of The Doe Run Herculaneum Title V permit, the Missouri SIP for lead, and information provided in the Secti on 114 ICR response from The Doe Run Company, we have determined that there have been adva nces in emission contro l measures since the 1999 Primary Lead Smelting MACT standard. The fo llowing paragraphs discu ss these advances and improvements.

The 1999 MACT lead emission limit for primary lead smelting was set at 1 lb/ton. The limit is a facility-wide emission limit that applie s to the aggregation of emissions discharged from the air pollution control devices used to control emissions from the following sources:

 Sinter machine;

 Blast furnace;

 Dross furnace;

 Dross furnace charging location;

 Blast furnace and dross furnace tapping location;

 Sinter machine charging location;

 Sinter machine discharge end;

 Sinter crushing and si zing equipment; and

 Sinter machine area.

A facility-wide limit format was used b ecause it was consistent with SIPs, the commingling of exhaust gases from processes to a single stack made it impossible to set limits for individual sources, it gave the facilities more flexibility in complying with the standard, and it promoted pollution prevention by giving each fac ility the ability to meet the emission limit through any combination of source re duction and control technology options.

The 1999 MACT lead limit was set using the lead emission limits from the lead SIPs for the states in which primary lead smelting sources were operational at the time of the rulemaking. EPA took each of the three lead SIP limits, in lb/day, divided them by the corresponding lead production capacity, in tons/day, and calculated a l ead emission rate in lb/ton. The results were as follows:

ASARCO - Missouri 1.0 lb/ton ASARCO - Montana 1.0 lb/ton Doe Run - Missouri 0.84 lb/ton

The values were ranked and the median value (1.0 lb/ton) was selected as representative of the MACT floor.

Since the MACT standard was promulga ted, the industry has undergone significant changes. Two of the three facilities have s hut down. As discussed above, the only remaining primary lead smelting facility is the Doe Run sm elter at Herculaneum, Missouri. Because the Doe Run facility is located in an area desi gnated as non-attainment for the lead National Ambient Air Quality Standard (NAAQS), the facility is subject to control requirements under the Missouri SIP for lead. In an effort to meet th e lead NAAQS, Missouri revised the lead SIP as it applied to the Doe Run facil ity in 2000, 2002 and 2007, requiring numerous emissions reducing6 measures and improvements to add-on control devices, processes, and work practices. SIP requirements are also incorporated into Doe Run’s Title V permit.

The SIP requirements, implemented after the 1999 MACT standard, were considered in our technology review. The SIP requirements, summa rized below, are descri bed in detail in the 2007 revision of SIP prepared by the Missouri DNR (available at http://www.dnr.mo.gov/ENV/apcp/docs/2007revision.pdf). The SIP addresses process, process fugitives, and fugitive lead emissions and requires enhancements of existing emission control technology, adding or upgrading enclosures, pr ocess changes and limitations, and work practices.

Under the SIP, fugitive dust emissions are controlled by comprehensive work practices including road watering and auto matic sprinklers, using regenera tive sweepers to remove dust from paved surfaces to reduce emissions from tr affic, maintaining a minimum water content for ore concentrate and for baghouse dust that is loaded into railcars , and inspecting the siding that encloses buildings (followed by prompt repairs if needed).

Our review found that the practices impleme nted under the SIP to control fugitive dust emissions have resulted in reductions in these emi ssions. As a result of the SIP requirements, we find that all feasible practices and controls availa ble for control of fugitive dust emissions in this industry have already been implemented. Ther efore, EPA did not find further applicable practices or controls that should be required under the MACT to reduce fugitive emissions.
Baghouses are the most common control devi ces used to control process and process fugitive emissions of lead compounds at the He rculaneum facility with the exception of the process emissions from the sinter machine, whic h are controlled by a combination of devices in series: electrostatic precipitator, baghouse, and acid plant (for control of sulfur dioxide). The buildings that house the blast furnaces, dross furn aces, and refinery kettles are also exhausted to a baghouse. Improvements to existing emission controls required by the SIP include the installation of pleated filters to lower the air-to-cloth ratio fo r baghouses, increased ventilation and improved ventilation hoods at the blast fu rnace, and using reverse flow technology for baghouse cleaning. SIP-required measures also included the installation of enclosures for unloading ore concentrate, sinter storage, and the sides of the sinter machine (which are evacuated to a baghouse).

