Zoning has always been a reflection of the people’s desire to control how their environment looks, which is another way of saying it’s an expression of our city’s values. One value many of us share is to have a local environment that is greener and more environmentally friendly. That is reflected in our current regulations that allow a maximum of 65% impermeable surface for newly built homes in residential districts. The remaining 35% of the lot must be permeable, which often means green space. That reduces the urban heat island effect and allows rain to soak into the ground, reducing flooding.
But our current built environment is a reflection of past values. A majority of the city was built pre-zoning, and the last bits that were built under pro-car zoning. Both have resulted in a lot of impermeable surfaces on almost every residential parcel in Somerville. For example of how zoning encouraged construction, we can look at 16 Summit Avenue. It holds a four-bedroom house with seven parking spaces and a small back yard:
16 Summit Ave circa 2025
If it were redeveloped, more of the space would almost certainly be devoted to homes and open space, and a lot less of it to car storage.
The city has conducted a study of impervious space, and using their data, we estimate that the average residential parcel is 73% impermeable. In other words, if a residential parcel gets redeveloped under our current regulations, the new building will almost certainly have a lot more permeable space.
115 Thurston St. is a perfect example. A few years ago, it held a triple-decker and a parking lot, for a total of 68% impervious space:
115 Thurston St circa 2020. Source: Google Maps
Now, it’s got a single building that covers 55% of the lot, with a large open yard in the rear. Overall, it is a significantly greener and more permeable piece of land than before, despite retaining parking spaces and adding more homes.
115 Thurston St circa 2025
In Somerville, we don’t have to give up dense housing to get green space. Rebuilding our lots can get us both.
P.S. If you own your parking spot or can get your property owner(s) to agree, consider converting it to a green space. The fine folks at Depave the Way can help. To learn more about their program and sign up, visit greenopensomerville.org/depave.