Rights-of-way have limited space, but we try to fit a lot into them: streets, sidewalks, overhead and underground utilities, as well as trees and other vegetation. Conflicts can arise between uses, notably trees and sidewalks. SDOT Urban Forestry works closely with Street Maintenance, Capital Projects, and private property owners to facilitate fixing sidewalks while preserving trees wherever possible. Innovative solutions for tree preservation include expanded tree pits and planting strips, rerouting sidewalks, ramping or bridging over tree roots, temporary shims and root pruning.
While expanding planting areas and ramping over roots, we must conform to sidewalk widths and slopes required by the Americans with Disabilities Act. Root pruning consists of cutting shallow roots in order to make room for a new sidewalk. Roots must be cut cleanly, ideally where other roots branch off to redirect growth. Pruning roots is challenging, as it’s necessary to remove enough roots to install a new sidewalk that will last, while leaving roots to sustain and support the tree.
There are certainly times when trees can’t be saved. When the available planting area is too narrow, the safety of a tree would be compromised by root pruning, or a tree is in poor condition regardless of sidewalk repair, removal and replacement is the only option. Despite all the challenges of accommodating trees and sidewalks, Arboriculturist Lou Stubecki, Urban Forestry’s lead on tree-sidewalk issues has an impressive record of saving trees. In 2010, of the 259 trees that had sidewalk repaired next to them, 191 were saved with a total appraised value of $1,645,530 and 68 trees had to be removed with a total appraised value of $252,630. When replacing trees or planting new areas, we choose trees of an appropriate size for the width of the planting strip that will not conflict with other infrastructure.