Response to Comments on the 2009 

NODA on the Landfill Loadings 

Calculations for SolventContaminated Wipes

December, 2011

Office of Resource Conservation and Recovery

U.S. Environmental Protection Agency

Prepared with the support of 

SAIC

12100 Sunset Hills Road

Reston, VA 20190

EPA Contract No.: EP-W-05-060
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1. Introduction

In response to EPA’s 2009 Notice of Data Availability (NODA) regarding the conditional 

exclusion of wipes (74 FR 55163, October 27, 2009), EPA received comments regarding 

the approach and assumptions used in estimating the quantity of solvent that may be 

disposed in a landfill, known as landfill loading. The scope of these comments included 

both the disposable wipes and reusable wipes analysis. The document prepared for the 

2009 NODA that contains the principal landfill loading assumptions is “Landfill 

Loadings Calculations for Disposed Solvent-Contaminated Wipes and Laundry Sludge 

Managed in Municipal Landfills,” January 2008 (Docket No. EPA-HQ-RCRA-2003-

0004). This is referred to below as the ‘Landfill Loadings Report’ or ‘landfill loadings 

calculations’

The public comments identified below present comments related to this portion of the 

risk assessment. The relevant portions of the comments are presented verbatim; full 

comments are in the docket for the final rule. If appropriate, revisions to the landfill 

loading calculations and/or the report were made to address these public comments. An 

explanation is included as to how the revised analysis addresses each comment. The 

revised, final Landfill Loadings Report is in the docket for the final rule (Landfill 

Loadings Calculations For Solvent-Contaminated Wipes, January 2012).

The landfill loading calculations are used as inputs to the risk assessment in calculating 

risks to receptors. Comments relating to these other portions of the risk assessment, such 

as fate and transport assumptions, are not identified below, but may be found in the 

document entitled Response to Comments on the Solvent Contaminated Wipes 2009 Risk 

Analysis: Risk-Based Mass Loading Limits, which is in the docket for the final rule.

2. Comments Primarily Addressing Solvents Selected for Inclusion in the 

Analyses

• Comment (0447 – John Deere): We agree with the scope EPA is taking, eliminating 

ten of the 30 solvents listed in 40CFR 261.31 because they are banned or restricted 

from use. Deere has defined a list of restricted materials applicable to John Deere 

facilities worldwide. Eight of these solvents (Carbon tetrachloride, 1,1,1-

Trichloroethane, Trichlorofluoromethane, Dichlorodifluoromethane, 1,1,2-

Trichlorotrifluroethane, Nitrobenzene, 2-Nitropropane and Pyridine) have been 

banned by Deere from all products and facilities. Deere agrees that the other two 

solvents, Carbon disulfide and Ethyl ether, are currently restricted from use in solvent 

applications.

RESPONSE: The commenter’s information is consistent with that provided in 

Sections 1.2.1 and 1.2.2 of the Background Document. No change to the 

background document or calculation is made as a result of this comment.
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3. Comments Primarily Addressing Assumptions for Disposable Wipes 

• Comment (0458 – Graphic Arts Coalition, page 2-3): On page 21 of the 

aforementioned report, Section 2.3.6 states: “As identified in Section 2.3.4, 

approximately 30,000 generators are assumed to generate F001 to F005 solvent 

contaminated disposable wipes; these generators are assumed to dispose their spent 

wipes as nonhazardous waste.”

The assumption that all 30,000 generators are disposing of their solvent contaminated

wipers that have been used in conjunction with a F001-F005 solvent is not accurate as 

very few facilities in the printing industry use F listed solvents for cleaning. In 

addition, current state policies do not allow generators to dispose of shop towels 

contaminated with a listed waste into a municipal landfill. The intent of the proposal 

issued by the Agency in 2003 is to establish those parameters that would allow 

facilities to safely dispose of their solvent contaminated wipers into a municipal 

landfill.

RESPONSE: The derivation of the estimate that there will be 30,000 generators 

of F001-F005 solvent-contaminated disposable wipes is provided in Section 2.3.4 

of the report, as identified by the commenter. The calculation incorporates an 

estimate of the percent of generators using F001-F005 solvents. The commenter’s 

information that ‘very few’ printing facilities use F001 to F005 solvents is 

difficult to incorporate into a quantitative estimate. EPA believes that the 

approach used in the report is appropriate, absent any data to the contrary.

The commenter correctly notes that the report assumes that all generators will 

dispose their contaminated wipes as nonhazardous waste (e.g., by municipal solid 

waste landfill), whereas under current regulation and state policies this 

assumption is not valid. The report makes the assumption to evaluate the impact if 

the policies were to change and the wipes were disposed as nonhazardous waste.

No change to the background document or calculation is made as a result of this 

comment.

• Comment (0458 – Graphic Arts Coalition, page 3): Further, the Agency does not 

recognize in its data analysis on landfill loadings that many printing facilities have 

migrated to the use of cleaning solvents that do not contain constituents that would 

render their solvent contaminated wipes a nonhazardous waste since the products 

used do not contain any listed solvents nor do they exhibit a hazardous waste 

characteristic. The assumption made in the report is that all facilities are using RCRA 

solvents. This is no longer accurate and is not supported by the data points in the 

current docket. Even in 1998, printing facilities were migrating to solvent technology 

that resulted in the creation of non-hazardous waste. While the towels contaminated 

with the nonhazardous solvents would no longer be subject to regulation, the 

important point is that the total number of facilities that would be disposing of
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disposable towels with RCRA regulated solvents would be less than what is currently 

assumed.

RESPONSE: The commenter is not correct in its statement that EPA assumed 

that all facilities are using RCRA solvents. As identified in Section 2.3.4 of the 

report, not all facilities are assumed to use RCRA solvents. Further, of the 

facilities using RCRA solvents, the report in Section 2.3.3 assumes that a fraction 

of their wipes contain the RCRA solvents (i.e., they do not exclusively use RCRA 

solvents, but use a variety of hazardous and nonhazardous solvents). The data 

used in the report are based, in part, on data from the printing industry provided 

by the Specialty Graphic Imaging Association (the commenter states that the 

Graphic Arts Coalition includes the Specialty Graphic Imaging Association).

No change to the background document or calculation is made as a result of this 

comment.

• Comment (0459 – National Automobile Dealers Association, page 3): Again, vehicle 

maintenance wipes often are contaminated with other hazardous or nonhazardous 

materials.

RESPONSE: The commenter confirms part of the approach included in the 

Background Document, namely that wipes are used in the vehicle maintenance 

industries. This industry was included in the report (Section 2.3.1). No change to 

the background document or calculation is made as a result of this comment.

The portion of the comment stating that wipes include a variety of contaminants 

(which may be different than the 30 solvents in the F001-F005 listings) is not 

addressed in the Landfill Loadings report. If solvent-contaminated wipes exhibit a 

characteristic due to constituents other than one of the exempt F-listed solvents

(e.g., co-contaminant metals), the wipes are not eligible for the exclusion. Also, 

wipes contaminated with other listed wastes would not be eligible for the

exclusion. Regarding other possible contaminants, note that the F-code solvent 

listings are based on the risk presented by the specific solvents which are included 

in the listing descriptions. The language in the listings illustrates EPA’s concern 

with the solvent chemicals in defining the scope of the listings. Other potential 

constituents in the solvent wastes vary widely across industries, such that it would 

be exceedingly difficult, if not impossible, to categorize and evaluate these wastes 

if we considered all other constituents. Because of the wide variability in 

constituents that might arise in wastes from use of the solvents, EPA focused its 

evaluation on the solvent chemicals themselves. We believe that this is the most 

practical approach to evaluating solvent wipes.

• Comment (0464 attachment – INDA/SMART (Geosyntec), page 11): Fitted 

Distributions for Parameters with Limited Datasets Result in Highly OverConservative Mass Loading Levels and Therefore Overestimate Risk. For many 
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chemical loading parameters, robust datasets were lacking and a small number of 

empirical measurements were used to represent the populations of interest by fitting

the data to a population distribution (parameterization). EPA guidance suggests 

caution in fitting distributions to data, especially when selecting the type of model for 

the parameterization.1,2 Inputs parameters were assigned to a distribution with little

consideration as to the underlying mechanism that may give rise to those distributions

(e.g., lognormal or normal distributions). Selecting the incorrect distribution can have 

a large impact in the results, particularly when the results reflect upper bound 

estimates. For example, consider the difference between a uniform distribution within 

a fixed range and a parametric distribution with a finite probability of extreme values. 

Extreme solvent loading values may even violate the implicit assumption that solvent 

loading is meeting the requirement of the risk assessment scenario (no free liquids).

