The working group reviewed how the draft bylaw defines "new construction" and which activities trigger stormwater permitting requirements. Staff and members discussed aligning the new‑construction definition with the zoning bylaw (demolition or reconstruction exceeding 50% of the building shell) and expanding how impervious area is counted for permit triggers.

Key points:
- New-construction trigger: the draft references a zoning-based test that treats demolition of more than 50% of the building shell (exclusive of an attached single-story garage) as new construction. The group discussed the practical effect: a homeowner who removes more than half of the shell will likely be captured as a new construction project, even if a foundation remains.
- Dual triggers: the bylaw keeps two different triggers: (1) a building alteration trigger tied to a 25% change in the building footprint/shell, and (2) a site‑wide impervious cover trigger (increase by 25% or a post‑construction total above thresholds such as 4,000 sq. ft.). The group clarified that both triggers operate independently; a project could be captured by either test.
- Whole-property counting: unlike the prior approach that emphasized roof area, the draft requires applicants to count all impervious surfaces (roof, driveway, walks, sheds, patios) when determining whether the post‑construction impervious threshold is met. Members noted this will capture many projects that previously avoided review by focusing only on the roof footprint.
- Decks and imperviousness: members debated whether to treat decks as impervious by default and whether to define a deck as 50% impervious. Some argued decks change flow and should be counted; others suggested counting rules belong in the regulations for flexibility.

Why it matters: these changes broaden the number of projects that will require stormwater review and may change how homeowners and builders plan teardowns and renovations. The working group emphasized consistent public messaging explaining that the bylaw is not retroactive — it applies prospectively to projects after the bylaw/regulations are adopted — and that existing, approved as‑built systems remain lawful if they met rules at the time of construction.

Ending: Staff will add clarifying language and cross‑references to zoning and wetlands rules in the draft and place certain implementation details into the regulations rather than the bylaw itself.