# Comment Summary and Response Document

Hazardous and Solid Waste Management System; Identification and Listing of Special Wastes; Disposal of Coal Combustion Residuals from Electric Utilities ;

Proposed Rule (Docket # EPA - HQ - RCRA - 2009 - 0640) Volume 5: Design Criteria: Liners

December 20141

Background The U.S . Environmental Protection Agency (Agency or EPA) proposed regulations for the management of coal combustion residuals (CCRs) which was published in the Federal Register on June 21, 2010 . This proposal, under the Resource Conservation and Recovery Act (RCRA), addressed the risks from disposal of CCRs generated from the combu stion of coal at electric utilities and from independent power producers . Two regulatory options were proposed . Under the first option, EPA proposed to reverse its August 1993 Bevill Regulatory and May 2000 Bevill Regulatory Determinations regarding CCR and to list CCRs as special wastes subject to hazardous waste regulation s under subtitle C of RCRA when destined for disposal in landfill or surface impoundments . Under the second option, EPA proposed to leave the Bevill determination in place and regulat e the disposal of CCR as non - hazardous solid waste under subtitle D of RCRA by issuing minimum national criteria . Both options would require composite liners, groundwater monitoring, structural stability requirements, corrective action, and closure/post c losure care . EPA also solicited comments on all aspects of both proposed options . The Agency received over 450,000 comments on the proposed rule . The majority of the comments focused on which regulatory path the Agency should pursue for regulating CCRs, i.e., RCRA’s subtitle C or subtitle D . EPA also conducted eight public hearings and took additional comments on the proposed rule . EPA has established three dockets for this regulatory action under Docket ID No. EPA - HQ - RCRA - 2009 - 0640, Docket ID No. EPA - HQ - RCRA - 2011 - 0392, and Docket ID No. EPA - HQ - RCRA - 2012 - 0028 . All documents in these dockets are available at http://www.regulations.gov . Although listed in the index, some information is not publicly availab le, e.g., Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy form. P ublicly available docket materials are available either electronically in http://www.regulations.gov or in hard copy at the OSWER Docket, EPA/DC, WJC West Building, Room 3334, 1301 Constitution Ave., NW, Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566 – 1744, and the telephone number for the OSWER Docket is 202 – 566 – 027 6.2

After reviewing all the comments and additional data received, EPA is promulgating a final rule to regulate the disposal of CCR as solid waste under Subtitle D of RCRA . This rule addresses the risks from structural failures of CCR surface impoundments , groundwater contamination from the improper management of CCR in landfills and surface impoundments and fugitive dust emissions . The Agency has developed seventeen volumes summarizing comments on major topics covered in the proposed rule (see table below) and the Agency’s responses to those comments , as well as a separate volume summarizing comments provided during public hearings . Since EPA is finalizing a rule under subtitle D of RCRA, only those comments submitted on the proposed subti t le C rule that are also applicable to the final rule are addressed in the comment and response documents. Volume Topic 1 General Comments 2 RCRA Subtitle D Regulatory Approach (Legal issues/Self - implementing

Design/Reliance on Certifications by an Independent Professional Engineer/Recordkeeping, State Submissions, Posting to the Internet/Finance Assurance/Alternative Approaches) 3 Scope and Purpose/Effective Dates/Applicability/Off - site Disposal/Definitions 4 Location Restrictions 5 Design Criteria: Liners and Leachate Collection Systems 6 Design Criteria: Structural Integrity 7 Operating Criteria: Endangered species/Surface water/Inspections/Run - on

Run - off 8 Operating Criteria: Air Criteria 9 Groundwater and Corrective Action 10 Closure and Post - Closure Care 11 Additional Comments including Overfills/ Harmonization with ELG. 12 Beneficial Use3

Volume Topic 13 Risk Assessment 14 State Authorities, Programs and Regulations 15 Compendium of Damage Cases 16 Regulatory Impact Analysis (RIA) 17 EPA’s Assessment Program This volume summarize s comments received on the proposed design criteria for liners and leachate collection systems and provides EPA’s responses to those comments. Comments and EPA Responses on the Design Criteria for Liners and Leachate Collection Systems The design criteria proposed in the RCRA subtitle D pr oposal consisted of two primary requirements: (1) a composite liner system for new CCR landfills, existing and new CCR surface impoundments and all lateral expansions; and (2) structural stability requirements for existing and new CCR surface impoundments and all lateral expansions of these units . No design requirements were proposed for existing CCR landfills; rather, EPA proposed that these units could continue to receive CCR s and continue to operate as compliant landfills, without violating the open dumping prohibition . Conversely, EPA proposed that existing CCR surface impoundments, unlike existing CCR landfills, would be required to retrofit with a composite liner system wi thin five years of the effective date of the rule or to close . Proposed Liner Requirements The proposed RCRA subtitle D design standards require d that new CCR landfills , new CCR surface impoundments, and lateral expansions of CCR landfills and CCR surface impoundments be constructed with a composite liner and leachate collection and removal system . In the proposal, EPA defined a composite liner to mean a liner system consisting of two components; the upper component consisting of a minimum 30 - mil flexible membrane liner (FML), and the lower component consist ing of at least a two - foot layer of compacted soil with a hydraulic conductivity of no more than 1×10 −7 cm/sec . FML components consisting of high density polyethylene (HDPE) were required to be at least 60 - mil thick . The FML component4

must be installed in direct and uniform contact with the compacted soil component . Hydraulic conductivity means the rate at which water can move through a permeable medium (i.e., the coefficient of permeability). In addition, EPA solicited comments on a number of issues, including: (1) whether any RCRA subtitle D option should allow facilities to use an alternative design for new CCR disposal units, so long as the owner or operator of the CCR disposal unit could o btain certification from an independent registered professional engineer or hydrologist that the alternative design would ensure that the appropriate concentration values for a set of constituents typical of CCRs will not be exceeded in the uppermost aquif er at the relevant point of compliance; i.e., 150 meters from the unit boundary down gradient from the unit, or the property boundary if the point of compliance (i.e., the monitoring well) is beyond the property boundary; (2) whether, in addition to the fl exibility provided by section 3004(o)(2) of RCRA, the CCR regulations should also provide for alternative liner designs based on, for example, a specific performance standard, such as the performance standard in 40 CFR 258.40(a)(1), or a site specific risk assessment, or a standard that the alternative liner, such as a clay liner, was at least as effective as the composite liner; (3) whether clay liners designed to meet a 1x10 - 7 cm/sec hydraulic conductivity might perform differently in practice than modele d in the risk assessment, including specific data on the hydraulic conductivity of clay liners associated with CCR disposal units; and (4) on the effectiveness of such additives as organosilanes, including any analyses that would reflect long - term performa nce of the additives, as well as the appropriateness of a performance standard that would allow the use of these additives in lieu of composite liners. The Agency received a number of comments advocating the use of alternatives to the proposed composite li ner . Most of these commenters recommended that geosynthetic clay liners be allowed as an alternative to the lower component stating that they have been proven to be an effective alternative to the two - foot layer of compacted soil . Some commenters stated that natural clay is not economically available in many parts of the country so, as an alternative, the CCR landfill owner or operator should have the ability to have a geosynthetic clay liner (GCL) approved as a replacement for the compacted soil componen t of the composite liner system if a demonstration is made that the alternative design meets the performance standard of the prescribed system . Other commenters stated that GCLs alone should be allowed as an5

alternative to the proposed composite liner . T here were also comments opposing the use of alternative liners stating that alternatives have not been proven to be effective . EPA also received comments explaining that the proposed requirement for a leachate collection and removal system in new CCR sur face impoundments was illogical since it would have to be constructed between the lower component (two feet of compacted soil) and upper component (flexible membrane liner) and the proposed rule specifically states that the flexible membrane liner componen t must be installed in direct and uniform contact with the compacted soil component . The inclusion of a leachate collection and removal system between the upper and lower components precludes direct and uniform contact . Placing a leachate collection and removal system between the lower and upper components of a composite liner would also compromise the integrity of the composite liner . These and other comments are discussed in more detail below. 1 . G randfathering of modern existing CCR surface impoundme nts and CCR landfills. Comment: Obviously, the focus of the proposed rules are the older, unlined, existing CCR surface impoundments that were constructed 20 or more years ago absent of today’s environmental rules and construction standards . However, many existing CCR surface impoundments and existing CCR landfills have been permitted and constructed under current environmental rules that have required liners, leachate collection systems, and other modern controls . The liners and leachate collection s ystems in these modern facilities were approved by state regulatory agencies and were deemed protective of human health and the environment . However, in many cases the liner systems, leachate collection systems, or other controls, may not match the specif

ic design criteria in the EPA’s proposed rule . There should be provisions in the EPA’s rules, allowing for the states, when adopting the EPA’s rules, to grandfather modern existing CCR surface impoundments and CCR landfills. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06832 - 26 Organization: SCANA Corporation Commenter Type: Electric Utility Company Comment: G randfathering of existing units encourages prolonging life of aging ponds and landfills . States routinely allow the continued operation of existing landfills and surface impoundments, without requiring the older units to comply with newly - imposed safeguards . In6

the 1999 Report to Congress, EPA estimated that the average age of surface impoundments and landfills was about 40 years . Yet many ponds and landfills are operating for decades longer Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06315 - 26 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Response : The Agency agrees with the commenter that “modern” existing CCR landfills an d surface impoundments should not be subjected to the full suite of requirements in the proposed rule . However, EPA believes that certain existing CCR disposal units can pose risks so, in the final rule we are requiring these units to meet specific requir ements to alleviate these risks . Specifically, the Agency is not subjecting e xisting CCR landfills to the location restrictions for placement above the uppermost aquifer , wetlands , fault areas , and seismic impact zones . Our rationale for this is that a ffected facilities would need to find additional disposal capacity, which would require utilities to procure new real estate for siting a new CCR landfill (which may be a significant distance from a power plant), obtain a new disposal permit for the CCR la ndfill (which can take an extended period of time), and transport significant volumes of CCRs great distances to newly - permitted facilities . EPA believes that a pplying the se location restrictions to existing CCR landfills would cause a significant decreas e in disposal capacity across the country . However, as proposed, EPA is requiring that existing CCR landfills must not be located in an unstable area unless the owner or operator demonstrates within 42 months of the effective date of the rule that recogni zed and generally accepted good engineering practices have been incorporated into the design of the CCR unit to ensure that the integrity of the structural components of the CCR unit will not be disrupted . Existing CCR landfills not meeting this requireme nt must close . Locating disposal units in unstable areas is generally recognized as having the potential to impact the structure of a ny disposal unit negatively and as such, increase the risks to human health or the environment through structural failures or leaching of contaminants into the groundwater . Additionally, existing landfills are not required to close or be retrofitted with a composite (or alternative composite) liner and a leachate collection and removal system . G iven the volume of the material currently managed in CCR landfills, the potential for disruption in CCR disposal capacity if existing CCR landfills were required to retrofit would be significant . However, t he final rule requires that only existing unlined CCR surface impoundmen t that are contaminating7

groundwater above a regulated constituent ’s groundwater protection standard to stop receiving CCR and either retrofit or close, except in limited circumstances . EPA believes that existing unlined CCR surface impoundments should no t be required to close prematurely if they are operating as designed and are complying with all the requirements of the rule, including all groundwater protection standards. The final rule also requires the closure of any CCR landfill or CCR surface impoun dment that cannot meet the applicable performance criteria for location restrictions or structural integrity established in this rule . Finally, those CCR surface impoundments that are no longer receiving CCR as of the effective date of the rule, but still contain water and CCR will be subject to all applicable regulatory requirements , unless the owner or operator of the facility dewaters and installs a final cover system on these inactive units no later than three years from the effective date of the rule. 2 . Liner Design Requirements Applicable to Existing CCR Landfills. a . The Need for Liners and Leachate Collection Systems. Comment: T hese proposed rules are quite detailed and include provisions (such as requiring synthetic liners) that are not necessary in all instances. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06011 - 11 Organization: Public Service Commission (PSC) - State of North Dakota Commenter Type: State Government Comment: EPA is proposing to modify the double liner and leachate collection and removal system requirement by substituting a requirement to install a composite liner and leachate collection and removal system . Tennessee agrees with this approach . This requirement and/or an equivalent requirement is identical to Tennessee ’ s stan dard for landfills and should be required in national standards regulating CCRs. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06298 - 62 Organization: Tennessee Department of Environment and Conservation (TDEC) Commenter Type: State Government Comment: Ecology supports the proposed rule technical requirements that new lateral expansions and new landfills be constructed with a composite liner and leachate collection system .8

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06866 - 6 Organization: Washington State Department of Ecology Commenter Type: State Government Comment: In some regions of the country, the proposed composite liner system simply is not necessary to ensure protection of groundwater. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 8 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06203 - 13 Organization: Arizona Public Service Company (APS) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06308 - 12 Organization: NRG Energy Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06863 - 41 Organization: Avista Corp. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06956 - 13 Organization: Tri - State Generation & Transmission Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08270 - 5 Organization: Cliffs Natural Resources Inc . (Cliffs) Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 21 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09536 - 9 Organization: Tennessee Valley Authority Commenter Type: Electric Utility Company9

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09713 - 11 Organization: Indianapolis Power & Light Company (IPL) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09885 - 27 Organization: Progress Energy, Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment: Wyoming believes that CCR landfills should be afforded the same opportunity to demonstrate that a liner is not ne eded as Subtitle D provides for municipal solid waste landfills in consideration of the fact that municipal waste poses a far greater threat to human health and the environment than CCR. Comment Number: EPA - HQ - RCRA - 2011 - 0392 - 0265 - 12 Organization: Departmen t of Environmental Quality, State of Wyoming Commenter Type: State Government Comment: Before mandating ground water monitoring and liners with regulations, it should be proven that the CCR does contain materials detrimental to human health . The characteristics of the CCR site must be considered before mandating a liner . Numerous sites are likely to have constituents which will absorb, adsorb or chelete harmful constituents from a CCR leachate . If so, the site should require a liner or monitorin g . Volume of leachates should be a consideration . If the volume is low then dispersion into surface or ground water of greater volume is likely to be of low consequence . If so, the site should not be required to have a liner or monitoring. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06113 - 1 Organization: None Given Commenter Type: Private Citizen Comment: I n certain situations, CCRs can be handled in a wet state, with no additional upgrades or impoundment liners . This would be true of applications where existing safeguards and handling practices provide sufficient environmental protection.10