For example, the solvent loading rate per wipe for all industries except printing was

estimated by EPA to fit a Weibull distribution (Exhibit H-7 in the Landfill Loadings

Report). Given this distribution we would expect 1% of the wipes to contain 144 

grams of solvent (Figure 4). Over 10,000 simulations, multiple loading rate values 

exceeding 200 grams would be selected. Such unrealistic mass loading levels were 

included in the analysis. Risks calculated under the assumption of no free liquids 

were developed under loading conditions that likely overestimated the potential 

loading rates.3

[Figure 4. Assumed Loading Rate Per Wipe in the Non-Printing Industry.]

RESPONSE: The general approach used for selecting and using parameter 

distributions are included in Section 1.3 of the Background Document. In particular, 

when deciding the type of distribution for the calculations, a distribution with the 

highest-ranking fit was typically selected because, for most input parameters (such as 

the amount of solvent on the wipe), no mechanistic basis exists to assess which 

distribution assumption is most appropriate. The commenter states that the parameter 

distributions were made with little consideration of the underlying reason or 

mechanism for the distribution. This is not correct because in most cases no 

information was available for these underlying mechanisms; if information was 

available it would have been considered in selecting the distribution.

The commenter states that an ‘upper bound’ of the amount of solvent per wipe would 

be reasonable to ensure that the wipe would meet a no free liquids requirement. The 

commenter suggests that values in excess of 200 grams per wipe would be 

unreasonable.

 1 EPA (1999). “Report of the Workshop on Selecting Input Distributions for Probabilistic Assessments.” 

630/R-98/004. 2 Crystal Ball (Version 7) does not allow fitting data to distributions for less than 15 samples due to the 

high degree of uncertainty.

3 Conservatism in estimates of loading rates is evidenced by the fact that each chemical in the risk 

assessment was assumed to be loaded on the same group of wipes. Collectively the total solvent on the 

wipes is above the empirical observations and potentially above the solvent capacity of the wipes.
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In considering this comment, EPA noted that applying an ‘upper bound’ is consistent 

with EPA guidance.4 The following guidance from Appendix B of EPA’s ‘Risk 

Assessment Guidance for Superfund’ (RAGS) is applicable here:

o Truncation may be considered when using unbounded probability 

distributions (e.g., normal, lognormal, gamma, Weibull) to characterize 

variability.

o Identifying appropriate truncation limits that reflect “plausible bounds” for an 

exposure variable will often require judgment.

o Sensitivity analysis can be used to determine if truncation limits are an 

important source of parameter uncertainty in risk estimates.

The following change to the background document or calculation is made as a result 

of this comment. Setting an upper bound for the amount of solvent on a wipe is one 

possible approach to try to account for the ‘no free liquid’ requirement. However,

selecting a reasonable value for this upper bound presents some difficulties due to the 

limited data. The initial sensitivity analysis presented in the report (i.e., Section 2.4.2 

of the Landfill Loadings Report) suggests that the amount of solvent on the wipes is 

not a particularly sensitive input parameter, so modifications to this distribution are 

not expected to impact results. To further investigate the importance of this 

parameter, a ‘what if’ analysis was conducted for two chemicals by setting the upper 

bound as 100 g/wipe. This value was chosen as an upper bound because no 

observations were above this value. The results of this analysis are included in 

Section 2.4.3 of the revised report. The landfill loading results were slightly lower 

when this limitation was present, but the magnitude of the difference was less than 8

percent at the 90th percentile when compared to the original analysis. Therefore, we 

find that the slightly more conservative approach used in conducting the analysis is 

reasonable.

• Comment (0464 attachment – INDA/SMART, page 13-14): Chemicals Included in the 

Risk Assessment Were Sufficient to Address Risks. Chemicals included in the risk 

assessment were sufficient to address the risks associated with landfill co-disposal of 

wipes and laundry sludge. Several solvents were excluded from the analysis based on 

use data that indicates these are no longer widely used industrial solvents. Use of 

solvent such as benzene, trichloroethylene, and tetrachloroethylene are being phased 

out. In general, it is expected that organic solvent use will continue to decline as more 

environmentally friendly solvents are employed. The data selected to evaluate the 

types of solvent used and the proportion of those solvent in waste stream is generally 

at least five to ten years old5 and may not reflect more recent changes in industry 

practices and movement to reduced risk solvent use.

