CityBlomenkampLetter_20150624.pdf
June 22, 2015
Mr. KernenLien
City of Edmonds
Planning Department
121Fifth Avenue North
Edmonds, WA 98026
Re: Trees@23220 Edmonds Way
Dear Mr. Lien:
th
On June 18,at your request,Iinspected the four significant neighboring trees on the
western perimeter of the current development site at 23220 Edmonds Way.Ourassignment
is to evaluate the recent damage to the subject treesand report on our findings.
The subject property has been recently cleared and mass graded. Excavations for site
development along the western and southern perimeters of the site have compromised the
health and structural stability of three significant trees. These are considered high risk and
warrant removal in thevery near future to abate the hazardous condition. Removal within 30
days is recommended.These are identified on the attached map in red, Trees #1, #3 and
#5.Stumps shall be left in the ground to avoid damaging adjacent trees.
Two of the subject trees along the west perimeter have been impacted to a lesser
degree and are in a condition where continued retention is feasible. Periodic monitoring
of condition and risk is warranted for the duration of the project.
Recommendations are provided at the end of this report to maintainthe existing
perimetertrees in the best possible condition. These basically includeproviding
supplemental irrigation to limit stress and provide a favorable environment for new root
growth, and to limit any further disturbance.
No further encroachment into the critical root zones of neighboring trees isanticipated.
The excavation work appears to be suitable to construct landscape retaining walls
without causing any more damage to trees to be retained. Any further cuts in existing
grades along the site perimeterwithin the drip-lines of retained trees shall be supervised
by a qualified tree care professional so appropriate actions can be taken to limit damage
and preserve trees in a viable condition.
Methodology
The tree assessment procedure involves the examination of many factors:
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June 22, 201523220 Edmonds Way Tree Assessment
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The crown of the tree is examined for current vigor. This is comprised of inspecting
the crown (foliage, buds and branches) for color, density, form, and annual shoot
growth, limb dieback and disease.
The bole or main stem of the tree is inspected for decay, which includes cavities,
wounds, fruiting bodies of decay (conks or mushrooms), seams, insects, bleeding,
callus development, broken or dead tops, structural defects and unnatural leans.
Structural defects include crooks, forks with V-shaped crotches, multiple
attachments, and excessive sweep.
The root collar and roots are inspected for the presence of decay,insects and/or
damage, as well as if they have been injured, undermined or exposed, or original
grade has been altered.
Inspection method included examining the tree with binoculars and sounding the trunk with a
mallet. No invasive methods were utilized unless described in the section below.
Findings
A total of five neighboring trees have been adversely impacted by recent excavation
work and gradingon the development site. Four exist on the neighboring property to the
west and one on the neighboring property to the south. Trees were identified in the field
with a numbered piece of orange flagging. These numbers correspond with the attached
Tree Risk Assessment Summary Form and copy of the site plan.
The cut in existing grade encroached to within onefoot of the western property line.
Four significant trees existed within a close proximity of the property line. These are
described as follows:
Tree #1 is a mature Douglas-fir, 42” DBH (diameter at breast height, 4 ½’ above ground)
and 160’ in height. The subject was in good condition with no concerning defects.
Foliage is of normal color and density.The cut in grade occurred at one foot from the
root crown to a depth of +/-three feet. The entire root system east of the subject has
been removed. Three main buttress roots have been severedwithin a few feet of the
root crown.
Tree #2 is a semi-mature western red cedar, 13” DBH, approximately 40’ in height. It is
somewhat suppressed by the larger adjacent Douglas-fir trees. It has a full live crown.
Foliage is of normal color and density. Overall condition is considered good. The cut in
grade occurred at four feet from the root crown to a depth of +/-three feet. Loss of root
mass is estimated at 20%.
Tree #3 is a Douglas-fir, 17” DBH and 105’ in height. It has developed poor trunk taper
from competition with larger adjacent Douglas-fir trees. The lower trunk appears sound,
with no outward indicators of internal decay. Foliage is of normal color and density.The
cut in grade occurred at three feet from the root crown to a depth of +/-three feet. Loss
of root mass is estimated at 40%.
Tree #4 is also a Douglas-fir, 29” DBH and 150’ in height.The lower trunk appears
sound, with no outward indicators of internal decay. Foliage is of normal color and
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June 22, 201523220 Edmonds Way Tree Assessment
Page 3
density.The cut in grade occurred at four and a half feet from the root crown to a depth
of +/-three feet. Loss of root mass is estimated at 30%.
Tree #5 is a neighboring tree on the south perimeter. It is also a Douglas-fir, 12” DBH.
It is of a much younger age class than the trees on the west perimeter. It has also
developed poor trunk taperfrom competition with larger adjacent Douglas-fir trees.
Foliage is of normal color and density.Moderate limb dieback was observed. The lower
trunk is covered in Englishivy. The cut in grade occurred at three feet from the root
crown to a depth of +/-five feet. Loss of root mass is estimated at 40%.
The subject property currently under development was fairly well treed, based on past
aerial imagery. All trees on south and west perimeters are considered new edge trees
with the removal of significant trees from the development lot.
Discussion
Tree #1 is situated closest to the property line. This tree was extensively damaged by
the cut in grade. The entire root system east of the trunk has been severed. The trees
ability to remain standing during strong wind events has been jeopardized.The degree
of root loss is expected to cause an immediate decline in health and vigor. The subject is
considered high risk and warrants removal to abate the hazard.
Tree #2 has not been compromised by the recent development activity. The loss of root
mass is not expected to have adverse impacts on long-term health or stability.
Continued retention is feasible.
Tree #3 has been compromised by the recent clearing and root disturbance. This
poorly-tapered tree is considered high-risk. The change in diameter over length is called
taper. Taper is an important indicator of mechanical strength of a trees bole and crown.
Tall, skinny trees are considered to have poor taper. The subject has an extremely high
height to diameter ratio of 74. Trees with height to diameter ratios greater than 50 are
considered potentially hazardous due to poor structure. Trees with poor taper and high
height to diameter ratios are predisposedto stem failure when placed under heavy
stress loads, such as unusually heavy winds, ice and snowstorms; or are exposed to
unfamiliar environmental stresses.Removal of Tree #3 is warranted to abate the
hazard.
The soils around Tree #4 are dissimilar to the soils adjacent to Tree #1.Soils in this
area are much rockier and compact. No damage to main buttress roots was observed
adjacent to Tree #4. Overall loss of root mass from the excavation work is estimated at
30%, but may be less due to the soil conditions on the development site near the tree.
The degree of root loss does not appear to have compromised structural stability.The
recent clearing of the development site has exposed it to unfamiliar environmental
stresses. Risk of failure is considered moderately-high due the size of the tree and
recent exposure. The subject is well-buffered from southwest prevailing by the
neighboring trees to the west. If the subject is retained, periodic monitoring is
recommended.
