P01 - Roseburg VAMC Building 13 Seismic Upgrade GeoReport - signed.pdf

Report Cover Page

Roseburg VAMC Building 13

Seismic Upgrades

Geotechnical Engineering Report

Roseburg, Oregon

May 14, 2025 | Terracon Project No. 82245178

Prepared for:

Blue Trident, LLC

7829 NE Esperione Lane

Bainbridge Island, Washington 98110

700 NE 55th Avenue

Portland, OR 97203

P (503) 659-3281

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter

May 14, 2025

Blue Trident, LLC

7829 NE Esperione Lane

Bainbridge Island, Washington 98110

Attn: Mr. Brian Moll

P: 206-351-2217

E: brian.moll@blue-trident.com

Re: Geotechnical Engineering Report

Roseburg VAMC Building 13 Seismic Upgrades

913 NW Garden Valley Boulevard

Roseburg, Oregon

Terracon Project No. 82245178

Dear Mr. Moll:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. P82245137 dated

September 24, 2024. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and floor slabs for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

Expires 6/30/2027

Ryan T. Houser, CEG

Senior Geologist

Kristopher T. Hauck, P.E.

Senior Principal | Office Manager

Seismic Sections Revied by Seismic Subject Matter Expert Dr. David Baska, PhD, PE

Geotechnical Engineering Report

Roseburg VAMC Building 13 Seismic Upgrades | Roseburg, Oregon

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Report Summary .............................................................................................. i Introduction Project Description Site Conditions

Previous Site Experience Concurrent Reports

Geotechnical Characterization Geology Groundwater GeoModel

Seismic Considerations Seismic Setting

Cascadia Subduction Zone (CSZ) Crustal Faults Seismic Hazards

Site Class Geotechnical Overview Earthwork

Demolition Site Preparation Bedrock Excavation Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Earthwork Construction Considerations Construction Observation and Testing

Shallow Foundations Design Parameters – Compressive Loads Footing Drains ................................................ Error! Bookmark not defined.

Design Parameters –Uplift Loads Construction Adjacent to Existing Building Foundation Construction Considerations

Floor Slabs Floor Slab Design Parameters Floor Slab Construction Considerations

Lateral Earth Pressures Design Parameters Subsurface Drainage for Below-Grade Walls

General Comments

Facilities | Environmental | Geotechnical | Materials ii

Figures GeoModel

Attachments

Exploration and Testing Procedures Photography Log

Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Note: Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic Overview Statement

Project

Description Seismic retrofit for the existing masonry two-story building.

Geotechnical

Characterization

■ Asphalt section over alluvium and residual soils over basalt bedrock. Basalt appears to be present at depths ranging from about 5 to 9 feet below the ground surface, which corresponds to elevations of approximately 446 to 447 feet

MSL.

■ Groundwater not observed during our current exploration;

however previous explorations at the site encountered groundwater perched on top of the bedrock in localized areas.

Earthwork

Shallow basalt bedrock was weathered and can likely be excavated with conventional earth moving equipment. Intact bedrock will likely require pneumatic hammers for excavation. The residual soils overlying the bedrock are generally clayey in nature.

Due to limited fill placement anticipated, we recommend using imported granular structural fill.

Shallow

Foundations

New shallow foundations should bear on basalt bedrock or granular structural fill extending to bedrock. The following values are applicable for new and existing foundations founded on bedrock:

■ Allowable bearing pressure = 6,000 psf

■ Expected settlements: < 1-inch total, < 1/2-inch differential

Below-Grade

Structures

Cantilevered calls can be designed using the resistance values in the Shallow Foundation section of the report. Earth pressures acting are provided in the Lateral Earth Pressure section.

General

Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed seismic retrofit of the existing

Building 13 on the VAMC located at 913 NW Garden Valley Boulevard in Roseburg, Oregon. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil and rock conditions

■ Groundwater conditions

■ Seismic site class per ASCE 7-22

■ Site specific seismic hazards investigation in accordance with OSSC Chapter

1803.6.1

■ Seismic Design Parameters (ASCE 41-23 General Method)

■ Site preparation and earthwork

■ Demolition considerations

■ Foundation design and construction

■ Bearing capacity of existing foundations

■ Floor slab design and construction

■ Lateral earth pressure

■ Frost considerations

The geotechnical engineering Scope of Services for this project included the advancement of two borings to depths of 10.1 to 14.2 feet below existing ground surface

(bgs), laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and exploration locations are shown on the Site Location and Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the exploration logs and/or as separate graphs in the Exploration and Laboratory Results section.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Information

Provided

Project information was provided by Blue Trident via email on

September 17, 2024. The request included a Statement of Work

(SOW) for seismic upgrades for Building 13 at the Roseburg

Veterans Administration Medical Center (VAMC). We were subsequently provided with as-built architectural plans for

Building 13.

