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IDEM > Nonrule Policies > Waste-0056-NPD Waste-0056-NPD

Indiana Department of Environmental Management
Office of Land Quality
100 North Senate Avenue
Indianapolis, IN 46204-2241
OLQ Phone: (317) 232-8941

Title: Methane Monitoring Program
Identification Number: WASTE-0056-NPD
Date Originally Effective: March 17, 2005
Dates Revised: March 28, 2007
Other Policies Repealed or Amended: Enclosure D1 Guidance
Citations Affected: 329 IAC 10-20-17

Brief Description of Subject Matter:
In accordance with the Solid Waste Rule 329 IAC 10-20-17, the owner, operator, or permittee of a municipal solid waste landfill (MSWLF) is required to monitor and control the landfill gas generated by their site to prevent methane concentrations from exceeding 25% of the lower explosive limit for methane in MSWLF structures, and the lower explosive limit for methane at the facility boundary. This document provides guidance for content, design considerations, and specifications that should be included in a Methane Monitoring Program.

This nonrule policy document is intended solely as guidance and does not have the effect of law or represent formal Indiana Department of Environmental Management (IDEM) decisions or final actions. This nonrule policy document shall be used in conjunction with applicable laws. It does not replace applicable laws, and if it conflicts with these laws, the laws shall control. This nonrule policy document may be put into effect by IDEM thirty days after presentation to the appropriate board. Pursuant to IC 13-14-11.5, this policy will be available for public inspection for at least 45 days prior to presentation to the appropriate board. If the nonrule policy is presented to more than one board, it will be effective thirty days after presentation to the last. IDEM will submit the policy to the Indiana Register for publication. Revisions to the policy will follow the same procedure of presentation to the board and publication.

Methane Monitoring Program

In accordance with the Solid Waste Rule 329 IAC 10-20-17, the owner, operator, or permittee of a municipal solid waste landfill (MSWLF) is required to monitor and control the landfill gas generated by their site to prevent methane concentrations from exceeding 25% of the lower explosive limit for methane in MSWLF structures, and the lower explosive limit for methane at the facility boundary. This document provides guidance for content, design considerations, and specifications that will satisfy the commissioner that a Methane Monitoring Program proposal complies with 329 IAC 10-20-17.

This nonrule policy document will be utilized during the commissioner's review of Methane Monitoring Program proposals submitted as required by the Solid Waste Rule for new sites and site expansions. The commissioner shall approve alternatives to the final design as outlined in this guidance if they are demonstrated, to the satisfaction of the commissioner, to provide at least the equivalent protection to human health and the environment. Currently approved Methane Monitoring Programs may continue as approved unless it is determined that the program is ineffective due to physical evidence of gas migration or geological conditions that warrant revision based on 329 IAC 10-20-17(c). Revisions to current Methane Monitoring Programs will follow this guidance only as it is directly supported by the Rule.

Much of the geological information requested in this guidance is available in the site hydrostudy submitted in the permit application under 329 IAC 10-15-4, in subsequent boring information and in the results of the regular ground water sampling.

Policy Standards for Landfill Methane Monitoring Programs

329 IAC 10-20-17(b) requires MSWLFs to prepare, propose for the commissioner's approval, and implement an approved routine Methane Monitoring Program. The proposal for a facility Methane Monitoring Program should include the following:

  1. Facility Conditions
  2. MSWLF Structures
  3. Facility Boundary
  4. Monitoring
  5. Contingency
  6. Remedy Proposal
  7. Probe Maintenance
  8. Modifications
  9. Reporting

1. Facility Conditions

329 IAC 10-20-17(c) requires that the type and frequency of methane monitoring be based on the facility's structural and geological conditions. Conditions applicable to the design of the methane monitoring system should be included in the proposal as follows:

1.1 A narrative describing the following landfill conditions:

  1. Maximum depth of landfill and/or waste;
  2. Description of the bottom liner design components;
  3. Activities and/or practices that might increase or decrease production of landfill gas;
  4. The current condition of the facility as it relates to gas and gas-migration related stress including current gas venting spots and leachate seeps on-site and off-site; and
  5. A general description and location of any devices currently in-place that are designed to vent landfill gas from the soil or from the waste.

