20.770.110 Specimen Tree Evaluation.
Specimen trees, for density calculation, shall be evaluated in accordance with the following criteria:
The specimen tree value shall be determined by multiplying the average of the size, location and condition values times the standard tree density of that tree found in Table 20.770.080-1; (e.g., if the standard tree density is 7 units); the size value (70% of state champion) is 3.0; the location (at least 75% visible) value is 2; the condition value is 1; then the Tree Specimen Value formula is (3+2+1)/3} x 7 = 14.0.
A. Size. Size shall be determined using the methodology developed by the American Forestry Association for measuring champion trees. This methodology, as adopted by the Washington Big Tree Program, is described in detail in the current edition of the following publication: Washington Big Tree Program, as published by College of Forest Resources, University of Washington. The size value for specimen tree evaluation shall be the percentage obtained by dividing the point value of the subject tree by the value of the state champion of the species then multiplied by four (4); e.g., Subject tree = 200 size points / 350 state champion tree points = 57% x 4 = 2.85).
1. Trunk Circumference. The circumference of the trunk shall be measured in inches at Breast Height (4.5 feet above the ground). If the circumference is distorted by low branching, etc., at Breast Height, the circumference shall be measured at the smallest reading obtainable at that point.
2. Tree Height. The height shall be measured in feet using standard forestry mensuration equipment (i.e., clinometer, etc.).
3. Average Crown Spread. The Average Crown Spread shall be measured in feet. The Average Crown Spread is the average of the spread of the crown at its widest and narrowest points.
4. Size Calculation. One point shall be assigned for every inch in circumference, each foot in height, and every 4’ in crown spread.
B. Location. Four possible location values, based upon the visibility of the tree from the public right-of-way or other publicly accessible areas of the property include:
1. 100% visible and prominent in the landscape = 3 points.
2. At least 75% visible = 2 points.
3. Not less than 50% visible = 1 point.
4. Not visible = 0 points.
C. Condition. The condition class of a tree shall be determined using the methodology described in the latest edition of International Society of Arboriculture’s Guide For Plant Appraisal.
1. Excellent Condition = 2 points.
2. Good Condition = 1 point.
3. Fair Condition = 0 points. (Ord. M-3643, 2004)