Project

Description

The project will address seismic deficiencies in Building 13 by renovating the interior spaces and correcting facility condition deficiencies to create a building that meets modern seismic design criteria. We understand this may include new and/or expanding existing foundations where structurally deficient within the footprint of the existing structure.

Proposed

Structure

Building 13 will be seismically retrofitted. We anticipate additional foundations will be constructed as part of the retrofit to support additional shear walls.

VA Handbook 18-8

Seismic Risk

Category

Risk Category III

Building 11

Fundamental

Period (provided)

0.235 seconds

ASCE 41-17

Earthquake

Hazard Levels

(provided)

Basic Safety Earthquake (BSE) Hazard Levels:

■ BSE-1N: Seismic hazard taken as two-thirds of the

BSE-2N for use with new buildings.

■ BSE-2N: Seismic hazard associated with ground shaking based on the Risk-Targeted Maximum Considered

Earthquake (MCER) determined in accordance with

ASCE 7 for use with existing buildings.

■ BSE-1E: Seismic hazard with 20% probability of exceedance in 50 years for use with existing buildings.

Should not exceed BSE-2N.

■ BSE-2E: Seismic hazard with 5% probability of exceedance in 50 years for use with existing buildings.

Should not exceed BSE-2N.

Finished Floor

Elevation Existing floor elevations will remain.

Facilities | Environmental | Geotechnical | Materials 3

Maximum Loads

Existing and anticipated structural loads were not provided. In the absence of information provided by the design team, we will use the following loads in estimating settlement based on our experience with similar projects.

■ Columns: 200 kips

■ Walls: 4 kips per linear foot (klf)

■ Slabs: 150 pounds per square foot (psf)

Grading/Slopes No grading is anticipated to be performed as part of this seismic retrofit project.

Below-Grade

Structures

Renovations to the existing structure with basement retaining walls will likely require below grade structure improvements.

Free-Standing

Retaining Walls

New retaining walls are not expected to be constructed as part of site development to achieve final grades.

Pavements No new pavements are planned.

Building Code

US Department of Veterans Affairs Office of Construction and

Facilities Management VA Handbook 18-8, Seismic Design

Requirements, Revised July 1, 2023 (VA Handbook 18-8) in addition to local (relevant) building codes such as Oregon

Structural Specialty Code – current version.

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project consists of Building 13 at the northwestern end of the VAMC Campus is located at 913 NW Garden Valley Boulevard in Roseburg, Oregon. The approximate center of the subject building is located at the following coordinates:

■ Latitude: 43.2267° N

■ Longitude: 123.3699° W

See Site Location

Facilities | Environmental | Geotechnical | Materials 4

Existing

Improvements

Two story brick building built in 1933 totaling approximately

14,250 square feet. The lower floor is a basement level that daylights to the north. Provided plans indicate foundations were designed for a soil bearing pressure of 6,000 psf, and that footing excavations should penetrate to a depth “capable of safely sustaining such a load.” Plans also indicate bottom of footing depths of 446 feet MSL, which is about 5 to 6 feet below the adjacent downslope grades.

Current Ground

Cover

Ground cover around Building 13 consists of asphalt pavement to the north and east, with lawn areas to the south and west.

Existing

Topography

The ground surface around Building 13 generally descends gently to the northwest with approximately 9 feet of total relief.

We also collected photographs at the time of our field exploration program.

Representative photos are provided in our Photography Log.

Previous Site Experience

Terracon previously completed the following geotechnical reports on the Roseburg VAMC

Campus:

■ “Geotechnical Engineering Report, VA Medical Center Upgrades, 913 NW Garden

Valley Blvd, Roseburg, Oregon,” Terracon Project No. 82185070, dated May 24, 2019.

■ “Geotechnical Engineering Report, Roseburg VAMC Building 3 Seismic Retrofit, 913 NW Garden Valley Boulevard, Roseburg, Oregon,” Terracon Project No.

