73316.022_GeoRprt_20240111_FNL.pdf

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Geotechnical Engineering Report Beatrice Morrow Cannady Elementary School

New Portable Classroom Structures

18031 SE Vogel Road

Happy Valley, Oregon

Prepared for:

North Clackamas School District

4444 SE Lake Road

Milwaukie, Oregon 97222

January 11, 2024

PBS Project 73316.022

© 2024 PBS Engineering and Environmental Inc.

4 4 1 2 S C O R B E T T A V E N U E , P O R T L A N D , O R 9 7 2 3 9 ▪ 5 0 3 . 2 4 8 . 1 9 3 9 M A I N ▪ 8 6 6 . 7 2 7 . 0 1 4 0 F A X ▪ P B S U S A . C O M

Geotechnical Engineering Report

Beatrice Morrow Cannady Elementary School

New Portable Classroom Structures

18031 SE Vogel Road

Happy Valley, Oregon

Prepared for:

North Clackamas School District

4444 SE Lake Road

Milwaukie, Oregon 97222

Prepared by:

Brian Ackerman, PE

Geotechnical Project Engineer

Reviewed by:

Ryan White, PE, GE

Principal Geotechnical Engineer

6/30/2024

North Clackamas School District

Beatrice Morrow Cannady Elementary School

New Portable Classroom Structures

Happy Valley, Oregon i

Table of Contents

1 INTRODUCTION

General Purpose and Scope

1.2.1 Subsurface Explorations

1.2.2 Soils Testing

1.2.3 Geotechnical Engineering Analysis

1.2.4 Report Preparation

Project Understanding

2 SITE CONDITIONS

Surface Description Subsurface Conditions Groundwater

3 CONCLUSIONS AND RECOMMENDATIONS

Geotechnical Design Considerations Shallow Foundations

3.2.1 Minimum Footing Widths and Design Bearing Pressure

3.2.2 Footing Preparation

3.2.3 Lateral Resistance

Retaining Walls

3.3.1 Soil Parameters for Retaining Wall Design

Retaining Wall Foundations

3.4.1 Retaining Wall Backfill

3.4.2 Drainage

Seismic Design Considerations

3.5.1 Code-Based Seismic Design Parameters

3.5.2 Liquefaction Potential

4 CONSTRUCTION RECOMMENDATIONS

Site Preparation

4.1.1 Subgrade Verification

4.1.2 Wet/Freezing Weather and Wet Soil Conditions

4.1.3 Dry Weather Conditions

5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS

6 LIMITATIONS

7 REFERENCES

Beatrice Morrow Cannady Elementary School ii

Supporting Data

TABLES

Table 1. Soil Parameters for Retaining Wall Design Table 2. 2022 OSSC Seismic Design Parameters

FIGURES

Figure 1. Vicinity Map

Figure 2. Site Plan

Figure 3. Lateral Surcharge Detail

APPENDICES

Appendix A: Field Explorations

Table A-1. Terminology Used to Describe Soil

Table A-2. Key to Test Pit and Boring Log Symbols

Figures A1–A3. Logs for Borings B-1 through B-3

Appendix B: Laboratory Testing

Figure B1. Atterberg Limits Test Results

Figure B2. Summary of Laboratory Data

Beatrice Morrow Cannady Elementary School

1 INTRODUCTION

General

This report presents results of PBS Engineering and Environmental Inc. (PBS) geotechnical engineering services for the proposed new portable classroom structure at Beatrice Morrow Cannady Elementary School located at

18031 SE Vogel Road in Happy Valley, Oregon (site). The general site location is shown on the Vicinity Map, Figure 1. The locations of PBS’ explorations in relation to existing site features are shown on the Site Plan, Figure 2.

Purpose and Scope

The purpose of PBS’ services was to develop geotechnical design and construction recommendations in support of the planned new portable classroom structure. This was accomplished by performing the following scope of services.

1.2.1 Subsurface Explorations

Three borings were advanced to depths of approximately 16.5 feet below the existing ground surface (bgs) within the proposed structure area. The borings were logged and representative soil samples collected by a member of the PBS geotechnical engineering staff. The approximate boring locations are shown on the Site

Plan, Figure 2. The interpreted boring logs are presented as Figures A1 through A3 in Appendix A, Field

Explorations.

1.2.2 Soils Testing

Soil samples were returned to our laboratory and classified in general accordance with the Unified Soil

Classification System (ASTM D2487) and/or the Visual-Manual Procedure (ASTM D2488). Laboratory tests included natural moisture contents, grain-size analyses, and Atterberg limits. Laboratory test results are included in the exploration logs in Appendix A, Field Explorations; and in Appendix B, Laboratory Testing.

1.2.3 Geotechnical Engineering Analysis

Data collected during the subsurface exploration and testing were used to develop site-specific geotechnical design parameters and construction recommendations.

