1 The NSWMA letter was postmarked January 30, 2002 but was not received by EPA until mid February. Receipt of this letter by EPA may have been delayed due to the irradiation of mail that was being sent to Federal offices in Washington, DC.

Virginia Bioreactor Project XL Landfills  Response to Comments  Page 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY PROJECT XL VIRGINIA BIOREACTOR PROJECT XL LANDFILLS RESPONSE TO COMMENTS May 13, 2002 Introduction The purpose of this document is to present comments and EPA's responses to comments on a proposed Project XL Site Specific Rule for Implementing Waste Treatment Systems at Two Virginia Landfills that was published in the Federal Register on December 28, 2001.

Background On December 28, 2001, EPA requested comments on the proposed rule for the Project XL Site Specific Rulemaking for Implementing Waste Treatment Systems at Two Virginia Landfills (see 66 FR 67152). The proposal was to provide regulatory flexibility under the Resource Conservation and Recovery Act (RCRA), as amended, at two Virginia landfills: the Maplewood Recycling and Waste Disposal Facility, located in Amelia County, Virginia (Maplewood Landfill); and the King George County Landfill and Recycling Facility, located in King George County, Virginia (King George Landfill). The Maplewood Landfill is owned and operated by USA Waste of Virginia, Inc., and the King George Landfill is owned by King George County and operated by King George Landfills, Inc. USA Waste of Virginia, Inc. and King George Landfills, Inc. are both subsidiaries of Waste Management, Inc., and will be referred to collectively as "Waste Management". Maplewood Landfill and King George Landfill, both of which are municipal solid waste landfills (MSWLFs), will be referred to collectively as the "Virginia Project XL Landfills".

As a result of the December 28, 2001 proposed rule for the Virginia Project XL Landfills, EPA received two comment letters. The National Solid Waste Management Association (NSWMA) provided comments in a letter dated January 28, 2002 1 . The NSWMA supported the 2 According to the Federal Register Notice the comment period for the proposed rule closed on January 28, 2002. EPA was contacted via telephone by NRC on January 28, 2002 and agreed to include their comments in the record and docket but to designate them as late.

Virginia Bioreactor Project XL Landfills  Response to Comments  Page 2 project and did not call for any revisions. The NSWMA comment letter states, "NSWMA's Landfill Institute supports the Project XL bioreactor landfill projects proposed for the Maplewood Landfill and the King George Landfill in Virginia as proposed in the Federal Register on December 28, 2001 (66 FR 67152)". EPA acknowledges the NSWMA comments; no response is necessary.

The National Recycling Coalition, Inc. (NRC) provided comments in a letter dated February 1, 2002. 2 EPA's complete and detailed response to these comments is contained below. Generally, some of the NRCs comments addressed the legal basis or adequacy of EPA's existing municipal solid waste landfill (MWSLF) criteria, 40 CFR Part 258. EPA requested and received comments on Part 258 prior to its issuance, and addressed these comments in the preamble at the time of its publication. See 56 Fed. Reg. 50978, October 9, 1991. In any event, the NRC's comments on the Part 258 MSWLF Criteria itself are beyond the scope of this rulemaking. Other NRC comments called for EPA to establish uniform design and operating criteria for all bioreactor landfills. These comments are also beyond the scope of this rulemaking, which addresses only the Maplewood and King George County landfills. NRC's comments also addressed the adequacy of landfill gas monitoring, collection, control and reporting requirements for the XL Project. The proposed rule did not provide any flexibility to existing regulations addressing these requirements, therefore these comments are also beyond the scope of this rulemaking. Finally, the NRC submitted comments on suggested testing changes for the XL Project. EPA has carefully considered these comment and suggestions and discussed them with the Virginia Department of Environmental Quality and Waste Management and their consultant in a number of phone calls and a meeting and site visit to the landfills. EPA believes the monitoring, testing and reporting requirements contained in this rule, the Final Project Agreement (FPA) and the State solid waste and air permits will provide sufficient information to characterize the bioreactor operations at the Virginia Project XL Landfills and protect human health and the environment. Therefore, no changes have been made to the proposed rule. The remainder of this RTC document responds in detail to comments submitted by the NRC in their letter.

EPA Responses to National Recycling Coalition Comments on the Virginia Project XL Landfills Proposed Rule Virginia Bioreactor Project XL Landfills  Response to Comments  Page 3 Executive Summary 1. Comment: The "superior performance" of the bioreactor design cannot be met in comparison to the dry tomb standards in current regulations because those are fatally flawed and in violation of the Resource Conservation and Recovery Act.

Response: Comments regarding the legal basis or adequacy of EPA's current municipal solid waste landfill (MWSLF) criteria are beyond the scope of today's rulemaking. EPA promulgated regulations implementing sections 1008( a)( 3), 4004( a) and 4010( c) of the Resource Conservation and Recovery Act (RCRA) in 1991, in accordance with the requirements of the Administrative Procedure Act. The time limit for challenging part 258 has long since passed, and this rulemaking did not reopen part 258 for comment or review. There is no basis for the commenters statement that the regulations are "fatally flawed" or that they violate RCRA.

For purposes of the XL Project that is the subject of today's rule, the part 258 criteria are the only basis for evaluating whether this project meets the "superior performance" criterion of Project XL. Under Project XL, EPA may provide project specific flexibility to existing rules, regulations and guidance provided the project meets all the Project XL criteria. As set forth in the Final Project Agreement http:// www. epa. gov/ ProjectXL/ virginialandfills/ page1. htm, EPAhas determined that this project meets the "superior environmental performance" criteria.

2. Comment: The artificial cost collar imposed on the design and operation of the bioreactors in order to keep their net costs less than those of dry tomb landfills effectively prioritizes costs over economics (sic), and, this too, is impermissible under law.

