Two chemical leaks at South Carolina solar factory reignite fight over siting near schools

The yellow buses were already rolling toward Flint Hill Elementary School the morning of March 5 when district officials got word there had been another chemical incident at the solar-panel factory next door.

Within minutes, the Fort Mill School District told drivers to divert students to a different campus for pickup. Families’ phones lit up with alerts: Flint Hill would be closed “out of an abundance of caution” because of “an active incident at Silfab Solar.” Emergency vehicles clustered at the sprawling white-and-glass plant just beyond the school’s ball fields.

It was the second leak in three days at the state-backed facility, which South Carolina leaders had only recently promoted as a flagship of the nation’s clean-energy manufacturing push.

No hazardous chemicals were detected on school grounds in either case, according to state regulators and the district’s independent air monitors. But the dual incidents in early March set off a far-reaching dispute over what kinds of industrial operations belong next to schools — and how much risk communities should accept in the name of green jobs.

A state-backed plant, a neighborhood school

Silfab Solar, a Canada-based manufacturer with plants in Washington state and Ontario, chose Fort Mill in 2023 for a $150 million facility to make solar cells and assemble panels. The 785,000-square-foot plant sits on Logistics Lane in York County’s Lakemont Business Park, directly beside Flint Hill Elementary and the site of a planned middle school.

State and local economic development officials hailed the project, which promised about 800 jobs and a major foothold for domestic solar-cell production. Gov. Henry McMaster called it “another chapter in South Carolina’s clean-energy success story” when the deal was announced.

From the start, however, residents and school families questioned whether a chemical-intensive factory should operate a few hundred yards from classrooms.

Two incidents in 72 hours

On March 3, those fears moved from hearing rooms to the morning commute.

Around 9:45 that morning, York County emergency officials received a report of a chemical release at Silfab. Initial alerts cited a 1,530-gallon spill of potassium hydroxide solution into a retention pond on the property. County officials later said that estimate was based on the capacity of a tank and that no more than 300 gallons of a very dilute solution — about 0.03% potassium hydroxide in water — actually escaped.

In a statement that day, Silfab said it could “confirm the accidental release of no more than 300 gallons of water diluted to a level of 0.03% potassium hydroxide” at its Fort Mill plant. The company said the material “was fully contained on site” and quoted the York County Office of Emergency Management as finding “no threat to public safety.”

Potassium hydroxide is a strong caustic chemical that can cause burns at higher concentrations, but regulators said the diluted solution posed no off-site risk. Hazardous materials crews responded, and the county told the public there was no impact to drinking water or nearby schools.

The Fort Mill School District said in a March 4 statement that it was “relieved this specific event did not pose an immediate risk to the community” and noted that its air monitors at Flint Hill registered no abnormal contaminants. At the same time, the district said it would review “the actions of both our staff and partnering entities to identify and address areas where improvements should be made.”

Two days later, another alarm went out.

Shortly after classes began on March 5, York County notified the district of a second incident at Silfab, this one involving hydrofluoric acid (HF), a highly corrosive substance used to etch and clean silicon wafers in solar-cell production. The company is permitted to store thousands of gallons of HF solution on site.

State and county officials later said about 300 gallons of HF solution leaked within a secondary containment structure designed to catch spills and did not leave the plant’s footprint. As with the earlier incident, regulators reported no off-site contamination.

But with HF, officials and parents alike were dealing with a chemical known for worst-case scenarios. Significant exposure can cause deep tissue damage and serious systemic effects. A community-funded modeling study by University of South Carolina researchers had previously suggested that a catastrophic HF release at the Silfab site could affect people over a multi-mile radius, depending on conditions.

School closure and state orders

The school district moved quickly. In a message to families that morning, officials said county emergency management had indicated “no danger to the community or our school” but added, “Out of an abundance of caution Flint Hill Elementary will be closed today.” Students already on buses were rerouted to Pleasant Knoll Middle School for dismissal. The district later said Flint Hill would remain closed Friday, March 6, while investigations continued, and classes would resume Monday.

At the state level, environmental and legal authorities escalated their response.

The South Carolina Department of Environmental Services — the newly structured agency that regulates air and water permits — had already directed Silfab on March 3 to suspend some operations while it investigated the potassium hydroxide release. After the hydrofluoric acid leak on March 5, the agency issued a follow-up letter ordering the company to cease operations at the Fort Mill plant.

Attorney General Alan Wilson went a step further publicly. In a statement and social media posts that Thursday, he called on Silfab to “immediately shut down” pending further review. Wilson later said his office had spoken with company representatives and that Silfab had agreed to “cease all chemical operations pending investigations and stop all other operations until Monday at 7 p.m., when the EPA is on the ground.”

