7. Attachment D3 - Arborist Report-Phase 2 -6.23.26.pdf

Arborist Report

Hillsboro Health and Education Center- South Side of Block

Prepared by Nidus Consulting for Apex Companies

June 23, 2026

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Introduction

Demolition is planned for the remaining 3 structures, along with all foundations and hardscapes, on block 56.

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Removing remaining buildings from block 56

Hillsboro School District has acquired the remaining properties on block 56 in

Hillsboro. 3J Consulting is designing demolition documents and overseeing of the demolition of the remaining 3 structures on the block, along with all foundations and hardscapes still in place. Nidus Consulting was the Project Arborist for the first phase of demolition. On April 28, 2026, we inventoried the 5 new trees and reassessed the 18 trees remaining after the first phase of demolition. This Arborist

Report includes an Inventory, Evaluation of Impacts, and Tree Preservation

Recommendations to be submitted to the City of Hillsboro as part of the permitting process.

Three additional properties were added to the project area.

After demolition of the buildings on the north side of the block, 222 SE 5 th Ave, 233 SE 6 th Ave, and 527 SE Baseline St., have been added to the project area.

These three properties are all surrounded by mature landscaping and have street trees planted in the right of way.

Portland Maps showing Hillsboro block 56 (blue). The map shows the site before any demolition occurred. Red X’s mark the buildings already removed and purple squares mark the buildings planned for demolition.

The Hillsboro School District prefers to preserve most trees through the demolition phase

Construction plans are currently unknown. All of the structures on site will be demolished, and all hardscape will be removed. This project will attempt to preserve all non-invasive trees that can be protected by Tree Protection Fencing throughout the demolition phase. Additional trees will likely require removal once the construction is planned.

Hillsboro protects trees on development projects

On construction projects the City of Hillsboro Municipal Code 12.50.230 regulates the removal and protection of trees with trunk diameters 8 inches or greater and conifers 30 feet or taller in height. Additionally, the City of Hillsboro defines most trees over 20 inches DBH (varies by species) as Specimen Trees. These trees have additional protections and can only be removed if:

• a Certified Arborist determines it is hazardous or weakened prior to construction, or

• A Registered Engineer determines that removal is necessary to complete construction.

The City of Hillsboro requires all trees being preserved to be fenced at 5 feet beyond their dripline during construction. This report will explain where this is not possible and recommend alternative methods for protecting trees.

The tree projection fencing already on site will be repositioned to accommodate the removal of all hardscape.

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Trees

Typical of older properties in Washington

County, a mix of native, non-native ornamental and invasive trees were growing together.

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Trees were typical for downtown Hillsboro

Typical of older properties in Washington County, a mix of native, non-native ornamental, and invasive trees were growing together. Most of the trees were in fair condition with a few trees in excellent, good, poor or very poor condition. The trees were relatively large with an average trunk diameter of

~17 inches. Data on each tree is shown in the Summary Table (right), and in the Tree Inventory. Locations are plotted in the Tree Map.

Two additional street trees and three private property trees were added to the inventory.

All of these trees were mature and growing near infrastructure. The street trees

(#12, 13, 15-17, 24-27, 37 & 38) were both growing around power lines and had been pruned for line clearance. The private property trees (#11, 14, 22, 28- 36, 39) were maintained to avoid fences or structures near them.

Trees #14, 33, 34, 36 & 39 were all growing along or close to the northern property line of 527 SE Baseline St.

Western red cedar #22 (39-inch DBH) was ~10 feet from a structure that was demolished and did not appear to be negatively impacted by the work.

Condition

Common Name Excellent Good Fair Poor Very Poor Total cherry plum - - 3 - - 3

Japanese flowering cherry - - 3 - - 3 little leaf linden 1 2 - - 3 little leafed linden - 1 1 - - 2

Portuguese laurel - - 1 - - 1 red flowering dogwood - - 1 - - 1 red maple - - 1 - - 1 salt cedar - - - - 1 1 southern magnolia - 1 - - - 1 sugar maple - - 1 - - 1 tree of heaven 1 - 1 - - 2 western red cedar - 1 1 - 2 white fir - - 1 - - 1 zelkova - - - 1 1

Total 2 5 13 1 2 23

18 trees were preserved through the first demolition phase.

