1

**Date:** February

7, 2013 **Subject:** Technical Approach for Wool Fiberglass MACT Floor Calculations

40 CFR 63, Subpart NNN

– Supplemental Proposal EPA Contract No. EP - D - 11 - 084 ; EPA Work Assignment No. 1 - 0 7 RTIProject No. 021 3199 .00 1 .00 7 **From:** Cindy

Hancy Dave Reeves **To:** Susan Fairchild, EPA/OAQPS/SPPD/MMG **Introduction** Section 112 of the Clean Air Act (CAA) requires that the U.S. Environmental Protection Agency (EPA) establish National Emission Standards for Hazardous Air Pollutants **(** NESHAP ) for the control of the hazardous air pollutants (HAP) emitted from both new and existing major sources in a source category . The se standards must reflect the maximum degree of reduction in HAP emissions that is achievable. Th e minimum level of co ntrol is referred to as the “Maximum Achievable Control T echnology (MACT) floor . ” The method for determining the MACT floor for a NESHAP is defined for both new and existing sources in CAA section 112(d)(3). For new sources, the MACT floor cannot be less stringent than the emission control that is achieved in practice b y the best - controlled simil ar source. F or existing sources , the MACT floor cannot be less stringent than the average emission limitation achieved by the best - performing 12 percent of existing sources for source categories with 30 or more s ources, or the best - performing five sources for source categories with fewer than 30 sources. The purpose of this memoran dum is to present the data, methodology , and results of the MACT floor anal ys is for the Wool Fiberglass Manufacturing NESHAP , 40 CFR 63, Subpart NNN source category . This analy sis is part of EPA's obligation under CAA section 112 ( f)(2 ) and 112(d)(6) to conduct a residual risk and technology review. The MACT floor anal ys is is also being performed in response to a petition for rulemaking by the Natural Resources Defense Council and Sierra Club that states EPA failed to set emission limits for HAPs (phenol and methanol) emitted by wool fiberglass facilities and challenges some HAP surrogacies used in the current wool fiberglass NESHAP . This MACT floor anal ys is uses data collected from a nationwide voluntary survey of wool fiberglass manufacturer s conducted by EPA in 2010 and an Information Collection Req uest (I CR) sent out to the wool fiberglass industry in November 2011 . Data on process o perati ons, emission controls, and air emissions data reported b y respondents to the survey

and IC R were compiled into a Microsoft Access data base that serves as the data set used for this MACT floor analy sis (referred to in this memorandum as the “I CR data set”). On November 25, 2011 EPA proposed revisions to the Wool Fiberglass Manufacturing NESHAP, 40 CFR part 63, subpart NNN . This memorandum incorporates changes made since the November 2011 proposal to reflect public comments regarding facility information and emissions data.2

**Background Information** The current Wool Fiberglass Production NESHAP (s ubpart NNN) was promulgated on June 14, 1999 and applies to each of the following existing and newly constructed major sources located at a wool fiberglass manufacturing facility : glass - melting furnaces, rotary spin (RS) manufacturing lines that produce bo nded building insulation, and flame attenuation (FA) manufacturing lines producing bonded pipe insulation. The current rule also applies to new FA manufacturing lines producing bonded heavydensity and pipe products . Currently , s ubpart NNN defines “bonded” as wool fiberglass to which a phenol - formaldeh yd e binder has been applied . The use of these typ es of HAP binders result s in formaldeh yde, phenol, and methanol emissions from sources at bonded RS and FA lines which generally consist of forming, curing, and collection operations. RS and FA manufacturing lines that produce nonbonded products are not currentl y subject to the standards . The 1999 Wool Fiberglass Production NESHAP (subpart NNN) sets particulate matter (PM) emission limits for new and existing furnaces and sets formaldehyde limits for new and existing RS lines and for new FA manufacturing lines . The original NESHAP also uses the surrogate approach, where PM serves as a surrogate for HAP metals and formaldeh yde serves as a surrogate for organic HAP. The wool fiberglass manufacturing source category currentl y co nsists of 30 facilities operating in the United States ; 10 of these facilities are major sources and operate 29 glass - melting furnaces. The remaining 20 facilities are listed as area sources or sy nthetic minors . The North American Insulation Manufacturers Association (NAIMA) announced that by the end of 2012, they