RESPONSE: It is possible that the assumptions regarding the use of chemicals and 

solvents may not reflect current use patterns due to some of the reasons cited by the 

commenter; this limitation was acknowledged in Section 2.4.4 of the Landfill 

 4 EPA, ‘Risk Assessment Guidance for Superfund. Volume III - Part A, Process for Conducting 

Probabilistic Risk Assessment.’ EPA 540-R-02-002. December 2001. 5 Landfill Loading Report – Appendix A and B. SAIC, October 2008.
6

Loadings Report. However, the commenter did not present any specific data on this 

question. Due to a lack of data to quantify how solvent use would change in the 

future, the Landfill Loadings Report did not include these effects. With specific 

regard to benzene, trichloroethylene, and tetrachloroethylene, the Landfill Loadings 

Report used data from the 2004 Toxics Release Inventory as a basis for assumptions 

regarding the maximum percentage of sites expected to use these chemicals in 

solvents for wipes; these maximum percentages were 2.1%, 1.8% and 0.9% for 

benzene, trichloroethylene, and tetrachloroethylene, respectively. These percentages 

already reflect a low proportion of facilities.

No change to the background document or calculation is made as a result of this 

comment.

4. Comments Primarily Addressing Assumptions for Reusable Wipes 

• Comment (0461 – TRSA, page 8): Printer Towels vs. Shop Towels. A portion of the 

old ELG data included the pounds of shop towels and the pounds of printer towels 

washed by individual laundries. This data showed that 1,332 laundries managed shop 

towels and 480 managed printer towels. EPA’s contractor did not identify the percent

of facilities that manage both printer and shop towels. Instead, EPA’s contractor 

assumed in the NODA: (i) that all laundries manage shop towels; (ii) that there is a 

36% probability that a laundry that manages shop towels also manages printer towels; 

and (iii) that laundries only process shop or printer towels and no other textile 

products.6 EPA’s contractor also indicates that trends over the past 10 years were not 

assessed with respect to how the data regarding the pounds of shop towels vs. printer 

towels washed by individual laundries has changed.

The assumptions here regarding the processing of shop towels and printer towels 

contributes to the substantial overestimation of the volume of solvent-containing 

laundry sludge going to landfills. Not all laundry facilities manage shop towels. (See

Section III below). Similarly, the assumption that 36% of laundry facilities manage 

shop towels and printer towels is also high. Id. Indeed, TRSA estimates that 

approximately 19% of industrial laundry facilities process printer towels and shop 

towels, which represents less than 10% of the laundry industry’s overall business. 

EPA’s contractor has ignored the significant volume of textile item such as uniforms, 

floor mats, linens, mop heads and other products that contain little, if any, solvents.

This incorrect assumption skews the overall laundry sludge risk assessment. The two 

most sensitive parameters in the model are quantities of shop towels washed and 

quantities of printer towels washed. TRSA agrees that significant uncertainty is 

created by the sensitivity of these parameters. Indeed, because the pounds of shop 

towels washed drives the gallons of washwater generated per pound, which in turn 

affects the mass loading of solvent in laundry sludge through the partitioning process, 

an overestimation on the front end (i.e., the quantities of shop towels and printer 

towels washed) will affect the mass-loading estimate – perhaps by orders of 

 6 The latter assumption is significantly misleading as shop and printer towels generally comprise only a 

small fraction (less than 10%) on most laundry’s product mix.
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magnitude. And, as noted herein, shop and printer towels are only a minor fraction of 

the product mix at most laundry facilities. This, too, overestimates mass loading 

calculations.

RESPONSE: The effluent limit guideline (ELG) data were used appropriately in the 

Landfill Loadings Report. The ELG data collection effort was substantial, as noted by 

the result that data were collected from over 1,000 laundries. The landfill loadings 

calculations were conducted in such a way as to isolate the effects of shop and printer 

towels from other textiles such as uniforms. Note that section 3.3.2 of the Landfill 

Loadings Report is in error where it states that the report assumed that all laundries 

manage shop towels. However, this is an error in the text, not in the calculation 

approach. Specifically, Section 3.3.1 of the report identified that of 190 laundries

from the ELG effort, 141 processed shop towels and 71 processed printer towels. For

the purpose of the calculation, the report ignores any laundry that does not manage 

either shop or printer towels, and ignores loadings from non-towel textiles such as 

uniforms which are also managed by laundries. This is done to isolate loadings from 

sludges attributed to shop and printer towels.

The assumption of 36% probability that a laundry that manages shop towels also 

manages printer towels is well documented in the report (Section 3.3.2). The 

percentage simply reflects the number of laundries washing printer towels as a 

proportion of those washing shop towels (480/ 1,332). The commenter’s proposed 

modification of this value to 19% is addressed in more detail in a later comment.

As a result of this comment, the Landfill Loadings Report is changed by clarifying 

Section 3.3.2 in regards to laundries managing shop or printer towels as well as other 

textiles.

