Clean Harbors' Co-CEO Sold $800,000 at a Record High. The Sale Isn't the Warning — the Price Is.

When Clean Harbors co-CEO Eric W. Gerstenberg sold 2,500 shares in mid-August, the instant read was the familiar one: the insider is bailing. The math does not support that read. The trade was worth $803,350, executed at $321.34 — a price within a handful of dollars of the company's record. It was about 4% of the stake he held, and afterward he still owned roughly $18.25 million of Clean Harbors. It was, in fact, his second identical 2,500-share sale of the year, made back in February at a lower price.

That combination — a small, repeated, scheduled-looking trim at the top of a run — is the signature of an executive managing a concentrated position, not a man losing faith in his own company. The sale is real, but it is not the story. The question that actually moves your money has nothing to do with the CEO's personal checkbook. It is whether a cash-flow business that just posted a record quarter and raised its guidance is worth the price the market is now charging for it.

The sale, stripped of the drama

Insider sales get treated like a smoke detector — any smoke means fire. But people sell stock for ordinary reasons: taxes, diversification, a plan they set up months earlier. The mere fact that someone sold tells you almost nothing. What carries weight is the size, the price, and the surrounding context.

Here, all three point the other way. The size is small — about 4% of his holding, under $820,000. The price is high, near the 52-week high of $335.94 on a stock that has risen roughly 36% year to date from a low of $201.34. And the context is that Clean Harbors has been outperforming its own sector: over the past six months the shares gained about 16% while the industry group fell about 5%. Selling a little of a winner near all-time highs, twice, in the same clean block size, looks like routine trimming at a favorable price. If anything, the timing argues the opposite of panic — he was cashing in, not escaping.

The cash flow the sale is being measured against

To know whether the stock is worth worrying about, you have to look at what the company does and whether the money is durable. Clean Harbors is one of the largest hazardous-waste treatment and environmental-services operators in North America. Its core business — collecting, treating, and disposing of industrial and hazardous waste — is largely fee-based: customers pay for a service, and the demand is among the stickiest in the economy, because industry and construction keep generating waste whether or not the market is in a boom. That fee-based, predictable character is exactly the kind of cash flow that justifies a premium over commodity-linked names.

The second quarter of 2026 shows that durability in motion. Revenue rose 12% to a record $1.74 billion; net income jumped 34% to $170.5 million; and adjusted EBITDA grew 22% to $409 million, with the margin expanding 190 basis points to 23.6%. The environmental-services segment delivered its 17th consecutive quarter of year-over-year margin expansion, incinerator utilization climbed to 91% from 86%, and landfill volumes rose 7%. Earnings of $3.22 a share beat the roughly $2.81 the street had penciled in. On top of a strong quarter, management raised full-year 2026 guidance — lifting the midpoint for adjusted EBITDA to about $1.38 billion and adjusted free cash flow to about $550 million.

If you were worried the co-CEO was fleeing a weakening business, the underlying data says the opposite. The cash flow is growing, the margins are still expanding, and the company is pointing up, not down.

Where the price leaves you

Now the part the insider sale does not touch: what the stock is being asked to cost you. On the last twelve months of earnings, Clean Harbors trades at roughly 38 times, and on the coming year's estimate around 45 times. That is well above the waste-management majors — Waste Management and Republic Services both sit near 31 times trailing earnings — even though, on the cash-flow multiple (EV/EBITDA) of about 16, Clean Harbors is roughly in line with them rather than wildly ahead.

That gap matters. A business that just raised guidance and is still expanding margins can afford a richer multiple — fee-based durability earns a premium. But rich is not cheap, and there is no margin of safety hiding in a 45-times-forward stock sitting near its all-time high after a 36% year-to-date run. Free cash flow over the last twelve months works out to a little under 3% of the market value; even the raised 2026 guidance only nudges that higher. You are paying up for a genuinely excellent, defensible cash-flow machine, and in return the cash coming back to you is thin.

That is the honest read, and it is a different call from "insider sold, run." Clean Harbors is a durable, fee-based compounder with 17 straight quarters of margin expansion and a full-year guide pointing up. It is not, right now, at a price where the gap between what the business earns and what you pay leaves much room for error. If the run that took it from the low $200s to the $320s continues, the multiple has less slack to absorb any wobble in growth.

The gap the stock needs to give back

The sale is a distraction — keep it off the list of reasons. The reason to be patient is the price. Clean Harbors only becomes the kind of opportunity a cash-flow investor wants when the gap between its durable earnings and its share price re-opens: either the stock pulls back, or its growth has to prove out of a far richer multiple. The quarterly earnings and, especially, the adjusted free-cash-flow number are the whole bull case, the only thing that keeps justifying the premium — and so the number that should be holding you back is not the co-CEO's $800,000 sell, but a price that has already priced in the good quarter.