OP-ED: The MBTA Communities Law Part 2 – What It Is, What It Isn’t

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By Linda Scott
Watertown Resident

What the MBTA Law (MGL 40A Section 3A of the Zoning Act) is:

A zoning plan to address building multifamily housing in areas where there is public transportation.

What it is for Watertown:

A zoning plan for 1,701 housing units in the form of three family structures or more. These units must be non-exclusionary, meaning without any age restrictions, and suitable for families with children. Why 1,701? Because that’s about 10 percent of the housing we have right now.

Our minimum acreage requirement is 24 acres, however, that can be spread over several reasonably sized zones (four 6-acre zones, for instance). The minimum size for a zone is 5 acres. Currently, the Watertown Planning and Community Development Department has it all assigned to one spot, extending out from Watertown Square, using one transit stop, the Watertown Square Terminal bus at the Delta.

We are designated as an adjacent community, which means that we have flexibility where we put these zone(s), as long as half of the zone is a half a mile from transit. Why a half a mile? Because planners use that number as a “reasonable walk zone.”

It’s my understanding that even this has changed from the original concept. A “transit location” could be an active bus stop, not just a bus terminal. For instance, Watertown Square would be the terminal, but catching that bus at another active bus stop farther from Watertown Square would count. Other bus lines in Watertown count as well.

Now, let’s get into the weeds a bit. The law requires the zone have a density of 15 plus gross units per acre. Not every property in this zone has to conform to this. Some could be less dense, which means some would have to be much denser (packed closer together or built higher) to compensate for the smaller ones (Steve Magoon’s balloon analogy).

Let’s take Saltonstall Park as an example. Saltonstall Park is a little over 4 acres (4.2). No one is suggesting that we build there. This is just to help you visualize the situation. If we did build up the park to comply with the MBTA Law, we’d need to put 63 housing units on that property to equal 15 gross units per acre. Let’s pick another site. The City Hall is 3/4 acres. We’d have to put about 11 housing units there. So, in total, those 2 adjacent plots of land would have to have
74 housing units on them to meet this requirement of a density of 15 gross units per acre. This could be configured in different ways, but nothing smaller than a three-family building would be in compliance, so divide 74 by 3 = at least 24 triple-decker buildings.

Or, as Steve Magoon hinted at in the City Council meeting, a very large building could be built to accommodate all 74 plus of the housing units. There are in between options as well.

In the Arlington Department of Planning and Community Development’s video, they show you examples of what this might look like.

What it is not:

An affordable housing plan, although they encourage it. An attempt to wrangle every square inch that isn’t covered in Watertown and build on it.

In fact:

“Municipalities seeking to limit construction of multi-family housing might draw the districts to cover areas that are already densely developed with housing, so that redevelopment could not yield that many net new units. If the municipality draws the zoning densities close to — or even less than — existing densities, then probably the municipality will not see a lot of building in the new zoning envelope.

In this way, the requirements indirectly credit municipalities that already have multi-family housing in qualifying locations, although the guidelines also assign higher zoning capacity targets to the municipalities that already contain the most housing.”


So, let’s see what the Town of Arlington’s Department of Planning and Community Development has to say about this. Their Planning Department has been actively engaging with their residents on this topic since at least November 2022. Just keep in mind that their assigned number for housing units is 2,046 and ours is 1,701.

Their assigned acreage is 32 acres and ours is 24. The concepts, however, are the same. Roughly, the first 45 minutes are explanations of the law, and (good) questions from the community follow.

The sound is not stellar, but between the narrative, captions and the visuals, you’ll get the idea. This is an excellent teaching tool for those who want the big picture of what’s heading our way.


Tomorrow, Part 3, An assessment of multifamily units currently in Watertown Square.

3 thoughts on “OP-ED: The MBTA Communities Law Part 2 – What It Is, What It Isn’t

  1. Hi Linda, I read the guidelines posted on the Commonwealth’s website (https://www.mass.gov/doc/compliance-guidelines-for-multi-family-zoning-districts-under-section-3a-of-the-zoning-act/download), and I think there might be some errors in your post.

    1) As an adjacent community with less than 100 acres of developable station area (see table in Appendix 1, pg 6), Watertown is free to place the district where we see fit, but are encouraged to place in areas with access to transit or an existing downtown or village center (Section 8b, pg 13).

    2) While towns and cities are allowed to have multiple districts, at least one district must comprise at least half of the minimum zone acreage (Section 5a, pg 8, also pg 19 of the compliance model guide). For Watertown that means at least one district has to be at least 12 acres in size. In practice, that means the city can have at most 3 districts.

  2. and Watertown does not have the space…just look at the high school project, there was nowhere adequate to build a new building. And what little space there is, is Green space. What a conundrum!

  3. Hi Sam and Fred,

    I have some options that may help. They’re in Part 4. Charlie cut this part way back. You may have noticed that I can get wordy… But maybe we can approach this without having to settle for knee-jerk zoning. I’m guessing that Charlie will let me give some real numbers in this forum after part 4.

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