SR 06:247 - Laserfiche WebLink

trees are considered "Heritage trees" by virtue of their trunk circumference, 62" com- bined and 70" combined, respectively, and appear to be vigorous and in good health with no evidence of disease, insect infestation, decline, or structural infirmity. Typically, Prunus species tolerate construction impacts moderately well, whereas Jug/ans species do not tolerate construction impacts. Both species typically produce a shallow, radial root system that is not likely to extend deeper than about 3 to 4 feet. The Landscape Ar- chitect stated that the condition of both trees makes them good candidates for preserva- tion, however, a significant portion of their root systems may be damaged or destroyed should excavation for the proposed structure take place. The general "rule of thumb" is to prohibit changes of grade or trenching to occur within the drip line of trees to be pre- served. On Mr. Finlay Boag's property (4558 Second Street), the subject tree is a multi-trunked Locust tree (Robinia species) that is approximately 5 feet from the side property line fence (adjacent to the Boyce lot). The trunks have a total combined circumference of 60" and the tree is more than 35' in height, thereby meeting the classification for a "Heritage Tree." Staff notes that the applicant has previously received a grading permit and has excavated within 23 feet of the rear property line. The trees of concern, however, are located along the rear 18 feet of the rear property line. The City's Landscape Architect indicated that development impacts could be mitigated by such measures as hand trenching the garage's foundation, requiring a greater setback from the property-line for the proposed structure, utilizing standard arbor techniques for cutting roots (larger than 1" diameter) when they are encountered, requiring that cut slopes be quickly backfilled (within 48 hours) once excavated - or else covered with burlap and wetted regularly, in order to avoid root desic- cation, and/or significantly pruning the top portion of the Heritage Black Walnut to re- duce the "sail effect," and the possibility of its overturning due to the loss of support roots. The Landscape Architect determined that due to the proximity of the proposed construc- tion to the neighboring heritage trees and the possible dlunage to the root systems, a Con- sulting Arborist's should be retained to evaluate the construction impacts to the trees and to recommend possible mitigations for those impacts. The applicant has hired one of the arborists on the City's list of approved consulting arborist to evaluate the condition of the neighboring trees and their estimated worth, and to recommend mitigation measures. As ofthe printing of this staff report, the consulting arborist's tree report was not yet ready. Staff has, however, conditioned this project so that all recommended mitigation measures of the arborist report are followed. Pleasanton Municipal Code Design Criteria Per Chapter 18.20 of the Pleasanton Municipal Code, the Planning Commission must de- termine that the proposed project meets the outlined design criteria to approve the pro- posal. The design review criteria for this project and staff analysis follow. Item 6.b. PADR-1338/PV-13/ Page 9 of 14 September 27, 2006