New rules in Winchester address loss of green space

With a history of flooding issues, an increase in new, large homes that level and pave over large swaths of land, and the issuance of new federal stormwater rules, Winchester Town Meeting in May approved new minimum green space requirements and hardscape caps for future residential development.

Residential zones now have a 35 percent minimum green space requirement, and a 35 percent maximum hardscape limit applies to all residential zones except for one.

In the past six to seven years, the town has seen an uptick in tree removal and loss of green space when large houses are built, according to Town Planner Brian Szekely, primarily because the town’s zoning bylaws only defined open space as any area not covered by a building.

The bylaws capped building sizes at 30 percent of the lot, but the lack of a specific open space definition made the remaining 70 percent of a lot open to anything – including being paved over, Szekely said.

“In our RG district – a small zoned district and the only one that allows two-family homes – you’d see large two-family homes, with two two-car garages, and the only way to swing into these garages was to pave everything,” Szekely said. “That was one major problem we were seeing.”

Winchester examined greenscape and hardscape requirements in Reading, Weston, Wellesley and Belmont, some of which require larger open space and smaller buildable lot percentages.

A rough calculation based on an average, flat 10,000-square-foot lot with 30 percent building coverage, taking into consideration how much greenspace is needed to accommodate a “run-of-the-mill, two-year storm,” was used to develop the new requirements, Szekely said.

The town – called “Waterfield” before “Winchester,” Szekely said – has spent tens of millions of dollars in recent years on flood mitigation efforts.

Town Engineer Beth Rudolph pointed to the Aberjona River, which ultimately feeds into the Mystic Lakes and River, as a source of many of the flooding problems, which she said were at their worst in the mid-1990s but have a long history before then.

Winchester has been working since the 1990s to implement a flood mitigation plan approved by the Massachusetts Environmental Policy Act Office and is now in the process of implementing projects included in the plan, on top of several previous projects, Rudolph said.

“The more that we can do to reduce impervious area in the town and keep any stormwater runoff on private property, rather than having to go into the town system, is obviously a benefit in terms of flooding projects, as we move into the new phase of the MS4 permit cycle,” she said.