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Preliminary Arborist Report 536 St. John Street, Pleasanton June 20, 2016 Page 5 • Structural integrity Trees with significant amounts of wood decay and other structural defects that cannot be corrected are likely to fail. Such trees should not be preserved in areas where damage to people or property is likely. Species response There is a wide variation in the response of individual species to construction impacts and changes in the environment. In general, coast live oaks are relatively tolerant of construction impacts and site changes while English walnut is intolerant of site disturbance. • Tree age and longevity Old trees, while having significant emotional and aesthetic appeal, have limited physiological capacity to adjust to an altered environment. Young trees are better able to generate new tissue and respond to change. • Invasiveness Species that spread across a site and displace desired vegetation are not always appropriate for retention. This is particularly true when indigenous species are displaced. The California Invasive Plant Inventory Database (http://www.cal- ipc.ora /paf /) lists species identified as being invasive. Pleasanton is part of the Central West Floristic Province. Black locust has a limited invasiveness rating. Each tree was rated for suitability for preservation based upon its age, health, structural condition and ability to safely coexist within a development environment. Table 2 provides a summary of suitability ratings. Suitability ratings for individual trees are provided in the Tree Assessment (see Exhibits). We consider trees with high suitability for preservation to be the best candidates for preservation. We do not recommend retention of trees with low suitability for preservation in areas where people or property will be present. Retention of trees with moderate suitability for preservation depends upon the intensity of proposed site changes. Table 2: Tree suitability for preservation 536 St. John Street, Pleasanton High These are trees with good health and structural stability that have the potential for longevity at the site. Seven trees had high suitability for preservation. Moderate Trees in this category have fair health and /or structural defects that may be abated with treatment. These trees require more intense management and monitoring, and may have shorter life -spans than those in the "high" category. Three trees had moderate suitability for preservation. Low Trees in this category are in poor health or have significant defects in structure that cannot be abated with treatment. These trees can be expected to decline regardless of management. The species or individual tree may possess either characteristics that are undesirable in landscape settings or be unsuited for use areas. Three trees had low suitability for preservation.