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06129 - 3 Organization: City Utilities of Springfield, MO Commenter Type: Electric Utility Company Comment : T he continued us e of compacted clay liners for Subtitle D standards should be allowed and is adequately protective of human health and the environment . Although a composite liner is required by the existing proposal, Arkansas and Louisiana regulations currently allow for a minimum of a two - foot layer of compacted clay with a hydraulic conductivity of no more than 1×10 - 7 cm/sec and leachate collection to be utilized for CCR disposal units . Entergy supports the continued use of clay liner systems, in conjunction with groundwater monitoring programs to ensure no impacts are noted from the ash disposal units. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06987 - 31 Organization: Entergy Services, Inc. Commenter Type: Electric Utility Company Comment : Clay liner systems should b e an acceptable alternative to the composite liner system for existing facilities. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10732_DEN - 044 - 4 Organization: Platte River Power Authority Commenter Type: Electric Utility Company Comment : We suggest the following conditions for allowing a facility to continue operating without the requirement to install a composite liner: 1 . The facility has a natural clay liner that provides equivalent performance to the proposed composite liner . 2 . U sable groundwater resources do not exist below the facility . 3 . Groundwater monitoring demonstrates the facility is in compliance with appropriate standards . 4 . The containment features of the facility are stable against slope instability, are struct urally sound, and are operated and maintained appropriately . 5 . In some states, e.g., Michigan, an industrial waste such as bottom ash can be shown to be he an “inert” and obtain an exemption from management as a waste . We propose that CCRs also have the ability to be shown to be inert on a case by case basis .11

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08865 - 6 Organization: Geosyntec Consultants Commenter Type: Other Company Comment : CCR surface impoundments operating in accordance with the proposed compo site liner requirements and applicable groundwater monitoring requirements do not need a leachate collection system, as any possible migration of constituents from the unit will be detected by the applicable groundwater monitoring system. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 9 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment: Existing landfills that do not have a liner meeting the requirements specified in the rules or landfills that do not meet the requirements f or landfill siting and design should be capped and hydraulic controls should be installed as needed to minimize movement of hazardous metals . Long - term monitoring should also be required. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06313 - 89 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Comment: The proposed rules require composite liners for impoundments not only under Subtitle C but also for Subtitle D . While the Subtitle C option is rigid with respect to this requirement, the Subtitle D program should not be . The Louisiana solid waste regulatory program required engineered clay liners, having a coefficient of permeability no greater than l x l0 - 7 cm/sec, up until rule modifications of 1993 after which new impoundments were req uired to have either composite liners or alternative liners that provide equivalent groundwater protection . The existing Cleco solid waste units were designed with the required clay liners while the newest one has a composite liner . Groundwater monitorin g over the course of years has shown that there has been no adverse impacts to groundwater from Cleco impoundments . This suggests that under a Subtitle D program, use of engineered clay liners on existing solid waste units offers adequate protection witho ut the extreme and unnecessary expense of excavating material from existing units and installing composite liners . The legislative history of the Bevill Amendment along with statements from the D.C . circuit court indicate that Congress directed EPA to in stall a regulatory program for CCR's that utilizes cost - effective controls and avoids imposition of12

undue regulatory costs on the electric utility industry if at all possible (EDF vs EPA, 852 F.2d 1309, 1315 (D.C . Cir . 1988 ) Considering these directions and the proven performance of engineered clay liners, EPA should not require the installation of composite liners at existing units under a Subtitle D program. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06868 - 7 Organization: Cleco Corporation Commenter Type: El ectric Utility Company Comment: EPA should require the use of a composite liner system as the standard for containment and closure systems . This system has been demonstrated (by EPA) to be the most effective barrier methodology, regardless of the classification of the materials to be contained (hazardous or non - hazardous). Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06552 - 1 Organization: Agru America, Inc . (Agru) Commenter Type: Other Company Comment: EPA should consider this [the Pennsylvania] progra m as a model for effective state programs as it finalizes the Subtitle D regulations . The only substantial modification recommend ed to the Pennsylvania program model is that EPA should mandate a liner retrofit and leachate collection system requirement for existing surface impoundments as proposed in the Subtitle D approach . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09281 - 18 Organization 1 : Exelon Power Commenter Type: Electric Utility Company Response: As discussed in the proposed rule, t he CCR damage cases and EPA’s quantitative groundwater risk assessment clearly show the need for effective liners

– namely composite liners

– to very significantly reduce the probability of adverse effects . Therefore, the final rule requires new CCR landfills, new CCR surface impoundments, and all lateral expansions to be constructed with a composite liner . Similarly, to maintain the integrity of the geomembrane upper component of the composite liner it is essential to control the hydraulic head, i.e . the fluid level above the upper geomembrane component of the composite liner the integrity of the geomembrane . The primary function of a leachate colle ction and removal system13

is to collect and convey leachate out of a unit and to control the depth of leachate above the liner Therefore, for new CCR landfills and lateral expansions, the final rule requires the installation of a leachate collections system to maintain the fluid level above the geomembrane at no more than 12 inches (30 centimeters) . As commenters rightly pointed out, requiring a leachate collection system as proposed for new CCR surface impoundments is counterintuitive and would compromise the integrity of the composite liner . Accordingly, the final rule does not require leachate collection systems for new CCR surface impoundments and lateral exp a nsions. Comment: The final regulations should address specific requirements for design of the leachate collection system, and should specify requirements for adequate quality assurance/ quality control for construction of the liner and leachate collection system. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06866 - 6 Organization: Washington State Department of Ecology Commenter Type: State Government Response: The final rule requires a leachate collection system designed, co nstructed and operated to maintain less than a 12 inch ( 30 - centimeter ) depth of leachate over the composite liner or alternative composite liner . This is the same requirement for leachate collection systems established in the regulations for municipal solid waste landfills at 40 CFR §258 . The Agency has chosen not to speci fy specific requirements for the design and construction of the leachate collection system to provide flexibility for its design and construction based on site specific conditions . Additionally, the final rule requires that the design and construction be certified by a qualified professional engineer . Moreover, EPA has developed recommended guidance for the design of leachate collection systems and construction quality assurance and quality control of liners and leachate collection systems . The recommend ed guidance is available at http://www.epa.gov/epawaste/nonhaz/industrial/guide/pdf/chap7b.pdf . b . Existing CCR Landfills Should be Required to Retrofit to a Composite Liner System . EPA did not propose to require existing CCR landfills to retrofit with a liner because these units presented significantly lower risks than those associated with CCR surface impoundments . The Agency was also concerned that potential disposa l capacity shortfalls could result if existing CCR landfills were required to close, given the volume of the material involved, and was concerned about the potential for significant disruption in energy supplies and distribution if all disposal units neede d to be simultaneously closed . The Agency concluded that14

greater public health concerns existed based on the potential for open dumping of CCRs if all disposal units were forced to close than by the potential risks caused by the continued use of these exi sting unlined landfills, given that the landfills would also be subject to the other rule requirements, including groundwater monitoring and corrective action . The Agency received no information during the comment period to contradict those initial conclu sions . The risks associated with unlined (or clay lined) CCR landfills remain significantly lower than those associated with CCR surface impoundments . U nlined u nits were found to present the greatest risks . Unlined impoundments result in cancer risks ab ove 1 × 10 - 5 for trivalent (3 × 10 - 4 ) and pentavalent (4 × 10 - 5 ) arsenic, as well as noncancer risks above an HQ of 1 for trivalent arsenic (8), molybdenum (4) and thallium (2) . Unlined landfills result in cancer risks above 1 × 10 - 5 for trivalent arsenic (2 × 10 - 5 ), and within the OSWER risk range for pentavalent arsenic (1 × 10 - 6 ). Clay - lined u nits were found to present risks lower than unlined units, but still within the OSWER risk range . Clay - lined impoundments result in cancer risks for trivalent arsenic (7 × 10 - 6 ) . Clay lined landfills also result in cancer risks for trivalent arsenic (1 × 10 - 5 ) . Consequently, the final rule allows existing CCR landfills without composite liners to continue to operate without retrofitting . EPA did not receive specific comments st ating that existing CCR landfills should be retrofitted with composite liners . 3 . Liner Design Requirements Applicable to New CCR Landfills and Lateral Expansions . a . No Technical Requirements Proposed for Leachate Collection Systems . Comment : The final regulations should address specific requirements for design of the leachate collection system, and should specify requirements for adequate quality assurance/quality control for construction of the liner and leachate collection system. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06866 - 6 Organization: Washington State Department of Ecology Commenter Type: State Government Response : EPA is finalizing a rule that requires new CCR landfills and lateral expansions to be constructed with a leachate colle ction and removal system that meets a specific performance standard: that the system is designed and constructed to maintain less than a 30 - cm depth of leachate over the liner . The design of the composite liner and leachate collection and removal system must be prepared by, or under the direction of, and certified by a qualified professional engineer . This requirement provides flexibility for professional engineers to design15

the leachate collection and removal system that are appropriate for site - specifi c conditions and that meet the minimum leachate depth requirement . This approach has been effective in protecting public health and the environment for MSWLFs . The commenter provided no information to suggest that it will not be effective for CCR landfil ls, and the Agency is aware of none . 4 . Liner Design Requirements Applicable to Existing CCR Surface Impoundments . a . Retrofit or Closure of Unlined CCR Surface Impoundments Regardless of Performance . Comment : We have constructed two CCR surface impoundments using high density polyethylene (“HDPE”) synthetic liners where the sub - base component of the composite liner does not meet the proposed requirement for two feet of clay with permeability less than or equal to 1.0 x 10 - 7 cm/sec . These surface impoundments are safe and functioning as designed . However, under the proposed rule, they, along with other “lined” CCR surface impoundments that do not me e t EPA’s definition of “composite liner” would be required to be closed before they reach their max imum storage capacity . EPA must include the D Prime component when it promulgates a RCRA s ubtitle D non - hazardous CCR regulation , such that it does not mandate the closure of CCR surface impoundments simply because they do not meet EPA’s proposed liner de sign standards regardless of how the facility is performing . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06398 - 29 Organization: Duke Energy Commenter Type: Electric Utility Company Response: As discussed in section VIII . B . 7, EPA has concluded that it is not necessary to require existing CCR surface impoundments to retrofit with a composite liner or close until the existing CCR surface impoundment presents an immediate threat to groundwater . Therefore, EPA is allowing CCR surface impoundments t hat are lined with a composite liner, or a clay liner that meets the technical requirements in the rule to continue to operate and receive CCRs, provided the owner or operator of the unit certif ies that the §257.71, Table I contaminants are not migrating f

rom the existing unlined CCR surface impoundment into groundwater at a statistically significant increase over background as determined through a groundwater monitoring program in accordance with §§257.90

– 257.94 . However, if the existing unlined CCR sur face impoundments are found to be leaking , they are subject to the corrective action requirements of today’s rule and must also either retrofit with a composite liner or alternative16

composite liner, or close in accordance with the closure requirements at § 257.100 , except in limited circumstances . The Agency has concluded that this revised approach will still ensure the protection of groundwater resources . b . Technical Requirements Applicable to Existing CCR Surface Impoundments Depending on Closure Dates . Comment: CCR s urface impoundments receiving CCR for treatment or disposal should be regulated from initial design through completion of post - closure monitoring requirements . For existing CCR surface impoundments , there should be two categories; ( 1) CCR surface impoundments to be closed within five years from the effective date of the CCR final r ule, and (2) CCR surface impoundments that will be used more than five years after the effective date of the CCR f

inal r ule. (1) Regulations for existing CCR surface impoundments to be closed within five years of the effective date of the CCR final r ule should include structural analysis with repair/improvements required to meet a dam safety factor of 1.2 . Additional requirements should include quarterly inspections , installation of groundwater monitoring wells, semiannual groundwater monitoring, closure plan, post - closure monitoring and maintenance and financial assurance in an amount sufficient to cap the surface impoundment and to perform environmental investigation and cleanup should the CCR surface impoundment fail or have releases to groundwater and surface water . The CCR surface impoundment owner or operator should be required to submit a statement committing to closure of the CCR surface impoundmen t within five years and acknowledge the responsibility to comply with (2) below should the CCR surface impoundment not be closed on schedule. (2) Regulations for existing CCR surface impoundments to be operated for more than five years after the effective date of the CCR final r ule should include a structural analysis with repair/improvements required to meet a dam safety factor of 1.5 . In addition, t hese surface impoundments should be retrofitted with a synthetic liner to prevent the migration of CCR co ntaminants into ground water and the owner or operator of the CCR surface impoundment should be required to obtain a solid waste processing/disposal permit following the RCRA s ubtitle D public participation process . Additional requirements should inclu de quarterly inspections, installation of groundwater monitoring wells, semi - annual groundwater sampling, annual estimation of remaining life, closure plan with cover , post - closure monitoring and17

maintenance plan and financial assurance sufficient to perf orm environmental investigation and clean up should the CCR surface impoundment fail or release contaminants to groundwater or surface water. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06298 - 30 Organization: Tennessee Department of Environment and Conservation (TDEC) Commenter Type: State Government Response: We disagree with the commenter that CCR surface impoundments that will not be operating and receiving CCRs for more than five years should be subject to fewer requirements than those CCR surface impoundments that will be operating and receiving CCRs from more than 5 years . First, we would note that the Agency does not have the authority to require the owner or operator of the CCR surface impoundment to obtain a solid waste processing/disposal per mit following the RCRA subtitle D public participation process nor impose financial assurance requirements . Thus, the Agency could not require such provisions, even if it wanted to . More importantly, the risks to human health and the environment can be t he same whether the CCR surface impoundment is operating and receiving CCRs for less than or more than five years . Therefore, the Agency has not made this change . However, with that said, the Agency has made a number of modifications to the proposed rule , which we have determined provide greater flexibility for the owner or operator of the CCR surface impoundment, and at the same time are protective . Specifically,  owners or operators of existing CCR surface impoundments that impound CCR, CCR slurry, or liquids to an elevation of five feet or more above the down stream toe of the structure and have a storage volume of 20 acre - feet or more; or impound CCR, CCR slurry, or liquids to an elevation of 20 feet or more above the down stream toe of the structure m ust d emonstrate that the existing CCR surface impoundment meets and will maintain a static structural stability factor of safety of greater than or equal to 1.50 under long - term loading conditions . This requirement has been modified from the proposed rule . EPA proposed this size threshold based on Mine Safety and Health Administration (MSHA) coal slurry pond requirements . However, EPA modified MSHA’s language from 5 feet above the “upstream toe” to 5 feet above the “downstream toe” in order not to captur e incised CCR surface impoundments . Incised CCR surface impoundments do not have embanked portions, and therefore do not present a threat of structural failure .18