“I know it’s been a long week for you,” Wilson told Fort Mill parents in a video message that evening.

Over the weekend, state officials arranged for roughly 300,000 gallons of water to be pumped from Silfab’s on-site stormwater pond and hauled to a permitted treatment facility as a precaution after the earlier potassium hydroxide spill. Silfab issued several public notices saying it was cooperating with state and federal investigators and underscoring that emergency officials had found “no offsite impact” to people or the environment.

On March 9, teams from the U.S. Environmental Protection Agency and the state environmental agency conducted on-site reviews at the Fort Mill plant. That night, regulators said Silfab could restart assembly operations — the portion of the plant that strings together cells into panels and laminates them — but that higher-risk chemical manufacturing would remain paused while the investigation continued.

Flint Hill Elementary reopened the same day.

A zoning fight and calls for new rules

By then, the accidents had crystallized a yearslong local dispute over how Silfab ended up next to two schools in the first place.

Silfab announced its Fort Mill project in September 2023, saying the plant would produce next-generation solar cells and modules for the U.S. market. York County leaders, in partnership with the state, had recruited the company to Lakemont Business Park, a light-industrial zone off Carowinds Boulevard where nearby subdivisions and new schools have sprung up as the Charlotte area has grown.

Residents organized quickly, arguing that a facility storing large amounts of hydrofluoric and hydrochloric acids and pyrophoric silane gas did not belong within about 600 to 1,300 feet of schools and homes. At a state air-permit hearing in October 2023, parents and neighbors pressed regulators about worst-case release scenarios and emergency plans for Flint Hill.

In February 2024, a Fort Mill resident formally asked York County to determine whether Silfab’s proposed operations qualified as “light industrial.” Three months later, the county Board of Zoning Appeals voted 5-0 that the type of solar-cell manufacturing Silfab planned was “heavy industrial” — a use not allowed in that zoning district.

County attorneys later said the board’s interpretation applied prospectively to new projects and did not automatically revoke Silfab’s previously issued approvals. A citizens’ group sued the county, Silfab and the property owner over building and air permits, but a judge dismissed the case in early 2026, clearing the way for operations to move forward under existing permits.

Monitoring, oversight and what comes next

The Fort Mill School District, which does not control industrial siting, tried to prepare for the plant’s opening. It hired environmental consultants Citadel EHS in 2024 to design an air-quality sampling program and emergency procedures tailored to Silfab. Perimeter monitors at Flint Hill went online around January, measuring dust, volatile organic compounds and wind conditions. Those instruments detected no contaminants during either March incident, the district has said.

Still, the twin leaks within 72 hours prompted the school board to take an unusually direct stance.

At a meeting in the days after the plant was ordered to shut down, the Fort Mill School Board adopted a resolution expressing “grave concern” about the two incidents and calling on state and local leaders to change what the Silfab site is allowed to do.

The board urged the governor, attorney general, state environmental agency, York County Council and county planning commission to limit Silfab’s operations to assembly work only and “require the immediate and permanent removal of hazardous chemicals from the Silfab site” because of the schools’ proximity.

“The district does not have direct legal authority over industrial siting or permitting,” the resolution noted, but board members said they were compelled to advocate for the safety of students and staff.

Local legislators, including state Sens. Mike Johnson and Wes Climer and several House members from York County, have also called for Silfab’s operations to remain restricted until regulators and independent experts can verify safety systems at the site. Some have said they will pursue legislation setting minimum distances between certain types of chemical facilities and K-12 schools statewide.

Silfab has said little publicly beyond its incident updates and statements committing to “continuing safe operations at Fort Mill for its employees and the community” and welcoming additional reviews by state and federal agencies. The company has emphasized that both incidents were immediately reported, that emergency systems functioned as designed and that government agencies have consistently found no off-site impacts.

As of mid-March, the Fort Mill facility is running only its assembly lines with heightened oversight, while tanks and systems tied to full solar-cell production remain idle. State environmental officials say their investigation into the March spills is ongoing and that they will evaluate whether any changes to Silfab’s permits or operations are warranted.

For parents dropping children at Flint Hill Elementary, the tall white factory at the edge of the campus is still part of the morning view. The buses are back to their usual routes, and the air monitors along the school’s fence line quietly log data. Whether the chemicals that were supposed to power South Carolina’s solar ambitions will ever resume flowing next door is now a question for regulators, elected officials and a community that has already lived through two early scares.