1.2 A narrative with plans and charts describing the following geological conditions:

  1. Time versus water level graphs of the uppermost aquifer using all available data collected from the ground water monitoring well system;
  2. Determination of stratigraphic target zones for the installation of gas probes;
  3. Plans depicting locations where such target zones might provide natural venting of gas (such as cut-banks and borrow-pits); and
  4. Geologic cross-sections depicting stratigraphic layers and their predicted role in aiding or preventing gas migration both vertically and laterally. The greatest depth of the liner and waste placement should be indicated on the cross-section.

2. MSWLF Structures

329 IAC 10-20-17(a)(1) requires the facility to measure methane gas in MSWLF structures, excluding gas control, leachate collection manholes, or recovery system components.

The Methane Monitoring Program proposal should include the following information:

2.1 A narrative describing the method of methane measurement including:

  1. Equipment used;
  2. Procedures of structure monitoring; and
  3. A plan including the identification of all applicable structures.

3. Facility Boundary

329 IAC 10-20-17(a)(2) requires the facility to ensure that sub-surface methane gas at the facility boundary does not exceed 100% of the lower explosive limit (LEL) of methane (5%). The facility may make this assurance under one of two systems: Early Warning or Perimeter. A detection in an early warning system allows the facility time to react prior to a violation, while a perimeter system detection automatically triggers a violation. The facility may opt for a mixture of both systems of testing locations within a Methane Monitoring Program. The Methane Monitoring Program should include the following considerations:

3.1 Testing locations under a perimeter system are designed to determine whether gas is migrating across the facility boundary and therefore need to be placed as close as practicable to the facility boundary but not more than fifty (50) feet inside the facility boundary. A detection over the LEL will be considered a transgression of methane across the facility boundary and therefore a violation of 329 IAC 10-20-17(a)(2).

3.2 Testing locations under an early warning system should be as close as possible to the solid waste boundary, however any well between the solid waste boundary and fifty (50) feet from the facility boundary should be considered early warning testing locations.

3.3 All facility boundary testing locations should be spaced on the schedule below. MSWLF structures that are subject to 329 IAC 10-20-17(a)(1) are not intended to be considered in these spacing guidelines.

  1. Every 100 feet when occupied buildings, or enclosed non-vented structures, are located at or within 600 feet of the solid waste boundary.
  2. Every 300 feet when occupied buildings, or enclosed non-vented structures, are located between 600 and 1,200 feet of the solid waste boundary.
  3. Every 1,000 feet when occupied buildings, or enclosed non-vented structures, are located greater than 1,200 feet of the solid waste boundary.
  4. The number of permanent probes may be increased or the distance between the probes reduced based on factors such as:
    1. Evidence of active gas migration;
    2. Absence of bottom liner; or
    3. Presence of frequent unconnected or poorly connected conduit zones.
  5. The number of permanent probes may be decreased or the distance between the probes expanded based on factors such as:
    1. Topographic barriers to methane migration such as ditches and borrow areas that completely expose the target zones identified in 1.2; or
    2. Reducing the circumference of the monitoring boundary by utilizing an early warning system as described in 3.2.

3.4 329 IAC 10-20-17(c) requires the facility to consider the geology of the site to determine gas migration. Generally, this will require a permanent probe at each test location capable of accessing soil gas at depths identified in 1.2.

3.5 329 IAC 10-21-4 should be used as a general guideline for gas probe installation. While this regulation pertains to ground water monitoring wells, the construction and reporting requirements are similar to gas probes. The major exception is 329 IAC 10-21-4(c)(5)(C), which limits screen length. In the case of gas probes, screen lengths should be specified and justified. IDEM prefers probe screen lengths to be as long as possible, though geological conditions may require specific adjustments.

3.6 The installation of permanent probes may be phased to coincide with cell construction provided the facility has interim measures in place and the approval of IDEM.