1.2.4 Report Preparation

This Geotechnical Engineering Report summarizes the results of our explorations, testing, and analyses, including information relating to the following:

• Field exploration logs and site plan showing approximate exploration locations

• Laboratory test results

• Groundwater levels and considerations

• Liquefaction potential

• Shallow foundation design recommendations:

o Minimum embedment o Allowable bearing pressure o Estimated settlement o Sliding coefficient

• Lateral earth pressures for retaining wall design including:

o Active, passive, and at-rest earth pressures o Seismic lateral force

Beatrice Morrow Cannady Elementary School o Allowable bearing pressure o Sliding coefficient o Groundwater and drainage considerations

• Seismic design criteria in accordance with the 2022 Oregon Structural Specialty Code (OSSC)

• Slab and foundation subgrade preparation recommendations

Project Understanding

PBS understands current plans are to add a new single-story, lightly loaded portable classroom structure on the north side of the existing school, south of the access road that leads to the stormwater facility, in an area covered with grass lawn and AC pavement. A retaining wall is planned along the north side of the new structure. PBS previously prepared a geotechnical engineering report for design and construction of the existing school (PBS, 2017).

2 SITE CONDITIONS

Surface Description

Three borings were advanced at the proposed portable classroom structure location on the north side of the existing school. The proposed portable classroom structure location slopes gently down to the north and northeast.

Subsurface Conditions

The site was explored by drilling three borings, designated B-1 through B-3, to a depth of 16.5 feet bgs. The drilling was performed by Dan J. Fischer Excavating, Inc., of Forest Grove, Oregon, using a trailer-mounted Little

Beaver drill rig and solid-stem auger drilling techniques.

PBS has summarized the subsurface units as follows:

ASPHALT

CONCRETE (AC):

Each boring encountered approximately 3 to 5 inches of AC at the ground surface.

CRUSHED

AGGREGATE

BASE:

Each boring encountered approximately 9 to 13 inches of crushed aggregate base underlying the AC.

CLAY (CH): Gray to brown, fat clay was encountered in each boring beneath the crushed aggregate base until the termination depth of the borings. The clay was medium stiff to very stiff, exhibited medium to high plasticity, and contained varying amounts of fine sand and fine, subangular gravel.

Groundwater

Static groundwater was encountered in borings B-2 and B-3 at depths of 13.7 and 4.5 feet, respectively. Please note that groundwater levels can fluctuate during the year depending on climate, irrigation season, extended periods of precipitation, drought, and other factors.

Beatrice Morrow Cannady Elementary School

3 CONCLUSIONS AND RECOMMENDATIONS

Geotechnical Design Considerations

The subsurface conditions at the site consist of medium stiff to stiff clay. Based on our observations and analyses, conventional foundation support on shallow spread footings is feasible for the proposed new portable structure. Excavation with conventional equipment is feasible at the site.

Shallow Foundations

Shallow spread footings bearing on at least 6 inches of crushed rock overlying medium stiff or better clay may be used to support loads associated with the proposed new portable classroom structures, provided the recommendations in this report are followed. Footings should not be supported on undocumented fill, if encountered.

3.2.1 Minimum Footing Widths and Design Bearing Pressure

Continuous wall and isolated spread footings should be at least 18 and 24 inches wide, respectively. Footings should be sized using a maximum allowable bearing pressure of 2,000 pounds per square foot (psf). This is a net bearing pressure and the weight of the footing and overlying backfill can be disregarded in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long-term live loads. Allowable bearing pressures may be increased by one-third for seismic and wind loads.

Footings will settle in response to applied loads. Based on our evaluation of the subsurface conditions and our analysis, we estimate post-construction settlement will be less than 1 inch for the column and perimeter foundation loads. Differential settlement will be on the order of one-half of the total settlement.

3.2.2 Footing Preparation

Excavations for footings should be carefully prepared to a neat and undisturbed state. A representative from

PBS should confirm suitable bearing conditions and evaluate all exposed footing subgrades. Observations should also confirm that loose or soft materials have been removed from new footing excavations and concrete slab-on-grade areas. Localized deepening of footing excavations may be required to penetrate loose, wet, or deleterious materials.

PBS recommends a 6-inch-thick layer of compacted, crushed rock be placed over the footing subgrades to help protect them from disturbance due to foot traffic and the elements.

3.2.3 Lateral Resistance

Given the relatively shallow footing embedment depths, we do not expect that footings supporting the new portable classroom structure can develop any passive resistance.

Retaining Walls

Addition of the proposed new portable classroom structure will require construction of retaining walls less than 5 feet tall to provide foundation support for the new structure. We recommend any retaining walls be founded on a minimum of 6 inches of crushed rock overlying medium stiff or better clay; be provided with adequate drainage; and be backfilled with clean, angular, crushed rock fill, in accordance with the recommendations provided in the following sections of this report.

3.3.1 Soil Parameters for Retaining Wall Design

The soil parameters commonly used for the design of retaining wall structures are soil moist unit weight “γm,” soil saturated unit weight “γsat,” soil internal friction angle “φ,” and soil cohesion “c.” The soil parameters

Beatrice Morrow Cannady Elementary School recommended for use in the retaining structure design are presented in the following Table 1, Soil Parameters for Retaining Wall Design.