Response: The commentor assumes a "cost collar" but it is unclear what the commentor means by this term. As stated in the preamble to the proposed rule, Project XL includes "cost savings and paperwork reduction" as one of eight criteria for determining whether a project proposal should be accepted, along with "superior environmental performance," and " avoidance of shifting risk burden" to name two others. 66 Fed. Reg. 67154. EPA disagrees that the proposed rule, or the XL project to which it applies, prioritizes costs over environmental protection.

3. Comment: EPA must establish uniform protocols for any XL or Cooperative Research and Development Agreement (CRADA) bioreactor tests to insure that the designs provide additional layers of conservatism to make this type of landfill "fool proof" and the tests produce all relevant information with statistical techniques for reliability.

Response: EPA is currently supporting bioreactor testing under the Project XL and CRADA programs. EPA disagrees that the Agency should establish "uniform protocols" for testing bioreactor technology under these programs. The monitoring requirements for each program and the projects under these programs are similar, but not the same. Each project is slightly different and therefore the requirements differ somewhat. However, there are common requirements of bioreactor projects under Project XL and CRADA to ensure that these projects do not pose an Virginia Bioreactor Project XL Landfills  Response to Comments  Page 4 unreasonable risk to human health and the environment. For example, all the projects require the monitoring of the leachate head on the liner as well as leachate quality and quantity, landfill gas composition and quantity collected, moisture and temperature sensors, waste characteristics as it changes over time, waste settlement as well as ground water quality. Furthermore, as EPA stated in its notice modifying its Guidance for Project XL, 62 Fed. Reg. 19872 (April 23, 1997), EPA expects data and experiences that will help the Agency make sound decisions as we look for ways to improve the current regulatory system." The Federal Register notice also explained that another of the objectives of Project XL is to "transfer successful approaches into the current system of environmental protection." If EPA decides in the future that the federal municipal solid waste landfill criteria in part 258 should be amended to allow more widespread implementation of bioreactor technology, the information learned from various approaches in Project XL and CRADA projects will be the basis for determining what uniform criteria should apply.

4. Comment: Among the design changes that the NRC believes ought to be included in protocols are: pre shredding the incoming waste load; lighter in place compaction of the waste load; double composite liners; 4: 1 side slopes; and greater redundancy in leachate collection lines.

Response: It is important to note that the tests cells in the Project XL bioreactor landfills are already constructed, have been filled with waste and are no longer actively receiving waste. EPA does not believe that any design changes are required for the Virginia Project XL Landfills in order to conduct the bioreactor testing at these sites. Bioreactor operating and testing requirements for the XL Project are described in the FPA, the Final Site Specific Rule and the VADEQ solid waste and air permits for the Virginia Project XL Landfills. As previously stated, one purpose of this XL project is to test and compare various design elements to determine what design criteria should apply generally to bioreactors, if EPA decides in the future to amend part 258. Since the waste is already in place in the bioreactor test cells EPA does not agree that preshredding or lighter in place compaction could or should be required for this XL project. See response to Comment 13 (a) regarding pre shredding of waste and Comment 13 (b) regarding compaction. There is an existing double (and in the case of the King George Landfill a triple) synthetic liner under the Virginia Project XL Landfill cells. See response to Comment 13 (c) regarding composite liners. A slope stability analysis was conducted for both landfills and considered the effect of bioreactor operations in the test cells. The slope stability analysis for both landfills was determined to exceed the value of 1.5 recommended by EPA. See response to Comment 13 (d) regarding side slopes. The existing design of the leachate collection systems provides for redundant drainage as is explained in the response to Comment 13 (e) below.

5. Comment: Among the test changes that the NRC proposes are: statistical sampling of bore samples to produce reliable data on site stabilization and gas emissions; and in line camera surveys of the leachate collection lines.

Response: The proposed rule states the operator of the landfill shall collect representative samples of the landfill waste in the test areas on an annual basis and analyze the samples for the following solid waste stabilization and decomposition parameters: Moisture Content, Biochemical Virginia Bioreactor Project XL Landfills  Response to Comments  Page 5 Methane Potential, Cellulose, Lignin, Hemi cellulose, Volatile Solids and pH. EPA believes that the testing agreed to in the Final Project Agreement will provide reliable and representative data on site stabilization and gas emissions. The monitoring and testing requirements specified in the proposed rule go beyond the requirements specified in existing regulations. See response to Comment 14 regarding waste stabilization and Comments 13 (f) and 15 regarding gas emission. The proposed requirements regarding monitoring and testing reflect what was agreed to by the stakeholders in the Final Project Agreement (FPA) which was announced for public comment on September 8, 2000 (65 Fed. Reg. 54520). The commentor did not submit comments on the proposed FPA.

I  Correction of the Fundamental Assumption 6. Comment Summary: Misreading of Superior Performance Criteria (page 5)

The commentor states that because the current landfill rules in 40 CFR part 258 are the baseline against which to evaluate whether this XL project meets the "superior performance" criteria, "whole sections of [the Final Project] Agreement (FPA) "must be largely revamped." The commentor also argues that "the problem with simply following" the `Superior Environmental Performance' criteria guideline in this case is that it does not take into consideration "whether EPA's current rules that are otherwise applicable protect the environment."

Response: This comment is beyond the scope of this rulemaking. See response to Executive Summary, Comment 1 above.

7. Comment Summary: Systemic Long Term Fallacy of Dry Tomb Designs (pages 5 8)

The commentor argues that because landfill liners "will ultimately fail" EPA rules which include "dry tomb" designs violate RCRA and should not be used as the baseline for this rulemaking. The commentor cites several sources which describe the rules prescribing "dry tomb" landfills as protecting the environment initially, but as also failing to address the long term potential for leakage of leachate and landfill gas.

