RCRA Subtitle D: Landfill Standards, Monitoring, and Closure

RCRA Subtitle D is the part of the Resource Conservation and Recovery Act that governs non-hazardous solid waste in the United States. Enacted in 1976, it banned open dumping, set minimum federal standards for landfills and other disposal facilities, and required every state to develop an EPA-approved solid waste management plan.¹ The federal rules set a floor. States build their own permitting and enforcement programs on top of that floor, and many go further than the baseline requires.

What Waste Subtitle D Covers

Under RCRA, “solid waste” means garbage, refuse, sludge from wastewater or air pollution control facilities, and other discarded material from industrial, commercial, mining, agricultural, and community activities.² The name misleads. Liquids and semi-solids count too.

Waste that does not meet the hazardous classification under Subtitle C falls into Subtitle D. That covers the great majority of what the country throws away: household trash, yard waste, manufacturing byproducts, and demolition rubble. Municipal solid waste landfills can also accept commercial waste, non-hazardous sludge, waste from very small quantity generators, and industrial solid waste alongside ordinary household garbage.³

Some materials get pushed into Subtitle D even when their chemistry might suggest otherwise. Household hazardous waste like leftover paint or pesticides from a home is not regulated under Subtitle C. Waste from very small quantity generators follows the same path. Mining overburden returned to the mine site, and agricultural crop and animal waste used as fertilizer, are excluded from hazardous classification and managed under state Subtitle D programs.⁴

The Open Dumping Ban

The core requirement of Subtitle D is the prohibition on open dumps. Every approved state plan must ban new open dumps and require closure or upgrading of every existing one.⁵ Before RCRA, disposal often meant a hole in the ground. The ban is what forced the shift to engineered landfills with liners, monitoring, and closure obligations.

The line between a sanitary landfill and an open dump lives in 40 CFR Part 257 for general solid waste facilities and 40 CFR Part 258 for municipal solid waste landfills. A facility that fails those criteria is, by definition, an open dump and must either come into compliance or shut down.⁶

How States and EPA Share the Work

Subtitle D runs on cooperative federalism. The EPA writes the minimum rules; states carry out permitting, inspection, and enforcement. This differs from Subtitle C, where the EPA has direct permitting authority. For non-hazardous waste, Congress deliberately put states in the driver’s seat.

Each state submits a solid waste management plan to the EPA. The plan must identify the agencies responsible for implementation, prohibit new open dumps, require that solid waste be recovered or disposed of in a sanitary landfill, and provide for closing or upgrading every existing open dump.⁵ The EPA has six months to approve or disapprove a plan and reviews approved plans periodically. If a plan drifts out of compliance with updated federal requirements, the EPA can withdraw approval after public notice and a hearing, which cuts off federal financial and technical assistance until the state fixes the problem.⁷

Approved states must show they can collect compliance information, conduct inspections, enter sites, and impose remedies including court orders and civil penalties.⁸ Many states adopt regulations stricter than the federal floor. Permitting rules, monitoring frequency, and acceptable waste types can vary from one state to the next, so anyone siting or operating a facility must check both the federal minimums and the specific state program.

Tribal lands work differently. RCRA does not include a provision allowing tribes to receive delegated program authority the way states can, so the EPA directly implements Subtitle D on tribal lands. The Part 257 and Part 258 minimums apply to facilities in Indian country, and the EPA can issue site-specific rules to give operators flexibility comparable to what state-approved programs offer.⁹

What Municipal Solid Waste Landfills Must Do

The most detailed Subtitle D regulations sit in 40 CFR Part 258, which governs municipal solid waste landfills (MSWLFs). Part 258 covers where a landfill can be built, how it must be constructed, how it is operated, and what happens for decades after it closes.¹⁰

Where a Landfill Can Sit

Part 258 prohibits MSWLFs in locations that raise the environmental or safety risk regardless of design quality. The restricted areas include airport safety zones, 100-year floodplains, wetlands, active fault areas, seismic impact zones, and unstable terrain.¹⁰ A landfill in the wrong spot can crack, flood, or leak no matter how well built.

Liner Systems and Leachate

New MSWLF units and lateral expansions require a composite liner and a leachate collection system. The composite liner has two components: an upper flexible membrane liner at least 30 mils thick, and a lower layer of compacted soil at least two feet deep with hydraulic conductivity no greater than 1 × 10⁻⁷ cm/sec. The leachate collection system on top must keep liquid buildup below 30 centimeters over the liner surface.¹⁰ The system captures the contaminated liquid that percolates through decomposing waste before it can reach groundwater.

Daily Operations

Operators must cover disposed waste with at least six inches of earthen material at the end of every operating day. Daily cover controls pests, reduces fire risk, limits odor, and keeps litter on-site.¹⁰ State directors can approve alternatives to soil. The regulations also bar MSWLFs from accepting regulated hazardous waste, bulk liquids, and certain other materials.