82225133, dated March 10, 2023.

■ “Geotechnical Engineering Report, VA Medical Center Roseburg Building 81

Expansion, 913 NW Garden Valley Boulevard, Roseburg, Oregon,” Terracon

Project No. 82235118, dated January 17, 2024.

Building 13 was not included as part of our previous work at the site.

Concurrent Reports

Terracon is presently conducting geotechnical engineering investigations for seismic upgrades for Buildings 11 and 16. Our investigation results and geotechnical recommendations will be issued under separate cover for these buildings.

Facilities | Environmental | Geotechnical | Materials 5

Geotechnical Characterization

Geology

Based on our review of the Geologic mapping the site is underlain by a thin layer of

Quaternary Fluvial deposits consisting of unconsolidated or poorly consolidated river deposits consisting of moderately sorted, sub-angular to well-rounded boulders, gravel, sand, lean clay and silt. Mapping indicates the alluvium is underlain by early Eocene and late Paleocene Siletz River Volcanics, which comprises the majority of the basement rock of the Oregon Coast Range. The volcanics consist primarily of pillow lava, submarine breccia, and interbedded submarine sedimentary deposits. In the Roseburg area, these volcanics are exposed in tightly folded uplifts and are comprised of pillow basalt, pillow breccia, basaltic sandstone, and mudflow breccia. Our explorations encountered the basalt, presented below as GeoModel Layer 4. In-place weathering of the basalt produced a clayey gravel residual soil presented below as GeoModel Layer 3.

Groundwater

We observed our explorations while drilling and after completion for the presence and level of groundwater. Groundwater was not encountered in our explorations advanced in November

2024 to depths of up to 14 feet bgs. We encountered perched groundwater during our

2019 exploration at the site on the northern portion of the VAMC site at depths of about

2½ to 10 feet bgs.

At times, perched groundwater observations can often be precluded due to the hollow-stem auger methods penetrating into bedrock materials effectively preventing water getting into the sampled soils. Therefore, we expect perched groundwater conditions above the relatively impermeable bedrock materials.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the explorations were performed.

Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the exploration logs. The

1 Wells, R.E., Jayko, A.S., Niem, A.R., Wiley, B.T., Baldwin, E., Molenaar, K.M., Wheeler, K.L., DuRoss, C.B., Givler, R.W., Bukry, D., Elder, W., McKeel, D., and

Marincovich, L., 2000, Geologic map and database of the Roseburg 30' X 60' quadrangle, Douglas and Coos Counties, Oregon, U.S. Geological Survey, Open-File

Report OFR-2000-376, 1:100,000.

Facilities | Environmental | Geotechnical | Materials 6 possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

GeoModel

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration and Laboratory Results and the GeoModel can be found in the

Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each exploration location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 FILL

ASPHALT: 4 inches thick; over POORLY GRADED

GRAVEL FILL (GP FILL): fine grained, angular, dark gray, moist, 2 inches thick {base rock}

2 ALLUVIUM

FAT CLAY WITH SAND to SANDY FAT CLAY (CH):

medium plasticity, dark brown with orangish brown, medium stiff; SANDY SILT (ML): brown, hard, variable gravel content

RESIDUAL

SOIL

POORLY GRADED GRAVEL WITH CLAY (GP-GC) to

CLAYEY SAND (SC): fine grained gravel, dark brown with orangish brown, moist, very dense.

4 BEDROCK

BASALT: dark gray, highly fractured, slightly weathered, strong

Seismic Considerations

Seismic Design information is presented for several levels of ground motion hazard as specified in ASCE 41-23 for levels BSE-1E, BSE-1N, BSE-2E and BSE-2N, as referenced in the U.S. Department of Veterans Affairs Handbook 18-8 Seismic Design

Requirements, dated November 1, 2024. A summary of our evaluation and results is presented in the following sections.

Facilities | Environmental | Geotechnical | Materials 7

Seismic Setting

Western Oregon is generally subject to earthquakes from three different sources:

interface, intraslab, and crustal. All three sources are related to interaction of the Juan de Fuca plate with the North America plate and could cause strong ground shaking at the site. This plate interaction area is referred to as the Cascadia Subduction Zone (CSZ).

The fault trace is located approximately 160 kilometers west of the project site. The CSZ is described as a broad, eastward dipping subduction zone whereby the North American plate is overriding the Juan de Fuca plate. A description of each earthquake source is provided below.