predict no major sources subject to Subpart NNN 1 will exist in this source category (see docket items 0040 and 0052) by phasing out the use of phenol - formaldehyde binders . Once a facility has phased out its use of these HAP binders on bonded lines, it may

apply to the appropriate permitting authority to no longer be subject to the MACT Subpart NNN standard under two definitions of the MACT rule: the applicability definition and the definition of ‘bonded’ . The specific chemicals, compounds, or groups of compounds designated as HAP are listed in CAA section 112(b). From this list, chromium compounds, hydrogen fluoride (HF) and hydrogen chloride (HCl) were identifie d as being emitted from furnaces; and formaldehyde, phenol, and methanol were identified as being emitted from bonded FA and RS lin es. Inthe November 2011 proposal , EPA set MACT floor limits for HF and HCl. The Agency received comments on the proposed HF and HCl emission limits and upon reexamination of our analy sis of the acid gas test data, we found that up to 80 percent of the HF and HCl test data in the floor were below detection limit ( BDL ) of the required test method . Based on this information , EPA has decided to set work practice standards for HF and HCl instead of MACT floor emission limits under section 1 12(h) of the CAA. The 2011 proposal also set emission limits for chromium compounds based on both s ection 112(d)(6) technology review and 112(f)(2) residual risk ample margin of safety . The Agency is not revising the chromium emission limit in the 2011 pro posal, but is correcting the basis for proposed limit being technology review (and not a calculated MACT floor). D etails regarding chromium compound emission l imits and particulate matter ( PM ) limits for glass - melting furnaces are discussed in the Section 112(d)(6) Technology Review for Wool Fiberglass NESHAP memorandum and in the Draft Risk Report for the Wool Fiberglass Manufacturing RTR available in the docket for this rulemaking (docket # EPA - HQ - OAR - 2010 - 1042). With regards to formaldehyde, phenol, and methanol at RS and FA bonded lines, EPA proposed to remove the surrogacy

relationship in the rule and establish limits for phenol and methanol and correct the formaldehyd e limit based on data submitted by the industry in their voluntary

information collection effort of 2010 . After the 2011 proposal , EPA received information from industry clarifying that the

1 Letters from A. Crane, NAIMA to C. Hancy, RTI (June 8. 2011) and S. Fairchild, U.S. EPA, (August 2, 2011).3

proposed limits for formaldehyde, phenol and methanol were based on a data set which included test data for lines that had phased out use of phenol/form aldeh yde binders and were therefore no longer subject to the rule. The Agency removed the erroneous data from the dataset and recalculated the MACT floor for RS lines based on the bonded lines at major sources and s ynthetic minor s ources . The limits in the supplemental proposal for RS lines differ from the proposed limits due to the removal of erroneous data from the data set used to calculate the MACT floor. **MACT Floor Analysis -**  **Subcategories** Under CAA section 112(d)(1), EPA has the discretion to “.. .distinguish among classes, types, and sizes of sources within a category or subcategory

in establishing.. .” standards. When separate subcategories are established, a MACT floor is determined separately for each subcategory . To determine whether the wool fiberglass manufacturing facilities warrant subcategorization for the MACT floor anal ys is, EPA reviewed unit and process design s , operating information , and air emissions data compiled in the ICR data set and other information collected b y the Agency for development of the NESHAP for this source category . The EPA also analyzed several subcategorization recommendations submitted by industry in their public comments on the proposed rule (76 FR 72770, November 25, 2011) . Based on this review, EPA concluded th at sufficient information exists to continue subcategorization of bonded lines into both FA and RS lines, but that beyond this level, there are no significant design or operational differences at wool fiberglass facilities that warrant further subcategoriz ation . Specifically , the original/current wool fiberglass NESHAP (subpart NNN) contains separate emission limits for FA manufacturing lines that produce heav y- density

wool fiberglass and FA manufacturing lines that produce p ipe product wool fiberglass . According to recent industry information, there is only one company

