EPA's 2026 PFAS Disposal Interim Guidance: Three Endorsed Methods and the Gaps
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EPA's 2026 PFAS Disposal Interim Guidance: Three Endorsed Methods and the Gaps

Facility operators handling PFAS waste need to understand EPA's three endorsed destruction/disposal methods, the new CERCLA reportable quantity, and state-specific restrictions that diverge from federal baseline.

by iSi Environmental

The Problem: You Have a Stockpile. EPA Updated the Rules. Now What?

Your facility has a problem that keeps environmental compliance leads up at night: a tank of aqueous film-forming foam (AFFF) sitting in the maintenance building since DOD and the private sector stopped using it. Or maybe it’s spent granular activated carbon (GAC) from your water treatment system, now saturated with PFAS and labeled as hazardous waste. Or contaminated soil discovered during an excavation, testing positive for PFOA at concentrations that trigger regulatory action.

The question you’re asking: What are we legally required to do with this?

For years, the answer was murky. PFAS regulations were fragmented—a patchwork of federal guidance, emerging state rules, and facility-specific cleanup agreements. But on April 28, 2026, EPA published an updated Interim Guidance on the Destruction and Disposal of PFAS and Materials Containing PFAS, consolidating research through September 2025 and endorsing three destruction and disposal pathways. At the same time, the regulatory landscape has diverged sharply: Maine, Massachusetts, Washington, and California have imposed restrictions that exceed the federal baseline. And the clock is ticking—PFOA and PFOS are now CERCLA hazardous substances with a reportable quantity of just 1 pound.

This post walks through what EPA says you can do, what the three methods actually accomplish (and what they don’t), where state rules diverge, and how to structure your disposal strategy.

Three EPA-Endorsed Methods: Thermal Destruction, Subtitle C Landfill, and Injection

EPA has endorsed three large-capacity technologies for PFAS destruction or long-term control:

1. Hazardous Waste Incineration — The Destruction Path

How It Works

Hazardous waste incinerators (also called combustors or thermal treatment units) burn PFAS-containing waste in high-temperature combustion chambers, breaking apart the C–F bonds that make PFAS so persistent. Commercial incinerators, cement kilns, and some industrial boilers equipped with RCRA permits can accept PFAS waste.

EPA’s Position

EPA’s 2026 guidance states that “permitted hazardous waste combustors that operate under certain conditions show promise” for destroying PFAS and minimizing air emissions. New research indicates that combustion temperatures above 800°C (some sources cite higher thresholds), combined with longer residence times (3–4 seconds or more in the flame zone) and well-controlled oxidant levels, can achieve effective destruction while limiting harmful byproduct formation.

The Performance Standard

Under 40 CFR 264.343 (RCRA Subpart O performance standards for incinerators), permitted combustors must achieve a destruction and removal efficiency (DRE) of 99.9999%—six nines—for principal organic hazardous constituents (POHCs) in regulated waste streams. This is the same standard applied to other hazardous organic compounds. If nine PFAS compounds are finalized as RCRA hazardous constituents (still pending a final rule as of April 2026), they will fall under this standard.

What Gets Destroyed

Incineration works for:

  • AFFF concentrate stockpiles (undiluted foam)
  • Spent granular activated carbon (GAC) from water treatment systems
  • Contaminated soils (if thermally treated)
  • Ion-exchange resins saturated with PFAS
  • Rinsewater and treatment residues

The Byproduct Problem

Here’s where the picture gets complicated. When PFAS burn, the C–F bonds break, releasing hydrogen fluoride (HF), a toxic air pollutant. HF is regulated under EPA’s National Emission Standards for Hazardous Air Pollutants (NESHAP) from hazardous waste combustors (40 CFR Part 63 Subpart EEE). The incinerator must have air pollution control equipment—activated carbon scrubber, dry scrubber, or wet scrubber—to capture the HF before it exits the stack.

