# Response to Comments on the Solvent

Contaminated Wipes 2003 Risk Screening Analysis

December, 2011

Office of Resource Conservation and Recovery U.S. Environmental Protection Agency

Prepared with the support of RTI International EPA Contr act Number EP

- W

- 09

- 004 RTI Project Number 0212041.002.024Response to Comments on the Solvent Contaminated Wipes 2003 Risk Screening Analysis

ii 

### Table of Contents

1. Introduction

................................ ................................ ................................ ................................ ............ 1

2. Summary of Commen ts by Reviewers

................................ ................................ ................................ ... 1 2.1 Preferential Treatment of Laundered Wipes and Sludge

................................ ............................. 5 2.1.1 Applied Different Modeling Assumptions (comme nt theme 1)

................................ ... 5 2.1.2 Established “5 gram limit” (comment theme 2)

................................ ........................... 5 2.2 2003 Modeling Assumptions Overestimate Risk

................................ ................................ ........ 6 2.2.1 Overall Modeling Framework (comment theme 3)

................................ ...................... 7 2.2.2 Landfill Characteristics and Environmental Setting (comment theme 4)

.................... 7 2.2.3 Groundwater Leachate Concentration (comment theme 5)

................................ .......... 8 2.2.4 Distance to Receptors (comment theme 6)

................................ ................................ ... 8 2.2.5 Centrifuge Removal Efficiencies (comment theme 7)

................................ ................. 8 2.2.6 Solvent Loadings for Non

- Laundered Wipes (comment theme 8)

............................... 9 2.3 2003 Modeling Assumptions Underestimate Risk

................................ ................................ ...... 9 2.3.1 Solvent Limits, Loading Rates, and Wipe Usage (comment theme 9)

....................... 10 2.3.2 Exposure Parameters (comment theme 10)

................................ ................................ 11 2.3.3 Use of Dilution and Attenuation Factors (DAFs) (comment theme 11)

.................... 13 2.3.4 Ecological Risk and Human Food Chain Risk (comment theme 12)

......................... 13 2.3.5 Advective Transport (comment theme 13)

................................ ................................ . 15 2.3.6 Meteorological Conditions (comment theme 14)

................................ ....................... 15 2.3.7 Soil Characteristics (comment theme 15)

................................ ................................ ... 15 2.3.8 Biod egradation (comment theme 16)

................................ ................................ ......... 16 2.3.9 Peer Review Comments (comment theme 17)

................................ ........................... 16 2.3.10 Solvent Impact on Liners (comment theme 18)

................................ ......................... 18 2.4 Sufficiency of Data and Model

................................ ................................ ................................ .. 19 2.4.1 Laundry Sludge (comment theme 19)

................................ ................................ ........ 19 2.4.2 Use of Delisting Risk Assessment Software (DRAS) (comment theme 20)

.............. 19 2.5.1 Laundering Operations (comment theme 21)

................................ ............................. 20 2.6 Not Specific to Screening Assessment

................................ ................................ ...................... 21 2.6.1 Combustion of Wipes (comment theme 22)

................................ ............................... 21 2.6.2 Conside ration of Other Contaminants Including Metals (comment theme 23)

.......... 22 2.6.3 Solvent Wipes Evaluated Separately (comment theme 24)

................................ ........ 23 2.6.4 Complexity of the Proposed Rule (comment theme 25)

................................ ............ 25 2.6.5 Groundwater Monitoring and Corrective Action Controls (comment theme 26)

................................ ................................ ................................ ............................... 25 2.6.6 Banning Based on Toxicity Characteristics (TC) (comment theme 27)

.................... 26 2.6.7 Lifecycle Analysis and Recycling (comment theme 28)

................................ ............ 27 2.6.8 Concern Over Health of the U.S. Population (comment theme 29)

........................... 28

3. References

................................ ................................ ................................ ................................ ............ 29
Appendix A: Risk

- Related Comment sResponse to Comments on the Solvent Contaminated Wipes 2003 Risk Screening Analysis

1 

## Response to C omments on the Solv ent

- Contaminated Wipes Proposed 2003 Screening Risk Analysis

1. Introduction

On November 20, 2003, Environmental Protection Agency ( EPA ) published a notice of rulemaking on industrial wipes that proposed a conditional exclusion from the definition of solid waste for reusable wipes and a conditional exclusion from the definition of hazardous waste for disposable wipes

. During the comment period on the November 2003 proposed rule, we received substantive comments on the risk screening anal ysis and the solvent loading calculations. In addition to public comments, we received comments from external peer reviewers. Both the public and the peer reviewers questioned aspects of the risk screening analysis and the modeling assumptions. In response to comments on the risk screening analysis, the Agency undertook a more robust risk analysis to determine the potential risk from disposal of solvent

- contaminated wipes and laundry sludge in both unlined and lined

non

- hazardous waste landfills. This revis ed risk analysis was subjected to external peer review and presented for public comment, along with the peer review comments and EPA’s response to those comments, in a Notice of Data Availability (NODA) on October 27, 2009 (74 FR 55163).

The revised risk a nalysis is probabilistic in nature and used Monte Carlo methods to characterize the variability and uncertainty associated with the modeling. The revised risk analysis results included solvent

- specific, risk

- based mass loading limit (RB

- MLL) estimates for both unlined and composite

- lined landfill scenarios. In addition, the Agency developed and used a new landfill coupled reactor model (LFCR), which allowed the modeling to account for solvent biodegradation and partitioning between air, water, and solid pha ses while in the landfill. The probabilistic approach used in the revised risk analysis addresses to a great extent the potential to overestimate, or underestimate, the risks from disposal of solvent

- contaminated wipes and sludges in landfills.

This comme nt review and response report focuses on the techni cal themes highlighted by the public comments received on the 2003 screening analysis

. The subject of this review is the risk

- related comments. These comments are presented in Appendix A and may also be fo und in the docket for the rule making (EPA

- HQ

- RCRA

- 2003

- 0004). As applicable, the responses discuss how the comment issue s were addressed in the 2009 revised risk analysis ; see Risk

- Based Mass Loading Limits for Solvents in Disposed Wipes and Laundry Sludg es Managed in Municipal Landfills (U.S. EPA, 2009). Note that responses to comments on the risk

- based mass loading limits (RB

- MLL) used in the 2009 revised risk analysis are provided in Response to Comments on the Solvent Contaminated Wipes 2009 Risk Analy sis: Risk

- Based Mass Loading Limits

, which is located in the docket for this rule

. Also, see the docket for Response to Comments on the 2003 Proposal on the Landfill Loadings Calculations for Solvent

- Contaminated Wipes for responses to comments on the land fill loading calculations.



### 2. Response to Comments Received on the 2003 Risk Screening Analysis
Review of the public comments revealed a consistency in themes across comments. As a result

, the technical issues noted by the comment s were grouped into genera l themes as follows:



###  Preferential Treatment of Laundered Wipes and Sludge (Section 2.1)
1. Applied Different Modeling Assumptions
2. Established “ 5 gram limit ”



###  2003 Modeling Assumptions Overestimate Risk (Section 2.2)
3. Overall Modeling Framework
4. Landfill Charact eristics and Environmental SettingResponse to Comments on the Solvent Contaminated Wipes 2003 Risk Screening Analysis

2 5. Groundwater Leachate Concentration

6. Distance to Receptors

7. Centrifuge Removal Efficiencies
8. Solvent Loadings for Non

- Laundered Wipes



###  2003 Modeling Assumptions Underestimate Risk
9. Solvent Limits, Loading Rates

, and Wipe Usag e 10. Exposure Parameters
11. Use of Dilution and Attenuation Factors (DAFs)
12. Ecological Risk and Human Food Chain Risk
13. Advective Transport
14. Meteorological Conditions
15. Soil Characteristics
16. Biodegradation
17. Peer Review Comments
18. Solvent Impact on Liners



###  Sufficiency of Data and Model (Section 2.4)
19. Laundry Sludge
20. Use of Delisting Risk Assessment Software (DRAS)



###  Potential Exposures before Landfilling (Section 2.5)
21. Laundering Operations



###  Not Specific to Screening Assessment (Section 2.6)
22. Combustion of Wipes
23. C onsideration of Other Contaminants Including Metals
24. Solvents Wipes Evaluated Separately
25. Complexity of the Proposed Rule
26. Groundwater Monitoring and Corrective Action Controls
27. Banning Based on Toxicity Characteristics (TC)
28. Life Cycle Analysis
29. Concern Over Health of the U .S. Population

.

The comments grouped in Section 2.6 capture and identify issues that were not specific to the risk screening analysis , but were generally related to the overall risk evaluation

.
The remainder of this section is organized according to the above themes and presents EPA ’ s response to each are a of interest. To fa cilitate linking these response themes to the actual comments shown in Appendix A

, Table 1 provides a cross

- walk between the themes and comments

.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

3 Table 1. Comment Summaries for the 2 003 Screening Risk Assessment

Comment er Identifier Comment Themes

Preferential Treatment of Laundered Wipes and

Sludges Modeling Assumptions Overestimate Risk Modeling Assumptions Underestimate Risks Sufficiency of Data and Model Potential Exposures

befo re Landfilling Not Specific to Screening Assessment

0199

- Hearing Transcript, Art Abell, Cando Co. 1 2 1

0199

- Hearing transcript

- Ralph Solarski

- Kimberly Clark. 1 2 5

0199

- Hearing Transcript

- David Dunlap, Uniform and Textile Service Association 2 1

0199

- Hearing Transcript

- David Case, ETC 4 1 8

0199

- Hearing Transcript

- David Case, ETC 2 3

0223

- Mervyn M. Dymally, California State Assembly 2 1 2 3

0257

- Kimberly Clark 1

0271

- CTDEP 19 22

0272

- George H. Larson 1, 2

0272

- George H. Larson 2 1

0281

- Graphic Arts Coalition 2 7

0281

- Graphic Arts Coalition 7

0283

- INDA/SMART 1, 2 7 2 5 ,2 7

0283

- INDA/SMART 1, 2 7

0283

- INDA/SMART 1 , 2 7

0283

- INDA/SMART 1 , 2 4,7 2 7

0283

- INDA/SMART 2 3, 4, 5,6,7 17 2 6

0283

- INDA/SMART 1 , 2 6,7,8 19 2 1

0288

- ETC 9 through 1 8 19, 20 2 1

0289

- AMEC 9,10,11,12 ,1 8 2 3 ,2 4

0312

- JR Simplot NA

– Commenter agrees with EPA’s risk screening analysis

0316

- VT Hazardous Waste Management Program 4 1 8

03 19

- American Reusable Textile Association 2 9

0320

- National Paint & Coating Association 2 4 , 8Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

4 Comment er Identifier Comment Themes

Preferential Treatment of Laundered Wipes and

Sludges Modeling Assumptions Overestimate Risk Modeling Assumptions Underestimate Risks Sufficiency of Data and Model Potential Exposures

befo re Landfilling Not Specific to Screening Assessment

0323

- Cement Kiln Recycling Coalition 17 , 21

0325

- ASTSWMO 12 2 0 2 1

0330

- AR DEQ 12

0330

- AR DEQ 12

0330

- AR DEQ 22

0330

- AR DEQ 12

0330

- AR DEQ 2 0

0346

- USWAG by Piper Rudnick 1,2 2 7

0348

- Uniform and Textile Services Association

- Textile Rental Services Association 2 1

0348

- Uniform and Textile Services Association

- Textile Rental Services Association 1 19

0350

- Tennessee Valley Authority 4

0353

- American Trucking Associations NA

– Commenter agrees with EPA’s risk screening analysis

0357

- Phelps Dodge Corporation 12 2 7

0357

- Phelps Dodge 21Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

5 

### 2.1 **Preferential Treatment of Laundered Wipes and Sludge** 

2.1.1 Applied Different Modeling Assumptions (comment theme 1)



### Comment: Several of the commenters express concern that the 2003 deterministic screening analysis applied different assumptions for reusable (laundered) and disposable (non

la undered) solvent

- contaminated wipes and seemingly provided preferential treatment for reusable wipes. In particular, there is concern that two very different sets of assumptions were applied in evaluating the potential risks from the management of the solv ent

- contaminated wipes in landfills. For example, it was noted that high

- end parameter assumptions were applied for disposable wipes and central

- tendency assumptions were applied for reusable wipes.

