Tequesta workshop endorses phased approach to meet new PFAS rule; consultants recommend ion‑exchange retrofit and RO upgrades

At a June 1 workshop, the Village of Tequesta heard a Kimley Horn master‑plan presentation that recommended a phased strategy to meet upcoming federal and state limits on PFOA and PFOS. Consulting engineer Nick Black told council the village can pursue a near‑term retrofit of two existing filter vessels with ion‑exchange resin to remove PFAS from the surficial well supply and simultaneously shift more production to the Florida‑aquifer reverse‑osmosis (RO) system.

The plan is a two‑phase course: Phase 1 would treat the 2.73 million gallons‑per‑day surficial flow with a targeted PFAS polishing system, estimated at about $3 million in capital costs; Phase 2 would expand RO capacity and supporting systems, estimated around $3.5 million. Black said the recommendation is intended to meet a 2029 compliance deadline tied to an MCL of 4 parts per trillion for PFOA and PFOS while avoiding the immediate capital expense of a full RO conversion.

Why it matters: the village currently blends surficial and Florida aquifer supplies (roughly a 70/30 blend in normal operations). Kimley Horn’s testing found higher PFAS concentrations in the surficial wells; because those wells account for roughly 30% of blended flow, the source concentrations can exceed the upcoming rule’s limits even if finished‑water concentrations are diluted. Black emphasized the difference between detection limits and enforceable standards: existing EPA methods measure in parts per trillion and analytical uncertainty at low levels can be ±20 percent.

How the options compare: consultants outlined three primary approaches. Ion‑exchange vessels use selective resins to target PFAS and have lower capital cost, but the resin becomes exhausted and requires off‑site disposal and periodic replacement (Stewart, a nearby utility, changes resins roughly every 10 months, Black said). Granular activated carbon (GAC) is effective for some PFAS but competes with organics and color in South Florida groundwater, increasing breakthrough risk. Nanofiltration or full‑scale RO is the most comprehensive technical fix but creates a PFAS‑laden concentrate stream that requires expensive, engineered disposal (deep injection wells can cost tens of millions) or larger outfall capacity.

Council questions focused on timing, water‑use permitting, and funding. Council Member Brandon asked whether the Village could meet the April 2029 deadline: consultants said concurrent design and permitting for both phases could make it feasible but that there is “not much wiggle room.” Staff flagged funding avenues including the emerging‑contaminants SRF program (which may offer principal loan forgiveness), alternative water supply grants, and traditional SRF loans if grant funding is unavailable.

On operations and resiliency, Kimley Horn noted the plant’s clear well (about 30 years old) is a single point of failure; storage on site (about 2.5 million gallons) provides less than a day of capacity at peak flows. The consultant recommended budgeting for a redundant clear well and further planning for distribution of pumpage across Florida wells to limit salt‑water intrusion risks.

Next steps: staff said a work authorization for design is expected at a regular council meeting next week, and a facilities plan seeking SRF inclusion is in progress. Allison Berg, utilities director, told council the Village will pursue the facilities‑plan funding pathway and immediate design and permitting so construction can be staged to meet regulatory timelines.

Representative quote: Kimley Horn’s Nick Black said, “A phased approach — retrofitting two vessels for ion‑exchange and improving RO recovery — is the most cost‑effective path to meet compliance in the near term without a full RO conversion today.”

The council did not take a final vote on construction but directed staff to move forward with design, permitting and funding efforts and to return with formal contract and funding recommendations.