Process changes implemented in response to the SIP to reduce emissions include a process control system for the injection of ai r through the blast furnace tuyeres located at the bottom of the blast furnace, limitations on indi vidual process and overall plant throughputs, and limiting specific operations to only certain time s of the day when the impact on ambient air concentrations is less. Emissions from malfunc tions will be reduced by alarms that sound when the baghouse fan malfunctions, an interlock system to restrict air flow into the blast furnace when the baghouse is not operating properly, and cameras for the dr oss and refinery kettles to detect kettle failure (i.e., when a plume of smoke is detected fr om the stack, the kettle burner can be immediately shut off and the problem corrected).

Under the SIP, technological improvements have also been made to the refining operations at the Doe Run facility. Under the current MACT, refining operations are not subject7 to the lead emission limit because at the time the MACT standards were developed, emissions from refining were considered fugitive in nature . In response to the SIP requirements, the Doe Run facility has enclosed the refining and casti ng operations and now exhausts the emission from the refining kettles as well as the refining building to baghouses.

Recent stack tests show that these improvement s have resulted in emissions substantially lower than are allowed under the current MACT rule. To assess the impacts of the technological improvements, lead emissions data from 2008 were compared with emissions data from 2000. Data from 2008 was selected because it reflect s the many technological improvements that have been implemented at the facility since the MACT rule promulgation. Emissions data from earlier years would not account for all of the emission reducing changes that have been implemented at the Doe Run facility given that some of the improvements were not implemented until 2007 and 2008. In 2008, lead emissions from the smelter operations sintering, blast furnace and drossing (i.e. from the main stack) were 13.31 TPY and emissions from the baghouse controlling emissions from the blast furnace and dross plant building (i.e., baghouse 7) were 1.81 TPY for a total of approximately 15.1 TPY. At the 2008 lead production rate of 149,500 tons, the emission rate at Doe Run was about 0.2 lb/ton, an 80 per cent reduction from the current MACT limit of 1 lb/ton.

The 2008 emissions of 13.31 TPY from sinterin g, blast furnace operations, and drossing operations, represent nearly 70 percent of total faci lity-wide lead emissions and reflect the annual rate of emissions achievable as a result of the technol ogical improvements that have been made since 1999. EPA believes that the level of emi ssions in 2008 support the lowering of the MACT limit to be consistent with the demonstrated level of performance.

In order to establish an emission limit that would properly reflect the facility performance, EPA used the actual 2008 annual em issions from the sintering, blast furnace and drossing operations (i.e. 13.31 TPY) and then a ccounted for variability using the 95 percent confidence upper predictive limit (UPL). The 95 percent confid ence UPL for the lead emissions is 14.8 tons. The use of the UPL to account for va riability in emissions and the emissions data used in the calculation is di scussed in Attachment 2.
To estimate the plant wide emission limit th at EPA is proposing, the technology-based emissions level for sintering, blast furnace a nd dross furnace operations (i.e., 14.8 TPY) was added to the other risk-based emission levels established for the other emission sources at the facility. The development of the plant wide emi ssion limit is described in the preamble to the proposed rule.

3.0 CONCLUSION

This review identified several developments in practices, controls or processes that have been implemented in the primary lead smelting source category since the 1999 MACT promulgation. The primary lead smelting sour ce category currently includes one operating facility compared to three at the time the MACT rule was promulgated. The one remaining facility, The Doe Run Resources Corporation, has implemented numerous work practices to control fugitive emissions and additional enclosures and improvements to add-on controls to address process and process fugitive emissions since the 1999 MACT. Additionally, refinery8 operation emissions, which were formerly fug itive, are now captured and exhausted through a baghouse.

