Feb 13 2013-Shoffner Consult Tree Report.pdfSHOFFNIER CONSULTING
21529 4"' AVE. W, #1C31, WA 98421 MOBILE: (206)755-2871
February 13, 2013
Tiffiny Brown
Burnstead Construction, LLC
11980 NE 24th St. #200
Bellevue, WA
98005
Re: Tract E Tree Retention Inventory and Protection Recommendations of Woodway Elementary 27 lot
plat.
Tiffiny:
This report is provided per City of Edmonds requirements to address the trees to be retained within Tract E
of the Woodway Elementary 27 lot plat as well as those to be removed. The purpose of evaluating the
trees to be retained is to confirm that their conditions are appropriate for being retained without posing a
risk to the adjacent lots. The purpose for reviewing the conditions of the trees to be removed is to confirm
that removal of them will not leave the retained trees exposed or damaged and thereby posing a risk to the
adjacent lots. In addition to those assessments, this report provides specifications and measures for
protection of the trees through clearing, grading and construction, monitoring the removal of trees adjacent
to Tract E and monitoring of grading within lots 17 and 18 to ensure proper protection of the root systems of
the trees along the boundary with the tract.
I visited the site recently to conduct an assessment of all the trees, both within the tract to be retained and
outside to be removed. I didn't identify the trees with numbered flagging, nor did I conduct any detailed
evaluations on any tree as none were in a condition that posed a concern over the level of risk associated
with them and conducting detailed evaluations wasn't a necessary component of the project scope.
1.0 Site conditions
The existing site conditions, in relation to those proposed for the development, as well as surrounding site
conditions, are important to consider in planning tree retention; it's important to consider vegetative cover,
topography and directions of exposure. Drastic changes in conditions surrounding retained trees can
greatly affect them by direct impacts to their roots resulting from grading, exposing them to a new edge
which increases the susceptibility of both windthrow (failure at the root crown) and windsnap (mid -trunk
failure) and increased stress levels for trees exposed along this new edge.
The project site is an abandoned school grounds that has been completely cleared, aside from a baseball
field backstop. Aside from the trees in the northeast comer, there is no overstory. The only vegetation is
tall grass and weeds. By and large, the topography of the site is flat, with the highest point being the
northeast corner where the tree retention tract is located. I wasn't able to find the year that the school was
built, but it's assumed that it was sometime in the late 60's to early 70's and its likel that the site has been
clear since that time. Based upon their relatively small diameters, the trees in the northeast corner were
either retained when the site was cleared for the school, which would not have been the original logging
event on the property, or were planted or established as volunteers following the clearing.
The project site is bordered by a park to the east, single family residences to the south and west and forest
conditions to the north. The site is fully exposed to the east, south, and west leaving the trees exposed to
prevailing winds from the south, southwest and west.
2.0 Tree Inventory and Assessments
In total there are 51 significant trees in the northeast corner; 34 in the retention tract and 17 outside it. All
are evergreens, however not all are conifers. The species of trees, by level of predominance, include
Douglas fir (Pseudotsuga menziesh), western hemlock (Tsuga heterophylla), a few significant, yet small,
and several sapling and seedling Pacific madrone (Arbutus menziesh) and a single western white pine
(Pinus monticoia). The trees to remain within the tract are spaced tightly, and collectively the crowns of the
conifers create a continuous canopy covering the sparse understory which is composed primarily of tall
grasses a few shrubs and several Pacific madrone seedlings.
Aside from four outlier Douglas firs on the edge of the stand that are 20" dbh or greater, all the trees range
between 8" and 16" dbh. In terms of size of Douglas firs, these trees are small enough to be considered
young. Aside from the 30" and 20" Douglas firs in the southeast corner of the tract which have crown
spreads of at least 30 feet diameter, the crown spreads of the trees are relatively narrow ranging between
15 and 25 feet in diameter. In a closed canopy condition such as this, and for trees of such small sizes,
these crown spreads are normal.
I conducted visual condition and health assessments of each tree by first observing each up close to
inspect the conditions of the trunk, looking for decay pockets or defects, such as cracks or crooks, and then
inspected the conditions of the crowns. Given the density of the canopy, getting a view of the very tops of
the trees was not possible for many of those within the interior, however, I was able to acquire good views
of the canopies from within the stand and didn't note any symptoms indicating high levels of stress, disease
infection or advanced dieback. As I stated in the second paragraph of this report, there was no need to
conduct detailed condition or risk assessments of any tree as none showed any symptoms of defect,
disease infection or illness that would potentially elevate the risk associated with any single tree beyond a
level of acceptability.
Live crown ratio (LCR), an indicator of windfirmness, is the percentage of trunk length/height with live
branches and for Douglas firs, more than hemlocks, is related to the degree of exposure to sunlight. Those
on the outer eastern, southern and western borders have relatively high LCRs of greater than 50%, while
those in the interior have LCRs that range from 40 to as low as 25%. Trees with LCRs as low as 35% pose
a risk to windsnap failure if clearing of adjacent forest leaves them standing as singles or in small clusters
of a few trees. These trees with low LCRs will remain part of a stand and will continue to receive protection
by the stand and their susceptibility to windsnap failure will not increase much, if at all.
3.0 Proposed Development Plan
The proposed development plan of the site is for the construction of 27 single family residences and the
establishment of Tract E for the retention of 34 of the 51 trees in the northeast corner. The impacts of
greatest interest are those that directly affect the trees to be retained within Tract E, both in terms of
maintaining the health and integrity of the trees and in preventing impacts that would, or could, increase the
failure potential of any single tree as a matter of protection for the houses to be built on lots 17 and 18.