Cascadia Subduction Zone (CSZ)

The Cascadia Subduction Zone (CSZ) is located near the coast of Oregon, Washington, and southern British Columbia where the Juan de Fuca Plate is subducting beneath the

North American Plate . Two seismogenic zones are attributed directly to the subduction zone:

Interface (megathrust) earthquakes occur along the interface between the two plates at depths generally ranging from 0 to 30 kilometers where the plates become locked together. No earthquakes have been recorded from this source, but geologic evidence strongly supports the occurrence of large megathrust earthquakes up to M9.4 every

300 to 700 years. Geologic evidence indicates the last major event occurred in 1700

The eastern edge of the seismogenic portion of the subduction zone earthquakes is located about 20 kilometers west of the site. For an earthquake return period of 2,475 years, interface sources account for about 89 percent of the strong ground shaking hazard.

Intraslab earthquakes occur at depths greater than 40 kilometers where the curvature of the subducting plate increases as the advancing edge moves east, resulting in normal

(extensional) faults within the plate. CSZ intraslab earthquakes are generally less than

2 DeMets, C., Gordon, R.G., Argus, D.F., Stein, S., 1990. Current plate motions:

Geophysical Journal International, v. 101, p. 425-478.

3 Atwater, B.F., 1992. Geologic evidence for earthquakes during the past 2,000 years along the Copalis River, southern coastal Washington: Journal of Geophysical

Research, v. 97, p. 1901-1919.

Facilities | Environmental | Geotechnical | Materials 8 magnitude M7.5 , and do not rupture the ground surface. Given their considerable depth, the ground motions from these earthquakes are relatively low, but are felt over a large area. A M6.8 intraslab earthquake occurred in 2001 near Olympia, Washington, at a depth of 52 kilometers (Nisqually earthquake). The site is located in the seismogenic portion of the intraslab earthquakes, which covers the Umpqua Valley, most of the

Willamette Valley, and portions of the Oregon Coast Range. For an earthquake return period of 2,475 years, intraslab sources account for about 4 percent of the strong ground shaking hazard.

Crustal Faults

Crustal earthquakes typically occur at depths within 35 kilometers of the surface and commonly rupture the ground surface to form an earthquake fault. The vegetative cover and thick sediment deposits in western Oregon obscure surface faults from being readily identified. The maximum magnitude earthquake that may be generated by one of these crustal earthquake sources is thought to be about M7.0. For an earthquake return period of 2,475 years, crustal sources account for about 7 percent of the strong ground shaking hazard.

The United States Geological Survey (USGS) maintains the Quaternary Fault and Fold

Database of the United States, which contains descriptions of known crustal faults throughout the United States. No individual crustal faults contribute more than 1 percent of the strong shaking hazard at the site. The unnamed faults near Sutherlin (No. 862) is the closest crustal fault contributing to strong ground shaking at the site, and is presented in the following table:

Fault Name Unnamed Faults near Sutherlin

USGS Fault Number 862

USGS Fault Class B

Distance from Fault 13 mi NNE

Length of Fault 17.5 miles

Strike (degrees) N49°E

Sense of Movement Normal

Dip Direction Unknown

Slip-rate Category Less than 0.2 mm/yr

Most recent prehistoric deformation

Middle and late Quaternary (<750 ka)

4 Cascadia Region Earthquake Workshop, 2008. Cascadia Deep Earthquakes.

Washington Division of Geology and Earth Resources, Open File Report 2008-1.

Facilities | Environmental | Geotechnical | Materials 9

Seismic Hazards

Seismic hazards resulting from earthquake motions can include earthquake-induced landslides, liquefaction, settlement, subsidence, surface rupture due to faulting or lateral spreading, seiche, and tsunami inundation. Definitions of each seismic hazard and their potential impacts to the site are provided in the following sections.

Ground Shaking

The release of energy from a fault results in shaking of the ground that generally decreases with distance from the fault. Buildings are required by code to withstand a prescribed level of ground shaking without collapse. The prescribed level of ground shaking is a function of proximity to a given fault and the potential size of the earthquake (i.e., its magnitude). Sites consisting of unconsolidated sediments will typically experience stronger ground shaking than sites composed of rock due to amplification effects.