 all existing CCR surface impoundments are subject to the groundwater monitoring and correcti ve action requirements in §§257.90 through 257.98, and must conduct weekly inspections and annual inspections that must be certified by a qualified professional engineer .  owners or operator s of existing CCR surface impoundment are required to prepare a written closure plan that explains the method of closure, a description of the final cap, and an estimate of the year in which closure will be completed .  a ll existing CCR surface impoundments are also subject to the post - closure care requirements of §25 7.10 3 of today’s final rule . 5 . Liner Design Requirements Applicable to New CCR Surface Impoundments and Lateral Expansions of Existing and New CCR Surface Impoundments . a . Definition of Composite Liner is Incorrect . Comment: Sec tion 257.71 and 257.72 describes the liner as 'composite' with a leachate collection system between the two liner components . This is a 'double liner system' not a composite liner system . Given the direct and uniform contact provision, the rule description o f composite system needs to be corrected. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 35 & 36 Organization: Kansas Department of Health and Environment Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08226 - 45 Organization: Ohio Environmental Protection Agency Commenter Type: State Government Comment: For new surface impoundments and lateral expansions, revise the requirement for the installation of a leachate collection system between the lower and upper component to installa tion of a leachate collection system above the upper component. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 35 & 36 Organization: Kansas Department of Health and Environment Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09282 - 13 Organization: North Carolina Department of Environment and Natural Resources Commenter Type: State Government19

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 23 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comme nt: The proposed version states "With a composite liner, as defined in paragraph (a)(2) of this section and leachate collection system between the upper and lower components of the composite liner." We believe this should read "With a composite liner, as defin ed in paragraph (a)(2) of this section and leachate collection system placed above/ on top of the composite liner." The composite liner must be in installed in direct and uniform contact and the leachate collection system should be placed on top of and not in the middle of the two 2 parts of the liner. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06819 - 24 Organization: Missouri Department of Natural Resources Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 22 Organization: Virginia Dep artment of Environmental Quality Commenter Type: State Government Response : EPA acknowledges that the proposed requirement for a leachate collection system between the upper and lower components of the composite liner for new surface impoundments and lateral expansions was proposed in error . For the reasons stated in the respon se to similar comments in section c (Composite Liner Integrity) below, the final rule is not requiring a leachate collection system for new CCR surface impoundments and lateral expansions. b . Composite Liner Placement . Comment : Composite liners should n ot be mandated throughout a wet/surface impoundment disposal area . Composite liners are an appropriate requirement beneath the CCR surface impoundment proper or over the CCR surface impoundment basin where a persistent source of water exists, but not bene ath the containment dikes or other impounding embankments where a composite liner represents a weak plane in the foundation of the containment structure and poses stability issues . Rather, with regard to containment dike/impounding embankment areas, the u se of soil and/or other non - geosynthetic seepage barriers in combination with subsurface drains is a better approach for stability, management of seepage and leachate, and2 0

long - term surface and groundwater protection . Mechanisms to promote the passive dew atering of the CCRs, and collect and control seepage and leachate, will yield the greatest dividends for stability and long - term environmental protection . The perfect liner system and watertight bathtub do not exist. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03451 - 5 Organization: Commenter Type: Private Citizen Response: The Agency agrees that a composite liner beneath a CCR surface impoundment containment dike or berm is not appropriate since the liner could create an unstable foundat ion and lead to leakage or the structural failure of the dike or berm . EPA did not intend to require a composite liner beneath the CCR surface impoundment containment dikes or other impounding embankments, but was not clear in the proposed rule . Therefor e, t he A gency is specifying in the final rule design requirements that composite liners are to be installed to encompass the CCR surface impoundment containment dikes or other impounding embankments . c . Composite Line r Integrity Comment: A liner integrity survey should be conducted on the flexible membrane liner (FML) component at an impoundment . This concept could be inserted where the direct and uniform contact provision is brought up . It could be phrased in terms of the FML component being wi thout tears or holes (and maybe even wrinkles when used in landfills) after deployment . It wouldn't hurt to include landfills too, but is critical for the impoundment due to the separation of the FML from the compacted soil liner. Comment Number: EPA - HQ - R CRA - 2009 - 0640 - 08226 - 45 Organization: Ohio Environmental Protection Agency Commenter Type: State Government Response : As stated previously and discussed in detail below, the final rule does not require a leachate collection system between the upper and lower components of the composite liner for CCR surface impoundments . Therefore, there will not be a separation betwee n the geomembrane (FML) component and the compacted soil component of the composite liner . Nevertheless, u pon completion of construction of the CCR landfill , CCR surface impoundment, or any lateral expansion, the owner or operator must obtain a certificat ion from a qualified21

professional engineer that the composite liner (or, if applicable, alternative composite liner) and the leachate collection and removal system has been constructed in accordance with the requirements of the final rule . This certificat ion should assure that the geomembrane component is installed in direct and uniform contact with the compacted soil component. Comment: Earthern embankments often develop cracking . When the embankment cracks, the 2 - ft thick layer of compacted soil would likely also have cracked . At that point, a single 30 - mil HDPE liner becomes the sole line of defense . Suggest considering 2 liners placed on 2 - ft compacted soil and the leachate collection system . Also, “direct and uniform contact with the compacted soi l component” is unrealistic as HDPE installation typically have wrinkles. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09337 - 53 Organization: Arizona Department of Environmental Quality (ADEQ) Commenter Type: State Government Response : The Agency has no experie nce or data that show that a composite liner consisting of two feet of compacted soil with a hydraulic conductivity of 1 x 10 - 7 cm/sec and a single 30 - mil geomembrane in direct and uniform contact with the compacted soil is not an effective liner system . EPA’s risk assessment shows that c omposite liners were the only liner type modeled that effectively reduced risks from all pathways and constituents far below human health and ecological criteria for every sensitivity analysis conducted. Comment: The p roposal requires that existing and new CCR surface impoundments and all lateral expansions of CCR surface impoundments to be constructed with a composite liner system having a leachate collection system between the upper component (flexible membrane liner) and lower component (compacted soil barrier) . However, the regulatory text also requires the two components of the composite liner to be installed in direct and uniform contact with each other . It is not possible to meet both requirements, as the inclus ion of a leachate collection system between the upper and lower components precludes intimate contact and makes the proposed design very inefficient, resulting in a significant leakage rate through the FML because it will not be supported by a clay liner . Leaving the rule in its present form will create confusion and difficulty, which would leave owners vulnerable to lawsuits since there will be no state agency to interpret the rules.22

It has been well established that "intimate contact" between the two l iner components is a major factor in the effectiveness of composite liner systems . Placing any material between the liner components defeats the purpose of requiring a composite liner system in the first place, particularly if the liquids passing the FML are not intended to be collected and removed . Also, “direct and uniform contact with the compacted soil component” is unrealistic as HDPE installation s typically have wrinkles. EPA needs to decide which is more important

— that is , having a leak detection/collection system or an effective liner system . EPA should consider requiring a double liner system, with the leak detection/leachate collection system between two FMLs, leaving the lower FML in true intimate contact with the underlying compacte d soil barrier . In addition, earthen embankments often develop cracking . When the embankment cracks, the 2 - ft thick layer of compacted soil would likely also have cracked . At that point, a single 30 - mil HDPE liner becomes the sole line of defense, which further suggests the consideration of two liners placed on 2 - ft of compacted soil and a leachate collection system . Because this requirement applies to surface impoundments (i.e . standing water bodies) the leachate collection system cannot logically b e intended to control the depth of leachate; it must be intended to detect, contain, and collect contain leakage through the FML . Yet nothing in the proposed rule specifies that the system must drain to collection points . If a leachate collection/leak de tection system is to remain a requirement, please include a requirement that the system be designed to gravity drain to collection points. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06517 - 4 & 12 Organization: None Given Commenter Type: Anonymous Comment: As currently proposed, placing a flex geomembrane liner (FML) directly over a leak detection system makes the proposed design very inefficient, resulting in a significant leakage rate through FML because it will not be supported by a clay liner . A composi te liner (combination of compacted clay and FML) beneath a surface impoundment would provide adequate protection of ground water . As a verification of the soundness of the impoundment a perimeter ground water monitoring system could also be required.23

Comm ent Number: EPA - HQ - RCRA - 2009 - 0640 - 06018 - 7 Organization: Indiana Department of Environmental Management (IDEM) Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06298 - 74 Organization: Tennessee Department of Environment and Conservation (TDEC) Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06398 - 41 Organization: Duke Energy Commenter Type: Electric Utility Company Comment : T he introduction of the leachate collection system between the two components of the composite liner would defeat the composite action . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 35 & 36 Organization: Kansas Department of Health and Environment Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06424 - 12 Orga nization: Garrett & Moore, Inc. Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06819 - 24 Organization: Missouri Department of Natural Resources Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 23 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09349 - 10 Organization: Santee Cooper Commenter Type: Electric Utility Company Comment : Proposed 40 CFR §257.71(a)(I) and 40 CFR §257.72(a)(2) specify that a composite liner be installed on existing and new CCR surface impoundments respectively . Included in these requirements is the stipulation that a leachate collection system be installed between the upper and lower components of the composite liner . This makes no sense since proposed 40 CFR §257.70(a)(2) and 40 CFR §257.72(a)(2) require that the composite liner be a24

two part system composed of a flexible membrane liner and a compact soil layer in direct contact with each other . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06352 - 18 Organization: Dayton Power & Light Company (DP&L) Commenter Type: Electric Utility Company Comment : G iven that both components of the liner system must be in direct contact with one another, the re is no way that a leachate collection system can be installed between these two components . EPA should eliminate the proposed requirement from the final regulations directing that leachate collection systems in the case of surface impoundments be betwee n the upper and lower components of the liner system when these components must be “ in direct and uniform contact ” with one another . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 9 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06352 - 18 Organization: Dayton Power & Light Company (DP&L) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06529 - 41 Organization: NiSource Corporate Services Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06532 - 35 Organization: Southern Illinois Power Cooperative Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06827 - 14 Organization: Oklahoma Gas and Electric Company (OG&E ) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06863 - 42 Organization: Avista Corp. Commenter Type: Electric Utility Company25

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09885 - 28 Organization: Progress Energy, Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 54 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment : The design criteria incorrectly require a leachate collection syst em between the upper and lower components of the composite liner system . Delete “and a leachate collection system between the upper and lower components of the composite liner” in the first sentence . Delete “and leachate collections system” in the second sentence. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06832 - 28 Organization: SCANA Corporation Commenter Type: Electric Utility Company Comment : We believe EPA made an error in proposing a leachate collection system for impoundments where the leachate collection system is placed between the upper and lower components of the composite liner . In landfills a leachate collection system is placed above the liner and the proposal details the upper flexible membrane liner must be in direct contact with the lo wer clay liner. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 07047 - 30 Organization: Great River Energy Commenter Type: Electric Utility Company Comment : The p roposed rule require s a composite liner system for existing impoundments which are to be retrofitted and kept in operation . The rule specifies that a leachate collection system is to be placed between the flexible membrane liner and the compacted soil barrier . However, parag raph 257.71(a)(2) requires direct and uniform contact between the two liner components . This is not possible with a leachate collection system between them . This would create a situation where owners would be out of compliance with one requirement or the other and vulnerable to lawsuits . Please revise these paragraphs to remove the requirement for intimate contact between the two liner components.26

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 07534 - 4 & 6 Organization: Aquaterra Environmental Solutions, Inc. Commenter Type: Other Company Response : The Agency agrees that the leachate collection and removal system requirements proposed for CCR surface impoundments would be counterproductive and proposed this requirement in error . The integrity of the composit e liner system is dependent upon the direct and uniform contact of the upper FML component with the lower soil component . The proposed requirement to construct a leachate collection system between the FML and soil components would prevent the direct and u niform contact of the upper and lower components and, therefore, compromise the integrity of the composite liner . For this reason, EPA has revised the requirements for CCR surface impoundments accordingly and is not requiring a leachate collection and rem oval system for new or existing surface impoundments . As the commenter argued, a leachate collection and removal system in a surface impoundment is not intended to control the depth of leachate, but it is intended to detect, contain, and collect leakage t hrough the upper component of the composite liner system . Therefore, a leachate collection and removal system in a surface impoundment designed for its intended purpose would require installation of the leachate collection and removal system between a dou ble liner system . EPA ’ s risk analyses show that a single composite liner system will protect human health and the environment at most sites across the country, and thus, a double liner system is not necessary as a national standard . Finally, since the Ag ency is not requiring a double liner system, with the leachate collection and removal system between the liners, the Agency is not requiring the owner or operator to monitor the system for leakage . Comment: N othing in the proposed rule indicates that owners or operators are required to inspect the [leachate collection] system to monitor leakage, or to take any action in the event of a leak and that the Agency should consider revising the rules to add monitorin g requirements and specify actions required upon detection of a leak. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06517 - 4 & 12 Organization: None Given Commenter Type: Anonymous27