Table 1. Soil Parameters for Retaining Wall Design

Soil

Material

Moist

Unit

Weight, γm (pcf)

Saturated

Unit

Weight, γsat (pcf)

Friction

Angle, φ

(degrees)

Cohesion, c (psf)

Lateral Earth Pressure Coefficient*

Active, Ka Passive, Kp At-Rest, Ko

Clay (CL) 115 120 28 0 0.32 2.3 0.53

ODOT

Gravel

Backfill for Walls

130 135 35 0 0.25 N/A 0.43

*These parameters assume flat ground surface conditions in front of the wall and behind the wall. The passive lateral earth pressure coefficients have been reduced by a factor of two to account for the amount of deflection required to engage full passive pressures.

Per section 1803.5.12 of the 2022 OSSC, the determination of dynamic seismic lateral earth pressures on site retaining walls less than 6 feet tall is not required.

Additional lateral pressures due to surcharge loads can be estimated using the guidelines shown on Figure 3, Lateral Surcharge Detail.

Retaining Wall Foundations

Retaining wall footings should be designed in accordance with the recommendations for spread footings, included in section 3.2 of this report. For retaining wall footings, lateral loads can be resisted by passive earth pressure on the sides of footings, and by friction at the base of the footings. A passive earth pressure of 250 pounds per cubic foot (pcf) may be used for footings confined by native soils and new structural fills. The allowable passive pressure has been reduced by a factor of two to account for the large amount of deformation required to mobilize full passive resistance and further reduced to account for the sloping toe conditions. Adjacent floor slabs, pavements, or the upper 12-inch depth of adjacent unpaved areas should not be considered when calculating passive resistance. For footings supported on native soils or new structural fills, use a coefficient of friction equal to 0.35 when calculating resistance to sliding. These values do not include a factor of safety (FS).

3.4.1 Retaining Wall Backfill

Backfill material placed behind retaining walls and extending a horizontal distance of 0.5H, where H is the height of the wall, should consist of granular material meeting Oregon Department of Transportation Standard

Specifications for Construction (ODOT SS) 00510.12 – Granular Wall Backfill, which recommends ODOT SS

02630.11 – Open-Graded Aggregate. We recommend the granular wall backfill be separated from general fill, native soil, and/or topsoil using a geotextile fabric that meets the requirements provided in ODOT SS 02320.10

– Geosynthetics, Acceptance, and ODOT SS 02320.20 – Geotextile Property Values, Table 02320-4 for separation geotextile. The geotextile should be installed in conformance with ODOT SS Section 00350 –

Geosynthetic Installation.

The wall backfill should be compacted to a minimum of 92% of the maximum dry density, as determined by

ASTM D1557. However, backfill located within a horizontal distance of 3 feet from the retaining walls should

Beatrice Morrow Cannady Elementary School only be compacted to approximately 90% of the maximum dry density, as determined by ASTM D1557. Backfill placed within 3 feet of the wall should be compacted in lifts less than 6 inches thick using hand-operated tamping equipment (such as jumping jack or vibratory plate compactors).

3.4.2 Drainage

Recommended lateral earth pressures assume that walls are fully drained and no hydrostatic pressures develop. For cantilevered concrete walls, a minimum 2-foot-wide zone of free-draining material meeting the requirements of ODOT SS 00430.11 – Granular Drain Backfill Material should be installed immediately behind the wall. A 4-inch diameter, perforated drainpipe should be installed at the base of the drain rock and routed to a suitable discharge point approved by the civil engineer.

Seismic Design Considerations

3.5.1 Code-Based Seismic Design Parameters

The current seismic design criteria for this project are based on the 2022 Oregon Structural Specialty Code

(OSSC). Based on subsurface conditions encountered in our explorations, Site Class E is appropriate for use in design. The seismic design criteria, in accordance with the 2022 OSSC, are summarized in Table 2.

Table 2. 2022 OSSC Seismic Design Parameters

Parameter Short Period 1 Second

Maximum Credible Earthquake Spectral Acceleration Ss = 0.82 g S1 = 0.36 g

Site Class E

Site Coefficient Fa = 1.3 Fv = 2.56*

Adjusted Spectral Acceleration SMS = 1.07 g SM1 = **

Design Spectral Response Acceleration Parameters SDS = 0.71 g SD1 = **

MCEG Peak Ground Acceleration PGA = 0.37 g

Site Amplification Factor at PGA FPGA = 1.46

Site Modified Peak Ground Acceleration PGAM = 0.54 g g= Acceleration due to gravity

* This value of Fv shall only be used to calculate Ts

** Site-specific site response analysis is not required for structures on Site Class E sites with S1 greater than or equal to 0.2, provided the value of the seismic response coefficient Cs is determined by Eq. (12.8-2) for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with either Eq. (12.8-3) for TL ≥ T > 1.5Ts or Eq. (12.8-4) for T > TL.

3.5.2 Liquefaction Potential

Liquefaction is defined as a decrease in the shear resistance of loose, saturated, cohesionless soil (e.g., sand) or low plasticity silt soils, due to the buildup of excess pore pressures generated during an earthquake. This results in a temporary transformation of the soil deposit into a viscous fluid. Liquefaction can result in ground settlement, foundation bearing capacity failure, and lateral spreading of ground.

Based on a review of the Oregon Statewide Geohazard Viewer (HazVu), the site is shown as having a low liquefaction hazard. Based on the soil types and relative density of site soils encountered in our explorations, our current opinion is that the risk of structurally damaging liquefaction settlement at the site is low.

