APPENDICES - Laserfiche WebLink

et al., 2008). Therefore, the goal of fuel treatment is not to remove all trees or vegetation but to minimize the potential for ignitions, crown fires, and extreme fire behavior by reducing fuel loads and altering the retained vegetation structure, composition, and spacing (horizontal and vertical). These recommendations should be conducted for all trees within 100 feet of the structure, and those that overhang are within 20 feet of a road or driveway. The Livermore-Pleasanton Fire Department has published a vegetation management standard that details how to properly maintain other types of vegetation, such as grass, brush, and other types of vegetation (LPFD 2021). SubAppendix B contains the LPFD’s Vegetation Management Standard. Tree maintenance recommendations and vegetation management to meet defensible space requirements and reduce wildfire risk generally do not change depending on who performs the work or where the tree is located. In the WUI areas of the City, trees within 100 feet of a building are recommended to be maintained to meet the recommendations in section 1.3 and appendices D, E, and F of the UFMP and the guidelines published by the Livermore-Pleasanton Fire Department. The two exceptions to this rule are 1.) trees along public roads should be maintained so that vehicles can travel unobstructed, and 2.) vegetation clearance around high-voltage electrical equipment is generally the responsibility of the electric utility, which is PG&E in the City. Tree Arrangement Fire spreads horizontally (from shrub to shrub or treetop to treetop) and vertically (from understory vegetation to tree). A more significant fire hazard exists where the spacing between trees and between shrubs and lower branches is close enough for the fire to preheat vegetation and ignite across the gap, either horizontally or vertically. If a ground fire transitions into a tree canopy fire, it will quickly spread from one tree to closely adjacent trees. The primary goal of tree arrangement is to break up the continuity of the flammable materials in the tree canopy through proper tree spacing. To accomplish this, the following recommendations are provided in the LPFD vegetation management standard (Livermore-Pleasanton Fire Department, 2021): • For slopes less than 20 percent, trim or space trees to provide 10 feet of space between the tips of tree limbs. Trees should be limited to groupings of 2-3 trees, with each grouping separated horizontally as described herein. • Increase spacing to 20 feet for slopes that are 20 to 40 percent. • For steep slopes over 40 percent, 30 feet of spacing is needed. When planting individual or small groupings of trees, allow for future growth by spacing them 20 to 30 feet apart. In addition, other ladder fuels, such as shrubs, should be removed around the base of trees. Pruning Practices Lack of attention to tree crowns of any species can result in trees accumulating dead twigs, leaves, and branches, regardless of whether they are categorized as “fire resistant.” This buildup of dead fuels in the canopy can easily result in trees becoming very flammable. Tree pruning recommendations focus on preventing fire from spreading into a tree canopy. To reduce the fire-spreading potential of trees taller than 18 feet, prune the lower limbs to a minimum height of 6 feet. If the tree is shorter than 18 feet, all branches and foliage should be removed from the lowest 1/3 of the tree. Trees near homes or buildings should receive additional attention, and branches that overhang the roof or come within 10 feet of the chimney should be trimmed or removed (Livermore-Pleasanton Fire Department, 2021). Additional attention should be given to trees that overhang public and private roads by trimming trees to provide 14 feet of vertical clearance above the roadway for emergency vehicle access (CFC, 2022). Special Pruning Standards for Palms – Palm trees are significantly different from broadleaf and conifer trees in their pruning requirements. Palm trees lack branches or leaves originating from buds on the trunk; instead, new fronds grow from a central point at the top of the tree (the heart). All palm tree species produce new fronds annually, 17