00002504 Addendum 6 REVISED.pdf

Procurement Services City of Portland, Oregon

@PortlandGov portlandgov

PortlandORGov

March 20, 2025

ADDENDUM NUMBER 6 - REVISED

RFQ Number 00002504

North Portland Aquatic Center Construction Manager/General Contractor (CM/GC)

Responses Due: March 27, 2025, by 2:00 P.M.

This addendum provides changes to the plans and specifications for the above-entitled project to be considered by each Responder. This addendum shall be included in the Response and, when closing the contract, will be a part thereof. Any changes made by this addendum to said plans and specifications offset only the portion of the plans, words or paragraphs specifically mentioned herein, and the balance of the plans and/or specifications remain in full force. It is the responsibility of all Responders to conform to this addendum.

Item No. Location Change

6.01 Q&A Question: Has a Geotechnical Report for the site been completed, and is it available?

Answer: Geotechnical evaluation of the site is on-going. Attached are the Phase I Preliminary Report and the Phase I Borings Geotechnical Report that we can share for reference. The Phase II Geotechnical Report will be completed after the preferred schematic design is finalized.

6.02 Q&A Question: Would a firm be disqualified if its submission does not include completed or in-progress natatorium projects of $15 million in the past 10 years? Is there flexibility in the qualification criteria to allow firms with relevant large-scale public project experience to compete, fostering a more equitable entry point into this specialized scope?

Answer: No, a firm will not be disqualified.

6.03 Q&A Question: Is the project’s sustainability goal confirmed as Living Building Challenge (LBC) certification?

Answer: The City’s Green Building Policy requires projects of this size to “Register and certify for the US Green Building Council's Leadership in Energy and Environmental Design (LEED) Building Design and Construction (BD+C) at the Gold level and/or achieve Living Building Challenge (LBC) status.” The project is still in the

Sylvester Donelson, Jr. Sara Morrissey Michael Jordan Chief Procurement Officer Deputy City Administrator City Administrator https://twitter.com/PortlandGov https://www.instagram.com/PortlandGov/ https://www.facebook.com/PortlandORGov

Item No. Location Change preliminary design phases and has not confirmed if LEED or LBC will be the path for compliance with the Green Building Policy. For more information, visit https://www.portland.gov/policies/environment-built/green-building/enb-901-green-building-policy.

END OF ADDENDUM

Attachments: Phase I Preliminary Report Phase I Borings Geotechnical Report

Please direct all questions and concerns to Valentine Hellman, at valentine.hellman@portlandoregon.gov.

Sincerely, Sylvester Donelson, Jr.

Chief Procurement Officer sd: veh https://www.portland.gov/policies/environment-built/green-building/enb-901-green-building-policy https://www.portland.gov/policies/environment-built/green-building/enb-901-green-building-policy

M E M O R A N D U M

To: Susan Vutz, AIA, LEED AP, DBIA / ELS Architecture and Urban Design

Date: August 10, 2023

GRI Project No.: 6732-A

From: Brian J. Bayne, PE, and Nathan M. Villeneuve, CEG

Re: Preliminary Design Recommendations Impacts to Existing City of Portland Sewer Line Northgate Park 9420 N Geneva Avenue Portland, Oregon

At your request, GRI is conducting a preliminary geotechnical investigation for the proposed aquatic center to be constructed at Northgate Park in Portland, Oregon. Our field investigation was recently completed, and we are in the process of completing the laboratory testing and engineering analysis for the project. This memorandum provides our preliminary conclusions and recommendations regarding seismic considerations, foundation support, and potential impacts of the planned improvements to the City of Portland’s (COP) existing sewer line that crosses the park from near the southwest corner to the northeast corner of the site.

