Addendum 1~7.pdf

Business Services Procurement and Contracting

1260 NW Waterhouse Rd Beaverton, OR 97006

(503) 356-4324

November 18, 2025

SOLICITATION ADDENDUM NO. 1

ITB 25-0014

Aloha High School Athletic Facility

THE FOLLOWING CHANGES/ADDITIONS TO THE ABOVE CITED SOLICITATION ARE ANNOUNCED:

This Addendum modifies the Invitation to Bid (ITB) document(s) only to the extent indicated herein. All other areas not changed or otherwise modified by this Addendum shall remain in full force and effect. This Addendum is hereby made an integral part of the ITB document. Bidder must be responsive to any requirements of this Addendum as if the requirements were set forth in the ITB. Failure to do so may result in Proposal rejection. See the ITB regarding requests for clarification or change and protests of this Addendum, and the deadlines for the foregoing.

This addendum is to be acknowledged in the space provided on the Bidder Certification form supplied in the solicitation document. Failure to acknowledge receipt of this addendum may cause to reject your Bid.

The closing date: December 18, 2025 at 2:00 PM Pacific Time

CLARIFICATION/REVISIONS:

*Specifications- Please see Revised Specification attached

QUESTION: A building fire alarm system is not required for the Batting Cage and Concessions/Restroom buildings as currently designed, and that Division 28 46 00 applies only if a triggering system (e.g., automatic sprinklers or a hood suppression system) is later added.

ANSWER: This is correct- for Group B low occupant loads, a building fire alarm system would not be required.

QUESTION: If monitoring is desired in the future (e.g., waterflow/tamper or hood supervisory/alarm), please confirm that a limited monitoring-only FA scope (small panel/module, dedicated circuit, and single path off-site monitoring if required by AHJ) is acceptable in lieu of a full occupant-notification system.

ANSWER: This would be acceptable.

QUESTION: If cooking equipment such as a deep fryer is included and requires a Type I hood with automatic suppression, please confirm whether the intent is for the suppression system to operate locally only, or to be monitored by a building fire alarm control unit. Our assumption is that local-only activation and audible alarm will satisfy code for this small Group B occupancy unless otherwise directed by AHJ.

ANSWER: No equipment requiring a hood will be utilized at these locations but if one is to be used in the future, local only activation would be acceptable.

QUESTION: Specification Section 13-34-19 for Metal Building Systems indicates in Section 2.1.A.1 that the only acceptable manufacturer is Nucor Building Systems and allows no substitutions in 2.1.B. Oregon Regional Statutes (ORS) do not allow for sole source procurement without prior approval (ORS 279B.075). Can you clarify if such approval was granted?

ANSWER: See the Revised specification attached.

QUESTION: Is there a Geo-tech report?

ANSWER: We have attached this report with this Addendum.

-END of Addendum

Elizabeth Smith Procurement & Contracting Beaverton School District

Prepared For:

E

Date: January 28, 2025

AKS Engineering & Forestry, LLC

12965 SW Herman Road, Suite 100

Tualatin, Oregon 97062

Report for Geotechnical

Engineering Design Services

Aloha High School Baseball/Softball Turf Fields

18550 SW Kinnaman Road

Aloha, Oregon

CGS Project: AKS-8-01

7662 SW Mohawk Street

(503) 616-9419 www.centralgeotech.com

AKS-8-01

January 28, 2025

AKS Engineering & Forestry, LLC

12965 SW Herman Road, Suite 100

Attention: Christopher Knight (knightc@aks-eng.com)

Subject: Report for Geotechnical Engineering Design Services

Aloha High School Baseball/Softball Turf Fields

18550 SW Kinnaman Road

Aloha, Oregon 97007

Central Geotechnical Services, LLC (CGS) is pleased to submit this report of geotechnical engineering services for the proposed improvements for the Aloha High School Baseball/Softball Turf Fields project located at 18550

SW Kinnaman Road in Aloha, Oregon. The report was prepared for conformance with the executed subconsultant agreement dated November 19, 2024. Please feel free to call our office with questions about this report.

Respectfully, Central Geotechnical Services, LLC

Krey D. Younger, P.E., G.E.