R esponse: This concern was addressed in the 2009 risk an alysis, which makes no distinction between solvent

- contaminated wipe types. Using a probabilistic national

- level modeling framework, the 2009 analysis evaluated the management of solvent

- contaminated wipes and industrial laundry sludge in “nonhazardous was te landfills.” Modeling was performed for solvent

- contaminated wastes (i.e., wipes and sludge) using an assumed unitized mass loading rate (i.e., 1 kg per year) for each liner type, exposure pathway, and receptor. The revised risk analysis estimated risk

- b ased, mass loading limits (RB

- MLL s ) for each F

- listed solvent that, if contained on any industrial wipe or in laundry sludge, would not exceed EPA’s risk criteria if these materials were disposed of in unlined or composite lined nonhazardous waste landfill s. These RB

- MLLs were compared to estimated landfill loading rates (ELLRs). These rates estimate the annual quantities of solvents remaining in wipes and laundry sludge when disposed in landfills within the United States. The ELLRs were developed using the best available data gathered from a variety of sources using a Monte Carlo approach designed to account for uncertainty and variability in the input parameters.

2.1 .2 Established “ 5 gram limit ” (comment theme 2)

Comment: Under the proposed rule, t he const ituents shown below in Table 2 were identified based on the 2003 risk screening analysis to be eligible for disposal in a municipal or non

- hazardous waste landfill if they meet the “ dry ” condition (i.e., contains less than five grams of solvent). As stated in the proposed rule, EPA chose five grams to be the standard for this condition because it falls within the
rang e found in the risk screening analysis to not pose a substantial hazard to h uman health and the environment and it is also within the range of what is achievable through use of advanced solvent

extraction processes (e.g., centrifuging or other high

- performance solvent

- extraction or

- removal technology). [68FR 65598]

Table 2. 19 Listed Solvents that May Be Disposed of in a Municipal Landfill unde r the 2003 Propos e d Rule

1,1,1

- Trichloroethane Acetone Ethyl Acetate
1,1,2

- Trichloroethane Butanol Ethyl benzene
1,1,2

- Trichlorotrifluoroethane Carbon Disulfide Ethyl Ether
1,2

- Dichlorobenzene Cyclohexanone Isobutyl Alcohol

2

- Ethoxyethanol Dichlorodifl uoromethane Methanol

In response to the five gram limit, commenters noted that they believe that this limit is unjustified from a human health and environmental r isk standpoint and therefore is arbitrary and capricious and should be eliminated . Of particu lar concern is the practicality of generators of disposable wipes meet ingResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

6 this standard by having access to centrifuging or other advanced solvent extraction equipment needed to comply

. As a preferred alternative to the five gram limit, comment er s supporte d hand

- wringing , which EPA has found will remove a meaningful amount of solvent (up to 68 percent according to the Technical Background Document)

.
Response : Under the 2009 analysis, the five gram limit is not considered explicitly

. Alternatively, the anal ysis developed solvent

- specific RB

- MLLs for unlined and lined landfills using a unitized mass loading approach. 

### For most solvents, EPA used empirical data from measurements of the amount of solvents found on disposed wipes; for other solvents the Agency us ed data on the amount of solvent applied to the wipes and made conservative assumptions of the fraction that remains in the disposed wipes. The resulting solvent

- specific limits were then compared to solvent specific ELLRs to determine whether current indu stry practices could potentially result in exceeding RB

MLLs for the F001

– F005 solvents. 

### The results of the final risk analysis demonstrate that wipes contaminated with certain solvents and laundry sludge may be sent to lined landfills without posing sig nificant risks to human health and the environment. Because target risk thresholds in the risk analysis were not exceeded when accounting for levels of solvent contained in wipes, EPA finds that the five gram limit for disposable wipes that are sent to lan dfills is not necessary to protect human health and the environment and, moreover, would be impossible to implement and enforce. Instead, solvent

- contaminated wipes that are sent to landfills must meet the same “no free liquids” condition for wipes that ar e sent to laundries, dry cleaners, and combustors. This "no free liquids" condition reduces human exposure to free liquid spent solvent during transport, handling, and final disposition of the wipes and ensures that solvent

- contaminated wipes contain no fr ee liquids in compliance with the municipal solid waste regulations.

**2.2 2003 Modeling**  **Assumptions Overestimate Risk** 
Several commenters expressed concern that the 2003 screening approach was overly conservative

. Table 3 identifies key comments received o n 2003 analysis and summarizes how the revised 2009 probabilistic analysis addressed these concerns. In addition, each of these key areas is discussed in greater detail below.

Table 3 . Modeling Assumptions Overestimated Risk in Screening Analysis

Parameter Comment on 2003 Screening Analysis 2009 NODA Probabilistic Analysis
Overall Modeling Framework Deterministic a pproach Probabilistic modeling was implemented using Monte Carlo methods to characterize variability and uncertainty

Landfill Characteristic s  Small landfill in a wet climate

 U nlined landfill

 Failure to adequately consider naturally occurring binding and removal mechanisms (e.g., degradation).  Performed n ational

- level modeling that included landfills of varying geometry and located throughout t he contiguous U.S.

 Modeling scenarios included both unlined and lined landfill s

.

 The modeling approach was revised and a new landfill coupled reactor (LFCR) model was developed.

Groundwater leachate concentration  U se of 5th (rather than the 10th)
perce ntile leachate concentrations to well concentrations;

 Unexplained use of the highest nine

year average leachate concentrations Probabilistic modeling was performed with EPACMTP using distributions of leachate output by the LFCR model.

Distance to receptor s Inhalation risks evaluated at 75 meters from the landfill R eceptor distance and direction were varied.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

7 Parameter Comment on 2003 Screening Analysis 2009 NODA Probabilistic Analysis
Centrifuge removal efficiency Centrifuging would remove only 90% of the solvent even though EPA Technical Background Document reveals that properly co nducted centrifuging of disposable wipes results in 95

- 100% removal efficiencies Not applicable

– Applied a two

- phased probabilistic approach to develop RB

- MLL and ELLRs.

Solvent Loadings for N on

- Laundered Wipes Overly conservative assumptions about the w ipe market and its contribution to solvent l oadings. ELLRs were developed using a Monte Carlo approach designed to account for uncertainty and variabilit y.

2.2.1 Overall Modeling Frame work (comment theme 3)

Comment: Comments were received on overall use of a “ deterministic ” a pproach to evaluate solvent

- specific risks from landfilling (e.g., use of a “ worst

- case ” small landfill size and wet climate rather than incorporating landfill size and climate into a probabilistic Monte Carlo analysis)

.
Response : Th e revised 2009 risk analysis did not use a deterministic approach . The revised analysis was probabilistic and was implemented using Monte Carlo methods to characterize the variability and uncertainty associated with the modeling. The implemented framework and data development approach applied in support of the 2009 analysis generally follow ed major Agency guidance documents, including, for example, the Risk Assessment Guidance for Superfund Volume 3 Part A: Process for Conducting Probabilistic Risk Assessme nt (RAGS 3A) (U.S. EPA, 2001 a ) and the Guiding Principles for Monte Carlo Analysis (U.S. EPA, 1997 b ). For more details, see section 2.2.4 Data Development of the revised risk document (U.S. EPA, 2009).

2.2. 2 Landfill Characteristics and Environmental Sett ing (comment theme 4 )

Comment: Several comments were received that expressed concern that the modeled landfill characteristics resulted in overly conservative risk estimates that were not representative of actual management conditions. The characteristics most frequently noted as overly conservative included the following:



###  M odeling a s mall landfill in a wet climate: It was noted by the commenters that the EPA employed “ high

- end ” (highly conservative) assumptions that included the modeling of a small landfil l in a wet climate for purposes of analyzing risks from landfilled non

- laundered wipes.



###  A ssum ing an Unlined landfill : Comments were received on the fact that the 2003 analysis considered releases from an unlined landfill scenario. The commenters charge tha t this scenario was too conservative because most sanitary landfills are equipped with liners and leachate collection systems.



###  F ailure to consider naturally occurring constituent removal mec hanisms (e.g., degradation) : Commenter s were concerned that the 20 03 analysis failed to adequately consider degradation effects of organic constituents in media transport pathways, failed to adequately consider the effect of evaporation of solvents on landfill loading rates, and assumed that all solvents in a wipe

were a vailable for release, rather than being irreversibly bound to the wipe.

Response:



###  Small landfill in a wet climate : In the revised risk analysis

, a probabilistic approach was applied because solvent

- contaminated wipes and laundry sludge can be disposed of in landfills of varyin g geometry (e.g., surface area), with varying operating conditions (e.g., operating life), and located in many different parts of the country. Thus, each realization in the theoretical distribution of 10,000 risk outputs represents a unique set of input values that were randomly selected withResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

8 respect to the landfill characteristics, location, hydrogeology, receptor location, exposure factors,

etc.



###  U nlined Landfill : Under the 2009 risk assessment, modeling was performed using both an

u nlined scenario and a c omposite liner scenario. The liner modeled under the latter scenario was assumed to consist of a geomembrane layer and soil. The liner leakage r ates applied under the s e scenarios were based on monthly average leak detection system (L DS) flow rates collected from empirical data; see section 3.1.2.1 Infiltration and Liner Leakage Rates , in the 2009 risk document (U.S. EPA, 2009 ). Modeling results were used to develop solvent

- specif ic estimates for each liner condition

.



###  Naturally Occurr ing Constituent Removal and Binding Mechanisms : In the 2009 analysis, the mode ling approach was revised and a new landfill coupled reactor (LFCR) model was developed and applied. Biodegradation within the LFCR model was accounted for using a single,

most c onservative available value for the biodegradation rate. Mass transfer of volatile contaminants to the atmosphere was modeled through evaporation and advective flow within landfill gas (primarily methane generated from waste degradation). In addition , t he revised risk modeling accounted for the partitioning between air, water, and solid phases using standard, accepted modeling approaches. The modeling thus accounted for adsorption to solid phases within the landfill, including the potential adsorption to di sposed wipes material.

2.2 .3 Groundwater Leachate C oncentration (comment theme 5)

Comment: Comments were received that question the use of the 5th (rather than the 10th) percentile value from the distribution of ratios of leachate concentrations to well c oncentrations and the unexplained use of the highest nine

- year average leachate concentrations as input to the groundwater modeling.

Response : This concern was addressed under the 2009 revised risk assessment using a national

level, probabilistic modeling approach . Within this framework, the LFCR model was run to develop distributions of leachate estimates which were used as input to the EPA ’ s Composite Model for Leachate Migration with Transformation Products (EPACMTP) groun dwater model (U.S. EPA, 2003a,c ). The output of EPACMTP is a database of annual peak and time

- averaged solvent concentrations arriving at randomly selected downgradient groundwater receptor well locations. The time

- averaged solvent concentrations were used as input to the downstream exp osure model.

2.2.4 Distance to Receptors (comment theme 6)

Comment: Comments were received on the fact that inhalation risks were evaluated at 75 meters from the landfill rather at a distance based on a national distribution, as was used for groundwater we ll distance.

Response : The 2009 revised analysis addresses this concern by varying receptor distance s and direction s to simulate locating individuals in any of 36 directions at any of 8 different distances from the edge of the unit. See s ection 3.2 of the risk document (U.S. EPA, 2009).

