September 27,2011

Via Electronic Transmittal: cozzie.david@epamail.epa.gov ward.hillary@epamail.epa.gov Ms. Hillary Ward Sector Policies and Programs Division (E143-01) Office ofAir Quality, Planning and Standards U.S. Environmental Protection Agency 109T.W. Alexander Drive Research Triangle Park, NC 27709

Dear Hillary:

We appreciateyourtaking time on bgust 30, 20'1Uo discuss optionswith industry stakeholders for addressingwellhead operatingstandards pursuantto EPA's revisions of40 CFR 60 SubpartWWW (Landfill NSPS). As promised, we prepared recommendationsfor rule revisions and clarifications pursuantto current wellhead operating standards.

When EPA established thewellhead standards for pressure, temperature and oxygen/nitrogen, many landfills did not have extensive experience with installing, operating and maintaining LFG collection and control systems (GCCS), or in operating beneficial landfill gas to energy projects. The industry also**~i~** not have any experience withr'lJmericwellhead**stand~!~~L,!nd~id** not fully comprehend the implications. Atthe time, EPA was concerned about developing standards thatwould help ensure thatGCCS were operated to preventformation of landfill fires, prevent inhibition ofanaerobic decomposition, and effectively controlsurface emissions. It has been 15 years since the Landfill NSPS was promulgated, and in thattime the landfill sector has gained a great deal ofexperience with GCCS and landfill gas to energy systems. In fact, the majority of landfills subject to the NSPS have installed GCCS systems, either because they have triggered the requirement to do so or have voluntarily installed gas collection systems early.

Efforts to complywith the prescriptive Landfill NSPS wellhead standards in 60.753(c), particularly the oxygen/nitrogen and temperature limits can often be counterproductiveto controlling surface emissions ofmethane. In orderto control temperature and oxygen/nitrogen levels, landfill owner/operators must reduce the vacuum applied tothewells. This in turn reduces the gas collection efficiency ofthe system - asystem designed to prevent surface emissions. For example, climate and waste characteristics often result in landfill gas temperatures routinely measured in excess of55 degrees Centigrade (131 degrees Fahrenheit).



### 1Additionally, arid landfills, non-producing landfill areas and interim early gas collection devices may routinelyexhibitelevated oxygen levels. Although the NSPS allows landfill owner/operatorsto establish a higher operatingvalue (HOV) with a demonstration that elevated parameter{s) do not cause fires orsignificantly inhibit anaerobic decomposition, many state agencies require an affirmative agency approval. Obtaining such approvals can take months oreven years. In extreme cases, agencies denyor never respond to HOV requests leavingthefacility in compliance limbo. Generallythis occurs because theydo notfully understand how GCCS operate.
Industry Recommendation for Revisions to the NSPS based on Operational Experience
Following are two recommendations for revisions to the NSPS that address wellhead operating standards and basis for our recommendations.

1. Eliminatethe pressure, temperature and oxygen/nitrogen standards inthe NSPS:
The prescriptive wellhead standards were included in the NSPS toguide landfill owners/operators in operatingthe new gas collection and control systems, specificallyto prevent subsurface oxidation events. Since the rule promulgation in 1996, the industry has gained significant and widespread field operations experience. The existing wellhead standards
are notthe best indicator ofGCCS performance because they are arbitrary limits on a limited number of parameters which do not accurately represent proper GCCS performance. This limited data does not provide a complete analysis ofwhat is happening within the landfill in all situations. As a result, most landfill owner/operators monitor additional parameters (e.g., methane, carbon dioxide, balance gas, flow, and header pressure) to properly understand what is happening within the landfill and to optimize GCCS operations. There are so manyvariables it would be extremely difficultto develop regulatorystandards that address all common operating scenarios. Further, the existing wellhead operating standards do not provide any additional protection to the environment because the landfill owner/operator is already heavily incentivized to maximize GCCS collection efficiencyto control odor, control subsurface migration, minimize groundwater impacts, maintain cap stability and integrity, control surface emissions, and maximize energy recovery. In addition, landfill owners and operators diligently operateto avoid causing subsurface fires as potential damage to leachate containment liners, gas collection and control systems and otherenvironmental controls can result in non-compliance and be extremely costly to mitigate.
The temperature limit in NSPS was established as an alert level that may indicate a problem that prompts further investigation; well temperature at orabove 55 degrees Celsius 