Response: These comments are beyond the scope of today's rulemaking, as they question the existing rules and not today's rulemaking. See Response to Comment 1 above. However, EPA notes that the commentor's arguments in fact support today's rule. This site specific rule is intended to allow for the testing of technologies that, if successful, may be useful in reducing the long term risks from MSWLFs. As stated in the proposal, "Several studies have shown that leachate quality improves over time when leachate is recirculated on a regular basis. For all of these reasons bioreactors are expected to decrease potential environmental risks and costs associated with leachate management, treatment and offsite disposal. Additionally, use of bioreactor techniques is expected to shorten the length of time the liner will be exposed to leachate and this should lower the long term potential for leachate migration into the subsurface environment. Bioreactors are also expected to reduce post closure care costs and risks, due to the Virginia Bioreactor Project XL Landfills  Response to Comments  Page 6 accelerated, controlled settlement of the solid waste during landfill operation. Finally, bioreactors provide for greater opportunity for recovery of methane gas for energy production since a larger quantity of methane is produced earlier than in a normal MSWLF." 66 FR 67155.

8. Comment Summary: Other Short Term Design Failings (page 9 13)

(a) Air Emissions.

"Chief among them is the issue of air emissions from landfills. The impression that has been left is that the regulation in 40 CFR Part 60 Subpart WWW, requiring a piping system intended to extract gas in large landfills, resolves concerns over landfill gas emissions. Those regulations do not, however, create any emission's limit other than certain piping design requirements. Notwithstanding that fact, the Agency has assumed that the collection efficiency is 75%, without any factual basis for that conclusion." The commentor provides information regarding variations in landfill gas collection efficiencies and reasons for this variation. The commentor also noted that "EPA rules mandating the installation of gas collection systems only covered 54% of the waste in the ground in 2000 ..." andcommentedonthecontributionof landfill gases to global warming and distribution of mercury and other hazardous compounds into the atmosphere.

Response: Similar to the commentor's statements regarding the adequacy of the existing MSWLF criteria in 40 CFR part 258, the comments in this section address the adequacy of existing regulations implementing the Clean Air Act at 40 CFR part 60 Subpart WWW. These comments are beyond the scope of today's rulemaking. Neither today's rule nor this XL project as a whole, provide for any flexibility regarding landfill gas monitoring, collection and control required by existing regulations. This project must comply with all applicable existing air regulations. As discussed in the preamble to the proposed rule, Waste Management's obligations with respect to landfill gas will be set forth in a Federally Enforceable State Operating Permit (FESOP). (66 FR 67157) The Virginia Department of Environmental Quality (VADEQ) is the regulatory agency which, under the federal Clean Air Act, has air permitting authority for both landfills. The VADEQ was a major stakeholder in the XL Project and has issued a New Source Review Permit 9 VAC 5 80 10 (NSR) for the King George Landfill which contains the enforceable parameters and requirements implementing the New Source Performance Standards (NSPS) regarding gas collection, control and monitoring. In addition, on July 31, 2001, VADEQ issued a Title V Operating Permit 9 VAC 5 80 50 et. seq. (Title V), for the King George Landfill. Both the Title V permit and the underlying NSR permit issued by VADEQ are considered Federally enforceable. An NSR Permit for the Maplewood Landfill is under development. An NSR Permit will be in place for each landfill prior to the addition of liquids. It is important to note that an active gas collection system is already in place and operating at both landfills. Details on the piping system for the LF gas extraction system are contained in the monitoring plan in the NSPS permits for the landfills. There is currently beneficial reuse of the LF gas at the Maplewood LF which is used for energy production and WM is working towards the beneficial reuse of the methane from the King George LF. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 7 (b) Leachate Collection Systems "A continuing threat to the ability of these systems to remove excess liquids is the problem of clogging of the pipes from microbial action and clog materials, exacerbated by organic matter and calcium concentrations in the waste load. That is the reason why it is absolutely essential that these lines be cleaned out at least annually for as long as the site remains biologically active in order to preserve their functionality.

"However, the ability to clean out the collection pipes becomes substantially more difficult as the length of the pipes, and the number of joints and the problems laying the segments in a straight line, increases. Yet, to our knowledge, EPA has never undertaken any systematic technical review to validate the maximum length which collection pipes can be reliably cleaned out overtime.... Combinedwithsteep3: 1, insteadof4: 1, sideslopes, thesedesignchangeshave facilitated the construction of mega landfills covering thousands of acres, hundreds of feet high. . . . . Moreover, so far as we are aware, neither has any regulatory consideration been given to how a clogged line would be repaired in a mega fill that would require digging out a cone shaped cavity through hundreds of feet of garbage to provide clearance for workers to access the clogged pipe segment."

Response: This comment is beyond the scope of today's rulemaking. Today's rulemaking concerns only the site specific requirements for operation of specific existing cells in the King George and Maplewood landfills as bioreactor landfills. The commentor's complaints about leachate collection systems are general in nature. Existing regulations (40 CFR 258.28( a)( 2)) allow leachate recirculation in MSWLFs that meet the design specifications in section 258.40( a)( 2), which include the requirement of a leachate collection system that can ensure a hydraulic head (leachate layer) above the liner of 30 centimeters (cm) or less, i. e. approximately 12 inches.

With respect to this proposal, the requirement of maintaining less than 30 cm of head on the liner in specifically included (40 CFR 258.41( c)( 1)). Waste Management will not be allowed to add liquids if the requirements for the head on the liner are exceeded. EPA does not agree that it is necessary to specify how such a leachate collection system must be designed. It is the responsibility of the landfill owner/ operator to comply with the leachate control requirements regardless of the length of pipes or number of joints.

(c) Monitoring Wells. "EPA requires groundwater monitoring wells in order to detect leakage before it reaches groundwater, generally 150 meters from the direction the groundwater will flow from the landfill and no more than 200 feet apart." The commentor argued that monitoring wells as much as 200 feet apart have an exceedingly low probability of detecting a leak from "a typical two foot long tear or rip . . . in a sand aquifer system" that would only be expected "to spread laterally about ten feet within 150 meters of the source."