PROJECT DESCRIPTION

Portland Parks and Recreation (PP&R) is planning to construct a new aquatic center at Northgate Park in north Portland, Oregon. The final configuration and amenities within the facility have not yet been finalized but will likely include two indoor pools, locker rooms, a multipurpose room, lobby, a mechanical room, a storage rooms, and spectator seating. In addition, a parking lot will likely be constructed adjacent to the facility. Per conversation with KPFF Consulting Engineers, the project’s structural engineer, the maximum column and wall loads are 120 kips and 4 kips per foot (kips/foot), respectively. Excavations to construct the improvements are estimated to be less than 15 feet deep, and we anticipate minimal new fills will be required.

PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS

Seismic Considerations We anticipate that the seismic design for the project will be in accordance with the 2022 Oregon Structural Specialty Code (OSSC), which is based on the International Building Code (IBC).

Seismic design in accordance with the 2022 OSSC is based on ASCE Documents 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16). The ASCE design methodology uses two spectral response acceleration parameters, SS and S1, DRAFT

GRI 6732-A – N. Portland Aquatic Center Preliminary Considerations Memorandum Page 2 August 10, 2023 corresponding to periods of about 0.2 seconds and 1.0 seconds, to develop the Risk-Targeted Maximum Considered Earthquake (MCER) response spectrum for Site Class B/C or bedrock conditions. For the site located at the approximate latitude and longitude coordinates of 45.5908° N and 122.7261° W, the SS and S1 parameters are 0.87 g and 0.40 g, respectively. To establish the ground-surface MCER spectrum, these bedrock spectral parameters are adjusted for soil site class using the short- and long-period site coefficients, Fa and Fv. The design-level response spectrum is calculated as two-thirds of the ground-surface MCER spectrum.

This project falls under Oregon Administrative Rule ORS 455.447 as a special occupancy structure and will require the completion of a site-specific seismic hazard study. The site-specific study is not part of our current scope of work and will be completed as part of the final design for the project during a later phase.

For preliminary design, based on the results of the recent explorations completed for this project, the soil profile at the site is representative of Site Class D, or a stiff-soil site. Due to the S1 acceleration parameter being greater than or equal to 0.2 g, Section 11.4.8 of ASCE 7-16 requires a site-specific ground-motion analysis unless the seismic response coefficient Cs is determined in accordance with Exception 2 of Section 11.4.8 of ASCE 7-16. Assuming the seismic response coefficient Cs is determined in accordance with Exception 2 of Section 11.4.8 of ASCE 7-16, the published site coefficients Fa and Fv are 1.11 and 1.90, respectively, in accordance with Section 11.4 of ASCE 7-16. The design-level response spectrum is calculated as two-thirds of the ground-surface MCER spectrum. We recommend the project structural engineer evaluate the seismic parameters and structural period based on the requirements of Sections 11.4.8 and 12.8 of ASCE 7-16 for this preliminary phase of the project.

The recommended MCER- and design-level spectral response parameters for Site Class D conditions are provided in the table below.

GRI 6732-A – N. Portland Aquatic Center Preliminary Considerations Memorandum Page 3 August 10, 2023

Table 1: RECOMMENDED SEISMIC DESIGN PARAMETERS (2018 IBC/2022 OSSC)

Seismic Parameter Recommended Value

Site Class D

MCER 0.2-Sec Period Spectral Response Acceleration, SMS

1.00 g

MCER 1.0-Sec Period Spectral Response Acceleration, SM1

0.76 g*

Design-Level 0.2-Sec Period Spectral Response Acceleration, SDS

0.68 g

Design-Level 1.0-Sec Period Spectral Response Acceleration, SD1

0.51 g*

Notes:

Exception 2 of Section 11.4.8 should be considered when evaluating base shear calculations in Section 12.8.

The SD1 value is intended only for calculating Ts.

*This value is not intended to be used in design.

Based on our recent explorations, it is our opinion that the risk of liquefaction and/or significant cyclic softening of the soils below the groundwater level at the site is low during a code-based seismic event. Based on site topography, the risk of earthquake-induced slope instability and/or lateral spreading is low. Based on the proximity of the site to mapped active faults, the risk of damage from ground rupture, landslides, settlement, and subsidence at this site is low. The risk of tsunamis and/or seiches is absent.

