Silfab Solar Chemical Spill Next to Flint Hill Elementary: What Happened and Where It Stands (August 2026)

What happened Chemicals on the list Hydrofluoric acid Emergency calls The zoning fight Where it stands now Sources

Last updated August 26, 2026. Originally published April 5, 2026.

Silfab Solar operates a solar cell and panel plant in a converted warehouse in Fort Mill, South Carolina, a few miles south of the North Carolina line. The building sits a few hundred yards from Flint Hill Elementary School, which opened in August 2025, and next to Flint Hill Middle School, which opened this month. In March 2026 the plant had two chemical incidents in one week, and one of them closed the elementary school for two days. Five months later the plant is idle with part of its workforce furloughed, and a circuit court judge is reconsidering a July ruling that found the county never had grounds to permit solar manufacturing at the site.

Key takeaways

• Silfab Solar's plant at 7149 Logistics Lane in Fort Mill shares a property line with Flint Hill Elementary and Flint Hill Middle. Two chemical incidents happened there in March 2026.
• On March 3, potassium hydroxide solution reached a stormwater pond. York County first reported 1,530 gallons, then revised it. Silfab and state regulators describe about 300 gallons of water at 0.03 percent potassium hydroxide.
• On March 5, the county learned of a hydrofluoric acid drip at a storage tank connection that had been present since late February. The school closed for two days. School air monitoring registered nothing and no injuries were reported.
• Since March 16 the plant has been limited to panel assembly under a state compliance agreement. York County says no work with regulated chemicals has taken place.
• On July 21, 2026 a circuit court judge upheld the 2024 zoning board ruling that solar manufacturing is not permitted at the site. A reconsideration hearing was set for August 26, 2026.
• Silfab idled production August 5 and furloughed part of its workforce August 17, citing material supply. The hazardous materials exhibit for the site lists planned storage of 15,850 gallons of hydrofluoric acid.

This article is educational and is not medical or legal advice. The chemistry described here is general toxicology, not a claim that anyone at Flint Hill Elementary was exposed. Where the public record is disputed, both versions are given with their sources.

I published the first version of this article in April, working mostly from one local outlet's reporting. This version pulls from the state compliance agreement, county statements, court filings, and several regional newsrooms, and it corrects two figures I got wrong the first time.

What happened at Silfab Solar in March 2026?

Evidence: strong. Reported by four regional newsrooms and described in the March 16 SCDES compliance agreement. The release volume is disputed, and both figures are given below.

The first incident was on the morning of March 3. Silfab notified York County emergency management that potassium hydroxide had been released at the plant and had reached a stormwater retention pond near the school's fence line.¹ Hazmat crews responded. The Fort Mill School District said the school's air monitoring system did not register any contaminants on campus.¹

The size of the release has been reported two ways. York County emergency management initially said 1,530 gallons, with about 1,500 gallons held in the retention pool and the remaining 30 gallons handled by hazmat crews.¹ The county later reduced that number.² Silfab's director of operations, Greg Basden, said the release was about 300 gallons of water containing 0.03 percent potassium hydroxide, and that the company did not know the volume until an investigation started.³ The compliance agreement Silfab signed with the South Carolina Department of Environmental Services on March 16 describes scrubber water containing diluted potassium hydroxide flowing into a stormwater structure after a manually controlled valve was left open and the solution leaked through a cracked drainpipe.⁴

The cleanup was far larger than either figure suggests. Silfab drained the retention pond, and about 300,000 gallons of water were pumped out and sent to a recycling facility.⁵ The company also removed a layer of soil from the pond as a precaution and said no liquid from the leak was detected beyond its property.⁵

The second incident came to light on March 5. That morning parents were turned away from Flint Hill Elementary because of an active incident at the plant. Students already on buses were taken to Pleasant Knoll Middle School for pickup, and the school stayed closed on Friday March 6.⁶ The chemical involved was hydrofluoric acid. According to Silfab and county officials, the acid was contained in a secondary vessel before it could spread.⁷

Basden gave more detail at a press conference the next day. A shipment of hydrofluoric acid had been offloaded during the week of February 23, and a small drip was found at the base of the tank. A vendor recommended tightening the flange, which brought the leak down to about one drip per hour. Basden said the total was roughly three tablespoons and was far below the amount that requires reporting to state or federal agencies.³ State Representative David Martin, who represents the area, said he did not trust what the company was saying and that Silfab had numerous opportunities to tell the truth.³

The Department of Environmental Services ordered a total stop at the plant on March 5, including a halt on receiving new chemicals. The agency and an EPA official inspected the site on March 9 and cleared Silfab to restart panel and cell assembly that evening, on the basis that assembly does not use chemicals regulated under EPA's Risk Management Program.⁵ The school reopened the same day.⁸ On March 10 the Fort Mill School Board passed a resolution asking the governor, the legislature, the attorney general, and York County Council to permanently limit the site to non-hazardous assembly and remove hazardous chemicals from the property.⁹ No injuries were reported from either incident.¹⁰

What chemicals are listed for the Silfab plant?

