Requirements for Municipal Solid Waste Landfills (MSWLFs)
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Groundwater Monitoring Requirements
Nearly all MSWLFs are required to monitor the underlying groundwater for contamination during their active life and post-closure care periods. The exceptions to this requirement are small landfills that receive less than 20 tons of solid waste per day, and facilities that can demonstrate that there is no potential for the migration of hazardous constituents from the unit into the groundwater. All other MSWLFs must comply with the groundwater monitoring requirements found at Title 40 of the Code of Federal Regulations (CFR) Part 258, Subpart E–Ground-Water Monitoring and Corrective Action.
Facility owners and operators must install a groundwater monitoring system that can collect samples from the uppermost aquifer (i.e., defined as the geological formation nearest the natural surface that is capable of yielding significant quantities of groundwater to wells or springs) to monitor groundwater. The groundwater monitoring system consists of a series of wells placed up-gradient and down-gradient of the MSWLF. The samples from the up-gradient wells show the background concentrations of constituents in the groundwater, while the down-gradient wells show the extent of groundwater contamination caused by the MSWLF. The required number of wells, spacing and depth of wells is determined on a site-specific basis based on the aquifer thickness, groundwater flow rate and direction, and the other geologic and hydro-geologic characteristics of the site. All groundwater monitoring systems must be certified by a qualified groundwater scientist and must comply with the sampling and analytical procedures outlined in the regulations.
- Detention Monitoring
MSWLF owner/operators monitor for the 62 constituents listed in Appendix I of 40 CFR Part 258 during the detection monitoring phase. This consists of sampling at least semiannually throughout the facility's active life and post-closure care period. The frequency of sampling is determined on a site-specific basis by the state regulatory agency.
If one of the 62 constituents is detected at a statistically significant higher level than the established background level during the detection monitoring phase, the MSWLF owner/operators must notify the state regulatory agency. The facility must establish an assessment monitoring program within 90 days, unless the owner/operators can prove that the detection of the constituent(s) was the result one of the following reasons:
- sampling, analysis, or statistical evaluation error (i.e., a false positive result);
- a natural fluctuation in groundwater quality;
- or caused by another source
- Assessment Monitoring
A MSWLF must begin an assessment monitoring program within 90 days of detecting a statistically significant increase in the constituents listed in Appendix I constituents. Samples must be taken from all wells and analyzed for the presence of all 214 constituents listed in Appendix II of 40 CFR Part 258 as a first step. The owner/operators must then establish the background levels for these constituents and establish a groundwater protection standard (GWPS) for each if any of the constituents listed in Appendix II are detected.
The GWPS represents the maximum allowable constituent level in the groundwater and is based either on the Safe Drinking Water Act (SDWA) Maximum Contaminant Level (MCL) for that constituent or the background level of the groundwater at the site if no MCL exists. The background level is used for the GWPS in cases where the site-specific background level is higher than the MCL.
The owner/operators must resample for all previously detected constituents that are listed in Appendix I and Appendix II within 90 days of establishing the background levels and the GWPS. Resampling must then be repeated at least semiannually. The facility may return to the detection monitoring phase if none of the Appendix II constituents are found to exceed the GWPS for two consecutive sampling events. However, the owner/operators of the MSWLF must characterize the nature of the release, determine if the contamination has migrated beyond the facility boundary, and begin assessing corrective measures if any of the constituents are detected at a statistically significant level higher than the GWPS.
- Corrective Action
A remedy is selected and corrective action begins based upon the assessment of corrective measures. Any corrective measure selected must be protective of human health and the environment, meet the GWPS, control the source(s) of the release to prevent further releases, and manage any solid waste generated in accordance with all applicable RCRA regulations. The facility must continue these remedial actions until it has complied with the GWPS for three consecutive years and can demonstrate that all required actions have been completed.
Closure and Post-Closure Care Requirements
The closure and post-closure care requirements for MSWLFs establish the minimum requirements that MSWLF owner/operators must comply once the landfill stops receiving waste and begins closure. Owner/operators are also required to continue monitoring and maintaining the landfill once it is closed to protect against the release of hazardous constituents to the environment. The closure and post-closure care regulations can be found at 40 CFR Part 258, Subpart F - Closure and Post-Closure Care.
- Closure
Final Cover Systems
The closure standards for MSWLFs require owner/operators to install a final cover system to minimize infiltration of liquids and soil erosion. The permeability of the final cover must be less than the underlying liner system, but no greater than 1.0 x 10-5 cm/sec. This requirement helps prevent the “bathtub effect” where liquids infiltrate through the overlying cover system but are contained by a more permeable underlying liner system. This causes the landfill to fill up with water (like a bathtub), increasing the hydraulic head on the liner system that can lead to the contaminated liquid (leachate) escaping and contaminating groundwater supplies.