The Oregon Statewide Geohazards Viewer (HazVu) published by the Oregon

Department of Geology and Mineral Studies (DOGAMI) categorizes the expected earthquake shaking from light, moderate, strong, very strong, severe and violent. HazVu indicates the site is located within an area that will experience “strong” ground shaking during a design level earthquake.

Earthquake-Induced Landslides

Earthquake-induced landslides may be characterized as inertial or weakening. Inertial landslides occur when the ground shaking adds a temporary horizontal force to the soil mass that, when combined with the existing gravitational force, exceeds the frictional resistance of the soil. Weakening failures occur when the soil mass losses strength (e.g., liquefaction) and can no longer provide the necessary frictional resistance to remain stable. Earthquake-induced landslides tend to decrease in number with increasing distance from the location of rupture.

5 Statewide Geohazards Viewer (HazVu) published by the Oregon Department of

Geology and Mineral Studies (DOGAMI) https://gis.dogami.oregon.gov/hazvu/, accessed December 2024.

https://gis.dogami.oregon.gov/hazvu/

Facilities | Environmental | Geotechnical | Materials 10

The Statewide Landslide Information Database for Oregon (SLIDO) , categorizes landslide susceptibility from low, moderate, high, and very high. SLIDO indicates the site has a “low” susceptibility to landslides. No mapped landslides are located in the vicinity of the site.

Soil Liquefaction

Soil Liquefaction occurs in loose to medium dense sands, and to a lesser extent silts and gravels, where the water table is close to the ground surface. Recently (Holocene epoch) deposited sands in deltaic environments have historically experienced the greatest amount of liquefaction during strong ground shaking. Liquefaction can cause a loss of soil strength and result in lateral or vertical ground movements. Structures located over soils that liquefy typically do not collapse provided they have been properly designed and constructed. However, the ground surface may settle several inches and there may be several feet of lateral ground movement if the liquefied site is adjacent to a river channel or other body of water. HazVu indicates the soils at the site are non-liquefiable.

Based on the shallow depth to basalt bedrock encountered in our explorations at the site, the soils are considered non-liquefiable.

Coseismic Subsidence

Permanent subsidence, or a lowering of the land level, is expected to occur along the coast and Coast Range during a large magnitude, CSZ interface earthquake. DOGAMI produced maps showing the estimated subsidence expected during a magnitude 9

Cascadia Subduction Zone earthquake . The maps present the subsidence estimates in wide, color-coded bands, and indicates the site is in an area that will experience little to no permanent subsidence during a design-level CSZ interface earthquake.

6 Oregon Department of Geology and Mineral Industries, 2024. Statewide Landslide

Information Database for Oregon (SLIDO), accessed December 2024, from

DOGAMI web site: https://gis.dogami.oregon.gov/maps/slido/.

7 Madin, I.P. and Burns, William J., 2013. Ground motion, ground deformation, tsunami inundation, coseismic subsidence, and damage potential maps for the

2012 Oregon Resilience Plan for Cascadia Subduction Zone Earthquakes. Oregon

Department of Geology and Mineral Industries (DOGAMI) Open-File Report O-13-

06.

https://gis.dogami.oregon.gov/maps/slido/

Facilities | Environmental | Geotechnical | Materials 11

Fault Rupture

Faults are recognized zones of differential earth movement. Stresses build in the Earth’s surface over time and release stored energy along these existing zones of weak rock.

The history of movement along a given fault can be investigated with geologic studies.

Structures located in the path of fault rupture typically experience considerable damage.

Based on our review of the fault information presented in the Crustal Faults section above, the depth to bedrock, and the site’s proximity to the nearest known active faults, it is our opinion that the risk of surface rupture due to ground faulting at the site is low.

Lateral Spread

Lateral spread is the lateral movement of saturated soils that can occur on slopes steeper than about 0.1 percent and level sites adjacent to bodies of water caused by underlying liquefied soils during a significant seismic event. Movement can range from a few inches to several feet, which can cause significant damage to structures supported on these soils. Lateral spread can occur on sites underlain by liquefiable soils that are located on or near slopes, and/or adjacent to a free face, such as a stream bank or the shore of an open body of water. Since the site soils are non-liquefiable, the potential for lateral spread from a design-level earthquake is negligible.

Seiche Inundation

A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing the formation of the standing wave.

Based on the definition of a seiche and that the site is not in close proximity/elevation to an enclosed or partially enclosed body of water, the risk of a seiche affecting the site is negligible.