Response: This comment is beyond the scope of today's rulemaking. Today's rulemaking Virginia Bioreactor Project XL Landfills  Response to Comments  Page 8 concerns only the site specific requirements for operation of specific existing cells in the King George and Maplewood landfills as bioreactor landfills. These comments concern the commentor's view of the existing MSWLF criteria with respect to detection monitoring requirements and do not address today's rulemaking.

With respect to today's rule, the Project sponsor did not request any regulatory flexibility with regard to groundwater monitoring at the Virginia Project XL Landfills. Waste Management is required to comply with all existing regulations for ground water monitoring at the two sites. EPA considers groundwater monitoring an important indicator for monitoring environmental impact. As of February 2002 there are 12 monitoring wells at the Maplewood Landfill and 14 monitoring wells at the King George County Landfill. The wells are sampled on a quarterly basis. The state solid waste permit contains complete information on the ground water monitoring programs at the Virginia Project XL Landfills. EPA has added figures to the docket for this rule that depict the ground water monitoring well locations on the Virginia Project XL Landfill properties.

9. Comment Summary: Proper Base Line Assumption for Bioreactor Designs and Tests (page 14)

"The design must be determined not on the basis of whether it poses less of a threat to the environment than current rules, but rather whether "there is no reasonable probability of adverse effects on health or the environment from disposal of solid waste" under the modified rules, regardless of whether the threat is less." It must be structured so as to provide reliable data on which to pattern new rules that would be applicable to all applicants for landfills after the discredited dry tomb standards are repealed.

Response: See response to Executive Summary, Comment 1. The criteria in part 258 set out the requirements that implement section 4004( a) of RCRA based on a determination that "there is no reasonable probability of adverse effects on health or the environment from" facilities meeting these requirements. The part 258 criteria are the proper and only basis for evaluating whether this project meets the "superior performance" criterion of Project XL. Today's rulemaking is for the purpose of implementing this project as two specific landfill sites and is not a rule to define, as a general rule, the requirements applicable to all bioreactor landfills.

II Proposed Changes in Bioreactor Design and Operation 10. Comment: A reading of the technical documents in this docket provides little inkling of the urgent need for any special care in the design or operation of a bioreactor. But, as explained below, we vigorously disagree with this characterization and, because of the actual real world problems in bioreactors, we strongly urge that the conditions of their design and operation be made foolproof. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 9 Response: The commentor misconstrues the purpose of today's rule. EPA is not promulgating a rule setting forth generally applicable design and operation criteria for bioreactor landfills. Rather, today's rulemaking is a site specific rule to allow specified techniques to be tested at particular existing landfill facilities. Based on the technical support documents and the Project XL proposal information contained in the Docket for this proposed rule including the Slope Stability studies for the test cells that will be operated as bioreactor landfills (Docket Numbers 4. 5 and 4.6), EPA believes that today's rule is protective of human health and the environment. Furthermore, the monitoring and testing requirements in the rule will allow for evaluation of the processes taking place in the test cells and provide EPA with detailed information on bioreactor operations. As the commentor notes, bioreactors are currently operating in different locations in the United States. Table 2 in the FPA contains a Summary of Field Scale Leachate Recirculation and Bioreactor Projects. Numerous technical writings on the subject show that safe and effective operation is achievable. The commentor rightly states that technical challenges remain, and bioreactors can be operated improperly. This need can be answered, in part, by projects like this one that will provide additional data on bioreactor operations under measured and controlled conditions.

11. Comment Summary: Advocate Role Inappropriate (pages 15 16)

The commentor notes that EPA listed six reasons why bioreactor technology will provide environmental benefits but did not acknowledge any of the numerous and widely recognized problems of bioreactors. The commentor believes that the record creates the impression that EPA is acting as an advocate for an untested and highly controversial technology. The commentor views EPA's decision to approve the Virginia Project XL Landfills as a product of combined function of promotion and regulation, which the commentor believes is contrary to EPA's obligation to independently and objectively evaluate each application on its merits.

Response: EPA objectively evaluated the project XL proposal for the VA landfills project and determined that the project meets the criteria for acceptance under Project XL. The basis for EPA's determination with respect to this project is set out in a Letter to Waste Management, Inc from Thomas C. Voltaggio, regarding selection of the Waste Management, Inc. Project XL Proposal, August 3, 2000 and in the Final Project Agreement. The August 3, 2000 Letter is in the Docket for this rule and posted on the EPA website at: http:// www. epa. gov/ ProjectXL/ virginialandfills/ voltaggio. pdf. The draft FPA was made available for public review and comment (65 FR 54520, Sept. 8, 2000). The FPA is also contained in the Docket for this rule and is posted on the EPA website at: http:// www. epa. gov/ ProjectXL/ virginialandfills/ fpa. pdf. The commentor did not submit comments on the draft Final Project Agreement (FPA) in response to the Agency's Notice of Availability of the FPA and solicitation of public comments. Nevertheless, EPA disagrees that its approval of the Virginia Project XL Landfills project was inappropriate, nor does EPA agree that it's role is one of advocacy. As explained in the above Federal Register notice concerning the FPA, Project XL "gives regulated entities the opportunity to develop alternative strategies that will replace or modify specific regulatory requirements on the condition that they produce greater Virginia Bioreactor Project XL Landfills  Response to Comments  Page 10 environmental benefits." As further explained in the preamble to the proposed site specific rule for this project, "these efforts are crucial to the Agency's ability to test new regulatory strategies that reduce regulatory burden and promote economic growth while achieving better environmental and public health protection." 66 FR 67154.

By promulgating today's rule, EPA is not advocating the wide spread use of bioreactor landfills for MSW waste. Promulgation of a site specific rule to allow an alternative approach in the context of a given XL project is not an indication that EPA plans to adopt that approach as a general matter. It would be inconsistent with the forward looking nature of these pilot projects to adopt such innovative approaches prematurely on a widespread basis without first determining whether or not they are potentially viable in practice and successful for the particular projects that embody them.