3.7 The testing location proposal should include landfill topographic plot plans clearly delineating the following on a scaled map as required by 329 IAC 10-11-2.5 and 329 IAC 10-15-2. Items requested below not applicable to the facility should be noted as such in the text or on the plan.

  1. Enclosed structures located on-site or within twelve hundred (1,200) feet of the facility's solid waste boundary (As required in 329 IAC 10-11-2.5(a)(9)(B));
  2. Solid waste, facility, and property boundaries (As required in 329 IAC 10-15-2(b));
  3. Location of proposed gas monitoring probes (As required in 329 IAC 10-15-2(d)(1)(G));
  4. Possible methane gas passageways identified such as utility lines, pipes, railroads, mines, field tiles, storm sewers, water lines, electric cables, and sand and/or gravel seams located within one hundred (100) feet of the solid waste boundary of the facility. Such items may be found on the map required in 329 IAC 10-11-2.5(a)(9).

3.8 The Methane Monitoring Program proposal should include a description of the system for measuring the methane gas concentration including:

  1. Gas probe installation procedures;
  2. Construction materials and methods;
  3. Design of probe and/or probe cluster;
  4. Gas probe schedule including the total length of the probe, length of the riser, and length and depth range of the screened interval, for all probes.

*Please be aware that, depending on the method chosen for installing permanent probes, the Department of Natural Resources may require borehole drillers to be certified per 312 IAC 13.

3.9 Testing methods, at each location, should be capable of monitoring methane:

  1. At elevations capable of detecting migrating gas at depths across the targeted zones identified in 1.2;
  2. In identified natural methane gas migration zones such as sand and/or gravel seams and open karst conduits located within one hundred (100) feet of the solid waste boundary of the facility;
  3. Near sensitive methane gas migration zones such as utility lines, and pipes located within one hundred (100) feet of the solid waste boundary of the facility; and
  4. At locations where a single screen might provide cross-contamination of perched ground water into an unsaturated zone below, the facility needs to propose a system of dealing with multiple unsaturated zones. Such a proposal should be developed in consultation with the IDEM Geology Section.

3.10 Additional probes might be needed after a Methane Monitoring Program is approved if evidence of gas migration is found through other means. (Ground water indications of gas migration can include volatile organic compounds and select inorganic compounds in ground water analysis results. Gas might also vent from ground water wells partially screened in unsaturated soils. Gas presence within the ground water well risers should be reported to IDEM based on 329 IAC 10-21-1(f). A facility could be put into an unnecessary ground water corrective action when a replacement well is more warranted.)

3.11 The installation of any device designed to vent landfill gas from the soil should be done in consultation with IDEM. Additional, or replacement, probes may be needed after a Methane Monitoring Program is approved if the function of a detection probe is impaired by nearby soil-gas venting.

4. Monitoring

329 IAC 10-20-17(c) requires a determination of type and frequency of methane monitoring. The Methane Monitoring Program should include collection method and quality control of landfill gas monitoring data as follows:

4.1 A description of the methods and equipment used to measure the concentration of methane at the landfill. The description should include procedures to ensure minimal air intrusion, calibration check, and employee and public safety. The equipment must be capable of measuring methane gas. It is preferred that oxygen and carbon dioxide percentages also be measured.

4.2 A sample of the form used to record data that includes the following field information:

  1. Analyst name;
  2. Gas instrument used;
  3. Calibration information;
  4. Date of monitoring event;
  5. Water level (if applicable);
  6. Name of probe and time monitored;
  7. Methane concentration (in either percent gas, or percent LEL); and
  8. Oxygen and carbon dioxide percentages (if available).

4.3 Methane monitoring should be done:

  1. Using permanent probes located around the perimeter of the facility;
  2. In all enclosed structures located at or within one hundred (100) feet of the solid waste boundary; and
  3. On a quarterly basis unless the site location and the initial methane gas concentration levels dictate a more frequent monitoring schedule.