Tree #5 on the south perimeter is considered high risk. The degree of root disturbance
and excavation work has compromised structural stability. Removal is recommended to
abate the hazardous condition.
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June 22, 201523220 Edmonds Way Tree Assessment
Page 4
The excavation work adjacent to the subject trees to be retained appears sufficient to
construct landscape retaining walls without causing more damage to perimeter trees.
The clearing of the development site does not appear to have compromised the
structural stability of the remaining trees on the adjacent neighboring lots to the south
and west. Neighboring trees are in fair to good condition. No outward indicators of root
disease were observed on the neighboring properties. The residual trees on the
neighboring property to the west are sound, with no outward indicators of internal stem
decay or serious defect.Continued retention is feasible.
Recommendations
To abate hazard potential and maintain risks at acceptable levels, the removal of Trees
#1, #3 and #5 are recommended. All of these have been compromised by the recent
excavation work.Removal within 30 days is recommended.
Trees #2 and #4can be feasibly retained at this time. Tree #4 is considered a moderate
to high risk. Periodic monitoring is recommended over the next two to three years,
particularly after strong wind events. A re-assessment of condition and risk is warranted
in two to three months and again before final completion or occupancy.Tree #2 can be
crown raised to provide clearance on the development site. Lower branches on the east
side shall be appropriately removed back to the trunk.Remove no more than 20% of the
live foliage.
No further damage is anticipated to perimeter trees. It appears side-yards have been
over-excavated to allow for the construction of landscape retaining walls. Walls shall be
back-filled with native spoils from the site. Although not anticipated, any roots
encountered during landscape wall construction shall be pruned before back-filling.
Damaged roots shall be pruned clean back to sound tissue, where the bark is completely
intact with the root. This will allow the root to sprout new growth. If roots are left
damaged, they will simply decay and not sprout new growth.
Affected areas within the drip-line shall be provided supplemental irrigation during the
summer months to limit stress associated with root loss and disturbance. Disturbed
areas shall be sufficiently watered every two weeks until frequent precipitation returns.
This will create a favorable environment for new root growth.
There is no warranty suggested for any of the trees subject to this report. Weather, latent tree
conditions, and future man-caused activities could cause physiologic changes and deteriorating tree
condition. Over time, deteriorating tree conditions may appear and there may be conditions, which are
not now visible which, could cause tree failure. This report or the verbal comments made at the site in
no way warrant the structural stability or long term condition of any tree, but represent my opinion
based on the observations made.
Nearly all trees in any condition standing within reach of improvements or human use areas represent
hazards that could lead to damage or injury.
For a Forester Every Day is Earth Day
June 22, 201523220 Edmonds Way Tree Assessment
Page 5
Please call if you haveany questions or need further assistance with this project.
Sincerely,
Bob Layton
ISA Certified Arborist#PN-2714A
ISA Tree Risk Assessment Qualified
Subject Trees
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June 22, 201523220 Edmonds Way Tree Assessment
Page 6
Upper crowns of subject trees
Recent grade lowering/excavation adjacent to Tree #1–looking south
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June 22, 201523220 Edmonds Way Tree Assessment
Page 7
Root damage to Tree #1
Tree #1 –shattered buttress root
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June 22, 201523220 Edmonds Way Tree Assessment
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Recent grade lowering/excavation adjacent to Tree #1–looking north
Excavation adjacent to Tree #4, rocky, compacted soils, no evidence of root damage
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June 22, 201523220 Edmonds Way Tree Assessment
Page 9
Tree #5 on south perimeter
Upper crown of Tree #5
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4
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Treatment Recommended
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estimate 20% to 30% loss of root system
Description of Risk Factors
structural stability compromisedstructural stability compromised
40% loss of root system
full crown, vigorous
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TREE RISK ASSESSMENT SUMMARY FORM
extensive root damage
Probability of Failure
minor root damage
Defects
poor trunk taper
recent exposure
major root loss
Target Rating
23220 Edmonds Way
see site plansee site plansee site plansee site plansee site plan
Location
For:
DBH
4213172912
western red cedar
Moderate Risk
Species
Extreme Risk
Risk Rating
Douglas-firDouglas-firDouglas-firDouglas-fir
Zero RiskHigh Risk
Redwood Acres
Low Risk
Size of Part
1 - up to 4"
2 - 4" - 20"
3 - > 20"
12345
9-11
0-23-56-8
12
Tree #
ProjectNo.TS4862
ArboristReport
TO:KautzRouteLLCc/oStevePrice
SITE:23220EdmondsWayEdmonds,WA98026
RE:23220EdmondsWayRiskReport
DATE:June18,2015
PREPAREDBY:ChrisMadison,ISACertifiedArborist#PN7671A
ISAQualifiedTreeRiskAssessor
REVIEWEDBY:ScottD.Baker,RegisteredConsultingArborist414
BoardCertifiedMasterArboristPN0670B
ISAQualifiedTreeRiskAssessor
Summary
Thetreesinquestionweredamagedduetogradingcutonadevelopmentsite.Avalidconstruction
permitwasinplace.
Onetreehasdamagethatmakesitlikelytobeunstableinstrongwinds.Thistreeshouldberemoved.A
secondtreeshouldbemonitoredorremoveddependingontherisktoleranceoftheowner.
Assignment&ScopeofReport
ThisreportoutlinesthesiteinspectionbyChrisMadisonofTreeSolutionsInc,onJune11,2015.We
wereaskedtovisitthejobsiteandprovideaLevel2riskassessmentfortreeslocatedon23220
EdmondsWayinEdmonds,Washington.Wewereaskedtoprovideaformalreportincludingfindings
andmanagementrecommendations.StevePrice,ownerofKautzRouteLLC,requestedtheseservices
forinformationalpurposes.
Thetreesize,species,healthandstructuralconditionandrelatednotesandrecommendationsforeach
treecanbefoundinFigure1:TreeInventory.RiskassessmentsforeachtreecanbefoundinFigure2:
RiskAssessmentMatrix.AsitemapwithtreelocationscanbefoundinFigure3:SiteMap.Photographs,
GlossaryandReferencesfollowthesitemap.LimitsofassignmentcanbefoundinAppendixA.
MethodscanbefoundinAppendixB.Additionalassumptionsandlimitingconditionscanbefoundin
AppendixC.DetailsoftheriskassessmentprocesscanbefoundinAppendixD.