Alternative policy approaches and/ or interpretations, on a limited, site or state specific basis and in connection with a carefully selected pilot project, is consistent with the expectations of Congress about EPA's role in implementing the environmental statutes (so long as EPA acts within the discretion allowed by the statute). Congress recognizes that there is a need for experimentation and research, as well as ongoing reevaluation of environmental programs, is reflected in a variety of statutory provisions, e. g., Sec. 8001 of RCRA, (42 U. S. C. 6981).

12. Comment Summary: Special Challenges of Bioreactors (pages 16 17)

"In order to attempt to accelerate decomposition in the ground, the moisture content and temperature of the waste load must be doubled, increasing the weight of the waste load by approximately one third, in an unstable and dynamic state in which there is differential settlement on the bottom liner, the possibility of anticipated seepages threatening side wall stability, the complexity of achieving adequate gas extraction, and so on." The commentor summarized two instances where breaches occurred in landfills where liquids were being recirculated.

Response: EPA is aware of the issues mentioned above as being concerns for the operation of bioreactor landfills. It is for these reasons that EPA and the other stakeholders have agreed to evaluate this technology and gather data on these issues at the Virginia Project XL Landfills and other Project XL bioreactor landfill test sites.

EPA agrees that careless injection of large quantities of leachate could lead to slope stability problems and these issues must be taken into account at all phases of bioreactor operation. See the response to Comment 13 B, 13 D and 13 G regarding compaction, side slope and buffer zones below.

Waste Management has installed temperature monitoring wells in several locations and depths throughout the test areas at both landfills and will be monitoring and recording the temperature at these locations. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 11 Based on the volume and density of waste measured in the test areas and the volume and mass of liquid that is proposed to be added to the Maplewood and King George Landfills on an annual basis, it is calculated that the weight of waste in the test areas would increase by 1. 7% and 2. 6% at the Maplewood and King George Landfills, respectively (Site Visit to Maplewood and King George Landfills).

In addition to the two landfill failures cited by the commentor, there are several other bioreactor landfills that are operating without incident. They include Yolo County in California; Florida Center for Solid and Hazardous Management, Bioreactor Landfill Demonstration Project; Outer Loop Landfill in Kentucky and the Delaware Solid Waste Authority, Sussex Landfill which historically recirculated leachate. Table 2 in the FPA contains a Summary of Field Scale Leachate Recirculation and Bioreactor Projects. Technical results of this project coupled with other landfill bioreactor projects will lead to design and operational guidance that the commentor desires.

Finally, this rule is only allowing bioreactor landfill operations at two test locations in Virginia. This rule is not meant to address all design concerns for a bioreactor landfill and they are clearly not meant to "serve as the basis for the second generation landfill".

13. Comment Summary: Need to Upgrade Dry Tomb Specifications for Bioreactors (pages 18 23)

The commentor stated that for a rule change for the second generation landfill design that would be applied across thousands of facilities over time, a heightened level of additional conservatism, beyond that in dry tomb design, must be built into bioreactor design specifications, and that this contrasts with the cost constraint on bioreactor design specifications incorporated into the VA landfills project. The commentor advocated that EPA set up a generic docket for conducting an investigation that can provide a factual basis to set up a generic protocol with which to evaluate project applications and compare results of various experiments. The commentor also stated that no further XL or CRADA bioreactor projects, including the Virginia Project XL Landfills project, should be approved. The commentor proposed a set of recommendations for changing the design and operation requirements in 40 CFR part 258 with respect to (a) pre shredding, (b) compaction, (c) liner, (d) side slopes, (e) leachate collection, (f) gas collection, (g) buffer zones, and (h) final flush.

Response: These comments are beyond the scope of today's rulemaking. As previously stated, EPA did not propose and is not promulgating today a rule of general applicability regarding bioreactor design specifications. Moreover, the comments regarding the XL Project that is the subject of today's rule concern the terms of the Final Project Agreement (FPA). The commentor did not submit any comments on the draft FPA in response to EPA Federal Register notice and request for comments. However, although the commentor made no mention of any aspect of the proposed site specific rule in the comments, the commentor referenced the VA Project XL Landfills in its broad discussions of how the part 258 criteria should be changed prospectively for design of landfills that will be operated as bioreactors. To the extent these comments can be Virginia Bioreactor Project XL Landfills  Response to Comments  Page 12 applied to today's rule, EPA responds in the context of responding to those recommendations.

Regarding a generic protocol and docket for bioreactor projects, EPA notes that the Office of Solid Waste and the Office of Research and Development are developing a centralized Internet page for bioreactor landfills. EPA plans to make annual reports for each project available to the public.

(a) Pre shredding of waste Comment: Pre shredding is needed to maximize distribution of liquid and promote decomposition, due to the heterogeneous nature of solid waste, the omnipresence of plastic bags, extremely high densities, and the difficulty of evenly distributing water in trench works throughout the waste load.

Response: As previously stated, these comments are beyond the scope of this rulemaking. However, if the commentor intended that today's rule should require that waste placed in the VA Project XL Landfills cells to be operated as bioreactors be pre shredded, such a requirement would not be possible. The test cells that are the subject of today's rule are generally inactive, meaning that they do not and will not receive waste on an ongoing basis during this XL Project. Additional fill may be added to maintain positive drainage on the surface of the landfill during the project, however this will be a small fraction of the waste volume in the cells and a shredding requirement for additional fill would not provide useful information for evaluating the effect of shredding. None of the existing waste in the landfill test cells was shredded. Moreover, since the existing waste was not shredded, this will provide for a rigorous test of bioreactor operations.