2.2 .5 Centrifuge Removal Efficiencies (comment theme 7)

Comment: Comments were received that pointed out that the assumption that centrifuging would remove only 90% of the solvent was overly conservative. EPA ’ s own Technica l Background Document (at page 67) reveals that properly conducted centrifuging of disposable wipes results in 95

- 100% solvent

removal efficiencies

.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

9 A specific comment relating to removal efficiencies for methyl ethyl ketone (MEK) recommended removing MEK from the listing of banned solvents since EPA ’ s own risk assessment d id not justify its inclusion and the EPA ’ s report “ Evaluation of the Solvent Extraction Efficiency of an Industrial Centrifuge on a Variety of Shop Towels and Wipes, ” states, “ that the s olvent that seemed to b e most easily extracted was MEK ” and notes that MEK ’ s removal efficiency was 99 percent. Based on the removal efficiency of MEK of 99 percent rather than 90 percent, the commenter requests the Agency to reevaluate the inclusion of ME K as one of the banned solvents.

Response : Under the 2009 analysis, these concerns were addressed in that specific removal technologies were not explicitly considered in estimating risks. Instead, a two

- phase probabilistic approach was applied to estimate risk

- based, mass loading limits and ELLRs for each F

- listed solvent

. The ELLRs were then used to determine whether current industry practices could potentially result in exceeding the RB

- MLLs for the 20 F001

– F005 solvents considered in the analysis. The ELLR analysis did not include a ‘what if’ analysis regarding the increase in use of solvent extraction technology for disposable wipes. The purpose of the analysis was to estimate landfill loading based on current wipes management methods without additiona l use of technologies such as a centrifuge. Regarding MEK, EPA notes that, based on the revised risk analysis, MEK is now included in the exclusion in the final rule.

2.2 .6 Solvent Loadings for Non

- Laundered Wipes (comment theme 8)

Comment: Commenters stat ed that under the 2003 analysis

, EPA applied an arbitrary “ high

- end ” parameter of 35 percent as the percentage of solvent

- soiled non

- laundered wipes ( SSNWs ) assumed to contain one or more F

- listed solvents.

Response : To address concerns related to solvent loadings, the EPA conducted a thorough analysis and developed representative ELLRs using the best available data gathered from a variety of sources using a Monte Carlo approach designed to account for uncertainty and variability in the input parameters. T he new approach applied in developing these rates is presented in EPA’s Landfill Loading Calculations for Disposed Solvent

- Contaminated Wipes and Laundry Sludge Managed in Municipal Landfill (U.S. EPA, 2008; referred to the “Landfill Loading Report” in thi s document). The Landfill Loadings Report no longer includes a separate factor (such as 35 percent) for estimating the percentage of wipes containing F

listed solvents. Instead, the number of facilities assumed to generate F

- listed solvent

- contaminated dis posable wipes was estimated from the Economics Background Document (Estimate of National Economic Impact of Conditional Exclusion of Solvent Industrial Wipes from RCRA Hazardous Waste Regulation (RCRA

- 2003

- 0004

- 0004), updated to 2002 data). T he updated ver sion of the Landfill Loading Report is in the docket for the final rule Landfill Loadings Calculations for Solvent

- Contaminated Wipes

, January 2012 . Also, see the docket for Response to Comments on the 2003 Proposal on the Landfill Loadings Calculations fo r Solvent

- Contaminated Wipes for responses to comments on the landfill loading calculations.



### 2.3 **2003 Modeling Assumptions Underestimate Risk**

C o mments were received that expressed concern that the 2003 screening approach underestimated risk

. Table 4 iden tifies key technical issues identified by these commenters and summarizes how the revised 2009 probabilistic analysis addressed these concerns. E ach of these k ey issues as well as others as other s are discussed in greater detail below.

Table 4

. Modeling As sumptions Under estimated Risk in Screening Analysis

Parameter Comment on 2003 Screening Analysis 2009 NODA Probabilistic AnalysisResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

10 Parameter Comment on 2003 Screening Analysis 2009 NODA Probabilistic Analysis

Solvent Limit, Loading Rates and Wipe Usage  5 gram s olvent limit will not be met

 W ipe usage assumption is low

 Adjustment fact ors applied regarding percentage of F

- solvents used and present on wipes are arbitrary and not appropriate. Applied p robabilistic modeling approaches to develop distributions of solvent

- specific RB

- MLLS and ELLRs

Exposure Parameters  High

- end values are n ot used, as required by EPA itself in its 1992 Exposure Assessment Guidance for Inhalation Rates, Exposure Duration

a nd Drinking Water Ingestion Rate

 The exposure period of an adult is assumed at only 10 years.

 Child exposure is assumed at 7 years. Data di stributions for exposure factors were developed based on the EPA Exposure Factors Handbook (EFH, U.S. EPA, 1997a ) and the review draft of the Child

- Specific Exposure Factors Handbook (Chi ld

- Specific EFH, U.S. EPA, 2006a ).

Use of Dilution and Attenuation Factors (DAFs) Use of Dilution and Attenuation Factors (DAFs) used to estimate exposure point concentrations are inappropriate Probabilistic modeling performed with EPACMTP

Ecological Risk and Human Food Chain Risk  Ecological risk is not fully evaluated.

 No food chain risk is evaluated Consistent, with the 2003 analysis, the 2009 analysis focused on significant pathways that would drive the risk

- based mass loading rates

Advecti ve Transport Advective transport was not evaluated Using the newly developed LF CR model, advective flow within landfill gas was modeled Meteorological Conditions Air emissions, groundwater and other meteorological risk factors were based

on Houston, TX and Lincoln

, NE, when other areas could be higher in risk National

- level modeli ng was performed using data from 57 representative meteorological regions cross

- referenced with data from the EPACMTP climate centers

Soil Characteristics Use of national averaged soil data characteristics without any consideration of more complex geolog ies will underestimate risks for many regions. National

- level modeling was performed using EPACMTP regional soil types

Biodegradation The assumption of degradation understates risk by as high as a factor of 7. Biodegradation within the LFCR model

was acco unted for using a single, most conservative available value for the biodegradation rate.

Peer Review Comments Peer r eview issues were not addressed. The modeling approach was revised

, input data sets were created, and a new landfill coupled reactor (LFCR) model was developed. The 2009 analysis was peer reviewed.

2.3 .1 Solvent Limits, Loading Rates
, and Wipe Usage (comment theme 9)

Comment: C omments were received that indicated t hat the five gram criterion will not be met and the EPA needs to recognize th e limitations of the extraction processes. A review of removal efficiency data in the docket indicates that no extraction technology can be routinely relied upon to yield less than five grams, with the possible exception of centrifuging which EPA is not ma ndating. T he more commonly applied techniques of hand wringing or use of a screen bottom drum will result in as high as 75 grams of solvent remaining on a wipe. The commenter believes that the risk must be modeled based on the maximum level expected follow ing extraction, other than centrifuge, which is 75 grams.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

11 Concerning wipes usage, the commenter points out that the r is k a ssessment assumes 120 wipes per day for large quantity generators ( LQGs ) and 30 wipes per day for small quantity generators ( SQGs )

. Ho wever, docket data indicates wipe usage rates of 400 to 1

, 000 per day for many LQGs (e.g., printing and aerospace sectors), “ several hundred ” per day for automobile manufacturers, and 50 to 100 wipes per day for a typical auto body repair shop.

In additio n , the approach used in the 2003 screening risk a ssessment appears to be model ing a certain amount of solvent contaminant with no reduction of the overall results based on assumptions regarding the percentage of F

- solvents likely to be used in in dustry or present on the wipe. However, the docket data indicate that weighting factors of 35% were applied for F

- solvent constituents and 10 % for characteristic solvents. This is based on an assumed probability that a given wipe user would only apply an F

- listed s olvent 35% of the time and a character istic solvent 10% of the time. As a result, the commenter states that s uch an arbitrary assumption is not appropriate

.
Response : Under the 2009 revised risk analysis, the five gram limit is not considered explicitly

. A lternatively, probabilistic national

- level modeling was performed for solvent

- contaminated wastes (i.e., wipes and sludge) using an assumed unitized mass loading rate (i.e., 1 kg per year) for each liner type, exposure pathway, and receptor. As discussed p reviously, the resulting RB

- MLLs were then compared to estimate d landfill loading rates (ELLRs)

. These rates represent the annual quantities of solvents remaining in wipes and laundry sludge when disposed in landfills within the United States. The ELLRs we re developed using the best available data gathered from a variety of sources using a Monte Carlo approach designed to account for uncertainty and variability in the input parameters.

Concerning wipe usage, the landfill loadings calculations in t he new La ndfill Loading Report include the number of wipes used per year per generator. Rather than using a fixed value, the Landfill Loading Report used a range of values to correspond to the range of usage rates by sites. In addition, different usage rates were p repared for different generator types. This is discussed in Section 2.3.1 of the Landfill Loadings Report. These usage rates were based on data in the record, such as those sources cited by the commenter.

Regarding weighting factors used for the usage of F

- listed solvents, t he new Landfill Loading Report no longer includes a separate factor (such as 35 percent) for estimating the percentage of wipes containing F

- listed solvents. Instead, the number of facilities assumed to generate F

- listed solvent

contamin ated disposable wipes was estimated from the Economics Background Document (Estimate of National Economic Impact of Conditional Exclusion of Solvent Industrial Wipes from RCRA Hazardous Waste Regulation (RCRA

- 2003

- 0004

- 0004), updated to 2002 data).

See the docket for Response to Comments on the 2003 Proposal on the Landfill Loadings Calculations for Solvent

- Contaminated Wipes for responses to comments on the landfill loading calculations. Also, see the docket for the final landfill loading report Loadings C alculations for Solvent

Contaminated Wipes , January 2012.

2.3 .2 Exposure Parameters (comment theme 10)

Comment: EPA received comments on the 2003 risk screening analysis stating that recommended high end exposure values are not used, as required by EPA in its 1992 Exposure Assessment Guidance for Inhalation Rates, Exposure Duration and Drinking Water Ingestion Rate. In addition, it was noted by a commenter that the exposure period of an adult was assumed to be only 10 years. However, for other risk assessme nts periods of 30 to 70 years are required. Furthermore, it was noted that child exposure is assumed at 7 years with no justification. The commenters stated that t he risks numbers provided for the child scenario are therefore inadequate.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

12 Response : The revi sed risk analysis presented in the 2009 NODA addresses these comments primarily through the use of data distributions for exposure factors which were developed based on the EPA Exposure Factors Handbook (EFH, U.S. EPA, 1997a) and the review draft of the Ch ild

- Specific Exposure Factors Handbook (Child

- Specific EFH, U.S. EPA, 2006a). For this analysis, exposure duration was assumed to correspond with the receptor’s residence time in the same house as determined using EFH data on residential occupancy. Because the data used to develop parameter information for resident receptors were age specific, separate distributions were developed for adult and child residents. Exposure durations used in this probabilistic analysis are provided in Appendix I of the revised risk analysis (U.S. EPA, 2009).

In the revised risk analysis, f or the critical groundwater pathway, we estimated risks for each individual exposure route for the adult (ingestion of drinking water, inhalation during showering, dermal contact during show ering). Because these exposure routes can occur during the same time period for carcinogens, we calculated a combined cancer risk by summing the risks for these three exposure routes. Note that this approach may slightly overestimate combined risk because the model does not subtract the solvent mass available for one shower exposure route (e.g., inhalation) from the mass available for the other shower exposure route (e.g., dermal contact). For children, we estimated the combined cancer risk due to ingestion of drinking water and dermal contact during bathing by summing the route

- specific risk estimates.