Thisriskassessmentincludedinthisreportdeterminesthepresenceofriskoveralimitedperiodof
time.Thelikelihoodofwholetreeorpartfailureisbasedonwhatisvisibleduringthetimeofthe
assessmentandwhatwouldlikelyoccurundernormalweatherconditions,overaoneyeartimeperiod.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
June18,2015p.2of19
Observations
TheSiteandHistory
ThesiteisaresidentiallotlocatedinEdmonds.Thesiteiscurrentlybeingclearedandgradedfor
developmentbyKautzRouteLLC.Thesiteisgoingtobedevelopedintoamultifamilyneighborhood
community.
Wewerecontactedbyourclientsoonafteragradingcuttothewesternpropertylinecauseddamageto
therootsofadjacenttrees(seePhoto1).Ourclientrequestedthatweassesstheextentofthedamage
forfurtherplanningpurposes.
Frommyunderstandingallworkwasconductedunderaͷ\[ğƓķDevelopmenttĻƩƒźƷapprovedbythe
CityofEdmonds.
Alltreeswerelocatedwithinsixfeetofthegradecutthatoccurred.Thegradecutbeginsatthe
northwestcorner,andextendsallthewaydowntothesouthwestcorner.Thegradecutvariesinheight.
Thedepthofthecutissmallestatthenorthernend(roughlylessthanafootindepth)anddeepestat
thesouthend(roughlyfourfeetindepth).Thegradecutadjacenttothetreesvariesinheightfrom
roughlytwofeettothreefeet.
CivilplansIreviewedcallfora3.9foottallretainingwalltobeinstalledalongthepropertyline,just
insidewherethegradingcuttookplace.Thewallistobebackfilledonthewestside,withadditionalfill
tobeaddedontheeasternside,raisingthegradetoroughlytheoriginalheight.
StevePricehasbeenworkingcloselywiththeneighboreversincethisincidenthadoccurred.Imetwith
theneighbor,Scott,onsiteduringmyinspection.
TheTrees
Iwasaskedtoassesstherootdamageandassociatedrisksofthefivetreesthatwereaffectedalongthe
propertyboundary(seePhoto2).
Iexcavatedthesoilsadjacenttoeachtreetolookfordamagedroots.Inoteddamagedrootsonlynear
Trees1and2.IfoundnodamagedrootsadjacenttoTrees3or4.
Inotedthatthesoilsaresandyandwelldrained.Thiswasalsonotedbythedemolitioncontractorwhen
hewasclearingthesite.
Usingalaserrangefinder,Imeasuredthebaseofthesetreesas109feetawayfromtheeasternedgeof
theneighboringhome.OnlyTrees1and4wouldbetallenoughtostrikethehomewererootfailureto
occur.Tree3is98feettall,onlyelevenfeetshyofthedistancetothehome.Alltreescouldstrike
targetsinthebackyardareatotheeastofthishome.
Tree1isalargeDouglasfir(Pseudotsugamenziesii)whichImeasuredat43inchesindiameterat
standardheight(DSH)and159feettall.Thistreewasingoodhealthandstructure,andshowedgood
vigor.Iobservedfourlargestructuralrootswhichweredamagedduetothegradecut.Imeasuredthe
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
June18,2015p.3of19
diametersofthedamagedrootsat5,10,6,and7inches(seePhoto3).Iexcavatedthebaseofthetree;
giventhestructureofthetrunkflare,Ibelievethelargerootswhichwereseveredwerestructuralroots.
Tree2isasmallWesternredcedarwhichImeasuredat13inchesDSH.Thistreehadsomeminorroots
cut;allofthedamagesrootsweresmallerthanoneinchindiameter.
Tree3isamediumsizedDouglasfir.Thistreehasapoortaperandasmallcanopy,likelyduetobeing
suppressedbythetwolargertrees(Tree1and2)tothenorthandsouth.Thegradingcutoccurredthree
feetfromthebaseofthistree.
Tree4isalargeDouglasfir.Thistreewasingoodhealthandform.Thegradingcutoccurredthreefeet
awayfromthebaseofthistree.
Tree5isasmallCherrylaurel(Prunuslaurocerasus).Ididnotobserveanymajorrootdamagetothis
shrub.
Alltreeshadinvasiveivy(Hedera sp.)attheirbase.IobservedivyclimbingsomeofthetreesIwasasked
toassess,aswellasothertreesinthenearbyarea.
Figure1.TreeInventory
TreeCommonNameBotanicalDSHDripGeneralNotes
No.Name*line**Health
Goodvigor.Epicormicgrowthon
Pseudotsuga trunk.Minortrunkkinkat78feet.
1Douglasfir4327EGood
menziesii Someoverextendedbranches,mostly
onthesouthernside.
Suppressedbynearbytrees.
Western138E
2 Good
Thuja plicata
redcedar
Pseudotsuga Suppressedtree.Poortaper.
17.111E
3 DouglasfirGood
menziesii
Pseudotsuga Goodhealthandstructure.Gradecut3
29.417E
4 Douglasfir
Good
menziesii feetawayfrombase.
Prunus 2.5^3EGoodhealth,fairform.Nomajorroot
5 CherrylaurelGood
laurocerasus damagedonetoplant.
*DiameteratStandardHeight(inches)
**Driplinewasmeasuredfromtheoutermostportionofthetrunktotheoutermostlimitsofthecanopy
(feet)
^Diametertakenatnurserycaliperheightsixinchesaboveground.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
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Figure2.RiskAssessmentMatrix
Likelihoodof
TreeCommonPartLikelytoPartImpactingFailure/ImpactLevelofRiskRating
No.NameFailFailureTargetConsequence
Douglasfir
1 RootsProbableHighLikelySevere High
Westernred
ImprobableVeryLowUnlikelyNegligible Low
2 Roots
cedar
DouglasfirPossibleLowUnlikelySignificant Low
3 Roots
Somewhat
DouglasfirPossibleHighSevere Moderate
4 Roots
likely
CherrylaurelImprobableVeryLowUnlikelyNegligible Low
5 Roots
TheISATreeRiskAssessmentmethodisexplainedinAppendixD.
Discussion
TheRiskAssessmenttableaboveshowsthelikelihoodoffailureofthetreesthatwereaffectedbythe
gradingcut.Scott,theneighbortothewest,requestedthatStevePricehaveusassesstheimpactof
constructiononthesetrees.
Thegradingcuttotheeastofthesetreesdamagedsomeroots,anddestabilizedthesoils.Thisrisk
assessmentonlycoversthenewriskcausedbythisgradingactivity.
ThetwotreesthathavethehighestriskareTrees1(high)and4(moderate).Trees2,3,and5allhave
Lowriskratings.
Frommyobservationsonsite,IbelievethatthemajorstructuralrootsofTree1weresevered,
destabilizingtheentirerootplatetotheeast.WerestrongwindstocausethistreetoswayIbelieveźƷƭ
likelythatthetreecouldfailatthebaseandfalltowardstothehometothewest.Theupperportionof
thetrunk(apartabout16inchesindiameter)wouldlikelystrikethehomeandcauseseveredamageto
theroofandtargetswithiniftheywerepresent.