Foundation Support The maximum column and wall loads for the project will be less than 120 kips and 4 kips/foot, respectively. In our opinion, foundation support for the building can be provided by conventional column-type and continuous wall footings founded in the underlying firm, native soils and designed using an allowable bearing value of up to 2,500 psf. This value applies to the total of dead load and/or frequently applied live loads and can be increased by one-half for the total of all loads: dead, live, and wind or seismic.

We recommend establishing all footings in firm, undisturbed native soil or compacted structural fill at a minimum depth of 1.5 feet below the lowest adjacent finished grade. The footing width should not be less than 18 inches and 24 inches for wall and column footings, respectively.

Excavations for all foundations should be made with a smooth-edge bucket, and all footing excavations should be observed by a qualified geotechnical engineer. Soft or otherwise unsuitable material encountered at foundation subgrade level should be overexcavated and backfilled with granular structural fill.

GRI 6732-A – N. Portland Aquatic Center Preliminary Considerations Memorandum Page 4 August 10, 2023

We estimate the total settlement of spread footings design in accordance with the recommendations presented above will be less than 1 inch. Differential settlements between adjacent comparably loaded footings should be less than half the total settlement. Our experience indicates these settlements will occur rapidly, with the majority of the settlement occurring during construction.

COP Sewer Line Considerations for Construction It is our understanding that an existing COP sewer line crosses Northgate Park from near the southwest to the northeast corners of the park. Based on available documentation provided by the design team, the existing sewer line has a diameter of 72 inches and is located approximately 56 feet below the existing ground surface where it crosses Northgate Park. The final configuration and location of the planned park improvements have not been finalized at this time, and there is the potential that a portion of the new building may be constructed above the existing sewer line. As previously indicated, maximum wall and column loads for the project will be less than 120 kips and 4 kips/foot, respectively, and can be supported on spread footings.

In addition, maximum excavations planned for the project will be less than 15 feet. Based on the depth of the COP sewer line, the maximum excavation depth for the project, the maximum column and wall loading for the project, and foundation support for the building will be provided by spread footings, it is our opinion that the planned improvements will have a negligible impact on the existing sewer line based on geotechnical considerations.

LIMITATIONS

The preliminary information provided in this memorandum is for planning purposes only and is not intended for final design of the project. Additional details regarding site conditions and recommendations for design and construction of the proposed improvements will be provided in our forthcoming preliminary geotechnical report.

We have included the Geoprofessional Business Association (GBA) guidance document “Important Information about This Geotechnical-Engineering Report/Geoenvironmental Report” to assist you and others in understanding the use and limitations of this report, included as Appendix A. We recommend you read this document.

GRI 6732-A – N. Portland Aquatic Center Preliminary Considerations Memorandum Page 5 August 10, 2023

Submitted for GRI, Brian J. Bayne, PE Nathan M. Villeneuve, CEG Associate Project Geologist

6732-A PRELIMARY GEOTECHNICAL CONSIDERATIONS MEMORANDUM

Enclosures: Appendix A, Geoprofessional Business Association Guidance Document

This document has been submitted electronically.

GRI 6732-A – N. Portland Aquatic Center Preliminary Considerations Memorandum August 10, 2023