For the child receptor, we did not simulate volatilization from the bath and subsequent inhalation for two reasons. First, by definition, the RfC is deriv ed to be protective of all human population including sensitive subgroups for noncancer risks. Because we assume that the solvent mass that enters the air during showering is likely to be greater than the solvent mass that could enter the air during bathin g, the concentration to which adults are exposed during a shower event is likely to be higher than that of children during bathing . For example, the bath water temperature for children is expected to be somewhat lower than the water temperature for showers , which would reduce the potential for volatilization of chemical solvents into the air. Second, for cancer endpoints, adult exposures have been shown to drive the risks. This is typically the case because the calcul ated risk is based on the ratio between exposure duration and averaging time, which is almost always higher for adults than for children

.
The objective of the revised risk evaluation was to determine the lowest mass loading that would not exceed the target risk, not to analyze all possible expo sures. EPA believes that the adult shower inhalation pathway provide s a sufficiently protective estimate of potential risk/hazard from inhalation while bathing for all receptors. The revised risk analysis presented in the 2009 NODA included a variety of co nservative assumptions to ensure that potential risks from landfill disposal were assessed protectively. Furthermore, our evaluation was based on the risks at the upper end of the risk distributions, i.e., the 90th percentile in the probabilistic analyses. In any case, the final risk analysis indicates that the risks for the solvent

- contaminated wipes in composite

- lined landfills are well below the target risk criteria for all of the solvents (except for trichloroethylene, which is not eligible for the exem ption); t he solvent landfill loadings are below one tenth of the risk

- based mass loading limits. 1

Regarding comments that the Combustion Risk Assessment Guidance suggests that infant scenarios should be addressed including impacts from nursing , the revis ed risk analysis did not evaluate this type of i nfant exposures for the landfill sce n ar io because dioxins, furans, and dioxin

- like polychlorinated biphenyls (PCBs) were not constituents of concern. The Human Health Risk Assessment Protocol for Hazardous Wa ste Combustion Facilities (U.S. EPA, 2005) only provides guidance for

1 See the risk results in F001

- F005 Solvent

- Contaminated Wipes and Laundry Sludge: Comparison of Landfill Loading Calculations and Risk

- Based Mass Loading Limits ” in the docket for the final rule.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

13 evaluating these specific constituents of concern and does not provide guidance for evaluating infant exposures to other constituents (such as solvents) via the ingestion of breast milk

.

2.3 .3 Use of Dilution and Attenuation Factors (DAFs) (comment theme 11)

Comment: Comments were received on the 2003 approach that applied u niversal DAF factors derived using general soil characteristics and a generic CMTP model, without any consideration for the behavior of the actual contaminants of concern. In one case, it was noted that the commenter felt the DAFs were inflated by a factor of 10.

Response : This comment was addressed under the 2009 probabilistic analysis

, which included national

- level modeling using the EPA ’ s Composite Model for Leachate Migration with Transformation Products (EPACMTP) groundwater model (U.S. EPA, 2003a,c). This model was used to perform solvent

specific modeling using the leachate estimates produced by the LFCR model. Generic DAFs were not used in the revised risk analysis. EPACMTP has been the subject of multiple peer reviews and has been through a formal review process with EPA ’ s SAB. In addition, the EPACMTP and supporting databases have been used in at least eight r isk analyses that have been through a combination of peer and SAB reviews (e.g., the Dyes and Pigments listing determination , EPA, 2003b ). The output of EPACMTP is a database of annual peak and time

- averaged solvent concentrations arriving at randomly sele cted downgradient groundwater receptor well locations. The resulting time

- averaged solvent concentrations were used as input to the downstream exposure models.

2.3 .4 Ecological Risk and Human Food Chain R isk (comment theme 12)

Comment: Commenters believe t hat the 2003 ecological screening analysis is deficient because it included only 10 of the 34 solvent constituents. Contrary to EPA ’ s conclusion on page 118 of Document

- 0003, all of the constituents fail the aquatic benchmarks, showing that there is substa ntial ecological risk from the proposed rule. As it stands, EPA ’ s ecological screenin g analysis was not conservative because it left out most of the solvent constituents and assumed excessive stream flow and dilution.

In addition, c omments were received th at stated that t he 2003 screening risk assessment failed to consider other important human indirect exposure pathways that are required by other programs, such as Superfund and Hazardous Waste Combustors. For example, there is no a ssessment of food chain r isks

. The commenters also pointed out that th e risk assessment also fails to address runoff and erosion and to address particulate emissions because a daily cover is assumed

. Yet volatilization of the solvent can occur into the daily cover soil layer and d ispersed by wind. Also of concern is l int or dirt saturated with solvent

or metal particles dispersed by the wind.

Response : As discussed above, EPA received comments on the lack of conservatism in the 2003 risk screening analysis; these comments covered c ertain modeling assumptions and gaps in available data. To address peer review and public comments regarding the importance of exposure pathways in determining the protective risk

- based mass loading limits , EPA reevaluated the potential for risk via indire ct exposure pathways as well as the potential for significant impacts on valued ecological attributes

. On October 27, 2009, EPA published a NODA that presented the revised methodology and results. As discussed below, EPA believes that the revised methodolo gy has substantively addressed the above comments on the 2003 risk assessment.

Indirect human health exposure pathways

– During the problem formulation stage of the 2009 risk analysis, EPA decided that the risk

- based mass loading rates should be developed for the exposure pathways that po sed the greatest potential concern. In other words, the risk

- based rates would be protective of all exposure pathways including those that represent relatively minor contributions to theResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

14 overall risk. As such, EPA consider ed the physical and chemical properties of the chemicals of interest and decided to focus primarily on direct exposure pathways. As discussed in section 2 of the RB

- MLL report, the 20 solvents evaluated include a wide range of volatile and semi

- volatile or ganic chemicals, most of which have relatively short environmental half

- lives (as compared to persistent organic chemicals). As with most organic solvents, diffusion and advection into the air are the primary release mechanisms into the environment and are the main reason many of these solvents can be used only with adequate ventilation. Moreover, a number of these solvents (e.g., benzene, toluene, and xylene) have been identified as groundwater contaminants at Superfund RCRA Corrective Action sites. Conseq uently, the leaching

- to

- groundwater pathway was also considered a primary release mechanism. The generally low values for partition coefficients for these solvents (e.g., the tendency for the solvent to volatilize) strongly suggests that indirect exposure pathways (e.g., plant uptake of vapors and subsequent ingestion of contaminated produce) will either be incomplete or contribute negligibly to total exposure.

The conclusion that volatile and semi

- volatile organic solvents are insignificant contributors t o risk via indirect exposure pathways (for a landfill source) is consistent with other risk analyses of landfill waste management scenarios (see for example, the risk analysis performed for the 

### Paint and Coatings Hazardous Waste Listing Determination [U.S. EPA, 2001b]). Thus, direct exposure pathways to air and groundwater were the primary focus of the risk modeling for wipes and laundry sludge. Furthermore, landfills maintain controls for particulate air releases and for soil erosion and runoff; regulation s for municipal solid waste landfills include run

- on/runoff controls (40 CFR 258.26), daily cover (§ 258.21), and compliance with the CAA requirements (§ 258.24). Thus, the primary focus of the risk modeling was to assess direct exposure pathways to the ai r and groundwater. EPA is not aware of information suggesting that including these indirect exposure pathways would alter the RB

- MLLs , nor did the commenter provide any such information

.

Soil erosion and runoff

– As noted above, e xisting regulations for MS WLFs are designed to minimize the likelihood of run

- on and runoff. For example, under 40 CFR Section 258.26, the owner or operator is required to prevent run

- on to the active portion of the landfill units and to collect and control

run

- off from the active portion for a 25

- year storm. In addition, runoff controls are a legal requirement of the EPA’s National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act. Therefore, based on existing regulations issued to control runoff and erosion, EPA eliminated runoff pathways from the risk assessment.

Ecological Risk

- The 2009 RB

- MLL report explains that potential exposures to aquatic life associated with surface water contamination due to groundwater interactions were not modeled because this would have required site

- specific information on nearby waterbodies to determine



###  that there is a receiving waterbody capable of sustaining aquatic life



###  the waterbody provides habitat for valued ecological attributes



###  the dilution/attention attributable to t he

− hydrogeological characteristics of the subsurface

− distance between the landfill and the waterbody, and

− capacity of a lake/pond or flow rate for a stream/river.
For chemical constituents that are potentially persistent and/or bioaccumulative in aquatic

e nvironments, the EPA would typically conduct a quantitative screening analysis to better understand the potential for adverse ecological effects. However, the solvents evaluated have low octanol

- water partition coefficients (i.e., these chemicals are relat ively water soluble and tend not to bioaccumulate) and tend to degrade rapidly in aqueous environments, especially in surface water (e.g., see, for example, biodegradation rates for the solvents as shown in Appendix B

, U.S. EPA, 2009 ) . Given the chemical

-Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

15 p hysical properties of solvent constituents, the opportunity for dilution and attenuation prior to any ecological exposure , and the localized nature of any sort of ecological impact, the EPA does not believe that potential risks to aquatic ecosystems would drive the RB

- MLLs. That is, the predicted risk to human health for individuals living in proximity to a landfill that manages industrial rags and wipes will be greater than the risks to aquatic ecosystems . As a matter of policy, EPA chose the upper end of the risk distribution (i.e., the 90 th percentile) to establish the RB

- MLLs ; this approach to protecting human health builds an additional layer of conservatism into these limits. Therefore, EPA chose to focus on the most significant risks, as appropriate, to establish RB

- MLLs that would be protective of human health and the environment with a high degree of certainty

.

2.3 .5 Advective T ransport (comment theme 13)

Comment: Comments were received on the 2003 screening expressing concern that adve c tive transpor t was not considered. The failure to consider advective transport of solvent contaminants through landfill gas was viewed as a major flaw that underestimates risk associated with the air pathway. In fact,

t hese losses would continue even after a landfill c over is applied and also throughout the post closure period.

Response : In the 2009 revised risk analysis, advective transport was addressed. The revised mode ling approach used a new landfill coupled reactor (LFCR) model

, which included algorithms for consi dering advective transport

. As part of this model, m ass transfer of volatile contaminants to the atmosphere was modeled through evaporation as well as through advective flow within landfill gas (primarily methane generated from waste degradation). Furtherm ore, the revised risk analysis modeled releases after the landfills are closed.

2.3 .6 Meteorological Conditions (comment theme 14)

Comment: Comments were received on the fact that a ir emissions, groundwater and other meteorological risk factors were based in 2003 exclusively on conditions in Houston, T exas , and Lincoln

, Nebraska

, while other locations in the country could be higher in risk . As a result , the screening could understate risk for major regions of the U nited States

. As an alternative, the EPA sh ould evaluate areas with high industrial density for whi ch heavy wipe usage is likely. For example, MSW landfills located in Detroit, M ichigan, should be evaluated to evaluate risk for the auto industry wipes.

Response : This concern was addressed under the 2009 analysis by evaluating air exposures based on national

- level air dispersion modeling using surface and upper air meteorological data obtained from a dataset of 57 representative meteorological regions. These representative meteorological regions were then cross

- referenced with the EPACMTP climate regions to develop national

- level data sets used as inputs the landfill and groundwater models

. The air dispersion modeling is described in section 3.2 of the 2009 risk document (U.S. EPA, 2009).

2.3 .7 Soil C haracteristics (comment theme 15)

Comment: Comments were received on the u se of national averaged soil data characteristics without any consideration of more complex geologies. It was noted that the 2003 assessment assumed favorable geology based on a nati onal averaged soil composition designated as “ silt loam ” with properties assigned

.
Response : Under the 2009 assessment, this comment was addressed under the implemented national

- level probabilistic approach. Under this approach, databases developed to supp ort the EPACMTP groundwater model were used as the primary source for the correlated environmental parameters including soil type as well as other parameters such as aquifer type, climate center, and aquifer temperature

. T he EPACMTP and supporting database s have been used in at least eight risk analyses thatResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

16 have been through a combination of peer and SAB reviews (e.g., the Dyes and Pigments listing determination , EPA, 200 3 b ). Thus, we used these data with a high level of confidence that the methods used to collect and develop this information were consistent with Agency guidance and best practices with respect to probabilistic risk analysis. See section 3.3.2 of the 2009 risk document (U.S. EPA, 2009) on model inputs for details on soil and other subsurface data were used.