Principal

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 PURPOSE AND SCOPE OF WORK

3.0 SITE CONDITIONS

3.1 GEOLOGY

3.2 SURFACE CONDITIONS

3.3 SUBSURFACE CONDITIONS

3.3.1 Groundwater Conditions

4.0 INFILTRATION TESTING

4.1 SUITABILITY OF INFILTRATIONS SYSTEM

5.0 CONCLUSIONS

6.0 DESIGN RECOMMENDATIONS

6.1 SHALLOW FOUNDATION SUPPORT RECOMMENDATIONS

6.1.1 Shallow Foundation Subgrade Preparation

6.1.2 Spread Footings

6.1.3 Foundation Settlement

6.1.4 Shallow Foundation Lateral Resistance

6.1.5 Shallow Foundation Lateral Resistance

6.2 DRILLED SHAFT FOUNDATION RECOMMENDATIONS

6.2.1 Drilled Shaft Lateral Foundation Capacity

6.2.2 Quality Control

6.3 FLOOR SLABS

6.4 SEISMIC DESIGN

6.5 LIQUEFACTION POTENTIAL

6.6 RETAINING WALLS

6.6.1 Assumptions

6.6.2 Subgrade Preparation

6.6.3 Wall Design Parameters

6.6.4 Wall Drainage and Backfill

6.6.5 Settlement

6.7 TURF FIELD

6.8 PAVEMENT

6.8.1 Conventional AC Pavement

6.8.2 Porous Asphalt Concrete (PAC) Pavement

6.8.3 Cold Weather Paving Considerations

7.0 EARTHWORK RECOMMENDATIONS

7.1 SITE PREPARATIONS

7.2 SITE SUBGRADE PREPARATION AND EVALUATION

7.3 SUBGRADE PROTECTION AND WET WEATHER CONSIDERATIONS

7.4 DEWATERING

7.5 EXCAVATION

7.5.1 Drilled Shafts

7.6 DRAINAGE CONSIDERATIONS

7.6.1 Temporary

7.6.2 Surface

7.6.3 Turf Drainage

7.7 PERMANENT SLOPES

7.8 STRUCTURAL FILL AND BACKFILL

7.8.1 General

7.8.2 On-Site Soil

7.8.3 Imported Granular Material

7.8.4 Trench Backfill

7.8.5 Aggregate Base

7.8.6 Drain Rock Material

7.8.7 Fill Placement and Compaction

7.8.8 Soil Amendment with Cement

7.8.9 Asphalt Concrete Pavement (ACP)

7.8.10 Pervious Asphalt Concrete

7.8.11 Choker Aggregate

7.8.12 Storage Aggregate

7.8.13 Subgrade Geotextile

7.8.14 Drainage Geotextile

8.0 LIMITATIONS OF REPORT

9.0 SIGNATURES

REFERENCES

LIST OF FIGURES

• Figure 1. Vicinity Map

• Figure 2. Site Plan

APPENDICES

Appendix A. Field Explorations and Laboratory Testing

• Figure A-1. Explorations and Soil Classification Key

• Figures A-2 through A15. Logs of Explorations

January 28, 2025 | Page 1

1.0 INTRODUCTION

Central Geotechnical Services, LLC (CGS) is pleased to submit this geotechnical engineering report for the proposed improvements for the Aloha High School Baseball/Softball Turf Fields project located at 18550 SW

Kinnaman Road in Aloha, Oregon. The location of the site is shown in the Vicinity Map, Figure 1.

Based on information provided to us and discussions with AKS, we understand that the project includes construction of new turf fields for baseball, softball, a multi-use soccer field, and a pervious pavement section to the west of the baseball field. The site improvements will also include field lighting, new dugouts, and a new baseball backstop. It is our understanding the project may include a new batting cage as well as an expansion to the concessions stand.

Structural design loads were not provided at the time this report was prepared. However, we have assumed maximum column and wall loads will be on the order of 50 kips per column and 3 kips per lineal foot (klf) respectively, and that floor loads for slabs on grade will be 100 pounds per square foot (psf) or less. We have also assumed that maximum cuts and fills for general site grading (not including cuts for structures below grade) will be less than 4 feet.

2.0 PURPOSE AND SCOPE OF WORK

The purpose of our services was to evaluate soil and groundwater conditions as a basis for developing geotechnical engineering design criteria for the proposed turf field updates. Our scope of services was provided in general accordance with our revised proposal dated October 24, 2024, which included the following:

1. Reviewed information regarding subsurface soil and groundwater in the vicinity of the site, including reports in our files, selected geologic maps, and other geotechnical engineering-related information.

2. Coordinated and managed the field investigation, including public utility notification and scheduling of subcontractors and CGS’s field staff.

3. Explored subsurface conditions by drilling ten borings to depths between 5 and 31.5 feet below ground surface (bgs).

4. Completed three field infiltration tests.

5. Obtained samples at representative intervals from the explorations, observed groundwater conditions and maintain detailed logs in general accordance with ASTM International (ASTM) Standard Practices

Test Method D 2488.

6. Performed laboratory tests on selected soil samples obtained from the explorations to evaluate pertinent engineering characteristics.

7. Provided project-specific geotechnical engineering evaluation and design recommendations in this report that will address the following components:

a. A general description of site and area topography, geology, and subsurface conditions.

b. An opinion as to the adequacy of site soil conditions for the proposed site improvements from a geotechnical engineering standpoint.

c. Summarize the results of infiltration testing and discussion of suitability of on-site infiltration facilities based on subsurface conditions if necessary.

January 28, 2025 | Page 2

d. Recommendations for site preparation measures, including disposition of undocumented fill and unsuitable soils, and constraints for wet weather construction.

e. Recommendations for earthwork construction, including use of on-site and imported tructural fill and fill placement and compaction requirements.

f. Recommendations for light pole foundation design parameters.

g. Recommendations for baseball field backstop foundations.

h. Recommendations for shallow foundations for lightly loaded structures.

i. Recommendations for pervious pavement design section for access road west of the baseball field.