APPENDIX A

Geoprofessional Business Association Guidance Document

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

Preliminary

Geotechnical Investigation North Portland Aquatic Center

Northgate Park

9420 N Geneva Avenue Portland, Oregon

September 5, 2023

Prepared for ELS Architecture and Urban Design

2040 Addison St Berkeley, California

Prepared by

16520 SW Upper Boones Ferry Road, Suite 100 Tigard, Oregon 97224

(503) 641-3478 | www.gri.com

GRI 6732-A – North Portland Aquatic Center Geotechnical Report September 5, 2023

TABLE OF CONTENTS

1 PROJECT DESCRIPTION

2 SITE DESCRIPTION

2.1 Site Conditions and Topography

2.2 Geology

2.3 Previous Development

3 SUBSURFACE CONDITIONS

3.1 General

3.2 Soils

3.3 Groundwater

4 CONCLUSIONS AND RECOMMENDATIONS

4.1 General

4.2 Seismic Considerations

4.3 Earthwork

4.4 Excavation and Shoring

4.5 Structural Fill

4.6 Foundation Support

4.7 Subdrainage/Floor Support/Swimming Pool Floor

4.8 Retaining Walls

4.9 Sewer Line and Sinkhole Considerations for Construction

4.10 Pavement Design

5 LIMITATIONS

6 REFERENCES

TABLES

Table 4-1: Recommended Seismic Design Parameters (2018 IBC/2022 OSSC) Table 4-2: Pavement Section Summary

FIGURES

Figure 1: Vicinity Map Figure 2: Site Plan Figure 3: Surcharge-Induced Lateral Pressure Figure 4: Typical Subdrainage Detail Figure 5: Surcharge-Induced Lateral Pressure

APPENDICES

Appendix A: Field Explorations and Laboratory Testing Appendix B: Sewer Line As-Built Appendix C: Geoprofessional Business Association Guidance Document

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 1 September 5, 2023

As requested, GRI completed a preliminary geotechnical investigation for the North Portland Aquatic Center (NPAC) project planned at Northgate Park in Portland, Oregon.

The Vicinity Map, Figure 1, shows the general location of the site. The purpose of our investigation was to evaluate subsurface conditions at the site and develop preliminary geotechnical recommendations to support Task 4: Preferred Site - Preliminary Schematic Design. The investigation included a review of available existing geotechnical information for the site and surrounding areas, subsurface explorations, laboratory testing, and engineering analyses. This report describes the work accomplished and provides conclusions and recommendations for use in the schematic design of the proposed project.

The following geotechnical report was provided by PP&R and reviewed by GRI:

• Geotechnics, LLC, 2021, Report of Geotechnical Services – Northgate Park Pathways

– Project No. 20-004-1

1 PROJECT DESCRIPTION

The Portland Parks and Recreation Department (PP&R) is planning to construct a new aquatic center within the footprint of the existing Northgate Park. The final configuration and amenities within the facility have not yet been finalized but will likely include two indoor pools, locker rooms, a multipurpose room, a lobby, a mechanical room, storage rooms, and spectator seating. In addition, a parking lot or lots will likely be constructed adjacent to the facility. Per conversation with KPFF Consulting Engineers, the project’s structural engineer, the maximum column and wall loads are 120 kips and 4 kips per foot (kips/foot), respectively. Excavations to construct the improvements are estimated to be less than 15 feet deep, and we anticipate minimal new fills will be required.

We anticipate the structure will be designed in accordance with the 2022 Oregon Structural Specialty Code (OSSC), which is based on the International Building Code (IBC).

Seismic design in these codes references the 2016 American Society of Civil Engineers (ASCE) 7-16 document, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16). This project falls under Oregon Administrative Rule ORS

455.447 as a special occupancy structure and will require the completion of a site-specific seismic hazard study. The site-specific study is not part of our current scope of work and will be completed as part of the final design for the project during a later phase.

We anticipate the majority of the parking lot and access roadways will be paved with asphalt concrete (AC) pavement; however, areas subjected to repeated heavy-truck traffic, such as trash-enclosure and service areas, may be paved with portland cement concrete (PCC) pavement.

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 2 September 5, 2023

2 SITE DESCRIPTION

2.1 Site Conditions and Topography

The proposed NPAC building site will be located within the existing Northgate Park. As shown on the Site Plan, Figure 2, the park is bordered by N Fessenden Street to the north, the Clarendon Regional Academy building to the east, residential homes and streets to the south, and N Geneva Avenue to the west. The park consists primarily of a maintained grass field, surrounded by a border of trees to the north, east, and west. An existing parking lot is situated within the trees on the west side of the park, adjacent to N Geneva Avenue.