that runs FA lines at their facilities. These facilities provided test data in response to the voluntary survey that was to represent all FA lines. The EPA received data for three FA line s that were running heavy- density product and no data on FA lines that were running pipe products. In their May 5, 2010 letter to EPA (see Docket EPA - OAR - HQ - 2010 - 1042) , industry stated that the testing at pot & marble flame attenuated ( FA ) process units wa s representative of all products made on FA lines based on the following: “all re melt borosilicate glass marbles; all are pot & marble flame attenuation; and all are operated b y J ohns Manville . ” The letter also stated that Johns Manville is the only NAIM A member with a pot & marble melting process and the FA process is “a completely different process than rotary (spin) and was subcategorized in the original MACT standard.” We therefore concluded that the limits developed for FA lines were representative o f all products made on FA lines and that further subcategorization was no longer supportable under the standard. W e proposed only limits for FA lines without regard to further subcategorization, and all products made on a n FA line using phenol/formaldehyde binders would be subject to those limits. Although we received comment suggesting subcategorization of up to four subcategories on FA lines, we received no additional test data from industry to support further subcategorization beyond the general FA line subcategory . Consequently , we propose limits for FA lines such that all products made on an FA line using phenol/formaldehyde binders are subject to the proposed emission limits. **MACT Floor Analysis Methodology Existing Sources**  A MACT floor anal ys is was completed for formaldehyde, phenol, and methanol emissions from RS and FA lines. The majority of the data (e.g., production and equipment throughput rates) used to calculate the MACT floors was submitted as confidential business information (CBI) and therefore , the data and calculations are not publicly available (and not included in this memorandum) .4

The first step in the MACT floor anal ys is for each regulated source and HAP was to array all the data and rank each unit ( for which emissions data was provided) b y emission level (lowest to highest) for each pollutant . From this ranking, a MACT floor pool of sources was identified for determining the minimum control level allowed for the MACT floor, consistent with the criteria defined for new and existing sources b y CAA section 112(d)(3). For the new source MACT floors, the best - controlled source was identified for which there were individual source test run data in the I CR data set. For the existing source MACT floors, selection of the MACT floor poo l size (i.e., number of emission units to be included in the determination of the average emission limitation value ) was determined on an individual unit category basis as described below. Bonded RS Manufacturing Lines . There are less than 30 RS lines located at the 10 major sources; therefore the top 5 best performing RS lines for which emission test data was provided were used in calculating the MACT floor for formaldehyde, phenol, and methanol. For new sources, the best performing source was used to calculate the MACT floor for each pollutant. Bonded FA Manufacturing Lines . This category includes less than 30 sources and emission test data was submitted for three FA lin es. Therefore, all of these three FA lines were used to calculate formaldehyd e, phenol, and methanol limits for existing sources. For new sources, the best performing source was used to calculate the MACT floor for each pollutant. The next step in the MACT floor anal ys is was to account for data variability in the c alculations of the applicable MACT floor limits for the subcategories using the data’s 99% upper prediction limit (UPL). Specificall y, the MACT floor limi t was determined as the UPLcalculated with the Student’s t - test using the “TINV” function in Microsoft Excel software. The UPLapproach has also been used in other EPA rulemakings (e.g., NESHAP for Portland Cement, NSPS for Hospital/Medical/Infectious Waste In cinerators, NESHAP for Industrial, Commercial, Institutional Boilers and Process Heaters , and NESHAP for Electric Generating Units ) to account for variability in emissions data for a specified level of confidence. The level of confidence represents the level of protection afforded to facilities whose emissions are in line with the best performers. For example, a 99 % level of confidence means that a facility whose emissions are consistent with the best performers has one chance in 100 of exceeding the floor limit. A prediction interval for a single future observation (or an average of several test observations) is an interval that will, with a specified degree of confidence, contain the next (or the average of some other pre - specified number) of randomly selected observation (s) from a population. In other words, the upper prediction limit estimates what the upper bo und of future values will be, based upon present or past background samples taken . The UPLconsequentl y represents the value at which we can expect the mean of future observations for the HAP emissions to fall within a specified level of confidence, based upon the results of an independent sample from the same population . This method accounts for the point - to - point variability in the data . The form of the UPL equation differs somewhat depending upon the number of data points and data distribution to whi ch it is applied. Attachment A includes a flow diagram that summarizes the UPL approaches used. To th is end, the data sets were evaluated for each HAP to ascertain whether the data were normally

