We cut concrete for tree basins with two factors in mind: Healthy Trees: Larger cuts allow for more space for trees to grow, allow more water to drain off the sidewalk into the tree basin (more water for the tree, less water for PUC to treat, less cost to SF taxpayers, less untreated waste getting flushed into the bay/ocean during storm events), allows for more oxygen exchange with the atmosphere. The Safest Sidewalk: The safest sidewalk is a flat, undamaged sidewalk. Concrete damage from street trees is largely correlated to the size of the tree basin. By giving the tree a larger cutout, we reduce the likelihood of that tree damaging or uplifting the sidewalk, and thus ensure a smooth, flat, unhindered path of travel for pedestrians. Our basin sizes are approved by Public Works and follow all relevant city code & ADA requirements for path of travel.