Response : As discussed previously, the final rule is not requiring the installation of a leachate collection system for CCR surface impoundments . Nevertheless, CCR surface impoundments and lateral expansions must be examined by a qualified person as follows a t intervals not exceeding 7 days for any appearances of actual or p otential structural weakness and other conditions which are disrupting or have the potential to disrupt the operation or safety of the CCR unit and must be inspected annually by a qualified professional engineer to ensure that the design, construction, ope ration, and maintenance of the CCR unit is consistent with recognized and generally accepted good engineering standards . Although it was not a requirement in the proposed rule, the final rule requires the same inspections for CCR landfills and lateral exp ansions as is required for CCR surface impoundments. Comment: Composite liners should not be mandated throughout a wet/surface impoundment disposal area . Composite liners are an appropriate requirement beneath the impoundment proper or over the impoundment basin where a persistent source of water exists, but not beneath the containment dikes or other impounding embankments where a composite liner represents a weak plane in the foundation of the containment structure and poses stability issues . R ather, with regard to containment dike/impounding embankment areas, the use of soil and/or other non - geosynthetic seepage barriers in combination with subsurface drains is a better approach for stability, management of seepage and leachate, and long - term s urface and groundwater protection . Mechanisms to promote the passive dewatering of the CCRs, and collect and control seepage and leachate, will yield the greatest dividends for stability and long term environmental protection . The perfect liner system an d watertight bathtub do not exist. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03451 - 5 Organization: Commenter Type: Private Citizen 6 . Liner Design Requirements Applicable to New CCR Landfills, Existing and New CCR Surface Impoundments and All Lateral Expans ions. a . Use of Composite Liners Only . Comment: The Agency should not allow alternative liner designs for the CCR landfills and CCR surface impoundments . The science of liner design for CCR waste containment structures has not advanced to the point where alternative liner designs should be allowed . A28

standard composite liner should be the required standard . Using an alternate design that consists of a lin er of only one type of material, such as clay soils or a high density polyethylene (HDPE) flexible membrane liner (FML) would not be appropriate since each of these materials has limitations to its use . Rather , a composite liner composed of both types of materials would mitigate the shortcomings of each separate material . Other liners, such as geosynthetic clay liners, which rely on the hydration of sodium bentonite, have not been tested with CCR leachate . Furthermore, laboratory tests will not determine their long - term viability in the field . It is impossible to predict with any certainty what the CCR materials will do in these landfills over time . The science of CCR materials is still expanding at a rapid rate, and our understanding of leachates for med from the different sources of coal and the different combustion processes over time is not fully defined . Even for facilities that use the same source of coal with the same combustion processes, the temperature gradients, moisture holding capacity of the CCR wastes, and changes in oxidation/reduction potentials within a CCR landfill can change the dominant mineral phases and more importantly, the solubility of the metals in the wastes . Therefore, leachate compositions are variable in both species pres ent and concentrations . Because of this variability, the interactions between metal - laden leachates from CCR’s and different liner materials have not been studied. A composite liner with an effective leachate collection and removal system should be the s tandard . Hydraulic control of both the FML component and the compacted clay layer (CCL) component of a composite liner, is reasonably well understood and can be designed to minimize the flow of aqueous liquids . With alternative designs, there is no assurance and no validation that the alternative design can achieve the same level of performance . In the absence of test data on proposed alternative designs, allowing alternative designs on new CCR disposal units wo uld be irresponsible . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06313 - 103 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Response : EPA agrees that new CCR disposal units should only install composite liner systems but disagrees that all alternative designs for a composite liner system should be rejected as insufficiently protective . As discussed in subsequent comment responses, many commenters29

provided strong evidence that the composite liner system required in the proposed rule is n ot always feasible or necessary to protect groundwater resources, and the Agency agrees . R esearchers have demonstrated the protectiveness of alternative liners, particularly geomembranes (GM) over geosynthetic clay liners (GCL). 1 For example, t he available data on the hydraulic effectiveness of GM/GCL composite liners demonstrates that a GM/GCL meets or exceeds the hydraulic performance of a GM/CCL liner design . Some states may also have requirements for alternative liner design s that are more stringent than the composite liner requirement , and the approach in the proposed rule would have effectively overruled those requirements by mandating that the facility install only a composite liner . Although EPA does not have data on the compatibility o f alternative liners with CCR and CCR leachate, the final rule requires that the owner or operator provide certification by a qualified professional engineer that t he alternative composite liner, at a minimum, meets or exceeds the performance of a composit e liner with respect to differential settlement, slope stability, puncture resistance, compatibility with CCR (chemical resistance) , and compatibility with sub - grade conditions. EPA also received comments from some states; e.g., Alaska, stating that suffi cient soil does not always exist in the state that would provide the required hydraulic conductivity . Allowing alternatives to the two feet of compacted soil will provide facilities in these states with a liner material with an equivalent or better hydrau lic performance than two feet of compacted native soil . E PA has also evaluated the performance of compacted clay liners, geomembranes (FMLs and HDPEs) , geosynthetic clay liners, and composite liners with two feet of compacted soil and determined that GM/G CL composite liners can be constructed to achieve hydraulic efficiencies in the range of 99 to 99.9% . These high efficiencies demonstrate that the GCL component of a GM/GCL composite liner is effective in impeding leakage through holes in the GM component of the liner. 2 EPA also developed guidance for the selection and installation of various types of liners including GCLs . 3 Therefore, u pon consideration of all the comments, EPA research, technical papers, and a thorough review of EPA’s revised risk ass essment, EPA

1 USEPA, “Assessment and Recommendations for Improvi ng the Performance of Waste Containment Systems,” EPA 600/R - 02/029, December 2002. 2 USEPA, “Assessment and Recommendations for Improving the Performance of Waste Containment Systems,” EPA 600/R - 02/029, December 2002. 3 USEPA, “Guide for Industrial Waste Management,” Chapter 7 (http://www.epa.gov/osw/nonhaz/industrial/guide/pdf/chap7b.pdf).30

acknowledges that the rule, as proposed, was overly prescriptive and should allow for alternative liners that are at least as protective of groundwater as a composite liner . b . Use of Alternative Liner Designs . Comment: It is not appropriate to allow alternative designs for new disposal units . It is impossible to predict with any certainty what the CCR materials will do in these landfills over time . The science of CCR materials is still expanding at a rapid rate, and our understa nding of leachates formed from the different sources of coal and the different combustion processes over time is not fully defined . Even for facilities that use the same source of coal with the same combustion processes, the temperature gradients, moistur e holding capacity of the CCR wastes, and changes in oxidation/reduction potentials within a CCR landfill can change the dominant mineral phases and more importantly, the solubility of the metals in the wastes . Therefore, leachate compositions are variabl e in both species present and concentrations . Because of this variability, the interactions between metal - laden leachates from CCR’s and different liner materials have not been studied. The science of liner design for CCR waste containment structures has not advanced to the point where alternative liner designs are acceptable . A standard composite liner should be the required standard . Using an alternate design that consists of a liner of only one type of material, such as clay soils or a high density p olyethylene (HDPE) flexible membrane liner (FML) would not be acceptable since each of these materials has limitations to its use, but a composite liner composed of both types of materials would mitigate the shortcomings of each separate material . Other l iners, such as geosynthetic clay liners, which rely on the hydration of sodium bentonite, have not been tested with CCR leachate . Furthermore, laboratory tests will not determine their long - term viability in the field. Comment Number: EPA - HQ - RCRA - 2009 - 06 40 - 06313 - 103 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Response : For the reasons stated in the response to the previous comment, EPA agrees that new CCR disposal units should only install composite liner systems . However, the Agency believes composite liners consisting of an alternative to the two feet of compacted soil with a hydraulic conductivity of 1 x 10 - 7 cm/sec as the lower component and a geomembrane upper31

component can be effective liners provided that the liquid flow rate through the lower component of the alternative composite liner is no greater than the liquid flow rate through two feet of compacted soil . The final rule is allowing such alternative composite liners provided the liquid flow rate equivalency is certi fied by a qualified professional engineer. Comment: In a performance - based regulatory system, there are a number of technologies and techniques that will reduce the risk of offsite migration of contaminants at least as much as composite liners, including: Subsurface slurry wall technology , I n - situ chemical fixation (ISCF) , I n - situ solidification/stabilization (ISS) , Natural attenuation, supported by groundwater modeling and monitoring and enhanced natural attenuation by chemical additions , and In situ seco ndary mineral growth/precipitation and contaminant sequestration in ash deposits (including enhanced processes by chemical additions) . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06300 - 30 Organization: Southern Company on behalf of itself and its four subsidiari es: Alabama Power Company, Georgia Power Company, Gulf Power Company, and Mississippi Power Company Commenter Type: Electric Utility Company Response : The Agency does not have sufficient experience or data on the systems suggested by the commenter to warrant allowing their use as an alternative to composite liners . Consequently, the final rule is requiring composite liners, or alternative composite liners as described in the response to the previous comment, for new CCR disposal units and all lateral expansions. Comment: States should have the flexibility to review and approve alternative liner designs that will provide adequate protection. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 34 Organization: Kansas Department of Health and Environment Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 21 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09337 - 35 & 36 Organization: Arizona Department of Environmental Quality (ADEQ) Commenter Type: State Government32

Response : EPA is allowing alternative composite liners as described above to provide a level of flexibility for site - specific conditions . The alternative composite liner must be certified by a qualified professional engineer . States are also free to develop their own regulations and/or permitting programs using their solid waste laws or other state authorities tha t would require public notice, hearings, and State approval of alternative liner designs. Comment: The Subtitle D rule should allow for alternate liner systems . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06252 - 17 Organization: Minnkota Power Cooperative, Inc . (Minnkota) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06254 - 19 Organization: Sunflower Electric Power Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06722 - 21 Organizati on: Arkansas Electric Cooperative Corporation (AECC) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08220 - 19 Organization: PowerSouth Energy Cooperative Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08253 - 27 Organization: Xcel Energy Commenter Type: Electric Utility Company 

### Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08841 - 32 

### Organization: Deseret Generation and Transmission Co - operative Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09427 - 19 Organization: San Miguel Electric Cooperative, Inc . (San Miguel) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09951 - 24 Organization: Full Circle Solutions, Incorporated Commenter Type: Beneficial User33

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10017 - 11 Organization: Salt River Project (SRP) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05827 - 2 Organization: Commenter Type: Private Citizen , P.E. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06860 - 13 Organization: South Carolina Chamber of Commerce, Environmental Technical Committee Commenter Type: Trade Association Comment: NDEQ’s permit program allows for alternative liner design demonstrations that are equivalent to the requirements for municipal solid waste landfills under 40CFR Part 258 and believes this is a reasonable and protective approach in states that have permit programs that adopt these same requirements. Comment Number: EPA - HQ - RCRA - 2 009 - 0640 - 07533 - 36 Organization: Nebraska Department of Environmental Quality (NDEQ) Commenter Type: State Government Comment: Allow alternatives to composite liners when site specific characteristics support such alternatives . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06424 - 11 Organization: Garrett & Moore, Inc. Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10017 - 29 Organization: Salt River Project (SRP) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 7 Organization: Kansas Department of Health and Environment Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06410 - 58 Organization: Anonymous Commenter Type: Anonymous Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10017 - 2934

Organization: Salt River Project (SRP) Commenter Type: Electric Utility Company Comment: A llow for the consideration of alternative liner systems that provide equivalent protection of human health and the environment . Com ment Number: EPA - HQ - RCRA - 2009 - 0640 - 06832 - 27 Organization: SCANA Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09358 - 7 Organization: Interstate Power and Light Company (IPL) and Wisconsin Power and Light Company (WPL) Commenter Type: Electric Utility Company Comment: A demonstration made to Washington State and Lewis County of the adequacy of an alternative liner clearly demonstrates that this approach is protective of groundwater and that a composite liner is not the only way to protect groundwater and should not be the only default liner required under the CCR landfill requirements . The final rule should include the flexibility to use alternatives to composite liners that are demonstrated to achieve the same long - term performance standards. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 07048 - 12 Organization: TransAlta Centralia Generation Commenter Typ e: Electric Utility Company Comment: EPA should consider allowing alternate liners which are as effective as the proposed composite liners for landfills and surface impoundments . This would allow flexibility to site operators and provide the same prote ction for management of CCRs in landfills and surface impoundments. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06917 - 29 Organization: Texas Commission on Environmental Quality (TCEQ) Commenter Type: State Government Comment: T here should be a process for approval of alternative liner systems with the flexibility to match site specific conditions and material to be stored. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06865 - 23 Organization: Constellation Energy35

Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09349 - 13 Organization: Santee Cooper Commenter Type: Electric Utility Company Comment: The CCR proposed rules should provide for alternate liner systems or variances from liner installation at locations where local geology or hydrogeology preclude the contamination of groundwater resources by leachate from the solid waste facility Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10166 - 16 Organization: Consumers Energy Company Commenter Type: Electric Utility Company Comment: EPA should provide for an engineering standard that can be met by facilities as a variance from leachate collection and composite liner requirements identified under Subpart C or D regulation. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08225 - 19 Organization: Minnes ota Power (ALLETE) Commenter Type: Electric Utility Company Comment: ASTSWMO would support allowing facilities to use alternative designs . Such flexibility would certainly be warranted if a State required or approved design differs from the federal req uirements, yet is demonstrated to provide equivalent or greater performance. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08787 - 40 Organization: Association of State and Territorial Solid Waste Management Officials (ASTSWMO) Commenter Type: State Government Comment: MassDEP recommends that alternative designs be based on performance equivalent to the specified standard design . The Massachusetts regulations include a provision allowing for review and approval of alternative designs as long as the design will achieve equivalent or superior performance to the standard design for the life of facility operations, closure and post - closure period . The equivalent design must use methodologies, materials and technologies that are clearly demonstrated to have been s uccessful in similar applications and can use acceptable QA/QC methods to monitor construction and performance .36

