Agenda - Parks and Recreation Commission - 10/14/1993

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that must be cl~vercd with soil close to the trunk. I hw,,ever, as a general rude it is best to remove trees that would be buried by 24 roches or more of fill around thc base. Cutting the soil away from a t~ue removes vital {coder roots, eliminates nutrient-rich ~opsoil, and often lowers the water table. Damage caused by shallow cuts (less lhan two inches) at least three [eet away from thc base of the tree may be miMmal, but still can bca shock to a treds vigor. If pos- siblc, avoid making thc cut durh~g hot, ~rv wcathcu water the tree (undis- turbed portions) before and after soil removal; and allow only hand digging inside thc PRZ. A shallow laver of mulch (pine nacdles, wood c~ips, or coarsely chopped twigs and bark) and dean root cuts will help wound~ closure and re~rowth. Deeper cuts within the root zone will requir~ Figure 7. If you change the grade within the root zone, use retaining wall to keep os much of the or~inal grade as possible. ~) backfilling; b) cut ting. Soil removed beyond re taining wall construction of a retainin~ wall closer than the limit of the PRZ (Figure 7b). EXCA VA TION As much as 4(1 percent of a tree's root system could be cut during thc installation of a nearby utilily line. This reduces water and nutrient uptake, and may compromise the stability of the tree. If it is not possible to relocate the utility line outside the tree's PRZ, you can reduce root damage by as much as 25 percent bv tunneling under the tree's root system (Figure 8). When digging a trench near a tree, begin tunneling when you encounter roots larger than one inch in diameter. Trenchin. EtLfor building fot:nda- tions also poses a danger to nearby trees. Although not often used in 7 c~. Backfilling behind retaining wall Trenching roots. Figure 8. Protect roots (rom damage when laying utility lines by tunneling rather than ~renching. Minnesota, posts, pilings or l-beams sometimes can be substituted for foundation walls and footers on homes (Figure 9). Drilling single holes as opposed to cutting deep trenches saves man}, critical roots. For all digging operations, insist that exposed roots be cut cleanly to promote quick wound closure and regeneration. Vibratory plows, chain trenchers, and hand tools do a better job at this than bulldozers and back- Figure 9, You can minimize damage to trees near foundations by using posts, pillars, or I-beams rather than foundation walls.