What's Happening in Lexington Center? Silva Cell system and healthy tree roots
If you’ve been through Lexington Center lately, you may have wondered about the extensive excavation that’s been happening in the sidewalk area on the north side of Massachusetts Avenue and puzzled over the rows of black pedestals being installed.
Silva Cell module diagram
Here’s the sequence, illustrated by the accompanying photos taken over the past month:
1. The sidewalk area where the trees are going to be planted is excavated down to a depth of about four feet, and the base of the excavation is lined with geotextile fabric and compacted gravel.
2. The base and pedestals of the Silva Cells are installed.
3. Good soil is poured into the spaces between the pedestals and is compacted lightly by foot. Piping to provide air and drip irrigation to the tree roots is installed. Once the soil is in place, caps are put on the pedestals to support sidewalk construction.
4. Another layer of geotextile fabric is laid on top before the sidewalk is constructed.
5. Then, construction of the sidewalk – gravel base, concrete foundation, layer of sand, and bricks – can begin, essentially suspended over the lightly compacted soil within the Silva Cells.
6. The result: a streetscape with a much healthier environment for trees (and all the environmental benefits they provide) while also providing a smooth, attractive brick sidewalk that is more accessible and safer for all users.