• Comment (0461 – TRSA, page 9): Solvent Concentration in Washwater. EPA’s 

contractor estimated the quantity of wastewater generated, deriving an industry 

average of 2.8 gallons/pound of textile based on 2002 water use data gathered from 

the Laundry ESP program. Based on sampling data gathered by the Office of Water 

during the ELG process, EPA’s contractor also estimated concentrations of solvents 

in laundry washwater after washing both printer and shop towels.

The estimates of quantity of wastewater generated and the concentration of solvent in 

wastewater are high. The most recent Laundry ESP results indicate that the industry, 

on average, uses 1.6 gallons/pound of textile. See 2006 Laundry ESP Report attached 

hereto as Exhibit “A.”7 This represents a savings of 26 billion gallons of water from 

1997 averages (or the water usage of about 700,000 people per year). Most 

significantly, in performing its calculations, EPA’s contractors used data taken from 

processes only involving shop towels and printer towels. Shop and printer towels are 

only a portion of overall production of most facilities. The other textile items, 

uniforms, floor mats, etc., would not be expected to contain any of the regulated 

 7 These TRSA data are only four years old, as compared to the ELG data that are now more than fourteen 

years old.
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solvents. By focusing only on the wastewater from shop and printer towel washing, 

EPA has greatly over-estimated wastewater solvent concentration.

RESPONSE: The commenter provided a report entitled ‘Laundry Environmental 

Stewardship Program: Laundry ESP’ which supports its claim that 1.6 gallons of 

water are used per pound of textile. In addition, the commenter also provided survey 

data for the same parameter (addressed in more detail in a later comment). Both the 

ESP report and the commenter’s survey data are more recent than the value used in 

the original Landfill Loadings Report. Therefore, EPA has modified the final Landfill 

Loadings report and calculations by including the survey data, rather than the ESP 

report, due to its detail.

As noted in a previous comment, the landfill loadings calculations were conducted in 

such a way as to isolate the effects of shop and printer towels from other textiles such 

as uniforms. For this reason, the analysis uses washwater from shop and printer towel 

washing. Including additional textiles as suggested by the commenter would have two 

effects:

(1) the washwater concentration term used in the calculation would decrease 

because it would be ‘diluted’ with water from other textiles which are not being 

evaluated for this effort; this effect was noted by the commenter; 

(2) the total washwater volume used in the calculation would increase due to the 

additional textiles considered; this effect was not noted by the commenter.

While these effects may or may not cancel each other out, they would add a layer of 

complexity to the calculation. Therefore, EPA maintained the simpler approach of 

isolating the washwater volume and the washwater concentration in the landfill 

loadings calculations for the wastewater treatment sludge.

• Comment (0461 – TRSA, page 9): Sludge Partitioning. To estimate a total mass of 

washwater and solvent, EPA’s contractor estimated the pounds of printer towels and 

shop towels washed, and the quantity of washwater. EPA’s contractor then used a 

partitioning model to estimate the portion of chemical in the wastewater that will 

partition to air or sludge, or remain in the water. As EPA’s contractor recognize, this 

modeling approach was necessary because sludge samples were not collected. See

Landfill Loadings Background Document, at 37.

The assumptions for this model include: (i) a reduction in volatility due to surfactant; 

and (ii) consideration of both a pit and screen (55% of facilities) and a pit, screen, 

equalization, and dissolved air flotation (45% of facilities) wastewater management 

systems. The results are expressed as a fraction of chemical in coming washwater 

which partitions to sludge. 

This partitioning process, at bottom, is hypothetical and depends entirely on the 

previously estimated volume of solvent-contaminated washwater. As noted, EPA’s 

contractor has overestimated both the quantity of incoming washwater, and the 
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quantity of shop and printer towels being processed and the concentrations of solvents 

in laundry wastewaters. And therefore, overestimated the quantity of each solvent 

“partitioning” to the sludge. The result, ultimately, is a compounding of the errors in 

the estimations of solvent contained in laundry sludge, and an inaccurate risk 

assessment.

RESPONSE: Specific elements from this comment are addressed in detail in other 

comments:

o Overestimation of the quantity of incoming washwater: addressed above (i.e.,

EPA modified the amount of water used per pound of textile based on the 

commenter’s survey data).

o Overestimation of the quantity of shop and printer towels being processed:

addressed below regarding survey data provided by the commenter,

o Overestimating the concentrations of solvents in laundry wastewaters: 

addressed above (i.e., the existing methodology is intended to isolate effects 

from shop and printer towels).

• Comment (0461 – TRSA, page 13): Industry Data. In response to the NODA, TRSA 

conducted a survey of its membership seeking data representation of current 

conditions in the industry.8 This data is business sensitive and was compiled only for 

purposes of responding to this NODA. Data collected via the survey included the 

following data points for the years 2005-2009:

o The laundry location;

o The sludge disposal location;

o Whether sludge was sent to a lined or unlined landfill;

o The pounds/year of both shop towels and printer towels processed;

o The gallons of washwater used per pound of towel;

o Total sludge concentration in ppmw for PCE, TCE, Methylene Chloride, 

Benzene, and 1, 1, 2-trichloroethane9

o Sludge TCLP data in mg/l for the same solvents; and 

o Solvent concentration in mg/l from washwater before pre-treatment

Eleven TRSA member companies responded, providing data from 271 industrial 

laundry facilities and 569 location-years of data points. These 271 facilities represent 

almost 90% of all facilities engaged in processing shop towels or printer towels. 

Using these data, independent expert Dr. Ranajit Sahu performed both a deterministic 

calculation for the estimated loading of PCE from laundry sludge, replicating EPA’s 

deterministic method, including EPA’s assumptions, and a Monte Carlo analysis. For 

the unit conversion and the sludge partitioning values, Dr. Sahu used the same values 

 8 The background data used to run both the deterministic and Monte Carlo calculations are attached hereto 

as “TRSA Survey Data and Summary”, Exhibit “B” and “Crystal Ball Report Using TRSA Data”, Exhibit 

“C”.

9 Given EPA’s conclusion that PCE was the only solvent posing a potentially unacceptable risk for laundry 

sludge, the following analysis pertains only to PCE.
10

as EPA. For the other factors – pounds of shop towels washed at a site, shop towel 

water concentration, pounds of printer towels washed at a site, printer towel water 

concentration, probability that laundry manages printer towels in addition to shop 

towel, gallons of washwater used per pound of towel, and the number of 

laundries/landfill – Dr. Sahu used TRSA survey data. For the deterministic approach, 

TRSA’s calculations represent the average for each data point used. 

RESPONSE: We have made a case-by-case evaluation of the data collected and 

provided by the commenter. EPA’s use of the data is described below.

The pounds/year of both shop towels and printer towels processed. The commenter’s 

data includes approximately 568 data points for shop towels and approximately 119 

data points for printer towels. This data has advantages and drawbacks in comparison 

to the data used in the Landfill Loadings Report. A primary advantage is that it is 

more recent (2005 to 2009) than the 1990s data used in the Landfill Loadings Report.

It also appears to include more facilities (271 as identified by the commenter), versus 

approximately 141 used in the Landfill Loadings Report. A drawback to the 

commenter’s data is that it appears to include data for multiple years for a single 

facility, with no method to distinguish which data are from a single facility. Therefore 

it may bias the results towards those facilities providing multiple years of data over a 

facility providing a single year of data. Nevertheless, the advantages outweigh the 

disadvantages in this instance. Therefore, the landfill loadings calculations have been

modified by including the commenter’s data for the pounds/year of shop towels and 

printer towels processed. In addition, Section 3.3.1 of the Landfill Loadings Report is 

modified by describing the data used.

The gallons of washwater used per pound of towel. The commenter provided 147 data 

points for this parameter. Similar advantages and limitations apply to this parameter 

as with the pounds of shop and printer towels processed. In addition, the Landfill 

Loadings Report previously considered this value as a constant (Section 3.3.4). Based 

on the new data submitted, the landfill loading calculations are modified by including 

these data as a distribution (the empirical data were best-fit to a lognormal 

distribution). In addition, Section 3.3.4 of the Landfill Loadings Report is modified 

by describing the data used.

Solvent concentration in mg/l from washwater before pre-treatment. The commenter 

provided 29 data points for tetrachloroethylene in washwater. The advantage of this 

data is that it more recent than the 1990s ELG data. However there are significant 

drawbacks with the data:

• The ELG data used in the Landfill Loadings Report are representative of 

washwater generated from shop or printer towels when washed alone (Landfill 

Loadings Report Section 3.3.3). The commenter does not specify the source of 

the sampled washwater. Based on its comments and concerns above that the 

concentrations used in the Landfill Loadings Report are high because they are 

taken from a process washing only shop or printer towels, we assume that 
11

these concentrations reflect washwater generated from shop and printer towels 

plus other textiles. As described previously, the calculation in the Landfill 

Loadings Report attempts to isolate the effect from shop and printer towels. 