The final cover system must include an infiltration layer of at least 18 inches of earthen material covered by an erosion layer of at least 6 inches of earthen material that is capable of sustaining native plant growth. An alternative cover design may be used if it provides equivalent protection against infiltration and erosion. These alternative designs must be approved by the director of an approved and authorized state program.
Closure Plans
Every MSWLF is required to prepare a written closure plan that describes the steps necessary to close the unit in accordance with the closure requirements. This plan must include the following information:
- A description of the final cover design and its installation methods and procedures
- An estimate of the largest area of the landfill requiring a final cover
- An estimate of the maximum inventory of waste on site during the landfill’s active life
- A schedule for completing all required closure activities
The MSWLF must begin closure operations within 30 days once a MSWLF has received its final shipment of waste. However, the MSWLF may delay closure for up to one year if additional capacity remains. Further delays following one year requires approval from the state director. All closure activities must be completed within 180 days (with the exception of an extension from the state director) after beginning. The owner/operators must then certify that the closure has been completed in accordance with the official closure plan after closure is complete. This certification must be signed by an independent, registered professional engineer or the state director. After this, the MSWLF owner/operators must also make a notation on the property deed indicating that the land was used as a landfill and that it is restricted from future use.
- Post-Closure Care
Post-closure care activities consist of monitoring and maintaining the waste containment systems and monitoring groundwater to ensure that waste is not escaping and polluting the surrounding environment. The required post-closure care period is 30 years from site closure, but this can be shortened or extended by the director of an approved state program. That can help ensure protection of human health and the environment.
Specific post-closure care requirements consist of maintaining the integrity and effectiveness of the following:
- Final cover system
- Leachate collection system
- Groundwater monitoring system
- Methane gas monitoring system
The owner/operator of a closed MSWLF must prepare a written post-closure care plan that provides the following information:
- A description of all required monitoring and maintenance activities, including the frequency with which each activity will be performed
- The name, address and telephone number of the person to contact during the post-closure care period
- A description of planned uses of the land during the post-closure care period
Any use of the land during this period must not disturb the integrity or operation of any of the waste containment systems or the monitoring systems. The owner/operator must certify that the post-closure care has been completed in accordance with the official post-closure care plan following the post-closure care period. This certification must be signed by an independent, registered professional engineer or the state director. Once signed, the certification is placed in the facility’s operating record.
Financial Assurance
All owners/operators of MSWLFs are required to demonstrate that they can pay for the required closure and post-closure care activities, and any corrective action that might become necessary due to releases of contaminants into the surrounding environment. EPA believes that requiring these financial assurance demonstrations ensures proper long term financial planning by owner/operators so that sites will be closed properly and maintained and monitored in a manner that protects human health and the environment. State and federal government entities are exempt from these requirements.
The first step in demonstrating financial assurance is preparing a written, site-specific cost estimate. Closure and post-closure care cost estimates are prepared prior to commencement of facility operations and must be adjusted annually during the active life of the unit/facility to account for inflation. Corrective action cost estimates are prepared when a release is detected, and also must be adjusted annually during the period of the correction action. All cost estimates are calculated based upon hiring a third party to perform the required action.
Financial Assurance Mechanisms
There are several allowable financial assurance mechanisms described in the regulations (see 40 CFR §258.74) that an owner/operator may use alone, or in combination, to demonstrate that they meet the closure and post-closure care financial assurance requirements. The allowable mechanisms include the following:
- Trust Fund (40 CFR §258.74(a))
An owner/operator may establish a trust fund into which he deposits money specifically earmarked for closure, post-closure care, and/or corrective action. The owner/operator must make annual payments into the trust fund for a specified period of time, referred to as the “pay-in period.”
- Surety Bond Guaranteeing Payment or Performance (40 CFR §258.74(b))
An owner/operator may obtain a payment or performance surety bond from a surety company that guarantees that the owner/operator will pay for or perform all required closure and post-closure care. For corrective action, an owner/operator may obtain a performance bond only. If the owner/operator fails to meet the requirements specified in the bond, the surety company assumes liability and must pay for, or perform all, the required activities specified in the bond. When using a surety bond to demonstrate financial assurance, the owner/operator also must establish a standby trust fund, into which the surety company will make payments if the owner/operate fails to comply with its financial responsibilities.