3.0 SITE CONDITIONS

3.1 GEOLOGY

The project site is located in the Tualatin Basin of the Puget Sound-Willamette Valley physiographic province, a tectonically active lowland located along the convergent Cascadia margin (Orr and Orr, 1999). The Tualatin

Basin is formed by a gentle syncline between the uplifted Coast Ranges to the west, the Chehalem Mountains to the south, and the Tualatin Mountains to the north and east. The Tualatin Mountains have been uplifted along northwesterly oriented faults, including the steeply dipping Portland Hills Fault located along the eastern flank of the mountains.

The near-surface geologic unit mapped at the site is the fine-grained facies of the Quaternary flood deposits

(Madin, 1990). The unit consists of unconsolidated silt and sand deposited by catastrophic floods associated with the sudden release of waters from glacial Lake Missoula during the late Pleistocene. Many dozens of these Missoula Floods occurred between about 15,500 and 12,500 years ago (and perhaps during earlier glaciations). Flood waters several hundred feet deep swept out of the Columbia Gorge and over the lowlands of the Portland area. Thickness of the flood deposits in the site vicinity is approximately 60 feet.

Underlying the Quaternary flood deposits are a thick accumulation of moderately to poorly lithified mudstone and sandstone mapped as the Sandy River Mudstone equivalent (Madin, 1990). These were deposited in a large delta where the ancient Columbia and Willamette Rivers converged probably during the middle Miocene to Pleistocene (approximately 6 to 1 million years ago). Thickness of the unit in the site vicinity is approximately

1,000 feet.

Basement rocks underlying the Sandy River Mudstone equivalent in the site vicinity consist of the Miocene

Columbia River Basalts (CRBs), emplaced approximately 17 to 6 million years ago in the Portland area (Madin, 1990). The CRBs are exposed in the Tualatin Basin in the highlands surrounding the valley and in a group of mountains south of the site, which include Cooper Mountain and Bull Mountain. The CRBs consist of thick flows of basalt erupted from fissures in eastern Oregon, Washington, and western Idaho that traveled down the ancient Columbia River Gorge to fill the lowland areas around Portland.

3.2 SURFACE CONDITIONS

The site is currently occupied by the existing baseball and softball fields, a soccer field, and associated parking.

A gravel access road, hardscapes, and landscaping are located south of the high school building. The project site is bounded by parking lots to the east, tennis courts to the north, and SW Madeline Street to the south.

The baseball and softball fields are bordered by sidewalks and associated hardscapes. The existing soccer field

January 28, 2025 | Page 3 is bordered by parking lots to the east, a paved access road to the north, the baseball field to the west, and the softball field to the south.

3.3 SUBSURFACE CONDITIONS

Subsurface conditions at the site were explored by drilling a total of ten geotechnical borings (B-1 through B-

10). Explorations were completed to final depths between 5 and 31.5 feet bgs. Approximate locations of the explorations completed at the site are presented in Figure 2. Logs of our explorations and associated laboratory testing completed for this study are presented in Appendix A.

Our explorations encountered an approximate 2-inch-thick root zone for borings B-1, B-2, B-4, and B-6 through

B-9. A pavement section of 2 inches of asphalt concrete over 4 inches of aggregate base was observed in boring

B-10, and approximately 2 to 3 inches of gravel fill was observed at the surface of borings B-3 and B-5. Fill was encountered in borings B-1, B-2, B-5, B-7, B-8, and B-9 to depths between 1 and 6 feet bgs. Fill generally consists of silt with vary amounts of sand, gravel, and organics.

Silt with varying amounts of sand underlies the surficial materials and fill at the site. Laboratory testing on select samples indicate moisture contents ranging from 21 to 51 percent at the time of our explorations and fines content of 93 to 99 percent. Atterberg limits test conducted on one select sample indicate a plasticity index of 11 and a liquid limit of 43.

3.3.1 Groundwater Conditions

Groundwater was observed within our explorations at depths of 1.5 feet to 5.5 feet bgs. The depth to groundwater may fluctuate in response to seasonal changes, prolonged rainfall, changes in surface topography, and other factors not observed in this study.

4.0 INFILTRATION TESTING

We conducted three on-site field infiltration tests at locations and depths below existing ground surface (bgs) as indicated by AKS. Approximate locations are shown in Figure 2. On-site testing was conducted in general accordance with the EPA Falling Head Percolation Test Procedure as stated in the Washington County On-Site

Stormwater Disposal System (OSDS) Design and Construction Minimum Guidelines and Requirements.

Our general procedure included excavating a 6-inch diameter hole using solid stem auger drilling techniques and inserting a 6-inch diameter polyvinyl chloride (PVC) pipe into the exploration and placing approximately 2 inches of clean gravel in the bottom of the pipe. The PVC pipe was then filled with clean water to approximately

1 foot above the gravel at the bottom of the drilled hole. The initial fill of water did not drain into the soil within 10 minutes, so the water level was maintained, and the soil was allowed to saturate for 4 hours.

Following the presoak period, water levels were measured, and the PVC pipes were refilled to approximately

12 inches above the soil at the end of each round of testing. The drop in water level was measured over a 1-to 3-hour period at each location. Field test results are summarized in Table 1 on the following page.