2.3 .8 Biodegradation (comment theme 16)

Comment: Comments were received that stated that t he assumption of degradation applied in the 2003 analysis understates risk by as much as a factor of 7. The a ssessment assumes degradation of solvent contaminants occurs as part of the parti tioning model of the landfill. However, the risk r eport notes that this may not be an appropriate assumption.

Response : EPA finds that degradation should be considered as part of the landfill modeling. In the revise d risk analysis presented in the 2009 NODA , b iodegradation within the newly developed LFCR model was accounted for using a single, most conservative available value for the biodegradation rate. EPA finds that this approach reflects the degradation process that occurs and is appropriately conservative.

2.3 .9 Peer Review Comments (comment theme 17)

Comment: Even though EPA had noted that they were deferring the issues identified during peer review until the final risk assessment was performed

, public comments were received noting the peer review comments had not been addressed. The below list highlights key technical issues noted by the peer reviewers

.



###  Groundwater transport was understated.



###  Inadequate waste stream characterization..



###  Tetrachloroethylene was no t evaluated.



###  Applied parameter values do not meet the requirement for a “ high end ” exposure scenario important to making regulatory decisions.



###  Many additional transport pathways exist and would increase risk.



###  Other types of receptors must be evaluated, inc luded a worker at the landfill.



###  Advective transport of air contaminants must be addressed.



###  Degradation, if assumed, must also consider risks from toxic degradation products, such as vinyl chloride.



###  Other factors besides climate and geology and landfill siz e need to be considered in the risk model.



###  The use of generic DAF ’ s is inappropriate.



###  No prediction of upset conditions due to unusual concentrations at a particular location in the landfill, or unusual preferential transport conditions (e.g. macropores i n the landfill or surrounding soils).



###  No consideration of NAPL effects, which could underestimate risk substantially both for the air pathway and the groundwater pathway.



###  Partitioning methodology treats other MSW waste in the unit as if it were a soil, whi ch is clearly

erroneous.



###  Too much information is based on “ verbal ” discussion or limited documentation making much of the data suspect and the risk conclusions questionable.



###  More comparison to actual cases is needed to validate the risk conclusions.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

17 Respon se: As discussed throughout this document, EPA completely revised the risk analysis and presented the analysis for comment in the 2009 NODA. T hese peer comments on the original risk screening analysis from 2003 proposal have essentially been addressed in t he 2009 revised risk analysis either through the development of the new LFCR model, national

- level datasets, or through the implementation of the probabilistic national

- level modeling approaches used to develop the RB

- MLL and ELLRs. EPA presented the revis ed risk analysis for peer review and has responded to the peer review comments on the revised analysis. See the docket for responses to peer review comments on the 2009 revised risk analysis (ELLR calculations

-- EPA

- HQ

- RCRA

- 2003

- 0004

- 0432 ; RB

- MLL calculat ions

-- EPA

- HQ

- RCRA

- 2003

- 0004

- 0433 ). EPA has also responded to public comments on the 2009 revised risk analysis; see the docket for Response to Comments on the Solvent Contaminated Wipes 2009 Risk Analysis: Risk

- Based Mass Loading Limits

.
In response to s ome of the specific peer review comments on the risk screening analysis mentioned by the commenter, EPA notes that the 2009 revised risk analysis addresses most of these concerns in the revised model ing (RTI, 2009). The revised analysis inc l u d ed:

• modeling for tetrachloroethylene ;

• “high

- end” risk results, i.e., EPA 90th percentile ELLR and RB

- MLL values ;

• advective flow of gas within the landfill using the new landfill model (LFCR) ;

• modeling of multiple pathways, including inhalation exposure from air releas es and exposure from groundwater releases through drinking water ingestion, showering, and dermal absorption;

• modeling of the fate and transport of the specific solvent chemicals (not generic DAFs).

Regarding predictions at particular locations, the 2009 revised risk assessment used a national

level, probabilistic modeling approach. The modeling was not designed to attempt to assess site specific factors. However, the data distributions used represented a wide range of possible conditions across the country. EPA finds that this is a conservative approach, especially in conjunction with use of the 90th percentile results for our final evaluation.

Concerning degradation products, the model used in the revised risk analysis does not simulate the formati on of daughter products from the degradation of chemical constituents in the landfill. However, any degradation products will themselves be subject to degradation, making any assessment of the practical effect of this extremely difficult to quantify. In th e case of vinyl chloride, we note that this chemical is a gas at room temperature and is likely to volatilize from the landfill rather readily. Given that the revised risk analysis showed that the high

- end (90th percentile) risk pathway of most concern was release to groundwater, it seems unlikely that air risks from formation of vinyl chloride would present higher risks than the groundwater risks evaluated in the revised analysis.

The Agency finds the formation of NAPL (non

- aqueous phase liquids) from th e disposal of solvent

- contaminated wipes to be highly unlikely. As a condition for the exclusion, the final rule requires that there be no free liquids in containers used for shipment and disposal. Also, the regulations for municipal solid waste landfills restrict the acceptance of any wastes with free liquids. Furthermore, the levels of solvents in the wipes are unlikely to be sufficient to promote formation of a non

- aqueous phase, especially considering the properties of the solvents. For example, most of the solvents are relatively water soluble and volatile, properties that make formation of a separate NAPL layer unlikely.

To address concerns related to the use of limited documentation for waste characterization and solvent loadings, the revised risk an alysis included a thorough analysis and development of representative ELLRs using the best available data gathered from a variety of sources. The analysis using a Monte CarloResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

18 approach designed to account for uncertainty and variability in the input paramet ers. EPA ’s revised methodology for estimating solvent loadings is described in Landfill Loading Calculations for Disposed Solvent

- Contaminated Wipes and Laundry Sludge Managed in Municipal Landfill (U.S. EPA, 2008) and the updated version of the document i n the docket for the final rule Landfill Loadings Calculations for Solvent

- Contaminated Wipes , January 2012.

In response to the comment that m ore compa rison to actual cases is needed, as noted above, the revised analysis did not attempt to model particula r locations . Rather, the 2009 revised risk analysis used a national

- level, probabilistic modeling approach. The modeling was not designed to attempt to assess site specific factors. There are significant uncertainties concerning how exposure and environmen tal assumptions will change over time. However, the fate and transport model used ( EPACMTP , and its predecessors )

, have been verified extensively at each of the developmental stages. The model has been verified, in numerous cases, by comparing the simulati on results against both analytical and numerical solutions. Additionally, EPACMTP and its predecessors have been validated using actual site data from four different sites. The relevant verification and validation history is discussed in detail in Appendix D of the EPACMTP Technical Background Document (U.S. EPA, 2003c). See the discussion on the model in section 4.2.2.3 of the risk documentation for the 2009 analysis ( U.S. EPA, 2009 ). EPA finds that the modeling approach used in the 2009 revised risk asses sment (a national

- level, probabilistic modeling approach), is appropriate.

See responses in this document regarding other pathways (section section 2.3.4) and responses to comments on potential worker exposure (section 2.5 ).

2.3.10 Solvent Impact on Line rs (comment theme 18 )

Comment: In response to the 2003 screening approach, comments were received on the unlined landfill scenario and recommended that EPA should consider the risk of wipe disposal on lined landfills and the potential for solvent impacts o n liner integrity.

Response: EPA recognizes that there are uncertainties associated with modeling the fate and transport of the chemicals in the environment. To address uncertainties highlighted by comments received in response to the 2003 risk screening analysis , EPA revised the analysis and developed a landfill coupled reactor (LFCR) model to simulate the dominant release mechanisms from a landfill, including vapor diffusion, advection, and leaching. The revised analysis also considered liner leakage ra tes that are based on measured, empirical data (Tetra Tech , 2001 ) that reflect existing conditions in landfills. In addition,

t he lan dfill source model accounts for liner leakage by 

### sorption to the geomembrane surface and diffusion through the geomembrane. As a result, the approach used in the revised risk analysis provides a reasonable representation of anticipated behaviors and supports the development of protective RB

MLL. G iven the low expected concentrations resulting from the application of the RB

- MLL s, it is unlikely that liner impacts will be significant. Th e most commonly used plastic for landfill liners, HDPE, has excellent resistance to most chemicals, particularly at low concentrations typically present in lan dfills. While it is true that high co ncentrations of some solvents can lead to swelling and decre ased integrity of some plastics, solvent concentrations are much lower i n a landfill setting than levels known to lead to such effects. As an EPA

- sponsored stud y indicate s , the published leachate chemistry data show that leachate from municipal solid waste landfills contains trace concentrations of synthetic organic chemicals (see Appendix E to Assessment and Recommendations for Improving the Performance of Waste Containment Systems, EPA/600/R

- 02/099 , December 2002).Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

19 

### 2.4 **Sufficiency of Data and Model** 

2.4 .1 Laundry Sludge (comment theme 19 )

Comment: To ensure th a t land disposal of laundry sludge is appropriate in all circum stanc es , c omment er s recommended that sufficien t data be used in the risk anal ysis to ac c ount for laundry variability (e.g., variations due to customer mix and specific types of items being processed)

. This type of variability can result in differences in consti tuents and concentrations. Of particular concern is the discussion in the preamble where EPA notes that the data used to analyze potential risks associ at ed with the disposal of laundry sludge consisted of “ a very limited number of wastewater concentrations collected from industrial laundries by the Office of Water as part of their effluent guidelines development process [68 FR65609]. ”

Response: This comment was addressed under the r evised analysis using a two

- phased probabilistic modeling approached

. To add ress variability in disposal environments, probabilistic national

- level modeling was performed to develop RB

- M L Ls using a mass loading rate approach (i.e., kg per year)

. These RB

- MLLs were then compared to estimated landfill loading rates (ELLRs). EPA

c omp letely revised the landfill loading calculations and presented our new analysis in the October 2009 NODA. The ELLRs were estimated as described in detail in the Landfill Loading Calculations for Disposed Solvent

- Contaminated Wipes and Laundry Sludge Manage d in Municipal Landfills (U.S. EPA, 2008)

. These rates represent the annual quantities of solvents remaining in wipes and laundry sludge when disposed in landfills within the United States. The ELLRs were developed using the best available data gathered fr om a variety of sources using conservative assumptions and a Monte Carlo approach designed to account for uncertainty and variability in the input parameters. For response to comments specific to the ELLR calculations, s ee the docket for Response to Commen ts on the 2003 Proposal on the Landfill Loadings Calculations for Solvent

- Contaminated Wipes

.

2.4.2 Use of Delisting Risk Assessment Software (DRAS) (comment theme 20 )

Comment: A commenter recommended that the EP A use the Delisting Risk Assessment Software (DRAS) as a comparison to the EPA’s screening analysis. It was noted that w hen DRAS is used to evaluate risk associated with the disposal of solvent

- contaminated industrial wipes, the outcome appears to be inconsiste nt with the conclusions of EPA’s risk s creening analysis.

Response: The DRAS model was designed to evaluate delisting petitions submitted under 40 CFR 260.22 to determine the potential risks arising from land disposal of a specific wastestream. Thus, the delisting process uses characterization s and volumes of waste generated by a particular generator. Rather than performing additional modeling with the DRAS delisting model, EPA developed the revised, robust risk analysis using models that reflect conditions at landfills nationally and updated e stimates of the quantity of solvents on wipes and in laundry sludge. The revised risk analysis is included in the docket for the final rule. The revised risk analysis used a state

- of the art landfill model, national

- level datasets, and a probabilistic nati onal

- level modeling approach to develop the Risk

- Based Mass Loading Limits (RB

- MLL) and Estimated Landfill Loading Rates ELLRs. The Agency believes that the revised risk analysis is a more up

- to

- date and comprehensive evaluation of risk and is more appropr iate for a national

level listing decision compared to the DRAS model. The DRAS model uses leaching data (TCLP) as input for the model. The revised risk analysis uses a new landfill model (LFCR) rather than TCLP leachate data for modeling solvent releases, which presents several advantages. EPA needed to perform a comprehensive national

- level assessment and the limited TCLP data available were not adequate for that purpose. The RB

- MLL methodology allowed EPA to capture a broad variety of conditions needed t o back

- calculate acceptable levels of solvents for a national rule. In addition, the model allowed EPA to consider the potential risk for many solvent chemicals based on their properties and transport characteristics, regardless of whether empirical releas e data such as TCLP were available. Finally, t heResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

20 revised risk analysis modeled disposal in a composite

- lined landfill, an option not included in the DRAS model. EPA presented the revised risk analysis for peer review and has responded to the peer review

co mments. EPA has also responded to public comments on the revised risk analysis presented in the 2009 NODA; see the docket for Response to Comments on the Solvent Contaminated Wipes 2009 Risk Analysis: Risk

- Based Mass Loading Limits

.