Subsequently, the risk of structurally damaging lateral spreading is also low.

Beatrice Morrow Cannady Elementary School

4 CONSTRUCTION RECOMMENDATIONS

Site Preparation

Construction of the proposed structure may involve clearing of the existing grass lawn area and demolition of possible existing structures. Demolition should include removing existing pavement from the proposed structure area. Materials generated during demolition should be transported off site or stockpiled in areas designated by the owner’s representative.

4.1.1 Subgrade Verification

Following site preparation and prior to placing aggregate base over shallow foundation and floor slabs, the exposed subgrade should be evaluated with a steel foundation probe. We recommend that PBS be retained to perform the subgrade verifications. Unsuitable areas identified during the field evaluation should be compacted to a firm condition or be excavated and replaced with structural fill.

4.1.2 Wet/Freezing Weather and Wet Soil Conditions

Due to the presence of fine-grained sands in the near-surface materials at the site, construction equipment may have difficulty operating on the near-surface soils when the moisture content of the surface soil is more than a few percentage points above the optimum moisture required for compaction. Soils disturbed during site preparation activities, or unsuitable areas identified during probing, should be removed and replaced with compacted structural fill.

Site earthwork and subgrade preparation should not be completed during freezing conditions, except for mass excavation to the subgrade design elevations.

4.1.3 Dry Weather Conditions

Clay soils should be covered within 4 hours of exposure by a minimum of 4 inches of crushed rock or plastic sheeting during the dry season. Exposure of these materials should be coordinated with the geotechnical engineer so that the subgrade suitability can be evaluated prior to being covered.

5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS

In most cases, other services beyond completion of a final geotechnical engineering report are necessary or desirable to complete the project. Occasionally, conditions or circumstances arise that require additional work that was not anticipated when the geotechnical report was written. PBS offers a range of environmental, geological, geotechnical, and construction services to suit the varying needs of our clients.

PBS should be retained to review the plans and specifications for this project before they are finalized. Such a review allows us to verify that our recommendations and concerns have been adequately addressed in the design.

Satisfactory earthwork performance depends on the quality of construction. Sufficient observation of the contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. We recommend that PBS be retained to observe footing subgrades.

Subsurface conditions observed during construction should be compared with those encountered during the subsurface explorations. Recognition of changed conditions requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated.

Beatrice Morrow Cannady Elementary School

6 LIMITATIONS

This report has been prepared for the exclusive use of the addressee, and their architects and engineers, for aiding in the design and construction of the proposed development and is not to be relied upon by other parties. It is not to be photographed, photocopied, or similarly reproduced, in total or in part, without express written consent of the client and PBS. It is the addressee's responsibility to provide this report to the appropriate design professionals, building officials, and contractors to ensure correct implementation of the recommendations.

The opinions, comments, and conclusions presented in this report are based upon information derived from our literature review, field explorations, laboratory testing, and engineering analyses. It is possible that soil, rock, or groundwater conditions could vary between or beyond the points explored. If soil, rock, or groundwater conditions are encountered during construction that differ from those described herein, the client is responsible for ensuring that PBS is notified immediately so that we may reevaluate the recommendations of this report.

Unanticipated fill, soil and rock conditions, and seasonal soil moisture and groundwater variations are commonly encountered and cannot be fully determined by merely taking soil samples or completing explorations such as soil borings. Such variations may result in changes to our recommendations and may require additional funds for expenses to attain a properly constructed project; therefore, we recommend a contingency fund to accommodate such potential extra costs.

The scope of work for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site.

If there is a substantial lapse of time between the submission of this report and the start of work at the site, if conditions have changed due to natural causes or construction operations at or adjacent to the site, or if the basic project scheme is significantly modified from that assumed, this report should be reviewed to determine the applicability of the conclusions and recommendations presented herein. Land use, site conditions (both on and off site), or other factors may change over time and could materially affect our findings; therefore, this report should not be relied upon after three years from its issue, or in the event that the site conditions change.

Beatrice Morrow Cannady Elementary School

7 REFERENCES

ASCE. (2016). Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16).

American Society of Civil Engineers.

DOGAMI. (2023). [Interactive Map]. Oregon HazVu: Statewide Geohazards Viewer. Oregon Department of

Geology and Mineral Industries, Earthquake Liquefaction. https://gis.dogami.oregon.gov/maps/hazvu/.

ODOT SS. (2021). Oregon Standard Specifications for Construction. Salem, Oregon. Oregon Department of

Transportation.

OSSC. (2022). Oregon Structural Specialty Code (OSSC). Based on IBC. (2021 International Building Code).

Country Club Hills, IL International Code Council, Inc.

PBS Engineering and Environmental Inc. (2017). Updated Geotechnical Engineering Report, North Clackamas

Elementary School, Damascus, Oregon. Prepared for North Clackamas School District. PBS Project

73316.000 PH0002.

Geotechnical-Engineering Report Important Information about This

Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.

While you cannot eliminate all such risks, you can manage them. The following information is provided to help.

The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer.

Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.