The improvements identified in this revi ew were all requirements imposed on the Doe Run facility through the Mi ssouri Lead SIP in order to comp ly with the lead NAAQS. As a result, current emissions data indicate an appr oximate 80 percent plant wi de reduction in lead emissions since the MACT was promulgated. A lthough these lead emission reductions are not the result of the MACT requirements, EPA belie ves that the current demonstrated emission levels represent an achievable pe rformance and that a reduction in the standard is warranted to bring the standard in line w ith actual performance.

To determine the emissions level on which the new emission limit would be based, EPA used the 2008 emissions for the facility as report ed in the Section 114 ICR response for the main stack emission (which includes the sintering, blast furnace, and drossing operations), and considered variability based on recent stack te sts. EPA calculated that the new emission limit should be based on a 14.8 tons per year cont ribution from the sintering, blast furnace,and drossing operations (i.e. the main stack). This 14.8 tons per year should be included in the calculation of the facility-wide le ad emission limit taking into c onsideration any other necessary emission reductions resulting from the residu al risk analysis bei ng conducted under Section 112(f)(2) for the source category.

4.0 REFERENCES

1. Letter from Curran, D.Y., Stinson Morrison H ecker LLP to S. Nizich, US Environmental Protection Agency, Response from The Doe Run Resources Corporation to EPA’s December 4, 2009, Section 114 Information Collection Request, February 5, 2010.9 

## ATTACHMENT 1

VOC and Organic HAP Emissi ons from the Main Stack

During the original MACT development in 1997, VOC emissions testing was performed by the EPA on the uncontrolled blast furnace exhaus t at the Doe Run sme lter to determine the magnitude of organic HAP emissions from prim ary lead blast furnaces. The emissions data obtained indicated low (part per billion) levels of several or ganic HAP compounds. The five compounds with the highest measured emissi on rates were benzene (62 ppb, 0.29 lb/hr), methylene chloride (50 ppb, 0.26 lb/hr), acetalde hyde (60 ppb, 0.15 lb/hr), carbon disulfide (33 ppb, 0.15 lb/ hr), and formaldehyde (87 ppb, 0.15 lb/ hr). Combined, the measured organic HAP emissions totaled 2.3 lb/hr, which is equivalent to an annual emission rate approaching 10 tons per year. At the time of the original MACT de velopment, EPA believed these levels of organic HAP emissions were not significant enough to warra nt regulation and were far below what the EPA has historically considered achievable with add-on controls (e.g., thermal oxidizers). The EPA generally considers thermal oxidizers capable of achieving a 98 percent emission reduction or an outlet concentration of 20 ppm, whichever is greater. As stated above, organic HAP concentrations at primary lead smelters range from 33 to 87 ppb, or three orders of magnitude less than what the EPA has considered achievabl e with thermal oxidizers. Therefore, the EPA believes that it is technically infeasible to redu ce organic HAP emissions from primary lead blast furnaces through the use of add-on controls.

EPA evaluated 2008 VOC and the 2005 NEI orga nic HAP data to determine whether it was feasible to require reductions in organic HAP emissions. Data was analyzed from the Doe Run emission inventory (as supplied to the Stat e of Missouri) and the 2005 NEI. VOC data reported in Doe Run emission inventories lists total VOC emissions in 2008 of 2.21 TPY. Information on individual organic HAP emissions and total VOC from the 2005 NEI lists total VOC emissions of 2.56 TPY and organic HAP emi ssions of about 0.06 TPY, or about 2 percent of total VOC. Applying this pe rcentage to the 2008 total VOC emissions results in 2008 organic HAP emissions of approximately 0.04 TPY, far below the 10 TPY reported in the original MACT.