Evidence: moderate. Planned quantities come from a hazardous materials exhibit obtained by one outlet through public records. The state air permit confirms the hydrofluoric and hydrochloric acid tanks in the approved design.

The plant's hazardous materials exhibit, obtained through public records requests and published by Charlotte Stories, lists the chemicals Silfab planned to store and use once solar cell manufacturing was running.⁹ These are planned quantities, not a count of what is in the building today. York County has stated that manufacturing never commenced at the site and that no work using regulated chemicals is taking place.¹¹ The state's air permit for the site does describe two hydrofluoric acid storage tanks and two hydrochloric acid storage tanks in the approved process design.¹²

Chemical	Planned quantity listed	Main hazard
Hydrofluoric acid, semiconductor grade	15,850 gallons	Corrosive, penetrates skin, systemic fluoride poisoning
Hydrochloric acid, semiconductor grade	10,560 gallons	Corrosive, toxic fumes
Silane	26,456 pounds	Ignites on contact with air, explosive
Anhydrous ammonia	44,000 pounds	Toxic and corrosive by inhalation
Sulfuric acid	9,198 pounds	Corrosive oxidizer
Phosphorus oxychloride	1,945 pounds	Toxic, releases hydrochloric acid fumes with moisture
Boron trichloride	1,540 pounds	Toxic gas, forms hydrochloric acid with moisture
Trimethylaluminum	951 pounds	Ignites in air, reacts violently with water
Potassium hydroxide	45 percent and dilute solutions	Strong caustic base
Hydrogen peroxide	30 percent or higher	Strong oxidizer
Sodium hydroxide	Not specified	Strong caustic base
Nitrous oxide	Not specified	Oxidizer gas
Methane, high purity	Not specified	Flammable gas
Isopropyl alcohol	Indoor tank	Flammable solvent
Oxygen and nitrogen	Outdoor bunker tanks	Oxidizer, asphyxiant
Ferric chloride, urea	Not specified	Water treatment and exhaust scrubbing

The exhibit also notes that phosphine, carbon dioxide, and hydrogen were under discussion depending on process selection.⁹ The silane is listed as stored in an outdoor bunker with concrete walls on three sides, and the oxygen and nitrogen tanks are required to sit at least 20 meters from the building.

Why does hydrofluoric acid worry people more than other acids?

Evidence: strong. Established clinical toxicology from peer-reviewed reviews. No claim is made here about exposure at the school.

Hydrofluoric acid injures the body through two separate mechanisms. The hydrogen ion burns tissue on contact, as any strong acid does, while the fluoride ion passes through skin and deeper tissue, binds calcium and magnesium, and can pull blood levels of both low enough to disturb heart rhythm.¹³ Deaths have been reported from skin burns covering a small fraction of the body, and symptoms can be delayed for hours, which is why HF burns are treated with calcium gluconate rather than water alone.¹⁴ Inhaled HF vapor injures the lining of the lungs and is absorbed quickly enough to cause the same electrolyte disturbances.¹³

That toxicology explains why the community reaction to a one-drip-per-hour leak was so strong. Residents were reacting to the plan to store 15,850 gallons of the same acid next to two schools, which they had been objecting to since 2024, rather than to the size of the March 5 leak itself.

What about the emergency calls from inside the plant?

Evidence: weak for any link to chemicals. The dispatch records are public. The county reviewed them and found no indication chemicals were involved.

