Silfab Solar plans to restart chemical and gas systems at its Fort Mill plant no sooner than mid-October after a safety review flagged monitoring and code gaps.

The company released the independent review and related documents on Wednesday, Sept. 30, fulfilling requirements of its March 16 compliance agreement with the South Carolina Department of Environmental Services (DES). The agreement followed a March 3 chemical spill at the plant at 7149 Logistics Lane, which shares a property line with Flint Hill Elementary and Flint Hill Middle schools.

YoCo News first reported the review's release and details.

TRC Engineers Inc. reviewed the plant from April through August 2026. The firm credited double-wall piping, storage rooms built to hold a full tank and about 26 toxic gas monitors. TRC concluded that Silfab's safety measures were consistent with industry standards for the chemicals on site.

The review carries a significant caveat. Because commissioning was paused, TRC could not observe equipment running or test alarms. The report states it provides no certification or guarantee.

Code gaps and a June evacuation

TRC's code review marked five areas where the plant's design did not meet code or documentation was missing. Those included no gas monitors in exhaust ducts from the silane and ammonia enclosures and an ammonia relief valve venting beneath a canopy.

TRC also found no containment around the scrubber and no method to control vapors from a roof vent if acid spilled in the hydrofluoric and hydrochloric acid storage room.

The firm observed a June 3 evacuation triggered by a propane incident. The plant's intercom was not fully installed at the time. Managers used Microsoft Teams messages and verbal instructions to direct workers out.

Fort Mill School District officials told TRC that parents call schools each time an emergency vehicle responds to the plant. District officials also said Silfab's notifications to the schools had dropped off in recent months.

Silfab's fixes

Director of Operations Greg Basden signed Silfab's response, agreeing with all 20 of TRC's recommendations. The company reported eight already closed, including new gas monitors, an 18-by-50-foot opening cut into the ammonia canopy and a working intercom. Remaining items carry October target dates.

Of 23 additional best practices TRC suggested, Silfab said 15 are complete and six remain under review. Among the unfinished items: a formal hazard study that Silfab said has no confirmed timeline and added ventilation for the acid storage room.

Silfab said it will notify Fort Mill schools of any Level 3 incident, its most serious category.

March spill traced to frozen valve

Silfab's April 13 analysis traced the March 3 spill to a water valve on the scrubber that likely failed in freezing weather. An operator filling the unit by hand overfilled it.

About 300 gallons of water containing 0.5 percent potassium hydroxide escaped through a broken drain line into the on-site stormwater pond. Silfab said the water did not leave the property, and the pond was emptied at York County's request.

What comes next

Silfab must give DES 72 hours' notice before receiving chemicals or restarting commissioning. The company's media statement puts the earliest restart at Oct. 18; the schedule filed with DES lists Oct. 19. The Herald also confirmed the 72-hour notice requirement and the Oct. 18 target.

The company hired Jamie Watts as corporate Director of Health and Safety on Sept. 10, WCCB reported. Watts holds a chemical engineering degree from N.C. State and has more than 30 years of safety experience.

Silfab's appeal of a circuit court ruling that solar cell manufacturing is not permitted under the site's light-industrial zoning remains pending. York County Circuit Court Judge Bill McKinnon upheld the Board of Zoning Appeals decision in July 2026, according to The Herald.

Residents who see an emergency at the plant can call the Fort Mill Police Department at 803-547-2022 or dial 911.