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08251 - 12 Organization: Massachusetts Department of Environmental Protection Commenter Type: State Government Comment: EPA ’ s final rule should allow alternative liner designs at CCR disposal facilities . GCLs have been used successfully for 25 years as an alternate to compacted clay in both Subtitle C and Subtitle D landfill composite liner systems. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 04523 - 1 & 2 Organization: Brantley Engineering, LLC Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05828 - 1 Organization: Provost & Pritchard Consulting Group Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05929 - 1 Organization: Schnabel Engineering Commenter Type: Other Company Comment : T he Subtitle D rule should allow for alternative liner systems to be approved by a qualified state program where the alternate liner can be shown as equally or more protective than a composite liner detailed in the existing proposal . For example a geosynthetic clay liner can perform equally as well as a flexible membrane composite liner in many geologic settings. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 07047 - 29 Organization: Great River Energy Commenter Type: Electric Utility Company Comment : I t is absolutely necessary that any Subtitle D option allow for the usc of alternative liner systems for CCR disposal facilities . Alternative liner systems can provide equal if not more protection to groundwater, and there is no reason why these alternate, but equally protective systems, should not be available under the regulations . Depending on the location and physical characteri stics of a CCR disposal facility, there are a range of liner systems that may be available to meet the applicable groundwater standards at the point of compliance . By establishing performance standards, this would give flexibility to tailor a system to me et the site specific characteristics of an individual disposal unit . These would include topographical, geological, climatological, and hydrological characteristics . EPA should not limit alternative37

liner design systems and deny owners/operators the abil ity to utilize systems that ar e equally or more protective as the composite liner system proposed in the Subtitle D options . Additionally, due to the significant volume of clay that is needed to line a facility, as well as the likelihood that other units would need the same materials in the same timeframe, there may be an insufficient supply of clay and/or it may be difficult to transport the needed volume of clay to the site. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06833 - 20 Organization: Dominion Resources Services, Inc. Commenter Type: Electric Utility Company Comment : Based on the technical information presented, CETCO requests that EPA's final rule allow GCLs as an alternative to the low - permeability soil component underneath the FML for both the proposed RCRA Subtitle C and Subtitle D composite liner options . GCLs have become the state of the practice for waste containment facilities . EPA research has shown that GCLs provide equivalent or superior performance compared with compacted clay liners. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06195 - 1 Organization: CETCO Commenter Type: Other Company Comment : The proposed regulations do not provide sufficient flexibility to consider alternative liners, leachate management methods, or final covers to accommodate variables in local conditions such as soil types, depth to groundwater, distance from surface water, and annual precipitation . The prescriptive one - size - fits - all approach unnecessarily ties the hands of state regulators and prevents them from tailoring permits to match the landfill design requirements to actual physical circumstances . For example, many aspects of the design imposed in the proposed regulation may be unnecessary in areas where local conditions provide an adequate and preferred d egree of natural protection. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06254 - 23 & EPA - HQ - RCRA - 2009 - 0640 - 06912 - 8 Organization: Sunflower Electric Power Corporation Commenter Type: Electric Utility Company Comment: The CCR proposed rules should provide for fl exibility in design and construction . Performance - based standards should be allowed to supplement default, prescribed engineering standards.38

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08840 - 18 Organization: Electric Power Generation Association Commenter Type: Trade Association Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10166 - 15 Organization: Consumers Energy Company Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08850 - 13 Organization: Lansing Board of Water & Light (BWL) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08853 - 12 Organization: Lower Colorado River Authority (LCRA) Commenter Type: Electric Utility Facility Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08865 - 8 Organization: Geosyntec Consultants Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09239 - 68 Organization: Prairie State Generating Company, LLC (PSGC) Commenter Type: Electric Utility Company Comment: It is critical that any rule allow flexibility in liner designs . Alternative liner designs can be just as protective and more cost - effective in many cases . For example, we have demonstrated that an engineered geo - composite liner (manufactured clay & synthetic composite mat) can be as effective as a standard compacted c lay & synthetic liner . We have also demonstrated that in many cases a simple clay liner, or even low permeability natural soils or impermeable rock formations, can provide the necessary protection, especially in arid states with no shallow or drinkable gr oundwater . We strongly oppose the concept of a "one - size fits all" prescriptive national liner standard, since such an approach would be arbitrary and completely ignore critical technical considerations such as waste characteristics, local climate, geolog y, native soil permeability, depth to groundwater, presence or absence of down - gradient receptors, leachable contaminants in the waste material, the mitigating effects of natural attenuation, etc . These are all important engineering and design considerati ons and illustrate why state permitting engineers, geologists and hydrologists are in the best position to determine what is technically39

necessary and appropriate for a given disposal facility . It is important that any CCR rule finalized by EPA allow for alternative liner designs that factor in local circumstances . To do otherwise would be arbitrary and capricious. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08253 - 8 Organization: Xcel Energy Commenter Type: Electric Utility Company Comment: Geosyntec support s the use of GCLs as an alternative to a compacted clay liner at CCR disposal sites . Geosyntec’s experience at over one hundred waste containment liner system design and construction projects indicates that, when properly designed and constructed, GCLs ca n provide equivalent performance to CCLs . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08865 - 8 Organization: Geosyntec Consultants Commenter Type: Other Company Comment: It doesn't make sense for E PA to advocate prescriptive designs for applications where multiple technologies are available and perform similarly for two reasons; first , this stifles the development of newer, more effective and potentially less costly technology alternatives because it limits the opportunity fo r their eventual application . This seems to be counter to what EPA's mandate shou l d be . Second, it places all of the risk, should the technology that EPA supports ultimately prove inadequate, on EPA . The USEPA should be setting performance based standards and spending their resources evaluating the proposed approaches but letting the marketplace deliver solutions that are first effective, then cost effective for those who have to pay the bill. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05798 - 1 Organiza tion: Anonymous Commenter Type: Environmental Consultant Comment: As landfill designers, we have successfully designed, perm i tted, and constructed numerous Subtitle D Landfill Sites utilizing geosynthetic clay liners with site soils, and believe that th e proposed coal ash landfill regulations should include language to incorporate equivalent or superior liner designs. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05825 - 1 Organization: TriAD Environmental Consultants, Inc.40

Commenter Type: Other Company Comment: I have operated and designed many landfill cells that use alternative liner designs at Subtitle C and D facilities and consider these should also allowed at CCR disposal facilities . A common alternative liner design involves the use of a geosynt hetic clay liner (GCL) in place of the compacted clay layer underneath the FML . There is a significant body of independent research and field performance data (much of it from USEPA studies) which shows that GCLs can outperform compacted clay liners. Comm ent Number: EPA - HQ - RCRA - 2009 - 0640 - 05826 - 1 Organization: Vista Consultants Commenter Type: Other Company Comment : It is my experience and professional opinion that alternative liner design involving the use of a geosynthetic clay liner (GCL) in place of the compacted clay layer underneath the FML should be allowed . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05867 - 1 Organization: Not Given Commenter Type: Professional Engineer Comment : Having designed liner systems for solid waste and incinerator ash monofills for the past 20 years, I have found that allowing the designer to select the appropriate soil component of the liner system is by far the best solution . Compacted soil liners are difficult to properly design and construct . Many sites don't have adequate soil, so either have to import the entire compacted soil layer or amend site soils with sodium bentonite . Importing of soil or amending soil is expensive and can be avoided using geosynthetic clay liners (GCLs). Also, the depth to groundwater ca n be shallow at some sites . By using a GCL an owner can gain two feet of air space without sacrificing the performance of the liner system . This saves valuable air space which will lengthen the life of a facility. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05927 - 1 Organization: Parametrix Commenter Type: Other Company Comment : T he requirement in Subtitle D mandating a minimum of 2 feet of compacted clay in liner construction should be amended to allow for synthetic equivalents and/o r alternative liner designs that can be proven to be an equivalent in performance to the proposed 2 feet of clay41

overlain by a flexible membrane liner. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06041 - 5 Organization: SKB Environmental, Inc (SKB) Commenter Type: Other Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06251 - 4 Organization: We Energies Commenter Type: Electric Utility Company Comment : Alternative liner designs should be available based on a specific performance standard. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10732_DEN - 044 - 4 Organization: Platte River Power Authority Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10752_DEN - 064 - 2 Organization: Xcel Energy Commenter Type: Electric Utility Company Comment : Alternatives should be recognized, such as a geosynthetic clay liners (GCL) . Alternative liner designs based upon specific performance standards referenced in 40 CFR Part 258.40 should also be recognized. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06723 - 21 Organization: West Virginia Department of Environmental Protection (WVDEP) Commenter Type: State Government Comment : T he Subtitle D rule should allow for the use of alternative liner systems for CCR disposal units . In some regions of the country, the proposed composite liner system is unnecessary to ensure protection of groundwater . There are alternative liner systems that can provide equal if not more protection to groundwater and there is no reason why these alternate, but equally protective systems , should not be allowed. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08864 - 7 Organization: JEA Commenter Type: Electric Utility Facility Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09274 - 17 Organization: RRI Energy Inc.42

Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09536 - 9 Organization: Tennessee Valley Authority Commenter: John W . Myers Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09885 - 27 Organization: Progress Energy, Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06308 - 12 Organization: NRG Energy Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08270 - 5 Organization: Cliffs Natural Resources Inc . (Cliffs) Commenter Type: Other Company Comment: In many cases, local and/or econ o mical sources of suitable clay liner materi a l are not available, resulting in higher project costs. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05867 - 2 Organization: Commenter Type: Private Citizen, P.E. Comment: N ew surface impoundments should allow for the use of performance based alternate liner systems instead of specifying a given technology . This flexibility in the CCR rule would allow a site specific design of appropriate liners which could reflect site specific conditions . Different locations will have different site specific considerations, including depth to groundwater, which will need to be factored into the design standards . Even in certain locations where potential risks to groundwater are greater, many alternate liner systems can meet or exceed the performance standards proposed in the rule . This option should also allow a company employed Registered Professional Engineers (“PE’) and or hydrologists to accomplish compliance certifications; not just third party PEs or hydrologists. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06299 - 17 Organization: MidAmerican Energy Holdings Company (MidAmerican) Commenter Type: Electric Utility Company43

Comment: We strongly support the rule including flexibility for an applicant to make a demonstration that an alternative liner design would also be acceptable . This might be a compacted clay liner, such as the four foot thick compacted clay liner in Wisconsin rules, but it might also be used by an applicant that chooses to demonstrate the effectiveness of composite liners that include geosynthetic clay liners in conjunction with soils that do not meet clay liner requirements . Other possibilities might also arise . Given the diversity of soils across the US and the potential for new geosynthetic or other products to be developed in the future, provisions need to be included in the rule to allow their use if justified. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06416 - 54 Organization: W isconsin Department of Natural Resources (WI DNR) and Public Service Commission of Wisconsin (WI PSC) Commenter Type: State Government Comment: EPA should allow alternative liner designs at CCR disposal facilities . The proposed rule currently does not allow for any deviation from the liner requirements for CCR units regardless of site specific conditions, EPA appropriately asks whether the RCRA s ubtitle D option “should allow facilities to use an alternative design f or new disposal units” provided a registered PE or hydrologist certifies that an alternate design system would “ensure that the appropriate concentration values for a set of constituents typical of CCRs will not be exceeded in the uppermost aquifer at the relevant point of compliance

– i.e., 150 meters from the unit boundary downgradient from the unit, or the property boundary if the point of compliance (i.e., the monitoring well) is beyond the property boundary.” Id . at 35202 - 03 . There is no question t hat alternate liner systems must be allowed under the Subtitle D program. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 8 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06203 - 13 Organization: Arizona Public Service Company (APS) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06863 - 41 Organization: Avista Corp. Commenter Type: Electric Utility Company44

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06956 - 13 Organization: Tri - State Generation & Transmission Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09536 - 9 Organization: Tennessee Valley Authority Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09713 - 11 Organization: Indianapolis Power & Light Company (IPL) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09885 - 27 Organization: Progress Energy, Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0 640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09713 - 11 Organization: Indianapolis Power & Light Company (IPL) Commenter Type: Electric Utility Company Comment : Most states currently allow alternative designs under their RCRA s ubtitle D programs and that the experience of the municipal solid waste management community (i.e., regulators, owners, operators, and the public) on the use of alternative liners has been very positive . In particular, Geosyntec supports the use of GCLs as an alternative to a compacted clay liner at CCR disposal sites . Geosyntec’s experience at over one hundred waste containment liner system design and construction projects indicates that, when properly designed and constructed, GCLs can provide equivalent performance to CCLs . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08865 - 8 Organization: Geosyntec Consultants Commenter Type: Other Company Comment : A liner design constructed from alternative materials (as compared to the prescriptive proposed composite liner system under the design criteria of 40 C.F.R . § 257.70) that is equally protective of groundwater must be allowed . EPA already acknowledges that there45

are alternative l iner systems that can provide equal, if not greater, protection to groundwater . Indeed, EPA has consistently recognized throughout the Bevill Amendment regulatory determination process that, given the vastly different site - specific characteristics of CCR disposal units across the country, there is not a “one - size - fits - all” approach when it comes to regulatory design standards for these units . Thus, there is no good reason why alternate

– but equally effective

– liner systems should not be available for ut ility CCR unit designs. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06398 - 40 Organization: Duke Energy Commenter Type: Electric Utility Company Comment : The alternative liner design provision within 40 CFR 258.40(a)(1) is an essential element of Alaska's Subt itle D regulatory program because of a lack of soil that meets the hydraulic conductivity requirements of the prescribed composite liner in 40 CFR 258.40(b) . I t will be impossible to build a CCR landfill in Alaska in compliance with the proposed design requirements unless alternative liner designs are allowed. Comment Number: EPA - HQ - RCRA - 2011 - 0392 - 0196 - 3 & EPA - HQ - RCRA - 2009 - 0640 - 06409 - 5 Organization: State of Alaska Commenter Type: State Government Comment: It is recommended that technical equivalency [of alternative liners] be demonstrated not only on the basis of various hydraulic parameters , such as flow rate or flux, but also on physical / mechanical parameters , such as differential settlement and slope stability, and construction issues , such as puncture resistance, sub grade conditions, and weather constraints . The overall design, including liner cross section, specifications, and CQC and CQA activities during installation must provide for technical equivalency. Comment Number: EPA - HQ - R CRA - 2009 - 0640 - 09349 - 13 Organization: Santee Cooper Commenter Type: Electric Utility Company Comment: Alternative liner systems are important precisely because they meet, and can exceed, EPA standards in protecting human health and the environment . Furthermore, they often reflect and address state and regional geology. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10498 - 1346

