Below are answers to residents' questions that SCDES had received throughout the course of the environmental permitting process. These FAQs include questions asked or submitted during public comment periods and public meetings about the facility.
When SCDES staff first observed the drip on March 5, the best estimate was approximately no more than one drip to hour. No actual measurements were taken by the Department. The facility informed us that the drip rate was faster when it was first discovered. The tank manufacturer advised the company to tighten the valve, which slowed the drip significantly but did not eliminate the drip. The drip is neutralized and contained inside a storage building. A direct reading sensor for HF is located just above the drip and is consistently reading 0.00 parts-per-million (ppm). A contractor has been hired to determine the safest way to transfer hydrofluoric acid from the tank so it can be repaired.
SCDES has been asked about the labeling of 49% HF at the facility as 3-0-0 instead of 4-1-0. We have reviewed the safety data sheet (SDS) provided to the facility for hydrofluoric acid by the company that supplies them with HF. It lists the health hazard, flammability hazard, and instability hazard as 3-0-0, respectively. According to S.C. OSHA, the facility should use the information found on the SDS provided by the supplier to develop the chemical hazard placards since formulations may vary. SCDES also contacted the supplier to confirm the correct placard coding.
Facilities aren’t required to provide the names and locations of their chemical suppliers to SCDES. Silfab will have this information.
Silfab is required to coordinate its emergency response plans with local emergency response agencies. That coordination is required prior to bringing regulated substances on-site and submitting its risk management plan (RMP) to the EPA. The RMP provides information about possible impacts of a worst-case release scenario and also more realistic release scenarios. Local emergency response agencies use this information to plan for their response.
Silfab is required to perform annual drills/exercises with local response agencies. If a release has the potential to impact schools or nearby residents, SCDES strongly encourages Silfab and local emergency response agencies to include schools and nursing home residents in these exercises.
Decisions on signage, where to go, how long residents should vacate homes, and when residents should return to homes are made by local emergency response agencies and the on-scene incident command. SCDES serves in an advisory capacity role to local emergency response agencies who will be the lead authority for making these decisions. Any possible home contamination claims need addressed with Silfab.
The facility plans to store three regulated substances on-site: silane (a flammable gas), hydrochloric acid (a toxic liquid), and anhydrous ammonia (toxic).
These chemicals are used at many facilities across the country and can be handled safely. Silfab is required to coordinate its emergency response plan with local emergency response agencies to determine the most appropriate procedures in the event an air release or a fire occurs at the site.
Silfab is required to coordinate its emergency response plan with the local emergency response agencies to determine the most appropriate procedures for any fire that may occurs at the site
Silfab is required to coordinate its emergency response plan with the local emergency response agencies to determine the most appropriate procedures and if any personal protective equipment (PPE) is necessary. It’s highly unlikely that PPE would be required outside of the fence-line of the facility.
Silfab is required to coordinate its emergency response plan with the local emergency response agencies to determine the most appropriate procedures for notifying schools, if necessary. Many decisions about these procedures will be made by local emergency response agencies on a case-by-case basis.
Silfab is required to coordinate its emergency response plans with local emergency response agencies. That coordination is required prior to bringing regulated substances onsite and submitting its risk management plan (RMP) to the EPA.
The RMP provides information about possible impacts of a worst-case release scenario and also more realistic release scenarios. These scenarios are generated using modeling software and population data. Local emergency response agencies use this information to plan for a possible response, and Silfab is required to perform annual drills/exercises with these local response agencies. If a release has the potential to impact the schools or nearby residents, SCDES strongly encourages Silfab and local emergency response agencies to include the schools and nearby residents in these exercises.
Silfab is required to coordinate its emergency response plans with local emergency response agencies. That coordination is required prior to bringing regulated substances onsite and submitting its risk management plan (RMP) to the EPA. Local emergency response agencies use this information to plan for their response, and those agencies determine the number of people needed to assist with any emergency.