Additionally, if the waste contains chlorine (some AFFF formulations do), incomplete combustion can produce chlorofluorocarbons (CFCs) or chlorofluoroethers—chemicals linked to ozone depletion. Tight operational control (temperature, air supply, mixing) is essential to prevent this.

Cost & Timeline

Incineration of PFAS waste typically runs $500–2,000 per gallon for AFFF concentrate, or $300–1,500 per ton for solid waste (GAC, resin, soil), depending on waste composition, facility location, and current combustor availability. The waste must be transported under hazardous waste manifest, which adds 2–4 weeks of logistical lead time. An incineration facility typically accepts waste within 4–8 weeks if capacity is available.

Key Limitation

The biggest uncertainty: EPA hasn’t published compound-specific destruction efficiency data for individual PFAS (PFOA, PFOS, PFBS, GenX, etc.) under real-world combustor conditions. The guidance says “promising,” which is code for “we believe this works, but we’re still monitoring.” Facilities choosing incineration should expect their permitted incinerator to have operational procedures specific to PFAS (temperature setpoints, residence time targets, air pollution control settings) in its permit. Ask the vendor for these details upfront.

2. RCRA Subtitle C Hazardous Waste Landfills — The Containment Path

How It Works

RCRA Subtitle C hazardous waste landfills are engineered facilities with multiple barriers to isolate waste from the environment. These landfills are not “regular” municipal solid waste landfills; they are purpose-built for hazardous waste and subject to strict federal requirements.

The Engineering Requirements

Every Subtitle C landfill must have (40 CFR 264 Subpart N):

  • Double composite liner: A bottom layer of clay (at least 1 meter thick, hydraulic conductivity ≤10⁻⁷ cm/s) topped by a synthetic membrane, typically high-density polyethylene (HDPE), at least 1.5 millimeters thick.
  • Leachate collection and removal system (LCRS): A network of pipes and gravel above the bottom liner that collects liquid that percolates through the waste and removes it before it contacts the liner.
  • Leak detection system: Sensors and monitoring wells between the two liners to detect any breaches.
  • Groundwater monitoring wells: To test whether contamination has reached the aquifer.
  • Financial assurance: The facility owner must post a bond or letter of credit to fund 30 years of post-closure care and groundwater monitoring.

EPA’s Position

EPA’s 2026 guidance recommends RCRA Subtitle C landfills, especially for high-concentration PFAS waste streams, because the engineering controls minimize the potential for PFAS to escape into leachate and groundwater.

Important Distinction: Containment, Not Destruction

This is critical: landfill disposal is not a destruction method. PFAS are extremely persistent—once buried, they remain in the waste mass indefinitely. The landfill is a containment barrier, buying you time and minimizing leakage. But if the liner fails, or if the facility is eventually closed and the cap is breached, PFAS can leach into groundwater.

What Gets Landfilled

Landfill disposal is used for:

  • Spent granular activated carbon (GAC)—the most common waste stream for this path
  • Ion-exchange resins
  • Contaminated soils with moderate to high PFAS content
  • AFFF-contaminated materials (though incineration is preferred if available)

Cost & Timeline

Disposal in a RCRA Subtitle C landfill typically costs $200–800 per ton, depending on the waste composition and landfill location. Lead times are usually 2–4 weeks after waste characterization and manifesting.

The State Complication

Here’s where federal baseline and state rules begin to diverge. Maine now requires landfill operators to test leachate for PFAS and report annually to the state (effective September 2024). Massachusetts is restricting PFAS-contaminated biosolids and asking whether GAC disposal in state landfills is sustainable. Washington is gearing up for biosolids regulations starting in 2027, with PFAS being a focus. California classifies PFAS as a hazardous substance and restricts disposal to Subtitle C facilities only—no municipal solid waste (MSW) landfills.

If your facility operates in multiple states, or if you’re sending waste to a landfill in another state, you must confirm that the receiving facility will accept PFAS-containing waste. Some operators are now self-restricting PFAS intake due to future liability concerns.