Organization: Florida Electric Power Coordinating Group, Inc . (FCG) Commenter Type: Electric Utility Company Comment: EPA must recognize that alternative liner systems can be equally as protective as, or more protective than, composite liner systems . These alternative liner systems have been approved by EPA as an acceptable alternative to the composite liner for MSWLFs, which are more likely to pose a greater threat to human health and the environment than CCR landfills. Florida’s double HDPE geomembrane liner system (“double liner”) is a prime example of one of these alternative liner systems . 4 [Florida’s double liner system i s different from EPA’s double liner system requirements for hazardous waste landfills, required by RCRA § 3004(o)(4)(A), and detailed in 40 C.F.R . sections 264.301(c) and 264.302 . ] Under its EPA - approved MSWLF program, FDEP permits the use of a double liner as an alternative to the composite liner. This liner system was critically evaluated in the early - to mid - 1990s by the Florida Department of Environmental Protection (“FDEP”), a Technical Advisory Group formed by FDEP, and EPA . EPA has approved Flor ida’s Subtitle D MSWLF program, which includes this liner system option. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06300 - 30 Organization: Southern Company on behalf of itself and its four subsidiaries: Alabama Power Company, Georgia Power Company, Gulf Power C ompany, and Mississippi Power Company Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10497 - 9 Organization: Seminole Electric Cooperative, Inc . (Seminole) Commenter Type: Electric Utility Company

4 Florida has concluded that, if constructed in accordance with Florida’s Rule 62 - 701.400(3)(c), F.A.C., a double liner is more protective of the environment than a com posite liner installed in accordance with Rule 62 - 701.400(3)(b), F.A.C. Thus, in Florida, EPA’s proposed composite liner would be less protective than the liner systems currently in use. Florida has studied its EPA - approved double liner at least four time s, each time finding the double liner more protective than a composite liner. EPA has failed to provide any mechanism allowing states like Florida to approve sound alternative liner systems. It appears also that EPA failed to even consider Florida’s techni cal demonstrations or provide its own evidence contradicting them. For these reasons, EPA’s adoption and mandate of its proposed composite liner requirement, to the exclusion of any alternatives, is arbitrary and capricious. (See Motor Vehicles Mfrs. Ass’n v. State Farm Mutual Auto. Ins. Co., 463 U.S. 29, 43 (1983).)47

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10498 - 13 Organization: Florida Electric Power Coordinating Group, Inc . (FCG) Commenter Type: Electric Utility Company Comment: S oil/clay in adequate amounts or with adequate characteristics is not available for use in the propose d composite liner. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06846 - 10 & 12 Organization: Florida Department of Environmental Protection (FDEP) Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09282 - 10 & 12 Organization: North Carolina Department of Environment and Natural Resources Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10324 - 15 Organization: Public Service Company of New Hampshire (PSNH) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10498 - 13 Organization: Florida Electric Power Coordinating Group, Inc . (FCG) Commenter Type: Electric Utility Company Comment: T he Salt River Project‘s (“SRP”) Coronado Generating Station, located in St . John‘s Arizona, has climatic conditions favorable for CCR disposal . The facility operates a State of Arizona permitted FGD surface impoundment and ash landfill . The regional aquifer is located more than 300 feet below the bottom of the FGD impoundment . The average annual r ainfall for this area is less than 12 inches . The FGD impoundment and ash landfill are located on the Chinle Formation, which consists of 150 - 200 feet thick sequence of bentonitic clay, shale, and siltstone, with a hydraulic conductivity of 1x10 - 7 to 1x10 - 9 cm/sec . The permeability and thickness of the Chinle unit, along with the depth to groundwater, serve as BADCT for the ADEQ APP . The FGD impoundment has been operating with a natural clay liner for over 30 years . Contamination of the regional drinkin g water aquifer has not occurred in that time frame . Site specific modeling of groundwater flow over an operational period of 10,000 years indicates that the FGD impoundment has not, and will not, contaminate the regional groundwater under scenarios used in EPA‘s Risk Assessment. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10017 - 1248

Organization: Salt River Project (SRP) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment: SRP‘s Navajo Generating Station located on the Navajo Nation land in Arizona operates a CCR landfill for all of its CCRs destined for disposal (i.e., fly ash, bottom ash, and de - watered FGD mater ial) . The CCR landfill is located in a dry climate with an average annual rainfall of less than 8 inches . The depth to groundwater in the Navajo Sandstone Formation is 800 - 900 feet below the bottom surface of the landfill . Neutron logging is conducted a t the landfill to detect any moisture in the vadose zone . Groundwater monitoring is conducted down - gradient of the unit . The Navajo Sandstone Formation forms the principal regional aquifer system for the area. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment: A lternative liners may be acceptable in some geographic settings . Coal fly ash has extremely low moisture conte nt at the time of collection by the ESP or baghouse . As a result, it has a moisture deficit, meaning that it will retain a certain volume of water when exposed to atmospheric conditions . High calcium fly ash, such as that associated with some subbitumino us and lignite coals burned in the western U.S., also undergoes hydration reactions on exposure to water, further utilizing excess moisture . Placing ash in layers designed to utilize any excess moisture, and then covering with a low permeability cap or a water balance cap, can effectively minimize percolation through the ash . EPRI performed a field and modeling study of this concept at a western power plant burning subbituminous coal . The results supported the low percolation potential for the site, and were used to help obtain state approval for an alternative to the standard composite liner requirement. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09765 - 56 Organization: Electric Power Research Institute (EPRI) Commenter Type: Trade Association Comment: Eastman owns and operates a permitted hazardous waste landfill as well as an49

industrial solid waste landfill permitted under Tennessee solid waste regulations . Our experiences with the construction and quality assurance of both Subtitle C double liner sys tems meeting minimum technology requirements under 40 CFR 264.301 and Subtitle D composite liner systems meeting or equivalent to MSW standards under 40 CFR 258 demonstrate the value of and enhanced compliance assurance offered by alternate designs that ar e demonstrated to be equivalent or superior to a performance standard . For example, this proposed rule requires a composite liner that includes two feet of clay compacted to achieve a hydraulic conductivity of 1 x 10 - 7 centimeters per second . The clay so ils native to eastern Tennessee are ill - suited for compaction to this hydraulic conductivity . In order to achieve this performance, significant engineering and construction effort must be expended . In addition, substantial quality control and quality ass urance must also be employed to assure compliance with this performance standard is achieved . However, Tennessee's industrial landfill regulations allow facilities to use liners that are demonstrated to provide equivalent or superior performance . As a re sult, Eastman as well as other industrial landfills in the State have demonstrated that alternate designs which substitute a flexible membrane liner (FML) for the clay component of a composite liner system achieve compliance with the standards . Furthermor e, FMLs can more consistently and more easily be shown to meet construction quality assurance requirements due to the manufacturing quality controls imposed by the industry as well as the established and rigorous testing protocols to which FMLs can be subj ected (for example, leak testing of 100% of all welded seams) . Eastman’s experience has shown that construction of a composite liner consisting of FMLs is approximately one - third the cost of constructing a composite liner consisting of an FML and clay . Eastman therefore supports allowing facilities to use alternate designs for liner systems under both the Subtitle C and Subtitle D options . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06880 - 7 Organization: Eastman Chemical Company (Eastman) Commenter Type: Oth er Company Comment: Even in locations where potential risks to groundwater are greater, there are alternate liner systems that can achieve the same level of protection as the composite liner system proposed by EPA . For example, geosynthetic clay liner (“GCL”) or similar systems can meet or exceed the performance standards of clay liners and certainly are equivalent or superior in some circumstances to two - feet of compacted soil in the lower component of the composite50

liner systems proposed under the Sub title D option . Therefore, in many circumstances, a liner system using the GLC in lieu of the two - feet of compacted soil readily enables a CCR disposal unit to meet the applicable groundwater monitoring standards . Depending on the location and physical c haracteristics of the disposal unit, there are a range of liner systems that may be available to meet the applicable groundwater standards at the point of compliance . EPA should not limit alternative liner design systems and deny owners/operators the abil ity to utilize systems that are equally or more protective as the composite liner system proposed in the Subtitle D option. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06203 - 13 Organization: Arizona Public Service Company (APS) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06956 - 13 Organization: Tri - State Generation & Transmission Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09885 - 27 Organization: Progress Energy, Inc. Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment: Geosynthetic clay liners would be an alternative to the prescriptive compacted clay component of the composite liner in the rule . Since GCLs are expected to contribute the lowest leakage, lower than compacted clay, and can help achieve the EPA mission to protect human health and the environment, we recommend that GCLs be allowed as an alternative liner component. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 11174_CHI - 002 - 2 Organization: Geosynthetic Materials Association (and CETCO) Commenter Type: Trade Association Comment: In light of the fact that the locations of CCR surface impoundments vary widely in terms of their topographical, geological, climatological and hydrological characteristics, any liner requirement must provide some degree of flexibility to account for the51

site - specific characteristics associated with those impoundments . Otherwise, the same concerns with over - regulation that the Agency described in its August, 1993 final regulatory program will resurface in the Subtitle D option . Therefore, the Agency should provide an owner/operator the ability to utilize alternative liner systems that are equally or more protective as the composite liner system proposed in the Subtitle D option for surface impoundments, as long as their use is approved by the appropriate state regulatory agency. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06827 - 13 Organization: Oklahoma Gas and Electric Company (OG&E) Commenter Type: Electric Utility Company Comment: EPA should allow alternative liner systems based on individual site conditions or based on adequate State program determinations . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08247 - 2 Organization: Tucson Electric Power Company Commenter Type: Electric Utility Company Comment: We recommend that the regulations require the use of a geomembrane lining system (geomembranes and \ or geosynthetic clay liners with membranes) as this system has been demonstrated (by EPA) to be a most effective barrier methodology, regardless of the classification of the materials (hazardous, non - hazardous or designated for beneficial re - use). Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05745 - 1 Organization: BTL Group of Companies Commenter Type: Other Company Comment: EPA should define and require a ‘composite liner’ consisting of two components: An upper component consisting of a flexible membrane liner (FML), and a lower component consisting of a geosynthetic clay liner . If ‘composite liner’ is not redefined to include a lower component GCL, then the allowance of an alternative liner design/system should be included . Comment Number: EPA - HQ - RCRA - 2009 - 0 640 - 05235 - 1 Organization: Propex Geosynthetics Commenter Type: Other Company Comment: EPA expresses reluctance in allowing alternative liners for new CCR facilities on page 75 FR 35203 . This reluctance appears to be due, in part, to the expectation that owners52

would propose a soil liner alone in place of the entire prescribed composite liner . We agree that a soil liner alone would not be as protective as the prescribed composite liner system, and should therefore not be considered an adequate substitute . We agree that an upper FML component is essential . However, there are other technically feasible alternatives to the lower 2 - ft compacted soil component that should be considered . Specifically, use of a geosynthetic clay liner (GCL) below the FML shou ld be considered as an equivalent substitute for a compacted soil component . GCLs are factory - manufactured mats consisting of 0.75 lb/ft2 of sodium bentonite clay between two geotextile layers, with a hydraulic conductivity of 5 x 10 - 9 cm/sec per ASTM D58 87 . Due to their low hydraulic conductivity, GCLs are frequently used as a substitute for two - foot thick compacted soil liners in composite liner systems of many municipal solid waste landfills (MSWLFs) . Field evidence has shown that composite liners wit h GCLs function equally well as, or better than composite liners with a compacted soil component (Bonapaiie et al . 2002, Bareither et al . 2010). Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06524 - 1 Organization: CETCO and University of Wisconsin Madison Commenter Type: Other Company Comment: T he regulations should include an allowance for alternative liner designs/systems . Under both Subtitles D and C, alternative designs using geosynthetics have frequently and consistently been proven to be cost effec tive solutions to situations where natural soils and aggregates are not readily available . The benefits and successes of utilizing geosynthetic systems in containment systems have been well documented by the technical materials and reports by the EPA . Ge osynthetics have been tested and successfully evaluated in great detail over a long period of use in a extremely wide range of applications by EPA. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06552 - 1 Organization: Agru America, Inc . (Agru) Commenter Type: Other Company Comment: A performance standard for liners must be established . Performance standards provide facilities with flexibility while ensuring that appropriate safeguards are in place . Providing an alternative standard to address circumstances where the requirement is highly dependent on site - specific conditions is appropriate when mechanisms are in place to ensure that the alternative is protective of health and the environment . To ensure that the alternative53

standard is protective, the stand ard can be accompanied by notification and documentation requirements . Certification by a registered professional provides an appropriate level of certainty that the performance standard is being met . In addition, notification would be provided to the st ate and the public such that enforcement could be pursued if necessary . P roviding an alternative like the one it is proposing allows facilities the flexibility to account for site conditions . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06529 - 40 Organization: NiSource Corporate Services Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06532 - 34 Organization: Southern Illinois Power Cooperative Commenter Type: Electric Utility Company Comment: For the geological and climatic conditions encountered in Kansas this proposed [composite liner] language is limiting and would not allow designs which can be equally protective while having the advantage of being sustainable indefinitely into the future . Capillary barrier designs using in - situ materials and geosynthetic clay liners have been used successfully in Kansas landfills located in areas of low precipitation . Other liner designs consisting of compacted clay have been adequately protective as de monstrated by years of groundwater monitoring in areas of eastern Kansas with higher precipitation and more shallow groundwater . A composite Subtitle D liner is clearly not needed to protect groundwater or surface water in all geologic and climatic scenar ios . States should have the flexibility to review and approve of alternative liner designs that will provide adequate protection. 5

5 Therefore, Kansas requests that paragraph (a)(I) of this section be modified to allow alternate designs as follows: 1) With a composite liner, as defined in paragraph (a)(2) of this section and a leachate collection system that is designed and constructed to maintain less than a 30 - cm depth of leachate over the liner or an alternate design approved by the Director of an approved state that demonstrates that leachate will be contained or manag ed in a manner that is protective of ground water and surface water. The design of the composite liner and leachate collection system must be prepared by, or under the direction of, and certified by an independent registered, professional engineer. (modifi cation in italics)54