Public copies of risk management plans can be found at How to Access Risk Management Plan Information | US EPA. Some portions of risk management plans are considered sensitive by state and federal law and aren't available on the public website. Appointments to see the full RMP and this sensitive information must be made in accordance with South Carolina law found at here.
The risk management plan (RMP) provides information about possible impacts of a worst-case release scenario and also more realistic release scenarios.
Silfab submitted its risk management plan (RMP) to the U.S. EPA October 5, 2024. Public copies of RMPs can be found at https://cdxapps.epa.gov/olem-rmp-pds/. Please note that some portions of RMPs are considered sensitive by state and federal law and will not be available on the public website. Appointments to see the full RMP with this sensitive information can be made in accordance with South Carolina state law found here or by visiting a federal reading room.
Prior to bringing the silane and hydrochloric acid on site, the facility is required to comply with the risk management program and submit a risk management plan to the U.S. EPA. This plan shows the impacts of possible accidental releases.
Public copies of risk management plans can be found at https://cdxapps.epa.gov/olem-rmp-pds/. Some portions of risk management plans are considered sensitive by state and federal law and will not be available on the public website. Appointments to see the full risk management plan and this sensitive information must be made in accordance with South Carolina state law or by visiting a federal reading room.
Silfab is required to coordinate its emergency response plans with local emergency response agencies, and that coordination is required prior to bringing regulated substances onsite and submitting its risk management plan (RMP) to the EPA. The RMP provides information about possible impacts of a worst-case release scenario and also more realistic release scenarios. Local emergency response agencies will use this information to plan for a possible response. Notifications to the public will be made by the local emergency response agencies and the on-scene incident command as needed.
Facilities also are required to report leaks or releases that exceed a reportable quantity (RQ) that leave the plant property promptly to the EPA National Response Center (NRC) and SCDES. Reportable quantity (RQ) thresholds can be found at https://www.epa.gov/epcra/consolidated-list-lists. Reports sent to the NRC are available to the public and can be found at: https://www.epa.gov/emergency-response/national-response-center. If a leak or release is below the RQ and does not go offsite, no notification is required.
When a facility submits an air permit application, it is required to assume 24/7 operations to determine the worst-case air emissions, even if the facility does not plan to operate that many hours. The air quality analysis submitted with the permit application considered offsite public receptors (such as schools, businesses, and parks) and demonstrated that the facility would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence line.
The Occupational Safety and Health Administration (OSHA) requires chemical manufacturers to develop a safety data sheet (SDS) for each hazardous chemical they make or import. The SDS includes information about chemical uses and safety. The SDS is given to facilities that use these chemicals and the facility is required to maintain the SDS onsite. OSHA also requires that all employees be trained on how to safely handle all chemicals onsite. The facility is not required to retest the chemicals.
Once the facility starts solar panel production, air emission stack testing will be required. The initial stack test for hydrochloric acid (HCl) and hydrogen fluoride (HF) emissions will be required within 45 days of achieving the maximum production rate or within 180 days of starting operation, whichever comes first. This testing will be required every two years thereafter. Silfab will be required to hire a third-party testing company to perform the testing. SCDES staff will be on-site to ensure the test is done properly.
In addition to stack testing, the facility will be required to monitor certain parameters daily in accordance with the conditions of its air permit to verify compliance with emission limitations and operational requirements. SCDES will perform unannounced inspections to assess operations, inspect the equipment and review monitoring records. The lowering of the stack height to meet county code (and the related appeal) do not impact the testing procedures or frequency.
SCDES doesn’t regulate the transport of chemicals. Silfab could provide this information.
SCDES regulates certain substances above certain quantities in tanks and containers.
Silfab has proposed to store two 5,280-gallon tanks of hydrochloric acid (HCl), two 7,925-gallon tanks of hydrogen fluoride (HF), one 22,983-gallon tank of silane and a 22,000-lbs tank of anhydrous ammonia. Silfab will also store diesel fuel on-stie to use in emergency generators. Other substances may be stored onsite in quantities that are not regulated. Not every chemical poses a risk to people or the environment. Pollutants are selected to be regulated based on whether and to what extent they can have negative effects on human health or the environment.
