A Living Forest to Stop Sewage Flooding in Alewife Brook

Alewife Living Forest

Living Forest Infrastructure for a Cleaner Alewife Brook

When heavy rain hits Alewife Brook in Cambridge, Massachusetts, sewage-contaminated floodwaters spill onto public trails, into neighborhoods, and into wildlife habitat. The 5,000 people living in the Alewife Brook floodplain regularly experience what is reported as the worst raw-sewage flooding in Greater Boston.

During an October 2021 storm that brought nearly an inch of rain, six outlets discharged a combined 2.5 million gallons of sewage-contaminated overflow in just 45 minutes.

What Is Living Forest Infrastructure?

Alewife Brook needs conventional infrastructure. Can living infrastructure help too?

Can we engineer that familiar treatment system to support a healthy native forest at the same time?

In simple terms: a forested leach field—combining a familiar wastewater-treatment principle with ecological restoration.

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Engineering and living systems can work together. Can we also slow some of this water, clean it, and return it to the landscape?

The MWRA, Cambridge, and Somerville are accepting public comments. Urge them to evaluate a living-forest pilot as part of their plans to reduce the amount of sewage-contaminated stormwater entering Alewife Brook.

Submit a Comment

The roughly 60,000 square feet of mowed grass between Alewife Brook Parkway and the brook could potentially support about 25,000 native trees and shrubs representing a rich diversity of species, many valuable to pollinators.

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Could a Miyawaki Forest Be Part of the Solution?

The Miyawaki method establishes forests by planting a wide diversity of native trees and shrubs as young saplings very close together.

As the forest develops, roots, fungi, microbes, and surrounding soils develop together into an increasingly complex living system. For living forest infrastructure, this dense, diverse planting approach is one possibility worth exploring.

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This would be more than a forest. It would be a pilot in living infrastructure.

On the Cambridge side of the Alewife, between Route 2 and Mass Ave, there is more than 60,000 square feet of mowed grass. Cambridge, experienced with two Miyawaki forests (in Danehy Park and Greene-Rose Heritage Park), could put into practice what was learned, using about 25,000 saplings of a great diversity of native plants.

Rather than sending it all down the brook, a pilot system could divert a portion of the combined sewer overflow for treatment. After screening to remove sediment and floating debris, the water could be pumped to the upland, where it could pass through engineered biological filters—potentially including wood chips colonized by fungi and beneficial microbes and biochar designed to adsorb contaminants.

The water could then be distributed underground through a carefully engineered infiltration system beneath the forest. Much as in a conventional leach field, the soil itself would provide further treatment—but here the treatment zone would also support thousands of native trees and shrubs.

As water moved through the soil, plant roots, fungi, bacteria, and other soil organisms could provide additional biological processing. Trees would return some water to the atmosphere through transpiration, while creating more biomass above and below ground.

Alewife’s Living Forest would complement the proposed and much-needed 3-million-gallon storage pipe, which is now part of the public discussion. It would enhance conventional infrastructure when more than an inch and a half falls generating more than 3 million gallons of overflow.

As the forest matures, deeper roots into the clay beneath the soil and accumulating organic matter could further improve soil structure and infiltration capacity.

If successful, the benefits could extend well beyond water quality. A native forest could provide habitat for birds and pollinators, cool its surroundings, capture carbon, filter air pollution, soften traffic noise from Alewife Brook Parkway, and make the Alewife Greenway more beautiful and welcoming.

Cities across the country are searching for affordable, nature-based ways to manage stormwater in a changing climate. Alewife Brook offers an extraordinary place to test what happens when ecological restoration and conventional engineering are designed together rather than treated as separate worlds.

How You Can Help

Wanted: Greenway walkers, mushroom foragers, birders, gardeners, ratepayers, pollinator people, salamander crossing guards, small-mammal champions, and earthworm wranglers.

Join the mushroom foragers of the Boston Mycological Club and write a comment explaining why you would like Alewife Living Forest infrastructure. Whom else might you speak for?

Add your voice during the public comment period by completing our comment form here.

Then invite someone with a different reason for caring about the Alewife to add their voice.

This forest can help keep sewage-contaminated water out of Alewife Brook while making its Greenway cleaner, healthier and more resilient. Planting thousands of native saplings would be an investment not just in today’s infrastructure, but in a forest that could grow and mature for generations.