These trees were in a similar condition to the first site visit in June 2024. Trees

#22 and #11 both had demolition within their driplines in the summer of 2025 but were showing no signs of stress.

Trees

Three mature trees were growing within a few feet of the building on

527 SE Baseline St.

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White Fir #33 (20-inch DBH) was in fair condition. It was growing about 10 feet away from tree

#39, a 10-inch DBH flowering dogwood also in fair condition.

Western red cedar

#14 (19-inch DBH) was in good condition. No demolition has occurred within its dripline.

Three mature trees were growing within a few feet of the building on 527 SE

Baseline St.

• Western red cedar #14 was growing 4 feet from the north wall of the building.

• White fir #33 was growing adjacent to a wooden fence and 6 feet from the building’s northwest corner.

• Red flowing dogwood #39 was growing 2 feet from the building’s west entrance with its branches growing over the roof.

Evaluation of Impacts

Private property trees will require careful demolition.

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Construction plans are unknown at this phase.

For now, we are only evaluating impacts to trees based on the demolition of the 3 remaining structures and all the remaining hardscapes and foundations. The perimeter sidewalk will remain.

I anticipate that impacts during demolition will be:

• 20 trees can be preserved

• 11 street trees and 9 private property trees

• 3 trees will be removed

Street trees will have demolition within their dripline.

Since the street trees are on the perimeter of the project with a sidewalk and fencing between them and the demolition, I expect relatively minor root loss.

Private property trees will require careful demolition.

The private property trees all have demolition within their dripline. Careful movement of heavy equipment in the space and precise work will help to reduce impacts to these trees.

• I am most concerned about trees #14, 33, and 39. They are all growing within a few feet of 527 SE Baseline St. In the Tree Preservation Recommendations, I have specified construction monitoring and immediate fencing during the demolition process for these trees.

The demolition crew carefully removed a structure that was ~10 feet from tree #22 (39 inches) during the first phase of the project.

Three trees will be removed.

In my opinion, trees #28, 32, and 36 are not worth preserving through the demolition phase. While these three trees could potentially be preserved through demolition, they are invasive species with hardscape immediately adjacent to their trunks that will be difficult to remove without damaging the trees.

I recommend removing tree of heaven #28.

Tree Preservation Recommendations

Install chain link Tree Protection

Fencing to protect the trees as shown on the Tree Protection Plan.

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Healthy Trees After Construction

The goal of tree preservation on construction projects is to have healthy trees that provide health and environmental benefits to the site for years into the future. Trees that do not have sufficient Tree Protection Zones or are not adequately protected during construction can become liabilities rather than assets. These Tree Protection Recommendations are designed to help increase the chances of having healthy trees many years after construction is complete.

Demolition Design Phase

1. As plans change or when final plans are approved, forward to the

Project Arborist for review.

2. Plan for no demolition within any Tree Protection Fencing and do not move fencing throughout the demolition process. If fencing needs to be moved, contact the Project Arborist.

Pre-Demolition Phase

3. Schedule a meeting with the Project Arborist and demolition contractors working on site to discuss demolition activities, Tree

Protection Measures, and monitoring schedule.

4. Install perimeter fencing and inspect the existing fencing around trees #11, 22, and 29-31. Fencing should match the Tree Protection

Plan.

5. Install chain link Tree Protection Fencing at least 4 feet tall with 6-foot-tall metal posts to protect the Tree Protection Zone as shown on the Tree Protection Plan.

6. Install 4-foot orange snow fencing along the edge of the planting strip around trees #26 & 27 as shown on the Tree Protection Plan.

Demolition Phase

7. Remove trees #28, 32 and 36.

8. The Project Arborist shall be contacted prior to any demolition within 15 feet of all trees being preserved. The Project Arborist shall observe all demolition that they determine to be important to tree preservation.

9. Immediately after demolition of the building at 527 SE Baseline St install new chain link Tree Protection Fencing at least 4 feet tall with 6-foot-tall metal posts to protect the trees #14, 33, 34 & 39 at a location determined by the Project Arborist in the field.

10. All roots shall be cut cleanly with a sharp saw. Stop construction activities in the area and contact the Project Arborist anytime a root larger than 2” in diameter is encountered.