Tsunami Inundation

A tsunami inundation is defined as the advancement or covering of land by a very large ocean wave that is caused by an underwater earthquake or volcanic eruption and often causes extreme destruction when it advances on to land.

Based on the distance and topographic relation of the site to the Pacific Ocean to the west, the risk of tsunami inundation to the site is negligible.

Facilities | Environmental | Geotechnical | Materials 12

Site Class

The seismic design requirements for structures are based on Seismic Design Category.

Site Class is required to determine the Seismic Design Category for a structure. The Site

Class is based on the upper 100 feet of the site profile defined by a weighted average value of shear wave velocity in accordance with Section 20.4 of ASCE 7-22.

Terracon performed a Multi-Channel Analysis of Surface Waves (MASW) survey at the site to determine the Site Class in accordance with Section 20.3 of ASCE 7-22. The time-averaged shear wave velocity values for the upper 100 feet of the subsurface profile

(VS100) are presented in the following table:

Geophysical Array Average Shear Wave

Velocity Vs100 (ft/sec) Site Class

MASW Bldg 13 1,995 C

Seismic Design Parameters - ASCE 41-23

The seismic design parameters, according to the general procedure of ASCE 41-23

Section 2.4.1 are provided in the following table.

ASCE 41-23 General Method Seismic Design Parameters

Description Value

Site Class C

Site Latitude 43.2267° N

Site Longitude 123.3699° W

Hazard Level

Site-modified Seismic Design

Parameters1

SXS SX1

BSE-2N 1.16 0.65

BSE-1N 0.78 0.43

BSE-2E 0.74 0.41

BSE-1E 0.15 0.09

1. These values were obtained using online seismic design maps and tools available at ASCEhazardtool.org. A copy of the ASCE Hazards Report is provided in the Supporting Information section of this report.

Facilities | Environmental | Geotechnical | Materials 13

Geotechnical Overview

Based on the subsurface conditions encountered at the site and the planned development, the site is feasible for development from a geotechnical perspective.

Based on our explorations and geophysical survey, strong bedrock is present at depths of 5 feet below site grades on the downslope side of the building to 9 feet below grades on the upslope side of the building. These depths correspond to elevations of approximately 446 to 447 feet MSL. Provided plans indicate the existing foundations bear at an elevation of 446 feet MSL, indicating the existing structure foundations are supported on, or very close to, the bedrock surface. Therefore, we have provided bearing pressures and recommendations for new footings to be supported on the bedrock materials and existing foundation bearing recommendations based on the information they are supported on the bedrock materials.

The near surface soils (above the bedrock) are moisture sensitive. Therefore, exterior construction subgrades (if applicable) could become unstable with typical earthwork and construction traffic, especially after precipitation events. The Shallow Foundations section addresses support of new foundations directly bearing on the bedrock or granular structural fill extending to bedrock.

While groundwater was not encountered during our current explorations, since the foundations are on, or very close to, the bedrock surface, perched groundwater may be encountered during excavation. This potentially increases if construction takes place during the wet winter and/or spring months. The contractor should be prepared to dewater localized areas if perched water is encountered.

Contractors should be prepared for bedrock excavations with rock excavation equipment in order to extend excavations into the bedrock.

It is important to note that previously developed sites in these urban environments often encountered buried abandoned utilities, tanks, or other remaining structures. As discussed in our environmental report, a suspect underground storage tank appears to remain onsite along the east side of the existing building. Therefore, the contractor should be prepared to remove undocumented fill and/or other unsuitable materials within the proposed building pad and replaced with engineered fill per the Earthwork section of this report.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration and Laboratory Results), engineering analyses, and our current understanding of the proposed project. The

General Comments section provides an understanding of the report limitations.

Facilities | Environmental | Geotechnical | Materials 14

Earthwork

Earthwork is anticipated to include minor demolition of slabs to provide access for new foundations, excavations for foundations, and limited engineered fill placement around new foundations. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations and floor slabs.

Demolition

Existing slabs, reinforcement, and utilities should be removed from the footprint of new foundations.

Site Preparation

Prior to placing new foundations, existing fill, native soils, and deleterious materials should be removed to expose bedrock materials. Since new foundations will be located on the interior of the existing structure and potentially limited excavations on the immediate exterior of the structure, subgrades should be evaluated by observation and hand probing by geotechnical personnel.

Our explorations were advanced adjacent to the existing structure. Undocumented fills and underground utilities could be present within the footprint of the building and may be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction of new foundations.