The south side of the park includes a play structure and other smaller park buildings and structures. Review of aerial imagery and topographic information indicates the site is generally flat with a very gentle slope to the northeast. Elevations range from 111 feet in the southwest corner to about 95 feet in the northeast corner. Unless noted otherwise, all elevations in this report reference the North American Vertical Datum of 1988 (NAVD 88).

2.2 Geology

Published geologic mapping indicates the site is mantled by coarse-grained Missoula Flood deposits consisting of silt, sand, gravel, and cobbles. (Beeson and others, 1991). In Portland, coarse-grained Missoula Flood deposits are often overlain by a layer of fine-grained Missoula Flood deposits consisting of clay, silt, and fine-grained sand.

2.3 Previous Development

GRI reviewed publicly available historical information, including topographic maps, aerial imagery, and Sanborn insurance maps. Topographic maps dating to 1897 indicate some residential streets and limited buildings in the area. Aerial imagery from the 1950s shows twelve long and narrow buildings occupying the area of the park. It is not uncommon for these buildings to have basements and other below-grade structures that were abandoned in place. Imagery from 1955 shows an empty lot, and imagery from 1960 to the present shows various sports field and park configurations without any major development.

A COP Bureau of Environmental Services (BES) sewer pipe crosses the park diagonally through the northeast and southwest corners. Based on as-built drawings, the sewer is approximately 56 feet below the surface of the park and consists of a 72-inch-diameter pipe or tunnel built in 1967. A review of City of Portland Maps Sewer Assets website shows numerous existing and abandoned sewer lines within the property. The sewer lines extend from the southern property line to the northern property line at N Fessenden Street.

A sinkhole appeared in the park in 2009, and limited information was documented in reporting by the Oregonian and KATU News. PP&R does not have any documentation of the sinkhole on file. According to the articles, the sinkhole measured approximately 20 feet

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 3 September 5, 2023 to 30 feet wide and measured about 1 foot deep near the edges and up to 20 feet deep at the center. The KATU article indicates the sinkhole was filled with gravel and other materials. The KATU article also mentions another sinkhole that occurred about 10 years prior to 2009 but does not include additional information.

3 SUBSURFACE CONDITIONS

3.1 General

Subsurface materials and conditions at the site were investigated between July 12 and 14, 2023, with three borings, designated B-1 through B-3. The approximate locations of the explorations are shown on Figure 2. The borings were advanced to depths ranging from

76.5 feet to 101.5 feet.

A discussion of the field and laboratory testing programs completed for this investigation is provided in Appendix A. Logs of the borings are provided on Figures 1A through 3A.

The terms and symbols used to describe the soil encountered in the explorations are defined in Table 1A and on the attached legend.

3.2 Soils

For the purpose of discussion, the soils disclosed by the explorations have been grouped into the following categories based on their physical characteristics and engineering properties:

a. TOPSOIL

b. SILT (Missoula Flood Deposits: Fine-Grained Facies / Possible Fill)

c. SAND and Silty SAND (Missoula Flood Deposits: Coarse-Grained Facies)

The following paragraphs provide a description of the soil units encountered in the explorations completed by GRI for this investigation and a discussion of the groundwater conditions at the site.

a. TOPSOIL All borings were advanced in existing grass fields and encountered approximately 6 inches of topsoil consisting of heavily rooted silt with varying amounts of sand.

b. SILT (Missoula Flood Deposits: Fine-Grained Facies / Possible Fill) Silt interpreted to be Missoula Flood Deposits (fine-grained facies), or possible fill was encountered in each of the borings beneath the topsoil, extending to depths ranging from about 5 feet to 8 feet. The unit consists of brown silt with varying amounts of fine-grained sand, ranging from a trace to some sand. Based on SPT N-values, the relative consistency of the silt ranges from medium stiff to stiff. Based on the historical development at the park, portions of this unit may be reworked fill.

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 4 September 5, 2023

Consolidation testing was conducted on the silt at a depth of about 6.5 feet in boring B-1.