January 28, 2025 | Page 4

Table 1. Field Measured Infiltration Results

Infiltration Test

No.

Depth

(feet)

USCS1

Material

Type

Percent Fines Content

Field Measured

Infiltration Rate2

(in/hr)3

B-1 5 ML N/A N/A*

B-2 5 ML 98.3 N/A*

B-5 0.5 ML 95.7 0

Notes:

1. USCS = Unified Soil Classification System

2. Appropriate factors should be applied to the field-measured infiltration rate, based on the design methodology and specific system used. Measured rates may not reflect long-term sustainable rates area wide.

3. In/hr = inches per hour

Infiltration rates shown in Table 1 represent a field-measured infiltration rate. We were unable to conduct infiltration testing in explorations B-1 and B-2 due to the presence of shallow groundwater and standing water at the surface. Rates summarized for B-5 indicate 0 inches per hour (in/hr) as minimal to no infiltration (drop in water levels) were observed during the prescribed testing period. Field measurements are limited to the accuracy of equipment employed to conduct the test. Actual long-term infiltration rates of the on-site soils are likely greater than 0 in/hr if measured for time frames much longer than prescribed in the testing standards.

A field-measured rate of 0 in/hr generally indicates infiltration less than 1/8 inch per hour, which is about the limit of the field measuring equipment.

In addition, field-measured rates represent a relatively short-term infiltration rate, and factors of safety have not been applied for the type of infiltration system being considered, or for variability that may be present in the on-site soil. Even with higher tested values, appropriate correction factors should be applied by the project civil engineer to account for long-term infiltration parameters. From a geotechnical perspective, we recommend a factor of safety (correction factor) of at least 2 be applied to this type of field infiltration testing result to account for potential soil variability with depth and location within the area tested. In addition, the stormwater system design engineer should determine and apply appropriate remaining correction factor values, or factors of safety, to account for repeated wetting and drying that occurs in this area, degree of in-system filtration, frequency and type of system maintenance, vegetation, potential for siltation and bio-fouling, etc., as well as system design correction factors for overflow or redundancy, and base and facility size.

The actual depths, lateral extent and estimated infiltration rates can vary from the values presented above.

Field testing/confirmation during construction is often required in large or long systems or other situations where soil conditions may vary within the area where the system is constructed. The results of this field testing might necessitate that the infiltration locations be modified to achieve the design infiltration rate.

The infiltration flow rate of a focused stormwater system typically diminishes over time as suspended solids and precipitates in the stormwater slowly clog the void spaces between the soil particles or cake on the infiltration surface. The serviceable life of a stormwater system can be extended by pre-filtering or with on-going accessible maintenance. Eventually, most systems will fail and will need to be replaced or have media regenerated or replaced.

We recommend that infiltration systems include an overflow that is connected to a suitable discharge point.

Also, infiltration systems can cause localized high groundwater levels and should not be located near basement

January 28, 2025 | Page 5 walls, retaining walls, or other embedded structures unless these are specifically designed to account for the resulting hydrostatic pressure. Infiltration locations should not be located on sloping ground, unless it is approved by a geotechnical engineer, and should not be infiltrated at a location that allows for flow to travel laterally toward a slope face, such as a mounded water condition or too close to a slope face.

4.1 SUITABILITY OF INFILTRATIONS SYSTEM

Successful design and implementation of stormwater infiltration systems and whether a system is suitable for development depends on several site-specific factors. Stormwater infiltration systems are generally best suited for sites having sandy or gravelly soil with saturated hydraulic conductivities greater than 2 in/hr. Sites with silty or clayey soil, are generally not well- suited for long-term stormwater infiltration or as a sole method of stormwater infiltration. Soils that have fine-grained matrices are susceptible to volumetric change and softening during wetting and drying cycles. Fine-grained soils also have large variations in the magnitude of infiltration rates because of bedding and stratification that occurs during alluvial deposition and often have thin layers of less permeable or impermeable soil within a larger layer.

Local groundwater conditions also significantly affect the capacity to infiltrate from a stormwater system. Sites with shallow groundwater can result in groundwater mounding. A hydraulic gradient that reaches the level of water in the soil immediately drops to zero and local groundwater will rise and mound and the infiltration rate slows dramatically, resulting in overflows or system flooding (failure). Groundwater mounding can also negatively impact structures, slopes or other areas adjacent to the stormwater infiltration facility. Typically, we do not recommend using infiltration systems where groundwater is less than 10 feet below the bottom of the proposed system unless the host soil is very permeable and consistently graded and will not cause mounding.

Some jurisdictions require a minimum of 5 or 10 feet between high groundwater conditions and the bottom of proposed facilities. Depending on the size of the project, adjacent features such as streams that can source water to a system instead of allowing it to drain and on-site soil infiltration capacities, there may be conditions where even a 10-foot separation between the level of groundwater and the base of the infiltration system may not be sufficient.

