Healthy trees can minimize surface erosion and stabilize soils. During prolonged periods of heavy rain, soil properties on steep slopes and other areas can change to such a degree that even healthy trees can uproot. Trees may also be part of larger slides which affect all or portions of the soil the tree has depended upon for its stability. When SDOT Urban Forestry is called to assist in the investigation and clean up of slides that involve trees, several conditions must be considered and addressed before clean up can begin. Often slides present trees in various conditions; some have completely fallen and others have exposed roots and may be leaning precipitously. The real challenge is determining which trees around the edges of the slide remain stable. This requires careful consideration by arborists, geotechnical experts, and safety managers to ensure that the site is safe for clean-up activities as well as the public.
Once these important decisions are made and the site is determined safe for employees, Urban Forestry and Street Maintenance crews coordinate debris removal and traffic control. Urban Forestry utilizes ropes, pulleys, hydraulic winches, aerial lifts, chainsaws, climbers and ground personnel to remove fallen and leaning trees. Further work usually involves moving the tree debris down-slope so that it is accessible to heavy equipment. The Safety Office helps maintain communication between teams and monitors site conditions.