Attachment N-6 <br />Page 2 of 5 <br />leaving 18' of protection space. But, it will have to be moved closer to the <br />trees for excavation of sewer, water, and eventually fire lane excavation, but <br />leave the protection fence in place as far from the tree trunks as possible, for <br />as long as possible during duration of construction. <br />2. As the fire lane is constructed and completed, it should be used for <br />construction activities as little asr possible. Use of the emergency fire lane <br />should be limited permanently. <br />3. Use a surface that allows moisture to penetrate. <br />4. Minimize cutting into the root system if possible by removing as little as 6" of <br />top soil prior to building the emergency access lane. <br />5. Maples are tolerant of root pruning. Therefore, on the tree side of the water <br />line trench, roots 1" and larger should be cut by hand by a certified arborist <br />as the trench is dug by rnachine. <br />6. When the sewer line trench is dug by machine, a certified arborist should be on <br />hand to cut roots as described above, between the. level of the bottom of the <br />water trench, and the bottom of the sewer trench. <br />7. When excavation for the fire lane has pushed the temporary protection fencing <br />completely to the trees, additional protection barriers such as beams and <br />plywood should be considered to protect the trunks. Mechanical damage such <br />as scratches, scrapes, and tears to the bark, must be avoided. Equally <br />important to protect are the structural roots near the trunk. If any of these are <br />exposed or disturbed within the drip line of the tree during excavation for the <br />fire lane, a certified arborist should be called on to provide instructions to <br />minimize damage to the support and vascular systems of the tree(s). <br />8. Following excavation for the fire lane, prior to application of aggregate <br />substrate, Vertical mulching should be considered. This is a process where <br />holes and fractures are created to increase air space for roots, especially small <br />feeder roots. This is accomplished by injecting high-pressure water or air <br />and physically auguring openings. In some cases, voids are filled with porous <br />material such as sand or gravel. <br />9. Whether or not #8 is used, the roots should be treated with a proprietary <br />source of mycorhiza selected and applied by a certified arborist prior to <br />application of the substrate for the fire lane. In addition, the root zone can <br />be treated topically with the growth regulator pacloorutrazol. <br />3. Mature 32" cottonwood tree just inside conservation zone, south of south parking <br />spaces: <br />Removal of cottonwood tree, highly recommended for obvious safety reasons. <br />A risk assessment can be performed. At first observation, the tree is at full maturity <br />and is frequently loosing limbs. If removal is allowed by government/municipality agencies <br />responsibility for the conservation zone, replacement trees will be recommended and <br />including those in the irrigation plan may be considered for at least the 3 to 5 years. <br />If removed, the cottonwood stump should be cut to within 2" of grade and the exposed <br />surface of the remainder should be cross-hatched with a chain saw with grooves at least 2" <br />deep and 1" apart. This should be done in a way that causes rain water to set in the grooves <br />and hasten stump decay. The exposed surface can be hidden by a covering of mulch. <br />