Considering the potential for shallow groundwater and hydraulically restricting soil/rock layers, on-site infiltration will likely be minimal during wet times of the year as a function of separation between bottom of infiltration facilities and groundwater and/or hydraulically restricting layers. In such a case infiltration may cause mounding of groundwater if areas of perched water are present in the area. We do not recommend stormwater infiltration be used as the exclusive method of stormwater management and recommend an overflow be a part of system design.

5.0 CONCLUSIONS

Based on our explorations, testing, and analyses, it is our opinion that the site is suitable for the proposed project from a geotechnical standpoint, provided the recommendations in this report are incorporated into the project design and implemented during construction. We offer the following conclusions regarding geotechnical engineering design and construction at the site.

• The near surface soil is sensitive to disturbance when at a moisture content that is above optimum. As discussed in the report, the subgrade should be protected from disturbance and damage by construction traffic. Proper subgrade protection during earthwork will be essential for the integrity of the turf field.

Cement amendment of the subgrade should be considered.

• Synthetic turf fields are typically designed with extensive subsurface drainage that requires a network of drainage pipes and relatively clean aggregate base material. Careful planning and deliberate construction methods specific to these types of fields should be employed by contractors with experience in

January 28, 2025 | Page 6 construction of synthetic turf fields. Typically, the layer underlying the synthetic turf is not designed to support heavy construction traffic unless the drainage layer thickness is overbuilt for that purpose.

• Infiltration rates of zero inches per hour were observed on site (very low rates not registered by the equipment used over the testing period). Based on the shallow groundwater and soil conditions encountered, we do not recommend on-site stormwater infiltration as a sole method of stormwater disposal. Minimal to no infiltration into the native soils should also be considered as a part of drainage design of the proposed synthetic turf field.

• New field lighting, backstops, and batting cage net poles may require drilled shaft foundations.

6.0 DESIGN RECOMMENDATIONS

6.1 SHALLOW FOUNDATION SUPPORT RECOMMENDATIONS

Based on the results of our explorations, and assumed building loads, the proposed buildings can be supported on conventional shallow footings bearing on firm, undisturbed native soil or structural fill placed over firm, undisturbed native soil. Continuous wall and isolated spread footings should be at least 16 and 20 inches wide, respectively. The bottom of exterior column or continuous footings should be at least 18 inches below the adjacent exterior grade. The bottom of the interior footings should be established at least 12 inches below the base of the slab. Foundations should not be established over the existing undocumented fill or on soft soil.

Grading plans were not available at the time of this report.

6.1.1 Shallow Foundation Subgrade Preparation

The subgrades beneath proposed structural elements should be prepared as described below and in the

“earthworks” section of this report. We recommend loose or disturbed soils resulting from foundation excavation be removed before placing reinforcing steel and concrete. Foundation bearing surfaces should not be exposed to standing water. If water infiltrates and pools in the excavation, the water, along with any disturbed soil, should be removed before placing reinforcing steel and concrete. A thin gravel layer consisting of Aggregate Base or Aggregate Subbase material can be placed at the base of foundation excavations to help protect the subgrade from weather and light foot traffic. The layer thickness for the gravel layer should be determined at the time of construction but is typically 3 to 4 inches. The gravel layer should be compacted as described in the “Fill Placement and Compaction” section.

We recommend CGS observe all foundation subgrades before placing concrete forms and reinforcing steel to determine that bearing surfaces have been adequately prepared and the soil conditions are consistent with those observed during our explorations.

6.1.2 Spread Footings

We recommend conventional footings be proportioned using a maximum allowable bearing pressure of 2,000 psf if supported on firm native soils or on structural fill placed over firm native soils. This bearing pressure applies to the total of dead and long-term live loads and may be increased by one-third when considering earthquake or wind loads. This is a net bearing pressure. The weight of the footing and overlying backfill can be ignored in calculating footing sizes.

6.1.3 Foundation Settlement

Foundations designed and constructed as recommended are expected to experience settlements of less than

1 inch. Differential settlements of up to one half of the total settlement magnitude can be expected between adjacent footings supporting comparable loads.

January 28, 2025 | Page 7

6.1.4 Shallow Foundation Lateral Resistance

Lateral loads can be resisted by a combination of friction between the footing and the supporting soil, and by the passive lateral resistance of the soil surrounding the embedded portions of the footings. A coefficient of friction between the concrete and soil of 0.35 and a passive lateral resistance corresponding to an equivalent fluid density of 250 pcf may be used for design. These values are appropriate for foundation elements that are poured directly against the native soils or surrounded by compacted structural fill.

The passive earth pressure and friction components may be combined, provided the passive component does not exceed two-thirds of the total.

The passive earth pressure value is based on the assumptions that the adjacent grade is level and static groundwater remains below the base of the footing throughout the year. The top 1 foot of soil should be neglected when calculating passive lateral earth pressures unless the adjacent area is covered with pavement.

The lateral resistance values do not include safety factors.

6.1.5 Shallow Foundation Lateral Resistance

Lateral loads can be resisted by a combination of friction between the footing and the supporting soil, and by the passive lateral resistance of the soil surrounding the embedded portions of the footings. A coefficient of friction between the concrete and soil of 0.35 and a passive lateral resistance corresponding to an equivalent fluid density of 250 pcf may be used for design. These values are appropriate for foundation elements that are poured directly against the native soils or surrounded by compacted structural fill.

