Lewisboro officials outline plan for septic maintenance district to cut lake phosphorus

Lewisboro officials on a hot summer evening presented a plan to form a septic maintenance district that would replace or upgrade failing septic systems around several lakes, aiming to reduce phosphorus pollution that local studies have flagged as a principal driver of algae growth.

Town staff and consultants said they shifted from pursuing a centralized wastewater treatment plant after multi-year grant attempts failed and cost estimates rose. "We were looking at a sewer approach ... but the sewer costs grew ... so the decision was made to consider this pivot to a septic district," said Tony, the town supervisor, explaining the change in direction and grant history.

The engineers described the proposed technology and scope. Consultants said the Fuji Clean CRX2 unit under consideration is an advanced on-site treatment device that, in recent testing and certification, can remove "up to approximately 90% of phosphorus" from treated flow. The project team identified about 131 homes in the Lake Kitchwan watershed as part of an initial installation set; the funding scenario under discussion could allow upgrades for roughly 500–600 parcels overall, compared with about 300 under the prior wastewater-plant plan.

Officials emphasized the financial differences between the two approaches. Presenters said earlier wastewater-plant estimates ranged into the tens of millions (the team described initial estimates of roughly $40 million that later increased) and would have required higher annual homeowner assessments — previously estimated near $1,450 a year. The septic-district approach was presented as a lower-capital option with an estimated district assessment of about $600 a year per household plus a modest electric cost for the unit blower (presenters used $10–$12 per month as an upper-range placeholder).

Consultants walked residents through how the advanced septic units work and how the district would operate. The on-site units still use a tank and leach field footprint similar to conventional systems but add an internal aerobic treatment stage and a small blower. "It's actually like a miniature wastewater treatment plant in your yard," said Tia, a consultant, describing the treatment stages, visible access lids and a small blower that would be sited near the house. Under the district model the town would own and manage a responsible management entity to handle routine pump-outs, an annual inspection program and maintenance contracts.

Residents asked technical and practical questions about the plan: whether the units address nitrates (consultants said the Fuji Clean units are focused on phosphorus removal for freshwater lakes), whether existing leach fields would be reused (Westchester County Department of Health guidance cited by staff calls for replacing leach fields when systems are upgraded) and what happens during power outages (staff said units revert to passive septic behavior until power is restored). The presenters also committed to supplying more detail on costs, a map/plan/report required by New York Town Law, and demonstration information before a vote.

Quality-of-life concerns came up during public comment. Chief Petro, a resident, said the lakes and wildlife are part of what draws people to the area and asked about noise and visual impacts; staff replied that the blower is low-decibel and that lids and equipment can be visually mitigated. Other residents asked how the plan would handle small, irregular lots or sites with limited leach-field area; officials said such cases would be handled during design and that the county health department typically allows site-specific engineering so long as replacements do not make a property "worse than it is now."

Officials described the legal path and timeline: the town board would initiate a map/plan/report under New York town law, the proposed district boundaries would be set, a public hearing would be held, and affected voters in the proposed district would vote in a referendum; if approved, the town would proceed to design, permitting and construction. Staff said only properties inside the formed district would pay the assessment, and properties added later would be subject to whatever rules the district establishes.

Organizers stressed the project is intended as a pragmatic step to reduce ongoing phosphorus inputs rather than an immediate cure for decades of accumulated nutrient loading in lake sediments. "Removing the new inputs helps the future, but it can take years for lakes to respond," a presenter said, noting precedent where full sewering or other interventions took decades to materially change lake conditions.

Next steps: the town plans further outreach, another informational session and the formal map/plan/report and public hearing processes required before putting a district referendum to affected voters. If the town proceeds, the referendum vote would determine whether assessed properties become part of the district and whether the town may form and operate the maintenance program described by staff.