### (0C) does not mean there is afire or indicate improper operation. Awell temperature at or above 55°C may be normal operating conditions for afacility based on site-specific climate and waste characterization. In the rulemaking record, EPA states thatvacuum adjustment is the solution to reduce temperature, nofsystem expansion (see section 1.2.2.6 and response to comments Page 2-110). Nonetheless, some state agencies have required automaticsystem expansions as



### 2an attempted resolution for higher temperature readings atwellheads because ofcurrent wording in the NSPS.
With over 15 years ofGees operational experience, the prescriptive wellhead standards require extensive industry and agency resources to demonstrate and/or approve HOVs at sites where other data indicates no issues with respectto surface emissions, subsurface fires or improper Gees operation. In the most extreme cases, agencies have required system expansion and/or enforcementactionswere taken where site conditions did notwarrant such actions (no fires, normal operationsfor site conditions).
A landfill owneroroperator must have flexibilityto demonstrate proper performance ofthe gas collection system during the early stage ofgas collection (i.e., front end ofthe gas generation curve). It is often difficultto meet NSPS operational standards using interim control, such as a leachate collection system, since 1) they are not designed to be airtight; 2) they are not "in" refuse, butare instead below or adjacenttothe refuse; and 3) piping thatconveys leachate (and the landfill gas) may preventthe flow of landfill gas underall circumstances (e.g., when leachate sump levels are high). Large quantities ofairoften enter leachate collection systems because they are not designed to be airtight. However, this is notan issue because the air does not move through the waste and thereforewill not cause subsurface oxidation withinthe refuse. Although the NSPS rules allow for alternative operational standards (Le., HOVfor oxygen), regulatory agencies have been extremely reluctant to grant such alternatives due to unfamiliaritywith LFG collection and control technology and existing site conditions. IfEPA, as part of its revisions to the NSPS, plans to expedite timing ofgas system installation, landfillswill need more flexibilityto address lower LFG qualityand quantity and the abilityto adapt system design and operations accordingly. Removal ofthe wellhead standards provides such operational flexibility.

Just as a landfill owneror operator must have flexibility to demonstrate proper performance of the gas collection system duringthe early stage ofgas collection similarflexibility is also needed to address declining flow situations (Le., back end ofthe gas generation curve). As we discussed in ourJuly 29,2011 call and August 8, 2011 letter, there is minimal risk ofoxygen intrusion due to the installation offinal cover. Further, because the gas generation/extraction rate is significantly reduced, the actual volume ofoxygen entering the landfill is minimal, even if the oxygen concentration ofthe gas itself is high. Therefore the risk forfire dueto ambient air intrusion is extremely low. As discussed in the August 8, 2011 letter, sites require flexibility to operationally shut-offwells located in areas with decliningflow and poorgas quality. Eliminatingthe requirement to conform to temperature and oxygen/nitrogen wellheads standards reduces regulatory burdensfor both agencies and industryto process HOVs and alternativetimelines for such exceedances.



### 32. Eliminate thetemperature and oxygen/nitrogen standards, and maintainthe requirementto operate the system with negative pressure ateach wellhead except underconditions at 60.7S3(b): Ofthe current wellhead operating standards, only pressure is directlytied tocontrolling emissions. As stated above, we do not believe thatthe wellhead pressure standard provides additional environmental protection in light ofother operating incentives described above. However, this negative pressure parameter could be maintained to ensure a minimum standard ofgas collection is maintained. Temperature and oxygen/nitrogen limitsshould be eliminated forthe reasons stated above; primarilytheir regulation is counter-productive to maximizing LFG collection efficiencyand controlling surface emissions.

Although ourpriority recommendation is to remove the prescriptivewellhead standards from the NSPS requirements, we recognize that opinions within EPA may differfrom this plausible and demonstrated solution. Therefore we developed thefollowing alternative approach: Maintain the pressure limitand replace thetemperature and oxygen/nitrogen limitswith a methane (CH4) to carbon dioxide (C02) ratio. We believethis approach offers amore reliable and earlier indication ofwellhead performance than current standards, as described below:
The purpose ofthetemperature and oxygen/nitrogen wellhead limits is to ensure the system is notoperated in awaythat causes fires orsignificantly inhibits anaerobic decomposition by killing methanogens. The CH4/C02 ratio is a better indicatorofthese issues than the current wellhead standards because it is a direct indicatorofthe predominant biological process within the landfill. Further, most landfill owner/operators already monitor both methane and carbon dioxide as partof normal GCCS operations using the same field monitoring devices.

