With construction beginning on the first of four blocks of Bell Street Park (between 1st and 2nd Avenues), one of the most dramatic changes to date has been the removal of the existing hedge maple (Acer campestre) trees. The decision to remove the existing trees on Bell Street was given a great deal of thought, taking into consideration safety (i.e. eyes on the street), ambient light, utility conflicts, location of the trees in relation to the existing buildings and the proposed street and sidewalk alignment, as well as tree health and life expectancy. While we could have worked around some of the trees through construction, the long-term damage would have limited their overall lifespan and would have conflicted with other community desires like an enlarged pedestrian realm and a greater diversity of tree species.
That said, we know that trees in the urban setting provide many benefits including wildlife habitat, traffic calming, shade, stormwater management and pollution removal. With urban trees in the right-of-way—especially in this case since Bell Street is a major utility corridor—it is a challenge to locate trees so that they will have enough soil volume and adequate clearance from utilities to ensure their long-term success.
For Bell Street Park, the team initially looked at Silva Cells—a system that we used at Winslow Way to suspend the pavement around the tree pits to provide additional uncompacted soil volumes—for the large trees located in the smaller planting beds. In addition to providing uncompacted soil for the trees, the soil in the Silva Cells can also help to intercept and manage stormwater runoff. Due to budget constraints and concerns by Seattle Public Utilities about the placement of Silva Cells around existing utilities, the project instead specified a structural soil mix, CU-Structural Soil, to support surrounding pavements while providing increased rooting area for trees beyond the planters.
In just a few short months, Bell Street Park will be home to a diverse mix of large and small deciduous trees--tulip poplars, tupelos, amelanchier and a variety of colorful maples--as well as a number of shore pines to provide evergreen interest and performance. We look forward to Bell Street becoming a great street park with a generous tree canopy for generations to come!