Stormwater Forum and Discussion - Feb 19th, 2019

Before the meeting got started, I asked a question inspired by one the proposed zoning bylaws changes. Our bylaws require certain amounts of open space. You can satisfy some of these requirements with a balcony or a roof, provided it's no more than ten feet above the lowest inhabited floor. One of this year's warrant articles proposes to remove the ten-foot restriction. I asked Wayne Chouinard "If there were something in our bylaws to incentivize roof gardens, could that help with our MS-4 permitting". Wayne wasn't sure, but felt that any such roof garden would have to be constructed to some set of standards. It's like installing pervious pavement for stormwater mitigation -- there has to be a design, and supporting evidence that pervious pavement will work as intended. That said, rooftop plantings that contain runoff would certainly help reduce stormwater emissions.

Wayne has been looking at floating wetlands. It's essentially a floating structure that holds plants. The plants can provide both habitat and water purification.

Now, on to the meeting proper.

EPA and MassDEP are collaborating with Arlington and Winchester on an effort to reduce phosphorus runoff into the Mystic River Watershed. We're working with state and federal agencies, and getting technical assistance from universities and private firms. The next meeting will focus on stormwater toolkits, and ways to encourage better stormwater management.

MyRWA has an upper Mystic storm mater management working group. The group would like to apply for a municipal vulnerability preparedness planning grant, preferably a multi-community one. They may be able to build off work that Cambridge has done to model the Mystic River Watershed. There's a group of upper mystic communities, which includes Arlington, Lexington, Woburn, Cambridge, and (possibly) Burlington. Medford and Somerville are part of the lower Mystic watershed group.

Emily Sullivan talks about hazard mitigation plans. Are towns considering regional mitigations as part of their local mitigation plans? Not yet, but it's something we'd like to look at, particularly where we can talk about things on a watershed level.

We've hired MAPC to help the town with developing a hazard mitigation process. This will focus on a set of predefined hazards. Hazard planning is not as community-specific as an MVP process.

Wayne and Emily provide updates on town projects. We've recently completed the installation of a raingarden in East Arlington (on Egerton Road, I think). We'll consider another raingarden installation later this year.

We're considering adding side infiltration basins near one of the Mystic River outflows. That should help with low-flow event infiltration.

Lori Kennedy talked about Philadelphia tree trenches. These are rather cool -- kind of like digging a trench, building a swale, and then planting trees on top. They provide stormwater storage capacity, and a water source for trees. http://www.phillywatersheds.org/what_were_doing/green_infrastructure/tools/stormwater_tree_trench has a diagram. These were very successful in a recent project in Boston, and Arlington should consider using the technique.