Irecommendremovalorsnaggingofthistreetoreducetherisk.Workpriorityishigh,andshouldbe
donebeforethefall/winterseasonswhenstrongwindsbecomemorefrequent.
Tree4istallenoughtostrikethehometothewest.Ididnotobserveanydamagedrootsofthistree.
However,Ibelievethelikelihoodoffailuretobepossibleduetothefactthatsoilsweredisturbedthree
feetawayfromthebaseofthistreewhichlikelyaffectedthestabilityofthistree.Ibelievethelarge
sizeoftheuppertreepartwouldcauseseveredamagetothehomewereittofail.Thistreeposesa
ͷaƚķĻƩğƷĻrisk.Thistreecouldberetainedandmonitoreddependingonthetreeowner'srisk
tolerance.Ifretentionisdesired,monitorthebaseofthistreeafterstormeventsforanycrackingor
heavingofsoils.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
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Thesoilsonthesite,whicharesandyandwelldrained,areconducivetotreestability.
Givenmyobservationsonsite,IbelievethatfailureofTrees2and3andimpacttotheneighboring
homeisunlikely.Thebackyardareaisoccasionallyused,butIbelievethelikelihoodoffailureand
impacttoatargetinthebackyardtobeunlikely.Thesetreeswouldbemostlikelytofailduringawind
storm,andthespacewouldlikelybevacantduringthattime.
Tree5isacherrylaurel,whichisaspeciesthatcangrowintoalargeshrub/smalltree.Thisspeciesis
consideredtobeaninvasivespeciesinourregion.Iobservedlittletonodamagetotherootsystemof
thisshrub.Thisshrubhasnomajortargets,andnopartslargeenoughtocauseanydamage.
Inmyopiniontheremovalofanyofthesetreeswouldnotcauseanincreaseofwindexposuretothe
remainingtreesonsite.Thecanopiesofthesetreesaredistinct,andtheyarewelladaptedtowind
loads.Thetreesalsohaveasharedrootingareawhichisalsoabenefittotreestability.Thereisalsoa
heavilywoodedarealocatedtothesouthoftheneighboringproperty,whichactsasawindbufferfor
thepropertyandtreeslocatedwithin.
Theinstallmentoftheretainingwallandfillsoiltotheeastofthesetreesshouldhelpimprovethe
stabilityoftheremainingtrees.Careshouldbetakentoinsurethatnoadditionalrootswillbedamaged
duringtheinstallationoftheretainingwall.Iadvisethefootingtobeplacedatcurrentgradesothatno
furtherexcavationisneeded.Thebackfillshouldbetampeddownsothesoilislightlycompacted.
Irecommendtheremovalofanyivyclimbingthesetrees,andremovalofasmuchivyonthegroundas
possible.Ivycanclimbtrees,addingsignificantweightwhichcouldincreasethelikelihoodoffailure.Ivy
canalsocauseothertreehealthproblemsincludingthegirdlingofvasculartissues.
Allofthetreesaffectedbythegradingcutarelocatedontheneighboringlottothewest.Duetothe
locationofthesetreesScott,theneighbor,isthetreeriskmanager.Alldecisionstomanage/mitigate
theriskofthesetreesareultimatelyuptohim.
Recommendations
RemoveorsnagTree1.Ifasnagisleftitshouldbe15feetorlessinheight.Anewfirtree
plantednexttothesnagwillhelpitblendintothelandscape.
Donotgruborgrindthestumpsoftreesthatareremoved.Stumpgrindingwouldaddtothe
disturbance,andpossiblyfurtherdestabilizetheadjacenttrees.Leavestumpstorotinplace.
Either:retainandmonitorTree4orremovetoeliminaterisk.
RetainandmonitorTrees2and3.
Placefootingsfortheretainingwallatthecurrentgrade.Tampthebackfillsothatitbecomes
lightlycompacted.
Removeallinvasivespeciesatthebaseofthetreesspecificallyremoveanyivyandvinesfrom
thebaseofalltrees.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
June18,2015p.6of19
Figure3.SiteSketch(nottoscale)
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
June18,2015p.7of19
Photographs
Tree1
Tree4
Tree5
Tree3
Tree2
Photo1Fourtreesandoneshrublocatedonthewesternborderofthedevelopedproperty.Phototakenlooking
West.
Tree1
Photo2Damagecausedbygradingcut.PhototakenlookingNorthwest.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
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Photo3Exampleofrootsthatweredamagedduetogradingcut.Rootswerelarge,andlikelymainstructural
rootsofthetree.Pencilinphotoindicatesscale.Left:RootDmeasuringseveninchesindiameter.Right:RootB
teninchesindiameter.
2940WestlakeAve.N(Suite#200)Seattle,WA98109Phone206.528.4670Fax206.547.5873
www.treesolutions.net
23220EdmondsWayRiskReport
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Glossary
advancedassessment:anassessmentperformedtoprovidedetailedinformationaboutspecifictree
parts,defects,targets,orsiteconditions.Specializedequipment,datacollectionandanalysis,
and/orexpertiseareusuallyrequired(ISA2013)
ANSIA300:AmericanNationalStandardsInstitute(ANSI)standardsfortreecare
basicassessment:detailedvisualinspectionofatreeandsurroundingsitethatmayincludetheuseof
simpletools.Itrequiresthatatreeriskassessorwalkcompletelyaroundthetreetrunklookingat
thesite,abovegroundroots,trunk,andbranches(ISA2013)
bendingmoment:aturning,bendingortwistingforceexertedbyalever,definedastheforce(acting
perpendiculartothelever)multipliedbythelengthofthelever(see moment)(ISA2013)
cabling:installationofhardwareinatreetohelpsupportweakbranchesorcrotches(Lilly2001)
chlorotic:foliagewithwhitishoryellowishdiscolorationcausedbylackofchlorophyll
codominantstems:stemsorbranchesofnearlyequaldiameter,oftenweaklyattached(Matheny etal.
1998)
cracks:defectsintreesthat,ifsevere,mayposeariskoftreeorbranchfailure(Lilly2001)
crown:theabovegroundportionsofatree(Lilly2001)
crowncleaning:selectivepruningtoremoveoneormoreofthefollowingparts:dead,diseased,and/or
brokenbranches(ANSIA300)
DBHorDSH:diameteratbreastorstandardheight;thediameterofthetrunkmeasured54inches(4.5
feet)abovegrade(Matheny etal.1998)
deciduous:treeorotherplantthatlosesitsleavessometimeduringtheyearandstaysleafless
generallyduringthecoldseason(Lilly2001)
driveby(assessment):limitedvisualinspectionfromonlyonesideofthetree,performedfromaslow
movingvehicle;alsomaybecalledawindshieldassessment(ISA2013)
epicormic:arisingfromlatentoradventitiousbuds(Lilly2001)
evergreen:treeorplantthatkeepsitsneedlesorleavesyearround;thismeansformorethanone
growingseason(Lilly2001)
force:anyactionorinfluencecausinganobjecttoaccelerate/decelerate.Calculatedasmassmultiplied
byacceleration.Isavectorquantity(ISA2013)
increment:theamountofnewwoodfiberaddedtoatreeinagivenperiod,normallyoneyear.
(Dunster1996)
ISA:InternationalSocietyofArboriculture
includedbark:barkthatbecomesembeddedinacrotchbetweenbranchandtrunkorbetween
codominantstemsandcausesaweakstructure(Lilly2001)
landscapefunction:theenvironmental,aesthetic,orarchitecturalfunctionsthataplantcanhave(Lilly
2001)
lateral:secondaryorsubordinatebranch(Lilly2001)
level(s)ofassessment:categorizationofthebreadthanddepthofanalysisusedinanassessment(ISA
2013)
leverarm:thedistancebetweentheappliedforce(orcenterofforce)andthepointwheretheobject
willbendorrotate(ISA2013)
limitedvisualassessment:avisualassessmentfromaspecifiedperspectivesuchasfoot,vehicle,or
aerial(airborne)patrolofanindividualtreeorapopulationoftreesnearspecifiedtargetstoidentify
specifiedconditionsorobviousdefects(ISA2013)
mitigation:processofreducingdamagesorrisk(Lilly2001)
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moment:aturning,bending,ortwistingforceexertedbyalever,definedastheforce(acting
perpendiculartothelever)multipliedbythelengthofthelever(ISA2013)
monitoring:keepingaclosewatch;performingregularchecksorinspections(Lilly2001)
owner/manager:thepersonorentityresponsiblefortreemanagementorthecontrollingauthority
thatregulatestreemanagement(ISA2013)
pathogen:causalagentofdisease(Lilly2001)
phototropicgrowth:growthtowardlightsourceorstimulant(Harris etal.1999)
Resistographdrill:adrillinginstrumentusedtodeterminethedensityofwoodbymeasuringthe
amountofresistancepresentedtothedrillingneedleasitisdrivenintothewood.Thedrilling
resistanceprofilesshowclearlywherecompressionwood,annualrings,rotinvariousstagesand
otherdefectshavebeenencounteredbythedrillingneedle
retainandmonitor:therecommendationtokeepatreeandconductfollowupassessmentsaftera
statedinspectioninterval(ISA2013)
significantsize:atreemeasuringЏͼDSHorgreater
snag:atreeleftpartiallystandingfortheprimarypurposeofprovidinghabitatforwildlife
soilstructure:thearrangementofsoilparticles(Lilly2001)
sounding:processofstrikingatreewithamalletorotherappropriatetoolandlisteningfortonesthat
indicatedeadbark,athinlayerofwoodoutsideacavity,orcracksinwood(ISA2013)
structuraldefects:flaws,decay,orotherfaultsinthetrunk,branches,orrootcollarofatree,
whichmayleadtofailure(Lilly2001)
tomography:atechniqueforobtaining2Dcrosssectionsor3Dpicturesoftheinteriorofanobjectby
passingsoundwavesthroughtheobjectandmeasuringthetraveltimesoftheacousticsignalsas
theobjectabsorbsorscattersthemonraypathsbetweensourceandreceiver.
VisualTreeAssessment(VTA):methodofevaluatingstructuraldefectsandstabilityintreesbynoting
thepatternofgrowth.DevelopedbyClausMattheck(Harris,etal 1999)
walkby(assessment):alimitedvisualinspection,usuallyfromonesideofthetree,performedasthetreerisk
assessorwalksbythetree(s)(ISA2013)
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References
ANSIA300(Part1)Α2008AmericanNationalStandardsInstitute.AmericanNationalStandardforTree
CareOperations:Tree,Shrub,andOtherWoodyPlantMaintenance:StandardPractices(Pruning).
NewYork:TreeCareIndustryAssociation,2008.
Dunster&AssociatesEnvironmentalConsultantsLtd.AssessingTreesinUrbanAreasandtheUrban
RuralInterface,USRelease1.0.Silverton:PacificNorthwestChapterISA,2006
Dunster,JulianA.,E.ThomasSmiley,NeldaMatheny,andSharonLilly.TreeRiskAssessmentManual.
Champaign,Illinois:InternationalSocietyofArboriculture,2013
E.Smiley,N.Matheny,S.Lilly.BestManagementPractices:TREERISKASSESSMENT.ISA2011.
Lilly,Sharon.!ƩĬƚƩźƭƷƭCertificationStudyGuide.Champaign,IL:TheInternationalSocietyof
Arboriculture,2001.
Matheny,NeldaandJamesR.Clark.TreesandDevelopment:ATechnicalGuidetoPreservationofTrees
DuringLandDevelopment.Champaign,IL:InternationalSocietyofArboriculture,1998.
Mattheck,ClausandHelgeBreloer,TheBodyLanguageofTrees.:AHandbookforFailureAnalysis.
London:HMSO,1994.
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AppendixALimitsofAssignment
Unlessstatedotherwise:1)informationcontainedinthisreportcoversonlythosetreesthatwere
examinedandreflectstheconditionofthosetreesatthetimeofinspection;and2)theinspectionis
limitedtovisualexaminationofthesubjecttreeswithoutdissection,excavation,probing,climbing,or
coringunlessexplicitlyspecified.Thereisnowarrantyorguarantee,expressedorimplied,that
problemsordeficienciesofthesubjecttreesmaynotariseinthefuture.
TreeSolutionsdidnotreviewanyreportsorperformanytestsrelatedtothesoillocatedonthesubject
propertyunlessoutlinedinthescopeofservices.TreeSolutionsstaffarenotanddonotclaimtobe
soilsexperts.AnindependentinventoryandevaluationoftheƭźƷĻƭsoilshouldbeobtainedbya
qualifiedprofessionalifanadditionalunderstandingoftheƭźƷĻƭcharacteristicsisneededtomakean
informeddecision.
A HazardTree isdefinedasatreethathasbeenassessedanddeterminedtohavecharacteristicsthat
makeitanunacceptableriskforcontinuedretention.Ahazardtree,orahazardouscomponent,exist
whenthesumoftheriskfactorsequalsorexceedsapredeterminedthresholdofrisk.The
predeterminedthresholdforriskandtheactionsrequiredtoreducetheriskbelowthatthresholdis
establishedbytheriskmanager.
AsaQualifiedTreeRiskAssessor,myjobistoprovidetheriskmanager,inmostcasestheproperty
owner,withtechnicalinformationrequiredtomakeinformeddecisions.Theriskmanagermustmake
thedecisionabouthowtoimplementtheactionsrequiredtoreducerisktoacceptablelevels.
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AppendixBMethods
Ievaluatedtreehealthandstructureutilizing visualtreeassessment(VTA)methods.Thebasisbehind
VTAistheidentificationofsymptoms,whichthetreeproducesinreactiontoaweakspotorareaof
mechanicalstress.Atreereactstomechanicalandphysiologicalstressesbygrowingmorevigorouslyto
reenforceweakareas,whiledeprivinglessstressedparts(Mattheck&Breloer1994).Anunderstanding
oftheuniformstressallowsmetomakeinformedjudgmentsabouttheconditionofatree.
Usingthe InternationalSocietyofArboriculture(ISA)TreeRiskAssessmentQualificationmethod,I
assignedariskratingtothetree.IperformedaLevel1,2,or3riskassessmentofalltreesasoutlinedin
theBestManagementPracticescompanionpublicationtotheAmericanNationalStandardsInstitute
(ANSI)A300Part9:TreeShrubandOtherWoodyPlantManagementΑStandardsandPractices,Tree
RiskAssessment.Thisapproachprovidesassessorsastructuredprocess,basedongoodscienceand
arboriculture,toassignrecommendedthresholdsforactionforthepurposeofinformingriskmanagers.
AdditionalinformationregardingthemethodcanbefoundinAppendixF.
Imeasuredthediameterofeachtreeat54inchesabovegrade,diameteratstandardheight(DSH).Ifa
treehasmultiplestems,Imeasuredeachstemindividuallyatstandardheightanddeterminedasingle
th
stemequivalentdiameterbyusingthemethodoutlinedintheGuideforPlantAppraisal,9Edition,
publishedbytheCouncilofTreeandLandscapeAppraisers.
Iusedasteelsoilprobetotestsoildepths.
Iusedbinocularstoinspecttheupperpartsofthetrees.
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AppendixCAssumptions&LimitingConditions
ConsultantassumesthatanylegaldescriptionprovidedtoConsultantiscorrectandthattitleto
1.
propertyisgoodandmarketable.Consultantassumesnoresponsibilityforlegalmatters.
Consultantassumesallpropertyappraisedorevaluatedisfreeandclear,andisunderresponsible
ownershipandcompetentmanagement.
Consultantassumesthatthepropertyanditsusedonotviolateapplicablecodes,ordinances,
2.
statutesorregulations.
AlthoughConsultanthastakencaretoobtainallinformationfromreliablesourcesandtoverifythe
3.
datainsofaraspossible,Consultantdoesnotguaranteeandisnotresponsiblefortheaccuracyof
informationprovidedbyothers.
ClientmaynotrequireConsultanttotestifyorattendcourtbyreasonofanyreportunlessmutually
4.
satisfactorycontractualarrangementsaremade,includingpaymentofanadditionalfeeforsuch
ServicesasdescribedintheConsultingArboristAgreement.
Unlessotherwiserequiredbylaw,possessionofthisreportdoesnotimplyrightofpublicationor
5.
useforanypurposebyanypersonotherthanthepersontowhomitisaddressed,withouttheprior
expresswrittenconsentoftheConsultant.
Unlessotherwiserequiredbylaw,nopartofthisreportshallbeconveyedbyanyperson,including
6.
theClient,thepublicthroughadvertising,publicrelations,news,salesorothermediawithoutthe
/ƚƓƭǒƌƷğƓƷͷƭpriorexpresswrittenconsent.
ThisreportandanyvaluesexpressedhereinrepresenttheopinionoftheConsultant,andthe
7.
/ƚƓƭǒƌƷğƓƷƭfeeisinnowaycontingentuponthereportingofaspecificvalue,astipulatedresult,
theoccurrenceofasubsequenteventoruponanyfindingtobereported.
AllphotographsincludedinthisreportweretakenbyTreeSolutionsInc.duringthedocumentedsite
8.
visit,unlessotherwisenoted.
Sketches,drawingsandphotographsinthisreport,beingintendedasvisualaids,arenotnecessarily
9.
toscaleandshouldnotbeconstruedasengineeringorarchitecturalreportsorsurveys.The
reproductionofanyinformationgeneratedbyarchitects,engineersorotherconsultantsandany
sketches,drawingsorphotographsisfortheexpresspurposeofcoordinationandeaseofreference
only.Inclusionofsuchinformationonanydrawingsorotherdocumentsdoesnotconstitutea
representationbyConsultantastothesufficiencyoraccuracyoftheinformation.
Unlessotherwiseagreed,(1)informationcontainedinthisreportcoversonlytheitemsexamined
10.
andreflectstheconditionofthethoseitemsatthetimeofinspection;and(2)theinspectionis
limitedtovisualexaminationofaccessibleitemswithoutdissection,excavation,probing,climbing,
orcoring.Consultantmakesnowarrantyorguarantee,expressorimplied,thattheproblemsor
deficienciesoftheplansorpropertyinquestionmaynotariseinthefuture.
LossoralterationofanypartofthisAgreementinvalidatestheentirereport.
11.
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AppendixDQualifiedTreeRiskAssessment
TheInternationalSocietyofArboriculturehasdevelopedastandardizedandsystematicprocessfor
assessingtreerisk.Thisapproachevaluatesthelikelihoodofwholetreeorpartfailureandany
associatedconsequences,basedonwhatisvisibleduringthetimeofthesitevisitandwhatwouldlikely
occurundernormalweatherconditions,overalimitedtimeperiod.
LEVELSOFRISKASSESSMENT
Level1Survey
Level1shallbealimitedvisualassessmentofanindividualtreeorapopulationoftreestoidentifyspecified
conditionsordefects.Conditionstobeidentifiedshouldincludeobviousdefects.Level1assessmentshallbefrom
alimited,specifiedperspective,suchasdriveby,walkbyoraerialpatrol.Level1surveyassessmentmethodology
shallbespecified.Periodicassessments,monitoring,andfollowuprecommendationsshouldbemadebasedon
theoutcomeoftheassessmentandtheobjectives.
Level2ΑBasic
Level2assessmentsshallincludea360degree,groundbasedvisualinspectionofthetreecrown,trunk,
abovegroundroots,andsiteconditionsaroundthetree.Useofhandtools,trowels,binoculars,orprobes,
shallnotbeprecludedfromaLevel2assessment.Amalletorothertoolshouldbeusedtosoundthetrunk,
largehollowsandloosebark.Level2shall
rootcollarandabovegroundbuttressrootsinordertodetect
provideadetailedvisualinspectionofatree(s)todetecttheconditionsspecifiedandtreedefectsinrelationto
surroundingtargets.
Abasicassessmentshouldincludetheidentificationofconditionsindicatingthepresenceof
structuraldefectsincluding,butnotlimitedto:
Dead,diseased,brokenbranches,stems,androots;
Weaklyattachedbranchesandcodominantstems;
Mechanicaldamageandcracksintothewood;
Abnormalgrowthsuchasswelling,ribs,flatareas,orseams;
Indicationsofdecayandcankers;
Rootplatelifting,abnormaltrunkflare,lackoftrunkflare,soilcracks,gradechange,restricted
orunderminedroots;
Unusualtreearchitectureincludinglean,lowlivecrownratio,poortaper,andcrownasymmetry
Level2inspectionsshouldbeconductedannually;morefrequentlyifspecies,treesize,treeconditionor
otherfactorsindicateaneedforamorefrequentinterval.Schedulinginspectionsshallbetheresponsibility
ofthetreeowner.Monitoringandfollowuprecommendationsshouldbemadebasedontheoutcomeof
theassessmentandtheobjectives.
Level3ΑAdvanced
Level3assessmentsshallincludeallLevel2requirements.Level3shallincludeadvancedmethod(s)toprovide
informationontreestructuralstrength,theextentofspecificstructuraldefects,conditions,orother
moredetailed
factorsinrelationtoatarget.Level3assessmentshallinclude,butisnotlimitedto,oneormoreofthefollowing
treeassessmenttechniques:Aerialassessment ofbranchorstemdefects;MicroresistanceDrilling;Evaluationof
targetrisk;Incrementboring;Probing;Pulltesting;Radiationassessment(eg.radar,xray,gammaray);Sonic
assessment;Sounding;and,Subsurfaceroot and/or soilassessment.
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LIKELIHOODOFFAILURE
Improbable:thetreeorbranchisnotlikelytofailduringnormalweatherconditionsandmaynotfailinmany
severeweatherconditionswithinthespecifiedtimeframe
Possible:failurecouldoccur,butitisunlikelyduringnormalweatherconditionswithinthespecifiedtimeframe
Probable:failuremaybeexpectedundernormalweatherconditionswithinthespecifiedtimeframe
Imminent:failurehasstartedorismostlikelytooccurinthenearfuture,evenifthereisnosignificantwindor
increasedload.Thisisarareoccurrenceforariskassessortoencounter,anditmayrequireimmediateactionto
protectpeoplefromharm
LIKELIHOODOFIMPACTINGATARGET
VeryLow:thechanceofthefailedtreeorbranchimpactingthespecifiedtargetisremote.Thisisthecaseina
rarelyusedsitefullyexposedtotheassessedtreeoranoccasionallyusedsitethatispartiallyprotectedbytreesor
structures.Examplesincludedararelyusedtrailortrailheadinaruralarea,oranoccasionallyusedareathathas
someprotectionagainstbeingstruckbythetreefailureduetothepresenceofothertreesbetweenthetreebeing
assessedandthetargets
impactthetarget.Thisisthecaseinanoccasionallyused
Low:itisnotlikelythatthefailedtreeorbranchwill
areathatisfullyexposedtotheassessedtree,afrequentlyusedareathatispartiallyexposedtotheassessedtree,
oraconstanttargetthatiswellprotectedfromtheassessedtree.Examplesincludealittleusedserviceroadnext
totheassessedtreeorafrequentlyusedpublicstreetthathasastreettreebetweenthestreetandtheassessed
tree
Medium:thefailedtreeorbranchmaynotimpactthetarget,withnearlyequallikelihood.Thisisthecaseina
fullyexposedononesidetotheassessedtreeoraconstantlyoccupiedareathatis
frequentlyusedareathatis
partiallyprotectedfromtheassessedtree.Examplesincludeasuburbanstreetnexttotheassessedstreettreeor
ahousethatispartiallyprotectedfromtheassessedtreebyanintermediatetree
High:thefailedtreeorbranchwillmostlikelyimpactthetarget.Thisisthecasewhenafixedtargetisfully
exposedtotheassessedtreeornearahighuseroadorwalkwaywithanadjacentstreettree
LikelihoodofImpactingTarget(PersonorProperty)
Likelihoodof
Failure(Tree)
VeryLowLowMediumHigh
Somewhat
Imminent UnlikelyLikelyVerylikely
likely
Somewhat
Probable UnlikelyUnlikelyLikely
likely
Somewhat
Possible UnlikelyUnlikelyUnlikely
likely
Improbable UnlikelyUnlikelyUnlikelyUnlikely
Figure1:Riskratingmatrixshowingthelevelofriskasthecombinationoflikelihoodofa
treefailingandimpactingaspecifiedtarget.
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CONSEQUENCESOFFAILURE
Negligible:consequencesarethosethatinvolvelowvaluepropertydamageordisruptionthatcanbereplacedor
repaired,anddonotinvolvepersonalinjury.
Minor:consequencesarethosethatinvolvelowtomoderatepropertydamageorsmalldisruptionstotrafficora
communicationutility.
thatinvolvepropertydamageofmoderatetohighvalue,considerable
Significant:consequencesarethose
disruption,orpersonalinjury.
Severe:consequencesarethosethatcouldinvolveseriouspersonalinjuryordeath,damagetohighvalue
property,ordisruptionofimportantactivities.
Likelihoodof
FailureandConsequences(totarget)
Impact
NegligibleMinorSignificantSevere
Verylikely LowModerateHighExtreme
Likely LowModerateHighHigh
Somewhat
LowLowModerateModerate
likely
Unlikely LowLowLowLow
Figure2:Riskratingmatrixshowingthelevelofriskasthecombinationofthelikelihoodof
atreefailingandimpactingaspecifiedtarget,andtheseverityoftheassociated
consequences.
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RISKRATINGCATEGORIES,TIMINGFORMITIGATION
Inthetreeriskassessmentmatrix,fourtermsareusedtodefinelevelsofrisk;low,moderate,high,andextreme.
Theseriskratingsareusedtocommunicatethelevelofriskandtoassistinmakingrecommendationstotheowner
orriskmanagerformitigationandinspectionfrequency.Thepriorityforactiondependsupontheriskratingand
risktoleranceoftheownerormanager.
9ǣƷƩĻƒĻΓ Theextremeriskcategoryappliesinsituationsinwhichfailureis imminent andthereisahighlikelihood
ofimpactingthetarget,andtheconsequencesofthefailureareͻƭĻǝĻƩĻ͵ͼThetreeriskassessorshould
meanimmediate
recommendthat mitigationmeasuresbetakenassoonaspossible.Insomecasesthismay
restrictionofaccesstothetargetzoneareatoavoidinjurytopeople.
IźŭŷΓ HighrisksituationsarethoseforwhichconsequencesareͻƭźŭƓźŅźĭğƓƷͼandlikelihoodisͻǝĻƩǤƌźƉĻƌǤͼor
ͻƌźƉĻƌǤͲͼorconsequencesareͻƭĻǝĻƩĻͼandlikelihoodisͻƌźƉĻƌǤ͵ͼThiscombinationoflikelihoodandconsequences
indicatesthatthetreeriskassessorshouldrecommendmitigationmeasuresbetaken.Thedecisionformitigation
andtimingoftreatmentdependsupontherisktoleranceofthetreeownerormanager.Inpopulationsoftrees,
thepriorityofhighrisktreesissecondonlytoextremerisktrees.
aƚķĻƩğƷĻΓ ModeraterisksituationsarethoseforwhichconsequencesareͻƒźƓƚƩͼandlikelihoodisͻǝĻƩǤƌźƉĻƌǤͼ
orͻƌźƉĻƌǤͼͳorlikelihoodisͻƭƚƒĻǞŷğƷƌźƉĻƌǤͼandconsequencesareͻƭźŭƓźŅźĭğƓƷͼorͻƭĻǝĻƩĻ͵ͼThetreeriskassessor
mayrecommendmitigationand/orretainingandmonitoring.Thedecisionformitigationandtimingoftreatment
dependsupontherisktoleranceofthetreeownerormanager.Inpopulationsoftrees,moderaterisktrees
representalowerprioritythanhighorextremerisktrees.
\[ƚǞΓ ThelowriskcategoryapplieswhenconsequencesareͻƓĻŭƌźŭźĬƌĻͼandlikelihoodisͻǒƓƌźƉĻƌǤͼͳor
consequencesareͻƒźƓƚƩͼandlikelihoodisͻƭƚƒĻǞŷğƷƌźƉĻƌǤ͵ͼ Sometreeswiththislevelofriskmaybenefitfrom
mitigationormaintenancemeasures,butimmediateactionisnotusuallyrequired.Treeriskassessorsmay
recommendretainingandmonitoringthesetrees,aswellasmitigationthatdoesnotincluderemovalofthe
tree.
Source:E.Smiley,N.Matheny,S.Lilly.BestManagementPractices:TREERISKASSESSMENT.ISA2011.
OPTIONSFORMITIGATION
Removetheriskaltogether,ifpossible,bycuttingoffoneormorebranches,removingdeadwood,orpossibly
removingtheentiretree.Extremerisksituationsshouldbeclosedoffuntiltheriskisabated.
Modifytheriskoffailureprobability.Insomecasesitmaybepossibletoreducetheprobabilityoffailureby
addingmechanicalsupportintheformofcablesbracesorprops.
Modifytheriskratingbymovingthetarget.Riskratingscansometimesbeloweredbymovingthetargetsothat
thereisamuchlowerprobabilityofthedefectivepartstrikinganything.Movingthetargetshouldgenerallybe
seenasaninterimmeasure.
arenotyetseriousand
Retainandmonitor.Thisapproachisusedwheresomedefectshavebeennotedbutthey
thepresentrisklevelisonlymoderate.
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DEFINITIONS(RISK)
acceptablerisk:thedegreeoramountofriskthattheowner,manager,orcontrollingauthorityiswillingtoaccept
(ISA2013)
acceptablethreshold:thehighestlevelofriskthatdoesnotexceedtheƚǞƓĻƩΉƒğƓğŭĻƩƭtolerance(ISA2013)
consequences:outcomeofanevent(ISA2013)
consequencesoffailure:personalinjury,propertydamage,ordisruptionofactivitiesduetothefailureofatree
ortreepart(ISA2013)
likelihood:thechanceofaneventoccurring.Inthecontextoftreefailures,thetermmaybeusedtospecify:(1)
impactingaspecifiedtarget;and(3)thecombination
thechanceofatreefailureoccurring;(2)thechanceof
ofthelikelihoodofatreefailingandthelikelihoodofimpactingaspecifiedtarget(ISA2013)
likelihoodoffailure:thechanceofatreefailureoccurringwithinthespecifiedtimeframe(ISA2013)
likelihoodoffailureandimpact:thechanceofatreefailureoccurringandimpactingatargetwithinthespecified
timeframe(ISA2013)
likelihoodofimpact:thechanceofatreefailureimpactingatargetduringthespecifiedtimeframeISA2013)
onpage2
likely(likelihoodoffailureandimpact):definedbyitsplacementinthelikelihoodmatrix(see Matrix1
oftheTreeRiskAssessmentform);imminentlikelihoodoffailureandmediumlikelihoodofimpact,or
probablelikelihoodoffailureandhighlikelihoodofimpact(ISA2013)
limitedvisualassessment:avisualassessmentfromaspecifiedperspectivesuchasfoot,vehicle,oraerial
(airborne)patrolofanindividualtreeorapopulationoftreesnearspecifiedtargetstoidentifyspecified
conditionsorobviousdefects(ISA2013)
mitigation:processofreducingdamagesorrisk(Lilly2001)
mitigationoptions:alternativesforreducingrisk(ISA2013)
and
mitigationpriority:establishedhierarchyformitigationofrisksbasedonriskratings,budget,resources,
policies(ISA2013)
residualrisk:riskremainingaftermitigation(ISA2013)
riskperception:thesubjectiveperceivedlevelofriskfromasituationorobject,oftendifferingfromtheactual
levelofrisk(ISA2013)
riskrating:thelevelofriskcombiningthelikelihoodofatreefailingandimpactingaspecifiedtarget,andseverity
oftheassociatedconsequences(ISA2013)
risktolerance:degreeofriskthatisacceptabletotheowner,manager,orcontrollingauthority(ISA2013)
target:person,object,orstructurethatcouldbeinjuredordamagedintheeventoftreeorbranchfailure(Lilly
2001)
targetbasedactions:riskmitigationactionsaimedatreducingthelikelihoodofimpactintheeventoftreefailure
(ISA2013)
targetmanagement:actingtocontroltheexposureoftargetstorisk(ISA2013)
targetvalue:themonetaryworthofsomething;theimportanceorpreciousnessofsomething(ISA2013)
targetzone:theareawhereatreeorbranchislikelytolandifitweretofail(ISA2013)
treeriskassessment:asystematicprocessusedtoidentify,analyze,andevaluatetreerisk(ISA2013)
treeriskevaluation:theprocessofcomparingtheassessedriskagainstgivenriskcriteriatodeterminethe
significanceoftherisk(ISA2013)
treeriskmanagement:theapplicationofpolicies,procedures,andpracticesusedtoidentify,evaluate,mitigate,
monitor,andcommunicatetreerisk(ISA2013)
unacceptablerisk:adegreeofriskthatexceedsthetoleranceoftheowner,manager,orcontrollingauthority(ISA
2013)
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