One or more PFAS compounds exceed EPA Maximum Contaminant Levels. This is not a current violation — the federal compliance deadline is April 2029 (a proposed extension to 2031 is not final). These are UCMR 5 results from 2023 to 2025; the system may have installed treatment since.
Key contaminants vs MCL
PFOA4.7 ppt(MCL: 4 ppt)
PFOS6.5 ppt(MCL: 4 ppt)
EPA MCL: 4 ppt (parts per trillion) for PFOA and PFOS individually. Compliance deadline: April 26, 2029 under the current rule.
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As printed in the state's own documents. Amounts are not added together: each is a different kind of figure.
Jun 26, 2026 · CWS recently completed bench-scale and full-scale testing of powdered activated carbon (PAC) to identify improvements necessary for PFAS treatment as part of the Charleston Water System PFAS Study. Based on the study findings, CWS plans to move forward with the initial Phase 1 improvements, including detailed design of a properly sized PAC Storage and Feed Facility to ensure compliance with finalized USEPA National Primary Drinking Water Regulation (NPDWR) as well as SCDES SPDWR requirements for surface water treatment facility design. The project will include detailed design services for a new PAC system with four (4) silos and eight (8) feeders, providing a minimum of thirty (30) days of PAC storage under average flow and design dose conditions and sufficient metering capacity to meet HWTP design flows. · $1.5M
On SRF fundable list (Provisional Priority List). Source →
Jun 26, 2026 · CWS recently completed bench-scale and full-scale testing of powdered activated carbon (PAC) to identify improvements necessary for PFAS treatment as part of the Charleston Water System PFAS Study. Based on the study findings, CWS plans to move forward with the initial Phase 1 improvements, including detailed design of a properly sized PAC Storage and Feed Facility to ensure compliance with finalized USEPA National Primary Drinking Water Regulation (NPDWR) as well as SCDES SPDWR requirements for surface water treatment facility design. The project will include detailed design services for a new PAC system with four (4) silos and eight (8) feeders, providing a minimum of thirty (30) days of PAC storage under average flow and design dose conditions and sufficient metering capacity to meet HWTP design flows. · $1.5M
On state DWSRF priority list (requested). Source →
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Oct 22, 2024 · The HWTP is planning a PFAS treatment project to meet the recently-released USEPA PFAS regulations. Several Powdered Activated Carbon (PAC) products will be evaluated and testing results will be analyzed to provide a basis of design for the full scale plant. The study will involve bench-scale testing for powdered activated carbon (PAC) to determine the most suitable product, dose, and contact time for PFAS treatment at the HWTP. In addition, the bench-scale testing protocol will also include analyses to evaluate the effects of PAC on other source water characteristics (e.g., total organic carbon (TOC), pH, alkalinity, etc.), as well as effects on water treatability based on the existing/planned HWTP unit processes. Based on the results of the study, a Preliminary Engineering Report (PER) for the PFAS treatment project will be developed. · $650k
On SRF fundable list (Provisional Priority List). Source →