Silfab was required to submit a risk management plan (RMP) to the EPA that also was shared with SCDES. This plan outlines how the facility plans to prevent accidental releases and its safety protocols. It also shows how the facility has coordinated its emergency response plan with local emergency response agencies. The facility is required to submit the RMP to EPA before it brings regulated substances on site. Silfab submitted its RMP to the EPA on Oct. 5, 2024, and it was reviewed by SCDES. Once the facility is operating, experienced SCDES staff will conduct unannounced inspections. Contractors are not required and will not be used. The frequency of these inspections hasn’t been determined yet.
Companies produce solar cells and panels differently -- no two facilities are identical. SCDES is aware of at least two existing facilities in operation in Georgia and three permitted facilities in South Carolina. There may be other future projects.
ES Foundry is very similar to Silfab and uses silane, hydrochloric acid (HCl) and hydrogen fluoride (HF), with similar air emissions. It has been in operation for more than a year.
Abner Solar received its air permit in November 2025 and isn't operational yet. It will use similar chemicals as Silfab Solar and ES Foundry.
Of note, the semiconductor industry uses the same types of chemicals and has similar processes and emissions as the solar panel industry. SCDES is aware of at least two semiconductor facilities in the country, in Midland, Mich., and Austin, Texas.
No. The facility in Washington State only assembles solar panels. The chemicals used at the Washington site are for cleaning and soldering the panels. These chemicals are not the same as those for Silfab Solar in Fort Mill.
Companies produce solar panels differently; no two facilities are identical. SCDES is aware of two existing facilities in operation in Georgia and two recently permitted facilities in South Carolina:
The Greenwood facility is very similar to Silfab and will also use silane, hydrochloric acid (HCl) and hydrogen fluoride (HF) and will have similar air emissions. It's our understanding that the zoning for the Greenwood facility is Light Industrial, however, zoning definitions vary by municipality.
The Georgia facilities use chemicals similar to the chemicals Silfab and ES Foundry plan to use but in smaller quantities.
Of note, the semiconductor industry uses the same types of chemicals and has similar processes and emissions as the solar panel industry. SCDES is aware of at least two semiconductor facilities in the country, in Midland, Mich., and Austin, Texas.
Silane is not a regulated air pollutant and not an air toxic. It is regulated as a flammable gas under the risk management program.
There are many facilities in South Carolina and across the country that report emitting toluene, hydrogen fluoride, VOCs and hydrochloric acid emissions annually. In South Carolina, at least 260 facilities report emitting at least one of these pollutants; at least 150 emit two of these pollutants; at least 60 facilities facility emit three of these pollutants; and at least 20 facilities emit all four of these pollutants. Requests for this list can be obtained by contacting our Freedom of Information office.
SCDES does not have zoning information for these locations, as zoning requirements vary by municipality. Some areas have no zoning laws at all.
All facilities that are required to obtain an air permit are required to perform an air quality analysis. The air quality analysis performed for Silfab demonstrated the facility would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence line.
Only regulated air pollutants and regulated substances under the risk management program (RMP) are required to be listed in the air permit application. Some chemicals may be stored or used onsite in quantities below regulated thresholds or exemption level and, therefore, do not need to be included in the air permit.
Facilities are allowed to release some level of air pollution as long as state and federal standards and air permit limits are met. These state and federal air quality standards are established to be protective of public health, especially children, the elderly, and those with respiratory conditions beyond the fence line of a permitted facility.
The air permit SCDES issued to Silfab in March 2024 limits the amount of air pollutants that can be released by the facility. It requires the air scrubbers to remove air toxic pollutants by at least 96%. The remaining emissions will be emitted through an exhaust stack.
An air dispersion analysis was performed to simulate the dispersion of these air pollutants from the stack into the ambient air. This analysis showed the air emissions would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence-line.
