Ships lose oil into the water every day, by design, and so does the machinery of big river dams. The fix, a lubricant that breaks down quickly and is minimally toxic when it escapes, has been in use for more than a decade. The federal rule meant to require it has not been issued. Its deadline is October 9.
At the back of most ocean-going ships, a steel shaft runs out through the hull to the propeller. Where it leaves the ship, it passes through a tube packed with oil, and at the end of the tube a ring of seals presses against the turning shaft. The seals have one job: keep the ocean out. They do it by holding the oil inside at a slightly higher pressure than the water outside, so that if anything gets past them, it is oil going out, not seawater coming in.
So oil goes out. Not in a spill, but a little every day, from a working ship, as intended. By an analysis the Environmental Protection Agency relies on, a stern tube consumes about 2.6 liters of oil a day on average, and up to 20 liters, a little over five gallons, on the thirstiest class of vessel. The agency's summary of where it goes is one sentence long: "any leakage of lubricant oil flows into the sea."
Nobody designing a propeller shaft is trying to pollute. The leak is the price of keeping water out of the bearings, and for more than a decade the engineering answer has been to change what leaks rather than to stop it: fill the tube with an oil that breaks down quickly, is minimally toxic to aquatic life and does not build up in living tissue. Regulators call it an environmentally acceptable lubricant.
On the Columbia River, the Army Corps of Engineers has been putting the same idea into its hydroelectric dams, where grease and oil work in the river.
The lubricant is no longer the hard part. In 2018 the Corps' own researchers found that 21 such greases met performance requirements comparable to the mineral-oil greases in its dams, at a competitive cost, though they urged caution in turbines until each grease had a record there. A laboratory study published this year found one such oil comparable to mineral oil in a ship's stern-tube bearing. What is missing is the rule.
Congress gave the Coast Guard two years from the publication of EPA's ship-discharge standards to write the regulations that enforce them, which makes the deadline Friday, October 9. The Coast Guard's own planning document files the rule under "Long-Term Actions," timetable "To Be Determined." Until it exists, ships answer to a permit written in 2013, which defines "acceptable" but leaves it to owners to show a product qualifies.
I.
One ship's leak is small. The fleet's is not. The figure regulators use comes from a 2010 conference paper by Dagmar Schmidt Etkin, a consultant at Environmental Research Consulting, who estimated the lubricating oil working vessels put into the world's port waters each year, from stern tubes and other routine discharges: 36.9 million to 61 million liters, roughly 10 million to 16 million gallons. EPA repeated the range in its 2024 rule.
In a 2011 report it went further and called the total "the equivalent of about one and a half Exxon Valdez-sized spills."
That comparison deserves its caveats. Etkin's paper says its stern-tube figures rest on "data on oil consumption sourced from a lubricant supplier," and it names no funder. Her firm's publication list includes a related 2009 study "prepared … for Castrol Marine Ltd.," a maker of marine lubricants. The agency has leaned on the figure for fifteen years. Etkin cites an older estimate, presented at the International Maritime Organization in 2008, that is higher still: 80 million liters a year from stern tubes alone.
The first federal requirement came in a permit. EPA's 2008 permit had encouraged these oils; its 2013 Vessel General Permit, which covers commercial vessels of 79 feet and longer in U.S. waters, required them in every oil-to-sea interface unless that was technically infeasible. It was careful not to call them harmless: using one, the permit says, "does not authorize the discharge of any lubricant in a quantity that may be harmful as defined in 40 CFR Part 110," EPA's oil-sheen rule.
In December 2018 Congress replaced the permit system with the Vessel Incidental Discharge Act, and EPA's national standards, published on October 9, 2024, repeat the requirement plainly: "An environmentally acceptable lubricant (EAL) must be used in any oil-to-sea interface unless such use is technically infeasible." Under the law, though, they take effect only when the Coast Guard's regulations do. Until then, the 2013 permit governs.
II.
On the Columbia and the Snake, the oil comes from dams. Each hydroelectric unit has gates, bearings and seals that work in the water, and the Corps runs eight big dams on the lower Columbia and lower Snake. "Every year, hydroelectric dams on the Columbia and Snake rivers leak large quantities of oil," Lauren Goldberg, then legal and program director of Columbia Riverkeeper, an environmental group, told Northwest Public Broadcasting in 2019.
"Sometimes there are leaks of hundreds of gallons of oil, sometimes over a thousand gallons of oil."
The leaks are often hard to see. In October 2022 the Corps confirmed an oil leak in the turbine system of Main Unit 1 at Little Goose Dam on the Snake. There were "indications that between 300 to 600 gallons of oil leaked over the previous 90 days," its release said; the oil was "not recoverable," and no sheen had been seen on the river.
