Staff outline "sustainable development" density bonus and civic‑space rules in recode presentation

City planning staff returned to the committee June 16 to continue a series of recode briefings and to walk members through a proposed "sustainable development" density factor intended to incentivize higher‑order site design and on‑site green infrastructure.

Sam Durfee, deputy planning manager, described three comparative density paths in a redevelopment context: the base density factor, an inclusionary‑zoning (IZ) density bonus that yields the largest unit count when developers provide affordable units, and a middle option — the sustainable development density factor — that awards a smaller bonus for meeting a menu of green‑design criteria. Using a hypothetical six‑story building of roughly 140,000 square feet, Durfee contrasted density factors noted in the presentation and showed how the sustainable development option would increase unit counts modestly compared with the base case while requiring green‑score actions such as enhanced stormwater practice, vegetated roofs, heat‑island reduction and EV‑ready parking.

"We're trying to capture stuff on‑site," Durfee said of rain gardens and bio‑retention, and he emphasized that stormwater and landscaping measures would be reflected in site‑plan stormwater reports and specific green‑infrastructure detail sheets the city would approve.

Committee members sought practical clarifications. Alderman Patricia Klee asked whether green features would be mandatory and how the city would ensure they were maintained over time; Durfee answered that maintenance for the life of the development is a requirement and that landscaping is enforced as part of approved site plans. On rain gardens, Alderman James Revan asked whether they require aeration; Durfee said they are designed to infiltrate and generally do not hold standing water.

Durfee also presented civic‑space concepts for large redevelopment overlays — ranging from pocket parks to programmed public amenities or physical connections to existing parks such as Mine Falls. In a case study the presentation identified roughly 18% of a redevelopment site as civic space; members raised concerns about long‑term maintenance costs and who would own and maintain those spaces (city DPW, an HOA, or the developer). Durfee said the city would coordinate thresholds and ownership models with DPW and that site‑plan conditions would require delivery of civic‑space improvements prior to final approvals.

On neighborhood types and scale, Durfee defended a roughly 20‑acre minimum threshold for redevelopment overlays as the area needed to assemble diverse building types and create coherent new neighborhoods. Several members said context matters — what works on Amherst Street or in the downtown will differ from suburban neighborhoods — and staff said they are considering blanket waivers (for example, 5–20%) during an initial implementation period to allow adjustments after real applications test the standards.

Durfee closed with recommended accessory‑structure rules (sheds) keyed to district context: in rural‑scale districts an accessory structure could be up to 50% of the principal building footprint or 600 sq. ft., and smaller caps would apply in denser districts; building permits would still be required though many such structures would not need planning‑board review if setbacks and lot‑coverage standards are met.

Next steps: staff will continue refining IZ and related provisions for future committee discussion and will bring additional specifics on administration, thresholds and DPW coordination before the code advances.