6.2 DRILLED SHAFT FOUNDATION RECOMMENDATIONS

New field lighting, backstops, and batting cage net poles may require a drilled shaft foundation. Drilled shaft support has the advantage of large moment transfer capacity as well as extending to depths where firm support is available.

6.2.1 Drilled Shaft Lateral Foundation Capacity

Drilled shaft foundations embedded at least 3 feet bgs can be designed for an allowable bearing capacity of

2,000 psf. Embedment depth for shaft foundations is typically controlled by lateral resistance capacity of the surrounding soil. Design should be based on allowable deflection at the top of the shaft as determined by the design engineer. A computer program, such as Ensoft’s LPILE, can be used to calculate the lateral capacity of drilled shaft foundations. LPILE uses lateral soil reaction (p) and lateral deflection (y) curves generalized from field load tests and soil input properties to approximate lateral pile deflections and moments. Recommended soil parameters for use by the LPILE program are presented in Table 2.

Table 2. Recommended LPILE Soil Parameters

Depth Below

Existing Grade

(ft)

Effective Unit

Weight (pcf)(1)

Cohesion, C

(psf) (2) Soil Modulus K (pci) (3)

Strain Value, Ɛ50 Soil Model

0 – 30 53 150 100 0.007

Silt

(Cemented

C-phi)

1) PCF = Pounds per cubic foot

2) PSF = Pounds per square foot

3) PCI = Pounds per cubic inch

January 28, 2025 | Page 8

6.2.2 Quality Control

Quality of shaft construction will be critical to provide acceptable settlement behavior. At a minimum, we recommend the following quality control measures:

• The hole bottom should be thoroughly cleaned as required by OSSC 00512.43 (Drilled Shaft

Excavation).

• A qualified technician should be present during construction to verify subsurface conditions are as interpreted and the general design intentions are met during construction.

6.3 FLOOR SLABS

Satisfactory subgrade support for floor slabs on grade supporting the planned 100 psf floor loads can be obtained provided the floor slab subgrade is described in the “Earthwork Recommendations” section of this report. Slabs should be reinforced according to their proposed use and per the structural engineer’s recommendations. Subgrade support for concrete slabs can be obtained from the firm native soils underlying the topsoil or on structural fill placed over firm native soils.

We recommend that on-grade slabs be underlain by a minimum 6-inch-thickness of aggregate base in order to provide the structural design support for subgrade reaction as described below and to act as a capillary break material to reduce the potential for moisture migration into the slab. The aggregate base section should be placed as recommended in the “Fill Placement and Compaction” section of this report.

If dry on grade slabs are required, for example at interior spaces where adhesives are used to anchor carpet or tile to the slab, a waterproof liner may be placed as a vapor barrier below the slab. The vapor barrier should be selected by the structural engineer and should be accounted for in the design floor section and mix design selection for the concrete, to accommodate the effect of the vapor barrier on concrete slab curing.

Load-bearing concrete slabs prepared as recommended should be designed assuming a modulus of subgrade reaction (k) of 150 psi per inch. This value is for a 1-foot by 1-foot square plate. The coefficient of subgrade reaction for a foundation varies based on its minimum width according to the following equation:

ks=ks1

B+1

2B

Where ks is the coefficient of subgrade reaction, ks1 is the coefficient of subgrade reaction for a 1-ft by 1-ft plate, and B is the minimum width or lateral dimension of the mat.

If dry on-grade slabs are required, for example at interior spaces where adhesives are used to anchor carpet or tile to the slab, a waterproof liner may be placed as a vapor barrier below the slab. The vapor retarder should be selected by the structural engineer and should be accounted for in the design floor section and mix design selection for the concrete, to accommodate the effect of the vapor barrier on concrete slab curing.

We estimate that concrete slabs constructed as recommended will settle less than ½ inch. Floor slab subgrades should be evaluated according to the “Subgrade Evaluation” section of this report.

6.4 SEISMIC DESIGN

Parameters provided on Table 4 are based on the conditions encountered during our subsurface exploration program and the procedure and requirements outlined in the 2018 IBC. Per American Society of Civil Engineers

(ASCE) 7-16 Section 11.4.8, a site-specific response analysis is required for site class F sites, and a ground motion hazard analysis or site-specific response analysis is required to determine the design ground motions for structures on Site Class D and E sites with S1 greater than or equal to 0.2g.

January 28, 2025 | Page 9

For this project, the site is classified as site class D; therefore, the provisions of 11.4.8 are applicable.

Alternatively, the parameters listed in Table 3 may be used to determine the design ground motions if the exceptions provided in ASCE 7-16 Supplement 3 are met and the fundamental period of the structure is less than 0.5 seconds. Exception 2 states “Structures on Site Class D 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 < 1.5 TS or Eq. (12.8-4) for T > TL “. If it is desirable to avoid these exceptions, a ground motion hazard analysis or site response analysis which is outside of the scope of services for this report, would need to be completed to determine the design seismic parameters for the site.