### 2.5 **Potential Exposures before Landfilling** 

2.5 .1 Launder ing Operations (comment theme 21 )

Comment: Comments were received that pointed out that the EPA has not considered exposures resulting from wipes and laundering processes, other than to evaluate sludge and wipe disposal in a MSW landfill. The following lists the exposure pathways recommended by commenters for evaluation:



###  Worker exposure at both the laundering facility and the P ublicly O wned T reatment W orks (POTW) receiving contaminated groundwater.



###  Fate and transport of haz ardous constituents not treated at the POTW that pass through to the water discharge and impact receiving water bodies.



###  Air emission pathways from the laundering process, and impacts on nearby residences.



###  R unoff issues and fire potential resulting from the storage and accumulation of wipes.

Response: The purpose of the screening analysis was to characterize the potential risk from the disposal of solvent

- contaminated wi pes and laundry sludge in MSW landfills . Occupational exposures, such as exposures result ing from the partitioning of solvents to air and wastewater during laundering operations, were not considered as part of the analysis. With regard to exposures to solvents during laundering operations, EPA assume s that workers are appropriately protected b y regulation and guidance provide by the U.S. Labor Department's Occupational Safety and Health Administration (OSHA). For example, worker exposures to an airborne contaminants are limited based on 1910.1000 Tables Z

- 1 and Z

- 2 ( http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table= STANDARDS&p_id=9992 and ht tp://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table= STANDARDS&p_id=9993 ). In addition, the final rule establishes a closed container standard that addresses fugitive air emissions from the solvent

- contaminated wipes , which will protect laundry em ployees. The final container standard applies to accumulation and storage at the generating facility, transportation either on

- site or off

- site, and, finally, storage and management at the handling facility, such as a laundry.

Concerning exposure to reside nts living in close proximity to laundering /dry cleaning facilities,
g iven the range of exposures captured by the modeling scenarios in the revised risk analysis presented in the October 2009 NODA, and the fact that ambient air exposures were not significa nt, any ambient air impacts from laundering /dry cleaning operations should be less significant than those considered under our landfill disposal scenario. T he revised risk analysis assumed that ambient air exposure could occur as close as 25 meters from th e landfill , a fairly conservative assumption

. Despite this, none of the 90 th percentile RB

- MLLs were based on ambient air exposures. I ndoor air exposures resulting from showering with contaminated gr oundwater and groundwater ingestion were found to be the key exposures considered, and these risks drove the analysis.

Furthermore, in response to comments from the peer review o f the landfill model used in the 2009 risk analysis, EPA considered what the mass loading rates would be if all of the leachate mass

v olatilized and the air pathway was the only pathway of concern

. The results from this effort are presented in Table 4

- 8 in the revised risk analysis document ( U.S. EPA, 2009 )

. This table presents the mass loading rates associated with the greatest estimate d risk for the air and groundwater pathways, respectively, at the 90 th percentile of the risk distribution. The table also includes an estimate of the mass loading rateResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

21 associated with the air pathway if all leachate mass volatilized. In short, t his analys is determined that, even i f all of the solvent mass from landfill leachate was released into the air (i.e., no transport to groundwater occurred) , the resulting mass loading limit for the solvents would not change significantly (see Section 4.2.2.1, U.S. E PA, 2009)

With regard to partitioning of solvents to wastewater and sludges, EPA’s Office of Water regulates wastewater discharges through the National Pollutant Discharge Elimination System (NPDES). The NPDES permit program controls water pollution by reg ulating point sources that discharge pollutants into waters of the US (http://cfpub.epa.gov/npdes/). Also, local POTW pretreatment standards may apply to many laundries. Therefore, risks associated with these discharges are currently managed by the EPA. Si milarly, risks associated with solvents that partition and persist in municipal sewage sludge are also managed by EPA’s Office of Water under the Clean Water Act (referred to as the 503b standards), which routinely evaluate s the potential risks associated with pollutants in sludge, and established risk

- based safe levels for selected pollutants based on the predicted risk to human health and the environment ( http://water.epa. gov/scitech/wastetech/biosolids/ biosolids_index.cfm ).

Lastly, r unoff issues associated with temporary storage practices were not evaluated as part of the assessment given that runoff controls are a legal requirement of the EPA’s National Pollutant Disch arge Elimination System (NPDES) under the Clean Water Act. Most states are authorized to implement the NPDES storm water program ( http://cfpub.epa.gov/npdes/stormwater/authorizati onstatus.cfm and http://cfpub1.epa.gov/npdes/stormwater/swbasicinfo.cfm ) . The NPDES regulations establish best management practices (BMPs) for stormwater and runoff pollution control practices designed to reduce the pollutants contained in discharges to the storm drain system and/or receiving waters. Based on existing regulations issued to control stormwater runoff, EPA assumed that BMPs would reduce exposure pathways associated with r unoff to levels well below concern. In addition, the final rule establishes a closed container standard that should address potential releases during storage.



### 2. **6 Not**  **Specific to Screening Assessment** 

This section identifies other technical issues noted by commenters that were not specific to the 2003 risk screening analysis.

2.6.1 Combustion of Wipes (comment theme 22)

Comment: In support of the 2003 proposed rule, combustion of contaminated wipes was considered and evaluated as a ma nagement option. EPA pr oposed to conditionally exclude from the definition of hazardous waste solvent

- contaminated disposable wipes that are sent to a municipal waste combustor (MWC) or other combustion facility. As a result, comment s were received on this management practice.

O ne commenter stated that the MWC analysis assumes 99.99% destruction efficiency ; h owever , this is the minimum efficiency for hazardous waste combustors, and is not necessarily the case with MWCs. The commenter noted that MWCs are not required to demonstrat e destruction efficiency and can operate at significantly lower combustion temperatures than hazardous waste incinerators. The

commenter stated that the MACT standards for MWCs allow higher levels of dioxin emissions than HWCs, reflecting their poorer oper ating conditions and lower destruction efficiency. C ommenter s suggested that wipe s contaminat ed with chlorinated F001 and F002 listed solvents may pose a significant hazard for the generation of dioxin emissions from combustors and/or contamination of comb uster residues.

Commenters also stated that the solvent

- contaminated wipes could pose a risk to the environment, either through volatilization or release of free liquids, or potential fire. Commenters urged EPA to specifyResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

22 some minimum standards for managem ent of solvent

- contaminated wipes to be burned in combustors to address risk from fugitive emissions during the storage and processing of these wipes prior to and during combustion.

Response: In support of the November 2003 proposed rule, the Agency anal yzed the risks posed from combustion of disposable wipes in municipal waste combustors. Based on this information, EPA made the conservative estimate that 99.99 percent of the incoming contaminant would be destroyed, with the remainder ending up in the ash (68 FR 65609). T hese combustors are easily capable of destroying the solvent, as described in Section IV.F.11 of the Technical Background Document (68 FR 65602). EPA went on to explain that EPA has promulgated revised air emission standard requirements un der the New Source Performance Standards for municipal waste combustors and commercial and industrial solid waste incinerators, which provide a level of protection comparable to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for haza rdous waste incinerators (68 FR 65602).

The New Source Performance Standards, which are promulgated under section 129 of the CAA, already require that municipal waste combustors and other solid waste combustion facilities comply with numerical emission limitations and performance standards that address emissions of dioxin and furans, as well as other air pollutants, such as mercury, particulate matter, sulfur dioxide, nitrogen oxides, semi

volatile metals, lead, cadmium, hydrogen chloride, and carbon mon oxide. To eliminate confusion regarding how the New Source Performance Standards apply to municipal waste combustors and other solid waste combustion facilities, we are clarifying in the regulatory language that we are allowing disposable wipes that meet t he conditions of today’s rule to be sent to municipal waste combustors and other combustion facilities that are regulated under the New Source Performance Standards in section 129 of the CAA. Generators may also continue to send solvent

- contaminated wipes to a hazardous waste combustor regulated under 40 CFR parts 264 or 265, or a hazardous waste boiler and industrial furnace regulated under 40 CFR part 266 subpart H which also control for dioxin and furan emissions.

EPA shares some of the commenters’ conc ern s about the management of solvent

- contaminated wipes prior to combustion

. EPA has addressed these concerns in the final rule. Specifically solvent

contaminated wipes must not contain free liquids when transported to a municipal waste combustor or other combustion facility. EPA has clarified this standard by defining “no free liquids” using the Paint Filter Liquids Test. The use of this test enables proper implementation of the “no free liquids” condition and, combined with today’s requirement that genera tors document how they are meeting this condition, should minimize the possibility of free liquids occurring after the solvent

- contaminated wipes leave the generator. If, however, free liquids do reach the combustor, they must be removed and managed under the applicable hazardous waste regulations. In addition, EPA is requiring that solvent

- contaminated wipes be accumulated, stored, and transported in non

- leaking, closed containers that are labeled as “Excluded Solvent

- Contaminated Wipes.” This container st andard will reduce the potential releases of the solvent to the air or through spills while being managed by the combustor.

2. 6 .2 Consideration of Other C ontaminants Including M etals (comment theme 23)

Comment: The commenters point ed out that the EPA negle cted to consider contamination of wipes from the material s that the solven t removes from the equipment. Testing by a national environmental company indicated that even after processing by a professional laundering service, cloth shop towels contain harmful levels of chemicals including lead and cadmium. However, another comment was received that dismissed this point stating that claims about residual metals in clean, laundered shop towels are entirely without merit.

Response: W e first note that solvent

- con taminated wipes that exhibit a characteristic (except for ignitability) due to constituents other than one of the excluded F

- and corresponding P

- and U

- listedResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

23 solvents (e.g., co

- contaminant metals) are not eligible for the conditional exclusions. Similar ly, wipes contaminated with other listed hazardous wastes would not be eligible for the conditional exclusions. Regarding other possible contaminants, we note that the F

- , P

- , and U

- code solvent listings are based on the toxicity and/or ignitability hazard s presented by the specific solvents included in the listing descriptions. The language in the listings illustrates EPA’s concern with the solvent chemicals. Other potential constituents in the solvent wastes vary widely across industries, such that it wou ld be exceedingly difficult, if not impossible, to categorize and evaluate risks associated with these wastes if we considered all other hazardous constituents and characteristics. Because of the wide variability in constituents that might be present in wa stes from use of the solvents and the identified hazards posed by the solvents, we focused our evaluation on the solvent chemicals themselves. We find that this is the most practical approach to evaluating risks posed by solvent

- contaminated wipes.

Regard ing the potential for laundered towels to contain residual metals, we note that the study cited by the commenter was limited to metal contaminants, not listed solvents. As described in the above paragraph, EPA did not attempt to evaluate possible co

- contam inants on the wipes. The exclusion is for wipes contaminated with F

- listed solvents, not metal

- contaminated wipes. The solvent

- contaminated wipes are still subject to the TC for metals, which would help to address any potential metal residuals in the laund ered wipes. In addition, any residual metals still on the towels after laundering would likely be tightly bound to the fibers, making any transfer from laundered towels to workers unlikely.