3. Class I Underground Injection Wells — The Long-Term Storage Path

How It Works

Underground injection control (UIC) is a federal program under the Safe Drinking Water Act (SDWA) that allows certain types of waste to be injected deep underground—typically below 1,500 feet and well below the lowest underground source of drinking water (USDW). Class I non-hazardous industrial waste wells are the permitted vehicle for PFAS-containing liquid waste.

EPA’s Position

EPA’s 2026 guidance identifies Class I injection wells as an option for long-term storage of PFAS-containing liquids, especially reverse-osmosis (RO) concentrate and ion-exchange regeneration brine. Injection provides minimal potential for environmental release because the waste is isolated in a deep, enclosed formation.

Operational Requirements

To operate a Class I injection well for PFAS waste:

  • Well integrity must be certified annually (mechanical integrity test, pressure test, chemistry compatibility review).
  • Groundwater monitoring is required in confining zones above and below the injection interval.
  • Wastewater must be pre-treated to remove particulates, corrosive materials, and suspended solids.
  • Injection pressure must not initiate fractures or compromise confining rock.

Cost & Timeline

Injection well disposal for liquid waste is typically $1–5 per gallon, depending on the region and whether pre-treatment is required. Timeline is 4–8 weeks after characterization.

Geographic Constraint

Injection well capacity is geology-dependent. Kansas, Oklahoma, Texas, and other parts of the Great Plains have suitable deep formations and existing Class I infrastructure. The Northeast, Pacific Northwest, and much of the Midwest have limited or no injection well capacity. If your facility is in an area without injection wells (e.g., New England, California, Washington), this option is not available.

The CERCLA Uncertainty

Here’s a growing concern: PFOA and PFOS are now CERCLA hazardous substances (as of July 8, 2024). The EPA UIC program and state regulatory agencies are grappling with an open question: can you legally inject a CERCLA hazardous substance into the subsurface if it’s under the UIC program (not RCRA)? EPA hasn’t issued final guidance on this issue. Most current Class I permits allow non-hazardous industrial waste, and PFAS may not qualify under that definition going forward. Facilities considering injection wells should start permitting conversations with state UIC authorities now, as this regulatory question will likely be clarified by late 2026.

The CERCLA Trigger: 1 Pound in 24 Hours

On July 8, 2024, EPA designated perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—including all salts and structural isomers—as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).

The Reportable Quantity: 1 Pound

EPA set the reportable quantity (RQ) at 1 pound. This is the lowest RQ EPA has ever promulgated under CERCLA. To put it in perspective:

  • TCDD (dioxin) = 1 gram (0.0022 pounds)
  • Lead compounds = 10 pounds
  • PCBs = 1 pound
  • PFOA/PFOS = 1 pound

What This Means

Any release of 1 pound or more of PFOA or PFOS in any 24-hour period triggers immediate notification obligations:

  1. National Response Center: Call 1-800-424-8802 (available 24/7)
  2. State or Tribal Emergency Response Commission: File written notification
  3. Local Emergency Planning Committee: File written notification

The report must be made immediately (same call or within 24 hours if immediate contact is unavailable). Failure to report is a federal violation with potential civil and criminal penalties.

What Counts as a Release

A “release” includes spills, leaks, discharges, disposal, abandonment, or any other uncontrolled loss of PFAS to the environment. Examples:

  • A storage tank corrosion leak that allows AFFF to seep into soil (even 1 gallon of undiluted AFFF concentrate contains roughly 2–5 pounds of PFOA/PFOS, depending on formulation)
  • A landfill leachate plume detected at a site boundary
  • A transportation accident during waste shipment
  • A spill during transfer between containers

Facility Implications

If your facility has a PFAS-containing waste stream (AFFF, spent GAC, RO concentrate, contaminated soil), you are now exposed to CERCLA liability. A single unplanned release of ≥1 pound triggers federal reporting and potential Superfund liability. This heightens the importance of:

