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Concord officials hear $30 million plan to fix Hall Street wastewater plant ahead of housing growth
Summary
City engineers told the Concord City Council the Hall Street Wastewater Treatment Plant is near its organic-loading limit and recommended new aeration tanks and equipment at an estimated $30 million, with a roughly five‑year design-to-construction timeline and a two‑year window before the plant's discharge permit expires.
City officials on Monday heard a presentation on needed upgrades to the Hall Street Wastewater Treatment Plant that city staff and consultant Wright-Pierce said will require roughly $30 million and about five years to design and build.
The work is aimed at increasing the plant's ability to remove organic loading and ammonia from wastewater as Concord faces a wave of housing development. "The Hall Street plant takes about 75% of the flow from the city of Concord," Wright-Pierce Senior Project Manager Mike Terrio told the council, and the plant's secondary biological treatment capacity is strained because one of two bio-tower treatment units is offline and the other is operating at significantly reduced effectiveness.
Why it matters: The plant was built in the 1970s and 1980s using bio-tower technology that has since produced persistent odor issues and, in Concord's case, a loss of reliable treatment capacity. Wright-Pierce and the city say rebuilding the bio towers alone would not buy enough future capacity; instead the recommendation is to add new aeration tanks, blowers and electrical equipment on the south side of the existing aeration basins so the plant can treat stronger waste streams and anticipated residential growth.
Details and timeline: Consultants said the primary driver is organic loading strength (BOD) rather than simply peak flow. Terrio told the council that conservation and other changes have lowered flow volumes while raising the concentration of organic matter, so the plant's effective loading capacity is now limited. The project scope as presented includes supplemental aeration basins, piping and a new building for blowers and electrical gear; Wright-Pierce estimated "approximately $30,000,000," and warned material and labor cost volatility could push that figure higher. The city manager and consultants said the work could be planned and delivered over about five years, and the plant's discharge permit will need revision in roughly two years, making early planning advisable.
Funding and rate impacts: City staff and the city manager said the upgrades would be reflected in the capital budget and drive future rate calculations. The city manager told councilors that users pay through user fees that cover capital costs and that larger users (for example state facilities discussed in council questions) pay the same user fee share as other customers; no separate additional state contribution was reported. Councilors discussed impact fees and legal limits: the manager explained impact fees must be tied to creation of new capacity, and cannot be used for ordinary repairs.
Council questions and clarifications: Councilors asked whether current high-strength dischargers exist and whether pretreatment standards would be enforced; Wright-Pierce and city staff said some businesses currently discharge higher-strength waste and the city will pursue pretreatment guidelines to reduce load and potentially reduce project cost. Consultants said one bio tower is offline and the remaining unit is operating at "less than 50%" capacity (figures given as operational estimates).
What comes next: Staff recommended advancing the engineering and capital planning work ahead of the permit renewal window to avoid a compressed schedule under New Hampshire DES or EPA requirements. Consultants said preliminary planning and design now will give the city options and timing to match development trajectories.
Ending: Councilors thanked the presenters for the briefing and asked staff to include the project in capital budget planning and rate modeling. No formal action or appropriation was taken at the meeting; staff said they will return with capital-budget proposals and permitting steps for future council consideration.