Table 3. Mapped ASCE 7-16 Seismic design parameters

Parameter Recommended Value1

Site Class D

Mapped Spectral Response Acceleration at Short Period (SS) 0.875 g

Mapped Spectral Response Acceleration at 1 Second Period (S1) 0.41 g

Site Modified Peak Ground Acceleration (PGAM) 0.481 g

Site Amplification Factor at 0.2 second period (Fa) 1.150

Site Amplification Factor at 1.0 second period (Fv) 1.89

Design Spectral Acceleration at 0.2 second period (SDS) 0.671 g

Design Spectral Acceleration at 1.0 second period (SD1) 0.517 g

Note:

1 Parameters developed based on Latitude 45.484635° and Longitude -122.869022 °using the ATC Hazards online tool.

6.5 LIQUEFACTION POTENTIAL

Liquefaction is a phenomenon caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles to near zero. The excessive buildup of pore water pressure results in the sudden loss of shear strength in a soil. Granular soil, which relies on interparticle friction for strength, is susceptible to liquefaction until the excess pore pressures can dissipate. Sand boils and flows observed at the ground surface after an earthquake are the result of excess pore pressures dissipating upwards, carrying soil particles with the draining water. In general, loose, saturated sand soil with low silt and clay contents is the most susceptible to liquefaction. Low plasticity, silty sand may be moderately susceptible to liquefaction under relatively higher levels of ground shaking.

Based on the subsurface conditions encountered in the explorations and the laboratory testing results, it is our opinion that there is a low risk of seismic-induced liquefaction at the site during the design-level earthquake.

6.6 RETAINING WALLS

6.6.1 Assumptions

Our retaining wall design recommendations are based on the following assumptions: (1) walls consist of conventional, cantilevered retaining walls, (2) walls are less than 8 feet in height, (3) the backfill is drained and consists of imported granular materials, and (4) the backfill has a finish slope flatter than 4H:1V. Re-evaluation of our recommendations will be required if the retaining wall design criteria for the project varies from these assumptions.

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6.6.2 Subgrade Preparation

Wall footings should bear on a minimum 12-inch-thick layer of imported granular material underlain by firm, undisturbed native soil and be prepared as listed in the “Site Subgrade Preparation and Evaluation” section of this report. The imported granular material should be fairly well graded between coarse and fine material, have less than 6 percent by dry weight passing the U.S. Standard 200 sieve, should have at least two mechanically fractured faces, and be compacted to 95% of maximum dry density as obtained from ASTM

D1557.

6.6.3 Wall Design Parameters

Wall footings prepared as recommended should be sized based on an allowable bearing pressure of 2,500 psf.

The weight of the footing and overlying backfill can be ignored in calculating footing sizes.

For unrestrained retaining walls, an active equivalent fluid pressure of 35 pcf should be used for design. Where retaining walls are restrained from rotation (such as basement walls), an at-rest equivalent fluid pressure of 55 pcf should be used for design. A superimposed seismic lateral force should be calculated based on a dynamic force of 7H2 pounds per lineal foot of wall, where H is the height of the wall in feet, and applied as a distributed load with the centroid located at a distance of 0.6H from the base of the wall.

If surcharges (e.g., structure foundations, concrete slabs, vehicles, steep slopes, terraced walls, etc.) are located within a horizontal distance from the back of a wall equal to the height of the wall, additional pressures will need to be accounted for in the wall design. Our office should be contacted for appropriate wall surcharges based on the actual magnitude and configuration of the applied loads. The base of the wall footing should extend a minimum of 12 inches below the lowest adjacent finish grade.

Lateral loads on the proposed structures can be resisted by a combination of sliding resistance on the base of footings and passive earth pressure on the sides of footings. We recommend a coefficient of friction of 0.35 for footings bearing on undisturbed, native silt, and 0.45 for footings bearing on granular engineered structural fill.

Passive earth pressures on the sides of buried spread footings may be calculated using an equivalent fluid pressure of 300 pcf per foot of embedment. For this value, backfill against the footing should be compacted to at least 92% of the maximum dry density as obtained from ASTM D1557. The upper foot of embedment should be neglected unless protected by pavement or concrete slabs on grade.

6.6.4 Wall Drainage and Backfill

The above design parameters have been provided assuming back-of-wall drains will be installed to prevent buildup of hydrostatic pressures behind all walls. If a drainage system is not installed, CGS should be contacted for revised design forces.

Backfill material placed behind retaining walls and extending a minimum horizontal distance of H, where H is the height of the retaining wall, should consist of select granular wall backfill meeting the requirements described in the “Structural Fill and Backfill” section. All wall backfill should be compacted to at least 92% of the maximum dry density as obtained from ASTM D1557. Wall backfill in the top 2 feet should be compacted to at least 95% of the maximum dry density when under structural areas such as footings, concrete slabs, pavement.