  • Proper waste storage (integrity inspections, secondary containment)
  • Timely disposal (don’t let waste accumulate indefinitely)
  • Emergency preparedness (know how to report and to whom)
  • Waste characterization (know the PFAS concentration of your waste so you can calculate whether a spill exceeds the RQ)

The Pending RCRA Hazardous Waste Listing: Still Uncertain as of April 2026

In February 2024, EPA proposed listing nine PFAS compounds as RCRA hazardous constituents:

  1. PFOA
  2. PFOS
  3. PFBS (perfluorobutanesulfonic acid)
  4. GenX (hexafluoropropylene oxide dimer acid)
  5. PFNA (perfluorononanoic acid)
  6. PFHxS (perfluorohexanesulfonic acid)
  7. PFDA (perfluorodecanoic acid)
  8. PFHxA (perfluorohexanoic acid)
  9. PFBA (perfluorobutanoic acid)

The comment deadline was April 8, 2024. As of April 2026, EPA has not published a final rule.

Important Legal Distinction

Listing as a “hazardous constituent” is not the same as listing as a “hazardous waste.” A constituent listing supports corrective action at contaminated sites but does not automatically make all wastes containing these compounds subject to RCRA Subtitle C regulations. A separate “hazardous waste designation” rulemaking would be required for that to occur.

Current Status

Until EPA issues a final hazardous waste designation, facilities are not required to manage nine-PFAS-containing waste under RCRA Subtitle C (though some are doing so voluntarily for liability protection). However, industry observers expect finalization in late 2026 or early 2027. Facilities should plan on the assumption that RCRA regulations for nine PFAS will eventually apply, which would require:

  • Waste characterization (testing for nine PFAS)
  • Hazardous waste generator classification (based on waste volume and concentration)
  • Manifest and disposal at permitted facilities
  • Record-keeping and biennial reporting (if generator)

State Divergence: Where Federal Baseline Breaks Down

EPA’s interim guidance represents the federal floor, but state regulations are creating a more restrictive ceiling in several key regions:

Maine: Landfill Leachate Testing (Effective September 2024)

Maine now requires landfill operators to test leachate for PFAS and report results annually to the state. Maine also banned land application of sewage sludge in 2022 (sludge is now sent to landfills instead, increasing disposal pressure). The implication: if you have spent GAC or other PFAS waste to dispose of, Maine landfills will accept it, but operators are now monitoring for PFAS leakage. This adds a compliance layer but doesn’t prohibit disposal—yet.

Massachusetts: Biosolids Restrictions and Emerging Pressure

Massachusetts banned land application of PFAS-contaminated biosolids. The state has also been sending biosolids to Casella’s Hawk Ridge composting facility in Maine, but the operator is planning closure due to PFAS restrictions. This demonstrates how regional waste infrastructure is under stress. For PFAS waste generators in Massachusetts, options are tightening: incineration or Subtitle C landfill in Massachusetts (if available) or in neighboring states.

Washington: Biosolids Sampling Framework (SB 5033)

Washington requires biosolids-generating facilities to sample quarterly for PFAS starting January 1, 2027. By July 1, 2026, the Department of Ecology will issue guidance on PFAS sampling. In 2029, the legislature will receive a report on contamination levels and possible disposal solutions. No explicit landfill ban yet, but this data gathering is laying the foundation for restrictions. Additionally, new landfill permits issued after August 1, 2027 require state Ecology approval, and the state is updating solid waste regulations to address emerging contaminants including PFAS.

California: Hazardous Substance Classification

California’s Department of Toxic Substances Control (DTSC) and State Water Resources Control Board classify PFAS as a hazardous substance. This restricts landfill disposal of PFAS-contaminated soil and residues to RCRA Subtitle C facilities—no municipal solid waste (MSW) landfills. If you’re operating in California and generating PFAS waste, your disposal options are limited to permitted hazardous waste facilities (incineration or Subtitle C landfill). Costs are typically 20–30% higher than in other regions.