Dispatch records obtained by Charlotte Stories show a series of 911 calls from the Silfab address in early 2026: a worker with seizures on February 4, a 23-year-old man with trouble breathing on March 26, a 25-year-old woman vomiting blood on March 28, and other calls for chest pain and cardiac symptoms.⁹

The first version of this article put those calls under a heading that said workers were getting sick from the chemicals. The calls stay in this version because they are public records, and the claim about cause comes out because nothing in the record supports it. York County reviewed the calls and said there was no indication they involved hazardous chemicals at the facility, and that nearly all of them stemmed from individual medical situations of employees.¹¹ Charlotte Stories also asserted that the calls came at a rate unmatched by other solar plants in the country, but it published no comparison data, and I have not found any. A former employee has alleged safety hazards and wrongful termination in a local TV interview, and no agency has confirmed those claims.¹⁵

How did a chemical plant get approved next to a school?

Evidence: strong for the ruling and the timeline, which come from court records and county statements. The back-dating and agenda claims are allegations from one outlet.

South Carolina recruited Silfab in 2023 with a $2 million state grant, and York County Council approved a fee-in-lieu-of-tax agreement that September on a 4 to 3 vote.¹¹ In February 2024 the county zoning administrator concluded that solar panel manufacturing fit the category for computer and electronic products, which is allowed in the Light Industrial district where the warehouse sits.¹⁶ A neighboring property owner, Walter Buchanan, appealed. On May 9, 2024 the Board of Zoning Appeals voted 5 to 0 that solar panel manufacturing is not a permitted use in the Light Industrial district.¹⁶

The county's position, then and now, is that a zoning interpretation applies to future permit applications and does not cancel approvals issued before the ruling, and that only a court can decide whether the ruling reaches Silfab retroactively.¹¹ Construction continued on that basis, and the county issued Silfab a certificate of occupancy on February 13, 2026.¹¹

Charlotte Stories has published internal county emails it obtained through records requests and argues they show staff back-dated approval dates on civil plans and issued permits for chemical storage buildings, a wastewater plant, and a central energy plant after the zoning board ruling. The same outlet reports that two council members twice asked for the Silfab matter to be placed on a council agenda and were ignored, which it says violates a county code provision requiring deferred items to be scheduled at the request of two members.⁹ Those are the outlet's readings of the records. I have not seen the county respond to the back-dating claim specifically, and it should be treated as an allegation until a court or an audit says otherwise.

Silfab appealed the zoning board's decision. The appeal was heard on May 26, 2026, and on July 21 Circuit Court Judge William McKinnon affirmed the board's ruling in all respects, finding that solar panel manufacturing is prohibited in the Light Industrial district.¹⁷ Silfab's president, Paolo Maccario, wrote to County Council on July 29 saying the decision involved a zoning interpretation only and does not affect the company's current operations.¹⁸ Silfab has said it will appeal. A separate lawsuit by the Citizens Alliance for Government Integrity over whether the ruling applies to Silfab's existing site was stayed pending the appeal, and the group has also petitioned the U.S. Supreme Court on the zoning question.¹⁹

Where does the Silfab plant stand now?

Evidence: strong. County statements, company statements, and court scheduling as of August 26, 2026.

As of this update, the plant is not making solar cells. Under the March 16 compliance agreement, Silfab may not restart the manufacturing steps that use potassium hydroxide and hydrofluoric acid until it retains a qualified engineer, reports to the state, and notifies the state of any future leaks.⁸ York County says only assembly work has been done at the site since then.¹¹ On July 30, after a four-hour closed session, Council Chairwoman Christi Cox announced that the court would hear Silfab's motion for reconsideration on August 26 and that no manufacturing would happen at the plant until then.²⁰

Silfab idled its module and cell lines from August 5 through August 10, citing constraints on materials and components, and on August 17 it furloughed a portion of its workforce for the same stated reason, with an expected three to four week duration.²¹ The Fort Mill School District said the idle was not an issue for the first day of school on August 3.²²

On the legal side, the Citizens Alliance asked the court on August 20 to bar Silfab from any chemical manufacturing process at the site while allowing office, warehousing, and distribution work to continue. The judge will not take up that request at the August 26 hearing.⁴ Two state bills, Senate Bill 530 and House Bill 4293, would void related permits when a property's use is not permitted under its zoning. Both are still in committee.¹⁵ Attorney General Alan Wilson sent Silfab a list of safety questions in March and has since hired an outside zoning consultant to work on the case.²³

The reconsideration hearing was scheduled for 11 a.m. on August 26, 2026 at the Moss Justice Center in York. I will update this section when the ruling is reported.

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Why I am still covering this

Evidence: commentary. This section is my own view of the record above.