Understand the Geotechnical-Engineering Services Provided for this Report Geotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.

The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations.

Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.

Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific Times Geotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer will not likely meet the needs of a civil-works constructor or even a different civil engineer. Because each geotechnical-engineering study is unique, each geotechnical-engineering report is unique, prepared solely for the client.

Likewise, geotechnical-engineering services are performed for a specific project and purpose. For example, it is unlikely that a geotechnical-engineering study for a refrigerated warehouse will be the same as one prepared for a parking garage; and a few borings drilled during a preliminary study to evaluate site feasibility will not be adequate to develop geotechnical design recommendations for the project.

Do not rely on this report if your geotechnical engineer prepared it:

the original site); or

• before important events occurred at the site or adjacent to it;

e.g., man-made events like construction or environmental remediation, or natural events like floods, droughts, earthquakes, or groundwater fluctuations.

Note, too, the reliability of a geotechnical-engineering report can be affected by the passage of time, because of factors like changed subsurface conditions; new or modified codes, standards, or regulations; or new techniques or tools. If you are the least bit uncertain about the continued reliability of this report, contact your geotechnical engineer before applying the recommendations in it. A minor amount of additional testing or analysis after the passage of time – if any is required at all – could prevent major problems.

Read this Report in Full Costly problems have occurred because those relying on a geotechnical-engineering report did not read the report in its entirety. Do not rely on an executive summary. Do not read selective elements only. Read and refer to the report in full.

You Need to Inform Your Geotechnical Engineer About Change Your geotechnical engineer considered unique, project-specific factors when developing the scope of study behind this report and developing the confirmation-dependent recommendations the report conveys.

Typical changes that could erode the reliability of this report include those that affect:

function or weight of the proposed structure and the desired performance criteria;

As a general rule, always inform your geotechnical engineer of project or site changes – even minor ones – and request an assessment of their impact. The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.

Most of the “Findings” Related in This Report Are Professional Opinions Before construction begins, geotechnical engineers explore a site’s subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from that sampling and testing were reviewed by your geotechnical engineer, who then applied professional judgement to form opinions about subsurface conditions throughout the site. Actual sitewide-subsurface conditions may differ – maybe significantly – from those indicated in this report. Confront that risk by retaining your geotechnical engineer to serve on the design team through project completion to obtain informed guidance quickly, whenever needed.

This Report’s Recommendations Are Confirmation-Dependent The recommendations included in this report – including any options or alternatives – are confirmation-dependent. In other words, they are not final, because the geotechnical engineer who developed them relied heavily on judgement and opinion to do so. Your geotechnical engineer can finalize the recommendations only after observing actual subsurface conditions exposed during construction. If through observation your geotechnical engineer confirms that the conditions assumed to exist actually do exist, the recommendations can be relied upon, assuming no other changes have occurred. The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations if you fail to retain that engineer to perform construction observation.

This Report Could Be Misinterpreted Other design professionals’ misinterpretation of geotechnical-engineering reports has resulted in costly problems. Confront that risk by having your geotechnical engineer serve as a continuing member of the design team, to:

specifications; and

• be available whenever geotechnical-engineering guidance is needed.

You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.

Give Constructors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that “informational purposes” means constructors have no right to rely on the interpretations, opinions, conclusions, or recommendations in the report. Be certain that constructors know they may learn about specific project requirements, including options selected from the report, only from the design drawings and specifications. Remind constructors that they may perform their own studies if they want to, and be sure to allow enough time to permit them to do so. Only then might you be in a position to give constructors the information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Conducting prebid and preconstruction conferences can also be valuable in this respect.

Read Responsibility Provisions Closely Some client representatives, design professionals, and constructors do not realize that geotechnical engineering is far less exact than other engineering disciplines. This happens in part because soil and rock on project sites are typically heterogeneous and not manufactured materials with well-defined engineering properties like steel and concrete. That lack of understanding has nurtured unrealistic expectations that have resulted in disappointments, delays, cost overruns, claims, and disputes.

To confront that risk, geotechnical engineers commonly include explanatory provisions in their reports. Sometimes labeled “limitations,” many of these provisions indicate where geotechnical engineers’ responsibilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions.

Your geotechnical engineer should respond fully and frankly.

Geoenvironmental Concerns Are Not Covered The personnel, equipment, and techniques used to perform an environmental study – e.g., a “phase-one” or “phase-two” environmental site assessment – differ significantly from those used to perform a geotechnical-engineering study. For that reason, a geotechnical-engineering report does not usually provide environmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated subsurface environmental problems have led to project failures. If you have not obtained your own environmental information about the project site, ask your geotechnical consultant for a recommendation on how to find environmental risk-management guidance.

Obtain Professional Assistance to Deal with Moisture Infiltration and Mold While your geotechnical engineer may have addressed groundwater, water infiltration, or similar issues in this report, the engineer’s services were not designed, conducted, or intended to prevent migration of moisture – including water vapor – from the soil through building slabs and walls and into the building interior, where it can cause mold growth and material-performance deficiencies.

Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by including building-envelope or mold specialists on the design team.

Geotechnical engineers are not building-envelope or mold specialists.

Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind.

Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation.

