Thornbury's treatment plant has expanded. The next housing constraint sits upstream.

More treatment capacity does not resolve every connection

In May, the town announced completion of the Thornbury treatment expansion. Rated capacity rose from 3,580 to 5,330 cubic metres per day, an increase of 48.9%. That is a measure of wastewater treatment, not a 48.9% increase in homes that can immediately receive building permits. Collection pipes, pumping capacity, existing commitments and individual approvals still determine how the extra treatment can be used. [Thornbury treatment expansion completion announcement] [Municipal water and sewer capacity record] [Mill Street pumping-station project record]

The Mill Street station serves the area west of Grey Street, including Thornbury and Lora Bay. The town describes it as operating at capacity. Its $17.7 million construction contract was announced in August, with a detailed construction schedule still being finalized. The treatment plant's completion and this contract award are genuine progress, but they are not the same milestone. A development dependent on additional pumping capacity has a different exposure from one whose existing servicing is already adequate. [Mill Street pumping-station project record] [Mill Street construction award and financing update]

The archive points to a more useful way to divide the market

The retained capacity page already identifies a February 2025 study of interim solutions at Mill Street, intended to support development agreements in constrained areas. Read alongside the town's separate permit guide for additional residential units, it reveals why a town-wide housing forecast can mislead. A sewer-dependent project, a property using an approved interim arrangement and a home relying on private septic are not waiting for the same event. The permit guide requires septic construction information where municipal sewer is absent; the larger treatment plant does not remove that property's site requirements. [Municipal water and sewer capacity record] [Additional residential unit permit requirements] [Mill Street pumping-station project record]

Several prominent numbers on the older capacity page refer to September 2021. They should not be used to estimate today's remaining home capacity after the 2026 expansion. The useful new finding is the change in where the constraint matters: more treatment is available, while the current Mill Street project still concerns the ability to move wastewater to it. That shifts the relevant research from a municipality-wide capacity total to the servicing route and agreement attached to each development. [Municipal water and sewer capacity record] [Thornbury treatment expansion completion announcement] [Mill Street pumping-station project record]

Provincial funding brings a deadline, not a guaranteed opening

The provincial infrastructure programme is part of the local timing risk. The town's December 2025 project record describes a March 31, 2027 completion deadline for full funding eligibility. Its August 2026 release says the contractor's schedule is still to be finalized and identifies pressure from construction costs, slower development and changes in the timing of development-charge receipts. That combination deserves attention, although it does not establish that the deadline will be missed or that funding has been lost. [Mill Street pumping-station project record] [Mill Street construction award and financing update]

The forecast through the end of 2027 is that new supply in the Thornbury and Lora Bay area will arrive unevenly, with projects dependent on additional Mill Street capacity lagging otherwise comparable projects that already have adequate servicing or an accepted interim solution. The treatment expansion alone is unlikely to create a synchronized wave of competing listings. Confidence is low because individual allocations, interim approvals and construction schedules have not been assembled into a complete project-level inventory. [Municipal water and sewer capacity record] [Thornbury treatment expansion completion announcement] [Mill Street pumping-station project record] [Mill Street construction award and financing update]

The assumption is that additional pumping remains necessary for the affected projects and that developers still intend to build. National borrowing conditions can slow both groups: the Bank of Canada held its rate at 2.25% in September while noting higher longer-term yields since July. Early commissioning, broad approval of interim connections or weak demand across all project types would weaken the forecast. The decisive evidence will be servicing agreements followed by permits and completions, with each project assigned to its actual sewer catchment. [Bank of Canada September policy decision] [Municipal water and sewer capacity record] [Mill Street pumping-station project record] [Mill Street construction award and financing update]