If the scrubber system becomes inoperable, the process will automatically shut down. The air permit also requires Silfab to notify SCDES of any malfunction or upset that lasts more than one hour if emissions exceed the specified limits. It’s also required to minimize any excess emissions. The facility must monitor the operations of the air scrubber regularly and document readings to ensure it is operating properly in accordance with the manufacturer’s specifications. Records of this documentation will be periodically reviewed by SCDES inspectors.
Silfab will use a wet acid scrubber system to control air toxic emissions. More than 50 facilities across South Carolina use scrubbers to control air emissions every day. Many of these facilities are required to test their scrubbers and have shown compliance with their air permit limits on a regular basis. Scrubber parameters, including pressure drop, liquid flow rate, and pH, will be monitored and recorded daily by Silfab staff to ensure the scrubber system is operating effectively. Also, if the scrubber system becomes inoperable, the process will automatically shut down.
The initial stack test for hydrochloric acid (HCl) and hydrogen fluoride (HF) emissions will be required within 45 days of achieving the maximum production rate or within 180 days of starting solar production operation, whichever comes first. This testing will be required every two years thereafter. Silfab will be required to hire a third-party testing company to perform the testing. SCDES staff will be on-site to ensure the test is done properly.
In addition to stack testing, the facility will be required to monitor certain parameters daily in accordance with the conditions of its air permit to verify compliance with emission limitations and operational requirements. SCDES will perform unannounced inspections to assess operations, inspect the equipment and review monitoring records.
First, SCDES will review the stack test data and report to determine compliance with the air permit. Any potential violations would result in the facility being referred to the enforcement section of the agency’s Bureau of Air Quality. If the enforcement section confirms that a violation has occurred, enforcement
An environmental impact study (EIS) is a tool that is used for identifying and analyzing specific activities that are determined to likely have a significant adverse environmental impact. They are performed by federal government agencies and are only required by federal law for some projects that use federal land, federal tax dollars, or are under federal agency jurisdiction.
An EIS was not required for this site. However, a state air quality construction permit was required. SCDES performed a thorough technical review of the air permit application and provided the public opportunities to provide input prior to the issuance of the air permit.
Silfab’s air permit was issued on March 1, 2024: AIR-ConstructionPermit-CP-50000090.pdf.
This air permit outlines all the recordkeeping, reporting, testing, and monitoring requirements to meet state and federal air quality standards. SCDES staff enforce these requirements by conducting unannounced compliance inspections and complaint investigations, reviewing periodic compliance reports and onsite inspection logs, observing stack tests performed by a third-party, and taking enforcement action when violations are found.
The monitoring and testing requirements are outlined in the air permit. More details about the monitoring and testing requirements can be found in the Response to Comments Document at Silfab-Solar-Response-to-Comments-on-Air-Quality-Draft-Permit.pdf starting on page 4.
Wastewater from the facility will be pre-treated onsite and then discharged to the City of Rock Hill’s sewer system. The City of Rock Hill will be required to notify SCDES of the quality and quantity of the water being discharged to their system and any anticipated impact on the quantity or quality of water to be discharged from their system. SCDES regulates the City of Rock Hill’s discharges to ensure appropriate protections are in place for waters that may be a source of drinking water.
Silfab demonstrated its air emissions could meet all state and federal air quality standards. The federal standards were established to be protective of public health and the environment. There are no anticipated impacts to soil, wildlife or waters.
A traffic study was performed for this site by S.C. DOT, which can best answer this question.
SCDOT performed a traffic study for this site and is the best agency to answer this question.
Zoning and land use decisions are made by city or county zoning authorities. The interpretation, application, and enforcement of county zoning ordinances are outside of SCDES's authority.
The agency doesn’t have the authority to dictate where a facility may or may not be located or make zoning decisions. These zoning and land use decisions are made by city or county zoning authorities. The agency’s role is to ensure a facility operates in compliance with the environmental permits that are issued in order to protect people’s health and the environment.
SCDES was aware Silfab would be using an existing warehouse located in an area that is zoned by the county as Light Industrial District (LI). Zoning and land use decisions are made by city or county zoning authorities. The interpretation, application, and enforcement of county zoning ordinances are outside of the agency's authority. SCDES's role is to ensure a facility operates in compliance with the environmental permits that are issued in order to protect people’s health and the environment.
