Westerly council hears $72 million wastewater plant upgrade plan to meet lower nitrogen limits

Engineers for the Westerly Upgrades project told the Town Council on Feb. 10 that the town’s wastewater treatment facility needs comprehensive rehabilitation to meet a new effluent permit and flood‑resiliency standards. John Tobia, project manager, told the council the “driver for the project is … effluent permit compliance,” and that the existing permit will require lower nitrogen and ammonia concentrations in plant discharge.

The presentation said the permit’s new limits are 5 milligrams per liter of total nitrogen and 1.7 milligrams per liter of ammonia, down from the plant’s current limits of 15 mg/L nitrogen and 5.5 mg/L ammonia. Tobia said the facility plan amendment completed after higher winter flows in early 2024 requires a broader set of improvements, and he described the work as “comprehensive,” affecting nearly all plant areas.

Why it matters: The plant serves about 16,000 people (roughly 45% of properties in town) and is permitted for an average monthly flow of 3.3 million gallons per day (MGD). The project team estimated a $72,000,000 construction budget to add two new aeration basins to meet the lower nitrogen limit, replace the plant electrical backbone, add pumping and generator capacity, and make chemical storage and some process equipment flood resilient.

Key technical details and schedule: Tobia said the facility plan amendment addresses higher winter wet‑weather flows, and that the design submission the town must send to Bridal (the permitting authority named in the presentation) is due no later than March 11, 2025. He described the near‑term submittal as the 90% design milestone that will be transmitted as an “order of approval” application to Bridal. He estimated Bridal’s review at roughly three months and then a back‑and‑forth period before final approval. Construction duration was estimated at about 28–31 months under the team’s progressive design‑build delivery model; that timetable exceeds the two‑year construction window named in the consent agreement, an issue Tobia said the project team will need to discuss with Bridal.

On capacity and future service: The design does not increase permitted flow (remains 3.3 MGD) but includes conservatism that could allow about a 15% gain in treatment capacity if the town later pursues a permit modification and additional approvals; that conservatism is equivalent to roughly 522 planning units (about 1,200 people) built into the design, the team said.

Flood resiliency approach: Tobia reviewed mapped flood elevations around the plant: a 100‑year planning flood at elevation 14.9, a next increment at elevation 17 (100‑year plus 2 feet of sea‑level rise), and a higher planning increment tied to 3 feet of sea‑level rise (around elevation 17.9 in the presentation). The initial facility plan had proposed a large flood berm between the river and plant, but a 30% design cost estimate showed that berm would exceed the project budget, so the team has changed approach: all new electrical and process equipment will be raised above the higher planning flood elevation, and existing structures will be protected with flood doors and raised concrete walls for chemical storage; further engineering will assess whether some secondary clarifiers and tanks can be raised.

Budget and risk: Councilors pressed the project team on the price tag and schedule. Tobia said the $72 million figure is the current construction estimate; if the town cannot commit additional funds the team would consider scope reductions. Town staff emphasized the town’s budget planning and borrowing capacity conversations are ongoing; the manager’s office later noted roughly $3 million in grants had been identified toward the project but that the bulk of funding would be by bond.

Council questions and next steps: Councilors asked how the 15% potential capacity increase was built into the design and what minor capital changes would be needed to realize it; Tobia said additional aeration equipment (air dispersion grids in the new basins) and some permitting would be required. On the schedule risk of exceeding the consent agreement two‑year construction period, Tobia told the council: “If you have facts, bring them back to us, and we’ll have another discussion,” and confirmed the team will raise schedule concerns with Bridal as part of the order‑of‑approval review. The project manager said the team will submit the 90% design to Bridal by the March deadline, proceed through Bridal review and environmental permitting, and return to the council with updated cost and schedule information as the design evolves.

Taper: The council did not take any formal votes that evening on design approvals or funding; the presentation was entered as a status update and the council asked staff to continue working with the engineering team and to return with clarifying memos on projected costs, schedule risks tied to the consent agreement, and grant opportunities.