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 03444 - 34 Organization: Kansas Department of Health and Environment Commenter Type: Sta te Government Comment : Th e proposed language is restrictive and would not allow designs which can be equally protective of groundwater and surface water . Other alternate liners have been used successfully throughout the country and provisions to allow alternate liners need to be incorporated . A composite Subtitle D liner is clearly not needed to protect groundwater or surface water in all geologic and climatic scenarios . States should have the flexibility to review and approve alternative liner design s that will provide adequate protection as allowed under part 258 for sanitary landfills . Therefore, we request that paragraph (a)(1) of this section be modified to allow alternate designs Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 21 & 32 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09337 - 35 & 36 Organization: Arizona Department of Environmental Quality (ADEQ) Commenter Type: State Government Comment : For new CCR landfills and lateral expansions , t here should be provisions for alternative landfill liner systems that have been demonstrated as acceptable under the state municipal waste landfill experiences per state . F or new CCR surface impoundments a nd lateral expansions , t here should be a process for approval of alternative liner systems . This should address the flexibility to match site specific conditions and material to be stored. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06865 - 23 Organization: Constellation Energy Commenter Type: Electric Utility Company Comment : T he regulations should provide performance, rather than prescriptive requirements to be met . Sites for storage of CCR vary according to physiographic province within a particular st ate, even more so across the entire United States . Design standards that may be suitable for one site may provide inadequate safety and environmental protection for another and may represent a significant overdesign for yet a third site . By establishing performance standards to be met, a framework allowing for innovation, incorporation of developing “best55

practices” and site --- specific solutions is promoted . This approach can result in solutions that are not only more cost --- effective, but can also prov ide better protection of property and the environment, in view of the specific site conditions encountered . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06831 - 2 Organization: MACTEC Engineering and Consulting, Inc. Commenter Type: Other Company Comment: There should be state oversight for all disposal facility designs . Minnesota does an independent review of all facility designs prior to permit issuance . MPCA staff have approved alternative liner designs for disposal facilities if they are at least as protec tive as the USEPA's proposed composite liner system . Minn . R . 7035.2815, subp . 7(K) allows the commissioner to approve an alternative liner system design .. . "The commissioner's approval shall be based on the ability of the proposed liner system to co ntrol leachate migration, meet performance standards, and protect human health and the environment." These landfill liners consist of a 1 foot of clay, 2 feet of clay, or a Geosynthetic clay liner overlain by a minimum 60 mil HDPE liner. Comment Number: EP A - HQ - RCRA - 2009 - 0640 - 06838 - 7 Organization: Minnesota Pollution Control Agency (MPCA) Commenter Type: State Government Response: EPA agrees with the commenters and is allowing alternative composite liner design s for new CCR landfills, new CCR surface impoundments, lateral expansions, and retrofits of existing CCR surface impoundments, where the owner or operator provides certification by a qualified professional engineer that the alternative composite liner design mee ts the specified performance standard . Specifically, the alternative composite liner can consist of an alternative to the two feet of compacted clay with a hydraulic conductivity no greater than 1 x 10 - 7 cm/sec and a geomembrane upper component . The alte rnative lower component must be certified by a qualified professional engineer that the liquid flow rate through the lower component of the alternative composite liner is no greater than the liquid flow rate through two feet of compacted soil with a hydrau lic conductivity of 1x10 - 7 cm/sec . See section VI . F . 5 . c . of the preamble to the final rule for a further discussion on alternative liners. c . Use of a Composite Liner System Consisting of Two FMLs .56

Comment: The clay soils native to eastern Tennessee are ill - suited for compaction to this hydraulic conductivity . In order to achieve this performance, significant engineering and construction effort must be expended . In addition, substantial quality control and quality assurance must also be em ployed to assure compliance with this performance standard is achieved . However, Tennessee's industrial landfill regulations allow facilities to use liners that are demonstrated to provide equivalent or superior performance . As a result, industrial landf ills in the State have demonstrated that alternate designs which substitute a flexible membrane liner (FML) for the clay component of a composite liner system achieve compliance with the standards . E xperience has shown that construction of a composite lin er consisting of FMLs is approximately one - third the cost of constructing a composite liner consisting of an FML and clay . The commenter supports allowing facilities to use alternate designs for liner systems. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06880 - 7 Organization: Eastman Chemical Company (Eastman) Commenter Type: Other Company Comment : Florida requires a double liner system . The d ouble liner system consist s of upper and lower 60 - mil minimum average thickness HDPE geomembranes, with a primary leac hate collection and removal system lying above the upper geomembrane designed to limit the leachate head to one foot above the liner during routine landfill operations after placement of initial cover, except in sumps and leachate collection trenches; and a leak detection and secondary leachate collection system between the upper and lower liners . The lower geomembrane must be placed directly on a subbase which is a minimum six inches thick, is free of sharp materials or any materials larger than one - half inch, and has a saturated hydraulic conductivity of less than or equal to 1 x 10 - 5 cm/sec . A geosynthetic clay liner (GCL) with a hydraulic conductivity not greater than 1 x 10 - 7 cm/sec may be used in place of the six - inch thick sub - base layer provided it is placed on a prepared subgrade which will not damage the GCL . Florida has concluded that, if constructed in accordance with Florida’s Rule 62 - 701.400(3)(c), F.A.C., the double liner system is more protective of the environment than a composite liner installed in accordance with Rule 62 - 701.400(3)(b), F.A.C . Thus, in Florida, EPA’s proposed composite liner would be less protective than the liner systems currently in use . Florida has studied its EPA - approved double liner at least four times, each time finding the double liner system more protective than a composite liner.57

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10497 - 9 Organization: Seminole Electric Cooperative, Inc . (Seminole) Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10498 - 13 Organization: Florida Electronic Power Coordinating Group, Inc . (FCG) Commenter Type: Electric Utility Company Response: First, EPA does not agree that a composite liner consisting of two 30 - mil FMLs will provide equivalent protection as a composite liner consisting of a GM and two feet of compacted soil , or an alternative composite liner such as a GM over a GCL . While FMLs have t he advantages of extremely low rates of water permeation, the disadvantages of a composite liner consisting of two FMLs include leakage through occasional FML imperfections and punctures , potential for slippage along the interface between the FML s , and FML embrittlement over time . Furthermore, a critical component of a composite liner is the compacted soil or GCL component beneath the GM layer which will impede the flow of liquid that may leak through a hole or defect in the GM . This added protection is not achievable using two FMLs for the composite liner system . Additionally, the potential exists for liquid transport through the FMLs through holes caused by punctures, tears, flawed seams, etc . If a puncture occurs, the puncture could compromise both F MLs and create a conduit for liquid flow to underlying permeable soil . Moreover, a liner system consisting of two FMLs in contact with each other poses the risk of creating a slip plane that may compromise the stability of the disposal unit (although EPA acknowledges that using textured GMs would reduce or eliminate this risk) . These data are documented in EPA research . 6 Hence, t he alternative liner design must consist of two parts, an upper GM component and a lower component other than a GM , that is c ertified by a qualified professional engineer to meet the performance criteria of today’s rule . Regarding the double liner system required in Florida and described above, while this double liner system provides the advantage of a leak detection system b etween the two GMs, the lower composite liner consisting of a 60 - mil HDPE over six inches of soil with a saturated hydraulic conductivity of less than or equal to 1 x 10 - 5 cm/sec is not equivalent to a GM over two feet of compacted soil with a hydraulic conductivity of less than or equal to 1 x 10 - 7 cm/sec . To

6 “Assessment and Recommendations for Improving the Performance of Waste Containment Systems.” http://www.epa.gov/nrmrl/pubs/600r02099/600r02099.htm58

be hydraulically equivalent, soil with a hydraulic conductivity of 1 x 10 - 5 cm/sec would need to be on the order of 100 times thicker than soil with a hydraulic conductivity of less than or equal to 1 × 10 - 7 cm/sec . Similarly, a lower composite liner consisting of a 60 - mil HDPE over a GCL with a hydraulic conductivity not greater than 1 x 10 - 7 cm/sec would require a GCL thickness of 24 inches to be equivalent to a GM over two feet of com pacted soil with a hydraulic conductivity of less than or equal to 1 x 10 - 7 cm/sec . Therefore, EPA is finalizing a requirement in today’s rule that the lower component of the required single composite liner must be either two feet of compacted soil with a hydraulic conductivity no greater than 1 x 10 - 7 cm/sec or an alternative composite liner with a lower component that meets the performance standard described in section VI . F . 5 . C of the preamble to the final rule . EPA did not propose a double liner system requirement and, while today’s requirements are minimum requirements, states may impose additional requirements in addition to today’s requirements; e.g., a leak detection system overlain by a GM, if the state deems additional requirements are neces sary . d. Specific Use of Geosynthetic Clay Liners as an Alternative to the Composite Line r. Comment: Giroud (1997) conducted an empirical study in his technical article "Equations for Calculating the Rate of Liquid Migration Through Composite Liners Due to Geomembrane Defects . " The study yielded an equation that predicts the leakage rate from a composite liner with a defect in the geomembrane (e.g., installation damage) . For a given size defect, the main factor controlling the leakage rate is the hydraulic conductivity of the lower soil component . Based on the study results, it shows that a composite liner with a geomembrane and GCL with a hydraulic conductivity of 10 - 7 cm/s is expected to have a lower leakage rate than a composite liner with a ge omembrane and a two foot compacted clay liner with a hydraulic conductivity of 1 x 10 - 7 cm/s ec . CETCO requests that EPA’s final rule allow GCLs as an alternative to the low - permeability soil component underneath the FML. Comment Number: EPA - HQ - RCRA - 2009 - 0 640 - 06524 - 1 Organization: CETCO and University of Wisconsin Madison Commenter Type: Other Company Response : EPA has examined the performance of GCLs approved for use as alternatives to composite liners in municipal solid waste landfills. 7 The EPA report titled “Assessment and

7 “ Geosynthetic Clay Liners Used in Municipal Solid Waste Landfills,” http://www.epa.gov/wastes/nonhaz/municipal/landfill/geosyn.pdf ; “ Geosynthetic Clay Liners in Waste59

Recommendations for Improving the Performance of Waste Containment Systems,” 8 concluded that if a compacted clay liner ( CCL ) or GCL is used alone, liquid migration can occur over the entire area of the liner that is subject to a hydraulic head . The report also concluded that in a composite liner, leakage will only occur at the location of the GM hole, but it will be much slower than flow through an orifice due to the hydraulic impedance provided by the CCL or GCL . T he report cited above evaluated, among other qualities, the hydraulic efficiencies of a composite liner system comprised of a geomembrane (GM) liner over a GCL (GM/GCL) for 28 cells at seven landfills . Liner hydraulic efficiencies were reported between 97 % and 100% . However, the authors also reported potential stability problems with GCLs constructed on slopes greater than 10H:1V (5.7°), and that GCLs may not be appropriate for the disposal of liquid wastes or sludges . Taking all of this information into account, EPA believes that GM/GCL composite liners could offer a viable alternative to the geomembrane over compacted clay (GM/CCL) composite liner, but is not convinced that a GCL alone is a viable alternative to a composite liner . T his is because t he A gency is concerned that GCLs being much thinner than the two feet of compacted soil required for composite liners may allow for the flow of liquids through the GCL at a faster rate than through two feet of compacted soil . EPA , therefore, is addressing thi s concern by requiring that alternatives to the two feet of compacted soil have an equivalent or lower flow rate than two feet of compacted soil with a hydraulic conductivity no greater than 1x10 - 7 cm/sec . The flow rate comparison must be made using Darcy ’s equation for gravity flow through porous media described above . The hydraulic conductivity of the GCL must be determined using a recognized and generally accepted methodology, for example, ASTM Standard D6766 - 12, “Standard Test Method for Evaluation of Hydraulic Properties of Geosynthetic Clay Liners Permeated with Potentially Incompatible Aqueous Solutions,” ASTM International, West Conshohocken, PA, 2012 , DOI: 10.1520/D6766 - 12 , www.astm.org . Also, as Containment,” http://www.epa.gov/tio/tsp/download/2001_meet/prez/carson.pdf ; and “Assessment and Recommendations for Improving the Performance of Waste Containment Systems,” http://www.epa.gov/nrmrl/pubs/600r02099/600r02099.htm 8 “Assessment and Recommendations for Improving the Performance of Waste Containment Systems.” http://www.epa.gov/nrmrl/pubs/600r02099/600r02099.htm60

noted previously, t he design and construction of the alternative liner must be certified by a qualified p rofessional e ngineer. e . Use of a Lower Geosynthetic Clay Liner Below the Upper FML Component of a Composite Liner . Comment : EPA expressed reluctance in allowing alternative liners for new CCR disposal facilities . This reluctance appears to be due, in part, to the expectation that owners or operators would propose a soil liner alone in place of the entire prescribed composit e liner . We agree that a soil liner alone would not be as protective as the prescribed composite liner system, and should therefore not be considered an adequate substitute . We agree that an upper FML component is essential . However, there are other tec hnically feasible alternatives to the lower two foot compacted soil component that should be considered . Specifically, use of a geosynthetic clay liner (GCL) below the FML should be considered as an equivalent substitute for a compacted soil component . G CLs are factory - manufactured mats consisting of 0.75 lb/ft 2 of sodium bentonite clay between two geotextile layers, with a hydraulic conductivity of 5 x 10 - 9 cm/sec per ASTM D5887 . Due to their low hydraulic conductivity, GCLs are frequently used as a sub stitute for two - foot thick compacted soil liners in composite liner systems of many MSW landfills. Based on the technical information presented above, CETCO requests that EPA’s final rule allow GCLs as an alternative to the low - permeability soil component underneath the FML for both the proposed RCRA Subtitle C and Subtitle D composite liner options . As outlined above, EPA research has shown that GCLs provide equivalent or superior performance compared with compacted clay liners . GCLs have become the stat e of the practice for waste containment facilities . If GCLs are not allowed, then utilities will be forced to construct compacted clay liners at all sites, which could be cost - prohibitive, especially if a suitable clay source is not available nearby . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06524 - 1 & EPA - HQ - RCRA - 2009 - 0640 - 06195 - 2 Organization: CETCO and University of Wisconsin Madison Commenter Type: Other Company Comment: Based on the technical information referenced herein and additional EPA and other publications, GMA recommends that the US EPA CCR Disposal Proposed Rule for either of the Subtitle C and/or Subtitle D Regulation options define and require a ‘composite line r’61