distributed, or fit another type of distribution ( e.g. , log n ormal distribution) . According to the Central Limit Theorem (Durrett, 1996), when a data set includes 15 or more sources , the UPL is based on the assumption that the data fit a normal distribution. The C entral Limit Theorem states that regardless of the shape of the original distribution, if the distribution has a finite mean ( μ) and variance ( σ2 ), the sampling distribution of the mean approaches a normal distribution with a mean of (μ) and a variance of σ2/N as N, the sample size, increases (Durrett, 1996) . The wool fiberglass data sets used to calculate MACT floors varied for each p ollutant . When the sample size is smaller than 15 and the distribution of the data is unknown, the Central L imit Theorem cannot be5

used to support the normality assumption . St atistical test of the kurtosis and skewness are then used to evaluate the normality

assumption. The skewness statistic (S) characterizes the degree of as ymmetry of a given data distribution. Normally distributed data have an S value of 0. An S valu e that is greater (less) than 0 indicates that the data are as ymmetrically distributed with a right (left) tail extending towards positive (negative) values. The standard error of the skewness statistic (SES) was also used in determining the normality of the data distribution . The kurtosis statistic (K) ch aracterizes the degree of peakedness or flatness of a given data distribution in comparison to a normal distribution. Normally distributed data have a K value of 0. A K value that is greater (less) tha n 0 indicates a relatively

peaked (flat) distribution. The standard error of the kurtosis statistic (SEK) was also used in determining the normality of the data distribution . For each data set to which the UPLwas applied (i.e. , the separate data sets for each HAP applicable to a source ), the S and K values were calculated using the reported test values . If both kurtosis and skewness tests indicate the data is normally distributed, the UPL was calculated using the UPL pooled variance Equation 1.

= + ( , ) × + Equation 1 where: = the average (mean) of the best performing existing sources ; t(p,df) = the t statistic for a confidence level p , and df degrees of freedom; s 2 = the pooled variance; n = the total number of test runs (all sources) used in the anal ys is; and m = the number of (future) compliance test runs [for run - by- run data , m=3]. Degrees of freedom calculated by :



### 1 1 

###         

# 

 N i i 

### n df Equation 1a Mean calculated b y: 

#  

  

###  N i n j ij i 

### x n X 1 1 

### 1 Equation 1b Pooled variance calculated by :



#   

 

### 

  n

i i 

### X x n s 1 2 2 

### 1 1 Equation 1c If the kurtosis or skewness tes ts indicate the data was not normally distributed, the data w ere log transformed . Once the log s of all the test runs w ere calculated , new kurtosis and skewness test s w ere performed on the log - transformed data. If both kurtosis and skewness tests indicate d the log - transformed data w ere normall y distributed, the UPLcan be calculated using the Equation 2 .6 

#          

         ) 1 ( 2 ˆ ˆ 1 4 2 ˆ ˆ 2 2 ˆ ˆ ˆ 2 99 . 2 ˆ ˆ 2 2 2 2 n n e m e me m Z e UPL          Equation 2 where: μ = the average of the best performing existing sources ;

99 . 

### Z = the z statistic for a lognormal distribution at 99 percent; 2 ˆ  = the variance; n = the total number of test runs (all sources) used in the anal ys is; and m = the number of (future) compliance test runs [for run - by- run data m=3]. Mean is calculated b y:

nx n i i 

## 

  1  Equation 2a Variance is calculated b y:



##   1 ˆ 1 2 2



  

## 

 n x x n i i  Equation 2b If the raw dat a and the log - transformed data were not normally distributed and n ≥ 13, the UPL was calculated using the UPL pooled variance with skewness adjustment in Equation 3. Note this adjustment cannot be used if the number of individual runs is less than 13.                   m n s t n s Skew X p df 1 1 6 2