2.6 .3 Solvent Wipe s Evaluated Separately (comment theme 24)

Comm ent : Comments were received that the analysis only considered a single solvent constituent from a single source going to a single landfill, and the landfill is assumed to receive wipes from no other sources. Furthermore it was noted that the benchmarks (ri sk criteria) used are inadequate to allow margins for contaminants migrating from other sources in the landfill. The commenter suggested that a non

- cancer hazard index of 1.0 and cancer r isk of 1E

- 05 do not provide a margin for other exposure impacts from other sources, and suggested using lower HQ and cancer risk targets.

Response: The Agency revised its analysis for the October 2009 risk analysis to evaluate multiple facilities disposing of solvent

- contaminated wipes in one landfill. We used a Monte Car lo analysis to represent the variability of generator and landfill locations; the distribution used ranged from 2 to 67 generators per landfill . In addition, the overall loadings assumed were conservative estimates, as described in the Landfill Loading Rep ort (see Landfill Loadings Calculations For Solvent

- Contaminated Wipes ; January 2012 , in the docket for the final rule.)

In using the data from the Biennial Report (BR), for example, the Landfill Loading calculations assumed that all of the waste reporte d in the BR category used was rags and wipes, even though the BR waste form (code W002, c ontaminated debris) includes, for example, certain paper, clothing, rags, wood, empty fiber or plastic containers, glass, piping, or other solids

. 2 Furthermore, the so lvent landfill loading analysis was scaled up to account for other industries that may generate wipes (increasing the number of facilities by about 80%), and also included an additional factor to account for possible growth in the use of disposable wipes i n the future. 3

The calculation of the risk

- based mass loading limits (RB

- MLLs) also used conservative assumptions, e.g., the revised risk analysis presented in the October 2009 NODA used conservative receptor locations for groundwater and ambient air pat hways. In addition, the final risk evaluation was based on the risks for the upper end of the risk distributions, i.e., the 90th percentile in the probabilistic

2 See Biennial Report instructions: http://www.epa.gov/wastes/inforesources/data/br11/br2011rpt.pdf
3 See section 2.3.4 of Landfill Loadings Calculations for Solvent

- Contaminated Wipes ; January 2012 , in the docket for th e final rule.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

24 analyses. Therefore, based on the conservative assumptions used to calculate both the solvent l andfill loadings and RB

- MLLs, the solvents present in the wipes and sludge are unlikely to present a significant risk when disposed in a composite lined landfill.

EPA does not agree with t he commenter ’s suggest ion that EPA use more restrictive target ris k criteria to address other possible sources of the solvents of concern. The Agency believes that the risk criteria used (1E

- 5 cancer risk and HQ less than 1.0 for non

- cancer risk) are appropriate for a listing decision, especially in light of the conserva tive approach used in the overall risk evaluation. However, the risk documentation also presented results for the 1E

- 06 cancer risk level (see Table 5 in F001

- F005 Solvent

- Contaminated Wipes and Laundry Sludge: Comparison of Landfill Loading Calculations a nd Risk

- Based Mass Loading Limits

, January 2012 , in the docket for the final rule). These results show that, even if the Agency used the 1E

- 06 criterion, the carcinogenic solvents would still not present risks above this level, except for trichloroethylene , which is not eligible for the exemption in any case due to non

cancer risks. Furthermore, f or the solvent RB

- MLLs based on non

- cancer risks, all of these solvents (except trichloroethylene) had HQ levels below 0.1, i.e., 10

- fold below the risk criteria u sed. Therefore, even using more restrictive criteria as suggested by the commenter, the disposal of solvent contaminated wipes and sludge in composite lined landfills does not appear to present significant risk.

The Agency also considered other potentia l sources for solvents in municipal landfills. These include: solvent

- contaminated wipes from conditionally exempt small quantity generators (CESQGs), other industrial wastes that may contain the solvent chemicals , and solvents contained in household hazar dous waste. The Agency does not believe these sources would significantly affect the overall risk results as described below.

Under federal regulations, CESQGs may dispose of hazardous waste in MSW landfills subject to §258 regulations (see 40 §CFR 261. 5(g)(3)). However, many states have requirements that are more stringent. For example, based on information collected in 1990, at least 22 states require all or some CESQGs to manage their hazardous waste at a permitted Subtitle C facility, thus prohibitin g disposal at a municipal solid waste facility ( more states may have adopted similar restrictions since 1994 )

. 4 In any case, solvent loadings associated with wipes from CESQG s are expected to be relatively small. For example, Large Quantity Generators gene rate over 1000 kg per month of hazardous waste, compared to CESQGs which cannot gene rate more than 100 kg per month (220 lbs, or about 1⁄2 of a drum) of hazardous waste (which includes all hazardous waste generated at the facility).

Concerning other indust rial wastes, wastes not associated with wipes that arise from solvent use of these chemicals will continue to be regulated under the F

- code listings and the hazardous waste characteristics (Part 261, Subpart C). Non

- solvent related wastes will be regulated under the hazardous waste characteristics, which include the Toxicity Characteristic for many of the more toxic solvents, as well as the ignitability characteristic for the more flammable chemicals. 5 Therefore, beyond the CESQG waste discussed above, ther e are regulations in place to restrict disposal of other sources of the solvent chemicals. Furthermore, e xisting hazardous waste regulations would continue to provide pollution prevention incentives toward decreasing the use of F

- listed solvents in general , because their use would continue to result in the generation of listed hazardous waste, such as spent solvents. In addition, many F

listed constituents are hazardous air pollutants (HAPs). Various NESHAP regulations (e.g., such as those identified in App endix C of the Landfill Loadings Report) provide incentives for a facility to decrease its use of HAP

- containing solvents.

4 Generation and Management of CESQG Waste , July 1994, EPA.
5 Six of the 20 solvent s evaluated in the risk analysis are TC chemicals and 12 are included in the F003 or F005 listing, indicating that they are ignitable.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

25 Regarding household hazardous waste, households are not generally expected to be using industrial hazardous waste solvents. In addi tion, m any communities in the United States offer a variety of options for safely managing household hazardous waste. Some communities have permanent facilit ies that collect hazardous household waste year

- round , including leftover paints, solvents, pestici des, and cleaning and automotive products

. 6 Other communities have special collection days for such wastes. Therefore, these waste collection programs will help divert this hazardous waste stream from MSW landfills.

2.6 .4 Complexity of the Proposed Rule ( comment theme 25)

Comment: Commenters stated that the 2003 proposed rule ha d different conditions for reusable wipes and disposable wipes destined for landfills. There are different regulatory exclusions, different labeling requirements, different limits on solvents and prohibitions. The commenters noted that complexity of the regulation is unnecessary because the risks to human health and the environment are the

same. 

### Response: EPA agrees the risks from release of solvent from wipes are the same for bot h reusable and disposable wipes, thus it makes sense to apply the same conditions during accumulation, transportation, and management of both types of wipes. The conditions in the final rule ensure that the solvent

- contaminated wipes are being managed appr opriately, regardless of whether they are being laundered or disposed. Furthermore, by finalizing conditions that are as similar as possible for both exclusions, EPA has reduced the burden of compliance with the rule, especially for facilities that use bot h types of wipes.

2.6 .5 Groundwater Monitoring and C orrective Action C ontrols (comment theme 26 )

Comment : Commenters stated that the proposed rule gave no consideration to groundwater monitoring and corrective action controls, even though all MSWLFs and 4 0 C.F.R. Part 257, Subpart B landfills operating today are required to have such controls. The commenter noted that EPA must take these regulatory conditions into account in determining whether disposable wipes disposed of in such units are properly classi fied as hazardous waste. See, e.g., 40 C.F.R. § 261.11(a)(3)(x) (consideration of the impact of other regulatory programs in determinations of whether solid waste should be identified and characterized as listed hazardous waste); Dithiocarbamate Task Force v. EPA, 98 F.3d 1394 (D.C. Cir. 1996) (determination of whether wastes pose a substantial hazard to human health or the environment when mismanaged requires consideration of all factors in 40 C.F.R. § 261.11(a)(3)).

Response: EPA disagrees with the commen ter’s assumption that, in an unlined landfill scenario, comprehensive monitoring is being done to assess potential impacts to groundwater, and that such monitoring would prevent potential risk. While monitoring is required for many landfills, there are

exc eptions to this requirement (e.g., for smaller landfills, as defined in § 258.1(f)(1)). Furthermore, the commenter is assuming that groundwater monitoring would identify landfill releases in a timely fashion in all cases, which is not certain.

In any case , protectiveness should not rely on groundwater monitoring to protect nearby residents from potential exposures. Rather, our risk analysis seeks to estimate risks to highly exposed individuals that rely on groundwater sources near landfills. If we rely on well monitoring, then groundwater releases might not be detected until aquifers have been contaminated. That approach would be inconsistent with the preventive intent of RCRA to prospectively avoid releases into the environment that may threaten human heal th and the environment. Therefore, relying on monitoring is not appropriate

6 For example, see the p rograms in Minnesota at http://www.pca.state.mn.us/index.php/living

- green/living

- green

citizen/household

- hazardous

- waste.html and New York a t http://www.dec.ny.gov/chemical/8778.html

.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

26 in our risk analysis. Finally, EPA has considered the impact of other regulatory programs in evaluating wastes from solvent

- contaminated wipes. We considered the regulatory program s in place for municipal landfills and municipal waste combustors. The final exclusion is conditioned upon disposal of the spent wipes in landfills subject to regulation under 40 CFR 258 and combustors that are regulated under section 129 of the CAA

.

2.6 .6 Banning Based on Toxicity Characteristics (TC) (comment theme 27)

Comment: In the proposed 2003 rule, EPA proposed that industrial wipes contaminated with the specified F

- or U

- listed solvents in Table 5 (Table 4 in the preamble to the 2003 proposed rule) or that are characteristically hazardous for other hazardous constituents, such as metals, cannot be disposed in municipal or other non

- hazardous waste landfills. As further discussed in the proposed rule, n ine of the solvents in Table 5 are characteristi cally toxic (TC), as defined in 40 CFR 261.24. Of these nin e, six (as noted by an asterisk : ‘‘*’’) were ineligible for disposal in a municipal or other non

- hazardous waste landfill because they me t the toxicity characteristic, not because of the results of EPA ’ s risk screening analysis. The remaining five solvents ( three of which are also characteristically toxic ) in Table 5 were restricted from disposal in municipal or other non

- hazardous waste landfills because the 2003 risk screening analysis indicated t hat they may pose an unacceptable risk to human health and the environment when disposed of at levels lower than the five

- gram condition. [68FR65597

- 68FR65598]

Table 5. 2003 Proposed Rule: Listed Solvents Not Allowed in Municipal Landfills

Benzene* 2

- Nit ropropane
Carbon tetrachloride* Nitrobenzene

Chlorobenzene* Pyridine Cresols (o,m,p)* Tetrachloroethylene* Methyl ethyl ketone (MEK) Methylene chloride Trichloroethylene *

In response to this proposal, comment er s expressed concern over the inability to achieve and verify a zero concentration of these 11 solvents given the potential for trace contaminants or slight cross

contamination of materials

. Instead of banning these solvents entirely, it was recommended that the EPA clearly state in the final ru le language that the toxic characteristic concentrations, as found in Table 1 of 40 CFR 261.24 for each of the solvents listed in this table, should be considered the de minimis level.

In addition, it was noted that EPA has no statutory authority to prohi bit non

- hazardous waste landfill disposal of wipes containing the solvents for which the EPA ’ s own risk screening analysis demonstrated no substantial hazard from landfilling. Furthermore, it was stated that the EPA ’ s use of the Toxicity Characteristic ( “ T C ” ) to ban the landfilling of certain additional solvents is unwarranted for several reasons:

1. TC modeling makes assumptions and uses parameters that are unsuitable for purposes of this rulemaking;
2. It is i nappropriate and illogical to apply the antici pated results of a TC hazardous waste test designed for a wide universe of wastes in lieu of the risk screening analysis
3. Banning wipes containing any percentage of solvent is not appropriate given that certain wipes will contain insufficient amounts of these solvents to exhibit the TC.