Dylan Peters, a spokesperson for the Corps' Walla Walla District, told Northwest News Network why it took three months to notice: "Because the oil was leaking back through the system into the turbine itself, it wasn't giving us the normal readings that you would look for for a potential oil leak."
At The Dalles, one unit leaked twice. In March 2018 the Corps reported losing about 470 gallons of oil from a generating unit, and said there was no evidence it had reached the river. In June the same unit lost about 53 gallons. In December, 192 gallons of hydraulic turbine oil went into the Columbia below the dam.
Because the oil was leaking back through the system into the turbine itself, it wasn't giving us the normal readings …
— Dylan Peters
Spokesperson, Walla Walla District, U.S. Army Corps of Engineers
The change on the river came from a lawsuit. Columbia Riverkeeper sued the Corps over oil discharges from the dams, and in August 2014 the two sides settled. "This is a groundbreaking agreement for clean water," Brett VandenHeuvel, the group's executive director, said in its announcement. Bob Rees, a fishing guide who then led the Association of Northwest Steelheaders, put the stake in commercial terms: "We rely on toxic-free fish to fuel business in communities along the Columbia and Snake Rivers."
The settlement's lubricant clause was narrower than the announcement suggested. It noted that the Corps already used environmentally acceptable lubricants on some equipment at The Dalles and John Day.
It gave the Corps a year to assess whether it could switch from grease to such lubricants on in-water equipment, "including wicket gates for the hydropower turbines, navigation locks and certain fishway equipment," and it limited that assessment to one question: "whether one or more EALs can be used without risk of potential damage to the equipment." Where the answer was yes, the Corps would switch.
III.
The test was scheduled at McNary Dam, near Umatilla, Oregon, on a turbine called Unit 13. Wicket gates are the adjustable vanes that meter water into a turbine. Their stems turn in greased bushings, and the grease meets the river. For the trial, technicians were to fit transducers to the wicket-gate stems and the grease lines, take the unit out of service and drain it to purge the old grease, and measure the bushings again about a year later, in December 2017.
Because the unit sits in a salmon river, the work had to be coordinated with the fish managers: the Corps' memo cites the previous August's count, 1,278 Chinook passing the dam on a single day, to gauge the outage's effect on fish.
A Corps report on the powerhouse tests, dated March 5, 2018, is listed among the references in a 2020 EPA permit document; we could not find a public copy. What has been published is the work of Victor F. Medina, a research environmental engineer at the Corps' Engineer Research and Development Center, who spent two days in February 2015 at The Dalles, John Day and McNary cataloguing the greases and oils in use.
His field notes, preserved in a slide deck, read like an inspector's list. On the John Day navigation lock, wire ropes on the gate were "heavily lubricated," above the water. At a fish pump, "the lubricant eventually is discharged into the water." Oil was leaking from spillway gate motors, and sorbent pads had been laid to contain it.
The same slides carry a blunter finding. Of 12 greases Medina's team had evaluated by then, two had test data showing they met all three of EPA's criteria, and neither was in use at the eight dams. Greases "termed as environmental friendly, environmentally aware, or even EAL," he wrote, "may not actually have sufficient testing to meet EAL requirements."
That was a preliminary count. The Corps' technical report, published in December 2018 with Medina as lead author, looked at 21 greases and reached a steadier conclusion: they "met performance requirements comparable to the mineral oils currently used in USACE dams," their cost was "competitive," and they "can be readily used." At Bonneville, switching the wicket-gate grease would raise operating costs by something on the order of 0.03 percent.
The report also found "a range of ambiguity" in EPA's definition and put products that "lack some test data" in a second tier. Several greases already in use at Bonneville, The Dalles and John Day sat there.
EPA has since written the requirement into the dams' water permits. The permits for the four Snake River dams require the Corps to "select EALs for all oil to water interfaces including wicket gates, bearings, lubricated wire ropes, Kaplan runners and other in-line equipment, unless technically infeasible," and to report on it to EPA every February. The permits come up for renewal next spring, and the Corps must apply by October 2.
IV.
Ships were harder. After the 2013 permit, shipowners switched in large numbers, and within a few years DNV (then DNV GL), the Norway-based classification society that sets technical rules for ships, was investigating what it called "a surge of stern tube bearing failures since 2014." The switch, it said in 2019, had "coincided with a reported widespread increase" in failures.
Under high load, its engineers found, an environmentally acceptable lubricant "will operate with a lower true viscosity" where the oil film is thinnest, and a much lower one in the cold, during mooring trials or a cold start. DNV changed its shaft-alignment rules that July. Its advice was not to abandon the new oils but to specify them properly: one viscosity grade up, or a better aft bearing.