4.4 Measurements taken within the top few feet of the ground surface have typically proven to be an ineffective measurement of landfill gas migration. Such methods might not take the hydrogeologic conditions into account as is required in 329 IAC 10-20-17(c).

5. Contingency

329 IAC 10-20-17(d) requires an MSWLF facility to follow a schedule of remedial measures if methane gas criteria are exceeded. The Methane Monitoring Program should include a contingency plan, as required in all current permits, that allows the facility to follow pre-developed steps for the initial response to a violation of gas criteria. This general remedial contingency plan should be designed to be performed without acquiring formal approval of a modification to the permit. Performance of any such remedial work should be done in consultation with the Geology Section. Completion of an approved contingency plan should satisfy the implementation portion of 329 IAC 10-20-17(d)(4). The Methane Monitoring Program should include an explanation of how the facility will comply with 329 IAC 10-20-17(d) with a contingency plan including the items in 5.1 and 5.2 below:

5.1 Notification information including:

  1. A list of property owners and residences immediately adjacent to the facility boundary;
  2. Criteria for notifying residents and owners of property that may be impacted by migrating gas;
  3. Location and contact information of the local fire department;
  4. Criteria for notifying the local fire department of a potential explosive gas threat;
  5. Name, phone number, and e-mail of IDEM contact personnel (either the site-assigned Geologist or the Geology Section Chief) and how they will be contacted in compliance with 329 IAC 10-20-17(d)(2).

5.2 A general narrative including:

  1. Immediate actions that might be taken to protect human health from uncontrolled landfill gas as required under 329 IAC 10-20-17(d)(1). This is meant to be a very general discussion, or list, that will be used as a starting point for consultation with the IDEM Geology Section in the event of an exceedence.
  2. Methods that will be used to determine the nature and extent of the problem as required under 329 IAC 10-20-17(d)(4). Any delineation of a gas migration plume should be established through supplemental sampling of soil gas from the same zone where the problem was first established.
  3. Criteria to be used to determine whether additional investigation is necessary;
  4. Criteria to be used to determine whether additional remedial action is necessary;
  5. Criteria to be used to determine when a remedial action is deemed finished.
  6. A schedule for the development of remedial investigation including:
    1. Nature and extent of a problem;
    2. The proposed remedy;
    3. Historical sampling results for use in comparison; and
    4. Methods to measure the effectiveness of the remedial action.

5.3 If the methane limits specified in 329 IAC 10-20-17(a) are exceeded:

  1. The contingency plan should be implemented immediately and with consultation with the Geology Section;
  2. Work done in compliance with the contingency plan must be compiled and placed in the operating record as per 329 IAC 10-20-17(d)(4) including the nature and extent determination and a proposed remedy within sixty (60) days of the detection;
  3. The Geology Section must be notified that the work has been done as per 329 IAC 10-20-17(d)(4) along with the determination whether additional investigation and remediation will be necessary;
  4. Completion of the work done in compliance with the approved contingency plan, including 5.1 and 5.2, should satisfy the implementation portion of 329 IAC 10-20-17(d)(4).
  5. To comply with the remedy proposal portion of 329 IAC 10-20-17(d)(4), please see Section 6 below.

5.4 Facilities with early warning systems, as described under 3.2, should include contingency plans specific to the system design. Such contingencies may include:

  1. The installation of sentinel probes, with the consultation of IDEM Geology Section, at the point nearest to the facility boundary from the well that has detected;
  2. A step-out system of probes toward the facility boundary to demonstrate that gas does not migrate to the facility boundary; or
  3. Installation of a remedial measure to cease additional gas migration.