- Letter of Credit (40 CFR §258.74(c))
An owner/operator may obtain an irrevocable standby letter of credit from an institution that has the authority to issue such letters and whose operations are regulated and examined by a federal or state agency. The letter of credit must be equal to the amount of the current cost estimate for closure, post-closure care, and/or corrective action.
- Insurance (40 CFR §258.74(d))
An owner/operator may obtain an insurance policy for a face value amount (the total amount the insurer is obligated to pay under the policy), at least equal to the cost estimate for closure and/or post-closure expenses. The insurance policy must guarantee that required funds will be available to close the unit and/or provide the required post-closure care at the appropriate time. Insurance is not an allowable mechanism for demonstrating financial assurance for corrective action—financial assurance for corrective action is not required until a release has been detected, and insurers will not issue a policy to cover an event which has already occurred.
- Corporate Financial Test (40 CFR §258.74(e))
An owner/operator can meet the financial assurance requirements by passing a financial test to demonstrate and document that they have sufficient assets to cover closure, post-closure care, and/or corrective action costs. Specifically, the owner/operator's tangible net worth must be greater than the sum of the current closure, post-closure care, and/or corrective action cost estimates test plus $10 million; they must have assets located in the United States amounting to at least the sum of current closure, post-closure care, and/or corrective action cost estimates; and they must satisfy one of the following three conditions:
- A current rating for its senior unsubordinated debt of AAA, AA, A, or BBB as issued by Standard and Poor's, or Aaa, Aa, A or Baa as issued by Moody's.
- A ratio of less than 1.5 comparing total liabilities to net worth.
- A ratio of greater than 0.10 comparing the sum of net income plus depreciation, depletion, and amortization, minus $10 million, to total liabilities.
- Local Government Financial Test (40 CFR §258.74(f))
If the owner/operator of the MSWLF is a local government, it may use the local government financial test to demonstrate closure, post-closure care, and/or corrective action financial assurance. To make this demonstration, a local government must satisfy either the bond rating requirement or the financial ratio alternative. The bond requirement requires the government to have an investment grade bond rating (i.e., AAA, AA, A, or BBB as issued by Standard and Poor’s, or Aaa, Aa, A or Baa as issued by Moody’s) on all outstanding general obligation bonds. The financial ratio alternative requires the government not have any outstanding general obligation bonds or only have unrated general obligation bonds, has a ratio of cash plus marketable securities to total expenditures greater than or equal to 0.05, and has a ratio of annual debt service to total expenditures less than or equal to 0.20. In determining these ratios, the government must use Generally Accepted Accounting Principles (GAAP) for governments, and have its financial statements audited by an independent certified public accountant. A government is not eligible to use this mechanism if it is currently in default on any outstanding general obligation bond; has any outstanding general obligation bonds rated lower than BBB as issued by Standard and Poor’s or Baa as issued by Moody’s; operated at a deficit equal to five percent or more of total annual revenue in each of the previous two fiscal years; or received an adverse opinion, disclaimer of opinion, or other qualified opinion from the independent certified public accountant auditing its financial statements.
- Corporate Guarantee (40 CFR §258.74(g))
An owner/operator may obtain a written guarantee from another company (the guarantor) to meet the closure, post-closure care, and/or corrective action financial assurance requirements. The guarantor must be either the parent corporation or principal shareholder of the owner/operator (i.e., a corporate parent or grandparent), a company whose parent company is also the parent company of the owner/operator (i.e., a corporate sibling), or another related or nonrelated company with a “substantial business relationship” with the owner/operator (including subsidiaries of the owner/operator). The guarantor also must meet the conditions of the corporate financial test described above. With a corporate guarantee, the guarantor promises to pay for or perform the required activities on behalf of the owner/operator if the owner/operator fails to meet its obligations.
- Local Government Guarantee (40 CFR §258.74(h))
An owner/operator may demonstrate closure, post-closure care, and/or corrective action financial assurance by securing a written guarantee from a local government. To issue such a guarantee, the local government (the guarantor) must meet the requirements of the local government financial test described above. In the guarantee, the local government promises to pay for or perform the required closure, post-closure, and/or corrective action if the owner/operator fails to do so.
- State-Approved Mechanism (40 CFR §258.74(i))
States that are authorized to implement the MSWLF criteria may designate and approve any other mechanism that an owner/operator may use to demonstrate financial assurance.
- State Assumption of Responsibility (40 CFR §258.74(j))
A state also may assume legal responsibility for a MSWLF’s closure, post-closure care, and/or corrective action expenses or assure that the required funds will be available from state sources to cover all expenses.