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RARKIREE.MEM Page 1 MEMORANDUM DATE: October 17, 1994 TO: Bob Hammitt CC: Johnny Medlin, Dick Morgan, Adrian Stansfield FROM: Jan Staszewski, Urban Forester SUBJECT: Health and Structural Integrity Assessment of the Incense Cedars In the South West Park Block General Description The Downtown Crew asked the Urban Forester to examine vandalized trees within the southwest Park Block. The damage by vandalism was superficial, however some Incense Cedars were in a state of decline and others had large open cavities. Staff made the decision to do a hazard assessment on all the Incense Cedars. The following assessment includes measures to abate hazards and recommendation to mitigate the loss of Park Block trees. Assessment There are sixteen Incense Cedars within this area that comprises all the larger trees within the southwest Park Block. The Incense Cedars are range in height from 60' to 100' tall and from 23" dbh to 38" dbh in. Most of the trees are within tree wells that were constructed around the mature trees when the Park Blk. was developed. There is no visible scarring to indicate that any of the trees were damaged at the time of construction. Though the site is used intensely on a regular bases, there does not appear to be any major impact on the trees or the ground around them. After observing a fungal conk on two of the incense cedars and large open cavities within two other incense cedars a detailed investigation was initiated. Staff found that all the incense cedars within this Park Block had multiple leaders in the top 15' to 30' feet. The multiple leaders were most likely caused by either high winds or snow loading breaking off the original leader. The multiple leaders contribute to structural instability at the old break point, that can result in failure of one or more of the new leaders. The presence of the conk on the two trees indicates the presence of the wood decaying fungus Oligoporus amarus. This fungal disease is commonly found in mature incense cedars or younger trees that have been injured (e.g., broken top). This fungus causes severe decay of the heartwood through the entire length of the trunk. The disease enters the trunk through any injury. Initially the disease causes pencil sized columns of decay through out the heartwood. As the disease progresses these columns of decay coalesce to form ever increasing areas of decay. Any other defects (e.g., open cavity, old snow break, and severe lean) in the tree will further reduce the tree's structural integrity. A core sampling of the incense cedars was necessary to determine the presence and extend of O. amarus within each tree, since the decay may not have any outward signs or symptoms. Core samples indicate there is O. amarus within all incense cedars. However, the disease is less advanced as that found in the four trees with the either conk or the large open cavities. To determine the relative hazard these trees pose the "Evaluation of Hazard Trees In Urban Areas" by Matheny & Clark was used. The hazard rating took into account the failure potential, size of part most likely to fail, and target rating of where the tree part could land. The evaluations found four high hazard trees. The two trees with conk and the two trees with an open cavity were found to be high hazard trees. These four trees have rating of either 8 or 9, within a hazard rating scale of 1 to 9, with 9 being the most hazardous. Recommendations Due to the extreme hazard potential caused by extensive internal decay the four incense cedars with hazard ratings of 8 or 9 should be removed before winter. The remaining trees should be checked yearly to observe the progress of the decay. However, there is one incense cedar that will most likely be removed within two years due to advancing decay. In addition, staff anticipates that the remaining trees will need to be removed over the next fifteen to twenty years as the decay slowing progress through their trunk's. There is no cure or preventative measures to stem the advancement of the decay. To provide for public education regarding the need for removal, each tree will be posted with a removal notice for at least one week prior to removal. The notice will state the reason for the removal, the date of removal, and the date and species of replanting. In addition, a public service announcement will be made at the time of the posting to reach others in the community that may not visit the area during the posting period. Staff plans to replant with Incense Cedar to maintain the integrity of the original landscape design. Staff believes that the unique set of circumstances that brought about the early demise of these trees should not be a deterrent from replanting the trees. In general, the trees have a long life, averaging over 500