Twenty years of maintenance after attainment — split into two ten-year plans, and shared where an area crosses a state line
The Environmental Protection Agency proposed approving a limited maintenance plan submitted by Kentucky for the Louisville area. The maintenance period runs twenty years in two ten-year halves, and this covers the second. The area crosses a state line, so each state submits its own portion.
Document overview (primary data)
- Document typeProposed rule
- AgencyEnvironmental Protection Agency
- Citation91 FR 55294
Key points
- The Environmental Protection Agency proposed approving a limited maintenance plan from Kentucky for the Louisville area.
- The maintenance period runs twenty years in two ten-year halves, and this plan covers the second.
- The subject is the 1997 8-hour ozone standard, whose maintenance remains at issue in 2026.
- The area spans Kentucky and Indiana, with each state submitting the plan for its own portion.
- The effect of approval is to make maintenance commitments federally enforceable as part of the state plan.
1What follows attainment
Meeting the standard and being redesignated to attainment does not end the procedure. A maintenance period follows — a long one, structured as two ten-year plans.
This is the later half. Roughly a decade has passed since attainment, and a plan for the next ten years is under review. This site separately covers a redesignation, where a maintenance plan was approved; here that plan is being renewed period by period.
2Older standards persist
The subject is the 1997 8-hour ozone standard. In a 2026 document, maintenance of a standard nearly thirty years old is at issue. Standards are revised without the old ones simply vanishing, and an area holds a separate position under each. This site also covers an area classified differently under the 2008 and 2015 standards.
3An area across a state line
| Item | Content |
|---|---|
| The area | The Louisville area spanning Kentucky and Indiana |
| What this covers | The Kentucky portion — Bullitt, Jefferson and Oldham counties |
| Submitted by | Kentucky, through its cabinet, on behalf of the Louisville metro district |
| The remainder | The Indiana portion is handled separately by that state |
Air quality areas are not cut along administrative lines. Where a metropolitan area crosses a state border, so does the maintenance area, and each state submits the plan for its own side. One area is thus covered by two states plans in combination.
4What limited means
A limited maintenance plan is a simplified form of maintenance plan. Where measured values run comfortably below the standard, maintenance may be shown without detailed future projections. Areas with less margin must file a full maintenance plan. What is required varies with the situation of the area.
5The effect of approval
The effect is to make certain maintenance commitments federally enforceable as part of the state plan. Filing a plan is not the point; the point is that the commitments in it become enforceable.
Why it matters
Attainment is not the end point; a twenty-year maintenance stage follows. Where a metropolitan area crosses a state line, plans from several states combine, so which authority applies depends on location.
FAQ
Is a plan needed after attainment?
What makes a maintenance plan limited?
Sources (primary)
Source: Federal Register (federal documents, public domain). Links go to the official site.