11. Contact the Project Arborist if any tree is damaged, and if any Tree

Protection Fence needs to be moved. The following activities are prohibited within the Tree Protection Fencing:

a. Ground disturbance or construction activity, including vehicle or equipment access

b. Storage of equipment or materials, including soil, temporary or permanent stockpiling

c. Proposed buildings, impervious surfaces, and underground utilities

d. Excavation or fill, trenching, or other work activities.

e. Cleaning of construction equipment, dumping of wastewater, concrete, paint, etc.

12. Keep Tree Protection Fencing in good condition throughout the project. If any fencing slumps, tears, or falls down, construction crews shall immediately repair the Tree Protection Fencing.

Construction Planning Phase

15. Begin planning for future construction by asking a consulting arborist to review construction plans and write an Arborist Report. For most trees, if the Tree Protection Fencing set up for demolition can remain in place through the entirety of construction, the trees can be preserved.

527 SE BASELINE ST

Tree Map

Basemap: Existing Conditions Plan

Created by PBS dated February 2025.

Tree locations are approximate.

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17 22

Tree##

Legend

Project Area

## Tree

Removal##

Legend

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Perimeter fence

Existing fence

Chain link fence – to add

Orange snow fencing to add

After demo. new fencing will be installed

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Tree Map

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Basemap: ESCP Demolition Plan Sheet

C141 Prepared by 3J Consulting for

Hillsboro School District 2026-06-09

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527 SE BASELINE ST

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Tree Inventory

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Tag# Species Common Name DBH Condition Suitability

Protected

Status

Canopy

Comments

N E S W

Prunus serrulata cv.

Japanese flowering cherry

14,12,11, Fair Low Protected 22 2520 15

Single trunk divides into multiple trunks at 3 feet; previously topped with heading cuts; large surface roots

12 Tilia cordata little leaf linden 9 Excellent Moderate

Street

Tree

15 1010 10

Street tree growing in 2 foot wide planting strip; good form; dense crown; under overhead utilities; Hillsboro tagged #200964

13 Tilia cordata little leaf linden 16 Good Low

Street

Tree

15 1520 20

Street tree growing in 2 foot wide planting strip; single trunk divides into multiple trees at 6 feet with seam; topped for overhead utilities; dense crown; minor dieback; Hillsboro tagged #200964

14 Thuja plicata western red cedar

19 Good Moderate Protected 20 2020 20

Single trunk divides into multiple trunks at 7 feet; dense crown; 4 feet north of brick wall

15 Tilia cordata little leafed linden

13 Good Moderate

Street

Tree

15 1215 15

Street tree growing in 2 foot wide planting strip; 3 feet from utility vault; dense crown; under overhead utilities; sidewalk lifting less than 1 inch Hillsboro tagged #200962, flexible tag #200963

16 Tilia cordata little leaf linden 9 Fair Moderate

Street

Tree

15 1515 15

Street tree growing in 2 foot wide planting strip; base too deep;

dense crown; under overhead utilities; Hillsboro tagged #200961

17 Zelkova serrata zelkova 13 Very Poor Low

Street

Tree

15 1015 15

Street tree growing in 12 foot wide planting strip; half of tree failed;

large wounds; declining; Hillsboro tagged #201086

22 Thuja plicata western red cedar

39 Poor Low Protected 20 2015 15 Strong central leader; thin top; ~10 feet from single family home

24 Tilia cordata little leaf linden 12 Good Moderate

Street

Tree

15 1515 15

Street tree growing in 2 foot wide planter; 2 feet from utility vault;

dense crown; under overhead utilities

25 Acer saccharum sugar maple 16 Fair Moderate

Street

Tree

15 1515 15

Street tree growing in 12 foot wide planting strip; single trunk divides into multiple trunks at 8 feet; branch dieback to 6 inches;

thin crown; Hillsboro tagged #200899

Prunus serrulata cv.

Japanese flowering cherry

10,10,9,6

,6,4

Fair Moderate

Street

Tree

12 1212 12

Street tree growing in 12 foot planting strip; base buried;

previously topped; Hillsboro tagged #200900

Prunus serrulata cv.