(b) Compaction Comment: FPA did not include a discussion of the point at which increased densities prevent liquid additions from reaching a part of the load where compaction is greatest. Detailed information on what those density limits are and what operational practices are necessary to keep compression below those limits in all parts of the affected load are necessary before operational practices can be established.

Response: To the extent that this comment requests that this project establish operational practices for all bioreactors, this comment is beyond the scope of today's rulemaking. Since little, if any, additional waste will be added to the cells during the XL Project, EPA does not believe that density limits or operational practices are needed for this project. Compression, settlement and waste characteristics will be monitored during the XL Project. Among the goals for the XL Project as stated in the FPA are the uniform distribution of leachate throughout the waste mass in the test areas. The Project will evaluate the relative effectiveness of different horizontal trench designs for uniformly distributing leachate throughout the waste mass, identify several leachate delivery options to simplify operations and provide monitoring features within the horizontal trenches so that liquid head and distribution rate within the trenches can be measured and Virginia Bioreactor Project XL Landfills  Response to Comments  Page 13 documented. The application capacity of the trenches has been estimated using the methodology described by Maier [1998]. This evaluation considered the moisture content of the waste, the hydraulic properties of the waste, the moisture retention capacity of the waste, and the head of liquid on the trench.

(c) Liners Comment: All bioreactors must be built with two complete Subtitle C composite liner/ leachate collection systems and with additional underliner specifications. The commentor notes that the proposal specified a design for Maplewood and King George that achieves much more than other MSWLF, although not to the specification recommended by the commentor.

Response: To the extent the comment recommends a generally applicable liner requirement for bioreactor design, it is beyond the scope of today's rule. EPA agrees that the proposed liner specification, which is in place at the Maplewood and King George landfills should be protective of human health and environment under circumstances of liquids addition. During landfill permitting, VADEQ determined that the design of the liner was equivalent to the composite design specified in 40 CFR Part 258.

(d) Side slopes Comment: Bioreactors should be required to have side slopes no steeper than 4: 1 because the introduction of liquids significantly increases the risk of seepages leading to side slope failures.

Response: To the extent the comment recommends a generally applicable requirement for bioreactor design, it is beyond the scope of today's rule. In both cases GeoSyntec conducted a site specific slope stability analysis to determine the effect of bioreactor operations on the VA Project XL Landfills. The slope stability analysis for the existing conditions at the landfills calculated a factor of safety of 1.62 for the Maplewood Landfill and 1. 53 for the King George Landfill. These results both exceed the minimum value of 1.5 recommended by EPA in "Solid Waste Disposal Facility Criteria Document No. EPA 530 R 93 017, November 1993. GeoSyntec also evaluated whether bioreactor operations in the test cells would affect the factor of safety. In both landfills GeoSyntec concluded the factor of safety would remain unchanged by bioreactor operations in the test cells. In the results of analyses for the Maplewood Landfill GeoSyntec concluded the critical failure surface is located outside the anticipate zone that would be wetted by liquid application during recirculation events. The side slopes adjacent to the bioreactor test area at the Maplewood Landfill are 4: 1 on threes sides while the fourth side is located adjacent to another cell. The King George Landfill test area is bounded on three sides by adjacent cells. The fourth side is approximately 450 feet long and is adjacent to a 3: 1 slope. Finally, there will be a minimum 50 foot setback from the crest to the outward slope for leachate injection as a safety measure against side slope leachate outbreaks. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 14 (e) Leachate collection Comment: Problems with increased biofouling, clogging and siltation can be expected to be severe. Increased temperature as the organic material at the bottom of the waste load "cooks" may degrade the performance of the polymer membrane if leachate pools instead of being drained away by high performance leachate lines. Reliance on the HELP model is insufficient for future decision making. There should be enhanced redundancy to cope with unanticipated problems including, a maximum distance between lines, a maximum length of the lines that are more difficult to clean out when clogged, greater grades and more rigorous resilience of the gravel bed to resist clogging. A 100 foot separation between lines, 1, 000 foot line length, 5  grade and gravel not sand and not calcium based gravel for the drainage bed is suggested.

Response: EPA believes that there is sufficient information available to reliably predict the performance of the leachate collection systems that are subject to today's rule. There is a dedicated leachate line for each of the test cells. The leachate lines are already in place and adequate for the test at the site. Leachate lines are approximately 1650 feet and are approximately 1500 feet at King George and Maplewood, respectively. The design of the leachate collection system piping provides for the pipe to be embedded in a high permeability stone layer. Geocloth over the stone and the stone itself distributes the weight and load. Further the high permeability stone acts as a redundant pathway for removal of leachate from the landfill if the piping were to become clogged. There is also a second riser extending from the primary leachate collection layer up to the sump house building at both the King George and Maplewood Landfills. Finally, WM has stated that the leachate lines could be cleaned out with a jetting device if they were to become clogged.

The cells in question will be operated as anaerobic bioreactors. Elevated temperatures are generally not a problem with anaerobic reactions. Only aerobic processes are of concern since they generate much more heat. Air is not being injected to any of these landfills and therefore there should be no significant aerobic reactions to cause major temperature increases. In addition to the HELP model, monitoring information available from existing landfills operated as bioreactors show that there is some elevation of temperature in the waste but only minimally near the liner. (See "The Potential Effects of Elevated Bioreactor Temperatures on the Interface Shear Strength of Textured Geomembranes and the Hydraulic Transmissivity of Geocomposite Drainage Materials, Waste Tech 2002, Melody A. Adams, Lance Reed, Nathan Ivy, February 2002). In addition, available information indicates the waste appears to be hottest in its core, not near the perimeter. There is also a buffer of sand and/ or gravel above the liners for additional protection against elevated temperatures. WM has installed temperature monitoring wells at three depths at Maplewood and fourth depths at King George in several locations throughout the test cells and the landfills. WM will be monitoring and documenting temperature at these locations. Finally, the FPA provides for collection of data on the temperature of landfill gas.