Bedrock Excavation

Bedrock was encountered at elevations of approximately 446 to 447 feet MSL (5 to 9 feet below the ground surface) in our explorations. The RQD values of the recovered rock cores within our explorations ranged from about 50 to 70 percent, which is indicative of “fair” rock quality. Our previous explorations at the site encountered rock with RQD values up to 97% (excellent). In our opinion, poor quality and/or closely jointed fair quality rock could be excavated using normal rock construction equipment that is equipped with rock teeth, rippers, and/or breakers. Fair quality rock will require hydraulic or pneumatic breakers, or blasting, to assist in bedrock removal where higher quality rock is encountered. Blasting is not feasible during construction of this seismic retrofit due to the potential for damage to the existing structure.

Facilities | Environmental | Geotechnical | Materials 15

Terracon performed one P-Wave geophysical survey adjacent to Building 13, which consisted of placing geophones setup in a linear configuration along the array as shown on the Exploration Plan. Seismic compression wave (p-wave) velocities obtained from our field tests ranged from about 1,000 ft/s to 20,000+ ft/s, with trend of increasing with depth into the bedrock layers. The cross-sectional image of the wave velocities generated from the seismic testing is included in the Exploration and Laboratory

Results section of this report.

Rippability of rock is generally described in terms of what size of bulldozer equipped with ripping attachments should be able to rip or break the rock to a certain depth. While we do not anticipate bulldozers can be used for excavation on this site, the following discussion will aid the contractor in determining what type of excavation equipment (e.g.

pneumatic hammers, etc.) they should plan for excavation of additional foundations within the footprint of the existing building.

For reference, we compared the findings to the “Caterpillar Performance Handbook” and the Caterpillar “Handbook of Ripping – 12th Edition”. Per the Caterpillar publications and guidance related to igneous basalt bedrock, the following criteria is often used for prediction of excavatability:

Caterpillar Dozer

Model

Seismic Wave Velocity for Basalt and Rippability (ft/sec)

Rippable Marginal Non-Rippable

D9R <7,600 7,600 to 8,600 >8,600

D10R <8,000 8,000 to 8,900 >8,900

D11R <8,700 8,700 to 9,900 >9,900

For reference a D9R dozer was selected for comparison of the field test results. Per the

Caterpillar performance handbook, bedrock with P-wave velocity to about 7,500 ft/s is rippable with a D9R dozer, and where P-wave velocity is over about 8,500 ft/s the bedrock is predicted to likely be unrippable and would require blasting. Based on these guidelines, we estimate that the bedrock at the project site is rippable with a D9R within depths presented in the following table with variability in depth as indicated on the geophysical survey exhibits:

Geophysics

Line

Approximate Depth to Top of

Basalt Bedrock (~4,000 ft/sec)

Approximate Depth with P-

Wave Velocities Less Than

7,600 ft/sec

MASW BLDG 13 2 to 10 feet 15 to 25 feet

One item to note in the above table and plot of wave velocity contours on the figures is the variability of the depth of rippable materials in a short (300-foot length) cross

Facilities | Environmental | Geotechnical | Materials 16 section. Velocity measurements indicate the upper portion of the basalt flow is fractured and/or weathered. The rippability criteria presented in the Caterpillar performance handbook is regarding mass grading and is not necessarily indicative of rippability of the materials within trenches using an excavator and other rock excavation techniques such as hoe-rams may be needed.

It should be noted that rock excavation is dependent on operator skill and experience as well as the size and depth of the planned excavations. Production and ability also are limited by the methods available and/or selected by the contractor. These methods include, but are not limited to, cross-ripping techniques, number of shanks, tooth angle, and tooth penetration. Work area space constrictions can have an impact on the ability to remove bedrock.

Over-breakage of bedrock in foundation and utility excavations should be anticipated and will result in additional quantities of concrete or backfill material. Disturbed or blasted material below design grades must be removed and replaced with compacted engineered fill.

Fill Material Types

Fill required to reach finished grades is anticipated to be very limited in area; therefore, we recommend using imported granular backfill or lean concrete where fill is needed.

The upper layers of materials encountered at the site (GeoModel Layers 2 and 3) have medium to high plasticity and we do not expect them to meet the plasticity requirements for reuse as structural fill.