Response: EPA agrees with those commenters who argued that the TC criteria should not be used to prohibit solvent

- contaminated wipes from being landfilled as a non

- hazardous waste and has decided to use the results of th e final risk analysis rather than apply the TC regulations to determineResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

27 whether solvent

- contaminated wipes can be disposed as solid wastes in municipal solid waste landfills ( MSWLFs )

. Therefore, wipes contaminated with benzene; chlorobenzene; o

- ,m

- ,p

- creos ols; methyl ethyl ketone; and/or tetrachloroethylene are eligible for the conditional exclusion for disposable wipes provided they meet the conditions of the exclusion. 7 The Agency undertook a comprehensive risk analysis to estimate the potential risk from disposal of solvent

- contaminated wipes and laundry sludge in MSWLFs. This revised risk analysis was subjected to external peer review and presented for public comment in the 2009 NODA. In support of this analysis, EPA: (1) collected and reviewed informati on (e.g., current industry practices, state programs, landfill loadings) from a wide variety of sources (site visits, data collected by EPA for RCRA and other regulatory programs, public comments, and other available information); (2) used probabilistic me thods to characterize the variability and uncertainty associated with the risk modeling; (3) developed and used a state

- of

- the

- art landfill model and examined the exposure pathways that pose the greatest potential risk; (4) included updated information for various input parameters, when such information was provided in the comments; and (5) recalculated the potential risks by using the most up

- to

- date human health toxicity benchmarks made available after the October 2009 NODA was published.

The revised ris k analysis presented in the October 2009 NODA included a variety of conservative assumptions to ensure that potential risks from landfill disposal were assessed protectively. Furthermore, our evaluation was based on the risks at the upper end of the risk d istributions, i.e., the 90th percentile in the probabilistic analyses. Therefore, we are confident that the solvents present in the wipes and sludge would not present a significant risk. The 2012 final risk analysis represents a comprehensive characterizat ion of the risk posed by these solvent

- contaminated wipes and, therefore, EPA concludes that this is appropriate information to use in determining whether solvent

- contaminated wipes should be excluded from the definition of hazardous waste.

The 2012 risk analysis for the six solvents that are also TC chemicals (benzene, chlorobenzene, cresols, methyl ethyl ketone, tetrachloroethylene, and trichloroethylene) indicated that five of the chemicals have risks well below the target criteria used. 8 The one solve nt that presents risks above the criteria is trichloroethylene, which is therefore ineligible for the conditional exclusion for disposable wipes being promulgated today. In addition, the exclusion only applies to disposable wipes; other industrial wastes, including solvent wastes not associated with wipes, will continue to be regulated as listed or characteristic hazardous waste, as applicable. Therefore, there are regulations in place to restrict disposal of solvent chemicals from other sources in municipa l landfills.

2. 6 .7 Lifecycle Analysis and Recycling (comment theme 28)

Comment: The commenter references a Lockheed study that looked at the raw material requirements and pollutant emissions associated with each type of wipe for its entire life cycle, fr om manufacture through usage a nd to the ultimate disposition. It is noted that t he results of the study

account ed for multiple use cycles for reusable towels . The report stated that reusable shop towels use s much less water and energy , and generate less so lid waste when compared to an equivalent amount of disposable paper towels.

C omments were also received that expressed concern that the proposed rule will not promote recycling of solvents and does not adequately support improved solvent handling practices by gener ators

7 However, wipes contaminated with trichloroethylene would still be subject to the TC because the results of the final risk analysis demonstrate that these wipes present a significant risk when disposed in a composite

- lined landfill. See section III.D. for further discussion.

8 Risks for the five solvents in composite

- lined landfills were below one tenth of the target risk criteria. See the risk results in “ F001

- F005 Solvent

- Contaminated Wipes and Laundry Sludge: Comparison of Landfill Loading Calculations a nd Risk

- Based Mass Loading Limits ” in the docket for the final rule.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

28 and handling facilities. I t was noted that the proposed rule may make it easier for generators and handlers to mismanage solvent

- contaminated industrial wipes and evade regulation by storing contaminated w ipes in lieu of disposal while claim ing intent to dispose at an indefinite future date.

Response: EPA agrees that reusable wipes provide environmental benefits. In the final rule, EPA is exclud ing reusable wipes from the definition of solid waste as the Agency proposed in the November 2003 p roposed rule

. The final rule revises the definition of solid waste to conditionally exclude solvent

contaminated wipes that are cleaned and reused. The purpose of this final rule is to provide a consistent regulatory framework that is appropriate to the le vel of risk posed by solvent

- contaminated wipes in a way that maintains protection of human health and the environment, while reducing overall compliance costs for industry.

Regarding the impact o n recycling, solvent removal and recovery can happen at var ious points in the life cycle of both disposable and reusable wipes. Generators may choose to recover solvent either to reduce virgin solvent use and reduce costs, or to reduce their environmental footprint. In addition, laundries or dry cleaners may recov er solvents from the solvent

- contaminated wipes that arrive at their facilities. Generators of solvent

- contaminated wipes have the potential to capture and recycle spent solvent “free liquids.”

Concerning the potential for mismanagement, the final rule requires certain conditions to be met for r eusable and disposable solvent

- contaminated wipes to be excluded from regulation . Specifically, t he wipes, when accumulated, stored, and transported, must be contained in non

- leaking, closed containers that can co ntain free liquids and the containers must be labeled “Excluded Solvent

- Contaminated Wipes.” The solvent

- contaminated wipes may be accumulated for up to 180 days prior to being sent for cleaning or disposal. At the point of transport for cleaning or dispos al, the solvent

- contaminated wipes and their containers must not contain free liquids. In addition, g enerators must maintain documentation that they are managing excluded solvent

- contaminated wipes as required and keep that documentation at their sites. La stly, the solvent

- contaminated wipes must be managed by facilities (laundries, landfills, and combustors) that are subject to the specified standards in order for the wipes to be eligible for the conditional exclusions under the final rule. Therefore, the Agency finds that these conditions address the potential for mismanagement.

2.6 .8 Concern Over Health of the U.S. Population (comment theme 29)

Comments : One commenter expressed concerns over potential threats posed by landfills, and cited possible impact s on certain subpopulations (children and the elderly). The commenter cited reports suggesting increased incidence of disease in fami lies living near landfill sites and question ed the operational effectiveness of landfill s

. The commenter noted many environ mental advantages of reusable shop towels and urge d EPA to exempt reusable shop towels from being classified as hazardous waste

.
Response : EPA agrees that reusable wipes provide environmental benefits and the final rule conditionally exclud es reusable wi pes from the definition of solid waste

. The Agency is also conditionally excluding disposable solvent

- contaminated wipes

, provided the wipes are: (1) disposed in a municipal solid waste landfill that is regulated under 40 CFR part 258, including § 258.40, or a hazardous waste landfill regulated under 40 CFR parts 264 or 265; or (2) treated in a municipal waste combustor or other combustion facility that is regulated under section 129 of the Clean Air Act (CAA) . Based on the revised risk evaluation the Agenc y finds that, under these conditions, the disposal of solvent

- contaminated wipes in composite

- lined landfills would not present a significant risk for the solvent chemicals included in the exclusion.

T he Agency does not believe the environmental health o r safety risks addressed by this action present a disproportionate risk to children or other subgroups. The commenter did not delineate how aResponse to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

29 conditional exclusion for wipes disposed in landfills would impact subgroups, such as children. In any

case, a s no ted in response to other comments (see section 2.3.2 Exposure Parameters ), health

- based benchmarks (e.g., RfC ) are derived to be protective of all human population including sensitive subgroups for noncancer risks. F or cancer endpoints, adult exposures hav e been shown to drive the risks , thus, the risk criteria used in the Agency’s revised risk evaluation is protective of the general population and subgroups. Also as described previously, t he revised risk analysis includes conservative assumptions to

ensure that potential risks from landfill disposal were assessed protectively (e.g., the revised risk evaluation is based on the risks at the upper end of the risk distributions )

. T he final risk analysis indicates that the risks for the solvent

- contaminated wipe s in composite

- lined landfills are well below the target risk criteria for all of the solvents (except for trichloroethylene, which is not eligible for the exemption).



### 3. References

U.S. EPA (Environ mental Protection Agency). 1997a

. Exposure Factors Handb ook. EPA/600/P

95/002Fa. U.S. EPA, Office of Research and Development, Washington, DC. Available at EFH

1997 Final Report

U.S. EPA (Environ mental Protection Agency). 1997 b

. Guiding Principles for Monte Carlo Analysis

. EPA/630/R

- 97/001. March. Available at http://www.epa.gov/ncea/pdfs/montc arl.pdf

U.S. EPA (Environ mental Protection Agency). 2001 a

. Risk Assessment Guidance for Superfund Volume 3 Part A: Process for Conducting Probabilistic Risk Assessment (RAGS 3A) . EPA 540

- R

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- 002. Available at http://www.epa.gov/oswer/riskassessment/rags3adt/

. December.

U.S. EPA (Environmental Protection Agency). 2001b. Risk Assessment Technical Background Document for the Paint and Coatings Hazardous Waste Listing Determination . Office of S olid Waste, Washington, DC. January. Available in Docket as document number EPA

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U.S. EPA (Environmental Protection Agency). 2003a. EPA ’ s Composite Model for Leachate Migration with Transformation Products (EPACMTP) Parameters/Data B ackground Document. EPA530

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- 003. U.S. EPA, Office of Solid Waste, Washington, DC. Available at http://www.epa.gov/osw/nonhaz/industrial/tools/cmtp/pd_toc

- 2.pdf

U.S. EPA ( Environmental Protection Agency). 2003b. Risk Assessment Technical Background Document for the Dye and Pigment Industry Hazardous Waste Listing Determination . U.S. EPA, Office of Solid Waste, Washington, DC. Available in docket as document number EPA

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- 2003

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.
U.S. EPA (Environmental Protection Agency). 2003c. EPACMTP Technical Background Document . U.S. EPA, Office of Solid Waste, Washington, DC. Available at http://www.epa.g ov/osw/nonhaz/industrial/tools/cmtp/

U.S. EPA (Environmental Protection Agency). 2005. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. EPA/5 3 0/R

- 05/006. U.S. EPA, Office of Solid Waste and Emergency Response. September. Wa shington, DC. Available at http://www.epa.gov/osw/hazard/tsd/td/combust/risk.htm#hhrad

U.S. EPA (Environmental Protection Agency). 2006 a

. Child

- Specific Exposure Factors Handbo ok (External Review Draft) . EPA

- 600/R

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- 096a. U.S. EPA, National Center for Environmental Assessment, Cincinnati, OH. September. Available at http://cfpub.epa.gov/ncea/cfm/recordispl ay.cfm?deid=56747

.Response to Comments on the So lvent Contaminated Wipes 2003 Risk Screening Analysis

30 U.S. EPA (Environmental Protection Agency). 2008. Landfill Loadings Calculations for Disposed Solvent

- Contaminated Wipes and Laundry Sludge Managed in Municipal Landfills . U.S. EPA, Office of Solid Waste and Emergency Response. October. Washington, DC.

U.S. EPA (Environmental Protection Agency). 20 12

. F001

- F005 Solvent

- Contaminated Wipes and Laundry Sludge: Comparison of Landfill Loading Calculations and Risk

- Based Mass Loading Limits . U.S. EPA, Office of Solid Waste and Emergency Respon se. August. Washington, DC.

U.S. EPA (Environmental Protection Agency). 2009. Risk

- Based Mass Loading Limits for Solvents in Disposed Wipes and Laundry Sludges Managed in Municipal Landfills . U.S. EPA, Office of Solid Waste and Emergency Response. October. Washington, DC.