AgdaPkt 2006-02-27 - Laserfiche WebLink

Browse Search

6.1 C.1 Page 9 movement was attached to the trunk of the tree about eighteen inches off the ground. The test results were inconclusive. The pull force was measured and recorded. There was no recorded incremental movement from the inclinometer (incremental movement) instrument. Staff discovered the problems that occurred with the data measurement process design. The use of synthetic rope used for the previous pull test creates stretch in the rope. While this causes the tree canopy to move similar to a storm wind loading for the previous observations, it didn't work well for the pull measuring device. The use of a vehicle to generate the pull does not allow for controlled incremental changes in pull force. The results were that as different pull forces were applied, the rope stretched and the force measured initially decreased. Staff concluded that there is measurable data that can be derived by further improving the test procedures. At the same time, staff observed the base of the tree following the previous pull testing observations. Some minor movement was noticed as previously, which was the basis for the reason to remove the tree, but it may not have been significant along the trunk where the instrument was attached. Staff will experiment with placement of the incremental movement measuring instrument to find the most advantageous location. Next Steps The next tree stability testing will utilize a web sling choker around the tree to minimize both stretch and damage to the tree. A steel cable will be connected to the sling and used to pull from an anchored vehicle. Tension will be increased using a Tirfor winching device - which provides incremental tightening and loosening for adjusting the pulling forces with control versus moving the vehicle to apply tension. The placement of the incremental movement measuring instrument will be tested in different positions to find the most advantageous location. The next tree stability pull testing is scheduled for mid to late February, 2006. A consultant from Ontario, Canada is going to be in California on other business. Staff has scheduled a field testing with his participation. Trees have been identified that are good candidates for the pull testing and could provide staff with useful data about tree species we are interested in further testing. The desired outcome is to create a more useful process staff can use over time to collect better data on tree stability in order to make better tree management decisions. Page 2 of 2 ~ .._.-,. - ..~_....,.....,-----_...-._- . ""'_'-~.--"'-"""_-.'_-~~---_""_""'.~---,,_._.,---_.~_....-.._-