Using the 2005 NEI data for the Doe Run f acility, VOC emissions are approximately 43 times the level of organic HAP emissions. Applying this ratio to the concentrations reported in the original MACT of 33 to 87 ppb (or 0.033 to 0.087 ppm), we estimate total VOC concentrations to be between 1.4 ppm and 3.7 ppm at the Doe Run facility. These VOC concentration levels (1.4 to 3.7 ppm) are we ll below the 4 ppm detection limit of the measurement methods currently available fo r VOC. We believe it is technically and economically impracticable to m easure VOC’s at these levels.

Recent information on a thermal oxidizer used to control organic emissions from a cement kiln showed that the thermal oxidizer wa s capable of reducing VOC emissions to 4 ppmv (at 7 percent oxygen), a level that is at least thr ee orders of magnitude greater than the organic HAP concentrations measured at the Doe Run fa cility. At higher VOC concentrations, for example 15 ppmv and above, a thermal oxidizer will have a removal efficiency of about 9810 percent. At lower VOC concentr ations of about 3 ppmv, a therma l oxidizer’s removal efficiency is expected to be no better than 50 percent. The estimated VOC concentrations at the Doe Run facility are estimated to be 1.4 to 3.7 ppm, thus an even lower removal efficiency is likely. Additionally, the use of thermal oxidizers has various significant adverse environmental consequences, including increase in emissions of criteria polluta nts, and significa nt extra energy utilization, with attendant increases in carbon dioxide (CO2) gas emissions.

Based on these considerations, EPA has determ ined that the VOC emissions from this facility do not warrant consideration for re gulation under the section 112(d)(6) technology review.11 

## ATTACHMENT 2

Variability and Upper Predic tive Limit Calculation Main Stack Lead Emissions

In assessing sources’ performance, EPA may consider variability both in identifying which performers are “best” and in assessi ng their level of perf ormance. Brick MACT , 479 F. 3d at 881-82; see also Mossville Envt’l Action Now v. EPA

, 370 F.3d 1232, 1241–42 (D.C. Cir 2004) (EPA must exercise its judgment, based on an evaluation of the relevant factors and available data, to determine the level of emissi ons control that has been achieved by the best performing sources considering these sources’ operating variability).
Variability in lead producers’ performance has a number of causes. For emissions of lead compounds that are controlled by baghouses, the va riability is chiefly due to variations in performance of the control device for which both run-to-run and test-to-test variability must be accounted. 1

In determining a plant-wide emission limit, we used annual emissions discharged from the air pollution control devices used to control lead emissions from the Doe Run primary lead smelter. For this rule, we used the 2008 emissions reported by Doe Run to the State of Missouri. Variability was added only to the main stack emissions as the emission levels for the other sources had required risk-based emission levels.
We assessed variability using a statistical fo rmula designed to estimate an emissions level that is equivalent to the source’ s performance based on future compliance tests. Specifically, the calculated limit is an upper predic tion limit (UPL) calculated with the Student’s t-test using the TINV function in Microsoft Excel®. The Student’s t-test has also been used in other EPA rulemakings (e.g., NESHAP for Portla nd Cement Manufacturing; NSPS for Hospital/Medical/Infectious Waste Incinerators ; NESHAP for Industria l, Commercial, and Institutional Boilers and Process Heaters) in accounting for variab ility. A prediction interval for a future observation is an interv al that will, with a specified degree of confidence, contain the next (or some other pre-specified) randomly se lected observation from a population. In other words, the prediction interval estimates what the upper bound of future values will be, based upon present or past samples taken. The UPL cons equently represents the value which we can expect the mean of future obser vations (3-run average for lead) to fall below within a specified level of confidence, based upon the results of an independent sample fr om the same population. In other words, if we were to randomly select a future test condition from any of these sources (i.e., average of 3 runs or 30-day average) we ca n be 95 percent confident that the reported level will fall at or below the UPL value. Use of the UPL is appropriate in this rulemaking because it sets a limit any single or future source can meet based on the source’s past performance.