, 2 Equation 3 where: = the average of the best performing existing sources ; t(p,df) = the t statistic for a confidence level p , and df degrees of freedom; s 2 = the pooled variance; n = the total number of test runs (all sources) used in the anal ys is; m = the number of (future) compliance test runs [for run - by- run data m=3]; and Skew = the skewness of the test runs used in the anal ys is. If the raw data and the log - transformed data were not normally distributed and n was less than 13 the UPL was calculated using the UPL pooled variance in Equation 1, but instead of using the Excel TINV formula to find the t stati sti c t(p,df) , a trial and error method was used to find the t stati sti c that gives a 99 percent confidence level by correcting the probability value s (p) using E quation 4 Corrected Probability

= P 0 (t) + Skewness x P λ3 (t)

– Kurtosis x P λ4 (t) + λ3 2 xP λ3 /2 (t) Equation 47

**Adjustment for Below Detection Level Emissions Data** Prior to calculating the UPL s, test runs that were below detection level (BDL) were identified. If a dataset contained any BDLvalues, the UPL was calculated using BDL values as reported in the test report. The calculated floor or emissions limit wa s then compared to three times the RDL values provided b y EPA . If the three ti mes the RDL w as less than the calculated floor or emissions limit (e.g., calculated from the UPL), we conclude that measurement variability was adequatel y addressed and the calculated floor or emissions limit would need no adjustment. I f, on the other hand , the value equal to three times the RDL were greater than the UPL , we concluded that the calculated floor or emissions limit does not account entirely for measurement variability and used the three times RDLvalue instead . The RDL for each pollutant was determined using data from tests of all the best performers for all of the final regulatory

subcategories (i.e., pooled test data). If no BDL values were included in the pollutant data set for a particular unit ty pe, these steps were not performed. **MA CT Floor Analysis Results**  The MACT floors for new and existing source s were calculated using the 99% UPLapproach described above and are summarized in Table 1 . When calculated MACT floor s for new sources are less stringent than the MACT floor calculated f or existing sources, the existing MACT floor calculated value was used for both new and existing sources. Table 1

– Summary

of MACT Floor Emission L imits **Data Distribution**  **Mean of Sources**

**U sed to Calculate**  **UPL (lb/ton) for**  **E xisting**  **S ources**  **MACT floor**

**limits for Existing**  **Sources (lb/ton)**  **MACT**

**floor limits for New**  **Sources (lb/ton)**  **RS Lines** Formaldehyd e Normal 0.15 0.22 0.087 Phenol Normal 0.15 0.31 0. 0 34 Methanol Normal 0.42 0.75 0.61 **FA Lines** Formaldehyd e Normal 3.53 5.55 3.32 Phenol Normal 0.51 1.36 0.46 Methanol Normal 0.30 0.50 0.50 **References:** Durrett, Richard (1996). Probability : Theory and Examples (Second edition). Bhaumik, D.K. and Gibbons, R.D. 2004. An Upper Prediction Limit for the Arithmetic Mean of a Lo gnormal Random Variable. Technometrics, 46(2):239 - 248. Johnson, Norman J., Modified t Tests and Confidence Intervals for As ymmetrical Populations. Journal of the American Statistical Association, Vol. 73, No. 363 (Sep., 1978), pp. 536 - 544.8 

## Attachment A9 Determine number of sources in MACT floor

Are there at least 15 sources in MACT floor?

Assume normal distribution
Calculate MACT floor using UPL Pooled Variance Equation 1 Test for normal distribution using kurtosis and skewness

Does sample have normal distribution ?

Calculate MACT floor using UPL pooled Variance with skewness adjustment Equation 3

Use UPL as MACT floor Are any data BDL or DLL ? Log transform data Test data for lognormal distribution using kurtosis and skewness

Does sample have lognormal distribution ?

Calculate MACT floor using UPL Lognormal Equation 2

Determine RDL
Compare UPL to 3 x RDL Use greater of UPL and 3 x RDL as MACT floor Yes No

Yes No

No Yes

Yes **MACT Floor Flow Chart**

Does the dataset contain 13 or more data points ( n ≥ 13 ) ? Calculate UPL by adjusting T statistic values using probability trial and error . No No Yes