6. Remedy Proposal

329 IAC 10-20-17(d)(4) requires a facility to propose a remedy within sixty (60) days of detecting levels of methane that exceed the limits defined in 329 IAC 10-20-17(a). The proposal that is inserted in the facility operating record should include both the work that has already been done, and any additional work that is deemed necessary. In the event that remediation tactics are ineffective and probe concentrations continue to exceed the regulatory limits of 329 IAC 10-20-17 for two quarters of monitoring, a gas venting system or a gas extraction system proposal for the facility should be submitted to IDEM for review. For more information on landfill gas venting systems, refer to the IDEM guidance document entitled "Methane Gas Venting System"

7. Probe Maintenance

329 IAC 10-20-17(b) requires the Methane Monitoring Program to be a long-term routine program. Monitoring devices should be properly protected and maintained to ensure continued compliance with the approved Methane Monitoring Program. Owing to time constraints between monitoring events, submittal of the plans and details of repairs and replacements of monitoring devices in the approved Methane Monitoring Program due to accidental damage may be done after the work is completed as allowed under 329 IAC 10-3-3(b).

7.1 If a probe is damaged, it should be fixed or replaced before the next monitoring event.

7.2 If a gas probe is damaged beyond repair, the probe should be properly abandoned and a replacement probe be installed within ten (10) feet of the original. A description of the work done should be submitted as part of the approved Methane Monitoring Program. A probe will automatically be considered ‘replaced' if it is installed within ten (10) feet of the original. If it is installed farther than ten (10) feet from the original, it will be considered a relocation, and a modification under 329 IAC 10-3-3(c), unless the new location is approved as a replacement by the Geology Section.

7.3 Abandonment procedures should follow 329 IAC 10-21-1(i). A description of the abandonment procedure should be submitted as part of the approved Methane Monitoring Program.

8. Modifications

Changes in an approved Methane Monitoring Program are, in effect, a modification to the permit. A change in the program may be prompted by such things as facility activities requiring probes to be relocated or any remedial work required under 329 IAC10-20-17 (d). Any change to the Methane Monitoring Program, excluding maintenance, repair or replacement, must be submitted to IDEM prior to implementation under 329 IAC 10-3-3.

9. Reporting

9.1 A Methane Monitoring Program is required (329 IAC 10-20-17(b)(1)) to be submitted, per the schedule devised in the facility permit, for approval prior to implementation and should include the information described in this document.

9.2 An As-Built Report will be required, as part of the pre-operational conditions of applicable solid waste permits. An as-Built Report for an approved revision to a Methane Monitoring Program needs to be submitted sixty (60) days after the implementation of the revision. This report should include such information that is gathered during the implementation of the Methane Monitoring Plan such as: probe construction, boring logs and a brief narrative, with geological cross-sections, on the probable interconnection between the screened interval of each probe and the zones targeted for screening in the Plan under 1.2.

9.3 Quarterly data are required (329 IAC 10-20-8(a)(10)) to be compiled and stored in the facility operating record. The Commissioner may request submittal or inspection of these data at any time (329 IAC 10-20-8(b)). Information in the quarterly data should include the items listed in 4.2.

9.4 Compilation of exceeding data and steps taken to protect human health are required by 329 IAC 10-20-17(d)(3) to be placed in the operating record within seven (7) days of a gas exceedence.

9.5 Within sixty (60) days of a detection of greater than 25% LEL (1.25% methane gas) in MSWLF structures or 100% LEL (5% methane gas) at the facility boundary, 329 IAC 10-20-17(d)(4) requires the following:

  1. Implementation of a remediation plan that must include the nature and extent of the problem and the proposed remedy. The remediation plan should include any work done in performance of the contingency plan and a proposal for any additional work that is deemed necessary to prevent additional violations.
  2. A copy of the remediation plan must be inserted into the facility operating record.
  3. Notification to the Commissioner that the remediation has been implemented. Notification should be in the form of a document outlining the work done, in consultation with IDEM Geology Section, and include a proposal for any additional work deemed necessary

9.6 Implementation of any remediation plan required under 329 IAC 10-20-17(d)(4) is considered a change to, or revision of, the Methane Monitoring Program and therefore a modification to the permit under 329 IAC 10-3-3. Items that require expediency to protect human health and the environment may be approved verbally, and in consultation, with the IDEM Geology Section until a formal revision of the Methane Monitoring Program can be compiled and submitted for approval.

For questions regarding this guidance contact Bill Robinson at 317/233-1055.

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