consisting of two components: An upper component consisting of a minimum 60 - mil flexible membrane liner (FML), and a lower component consisting of a geosynthetic clay liner containing at least 0.75 lb/ft2 of sodium bentonite . If ‘composite liner’ is not redefined to include a lower component GCL, then at a minimum an alternative liner design should be provided Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 02340 - 1 Organization: Geosynthetic Materials Association Commenter Type: Trade Association Comment: GMA recommends that the USEPA CCR Disposal Proposed Rule for either the proposed Subtitle C and Subtitle D Regulation option be revised to define a ‘composite liner’ as consisting of two components: An upper component consisting of a minimum 30 - mil flexible me mbrane liner (FML), and a lower component consisting of either at least a two - foot layer of compacted soil with a hydraulic conductivity of no more than 1 x 10 - 7 cm/s, or a geosynthetic clay liner (GCL) containing at least 0.75 lb/ft2 of sodium bentonite . If ‘composite liner’ is not redefined to include a lower component GCL, then the allowance of an alternative liner design/system should be included. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 0 4 0 33 - 1 Organization: Geosynthetic Materials Association Commenter Type: Trade Association Comment: EPA's prescriptive one - design - fits - all approach is not suitable for all facilities, especially given the many local or regional variations in hydrology, geology, and other site characteristics. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09358 - 12 Organization: Interstate Power and Light Company (IPL) and Wisconsin Power and Light Company (WPL) Commenter Type: Electric Utility Company Comment: Given the vastly different site - specific characteristics of units across the country, there is no "one - size - fits all" approach when it comes to regulatory design standards for CCR disposal units . CCR sites "vary widely in terms of topographical, geological, climatological, and hydrological characteristics," any regulatory regi me must have the flexibility to tailor controls to the site - specific characteristics of the individual disposal units . There are alternate liner systems that can achieve the same level of protection as the composite liner62

system proposed by EPA . For exam ple, geosynthetic clay liner ("GCL") or similar systems can meet or exceed the performance standards of clay liners and certainly are equivalent or superior in some circumstances to two feet of compacted soil in the lower component of the composite liner s ystems proposed under the Subtitle D option . Therefore, in many circumstances, a liner system using the GCl in lieu of the two feet of compacted soil readily enables a CCR disposal unit to meet the applicable groundwater monitoring standards. Comment Numb er: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 8 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06203 - 13 Organization: Arizona Public Service Company (APS) Commenter Type: Electric Utility Company Response: EPA has reviewed the data provided with comments , as well as other technical reports and believes a composite liner comprised of a FML over a GCL is a viable alternative to a FML over a CCL , although we agree with the commenter that a GCL liner a lone would not be as protective as the prescribed composite liner system . Therefore, the final rule allow s alternative liner designs for new CCR landfills, new CCR surface impoundments, lateral expansion s of existing and new CCR landfills and when retrofi tting existing CCR surface impoundments . These alternative designs must consist of two parts, an upper FML component and a lower component having a flow rate no greater than that of two feet of compacted soil having a hydraulic conductivity no greater tha n 1x10 - 7 cm/s ec . The flow rate comparison must be made using Darcy’s equation for gravity flow through porous media described above . The hydraulic conductivity for the two feet of compacted soil used in the comparison shall be no greater than 1 x 10 - 7 cm/sec . The hydraulic conductivity of the GCL must be determined using a recognized and generally accepted methodology , for example, ASTM Standard D6766 - 12, “Standard Test Method for Evaluation of Hydraulic Properties of Geosynthetic Clay Liners Perme ated with Potentially Incompatible Aqueous Solutions,” ASTM International, West Conshohocken, PA, 2012 , DOI: 10.1520/D6766 - 12 , www.astm.org . Also, as previously noted, t he design and construction of the alternative line r must be certified by a qualified p rofessional e ngineer. f . Use of Clay Liners in Addition to Composite Liners .63

Comment : The use of engineered clay liners on existing solid waste units offers adequate protection without the extreme and unnecessary expense of excavating material from existing units and installing composite liners . The legislative history of the Bevill Amendment along with statements from the D.C . circuit court indicate that Congress directed EPA to install a regulatory program for CCR's that utilizes cost - effective controls and avoids imposition of undue regulatory costs on the electric utility industry if at all possible (EDF vs EPA, 852 F.2d 1309, 1315 (D.C . Cir . 1988 ) . Considering these directions and the proven performance of engineered clay liners, EPA should not require the installation of composite liners at existing units under a RCRA s ubtitle D CCR regulatory program . The Louisiana solid waste regulatory program required engineered clay liners having a coefficient of per meability no greater than l x l0 - 7 cm/sec, up until the rule was modified in 1993 , after which new surface impoundments were required to have either composite liners or alternative liners that provide equivalent groundwater protection . Groundwater monitoring over the course of years has shown that there has been no adverse impacts to groundwater from the commenter’s surface impoundments that used engineered clay liners . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06868 - 7 Organization: Cleco Co rporation Commenter Type: Electric Utility Company Comment : T he long term performance of clay liners containing CCR wastes is not well understood at the present time . It is possible that some constituents in the wastes, such as salt, will desiccate a clay liner and produce cracks in the clays that would serve as a pathway for the migration of CCR wastes from the containment structure into the environment . In addition, a risk assessment would only typically give consideration to the current value or use of a resource, such as ground water with a high saline content, and not the potential future value and use of the resource that may be enhanced by technological treatment advances in the future. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06313 - 104 & 105 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Information related to the field performance of compacted clay liners is readily available in the literatur e, including the aforementioned, “Assessment and Recommendations for Improving the Performance of Waste Containment Systems”, R . Bonaparte, D.E . Daniel, and64

R.M . Koerner, EPA/600/R - 02/099, EPA National Risk Management Research Laboratory, Cincinnati, OH, http://www.epa.gov/nrmrl/pubs/600r02099/600R02099 . In chapter 4 of this document, researchers evaluated a database of 89 compacted clay liners and test pads . The study found that although all 89 liners in the database were designed and constructed to meet a field hydraulic conductivity of 1 x 10 - 7 cm/s ec , this value was not met at more than one - fourth (26 percent) of the sites in the database . In other words, one - fourth of the compacted clay liners in the database could experience greater leakage in the field than initially modeled. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06195 - 2 Organization: CETCO Commenter Type: Other Company Response : Upon further consideration, EPA is finalizing today’s rule to allow owners or operators of existing CCR landfills and surface impoundment with a clay liner to continue to operate these disposal units for the reminder of their useful life . Based on the results of EPA’s risk assessments, the Agency has determined that CCR disposal units that have a clay liner and that meet the technical requirements in the rule, i.e., the groundwater monitoring and corrective action requirements, and the closure and post closure care requirements, will be protective of human health and the environment . However, as explained in section VI.F.3.a above, unlined surface impoundments that are leaking are required to close in accordance with the closure requirements in §257.10 2 of today’s rule. g . Alternative Liners Only in States with Permitted Programs . Comment : Alternative designs should only be allowed in states with regulations for permit application review, public notice and an opportunity for hearings . EPA could craft a regulation requiring that these alternatives only be allowed in states with RCRA s ubtitle D permitting progr ams equivalent to that required for delegation of authority for MSW landfills, found at 40 CFR 239 . There would be no need for the actual EPA delegation of authority, but the rule would give a framework to use for such requests. Comment Number: EPA - HQ - RCR A - 2009 - 0640 - 06260 - 80 Organization: Kentucky Department for Environmental Protection Commenter Type: State Government Response : The Agency disagrees . To support a standard under section 1008(a) or 4004(a) EPA is required to prove that the rules will be protective based on the record available at65

the time the rule is promulgated . In the absence of a record demonstrating the adequacy of state programs, EPA cannot simply rely on subsequent state action to demonstrate that a particular requirement will meet the 4004(a) standard . As discussed in Section IV of the preamble to the final rule , the mere existence of the provisions mentioned by the commenter does not prove the adequacy of the state program, but also by how the state implements the requirements (e .g., when and how are variances or exemptions granted) . And as discussed in that section, EPA lacks sufficient information to make any determination on many state programs . By contrast, we have determined, based on the available information, that alterna tive composite liner designs can be as protective as the composite liner design in the proposed rule, provided a qualified professional engineer certifies that the alternative to the two feet of compacted soil has a flow rate no greater than that of two feet of compacted soil having a hydraulic conductivity no greater than 1 x 10 - 7 centimeters per second . (See the previous Response to Comments for further discussion.) h . P erformance - based Standards . Comment: Any design standard should be made performance - based rather than prescriptive to provide for flexibility in design and construction . P erformance - based standards should be allowed to supplement def ault, prescribed engineering standards and there are infinite site variables that can allow for flexibility in design and not require specific liner types but still meet the goal addressing hydraulic conductivity to protect human health and the environment . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 08850 - 13 Organization: L ansing Board of Water & Light (BWL) Commenter Type: Electric Utility Company Comment: By establishing performance standards to be met, a framework allowing for innovation, incorporation of developing “best practices” and site --- specific solutions is promoted . This approach can result in solutions that are not only more cost --- effective, but can also provide better protection of property and the environment, in view of the specific site conditions encountered . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06831 - 2 Organization: MACTEC Engineering and Consulting, Inc. Commenter Type: Other Company66

Comment: Change the definition of “ composite liner ” from “....and the lower must consist of at least two - foot layer ( sic ) of compacted soil with a hydraulic conductivity of no more than 1x10 - 7 cm/sec” to read as follows: “.. . and the lower component must consist of or be equivalent or superior to a two - foot layer of compacted soil with a hydraulic conductivity of no more than 1x10 - 7 cm/sec.” Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06529 - 40 Organization: NiSource Corporate Services Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06532 - 34 Organization: Southern Illinois Power Cooperative Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09239 - 68 Organization: Prairie State Generating Company, LLC (PSGC) Commenter Type: Electric Utility Company Comment: Providing an alternative standard to address circumstances where the requirement is highly dependent on site - specific conditions is appropriate when mechanisms are in place to ensure that the alternative is protective of health and the environment . Certification by a registered professional provides an appropriate level of certainty that the performance standard is being met . In addition, notification would be provided to the state and the public such that enforcement could be pursued if necessary . Using sound science and engineering princi ples to develop a disposal design is a more prudent approach rather than an across the board regulatory mandate regardless of the environmental parameters that need to be considered when designing a disposal site . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06 529 - 40 Organization: NiSource Corporate Services Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06532 - 34 Organization: Southern Illinois Power Cooperative Commenter Type: Electric Utility Company67

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09239 - 68 Organization: Prairie State Generating Company, LLC (PSGC) Commenter Type: Electric Utility Company Comment: E stablishing performance standards would give flexibility to tailor a system to meet the site - specific character istics of an individual disposal unit . These would include topographical, geological, climatological, and hydrological characteristics . EPA should not limit alternative liner design systems and deny owners/operators the ability to utilize systems that ar e equally or more protective as the composite liner system proposed in the Subtitle D options . Additionally, due to the significant volume of clay that is needed to line a facility, as well as the likelihood that other units would need the same materials in the same timeframe, there may be an insufficient supply of clay and/or it may be difficult to transport the needed volume of clay to the site. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06833 - 20 Organization: Dominion Resources Services, Inc. Commenter Type: Electric Utility Company Comment: Given that CCR sites “vary widely in terms of topographical, geological, climatological, and hydrological characteristics,” any regulatory regime must have the flexibility to tailor controls to the site - specific charac teristics of the individual disposal units . Otherwise, the same concerns with over - regulation that EPA correctly described with respect to a Subtitle C program will arise under a Subtitle D nonhazardous waste program for CCRs . For example, it is not nece ssary to require the installation of a composite liner system to a lateral extension of an existing CCR landfill in the arid Southwest where the distance to groundwater may be several hundred feet or more . There are alternate liner systems that can achiev e the same level of protection as the composite liner system proposed by EPA. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06198 - 8 Organization: Ameren Corporation Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06203 - 13 Organization: Arizona Public Service Company (APS) Commenter Type: Electric Utility Company68

Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06956 - 13 Organization: Tri - State Generation & Transmission Commenter Type: Electric Utility Company Comment Number: EPA - HQ - R CRA - 2009 - 0640 - 09536 - 9 Organization: Tennessee Valley Authority Commenter Type: Electric Utility Company Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 10483 - 53 Organization: Utility Solid Waste Activities Group (USWAG) et al. Commenter Type: Trade Association Comment: As landfill designers, we have successfully designed, permttted, and constructed numerous Subtitle D Landfill Sites utilizing geosynthetic clay liners with site soils, and believe that the proposed coal ash landfill regulations should include lan guage to incorporate equivalent or superior liner designs. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 05825 - 1 Organization: TriAD Environmental Consultants, Inc. Commenter Type: Other Company Comment: Alternative liner designs based upon specific performance standards referenced in 40 CFR Part 258.40 should also be recognized. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06723 - 21 Organization: West Virginia Department of Environmental Protection (WVDEP) Commenter Type: State Government Comment: T he Subtitle D option must provide flexibility in the design of new disposal units and provide performance standards to be met . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 09284 - 52 Organization: Virginia Department of Environmental Quality Commenter Type: State Government Comment: The final rule should include the flexibility to use alternatives to composite liners that are demonstrated to achieve the same long - term performance standards. Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 07048 - 12 Organization: TransAlta Centralia Gene ration Commenter Type: Electric Utility Company69

Comment: N o performance standards should be permissible since state agencies might adopt weak performance standards that would not be adequate to protect human health and the environment . Major s tate regulatory failures, such as those identified by EPA and others, indicate that this is a likely scenario (USEPA, 2007; Environmental Integrity Project and Earthjustice, 2010; Environmental Integrity Project, Earthjustice, and Sierra Club, 2010) . Comment Number: EPA - HQ - RCRA - 2009 - 0640 - 06313 - 104 Organization: Earthjustice et . al. Commenter Type: Advocacy Group Response : For the reasons discussed previously, the final rule incorporates a performance standard for the composite liner requirement allowing alternative liner designs for new CCR landfills, new CCR surface impoundments, retrofits of existing surface impoundments, and any lateral expansion provided the owner or operator provides certification by a qualified professional engineer that th e lower component of the alternative composite liner has an equivalent or lower flow rate as two feet of compacted soil with a hydraulic conductivity no greater than 1 x 10 - 7 centimeters per second .