The test results indicate the silt is overconsolidated and exhibits low compressibility in the preconsolidated range of pressures and high compressibility in the normally consolidated range of pressures (see Figure 4A).

c. SAND and Silty SAND (Missoula Flood Deposits: Coarse-Grained Facies) Sand interpreted to be Missoula Flood Deposits (coarse-grained facies) was encountered beneath the silt in each boring and extending to depths ranging from about 76.5 feet to

101.5 feet, the maximum depth explored in the borings. The unit typically consists of sand, with varying amounts of silt and gravel ranging from a trace of silt to silty and up to a trace of gravel. A 5-foot-thick layer of gravel with some fine- to coarse- grained sand was encountered in B-1 at a depth of 80 feet. Cobbles were interpreted to be contained within the unit based on drill action. Based on SPT N-values, the relative density of the sand ranges from medium dense to very dense.

3.3 Groundwater

The borings were advanced using mud-rotary drilling techniques, which do not allow for the direct measurement of groundwater levels. Based on nearby well logs and published information provided by the U.S. Geological Survey, the estimated depth to the regional groundwater level across the site ranges from about 90 feet to 100 feet below the ground surface across site elevation changes (Snyder, 2008). However, localized perched-groundwater conditions may occur at shallower depths in the near-surface silt soils during periods of heavy or prolonged rainfall or following irrigation of the fields.

4 CONCLUSIONS AND RECOMMENDATIONS

4.1 General

Subsurface explorations completed for this investigation indicate the site is typically mantled with silt underlain by medium-dense to very-dense sand. We anticipate regional groundwater is typically encountered at depths on the order of 90 feet to 100 feet;

however, shallow perched groundwater can occur during periods of heavy or prolonged rainfall or site irrigation.

The site has previously been developed with numerous residential buildings. It is not uncommon to encounter fill soils used to backfill below-grade structures associated with these buildings.

In our opinion, foundation support for new structural loads can be provided for the new building by conventional column- and wall-type spread footings established in firm, undisturbed native soil or compacted structural fill. The primary geotechnical considerations associated with construction of the proposed improvements include the potential presence of fine-grained soils that are moisture sensitive, the presence of

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 5 September 5, 2023 undocumented fill, and potential for sinkholes at the project site that may develop over abandoned structures and/or utilities. The following sections of this report provide our conclusions and recommendations for use in the design and construction of the project.

4.2 Seismic Considerations

The ASCE design methodology uses two spectral response acceleration parameters, SS and S1, corresponding to periods of about 0.2 seconds and 1.0 seconds, to develop the Risk- Targeted Maximum Considered Earthquake (MCER) response spectrum for Site Class B/C or bedrock conditions. For the site located at the approximate latitude and longitude coordinates of 45.5908° N and 122.7261° W, the SS and S1 parameters are 0.87 g and

0.40 g, respectively. To establish the ground-surface MCER spectrum, these bedrock spectral parameters are adjusted for soil site class using the short- and long-period site coefficients, Fa and Fv. The design-level response spectrum is calculated as two-thirds of the ground-surface MCER spectrum.

This project falls under Oregon Administrative Rule ORS 455.447 as a special occupancy structure and will require the completion of a site-specific seismic hazard study. The site-specific study is not part of our current scope of work and will be completed as part of the final design for the project during a later phase.

For preliminary design, based on the results of the recent explorations completed for this project, the soil profile at the site is representative of Site Class D, or a stiff-soil site. Due to the S1 acceleration parameter being greater than or equal to 0.2 g, Section 11.4.8 of ASCE 7-16 requires a site-specific ground-motion analysis unless the seismic response coefficient Cs is determined in accordance with Exception 2 of Section 11.4.8 of ASCE 7-16.

Assuming the seismic response coefficient Cs is determined in accordance with Exception 2 of Section 11.4.8 of ASCE 7-16, the published site coefficients Fa and Fv are 1.11 and 1.90, respectively, in accordance with Section 11.4 of ASCE 7-16. The design-level response spectrum is calculated as two-thirds of the ground-surface MCER spectrum. We recommend the project structural engineer evaluate the seismic parameters and structural period based on the requirements of Sections 11.4.8 and 12.8 of ASCE 7-16 for this preliminary phase of the project.