Telephone: 301/565-2733 e-mail: info@geoprofessional.org www.geoprofessional.org

Figures

FIGURE

JAN 2024

73316.022

LATERAL SURCHARGE DETAIL

BEATRICE MORROW CANNADY ES PORTABLES

HAPPY VALLEY, OREGON

Appendix A Field Explorations

Beatrice Morrow Cannady Elementary School

A-1

Appendix A: Field Explorations

A1 GENERAL

PBS explored subsurface conditions at the project site by advancing three borings to depths of up to approximately 16.5 feet bgs on December 21, 2023. The approximate locations of the explorations are shown on Figure 2, Site Plan. The procedures used to advance the borings, collect samples, and other field techniques are described in detail in the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed engineering practices in general accordance with relevant ASTM procedures. “General accordance” means that certain local drilling/excavation and descriptive practices and methodologies have been followed.

A2 BORINGS

A2.1 Drilling

Borings were advanced using a trailer-mounted Little Beaver drill rig provided and operated by Dan J. Fisher

Excavating, Inc., of Forest Grove, Oregon, using solid-stem drilling techniques. The borings were observed by a member of the PBS geotechnical staff, who maintained a detailed log of the subsurface conditions and materials encountered during the course of the work.

A2.2 Sampling

Disturbed soil samples were taken in the borings at selected depth intervals. The samples were obtained using a standard 2-inch outside diameter, split-spoon sampler following procedures prescribed for the standard penetration test (SPT). Using the SPT, the sampler is driven 18 inches into the soil using a 140-pound hammer dropped 30 inches. The number of blows required to drive the sampler the last 12 inches is defined as the standard penetration resistance (N-value). The N-value provides a measure of the relative density of granular soils such as sands and gravels, and the consistency of cohesive soils such as clays and plastic silts. The disturbed soil samples were examined by a member of the PBS geotechnical staff and then sealed in plastic bags for further examination and physical testing in our laboratory.

A2.3 Boring Logs

The boring logs show the various types of materials that were encountered in the borings and the depths where the materials and/or characteristics of these materials changed, although the changes may be gradual.

Where material types and descriptions changed between samples, the contacts were interpreted. The types of samples taken during drilling, along with their sample identification number, are shown to the right of the classification of materials. The N-values and natural water (moisture) contents are shown farther to the right.

A3 MATERIAL DESCRIPTION

Initially, samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity, and other distinguishing characteristics of the soil samples were noted. Afterward, the samples were reexamined in the PBS laboratory, various standard classification tests were conducted, and the field classifications were modified where necessary. The terminology used in the soil classifications and other modifiers are defined in Table A-1, Terminology Used to Describe Soil.

Table A-1

Terminology Used to Describe Soil

Soil Descriptions

Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based on total dry weight, is the primary soil type and is capitalized in our log descriptions (SAND, GRAVEL, SILT, or CLAY). Smaller percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the

ASTM D2488-06 Visual-Manual Procedure. “General Accordance” means that certain local and common descriptive practices may have been followed. In accordance with ASTM D2488-06, group symbols (such as GP or CH) are applied on the portion of soil passing the 3-inch (75mm) sieve based on visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils.

Fine-Grained Soils (50% or greater fines passing 0.075 mm, No. 200 sieve)

The primary soil type, i.e., SILT or CLAY is designated through visual-manual procedures to evaluate soil toughness, dilatency, dry strength, and plasticity. The following outlines the terminology used to describe fine-grained soils, and varies from ASTM

D2488 terminology in the use of some common terms.

Primary soil NAME, Symbols, and Adjectives Plasticity

Description

Plasticity

Index (PI)

SILT (ML & MH) CLAY (CL & CH) ORGANIC SOIL (OL & OH)

SILT Organic SILT Non-plastic 0 – 3

SILT Organic SILT Low plasticity 4 – 10

SILT/Elastic SILT Lean CLAY Organic SILT/ Organic CLAY Medium Plasticity 10 – 20

Elastic SILT Lean/Fat CLAY Organic CLAY High Plasticity 20 – 40

Elastic SILT Fat CLAY Organic CLAY Very Plastic >40

Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:

Description % Composition

With Sand % Sand ≥ % Gravel 15% to 25% plus No. 200

With Gravel % Sand < % Gravel

Sandy % Sand ≥ % Gravel ≤30% to 50% plus No. 200

Gravelly

% Sand < % Gravel

Borderline Symbols, for example CH/MH, are used when soils are not distinctly in one category or when variable soil units contain more than one soil type. Dual Symbols, for example CL-ML, are used when two symbols are required in accordance with ASTM D2488.

Soil Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 7). Descriptive terms are based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows. SILT soils with low to non-plastic behavior (i.e., PI < 7) may be classified using relative density.

Consistency

Term SPT N-value

Unconfined Compressive Strength tsf kPa

Very soft Less than 2 Less than 0.25 Less than 24

Soft 2 – 4 0.25 – 0.5 24 – 48

Medium stiff 5 – 8 0.5 – 1.0 48 – 96

Stiff 9 – 15 1.0 – 2.0 96 – 192

Very stiff 16 – 30 2.0 – 4.0 192 – 383

Hard Over 30 Over 4.0 Over 383

Table A-1

Terminology Used to Describe Soil

Soil Descriptions

Coarse - Grained Soils (less than 50% fines)

Coarse-grained soil descriptions, i.e., SAND or GRAVEL, are based on the portion of materials passing a 3-inch (75mm) sieve.