Japanese flowering cherry

20,15 Fair Low

Street

Tree

15 1515 15

Street tree growing in 12 foot wide planting strip; single trunk divides into multiple trunks at 4 feet; decaying branch wound;

base buried; Hillsboro tagged #200901

28 Ailanthus altissima tree of heaven 30 Fair Low Protected 12 1515 15

Tree growing near property boundary; swollen trunk; unusual form; invasive

29 Prunus cerasifera cherry Plum 12 Fair Moderate Protected 8 8 8 8

Tree growing near property boundary; single trunk divides into multiple trunks at 5 feet; previously topped

Tree Inventory

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Tag# Species Common Name DBH Condition Suitability

Protected

Status

Canopy

Comments

N E S W

30 Prunus cerasifera cherry plum 8 Fair Low Protected 5 5 5 5

Tree growing near property boundary; single trunk divides into multiple trunks at 5 feet; previously topped; thin crown; swollen base

31 Prunus cerasifera cherry plum 14 Fair Moderate Protected 8 5 10 5

Tree growing near property boundary; single trunk divides into multiple trunks at 5 feet; previously topped; cant see base due to epicormic and ivy covering base

32 Ailanthus altissima tree of heaven 8,5,4,3 Excellent Low Protected 15 1515 15

Tree growing near property boundary; single trunk divides into multiple trunks at base; broke curb; 1 foot from building wall

33 Abies concolor white fir 20 Fair Moderate Protected 5 - - -

Off-site; canopy extends ~5 feet over fence; dead lower branches;

~35 feet tall; no tag

34 Prunus lusitanica Portuguese laurel

20,13 Fair Low Protected 5 1510 15

Thinning rounded canopy; trunk splits at base with a deep seam;

ivy growing up trunk; main leader splits into 4 stems all 8 in or larger at 8 feet; sapsucker wells on main stems

36 Tamarix parviflora salt cedar 6,4 Very poor Low Protected 1 6 10 2

The trunk is growing horizontally near the ground; with many dead branches and epicormic growth from the base

Magnolia grandiflora southern magnolia

18,12 Good Moderate

Street

Tree

10 10 9 8

Full mature canopy; two main branches originate at 3 feet;

branches growing 7 feet above street; exposed 7-inch with mowing wound; raised soil around base; 6 in branch removed at 3 feet that is black; Hillsboro tagged #201087

38 Acer rubrum cv. red maple 14 Fair Low

Street

Tree

12 1210 10

The middle of the crown has been topped for power lines; many exposed roots filling the planting area and emerging on the far side of the sidewalk; vertical seam on south side of trunk

39 Cornus florida red flowering dogwood

10 Fair Low Protected 7 10 7 8

Vertical crown; Stem splits into 2 at 4.5 feet; small girdling root that could be pruned; clearance pruned to 10; Growing 2.5 feet from building; crown mostly cleared back from roof