(f) Gas collection Virginia Bioreactor Project XL Landfills  Response to Comments  Page 15 Comment: The commentor could find no specification in the Application or Final Project Agreement of how the gas collection system would be constructed to address gas emissions from the bioreactor cells. Repeated reference is made that the design will comply with 40 CFR part 60, subpart WWW. Subpart WWW does not address system components needed to capture fugitive gases from a bioreactor landfill. This is totally unacceptable. Before this case proceeds any further, the applicant must be required to submit as part of its proposal detailed plans for how it intends to cope with the unique gas generation patterns of a bioreactor in which the site is highly unstable, making pipe and trench placement extremely difficult and the rate of gas generation is accelerated to a point in time when the geometry of a landfill creates additional hurdles to capturing gas.

Response: Today's rule does not address gas collection because it is a site specific rule under RCRA. Thus this comment is beyond the scope of today's rule making. The gas collection and control requirements applicable to MSWLFs (including both dry tomb and bioreactor land fills) are regulated under the Clean Air Act (CAA).

With respect to this project, the project sponsor did not request any regulatory flexibility for any increased fugitive emissions of landfill gas that might result from the project. The landfills both have undergone New Source Performance Standards (NSPS) permitting and CAA Title V permitting. WM as the operator must comply with all applicable air regulations. EPA and Virginia Department of Environmental Quality permitting staff have reviewed this project and do not believe it represents any increased adverse impact on human health or the environment.

As stated in the FPA, the surface test for methane concentration, which is used to determine collection efficiency and surface integrity, will be conducted according to the MSW Landfill NSPS surface monitoring requirements set forth in 40 CFR section 60.755( c).

As stated in the FPA, one of the project goals is to minimize landfill gas emissions by maximizing collection and control through early installation and operation of a comprehensive collection and control system in the bioreactor cell. If odor problems or air quality problems occur, then the system will be expanded as needed (e. g., using additional extraction wells or trenches or by placing less permeable cover over affected areas).

As stated in the FPA, one of the goals of the monitoring program is to monitor the ground surface of the entire site, including the liquid application area, for the presence of landfill gasses (i. e. methane, NMOCs, etc.,) to ensure that permit and regulatory limits are not exceeded, and evaluate the need for additional landfill gas collection components (i. e., wells and header pipe) during liquid application events to improve the effectiveness of the landfill gas collection system. (see section 3. 1. 2. 4 Potential Environmental Impact to Air)

As stated in the rule, effective November 1999, Waste Management installed, and is operating, an active (i. e. vacuum induced) landfill gas collection system in Phases 1, 2 and 3 at the Maplewood Landfill. An active gas collection system became operational at the King George Landfill on Virginia Bioreactor Project XL Landfills  Response to Comments  Page 16 December 10, 2000. In addition, on September 1, 2001 Waste Management signed an agreement with a private energy development company to construct a 9MW power plant fueled by landfill gas at the Maplewood Landfill. This plant is currently beneficially reusing the landfill gas to generate energy. Waste Management is currently negotiating a similar gas/ energy recovery agreement for the King George Landfill.

(g) Buffer Zones Comment: Buffer zone are needed to keep liquids away from side walls in order to avoid seepage that can lead to a side wall failure. The commentor did not see a discussion of buffer zones or how liquid addition would be managed to prevent leakage into the buffer.

Response: Buffer zones for the side slopes are discussed in the FPA. The FPA states that in order to minimize the potential for the occurrence of seeps, liquid distribution structures will be placed at least 50 feet away from the crests of outward slopes. The FPA also states that the potential impacts that could be caused by seeps are and will continue to be promptly mitigated at the Maplewood and King George County Landfills through a program of seep detection through visual inspections and of maintenance to quickly repair any seep that would occur. The leachate distribution pipes will be installed along contour lines or perpendicular to the slope. WM agreed to monitor the liquid levels in the landfill gas extraction wells during the project as an additional safe guard against liquid buildup in the landfill and the possibility of surface seeps. WM also will be monitoring gas production. If liquid levels were to rise into the gas extraction wells this could lower the production of landfill gas. This program of inspections and maintenance will continue to be implemented throughout the XL Project. Further, because of the ongoing project, site personnel will be particularly advised to be more sensitive to the potential for seeps. At King George only the south side of the test area is directly adjacent to a side slope, the other three sides are adjacent to other cells of the landfill.

(h) Final flush Comment: Before final cap is placed on the cell, clean water should be flushed through the site to leach out hazardous compounds.

Response: As stated in proposed rule, at the end of the project term the VA Project XL Landfills must return to compliance with the regulatory requirements which would have been in effect absent the flexibility provided through the site specific rule. As explained in the preamble of the proposed rule, research reported in, "Active Municipal Waste Landfill Operations: A Biochemical Reactor," Reinhart, 1995 (Reinhart 1995), has shown that bioreactor processes tend to reduce the concentration of many pollutants in leachate, including organic acids and other soluble organic pollutants. Bioreactor operations brings pH to near neutral conditions and generally, metals are much less mobile under these condition. The Reinhart 1995 study found that metals were largely precipitated and immobilized in the waste of bioreactor landfills. Upon completion of the Project term, the liquid addition to the bioreactor test cells will be stopped and Virginia Bioreactor Project XL Landfills  Response to Comments  Page 17 the leachate will be drained and the head on the liner will continue to be maintained as specified by standard RCRA Subtitle D landfill regulations.

III Proposed Changes in Bioreactor Tests 14. Comment Summary: Stabilization (pages 24 27)

To determine whether a waste load has been stabilized such that the post closure period might be reduced requires a reliable measurement of how much organic material remains undecomposed at closure. This requires statistical sampling techniques, and then reliable measures of remaining carbon values and of the rate of decomposition. The commentor stated its view of what constitutes reliable statistical sampling for the purpose of measuring waste stabilization.