Coarse-grained soil group symbols are applied in accordance with ASTM D2488-06 based on the degree of grading, or distribution of grain sizes of the soil. For example, well-graded sand containing a wide range of grain sizes is designated SW;

poorly graded gravel, GP, contains high percentages of only certain grain sizes. Terms applied to grain sizes follow.

Material NAME Particle Diameter

Inches Millimeters

SAND (SW or SP) 0.003 – 0.19 0.075 – 4.8

GRAVEL (GW or GP) 0.19 – 3 4.8 – 75

Additional Constituents:

Cobble 3 – 12 75 – 300

Boulder 12 – 120 300 – 3050

The primary soil type is capitalized, and the fines content in the soil are described as indicated by the following examples.

Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 percent. Other soil mixtures will have similar descriptive names.

Example: Coarse-Grained Soil Descriptions with Fines

>5% to < 15% fines (Dual Symbols) ≥15% to < 50% fines

Well graded GRAVEL with silt: GW-GM Silty GRAVEL: GM

Poorly graded SAND with clay: SP-SC Silty SAND: SM

Additional descriptive terminology applied to coarse-grained soils follow.

Example: Coarse-Grained Soil Descriptions with Other Coarse-Grained Constituents

Coarse-Grained Soil Containing Secondary Constituents

With sand or with gravel ≥ 15% sand or gravel

With cobbles; with boulders Any amount of cobbles or boulders.

Cobble and boulder deposits may include a description of the matrix soils, as defined above.

Relative Density terms are applied to granular, non-plastic soils based on direct measure or correlation to the Standard

Penetration Test N-value as determined by ASTM D1586-84.

Relative Density Term SPT N-value

Very loose 0 – 4

Loose 5 – 10

Medium dense 11 – 30

Dense 31 – 50

Very dense > 50

SAMPLING DESCRIPTIONS

Table A-2

Key To Test Pit and Boring Log Symbols S P T D ri ve

S am p le r

S ta n d ar d P e n e tr at io n T e st

A

T M

D

S h e lb y T u b e P u sh

S am p le

T M

D

S p e ci al iz e d D ri ve

S am p le rs

(D e ta ils N o te d o n L o g s)

S p e ci al iz e d D ri ll o r

P u sh am p le r (D e ta ils N o te d o n

Lo g s)

G ra b S am p le

R o ck

C o ri n g I n te rv al

S cr e

(W at e r o r

A ir S a m p lin

W at e r

Le ve l D u ri

D ri lli n g /E xc av at io n W at e r

Le ve l A ft ri lli n g /E xc av at io

LOG GRAPHICS

PP Pocket Penetrometer HYD Hydrometer Gradation

TOR Torvane SIEV Sieve Gradation

DCP DS Direct Shear

ATT Atterberg Limits DD Dry Density

PL Plasticity Limit CBR California Bearing Ratio

LL Liquid Limit RES Resilient Modulus

PI Plasticity Index VS Vane Shear

P200 Percent Passing US Standard No. 200 Sieve bgs Below ground surface

OC Organic Content MSL Mean Sea Level

CON Consolidation HCL Hydrochloric Acid

UC Unconfined Compressive Strength

Details of soil and rock classification systems are available on request. Rev. 02/2017

Dynamic Cone Penetrometer

Geotechnical Testing Acronym Explanations

Lithology Boundary:

separates distinct units

(i.e., Fill, Alluvium, Bedrock) at approximate depths inciated

Sampler

Type

Sample

Recovery Sample

Interval

Instrumentation Detail Sampling Symbols Soil and Rock

Well Pipe

Piezometer

Piezometer

Ground Surface

Well Cap

Bottom of Hole

S o il o r R o ck

T y p e s

Well Seal

Well Screen

Soil-type or Material-type

Change Boundary: separates soil and material changes within the same lithographic unit at approximate depth indicated

0.0

0.4

1.5

16.5

P200 = 90%

LL = 52

PL = 20

PI = 32

ASPHALT (5 inches) CRUSHED ROCK BASE (13 inches)

Medium stiff, brown to gray, fat CLAY (CH) with sand; medium plasticity; fine sand; moist becomes stiff becomes medium stiff; high plasticity becomes very stiff; low plasticity

Final depth 16.5 feet bgs; boring backfilled with bentonite and surface patched with AC cold patch. Groundwater not encountered at time of exploration.

P200

ATT

D E

P T

H INSTALLATION AND

COMMENTS

0 50 100

CORE REC%RQD%

MOISTURE CONTENT %

DYNAMIC CONE

PENETROMETER

UNCORRECTED N-VALUE

B

O R

IN

G

L O

G

6.

2_ B

1- 3_

.G P

J P

B S

_D A

T A

T M

P L_

G E

O .G

T

P R

IN

T

D A

T E

1/

9/

:R P

G

G R

A P

H

IC

LO

G

DRILLED BY: Dan J. Fischer Excavating, Inc.

