Kentucky's MSW Landfill State Plan Takes Over from the Federal Plan: What Operators Need to Know Before May 26, 2026

Kentucky’s existing municipal solid waste landfills have operated under EPA’s direct federal oversight since May 2021. That is about to change.

On April 23, 2026, EPA Region 4 published a proposed rule at 91 FR 21758 approving the Kentucky Energy and Environment Cabinet’s Clean Air Act Section 111(d) State Plan for existing MSW landfills. The comment period closes May 26, 2026. Once EPA finalizes the approval, the MSW Landfill Federal Plan at 40 CFR 62, subpart OOO no longer applies to Kentucky landfills. The Kentucky State Plan — codified at 401 KAR 61:036 — takes over, and the Kentucky Cabinet becomes the agency that receives annual emission rate reports, issues compliance schedules, and pursues enforcement for Subpart Cf obligations.

The underlying federal emission guideline at 40 CFR 60, subpart Cf does not change. What changes is the regulator of record. For landfill operators running Kentucky sites, that shift affects how compliance reports are submitted, who inspects, and who issues citations when something goes wrong. For multi-state operators with landfills in Kentucky plus Tennessee, Indiana, Ohio, or nearby states, each state remains on its own track.

Here is what Kentucky MSW landfill operators need to know before the May 26 comment window closes.

What EPA Is Actually Approving

Section 111(d) of the Clean Air Act requires states to develop plans implementing EPA’s Emission Guidelines (EG) for existing stationary sources. For MSW landfills, EPA finalized the revised EG on August 29, 2016 at 40 CFR 60, subpart Cf (81 FR 59276). Subpart Cf applies to existing MSW landfills that commenced construction, reconstruction, or modification on or before July 17, 2014. Landfills that began after that date are covered by the corresponding New Source Performance Standard at 40 CFR 60, subpart XXX, which is directly federally enforceable regardless of state plan status.

States were originally required to submit a state plan implementing Subpart Cf by May 30, 2017. Kentucky — like many states — missed that deadline. EPA therefore finalized the MSW Landfill Federal Plan at 40 CFR 62, subpart OOO on May 21, 2021 (86 FR 27756), and the Federal Plan has been in effect in Kentucky for existing MSW landfills since then.

Kentucky submitted its revised State Plan to EPA on June 11, 2024. The plan adopts 401 KAR 61:036, “Emission Guidelines and Compliance Times for Municipal Solid Waste (MSW) Landfills,” which became effective in Kentucky on June 3, 2021. The state regulation incorporates the applicable provisions of Subpart Cf by reference. EPA’s Technical Support Document, included in the docket for this rulemaking (EPA-R04-OAR-2025-1180), concludes that the Kentucky plan meets the relevant Section 111(d) requirements.

This is not Kentucky’s first MSW state plan. EPA approved an earlier Kentucky plan on April 20, 1999 (64 FR 19290) under the predecessor EG at 40 CFR 60, subpart Cc. The 2026 action replaces that earlier plan with one aligned to the 2016 EG revision.

The comment period is short. 33 days from the April 23 Federal Register publication.

Which Landfills Are Affected

The Kentucky State Plan, once approved, applies to Kentucky MSW landfills that meet all three conditions:

Commenced construction, reconstruction, or modification on or before July 17, 2014
Have a design capacity equal to or greater than 2.5 million megagrams AND 2.5 million cubic meters
Are currently operating under the Federal Plan at 40 CFR 62, subpart OOO

For landfills meeting those criteria, the transition is administrative. No fresh compliance demonstration is required. Existing GCCS design plans, monitoring plans, and annual reports remain valid. What changes is the agency that receives them.

Landfills that do not meet the design capacity threshold are not subject to the GCCS requirement under the EG, and the state plan transition does not change that. New MSW landfills (construction commenced after July 17, 2014) are subject to NSPS Subpart XXX, which is federally enforceable regardless of state plan status.

The 34 Megagram NMOC Threshold Still Runs the Compliance Calendar

The core Subpart Cf trigger has not changed, and the Kentucky state plan does not modify it. Every Kentucky MSW landfill above the 2.5 million megagrams / 2.5 million cubic meters design capacity threshold runs the NMOC emission rate calculation annually per 40 CFR 60.33f.

The compliance triggers:

NMOC emission rate ≥ 34 Mg/year (Tier 2 methodology): The landfill must submit a gas collection and control system (GCCS) design plan within 1 year and install and operate the GCCS within 30 months of the most recent NMOC emission rate report.
Surface methane concentration ≥ 500 ppm from the landfill surface: Same obligation — submit GCCS design plan within 1 year, install and operate within 30 months.

Neither trigger is new in 2026. Both have been in place since the 2016 EG revision.

What the state plan transition does change: the regulator of record for these obligations. After EPA finalizes the Kentucky State Plan, the annual NMOC emission rate report goes to the Kentucky Cabinet, not to EPA Region 4. GCCS design plan submittals go to the Cabinet. Compliance schedules, extensions, and enforcement follow the state authority.

Why NMOC Calculation Errors Are the Most Common Citation

EPA has issued a public Enforcement Alert specifically flagging MSW landfills that violated the NMOC emission rate calculation requirements. The pattern the Enforcement Alert describes: landfills under-reporting NMOC emissions, missing the 34 Mg/yr threshold on paper when the actual emissions were above it, and therefore failing to install GCCS on the required schedule or running an inadequately designed GCCS relative to actual gas generation.