Response: The comment is beyond the scope of today's rulemaking. There is nothing in the proposed rule or today's final rule that would shorten or reduce the post closure period. Moreover, the comment concerns the FPA, which the commentor did not comment on when the Agency announced the availability of the draft FPA and solicited public comments. The FPA provides for annual testing of solid waste stabilization and decomposition by the collection of 4 test borings per year with 3 samples per boring. The samples will be collected from approximately 5  10 ft., 25  30 ft:, 45  50 ft. and analyzed for moisture content, biochemical methane potential, cellulose, lignin, hemi cellulose, volatile solids and pH.

15. Comment Summary: Gas Collection (pages 28 29)

The FPA relies on measurements of fugitive gas emissions pursuant to 40 CFR part 60, subpart WWW, but that rule only requires limited measurement of the concentration of select compounds in grab samples. Measurements of the total quantity of methane emissions are needed, not just concentration levels. Measurements are also essential to determine the collection efficiency of the gas extraction systems for estimating landfills' contributions to global warming.

The study by SCS Engineers contains no empirical data to support a claim of enhanced gas collection performance of bioreactors, but rather is purely hypothetical in which the authors assume that bioreactor gas collection is more efficient.

The commentor recommended that same statistical sampling techniques it recommended for stabilization tests (see p. 25) should be used to determine how many samples are necessary and which part of the landfill face to sample, but specified the following differences:

(1) The additional separation of the waste load by vertical strata is unnecessary, (2) The importance of including the exposed side walls as well as the working face in the array from which samples are pulled is absolutely essential; and (3) Samples should be pulled during each season of the year on a day selected randomly. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 18 The commentor also recommended that if a cylindrical polypropylene enclosure is placed on the ground surface and a small amount of surrounding dirt is used to provide a seal, with a batteryoperated fan within the enclosure, samples can be collected from within the head space.

Response: The comment is beyond the scope of today's rulemaking. As the commentor notes, requirements concerning landfill gas collection and control are contained in Clean Air regulations. These regulatory requirements are implemented through VADEQ permits. However, as part of the XL Project studies agreed to in the Final Project Agreement, Waste Management will measure the flow rate of landfill gas to determine the quantity of gas generated, measure emissions of releases of landfill gas, in order to verify that permit specified air quality standards are not being exceeded, and track the frequency of any odor complaints during and after liquid application events.

For the first year, tests will be done quarterly and for the following years some test frequencies will be changed to semi annually or as otherwise required in the FESOP with the VADEQ for early gas collection, control, and monitoring.

Details on this measuring and the LF gas extraction system are contained in the monitoring plan in the NSPS permits for the landfills. There is active gas collection at both Project XL Landfills. WM is currently beneficially reusing the LF gas at the Maplewood LF. WM is working toward the beneficial reuse of the methane at the King George LF.

The FPA outlines the goals for the monitoring system which include the monitoring of the ground surface of the entire site, including the liquid application area, for the presence of landfill gasses (i. e. methane, NMOCs, etc.,) to ensure that permit and regulatory limits are not exceeded, and evaluate the need for additional landfill gas collection components (i. e., wells and header pipe) during liquid application events to improve the effectiveness of the landfill gas collection system. The surface test for methane concentration which is used to determine collection efficiency and surface integrity will be conducted according to NSPS surface monitoring requirements in 40 CFR section 60.755 (c).

The surface test for methane concentration which is used to determine collection efficiency and surface integrity will be conducted according to NSPS surface monitoring requirements in 40 CFR section 60.755 (c).

16. Comment Summary: Leachate Collection Line (page 30)

The commentor stated that the ability to maintain leachate collection lines in dry tomb landfills has not been scientifically qualified and is a serious cause of concern, which is greater in bioreactor landfills due to increased problems of siltation, clogging and biofouling. A key test to evaluate whether the performance of these lines may be compromised is to use an in line camera along with the clean out head annually in the test and control cells. Virginia Bioreactor Project XL Landfills  Response to Comments  Page 19 Response: Today's rule requires that the leachate collection system shall be operated, monitored and maintained to ensure that less than 30 cm depth of leachate is maintained over the liner. The rule also requires the operator to collect monthly sampling of the leachate; determine on a semiannual basis the total quantity of leachate collected in test and control areas; the total quantity of liquids applied in the test areas and determination of any changes in this quantity over time; the total quantity of leachate in on site storage structures and any leachate taken for offsite disposal. The collection of this information will provide sufficient information to be able to evaluate how well the leachate collection system is performing. Although a leachate line visual inspection using an in line camera is one way of assessing the performance of the leachate collection lines, EPA does not agree that this test should be required as part of today's rule. GeoSyntec performed a leachate pipe strength calculation as part of the evaluation of the landfill leachate system. See response to Comment 13 (e) above.

Conclusion 17. Comment Summary: The FPA does not resolve key issues regarding development of bioreactor designs, foremost of which is the assumption that performance equal to dry tomb landfills constitutes superior performance and that economics takes priority over the environmental. Greater scientific rigor is needed in several tests in order to produce reliable data. The commentor does not believe that the rulemaking should go forward until the signification deficiencies identified are corrected. Economic considerations and pressures should not deter EPA from making the necessary corrections.

Response: EPA appreciates that the commentor has serious reservations regarding bioreactor landfill technology in general and is concerned in particular about design criteria for bioreactor landfills. However, today's rulemaking does not concern design criteria for bioreactors, rather it concerns site specific requirements for operation of existing landfill cells as bioreactors for a finite period of time. EPA does not agree that today's rule or the XL project that it addresses prioritized economics over the environment. As set forth in the FPA and guidelines for Project XL, superior environmental performance means environmental performance that is superior to what would be achieved through compliance with current and reasonably anticipated future regulations. The agency does not agree with the statement that, "performance equal to dry tomb landfills constitutes superior performance" but rather believes bioreactors have the potential to provide superior performance as stated in the Rule and FPA.