LOGGED BY: B. Ackerman

DRILLING METHOD: Solid-Stem Auger

MATERIAL DESCRIPTION

S A

M P

LE

T

Y

E

M P

LE

ID

BORING B-1

T E

S T

IN

G

DEPTH

FEET

(See Site Plan)

APPROX. BORING B-1 LOCATION:

FIGURE A1HAMMER EFFICIENCY PERCENT: 60

BIT DIAMETER: 4 inches

BEATRICE MORROW CANNADAY ES

HAPPY VALLEY, OREGON

PBS PROJECT NUMBER:

73316.022

NOTE: Lines representing the interface between soil/rock units of differing description are approximate only, inferred where between samples, and may indicate gradual transition.

Surface Conditions: Asphalt

LOGGING COMPLETED: 12/21/2023

Long: -122.47701Lat: 45.43078

S -1

S -2

S -3

S -4

S -5

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0 50 100

0.4

1.5

16.5

12/21/23

12/21/23

ASPHALT (5 inches) CRUSHED ROCK BASE (13 inches)

Stiff, light brown to red-brown, fat CLAY (CH) with sand; medium to high plasticity; fine sand;

moist becomes medium stiff, light brown to gray-blue becomes stiff becomes medium stiff

Final depth 16.5 feet bgs; boring backfilled with bentonite and surface patched with AC cold patch.

D E

P T

H INSTALLATION AND

COMMENTS

0 50 100

CORE REC%RQD%

MOISTURE CONTENT %

DYNAMIC CONE

PENETROMETER

UNCORRECTED N-VALUE

B

O R

IN

G

L

6.

2_ B

1- 3_

.G P

J P

B S

_D A

T A

T M

P L_

G E

O .G

IN

T

D A

T E

1/

9/

:R P

G

G R

A P

H

IC

LO

G

DRILLED BY: Dan J. Fischer Excavating, Inc.

LOGGED BY: B. Ackerman

DRILLING METHOD: Solid-Stem Auger

MATERIAL DESCRIPTION

S A

M P

LE

T

Y

M P

LE

ID

BORING B-2

T E

S T

IN

G

DEPTH

FEET

(See Site Plan)

APPROX. BORING B-2 LOCATION:

FIGURE A2HAMMER EFFICIENCY PERCENT: 60

BIT DIAMETER: 4 inches

BEATRICE MORROW CANNADAY ES

HAPPY VALLEY, OREGON

PBS PROJECT NUMBER:

73316.022

NOTE: Lines representing the interface between soil/rock units of differing description are approximate only, inferred where between samples, and may indicate gradual transition.

Surface Conditions: Asphalt

LOGGING COMPLETED: 12/21/2023

Long: -122.47724Lat: 45.43076

S -1

S -2

S -3

S -4

S -5

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0 50 100

0.3

1.0

7.5

16.5

12/21/23

P200 = 84%

No recovery

ASPHALT (3 inches) CRUSHED ROCK BASE (9 inches)

Stiff, brown to red-brown, fat CLAY (CH) with sand; medium to high plasticity; fine sand;

moist becomes medium stiff

Medium stiff, brown to red-brown, sandy fat CLAY (CH) with trace gravel; medium plasticity;

fine sand; fine, subangular gravel; wet becomes stiff, with decreased sand

Final depth 16.5 feet bgs; boring backfilled with bentonite and surface patched with AC cold patch.

P200

D E

P T

H INSTALLATION AND

COMMENTS

0 50 100

CORE REC%RQD%

MOISTURE CONTENT %

DYNAMIC CONE

PENETROMETER

UNCORRECTED N-VALUE

B

O R

IN

G

L

6.

2_ B

1- 3_

.G P

J P

B S

_D A

T A

T M

P L_

G E

O .G

IN

T

D A

T E

1/

9/

:R P

G

G R

A P

H

IC

LO

G

DRILLED BY: Dan J. Fischer Excavating, Inc.

LOGGED BY: B. Ackerman

DRILLING METHOD: Solid-Stem Auger

MATERIAL DESCRIPTION

S A

M P

LE

T

Y

M P

LE

ID

BORING B-3

T E

S T

IN

G

DEPTH

FEET

(See Site Plan)

APPROX. BORING B-3 LOCATION:

FIGURE A3HAMMER EFFICIENCY PERCENT: 60

BIT DIAMETER: 4 inches

BEATRICE MORROW CANNADAY ES

HAPPY VALLEY, OREGON

PBS PROJECT NUMBER:

73316.022

NOTE: Lines representing the interface between soil/rock units of differing description are approximate only, inferred where between samples, and may indicate gradual transition.

Surface Conditions: Asphalt

LOGGING COMPLETED: 12/21/2023

Long: -122.47724Lat: 45.43069

S -1

S -2

S -3

S -4

S -5

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0 50 100

Appendix B Laboratory Testing

Beatrice Morrow Cannady Elementary School

B-1

Appendix B: Laboratory Testing

B1 GENERAL

Samples obtained during the field explorations were examined in the PBS laboratory. The physical characteristics of the samples were noted and field classifications were modified where necessary. During the course of examination, representative samples were selected for further testing.