When a fuel delivery company showed up to Johns Hopkins Hospital last Wednesday morning with thousands of gallons of diesel for backup generators, it quickly found itself in trouble.

Hospital and public officials still haven’t explained how it happened, but two underground tanks were filled well past their capacity. As a result 5,000 gallons of red-dyed diesel raced down storm drains from the medical complex to the Baltimore waterfront, coating turtles and birds and turning a Harbor East canal the color of wine.

Hopkins has promised to pay for the cleanup, but, beyond acknowledging the overflow, hospital officials have revealed little about how the mess happened.

Was this a mechanical failure? A faulty meter? A contractor asleep at the nozzle?

The Maryland Department of the Environment requires owners of underground tanks, like Hopkins, to ensure deliveries are “constantly monitored” to guard against overfilling. MDE spokesman Dave Abrams said owners must also gauge their tanks’ capacity — either using a stick or automatic reader — and check that tanks have room before accepting new deliveries.

The two Hopkins tanks were outfitted with fail-safes, as required by state regulations, according to a Hopkins registration document provided by MDE.

The rules call for fuel tank operators to use one of two options to prevent overfills: Facilities with underground tanks must have either automatic shut-offs that stop the flow of fuel when a container reaches 95% capacity, or be equipped with alarms — sounding both audible and visible signals — when a tank is 90% full.

The two Hopkins tanks are double-walled and each capable of holding up to 20,000 gallons of fuel, according to their registration with MDE’s Oil Control Program. In service since 2005, both tanks have required overfill fail-safes, according to the state registration.

A Hopkins spokesperson did not answer questions about the circumstances surrounding this spill, including whether fail-safes were in working order or whether hospital system personnel were on site at the time of the incident.

“A thorough review of the diesel fuel overflow incident is ongoing, so we do not yet have full information about precisely what happened and all of the contributing factors,” spokeswoman Kim Hoppe said in a statement.

Hopkins is cooperating with government authorities “to protect the health and safety of the community,” she said.

MDE also requires each tank to have 5-gallon spill buckets, though these would have been far too small to contain to last week’s spill.

Abrams, the MDE spokesman, shared Oil Control Program requirements and said regulators are investigating the cause of the spill. The environmental agency is overseeing cleanup in Harbor East alongside city agencies and the U.S. Coast Guard.

A week since the incident, responders have cleaned up much of the spill, and environmental scientists have said long-term impacts are likely small, since diesel evaporates quickly.

Still, the fuel reached a body of water that environmentalists and government agencies have worked for years in an effort to restore, though it remains challenged by urban runoff and sewer overflows.

Hopkins initially estimated the spill was around 200 gallons before revising that figure to 2,000 gallons and, finally, reporting Friday that it totaled 5,000 gallons. The hospital offered no explanation for why its estimate grew exponentially.

Alice Volpitta, Baltimore harbor waterkeeper for the nonprofit Blue Water Baltimore, said the MDE tank registrations might explain why Johns Hopkins has remained tight-lipped, since the hospital system may believe it has grounds to hold its contractor accountable.

“We should all look at this incident [and] understand that something like this can happen at any time,” she said. “Accidents happen.”

As Volpitta and environmental scientists have pointed out, things could have been worse.

Diesel fuel is lighter than other petroleum products, meaning it can evaporate on its own, but also spreads quickly, said Carys Mitchelmore, an environmental toxicologist with the University of Maryland Center for Environmental Science. In this case, the diesel emptied into a canal beneath Central Avenue that trapped the fuel on three sides, while emergency responders were able to able to contain almost all of it.

If the spill had emptied into the harbor at a different location, it could have spread farther. Diesel is among the most acutely toxic types of oil, Mitchelmore said, and a wider spill could have caused greater harm to wildlife and health hazards to people who inhaled its fumes.

The recent spill isn’t Hopkins’ only problem with pollution.

According to a U.S. Environmental Protection Agency database, a heating and cooling system at the hospital has released pollutants in its wastewater at levels far above federal limits for years, emptying them into storm drains and ultimately the harbor. At points since April 2022, the Hopkins plant has discharged copper at levels 25 times or even 40 times the EPA’s monthly limit. Chlorine discharges have reached as much as eight times the federal limit.

Despite the EPA rap sheet, MDE has no recorded inspections of the issue in its database.

MDE’s Abrams said the Hopkins wastewater discharges were referred to the EPA in 2023. State regulators visited the site alongside the EPA in April 2023, but have not inspected it since, he said.

Hopkins’ Hoppe did not acknowledge questions about the wastewater violations.

The Hopkins discharges flow through storm drains beneath the city, and, according to a state permit, empty into the harbor under Central Avenue, where a bridge connects Harbor East and Harbor Point — the same spot where diesel filled the canal last week.

Volpitta said it’s troubling that an institution so dedicated to Baltimore’s public health has contributed this much pollution to its waterways.

But Volpitta was heartened by the quick emergency response to last week’s spill and the outcry of residents, which she saw as a sign of how much people care about cleaning local waterways.

The incident served as a reminder of the harbor’s vulnerability, she said.

“If this had happened anywhere else along the harbor,” she said, “it would have been a much more devastating impact.”