1 Run-to-run variability is essentially within-test variability, and encompasses variability in individual runs comprising the compliance test, and includes uncertainties in correlation of monitoring parameters and emissions, and imprecision of stack test methods and laboratory analysis. 72 FR at 54877 (Sept. 27, 2007). Test-to-test variability results from variability in pollution device contro l efficiencies over time (depending on many factors, including for fabric filters the point in the maintenance cy cle in which a fabric filter is tested). Test-to-test variability can be termed long-term variability. 72 FR at 54878.12 This formula uses a pooled variance (in the s 2 term) that encompasses all the data-point to data-point variability. Where variability was ca lculated using the UPL statistical approach, we used the sample standard devia tion calculated from the emissions da ta distributions for lead. The standard deviation is the common measure of the dispersion of the data set around an average. We note here that the methodol ogy accounts for both short-term a nd long-term variability and encompasses run-to-run and te st-to-test variability.
We adopted a form of the UPL equation that ha s been used in more recent rulemakings. See 75 FR 54970 (September 9, 2010), 75 FR 32020 (June 4, 2010) and 75 FR 31905 (June 4, 2010). The UPL used in this pr oposed rule is calculated by:

Where:

x  ̄ = 2008 annual emissions n = the number of test runs m = the number of test runs in the compliance average

s 2 = observed variance t = student t dist ribution statistic

This calculation was performed using the following Excel functions:

95 percent UPL = 2008 annual emissions + [ STDEV(Test Runs) x TINV(2 x probability, n-1 degrees of freedom)*SQRT((1/n)+(1/m))], for a one-tailed t-value, probability of 0.05, and sample size of n

Figure 1 presents the UPL calculation using the recent st ack test data for the main stack at the Doe Run Herculaneum facility. Figure 2 is a listing of stack test results used in the calculation of the UPL.13 Figure 1 - UPL Calculations fo r Main Stack Lead Emission

UPL Pooled Variance=
Runs 2001-2008
1 2.28
2 2.35
3 3.15
4 2.85
5 0.47
6 0.58
7 0.39
8 0.43
9 0.40

ni = number test runs = 9

Total Number of sources = 1

n =Total # test runs = 9

8

This step is for QC only:

means 1.4335

1.4335 13.31 Main Stack Pb emissions (tons/yr) ‐ 2008 EI
Mean =

Pooled Variance = 1.42101

m= number future runs = 3 Method 12 test quarterly (3 runs/test)

Term1 0.4444

Term2 0.6316

Squared root Term2 0.7947

t

‐ statistic = quantile t

‐ distribution with df degrees of freedom at .95 confidence level = 1.859548033

UPL POOLED VARIANCE = 14.78779913 Doe Run Main Stack Pb

Emissions, lb/hr

NOTE: the pvalue for the t-statistic is calculated as: 2*alpha, where 1-alpha is desired confidence, so if 99% confidence is de sired then alpha=0.01 and 2*alpha=2*(0.01) 

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n m        14 Figure 2 - Doe Run Herculaneum Stack Test Da ta from Section 114 ICR Response

Source Year of Test Run # Emissions Tests Results for Pb (lb/hr) Production during testing (tons Pb/hr) Emissions rate during testing (lb Pb/ton Pb produced)
Main Stack 2001 1 6.07
2 4.95
3 3.13
2002 1 20.24 8.88 2.28
2 20.87 8.88 2.35
3 27.99 8.88 3.15
2003 1 25.2 8.83 2.85
2 11.92 25.38 0.47
3 14.62 25.38 0.58
2004 1 6.85 17.50 0.39
2 7.46 17.50 0.43
3 6.99 17.50 0.40
2006 1 3.3
2 4
3 4
2008 1 10.81
2 17.49
3 19.23