Imported Fill Materials: Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Fill Type 1 Specifications

Acceptable Location for

Placement

(for Structural Fill)

Common Fill

Oregon Department of

Transportation Standard

Specifications for Construction

(ODOT SSC) Section 00330.13

Selected General Backfill

(Maximum PI = 10% and LL =

40%)

All locations across the site.

Dry weather only acceptable

Facilities | Environmental | Geotechnical | Materials 17

Fill Type 1 Specifications

Acceptable Location for

Placement

(for Structural Fill)

Select Fill ODOT SSC Section 00330.14

Selected Granular Backfill 2

All locations across the site.

Wet and dry weather acceptable.

Crushed

Aggregate Base

Course (CABC)

ODOT SSC Section 02630.10

Dense Graded Aggregate

(2”-0 to ¾”-0) 2

All locations across the site.

Wet and dry weather acceptable.

Trench Backfill

ODOT SSC Section 00405.14 for

Trench Backfill with additional stipulations 4

Acceptable materials include

Common and Select Fill listed above.

Subgrade

Stabilization

ODOT SSC Section 00330.14 for

Selected Granular Backfill above groundwater seepage and ODOT

SSC Section 00330.16 for Stone

Embankment Material with additional stipulations 4

12-inch compacted lift in wet or soft subgrades encountered in subgrade and other utility excavations.

Bedding &

Haunching

ODOT SSC Section 00405.13, Pipe Zone Material

Thickness above and below pipe recommended by

Electrical Engineer

1. Controlled, compacted fill should consist of approved materials that are free

(free = less than 3% by weight) of organic matter and debris (i.e. wood sticks greater than ½ inch in diameter). A sample of each material type should be submitted to the geotechnical engineer for evaluation.

2. Material should have a maximum aggregate size of 2 inches, and a minimum laboratory CBR of 20% for granular soils, and no more than 8% passing the No. 200 sieve by weight determined by ASTM D6913. Fines should have a Plasticity Index (PI) of less than 20% per ASTM D4318. Reclaimed glass will not be accepted.

3. The contractor shall select the appropriate material for use based on the current and forecasted weather conditions at the time of construction.

4. Maximum aggregate size shall be limited to 2½ inches.

Fill Placement and Compaction Requirements

Structural should meet the following compaction requirements.

Facilities | Environmental | Geotechnical | Materials 18

Item Structural Fill

Maximum Lift

Thickness

8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

4 to 6 inches in loose thickness when hand-guided equipment

(i.e. jumping jack or plate compactor) is used

Minimum

Compaction

Requirements 1,2

95% of max.

Water Content

Range

-2% to +2% of optimum

1. Maximum density and optimum water content as determined by the modified

Proctor test (ASTM D1557).

2. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least

70% relative density (ASTM D4253 and D4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1H:1V projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

On-site materials are considered suitable for backfill of utility and pipe trenches from

1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of structural fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

Facilities | Environmental | Geotechnical | Materials 19

Utility trenches are a common source of water infiltration and migration and has been encountered at other building improvements on the campus. Utility trenches penetrating beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line.

If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structures are anticipated to be accomplished with conventional construction equipment where soils were encountered. Refer to the

Bedrock Excavation section for a discussion around bedrock excavation. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the

Facilities | Environmental | Geotechnical | Materials 20 affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The recommendations included in this report, including any options or alternatives, are confirmation dependent. In other words, they are not final, because we, as the geotechnical engineer, relied on judgement and opinion to do so. Terracon can finalize the recommendations only after observing actual subsurface conditions exposed during construction. Therefore, earthwork and foundation excavation efforts should be observed by the Geotechnical Engineer or their representative. Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and existing fill soils), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test performed for every 12 vertical inches of compacted backfill. Where not specified by local ordinance, one density and water content test should be performed for every 100 linear feet of compacted utility trench backfill and a minimum of one test performed for every 12 vertical inches of compacted backfill.

Facilities | Environmental | Geotechnical | Materials 21

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical

Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Shallow Foundations

If the site has been prepared in accordance with the requirements noted in the

Earthwork section, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Description

Maximum Net Allowable

Bearing Pressure 1, 2

6,000 psf – foundations bearing on granular structural fill extending to bedrock. This value may also be used for existing foundations bearing on bedrock.

Required Bearing Stratum

Bedrock (GeoModel Layer 4) or granular structural fill extending to GeoModel Layer 4

Bond Break / Levelling

C…