Stormwater Tree Trenches

1. Project Description:

The City received a grant to support green infrastructure allowing us to install 15 Stormwater Tree Trenches within the City of Watertown. The grant will cover the cost of excavation, installation of a crushed stone base, perforating the pipe, back filling, connection to either an existing or a new catch basin & loam and seed for each tree trench unit.

Stormwater tree trenches are designed to reduce & treat stormwater runoff & recharge groundwater. This will allow the City to reduce phosphorus loading to the Charles River by filtering & infiltrating runoff. It also supports the City’s efforts and goals of its Stormwater Management Plan under the EPA’S Municipal Separate Storm Water System permit program as well as supports the City’s municipal vulnerability program.

2. Taxpayer Benefits:

Green infrastructure mimics natural processes to capture, infiltrate, and treat rainfall and stormwater runoff which, if not properly treated, can carry pollutants into waterbodies and be harmful to public health and safety. Tree trenches remove pollutants such as phosphorus before water is discharged into the Charles River.

Precipitation events are becoming increasingly intense due to climate change & the stormwater infrastructure designed decades ago is now undersized which can cause stormwater flooding. Flooding can also occur in areas with high amounts of impervious surfaces. Tree trenches enhance groundwater recharge in highly paved neighborhoods.

Urban heat islands occur when natural land cover is replaced with dense concentrations of pavement. Stormwater tree trenches improves air quality as trees absorb pollutants such as nitrogen dioxide and sulfur dioxide and produce oxygen. Trees also absorb carbon dioxide, helping to sequester climate-warming pollutants and lessen Watertown’s contribution to global climate change.

See the presentation Greening the Streets of Watertown - Edenfield Avenue (PDF)

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The image of a tree trench is from: