HomeMy WebLinkAbout2026-04-21 - ACR - Light Pole Conflict NE 10th Street
________________________________________________________________
FROM: Shannon Ingebright, (PN 8753A); Atlas Technical Consultants
TO: Charlie Calvano; Landscape Architect; Integrus Architecture
CC: Nick Culp; Forma Construction; Superintendent
PROJECT: Hazen High School Modernization Project
DATE: April 21, 2026
SUBJECT: Recommendations for Trees adjacent to Light Pole Installation
____________________________________________________________________________________
INTRODUCTION
This Arborist Compliance Report (ACR) addresses a stand of trees rooted adjacent to a proposed lamp post as part
of street improvements for the Hazen High School Modernization project. The work will affect a stand of Black Locust
(Robinia pseudoacacia) along NE 10th Street in the City of Renton. The Project Arborist conducted a site visit on April
15, 2026 to assess the stand and discuss the proposed work with the contractor.
METHODS
The subject trees were measured for size at 4.5 feet above the ground surface (diameter at breast height [DBH])
using a graduated metal loggers’ tape. Height and branch radius were visually estimated to the nearest five feet. A
health condition rating was assigned to each tree using a scale from one to six, one being excellent and six being
completely dead. The health factor combines an assessment of tree vigor and the soundness of the above-ground
structure.
An impact assessment of the subject trees was estimated by measuring the distance of the subject trees to the
proposed work area. An estimate of the amount of aerial clearance that would be required for light pole installation
also contributed to this rating. These conditions were visually estimated since the trees are not surveyed.
RESULTS
Five trees are rooted in proximity to the work (Figure 1) (Table 1). One tree, tree number A-1, will likely have
significant impacts from light pole installation while tree number A-2 will likely have moderate CRZ impacts. Three
additional trees are set back from the work and can likely be retained with minimal impacts (Table 1). Tree numbers
A-1 and A-2 are rooted on the fence line within the parcel boundary. The critical root zone (CRZ) impact is estimated
to be high and moderate, respectively, due to proximity to the work. The significant impact to A-2 would be from
pruning for aerial clearance requirements since the subject tree has a slight 20 degree lean into the project area
(Figure 2). Tree numbers A-3 and A-4 are set back from the proposed work and will likely have minimal impacts. Tree
number A-5 is rooted within the City of Renton right-of-way. The CRZ impact is estimated to be moderate.
Table 1 – Tree attribute data and CRZ analysis
TREE
TAG # BOATNICAL NAME COMMON
NAME
DBH
(IN)
HLTH
CONDTN CRZ IMPACT TREE
CREDITS
ACTION
(r=REMOVE)
A-1 Robinia Pseudoacacia Black locust 8.4 FAIR HIGH 4 r
A-2 Robinia Pseudoacacia Black locust 10.6 FAIR MOD 5 r
A-3 Robinia Pseudoacacia Black locust 29.6 FAIR LOW 11 PROTECT
A-4 Robinia Pseudoacacia Black locust 20.3 FAIR LOW 8 PROTECT
A-5 Robinia Pseudoacacia Black locust 22.5 FAIR MOD N/A (city tree) r
The removal of tree numbers A-1 and A-2 will result in the loss of 9 tree credits. The total tree credits required for
the project per the City of Renton Municipal Code Chapter RMC 4-4-130(H.)(1.)a is: 1,020 tree credits. The total tree
credits based on the current number of retained trees is 1,120. This includes the additional trees invented within
the parcel adjacent to the work (A-1 through A-4). Therefore, the current total tree credits with the removal of tree
numbers A-1 and A-2 is: 1,111 tree credits. Tree number A-5, if removed, would not be subject to replacement based
on direct communication with the City.
DISCUSSION
Tree numbers A-1 and A-2 are recommended for removal due to the anticipated severity of impacts associated with
installation of the proposed light pole due to both belowground and aerial imapcts. Both trees are located in
proximity to the work area with the edge of excavation estimated at 3.5 to 4 feet from the base of each trunk. This
distance represents a substantial encroachment into the CRZ of the subject trees and is expected to result in high
below-ground impacts. In addition to root disturbance, installation of the light pole would require aerial clearance
of tree numbers A-1 and A-2 to accommodate pole height and maintenance access. The combination of a high CRZ
impact and required branch pruning would likely contribute to elevated stress levels, increasing the potential for
reduced vigor and long-term decline, of the subject trees. When considered cumulatively, these impacts exceed
thresholds typically considered acceptable for retention.
The species composition and condition of the stand further reduce its suitability for long term retention,
independent of construction-related impacts. English ivy (Hedera helix) is present throughout the stand and has
grown into the crowns of all subject trees (Figure 3). Ivy infestation is contributing to increasing physiological stress
and is expected to continue to adversely affect tree health over time. Additionally, Black Locust is listed as a Class C
noxious weed in King County and is recognized for its invasive characteristics, including the formation of dense stands
that displace native vegetation. These factors reduce the ecological and long-term functional value of the stand and
further support removal of Tree numbers A-1 and A-2 in association with the proposed work.
RECOMMENDATION
The chain-link fencing delineating the proposed sidewalk from the school parcel is functioning as tree protection
fencing currently. If tree number A-4 is retained, high visibility construction fencing is recommended to be
established around tree number A-4 to avoid compaction within the CRZ and to deter material storage within the
Tree Protection Area. Any unforeseen root impacts encountered during construction should be evaluated
immediately by the Project Arborist, and work should pause in the affected area until appropriate mitigation
measures are identified.
CONCLUSION
Tree numbers A-1 and A-2 are recommended to be removed, while Tree numbers A-3 and A-4 are recommended to
be retained and protected. Tree numbers A-1 and A-2 are proposed for removal because they are in direct conflict
with the proposed street improvement work and would experience substantial impacts associated with installation
of the lamp post.
Figure 1 – Overview of the stand of Black Locust. Note the subject trees directly adjacent to the work are shown here. Tree numbers
A-3 and A-4 are set back from the work almost directly behind A-1 and A-2
A-5 A-1 A-2
Figure 2 – Branch pruning will be required to accommodate lamp post installation.
Figure 3 – Another view of the subject stand showing the extent of the ivy infestation and dense grove.
Attachment A
Electrical Plan Sheet (No Arborist markup)
~A S P H ~
6'AW
6'AW6'AW
8"W(R)8"W(R)
IE 8"PVC(W):463.70'IE 8"PVC(E):461.36'8"PSD
12"PSD
12"PSD(R)
CB RIM:452.87'
IE 12"PE(S):449.35'
H2O:449.35' BTM:447.9'
12"PSD(R)
SSMH RIM:469.06'
(W/ CHIMNEY COVER)
8"CP(N)
8"VC(W)(R)
8"DI(E)(R)
COC:446.26'
8"SS
8"PSS8"PSS(R)
8"PSS(R)
8"PSS(R)
2"G(P)
2"G(P)
2"G(P)
4"G(R)
4"G(R)
PP
SLHH
N.E. 10TH ST.
( A DEDICATED PUBLIC RIGHT OF WAY)
30'