Zoning and land use decisions are made by city or county zoning authorities. The interpretation, application, and enforcement of county zoning ordinances are outside of the agency's authority. SCDES's role is to ensure a facility operates in compliance with the environmental permits that are issued in order to protect people’s health and the environment.
The agency doesn't have the authority to dictate where a facility may or may not be located or make zoning decisions. These zoning and land use decisions are made by city or county zoning authorities. The agency’s role is to ensure a facility operates in compliance with the environmental permits that are issued in order to protect people’s health and the environment.
An air quality analysis was performed for the three air toxic pollutants, and the analysis demonstrated the facility would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence line.
SCDES isn’t involved with real estate issues.
After the facility begins operations, air emission stack testing will be required. The initial stack test for HCl and HF emissions will be required within 45 days of achieving the maximum production rate or within 180 days of starting operation, whichever comes first. This testing will be required every two years thereafter. Silfab will be required to hire a third-party testing company to perform the testing. SCDES staff will be on-site to ensure the test is done properly.
In addition to stack testing, the facility will be required to monitor certain parameters daily in accordance with the conditions of its air permit to verify compliance with emission limitations and operational requirements. SCDES will perform unannounced inspections to assess operations, inspect the equipment and review monitoring records.
Silfab is the first solar panel production facility to receive an air permit in South Carolina. A second solar panel production facility has received an air permit in Greenwood.
More than 2,000 facilities in South Carolina have air permits issued by SCDES (or the former DHEC). Experienced SCDES permitting engineers and inspectors perform their duties with respect to these 2,000+ facilities across the state. There are no specific credentials required for permitting and inspecting solar panel facilities.
No air permit from SCDES is required for the warehousing and distribution of solar panels.
SCDES was aware Silfab would be using an existing warehouse to produce solar panels and that this warehouse is located in an area that is zoned by the county as Light Industrial District (LI). Zoning and land use decisions are made by city or county zoning authorities.
The interpretation, application, and enforcement of county zoning ordinances are outside the agency's authority. SCDES's role is to ensure a facility operates in compliance with the environmental permits that are issued in order to protect people’s health and the environment.
Not all chemicals are regulated pollutants. There may be some chemicals stored onsite that are exempt from permitting or may not be regulated by state or federal regulations.
All regulated air pollutants, including air toxics, were evaluated and addressed in the air permit. The county conducted the technical review for the stormwater runoff permits for the site. If the facility generates any hazardous waste after it starts operation, it will be required to comply with state and federal hazardous waste generator laws.
The air quality analysis submitted with the permit application included the location of the two new schools and demonstrated that the facility would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence line.
The disposal of wastes and landfills are regulated by SCDES’s land and waste program. If the facility generates any hazardous wastes after it starts operation, it will be required to notify SCDES and comply with the state and federal hazardous waste generator laws.
EPA Region 4’s Senior Toxicologist provided the following responsse:
“EPA notes that there is not presently a source standard for solar panel manufacturing pursuant to Clean Air Act section 112. This facility will be a synthetic minor facility for HAPs, meaning emissions will be restricted below “major source” thresholds of 10 tons per year of individual HAPs, or 25 tons per year of combined HAPs, so there is also no requirement for a case-by-case maximum achievable control technology determination. This means there is no federal requirement to continuously monitor emissions of HCl or HF at the facility.