The damage to confidence outlasted the diagnosis. A 2025 review in the ASME Journal of Tribology, whose authors include DNV researchers, found that the oils "suffer from a loss of trust from ship owners," that only a small fraction of new ships are built with systems that use them, and that owners often prefer other answers to the leak: air-seal systems that keep mineral oil in the tube, or bearings lubricated by seawater, with no oil at all.
This year a laboratory study in Tribology Transactions, by engineers at RWTH Aachen University and Gdańsk University of Technology, ran one such lubricant against mineral oil in a stern-tube bearing. Under normal conditions its friction was 9.4 percent higher and its oil film 7.3 percent thicker. Under severe conditions it did as well or slightly better. "These results show that EALs can be used in stern tube systems under normal and severe operating conditions," the authors concluded.
Read together, the record is not a story about green oil failing. It is a story about a substitution made fast, under a permit, before the rules for designing a ship's bearings accounted for how these oils behave, and then corrected. The engineering question has largely been answered. The regulatory one has not.
V.
EPA's definition has three parts: an environmentally acceptable lubricant must be biodegradable, minimally toxic and not bioaccumulative. Nothing in it says the oil has to come from a plant. The Corps' own guidance lists the base fluids that can qualify: synthetic esters, polyalkylene glycols, polyalphaolefins and crop-based oils. Two of those four, polyalphaolefins and polyalkylene glycols, are typically made from petrochemicals, and synthetic esters can be too.
That matters to a buyer, because the government also runs a program for biobased products, made from agricultural, forestry and other biological materials, and the two are easy to confuse. The Agriculture Department's BioPreferred program sets a minimum biobased content for each category it designates for federal purchasing: on its register as of September 2026, 46 percent for water turbine bearing oils and 44 percent for hydraulic fluids.
That measures where the carbon came from, not what happens when the oil reaches a river. A product can meet the biobased minimum without being an environmentally acceptable lubricant, and one made from polyalphaolefin can be acceptable with no biobased carbon at all. A product can also pass both tests; for water turbine bearing oils on the permitted dams, the purchasing preference and the EAL requirement can apply at once.
The register has no category for stern-tube oil in particular; such a product falls under its catch-all "Other Lubricants," at 39 percent.
The additives are where a label can mislead most. In a 2024 study funded in part by the Energy Department's water-power office, chemists at Oak Ridge National Laboratory mixed candidate additives into a base oil and exposed a small freshwater crustacean used in EPA toxicity tests to the result. With the lab's own experimental additives, 90 to 100 percent of the animals survived. With a conventional additive, 30 percent survived. With the two commercial bio-derived additives the team tested, none did.
"This is a clear example that bio-derived does not mean low toxicity," the authors wrote. (One author worked for Syensqo, the company that supplied part of the lab's feedstock.)
A timeline from EPA's 2011 lubricant report to the Coast Guard's October 9, 2026 deadline and the Snake River dam permits' March 2027 expiry.
| Item | What happened | Ships or dams |
|---|---|---|
| 2011 | EPA report on environmentally acceptable lubricants | Ships |
| Dec 2013 | Vessel General Permit requires EALs in oil-to-sea interfaces | Ships |
| Aug 2014 | Corps and Columbia Riverkeeper settle | Dams |
| Feb 2015 | Corps field survey of dam greases | Dams |
| 2016–17 | McNary Unit 13 grease trial planned | Dams |
| Dec 4, 2018 | Vessel Incidental Discharge Act signed into law | Ships |
VI.
The deadline falls on a Friday. According to its entry in the federal regulatory agenda, the Coast Guard plans to issue the rule as an interim final rule, which would take effect without first being proposed for comment. The agenda gives no date. As of late September nothing was under review at the White House office that clears significant rules before publication, a step this one would have to take.
None of that changes what happens at the back of a ship on the morning of October 10. The shaft will turn, the seals will hold, and the oil in the tube will stay at a slightly higher pressure than the sea, as designed. A few liters of it will go into the water. The only question the rule was ever going to settle is what those few liters are made of.
Patriot BioSolutions, which publishes The Green Brief, sells biobased products, including lubricants.
| Dec 2018 | Corps technical report on dam lubricants | Dams |
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| 2019 | DNV changes shaft-alignment rules | Ships |
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| Apr 2022 | Snake River dam permits require EALs | Dams |
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| Oct 9, 2024 | EPA publishes national standards | Ships |
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| Oct 2, 2026 | Corps must apply to renew Snake River permits | Dams |
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| Oct 9, 2026 | Coast Guard's statutory deadline | Ships |
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| Mar 31, 2027 | Snake River permits' term ends | Dams |
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