Great Plains: Limited Restrictions, Self-Restricting Operators

Kansas, Missouri, Oklahoma, and Texas do not yet have statewide explicit bans on PFAS landfill disposal. However, some individual MSW landfill operators are self-restricting PFAS intake due to liability concerns. EPA Region 7 (covering Kansas and Nebraska) is supporting technical assessments of PFAS in drinking water systems, suggesting that state-level restrictions may follow once contamination is quantified.

Implication for Multi-State Operations

If your company operates facilities in multiple states or sends waste across state lines, you must manage different disposal regulations in each jurisdiction. A load of spent GAC acceptable in Kansas may not be accepted by California landfills. Disposal costs and lead times vary significantly. Build state-specific disposal strategies, not a one-size-fits-all approach.

The Three Waste Streams: Cost, Timeline, and Decision Tree

Waste Stream 1: AFFF Concentrate Stockpile

Volume Typical: 50–5,000 gallons (depending on facility size and history of use)

PFAS Content: 2–8% by weight (4–16 mg/mL); a 1,000-gallon tank contains 30–60 pounds of PFOA/PFOS equivalent

Recommended Disposal: Hazardous waste incineration (preferred); RCRA Subtitle C landfill if incineration unavailable

Cost: $500–2,000/gallon (incineration); $200–800/gallon (Subtitle C landfill)

Timeline: 4–8 weeks (manifesting, transport, processing)

Regulatory Trigger: Any spill ≥1 pound PFOA/PFOS = CERCLA RQ notification

Action: Contact 3–5 incineration vendors now for pricing. If incineration capacity is constrained in your region, book early. Confirm vendor can handle your specific AFFF formulation (some contain DOC or other additives).

Waste Stream 2: Spent Granular Activated Carbon (GAC)

Volume Typical: 100–500 pounds per year (depending on water treatment volume and PFAS concentration in source water)

PFAS Content: GAC becomes saturated; retains 10–50% PFAS by weight

Recommended Disposal: RCRA Subtitle C landfill (predominant); thermal reactivation (limited availability; only a few vendors offer this)

Cost: $300–900/ton (Subtitle C landfill); $500–1,500/ton (thermal reactivation)

Timeline: 2–4 weeks

State Variability: Maine and Massachusetts landfills still accepting with new leachate monitoring; California restricts to Subtitle C only; Great Plains has fewer restrictions

Action: Quantify your GAC generation rate (gallons of water treated per pound of GAC used). Budget for increasing disposal costs. If operating in California, identify a Subtitle C facility now—capacity may be limited. Monitor state PFAS regulations for any new restrictions that might affect your current disposal path.

Waste Stream 3: Reverse-Osmosis (RO) Concentrate

Volume Typical: 10–20% of treated water volume (e.g., 100 GPD RO system produces 10–20 GPD concentrate)

PFAS Content: Highly variable (1–100+ µg/L), depending on source water concentration and treatment system efficiency

Recommended Disposal: Class I injection well (if available); further treatment (sorption, ion exchange); RCRA Subtitle C liquid waste storage (temporary; not long-term)

Cost: $1–5/gallon for injection; $2–10/gallon for further treatment

Geographic Dependency: Injection wells available in Kansas, Oklahoma, Texas, parts of Colorado; not available in Northeast, California, Pacific Northwest

Action: Determine your facility’s location and whether Class I injection well capacity exists. If yes, begin permitting discussions with state UIC authority. If no, develop a strategy for further treatment or temporary storage while seeking incineration or other options.