However, Condition B.1 of the air permit limits overall annual HAP emissions from the facility, and Condition B.6 requires a specific efficiency of wet scrubbers intended to control the emissions of these pollutants. Condition B.6 requires initial and ongoing testing of these scrubbers, which will establish the operational ranges required to be established in Condition B.7. Condition B.8 then requires that several parameters indicating the adequate operation of the scrubbers must be measured and recorded daily. The permit further states at Condition B.8 that “Each scrubber shall be in place and operational whenever processes controlled by it are running.” This means that the manufacturing process is required to be controlled to this degree at all times. Conditions B.4 and B.8 require that any deviations from established operational ranges are reported along with any corrective actions at least semiannually, which is consistent with reporting requirements for major sources and other stationary source programs. Should there be downtime for the wet scrubbers, the process should be halted. Permit Condition B.1 requires emissions from malfunctions to be included in determining compliance with the annual emission limits, and as noted above, any deviations from normal operating parameters are recorded and reported. Further, Condition F.5 contains a reporting requirement within 24 hours after the beginning of the malfunction of air pollution control equipment for any discharges lasting for one hour or more. The State will therefore have the information necessary to determine compliance with the permit conditions.
Should there be accidental releases from the storage of these chemicals, that occurrence would not be considered part of normal operation, so the State’s risk management plan regulations establish requirements to address this scenario. Specifically, the permit requires the submission of a risk management plan for HCl and for silane. This plan is used to inform local emergency response agencies.
The State’s initial response to comments document, along with the newer “Q and A” document at the website identified previously, address some of these issues in greater detail. Please continue to follow up with South Carolina Department of Environmental Services’ Air Permitting Division with specific concerns.”
Any potential air permit violation would result in the facility being referred to the agency’s Air Compliance Management Division within the Bureau of Air Quality. If the agency confirms that a violation occurred, we will require any necessary corrective actions and may impose civil penalties.
The facility must correct a violation within a reasonable timeframe. SCDES will pursue necessary enforcement or other action to address any ongoing noncompliance.
Companies produce solar cells and panels differently -- no two facilities are identical. SCDES is aware of at least two existing facilities in operation in Georgia and three permitted facilities in South Carolina. There may be other future projects.
ES Foundry is very similar to Silfab and uses silane, hydrochloric acid (HCl) and hydrogen fluoride (HF), with similar air emissions. It has been in operation for more than a year.
Abner Solar received its air permit in November 2025 and isn't operational yet. It will use similar chemicals as Silfab Solar and ES Foundry.
Of note, the semiconductor industry uses the same types of chemicals and has similar processes and emissions as the solar panel industry. SCDES is aware of at least two semiconductor facilities in the country, in Midland, Mich., and Austin, Texas.
No. The facility in Washington State only assembles solar panels. The chemicals used at the Washington site are for cleaning and soldering the panels. These chemicals are not the same as those for Silfab Solar in Fort Mill.
Companies produce solar panels differently; no two facilities are identical. SCDES is aware of two existing facilities in operation in Georgia and two recently permitted facilities in South Carolina:
The Greenwood facility is very similar to Silfab and will also use silane, hydrochloric acid (HCl) and hydrogen fluoride (HF) and will have similar air emissions. It's our understanding that the zoning for the Greenwood facility is Light Industrial, however, zoning definitions vary by municipality.
The Georgia facilities use chemicals similar to the chemicals Silfab and ES Foundry plan to use but in smaller quantities.
Of note, the semiconductor industry uses the same types of chemicals and has similar processes and emissions as the solar panel industry. SCDES is aware of at least two semiconductor facilities in the country, in Midland, Mich., and Austin, Texas.
Silane is not a regulated air pollutant and not an air toxic. It is regulated as a flammable gas under the risk management program.
There are many facilities in South Carolina and across the country that report emitting toluene, hydrogen fluoride, VOCs and hydrochloric acid emissions annually. In South Carolina, at least 260 facilities report emitting at least one of these pollutants; at least 150 emit two of these pollutants; at least 60 facilities facility emit three of these pollutants; and at least 20 facilities emit all four of these pollutants. Requests for this list can be obtained by contacting our Freedom of Information office.
SCDES does not have zoning information for these locations, as zoning requirements vary by municipality. Some areas have no zoning laws at all.
All facilities that are required to obtain an air permit are required to perform an air quality analysis. The air quality analysis performed for Silfab demonstrated the facility would not exceed any state or federal health-based standards that are protective of public health and the environment beyond the fence line.
There is no Dow Company facility currently operating in South Carolina. We are not aware of the chemicals this company does or doesn't use.