The recommended MCER- and design-level spectral response parameters for Site Class D conditions are provided in the table below.

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 6 September 5, 2023

Table 4-1: RECOMMENDED SEISMIC DESIGN PARAMETERS (2018 IBC/2022 OSSC)

Seismic Parameter Recommended Value

Site Class D

MCER 0.2-Sec Period Spectral Response Acceleration, SMS

1.00 g

MCER 1.0-Sec Period Spectral Response Acceleration, SM1

0.76 g*

Design-Level 0.2-Sec Period Spectral Response Acceleration, SDS

0.68 g

Design-Level 1.0-Sec Period Spectral Response Acceleration, SD1

0.51 g*

Notes:

Excep�on 2 of Sec�on 11.4.8 should be considered when evalua�ng base shear calcula�ons in Sec�on 12.8.

The SD1 value is intended only for calcula�ng Ts.

*This value is not intended to be used in design.

Based on our recent explorations, it is our opinion that the risk of liquefaction and/or significant cyclic softening of the soils below the groundwater level at the site is low during a code-based seismic event. Based on site topography, the risk of earthquake-induced slope instability and/or lateral spreading is low. Based on the proximity of the site to mapped active faults, the risk of damage from ground rupture, landslides, settlement, and subsidence at this site is low. The risk of tsunamis and/or seiches is absent.

4.3 Earthwork

4.3.1 General

The silt soils that mantle the site are fine grained and sensitive to moisture content. During wet conditions, the soils are easily disturbed, rutted, and weakened by construction activities. For this reason, we recommend that, if possible, all site preparation and earthwork be accomplished during the typical dry late spring through early fall months. It has been our experience that the moisture content of the upper few feet of fine-grained soils will decrease during extended warm, dry weather. However, the moisture content of the soil below this depth tends to remain relatively unchanged and well above the optimum moisture content for compaction. As a result, the contractor must use construction equipment and procedures that prevent disturbance and softening of the subgrade soils. To minimize disturbance of the moisture-sensitive, fine-grained soils, site grading can be completed using track-mounted hydraulic excavators. The excavation should be finished using a smooth-edged bucket to produce a firm, undisturbed surface.

It may also be necessary to construct granular haul roads and work pads concurrently with

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 7 September 5, 2023 excavation to minimize subgrade disturbance. If the subgrade is disturbed during construction, soft, disturbed soils should be overexcavated to firm soil and backfilled with structural fill.

4.3.2 Site Preparation

Demolition of existing structures and improvements within the limits of the new structures, retaining walls, areas of mass grading, and paved areas should include removal of underground utilities, foundations and walls, and associated unsuitable backfill.

Excavations made during demolition to remove existing improvements should be backfilled with structural fill. Any soil disturbed during the demolition should be removed and replaced with structural fill.

In unimproved areas, the ground surface within areas of mass grading or within the limits of proposed structures, retaining walls, or pavements should be stripped of vegetation, surface organics, and loose surface soils. Strippings will not be suitable for use as structural fill and should be disposed of off site or used in landscape areas. We anticipate stripping up to a depth of about 6 inches to 8 inches will likely be required in grass areas; however, deeper grubbing may be required to remove brush and tree roots.

Following stripping or excavation to subgrade level, the exposed subgrade should be evaluated by a qualified geotechnical engineer or engineering geologist. Proof rolling with a loaded dump truck may be part of this evaluation. Any soft areas or areas of unsuitable material disclosed by the evaluation should be overexcavated to firm material and backfilled with structural fill.