Waste Stream 4: Contaminated Soil

Volume Typical: Hundreds of tons (highly variable; depends on excavation scope)

PFAS Concentration: EPA soil screening levels not yet finalized; guidance suggests 1–10 µg/kg as trigger for further investigation

Recommended Disposal: Excavation + RCRA Subtitle C landfill (most common); thermal treatment/incineration (high cost, limited capacity); in-situ stabilization (research-phase, not widely available)

Cost: $100–500/ton (including excavation, characterization, transportation, landfill disposal)

Timeline: 2–3 months (depending on excavation scope and manifesting volume)

State Variability: California restricts to Subtitle C; Maine, Massachusetts, Washington have emerging restrictions; Great Plains less restrictive

Action: Conduct Phase I or Phase II environmental site assessment (ESA) if contamination is suspected. Get waste characterization (TCLP or other EPA method) before contacting disposal vendors. Landfill capacity for large volumes (1,000+ tons) requires advance notice.

iSi’s Role: Waste Characterization, Vendor Evaluation, and CERCLA Readiness

For facilities facing a PFAS disposal decision, the path forward involves three critical steps:

1. Waste Characterization Know your waste: concentration of PFOA, PFOS, and other PFAS; volume; composition (is it pure AFFF, or AFFF mixed with water or other materials?); moisture content. Testing cost: $500–2,000 per sample. This information drives disposal method selection, vendor bidding, and CERCLA RQ assessment.

2. Disposal Vendor Evaluation Contact multiple vendors (incineration, landfill, injection, reactivation). Request proposals that specify accepted waste type, processing timeline, cost per unit, air emissions data (for incineration), and post-disposal certification. Evaluate vendor credentials (RCRA permits, ISO certifications, insurance). Cost to evaluate: included in vendor proposals (usually no fee to request quote).

3. CERCLA Reporting and Emergency Preparedness Document your facility’s PFAS waste streams, storage locations, and estimated quantities. Brief your emergency response team on the 1-pound CERCLA RQ and the National Response Center contact procedure. Conduct an integrity inspection of AFFF storage tanks and GAC containers. Cost: internal labor; low cost but high value.

iSi Environmental provides expertise in all three areas:

  • Waste characterization: EDR historical records, soil testing coordination, waste analysis
  • Vendor evaluation: Multi-vendor RFQ, negotiation support, contract review
  • CERCLA readiness: Facility PFAS inventory, emergency response planning, notification protocol

Key Takeaways

  1. EPA’s 2026 Interim Guidance endorses three methods: incineration (destruction), Subtitle C landfill (containment), and injection wells (storage). Each has trade-offs.

  2. Incineration is the only true destruction method, but byproduct control (HF capture, avoiding CFC formation) is essential. The final rule on nine-PFAS RCRA hazardous waste designation is still pending, expected late 2026 or early 2027.

  3. CERCLA RQ of 1 pound is unprecedented. Any facility with PFAS waste is now exposed to federal reporting liability if a release occurs. Know your waste concentration and storage integrity.

  4. State rules are diverging rapidly. Northeast and West Coast states (Maine, Massachusetts, Washington, California) are restricting PFAS disposal; Great Plains states are less restrictive but may follow as contamination data accumulates.

  5. Disposal costs and timeline vary by method and location. Incineration: $500–2,000/gallon (AFFF), 4–8 weeks. Subtitle C landfill: $200–900/ton, 2–4 weeks. Injection wells: $1–5/gallon (if available), 4–8 weeks. Multi-state operations must manage multiple regulatory frameworks.

  6. Start disposal planning now. Incineration capacity is constrained in many regions. Landfill operators are becoming more selective about PFAS intake. Injection well permitting is complex. Delay increases cost and limits options.

What’s Next?

If your facility is managing PFAS waste, contact iSi Environmental to:

  • Characterize your waste streams (concentration, volume, composition)
  • Evaluate disposal options (cost, timeline, regulatory fit)
  • Support CERCLA reporting and emergency preparedness
  • Navigate state-specific restrictions if you operate multi-state

The regulatory landscape will continue to shift—RCRA final rule expected late 2026, state restrictions tightening in 2027. Being proactive today protects your facility tomorrow.

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