Those impacts are as follows:
Removal of the 17 trees along the western and southern perimeters of the stand Removal of the
trees along the perimeter, more so on the western side than the south where there is a considerable
gap between the trees to be removed and those to be retained (thus an edge is already in place) will
create a new edge for trees that have grown under conditions of lower exposure and have become
adapted to these conditions. Although a new edge will be created, the change in conditions,
specifically the degree of exposure, will not increase significantly. Currently, the trees that will remain
are only one tree away from the existing edge so the new conditions won't be so different from how
they are now for these trees. Provided the recommendations pertaining to the removal of the trees
outside the tract are followed, the remaining trees should be capable of adapting to the new conditions
and not be at risk of failure.
2. Clearing and grading for the lots adjacent to the tract -- Given the relatively level site conditions and the
lack of considerable vegetative cover outside the tree retention tract, very little clearing and grading will
need to be done to prepare the lots. However, as shown on the site plan, the grade along the western
and southern boundary of Tract E is to be lowered by four feet at the most over a distance of
approximately 16 feet from the western edge of the new tract and over a distance of approximately 6
feet from the southern side of the new tract.
There are two chief concerns related primarily to grading. Those are damage to and the loss of
structural roots which keep the tree anchored, and damage to loss of small feeder roots which are
connected to the structural roots. The further the cuts are from the tree, the less the root damage and
loss and most importantly that of the structural roots. The retained trees nearest to the southern
boundary of the tract are all further than 16 feet to the north, far enough that the grading impacts won't
affect their structural roots and the loss of feeder roots will be minor.
The trees on the western side are considerably closer to the proposed grading. Two trees that are
essentially on the western border of the tract are within 8 feet of the top of the proposed cut. The rest
of the trees are at least, or more than, 10 feet from the top. The top of the cut at 336, however, is
essentially at grade or perhaps just slightly lower than it by no more than 6 inches. At this location, the
roots are down as far as 2 to 3 feet so none are likely to be impacted. The next contour of the cut at
334 is another 4 feet to the west for a total distance of 12 feet from the trees. This cut will impact some
roots, however, at this distance and depth, it's unlikely to sever the major structural roots.
The most important area of protection to maintain the integrity of the structural roots is termed the root
plate; it is the zone within which the major structural roots are located and if the stability of the trees is
to be maintained, all grading down to and below a depth of 2 feet should stay outside the root plate.
The trees along the western border include diameters of 8", 10", 12", 14" and 16". The root plate
protection zone for trees between 8 and 14" is 7 feet, while that for trees of 16" is 8 feet. Therefore, in
terms of protecting the root plate, the grading is far enough away to maintain the structural integrity of
each of these trees.
4.0 Tree Protection measures, Removal and Grading Guidelines and Monitoring
Given the tight constraints between the trees within the tract and those to be removed, mainly on the
western side, its essential that tree protection measures are instituted and maintained starting before any
work is done adjacent to the tract. Following are the recommended tree protection measures and
monitoring procedures:
9. Prior to beginning any work on tree removal or clearing, the trees to be removed are to be
identified by the project consulting arborist with distinct markings on the trunk.
2. Tree protection fencing is to installed to the outside of the trees to be retained. The purpose of
installing the fencing is to protect the entire tract, including the understory vegetation as well as the
trees. The plan shows the protection fencing located at the edges of the driplines to be retained.
Given the tight confines between the trees to be retained and to be removed along the western
side of the tract, many of the trunks of the trees to be removed are located within the driplines of
the trees to be removed, therefore, along this side off, the fencing will need to located just beyond
the trunks of the trees to be retained. The plan also shows the fencing around the driplines of the
trees on the southern side of tract. Preferably the fencing should be placed at the border of the
tract. To protect the roots of the trees and the existing native vegetation within the tract, this is to
be an area of no intrusion and no machinery. All work done within this area is to be done by hand
only. The seedling Pacific madrones within the tract are to be flagged for identification and
retention.
3. Tree removal is to be monitored by the project consulting arborist to ensure that proper measures
are taken to eliminate damage to the retained trees and that no trees to be retained are removed.
4. Removed trees are to be felled away from those to be retained.
5. Stumps are either to be left in place or removed in a way that will minimize root damage and loss of
the retained trees. They are not to be pulled.
6. Once the trees are removed, the protection fencing is to be moved to the border of Tract E and it is
to remain there throughout the remainder of development and construction.
7. The project consulting arborist is to monitor the removal of the stumps and the grading along outer
edge of the tract. Any roots as large as 912 inch in size are to be hand cut by the project consulting
arborist.
5.0 Use of This Report
This report is provided to Burnstead Construction, LLC as a means of reviewing the conditions of the trees
in the northeast corner of the Woodway Elementary and to make recommendations for protection of the
those to be retained and measures to take to lessen the degree of impacts and to insure the long term
health of these trees. Please note that this report only pertains to the condition of the trees at the time of
the assessment and doesn't warrant or guarantee the long term health of these trees. Tony Shoffner, this
report and Shoffner Consulting cannot guarantee that the health of these trees will not be adversely
affected by the impacts.
If you have any questions regarding this report, please feel free to call me directly.
Cordially,
Tony Shoffner
ISA Certified Arborist #PN -0909A
CTRA #1759