Groundwater Monitoring and Corrective Action

Every MSWLF must install a groundwater monitoring system with enough wells, in the right places and at the right depths, to detect whether contaminants are moving from the waste into the uppermost aquifer.¹⁰ A narrow exemption is available: the state director can suspend monitoring if the operator demonstrates, through site-specific analysis certified by a qualified groundwater scientist, that there is no potential for contaminant migration during the active life and post-closure care period.¹¹ Few facilities qualify.

Routine detection monitoring tests for the constituents listed in Appendix I to Part 258, covering heavy metals like arsenic, lead, chromium, and cadmium, and organic compounds like benzene, vinyl chloride, and trichloroethylene.¹² If monitoring shows a statistically significant increase over background levels, the facility moves into assessment monitoring, which tests for a much broader list.

When assessment monitoring confirms an exceedance of groundwater protection standards, the clock starts. Within 14 days, a notice identifying the problem constituents goes into the operating record and the state director is notified. Within 90 days, the operator must begin assessing corrective measures, weighing potential remedies for effectiveness, reliability, implementation difficulty, timeline, and cost.¹³

Before selecting a remedy, the operator must hold a public meeting to discuss the assessment with affected community members. The remedy chosen must protect health and the environment, meet the groundwater protection standard, and control the source of contamination to the greatest extent practicable. The operator then carries out the remedy on a defined schedule while continuing to monitor.¹³ This is where most of the real money in landfill management gets spent.

Closure, Post-Closure Care, and Financial Assurance

When a landfill unit stops accepting waste, the operator must install a final cover designed to minimize both water infiltration and erosion. The cover must have permeability equal to or less than the bottom liner (or no greater than 1 × 10⁻⁵ cm/sec, whichever is lower), an infiltration layer of at least 18 inches of earthen material, and an erosion layer of at least 6 inches capable of supporting plant growth.¹⁴ State directors can approve alternative cover designs for small facilities that handle 20 tons per day or less, taking local climate and geology into account.

After closure, post-closure care runs for at least 30 years. That includes maintaining the final cover, operating the leachate collection system, and continuing groundwater monitoring.¹⁵ The 30-year period is a floor. State directors can shorten it if the operator shows a reduced period still protects health and the environment, or extend it indefinitely when conditions warrant. Landfills that are still contaminating groundwater, or where the waste mass has not stabilized, routinely see their post-closure obligations extended well past 30 years.

Landfills close when they run out of space, but they can also close when the operator runs out of money. Part 258 requires every MSWLF owner or operator to demonstrate that funds will be available for closure, post-closure care, and corrective action. Allowable financial instruments include:

A trust fund held by a trustee.
A surety bond from a third party guaranteeing payment or performance.
An irrevocable letter of credit from a bank.
An insurance policy covering closure and post-closure costs.
A corporate or local government financial test showing sufficient strength to self-fund the obligations.
A corporate or local government guarantee from a parent or governmental entity.
A state-approved mechanism or state assumption of responsibility.

Mechanisms guaranteeing performance rather than payment cannot be combined with other instruments.¹⁶ The cost estimates behind these assurances must be updated periodically, and the financial instruments have to stay in place throughout the post-closure care period.

Landfill Gas

Decomposing waste generates methane, which is both a potent greenhouse gas and an explosion risk. Subtitle D itself focuses on waste management and groundwater; the Clean Air Act layered air emission requirements on top of the same facilities. MSWLFs above certain size and emission thresholds must install gas collection and control systems under EPA’s New Source Performance Standards.

An active landfill triggers the gas collection requirement when non-methane organic compound emissions reach 34 megagrams per year, or when surface monitoring detects methane concentrations at or above 500 parts per million. Closed landfills face a threshold of 50 megagrams per year.¹⁷ Once triggered, operators have 30 months to install and start up a collection and control system.

Facilities with active gas collection systems must monitor wellhead pressure, gas composition, and temperature monthly. Surface methane must be checked quarterly along the entire perimeter and across the landfill at 30-meter intervals. Any reading at or above 500 ppm above background requires corrective action. Closed landfills that go four consecutive quarters without exceeding the 500 ppm threshold can drop to annual monitoring.¹⁸

Other Waste Streams

Municipal solid waste gets the most prescriptive federal treatment, but Subtitle D also covers other non-hazardous categories where states fill in most of the detail.

Industrial landfills that do not accept household waste fall under the general criteria in 40 CFR Part 257 rather than Part 258. Part 257 excludes hazardous waste facilities (Subtitle C) and MSWLFs (Part 258), which leaves it as the catch-all for everything else.⁶ Its requirements are less prescriptive than Part 258, reflecting the wide variation in industrial waste characteristics. States fill the gap with their own permitting programs.