Other recurring Subpart Cf citations include:

Missing or late annual emission rate reports
Surface methane exceedances (>500 ppm) not triggering the required design plan submittal
GCCS operational shortfalls — inadequate vacuum at wells, temperature of decomposition above the threshold at wells, NMOC destruction efficiency below the required 98% (or equivalent)
Inadequate documentation supporting landfill gas heat input, energy production, or flaring claims

After the Kentucky state plan takes effect, the same compliance categories will be enforced by the Kentucky Cabinet rather than EPA Region 4. The technical content of what is enforced does not change.

The Kentucky transition is a natural moment to re-verify the NMOC calculation methodology at every covered landfill. A calculation that was marginal under Federal Plan reporting will be marginal under State Plan reporting. Operators who have not had an outside review of the NMOC calculation in 3+ years should treat the May 26, 2026 window as the deadline to do so.

What the Federal-to-State Transition Actually Changes

The practical mechanics shift across four areas:

Reports and submittals. Annual NMOC emission rate reports, GCCS design plan submittals, and compliance notifications that currently route to EPA Region 4 in Atlanta will, after final approval, route to the Kentucky Energy and Environment Cabinet. Operators should confirm the submittal channels and correct agency contact before the first state-era report cycle.

Inspections. Inspections of Kentucky landfills will be conducted by the Kentucky Cabinet’s Division for Air Quality inspectors rather than EPA Region 4. State inspectors have delegated enforcement authority and work from the same Subpart Cf technical content, but local practice and inspection priorities may differ from federal practice.

Compliance schedules. Any open compliance schedules under the Federal Plan should be explicitly mapped to the State Plan on transition. Operators with active GCCS design plans in process should confirm with EPA Region 4 whether those schedules transfer automatically or require explicit re-filing with the Cabinet.

EPA’s retained authority. EPA Administrator retains approval authority for alternative methods to determine NMOC concentration or a site-specific methane generation rate constant (k) per 40 CFR 60.30f(c). A landfill that submitted an alternative-method request under the Federal Plan does not lose that authority on transition. A landfill that wants to submit a new alternative-method request after transition submits it to EPA, not to the Cabinet.

The Multi-State Operator View

If you operate landfills in Kentucky plus one or more neighboring states, the Kentucky transition does not flow through to sister sites. Each state runs its own state plan status:

Tennessee: operates under an approved state plan at 40 CFR 62, subpart RR
Indiana: operates under an approved state plan
Ohio: operates under an approved state plan
Illinois: operates under an approved state plan
Virginia, West Virginia: each handled through EPA Region 3 state plan actions
Missouri: operators should verify current status through MDNR

For a corporate EHS team standardizing landfill compliance across multiple states, the transition in Kentucky is a good moment to confirm the state-by-state map. A landfill in Louisville now answers to the Kentucky Cabinet. A landfill across the river in Clarksville, Indiana continues to answer to IDEM. The technical content of Subpart Cf is the same at both sites; the agency, the inspectors, and the submittal channels are different.

What the Current Deregulatory Cycle Does and Does Not Touch

EPA’s Q2 2026 deregulatory cycle has moved on air-rule fronts including MATS (final repeal effective April 27, 2026), the GHG Endangerment Finding (rescission final February 12, 2026), NSPS OOOOb/c for oil and gas (narrow technical amendments signed April 4, 2026), the EtO Commercial Sterilization NESHAP (reconsideration proposed March 17, 2026), and several sector NESHAPs still in reconsideration.

The MSW Landfill EG at Subpart Cf is not on the current reconsideration list. For now, Subpart Cf is stable. The Kentucky state plan action is a routine administrative approval — it does not signal a deregulatory direction on landfill methane or NMOC controls.

Operators should not use the Kentucky transition as a reason to draw down compliance effort. The 34 Mg/yr NMOC threshold, the 500 ppm surface methane trigger, and the GCCS operational requirements remain in force, and EPA’s Enforcement Alert on NMOC calculation violations remains current.

Practical Steps Before May 26, 2026

For every Kentucky MSW landfill operator, the transition window is the right moment to run the following checklist:

Confirm Subpart Cf applicability. Verify the landfill’s first construction / reconstruction / modification date is on or before July 17, 2014 and design capacity is ≥ 2.5 million megagrams and ≥ 2.5 million cubic meters. Document the determination.
Re-verify the NMOC emission rate calculation. Use Tier 1, Tier 2, or Tier 4 methodology per 40 CFR 60.35f. If the Tier 2 rate is close to 34 Mg/yr, get an outside review before transition.
Re-verify GCCS operational status. For landfills above the 34 Mg/yr threshold (or with surface methane above 500 ppm), confirm the GCCS is operating per Subpart Cf — vacuum at wells, temperature, destruction efficiency, monitoring cycles.
Update internal SOPs and compliance calendar. Annual reports, design plan submittals, and notifications that currently route to EPA Region 4 need to be mapped to the Kentucky Cabinet after final approval.
Reconfirm the audit trail for prior Federal Plan compliance. Any open compliance schedules or active GCCS design plans need to carry cleanly into the state program.
Comment if needed. If your landfill has an implementation concern — technical, transitional, or regulatory — the comment window closes May 26, 2026 through docket EPA-R04-OAR-2025-1180 on Regulations.gov.

When iSi Steps In

iSi supports Kentucky and multi-state MSW landfill operators with NMOC emission rate calculations, GCCS design plan preparation, surface methane monitoring, annual compliance reporting, and transitions between federal and state programs. For a Kentucky landfill operator heading into the state plan transition with questions on NMOC calculation methodology, GCCS operational compliance, or cross-state standardization, the next step is a 30-minute scoping call.