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Task force hears staff explanation of tree‑mitigation calculation change (ACI) and its effect
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Summary
Staff illustrated how switching to an ACI (aggregate caliper inches) calculation and removing a single‑family exemption changes mitigation totals, saying the aim is to encourage on‑site tree retention. Task force requested follow‑up materials and asked how the tree bank and rookeries protections would work.
Planning staff presented examples comparing the current mitigation formula (a divisible‑by‑900 method referenced in the packet) to an ACI (aggregate caliper inches) approach. Using a previously approved development as an example, staff said the ACI method produced 160 total mitigation inches while the older calculation produced 774 inches for the same site when the single‑family exemption was removed.
Staff framed the ACI approach as site‑specific, measuring caliper inches from six inches up, and argued that higher on‑site mitigation requirements under the older method can incentivize off‑site mitigation rather than canopy retention. Task force members asked for additional written guidance in the packet, and a public speaker suggested researching tree‑bank programs used elsewhere (including an oak tree bank) and adding strict guidelines if the town adopts a tree bank.
Why it matters: The calculation method affects how many replacement inches are required after tree removal and so can materially change developer costs and the amount of canopy preserved on site. Task force members also requested clearer rules about protections in high‑value environmental areas and rookeries.
Next steps: Staff will include the referenced code sections, best practices, and any comparative calculations in follow‑up materials; the packet already contains attachment 2 (Q&A) and the wetland and tree ordinance sections for review.