Concrete, wood, asphalt, drywall, and roofing shingles from building projects are regulated as Subtitle D waste. Because construction and demolition debris has a lower contamination potential than mixed municipal waste, dedicated C&D landfills often operate under less stringent state requirements than MSWLFs. One boundary worth flagging: a C&D landfill that accepts residential lead-based paint waste but no other household waste is specifically excluded from the MSWLF definition and is not subject to Part 258.³

Medical waste from hospitals, dental offices, and laboratories is non-hazardous solid waste under RCRA. Federal regulations do not classify waste as hazardous based on its infectious nature. The EPA had temporary authority over medical waste tracking under the Medical Waste Tracking Act of 1988, but that law expired in 1991. States have individually regulated medical waste since then, and their programs vary. Once medical waste is treated to render it non-infectious, through autoclaving for example, it can be disposed of as ordinary solid waste in landfills or incinerators.¹⁹

Coal Ash and PFAS

Two waste categories are reshaping Subtitle D and warrant close attention from operators.

Coal combustion residuals (CCRs), including fly ash, bottom ash, and flue gas desulfurization materials from power plants, are regulated under 40 CFR Part 257, Subpart D. The EPA’s 2015 CCR Rule established groundwater monitoring, closure, and post-closure requirements for active CCR surface impoundments and landfills at electric utilities. A 2024 final rule extended these requirements to legacy CCR surface impoundments (units that stopped receiving waste before the 2015 rule took effect) and CCR management units, pulling them into the same groundwater monitoring, corrective action, closure, post-closure care, and recordkeeping obligations.²⁰

A subsequent rule effective February 2026 extended several compliance deadlines. The deadline for completing facility evaluation reports for legacy units moved to February 2027; deadlines for preparing closure and post-closure care plans shifted to August 2031; and actual closure initiation moved to February 2032.²¹ Operators with legacy coal ash units should track these shifting dates carefully.

Per- and polyfluoroalkyl substances (PFAS) are increasingly detected in landfill leachate, and the federal response is still taking shape. The EPA has issued interim guidance on the destruction and disposal of PFAS and PFAS-containing materials, identifying landfills, thermal destruction, and underground injection as large-scale capacity technologies that can destroy PFAS or control its release.²² The guidance is interim rather than binding. No federal rule yet requires Subtitle D landfills to test for or treat PFAS in leachate, though individual states are starting to impose their own requirements.

Enforcement and Citizen Suits

Because Subtitle D delegates primary authority to states, most enforcement happens at the state level. Approved states must have authority to seek court orders halting activities that endanger health or the environment, enjoin ongoing violations, and recover civil penalties.⁸ Specific penalties and procedures vary by state. The EPA’s Subtitle D role is supervisory: it sets standards, reviews state programs, and can withdraw plan approval, but it does not directly issue permits or levy fines for non-hazardous waste facilities the way it does under Subtitle C.

RCRA also gives ordinary people a direct route into federal court. Under 42 U.S.C. § 6972, any person can file a citizen suit against a past or present owner, operator, generator, or transporter whose handling of solid waste may present an imminent and substantial endangerment to health or the environment. The provision explicitly covers non-hazardous solid waste. The plaintiff must give 90 days’ notice to the EPA, the relevant state, and the alleged violator before filing, and the suit is blocked if the government is already diligently prosecuting the same matter. Courts can award litigation costs, including reasonable attorney and expert witness fees, to the prevailing party.²³

1
U.S. Environmental Protection Agency. EPA History: Resource Conservation and Recovery Act
2
United States Environmental Protection Agency. Criteria for the Definition of Solid Waste and Solid and Hazardous Waste Exclusions
3
eCFR. 40 CFR 258.2 – Definitions
4
eCFR. 40 CFR 261.4 – Exclusions
5
Office of the Law Revision Counsel. 42 USC 6943 – Requirements for Approval of Plans
6
eCFR. 40 CFR Part 257 – Criteria for Classification of Solid Waste Disposal Facilities and Practices
7
Office of the Law Revision Counsel. 42 USC 6947 – Approval of State Plan; Federal Assistance
8
eCFR. 40 CFR Part 239 – Requirements for State Permit Program Determination of Adequacy
9
United States Environmental Protection Agency. EPA Direct Implementation of Federal Environmental Programs in Indian Country
10
eCFR. 40 CFR Part 258 – Criteria for Municipal Solid Waste Landfills
11
eCFR. 40 CFR 258.50 – Applicability
12
eCFR. Appendix I to Part 258 – Constituents for Detection Monitoring
13
eCFR. 40 CFR Part 258 Subpart E – Ground-Water Monitoring and Corrective Action
14
eCFR. 40 CFR 258.60 – Closure Criteria
15
eCFR. 40 CFR 258.61 – Post-Closure Care Requirements
16
eCFR. 40 CFR 258.74 – Allowable Mechanisms
17
eCFR. Emission Guidelines and Compliance Times for Municipal Solid Waste Landfills
18
eCFR. Standards of Performance for Municipal Solid Waste Landfills That Commenced Construction, Reconstruction, or Modification After July 17, 2014
19
U.S. Environmental Protection Agency. Medical Waste
20
Federal Register. Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities
21
Federal Register. Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities; CCR Management Unit Deadline Extension Rule
22
U.S. Environmental Protection Agency. Interim Guidance on the Destruction and Disposal of PFAS and Materials Containing PFAS
23
Office of the Law Revision Counsel. 42 USC 6972 – Citizen Suits