Most of the exposures I write about on this site can be managed at home by changing what you buy or filter. A chemical plant next to a public school is not that kind of exposure, because the people affected had no purchase decision to make. What they had was a zoning board that ruled in their favor in May 2024 and a county that treated the ruling as forward-looking only. A circuit court has now sided with the board, and the March incidents are the reason that disagreement is finally being resolved in public rather than in closed session.

If you live in Fort Mill, Tega Cay, or south Charlotte, the York County statement page and the Fort Mill Sun have been the two most consistent places to follow filings and hearing dates. Council meetings are open to the public, and the compliance agreement and the court order are both linked in the sources below.

Sources

• 1. WBTV, "Chemical spill reported at solar facility near elementary school in York County," March 3, 2026. wbtv.com
• 2. WBTV, "Water pumped out of pond at Silfab Solar amid chemical leak," March 5, 2026. wbtv.com
• 3. WCNC Charlotte, "'We followed protocols': Silfab tries to downplay impact of chemical incidents that sparked outrage," March 6, 2026. wcnc.com
• 4. Fort Mill Sun, "Citizens Alliance Asks Judge to Halt Chemical Work at Silfab Plant," August 20, 2026, including the March 16, 2026 SCDES compliance agreement filed as an exhibit. fortmillsun.com
• 5. Solar Power World, "Silfab solar cell manufacturing site temporarily closed after chemical incident," March 11, 2026. solarpowerworldonline.com
• 6. WCNC Charlotte, "South Carolina officials issue 'total stop' for Silfab Solar after second chemical spill this week," March 5, 2026. wcnc.com
• 7. WFAE, "Silfab Solar's South Carolina plant spills another chemical at its Fort Mill site, closing nearby school," March 5, 2026. wfae.org
• 8. WCNC Charlotte, "Silfab to return after two chemical incidents at plant near Fort Mill school," March 7, 2026. wcnc.com
• 9. Charlotte Stories, "Christi Cox and Josh Edwards Ignored The Law To Force Silfab's Toxic Factory Next To Kids," April 3, 2026, and "Why Do So Many People Keep Getting Sick and Injured At Fort Mill's Silfab Factory?", March 26, 2026. Advocacy outlet, used here for records it obtained through public records requests: the hazardous materials exhibit, dispatch logs, school board resolution, and internal emails. charlottestories.com
• 10. Post and Courier, "Silfab Solar will return to court in August to argue against York County zoning ruling," July 2026. postandcourier.com
• 11. York County, SC, "Information on Silfab Solar," official statement page, updated through August 2026. yorkcountysc.gov
• 12. South Carolina Department of Environmental Services, Silfab Solar community engagement page, air permit process description. des.sc.gov
• 13. Schwerin DL, Hatcher JD. "Hydrofluoric Acid Toxicity." StatPearls, updated 2023. PMID 28722859. pubmed.ncbi.nlm.nih.gov
• 14. Bajraktarova-Valjakova E, et al. "Hydrofluoric Acid: Burns and Systemic Toxicity, Protective Measures, Immediate and Hospital Medical Treatment." Open Access Maced J Med Sci. 2018;6(11):2257-2269. PMC6290397.
• 15. WSOC-TV, "Judge to hear Silfab Solar in zoning appeal case," May 2026, including the former employee interview and pending bills S.530 and H.4293. via yahoo.com
• 16. WBTV, "Judge upholds 2024 York County zoning ruling in Silfab Solar dispute: What to know," July 27, 2026. wbtv.com
• 17. FITSNews, "S.C. Court Upholds Ruling Against Silfab Solar's Fort Mill Factory," July 21, 2026, with a link to the order. fitsnews.com
• 18. Fort Mill Sun, "Silfab Tells York County Council Court Ruling Does Not Affect Fort Mill Operations," July 30, 2026. fortmillsun.com
• 19. The Herald (Rock Hill), "SC judge affirms York County zoning ruling; Silfab to appeal, plant still open," July 22, 2026. via aol.com
• 20. WBTV, "York County Council waiting on further developments to take action on Silfab zoning issue," July 31, 2026. wbtv.com
• 21. Solar Power World, "Silfab furloughs workers at SC solar panel plant," August 20, 2026. solarpowerworldonline.com
• 22. Queen City News, "Fort Mill students return to classes as Silfab Solar prepare to halt production," August 2026. qcnews.com
• 23. Queen City News, "Silfab Solar defends Fort Mill facility in long-running zoning battle," May 27, 2026. qcnews.com