Here's what the document actually says, and it is a case study in how one number frames an entire rule. On May 18, 2026, the Environmental Protection Agency proposed a Clean Water Act regulation (RIN 2040-AG41, docket EPA-HQ-OW-2009-0819) that would revise the technology-based effluent limitations guidelines and standards — ELGs — it adopted in its 2024 supplemental rule for the steam electric power generating point source category. The proposal targets one discharge stream: unmanaged combustion residual leachate (CRL) at existing power plants. And EPA puts a hard estimate on it — the change is projected to reduce costs by $446 million to $1.09 billion annually at a 3 percent discount rate. The comment period closed June 17, 2026.
Two pieces of vocabulary unlock this. 'Effluent limitations guidelines and standards' are the technology-based limits the Clean Water Act requires EPA to set for categories of industrial dischargers; they define how clean a wastewater stream has to be before it leaves the facility, based on what treatment technology can achieve. The 'steam electric power generating point source category' is regulatory shorthand for power plants that boil water to spin turbines — historically the coal fleet, where most of the relevant discharges originate. The 2024 rule tightened these limits; this 2026 proposal would revise them back for one stream.
What combustion residual leachate is — and why it's the target
Combustion residual leachate is the water that percolates through coal-combustion residuals — coal ash — and picks up contaminants as it moves. 'Unmanaged' CRL, the specific stream this proposal addresses, is leachate that is not actively collected and routed through engineered treatment. The 2024 supplemental ELG imposed requirements on this stream at existing sources; the 2026 proposal would revise those requirements, and the headline consequence is the cost figure EPA itself published: up to $1.09 billion a year in reduced costs to the regulated power plants.
That number is the story, and it deserves to be read in both directions. A cost saving to industry of that size is, by definition, the avoided cost of controls that the 2024 rule would have required. The document does not present those controls as worthless — it presents the proposal as a revision of the technology basis for regulating this particular stream. But the honest framing is a trade-off: EPA is proposing to require less treatment of an ash-derived discharge stream, and the benefit it quantifies most prominently is the money power plants won't have to spend. The pollution-reduction side of the ledger is what the comment record will contest.
The legal and policy machinery
The reason EPA can propose this at all is the structure of the Clean Water Act's ELG program. The limits are 'technology-based,' meaning EPA sets them according to what a defined level of treatment technology can achieve and what is economically achievable for the category. That gives the agency room to revisit the technology basis — to conclude that a different level of control is the appropriate standard for unmanaged CRL at existing sources than the 2024 rule prescribed. A revision like this is EPA re-drawing the technology line, and the cost estimate is part of how it justifies the new line as economically reasonable.
This is also a textbook example of a regulatory whipsaw, and the document, not the press release, makes the sequence visible. The 2024 supplemental rule tightened the standard. The 2026 proposal would loosen it for this stream, roughly two years later. For the power plants in the category, that is precisely the kind of regulatory instability that makes capital planning hard: a plant that began engineering CRL controls to meet the 2024 standard now faces a proposal that may relieve part of that obligation. Some operators will welcome the relief; others, having already committed capital, get less benefit from a rollback than the headline number implies. The savings estimate is an aggregate; it is not evenly distributed.
Why the timing window was tight
One detail worth flagging: the comment period closed June 17, 2026, only about a month after the May 18 proposal. That is a relatively compressed window for a rule of this consequence, and the comment record assembled in that window is what EPA must respond to before it can finalize anything. For a proposal that revises a recent rule and carries a billion-dollar cost figure, the comments — from utilities, environmental organizations, states, and downstream water users — are the substance of the next phase. A proposed rule is a proposal; it sets no binding limit until EPA finalizes it after weighing those comments.
What to watch
Three things will determine whether this proposal becomes the rollback the headline number suggests. First, whether EPA's technology and economic justification for revising the unmanaged-CRL standard holds up against the comment record — the cost saving is the agency's number, and the comments will test the pollution-control assumptions behind it. Second, the scope: this proposal is specifically about unmanaged CRL at existing sources, not the entire 2024 ELG, and reading it as a wholesale repeal of power-plant wastewater limits would be wrong. Third, the litigation posture — rules that loosen Clean Water Act standards and carry large cost figures tend to be challenged, and a final rule is rarely the end of the story.
The verifiable bottom line: EPA has proposed to revise the 2024 effluent guidelines for unmanaged combustion residual leachate at existing power plants, under RIN 2040-AG41, and estimates the change cuts costs by $446 million to $1.09 billion a year. That figure is EPA's own, and it is the lens through which the entire proposal should be read — a quantified cost saving on one side, fewer controls on an ash-derived discharge stream on the other. The final rule, after the comments, is where the line actually gets drawn.