We prefer to use data representative of washwater generated from the washing 

of shop and printer towels only to estimate the loadings of treatment sludge 

derived from laundering solvent-contaminated wipes. Therefore, we did not 

incorporate the concentrations provided by the commenter in the final 

analysis.

• The ELG data used in the Landfill Loadings Report are based on six laundries 

washing shop towels and three laundries washing printer towels (Landfill 

Loadings Report Section 3.3.3). It is not clear from the commenter’s data 

whether the concentration data represents multiple years from a single site, in 

which case the number of sites represented by the commenter’s data may be 

significantly less than 29. Therefore, the number of sites represented by the 

ELG data set may be comparable to the number of sites represented by the 

commenter’s data.

• The commenter did not provide any details on how the washwater samples 

were obtained or analyzed, nor were any QA or QC information provided. 

Therefore, EPA decided not to use these data.

For these reasons, the tetrachloroethylene data provided by the commenter are not 

used in the Landfill Loadings Report.

Other Data Identified by the Commenter. The commenter identifies additional data 

elements as part of its survey:

o The laundry location;

o The sludge disposal location;

o Whether sludge was sent to a lined or unlined landfill;

o Total sludge concentration in ppmw for PCE, TCE, Methylene Chloride, 

Benzene, and 1, 1, 2-trichloroethane

o Sludge TCLP data in mg/l for the same solvents.

However, these results were not provided by the commenter and could not be 

evaluated.

• Comment (0461 – TRSA, page 14-15): Deterministic Analysis. The results of this 

deterministic calculation are reflected in the Table below. 

[Table - Calculations for Estimating Landfill Loading of PCE from Laundry Sludge]

Using EPA’s method, and substituting TRSA’s more recent and robust data as 

described above, TRSA contends that EPA has overestimated PCE loading into a 

landfill by a factor of 417, with TRSA estimating that the kg/year of PCE going to 

landfill to be 0.064 kg/yr not 26.74 kg/yr. Of course, reducing the ELLR by a factor 

of 417 negates any potential excess risk for laundry sludge that EPA has estimated, 
12

for both the lined or unlined landfill with one possible exception – the potential risk at 

the 90th percentile for PCE at an un unlined landfill using the combined wipes and 

sludge data (see Comparison Background Document at 6, Table 1, estimated risk ratio 

of 530 for PCE under the combined scenario).10 Most significantly, the potential risk 

ratio of 1.1 for PCE in a lined landfill under a combined wipes plus sludge scenario, 

is negated by TRSA’s data, and becomes even less of a risk in light of the fact that of 

the 1.1 ratio, only 0.2 is attributed to laundry sludge. Qualitatively then, given that 

EPA has overestimated by a factor of 417, it is reasonable to conclude that laundry 

sludge poses no excess risk for PCE or any other solvent, especially in a lined landfill 

disposal scenario. 

Other aspects of TRSA’s data further confirm that EPA has significantly 

overestimated the potential risk associated with laundry sludge. Overall, TRSA’s data 

indicates that fewer reusable towels (printer or shop towels) are being processed by 

industrial laundries in a given year than EPA has estimated (312,893 lb/yr shop 

towels versus EPA’s estimate of 465,000 lbs/yr). There is an even more dramatic 

decline in the use of printer towels. (EPA estimates of 429,000 lb/yr versus TRSA 

survey data showing 214,595 lb/yr). TRSA data regarding this variable were received 

from as far back as 2005, indicating that the industry reduction in printer towels 

processed is not due solely to the economic slowdown of the past 15 months. In 

addition, where EPA estimated a 36% probability that a given facility is washing both 

shop towels and printer towels, TRSA’s data – for which it received 569 data points –

indicates that there is an overlap, on average, for only 21% of responding facilities. 

For the concentration data, TRSA data are based upon 29 data points; EPA used only 

three data points. 

Regarding the volume of washwater, TRSA’s data confirms the general pattern seen 

throughout the industry (see Section II C.2 above) that facilities are increasingly 

using less water per pound of textile without impact to sludge content. TRSA’s 148 

data points show that on average laundries are using 2.05 gallons/pound of towel, as 

opposed to 2.28 gal/lb as used by EPA based upon 2002 data. 