Tree Impacts

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Tag Species DBH

Likelihood of Survival Disposition Comments

11 Prunus serrulata cv. 14,12,11,10 Moderate Preserve Demolition is planned inside the dripline on 3 sides.

12 Tilia cordata 9 High Preserve Street tree, parimiater sidewalk will be maintained.

13 Tilia cordata 16 High Preserve Street tree, parimiater sidewalk will be maintained.

14 Thuja plicata 19 Moderate Preserve ~4 feet from demoltion.

15 Tilia cordata 13 High Preserve Street tree, parimiater sidewalk will be maintained.

16 Tilia cordata 9 High Preserve Street tree, parimiater sidewalk will be maintained.

17 Zelkova serrata 13 Low Preserve Street tree, parimiater sidewalk will be maintained. Poor condition.

22 Thuja plicata 39 Moderate Preserve Removal of brick foundation ~10 feet from base.

24 Tilia cordata 12 High Preserve Street tree, parimiater sidewalk will be maintained.

25 Acer saccharum 16 Moderate Preserve Street tree, equipment, and excavation may be within 5 feet of the dripline.

26 Prunus serrulata cv. 10,10,9,6,6,4 Moderate Preserve Street tree, equipment may be within 5 feet of dripline.

27 Prunus serrulata cv. 20,15 Moderate Preserve Street tree, equipment may be within 5 feet of dripline.

28 Ailanthus altissima 30 Moderate Remove Demolition planned adjacent to base.

29 Prunus cerasifera 12 Moderate Preserve ~5 feet from demoltion on two sides.

30 Prunus cerasifera 8 Moderate Preserve ~5 feet from demoltion on two sides.

31 Prunus cerasifera 14 Moderate Preserve ~5 feet from demoltion on two sides.

32 Ailanthus altissima 8,5,4,3 Moderate Remove ~1 foot from wall to be demolished.

33 Abies concolor 20 Moderate Preserve ~6 feet from demolition, adjacent to fence to be removed

34 Prunus lusitanica 13,20 Moderate Preserve ~15 feet from demolition, adjacent to fence to be removed.

36 Tamarix parviflora 4,6 Low Remove ~3 feet from demolition.

37 Magnolia grandiflora 12,18 High Preserve Street tree, parimiater sidewalk will be maintained.

38 Acer rubrum cv. 14 High Preserve Street tree, parimiater sidewalk will be maintained.

39 Cornus florida 10 Moderate Preserve ~2 feet from demolition

Methods

Sadie assessed street trees of any size, broadleaf trees at least 8” in diameter and conifers at least 30 feet tall.

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Sadie Wechsler (Consulting Arborist, Certified Arborist PN-10269A, Tree Risk

Assessment Qualified) evaluated street trees of any size, broadleaf trees at least 8” in diameter, and conifers at least 30 feet tall on April 28, 2026. Sadie re-evaluated and updated the June 2024 inventory for the entirety of block 56. Sadie collected the following data for each tree:

1. Tree genus and species

2. Trunk diameter (rounded to inches) at 54” height

3. Tree condition, see table to right based on the Guide for Plant Appraisal.

Health, structure and form were assessed independently, and the lowest rating equals the overall condition rating.

4. Suitability for preservation considers future factors affecting the tree’s ability to be an asset to the future site.

• High, tree is likely to be an asset of the future site and should be the focus of preservation efforts.

• Moderate, tree may be an asset of the future site and should be considered for preservation.

• Low, the tree is unlikely to be an asset to the project and should be considered for removal. These trees should be preserved if they are likely to survive construction and if preservation is relatively simple.

Suitability for preservation starts with the current tree condition and includes species specific factors such as:

• species success in region,

• species susceptibility to root loss and other construction impacts,

• typical species longevity, and

• species invasiveness

Suitability for preservation also includes factors of the individual tree such as:

• existing infrastructure around trees,

• structural features that do not affect stability today but are likely to in the future, and

• forest stand dynamics as neighboring trees are removed.

6. Documented and evaluated impacts to trees from construction already complete.

7. Whether trees meet specific size, species, and location criteria in the permitting jurisdiction.

Sadie reviewed the Demolition Plan created by 3J Consulting dated June 9, 2026.

Sadie estimated distances from existing trunk locations and evaluated likelihood of survival of each tree using her experience from previous projects as outlined in the Managing Trees During Site Development and Construction.

Health Structure Form

Excellent

Vigor nearly perfect with little or no twig dieback, discoloration or defoliation.

Strong branch attachments with few or no features affecting tree or branch stability.

Tree shape highly functional and aesthetic in landscape.

Good

Typical vigor with minor twig dieback, defoliation or discoloration.

Good branch attachments with minor and correctable features affecting tree or branch stability.

Tree shape functional and aesthetic in landscape.

Fair

Reduced vigor with moderate twig dieback, defoliation, and/or discoloration.

A single feature significantly affecting or multiple features moderately affecting tree or branch stability that would not be practical to correct or would require multiple treatments over several years.

Tree shape compromises function and/or aesthetics in landscape.

Poor

Compromise d vigor with extensive twig and/or branch dieback and defoliation.

A single feature seriously affecting or multiple features significantly affecting tree stability that cannot be corrected.

Tree shape significantly detracts from function and/or aesthetics to a significant degree.

Very

Poor

Poor vigor with little live foliage or branches.

Multiple features seriously affecting tree stability that cannot be corrected.

Tree shape provides little to no function and is visually unappealing in landscape.

Dead

No live foliage or branches

Tree failed. -http://www.nidusconsulting.com/ http://www.nidusconsulting.com/ https://wwv.isa-arbor.com/store/product/4390 https://wwv.isa-arbor.com/store/product/139/

Nidus Consulting

206.850.6880 sadie@nidusconsulting.com www.nidusconsulting.com

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Arborist Report

Hillsboro Health and Education Center- South Side of Block mailto:sadie@nidusconsulting.com http://www.nidusconsulting.com/ http://www.nidusconsulting.com/