4.3.3 Granular Work Pads

If construction occurs during wet-ground conditions, granular work pads will be required to protect the underlying fine-grained subgrade and provide a firm working surface for construction activities. In our opinion, a 12-inch to 18-inch-thick granular work pad should be sufficient to prevent disturbance of the subgrade by lighter construction equipment and limited traffic by dump trucks. Haul roads and other high-density traffic areas, including the use of Gradalls and forklifts, will require a minimum of 18 inches to 24 inches of fragmental rock up to 6-inch nominal size to reduce the risk of subgrade deterioration.

The use of a woven geotextile fabric or geogrid over the subgrade may reduce the need for maintenance during construction. Haul roads can also be constructed by placing a thickened section of pavement base course and subsequently spreading and grading the excess CRB after earthwork is complete.

4.3.4 Prior Site Development

Due to previous development at the project site and the potential to encounter undocumented fill soils, it should be anticipated that some overexcavation of subgrade

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 8 September 5, 2023 may be required. In addition, site improvements within previously developed areas include the risk of encountering undocumented or poorly documented improvements and infrastructure. Although not encountered during the subsurface explorations completed at the site, the possibility does exist of encountering existing underground improvements.

4.3.5 Site Grading

Final grading across the project should provide for positive drainage of surface water away from exposed slopes to reduce the potential for erosion. Prior to placing pavement base course aggregate, the subgrade should be sloped to a minimum -0.5% slope to aid in drainage. Permanent cut and fill slopes should be no steeper than 2H:1V (Horizontal to Vertical) and should be protected with vegetation to reduce the risk of surface erosion due to rainfall.

4.4 Excavation and Shoring

4.4.1 General

We anticipate the maximum depth of excavations to establish the base of the swimming pool, footing subgrades, and site utilities will be up to about 15 feet. Excavations at the site will encounter silt soils overlying sand with variable amounts of silt, gravel, and cobbles. Due to the previous development at the site, it is likely to encounter undocumented fill soils in portions of the site. The method of excavation and the design of excavation support are the responsibilities of the contractor and are subject to applicable local, state, and federal regulations, including the current Occupational Safety and Health Administration (OSHA) excavation and trench safety standards. The means, methods, and sequencing of construction operations and site safety are also the responsibility of the contractor. The information provided below is for the use of our client and should not be interpreted to mean we are assuming responsibility for the contractor’s actions or site safety.

4.4.2 Groundwater Management

We anticipate the groundwater level will typically occur below the anticipated maximum excavation depth; however, perched groundwater may develop in the near-surface fine-grained soils that mantle the site during periods of heavy or prolonged rainfall.

Groundwater seepage, running-soil conditions, and unstable excavation sidewalls or excavation subgrades, if encountered during construction, will require dewatering of the excavation and sidewall support. The impact of these conditions can be reduced by completing excavations during the summer months, when groundwater levels are lowest.

We anticipate perched-groundwater inflow, if encountered, can generally be controlled by pumping from sumps. To facilitate dewatering, it will likely be necessary to overexcavate the base of the excavation to permit installation of a granular working blanket. We

GRI 6732-A – North Portland Aquatic Center Preliminary Geotechnical Investigation Page 9 September 5, 2023 estimate the required thickness of the granular working blanket will be on the order of 1 foot. The actual required depth of overexcavation will depend on the conditions exposed in the excavations and the effectiveness of the contractor’s dewatering efforts. The thickness of the granular blanket must be evaluated based on field observations during construction. We recommend the use of relatively clean, free-draining material, such as 2-to 4-inch-minus crushed rock, for this purpose. The use of a geotextile fabric over the excavation base will assist in subgrade stability and dewatering.

4.4.3 Temporary Excavations

The inclination of temporary excavation slopes will depend on groundwater conditions and variable soil conditions. In this regard, we anticipate temporary excavation slopes in native fine-grained soils can be cut at 1H:1V to a maximum depth of about 10 feet. We anticipate temporary excavations in the sand can be excavated to a short-term maximum inclination of about 1½H:1V. There should be no surcharge loading, stockpiles of soil, or other heavy building materials within a horizontal distance from the crest of the slope equal to the height of the slope. Flatter slopes may also be necessary if significant seepage conditions are encountered.