Finally, and most importantly, the TRSA survey results indicated that the majority of 

facilities are using lined landfills. TRSA’s data are reflective of the general trend over 

the past 20 years away from unlined landfills. Further, on average, the TRSA data 

show that a given landfill accepts sludge from only one laundry facility and not 

multiple facilities. EPA’s contractor estimated that the number of laundries to a given 

landfill was 1.7, almost twice what TRSA’s data show. Regardless, the 

overestimation of PCE loading into either an unlined or lined landfill by a factor of 

417 based on a much more robust and current data set, alone eliminates the notion 

that any of the solvents pose any potential excess risk for laundry sludge.

 10 See above, Section II.C, for TRSA’s argument why it is incorrect to estimate risk using a combination of 

disposable wipes data and laundry sludge data.
13

RESPONSE: Most of the comments regarding various input parameters are 

discussed previously. These include the quantity of towels washed, washwater 

concentration, and washwater volume.

The fraction of facilities washing printer towels versus shop towels was calculated by 

the commenter as 21% (i.e., 119 data points for printer towels/568 data points for 

shop towels). The commenter’s data may not be a true reflection of facility count, 

because a single facility can be represented by multiple data points. To provide 

consistency with the other uses of the data provided by the commenter, however, the 

landfill loadings calculations are revised to include this percentage calculated by the 

commenter.

The number of laundries using a single landfill is also an input parameter. The 

commenter states, on average, that a given landfill accepts sludge from only one 

laundry facility and not multiple facilities. We disagree that this is a reasonable

average value because, at a minimum, a given landfill will accept sludge from a 

single laundry facility (i.e., this value can never be less than one). The supporting data 

used by the commenter to check this conclusion was not provided. Therefore the 

parameter value used in the Landfill Loadings Report is unchanged.

The results following incorporation of the above changes are included in Section 3.4 

of the revised Landfill Loadings Report.

The commenter’s claim that the survey shows that the “majority” of laundry facilities 

dispose of their sludge in lined landfill is not sufficient to demonstrate that there are 

no potential risks from disposal in unlined units. The term “majority” is vague, and 

the specific number using lined landfills or the underlying data were not presented. 

Nonetheless, we modeled both an unlined and composite-lined landfill scenario to 

assess the full range of potential risks. The Agency found that disposal of wipes in 

composite-lined landfills was a necessary condition for the exclusion to adequately 

protect human health and the environment.

• Comment (0461 – TRSA, page 15): Monte Carlo Analysis. After conducting the 

deterministic calculation, the same data sets used were also used to conduct a MonteCarlo analysis for PCE only, using Crystal-Ball, the same software used by EPA’s 

contractors. The Monte Carlo analysis using TRSA’s data confirms the conclusion 

reached in TRSA’s deterministic calculation.

As shown in the attached Crystal Ball report, 200,000 trials were run. Lognormal 

distributions were selected for each of the variables with the respective distributional 

parameters. In most cases, the lognormal distribution was the one selected by the 

program as the best fit. In a few cases, the lognormal was the second best fit, very 

close to the one selected by the program. However, from a conceptual standpoint, it is 

more likely that the data are lognormally distributed, which is why it was selected. 

The results did not materially change if the other distribution (for example, Weibull) 

was selected. In the report, cell K5 refers to pounds of shop towels; cell K6 refers to 
14

the PCE concentration in wash water; cell K7 refers to pounds of printer towels; and 

cell K10 refers to the gallons of wash water per pound of towel, of either kind. 

The Monte Carlo analysis shows the respective sludge loading results for PCE as 

follows: 0.019 kg/yr at the 50th percentile and 0.171 kg/yr at the 90th percentile. In 

comparison, the respective EPA-estimated values were 23 kg/yr at the 50th percentile 

and 170 kg/yr at the 90th percentile. EPA’s Monte Carlo analysis, therefore, overestimates the sludge loading to a landfill by a factor of 1202 at the 50th percentile and 

by a factor of 991 at the 90th percentile.

Given the results from TRSA’s more current and robust data, it is clear that PCEcontaining laundry sludge does not pose any potential excess risk.

RESPONSE: Results of the revised analysis are included in Section 3.4 of the 

revised Landfill Loadings Report. These results incorporate the previously discussed 

changes to the input parameters. The revised sludge results for 20 chemicals (i.e., not 

limited to perchloroethylene) are included. These 20 chemicals are the ‘F-listed 

solvents’ as described in Section 1.2 of the Landfill Loadings Report. As described 

previously in response to TRSA’s comments, we did not adopt all of the changes 

suggested by the commenter. Using the updated data on the pounds of towels 

processed per year and the resulting washwater used lowered the mass loadings 

calculated for sludges generated by the laundries by about 50%. These changes are 

presented in the final Landfill Loadings Report.