Anaerobic methanogenic bacteria produce CH4 concentrations ofapproximately 55-60% by volume and C02 concentrations ofapproximately 40-45% by volume. Aerobic bacteria produce C02 and water

- no CH4. Ifover-extraction occurs at a collection device, an excessive quantity ofair enters the landfill. The oxygen from the air kills the anaerobic methanogenic bacteria and allows aerobic bacteria to survive, thereby reducing the concentration ofCH4 and increaSing the concentration ofC02. Therefore, CH4/C02 ratios above 1.0 (i.e., the CH4 concentration is greaterthan the C02 ratio) are considered normal and indicatethat neithertemperature nor over extraction is significantly inhibiting anaerobic decomposition or killing the methanogens that produce the CH4. A CH4/C02 ratio below 1.0generally indicates a significant amount of aerobic decomposition is beginning to occur. Because significant aerobic decomposition usually preceeds a subsurface fire, the CH4/C02 ratio provides agood "earlywarning" indicator and allows the landfill owner/operatorto respond before afire begins.

An exception is arid and olderwaste sites, which typically produce LFG ata much lower generation rate. Because ofthe lower LFG generation rate, it is easy for a relatively small volume ofairto kill the methanogenic bacteria and cause the CH4/C02 ratio tofall below 1.0. However, in these situationsthetotal volume ofairentering the landfill is notenough to cause a landfill fire orsignificantly inhibit anaerobic decomposition. Therefore, forarid sites {i.e.,



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### those with average annual precipitation less than 25" /year) orareas thatcontain waste in which all the waste in place is more than 20 years old, a CH4/C02 limit of0.75 is more appropriate.

We believe CH4/C02 ratio is a more representative parameterfor measuring system performance and will result in farfewervariances. However, because landfill processes are dynamic, situations may arise where the CH4/C02 ratios would not be appropriate. Therefore, the rule must maintain the current process fordemonstrating an alternative ratio, where necessary, for proper operation.

Recommended NSPS Rule Clarifications

If EPA retains/replaces one or more wellhead standards, we recommend EPA clarify the following critical issues in the Preamble and/or Final Rule changes for HOV demonstrations:

• No approval required for HOVs; rule clearly states that the owner or operator "may establish" such values, but somehow this has evolved to case-by-case regulatory approval.
• Site makes demonstration instead; dOGl:IfAentation kept 

### on site andavailable-for review by air agencies. Documentation could be included in semiannual reports, ifwarranted.
• Demonstration designed to meet rule requirement that an alternate HOV does not cause/contribute to afire, nor significantly inhibit anaerobic decomposition.
• Because ofthe many possible scenarios, agencies should not prescribe the types ofdata that should be collected by landfills to establish appropriate values but allow sitespecific conditions to dictate.

If EPA retains/replaces one or more wellhead standard, then we recommend EPA clarify that correction action timelines that extend beyond 15 days but are less than 120 days do not require agency approval. Furthermore, clarification should be provided that remedies other than expansion ofthe gas well field can also be implemented in the 120-day period without agency approval. In the Preamble tothe June 16, 1998 landfill NSPS amendments EPA stated

If

### Depending on the remedy selected to correct the problem, a differenttimeline may be needed, but any timeline extending more than 120 days must be approved by the regulatory agency. If 

### [F.R. Vol. 63, No. 115, P. 32748, June 16, 1998]. Industry recommends EPAfinalize this previously proposed clarification in the rule such that:

• Corrective action timelines exceeding 15 days but less than 120 days do not require agency approval; agency approval is only required when additional time beyond 120 days is necessary to correct a problem.
• Remedies other than lFG system expansion can also be implemented in the 120-day window without agency approval. Approval is only necessary if the remedy will take
more than 120 days.



### 5We also recommend that EPA clarifythat sites may exclude wells located in dangerous areas (i.e., active filling areas, raised wells) from monitoring. This is consistent with surface emissions monitoring provisions (see 40CFR 60.7S3(d)).

Please contact us ifyou have any questions regarding ourcomments. Waste Management greatlyvalues the successful collaboration we have shared with theAgency in developing protective and workable standards for MSW landfills. We lookforward to our continued working relationship with you.
Sincerely,

Kerry Kelly, Director, Federal Public Affairs

CC: F. Caponi, LACSD S. Crawford, SWANA A. Marconi, DSWA R. Repa, NSWMA R. Strube, Veolia P. Sullivan, SCS N. Wuestenberg, Republic Services Amy Van Kolken Banister, Senior Director, Corporate Air Programs



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