Perforated collector pipes should be placed at the base of the granular backfill behind the walls. The pipe should be embedded in a minimum 1-foot-wide zone of angular drain rock and the drain rock should be wrapped in a drainage geotextile fabric. The collector pipes should discharge at an appropriate location away from the base of the wall. The discharge pipe should not be tied directly into stormwater drain systems, unless measures are taken to prevent backflow into the drainage system of the wall.

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6.6.5 Settlement

Settlement of up to 1 percent of the wall height commonly occurs immediately adjacent to the wall as the wall rotates and develops active lateral earth pressures. Consequently, we recommend that construction of flatwork adjacent to retaining walls be postponed at least four weeks after backfilling of the wall, unless survey data indicates that settlement is complete prior to that time.

6.7 TURF FIELD

We anticipate that the playing fields will consist of locally commercially available synthetic turf material manufactured specifically for use on athletic fields. The turf should be installed in accordance with the manufacturer's recommendations over a drainage layer capable of supporting intended uses. Subgrade should be prepared in accordance with the “Earthwork Recommendations” section of this report. The greatest demand on the subgrade will be during construction, when earthwork equipment performs grading work.

Subgrade protection will be critical to the long-term performance of the field, especially during the wet season.

Cement amendment of the subgrade should be strongly considered for subgrade protection during construction. Not only will cement amended subgrade provide protection during original construction, it will also provide subgrade protection if the turf needs to be replaced in the future.

It is possible that groundwater could rise to near ground surface during periods of extreme wet weather. We recommend that a subsurface drainage system be installed below the field as discussed in the “Drainage

Considerations” section of this report.

6.8 PAVEMENT

New pavement is proposed for an access road west of the baseball field. The pavement section may be either conventional (AC over Aggregate Base) or pervious asphalt pavement. Pavement sections should be installed on native subgrade or engineered fills prepared in conformance with the “Earthwork Recommendations” and

“Structural Fill” sections, with the understanding that for pervious pavement considerations subgrade for engineered silt fill typically has lower permeability than native subgrade. All thicknesses are intended to be the minimum acceptable. Design of the recommended pavement section assumes that construction will be completed during an extended period of dry weather. Wet weather construction could require an increased thickness of aggregate base.

Construction traffic should be limited to haul roads. Construction traffic should not be allowed on new pavement. If construction traffic is to be allowed on newly constructed pavement, an allowance for this additional traffic will need to be made in the design pavement section. The pavement thicknesses do not account for construction traffic, and haul roads and staging areas should be used.

Pavement material recommendations are provided in the “Structural Fill and Backfill” section of this report.

6.8.1 Conventional AC Pavement

The recommended pavement sections assume that final improvements surrounding the pavement will be designed and constructed such that stormwater or excess irrigation water from landscape areas does not infiltrate below the pavement section. Our conventional pavement recommendations are based on the following assumptions:

• Resilient moduli of 4,500 psi and 20,000 psi were assumed for the subgrade and aggregate base, respectively.

• The design manual provided for the project specifies pavement recommendations based on a design life of 20 years.

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• Initial and terminal serviceability indices of 4.2 and 2.5, respectively.

• Reliability of 85 percent and standard deviation of 0.45.

• Traffic consists of light passenger carts and personal vehicles with occasional, small delivery trucks.

We recommend the following conventional pavement section based on the above information. If traffic is to include larger, more frequent trucks, our recommendations should be revised.

Conventional Pavement Section (2.5 inches of AC over 8 inches of aggregate base)

• 2.5 inches of ½-inch, Level 2, dense ACP, PG 64-22 (surface course)

• 8.0 inches of aggregate base

• Subgrade stabilization (if required)

• Subgrade Geotextile

6.8.2 Porous Asphalt Concrete (PAC) Pavement

The porous pavement structure includes a layer of PAC over a base section of choker aggregate over open graded storage aggregate. If subgrade infiltration is desired, the subgrade should be cut from the edges and not be trafficked by construction equipment. The subgrade grades should be designed to allow adequate storage of storm infiltration. The amount of storage aggregate listed below is the minimum for structural design; however, the total storage aggregate thickness should be controlled by hydraulic storm requirements.

We recommend the following porous asphalt pavement section:

Porous Pavement Section (3.0 inches of PAC, over 2inches of choker aggregate, over 10 inches of storage aggregate)

• 3.0 inches of ½-inch PAC, PG 70-22ER

• 2.0 inches of chocker aggregate

• 10.0 inches of storage aggregate

• Drainage Geotextile

6.8.3 Cold Weather Paving Considerations

In general, AC paving is not recommended during cold weather (surface temperature less than 40 degrees

Fahrenheit). Compacting under these conditions can result in low compaction and premature pavement distress.

Each AC Mix design has a recommended compaction temperature range that is specific for the particular AC binder used. In colder temperatures, it is more difficult to maintain the temperature of the AC mix as it can lose heat while stored in the delivery truck, as it is placed, and in the time between placement and compaction.

In Oregon, the surface temperature during paving should be at least 40 degrees Fahrenheit for lift thickness greater than 2.5 inches and at least 50 degrees Fahrenheit for lift thicknesses between 2 and 2.5 inches.

If paving activities must take place during cold weather construction as defined above, the project team should be consulted and a site meeting should be held to discuss ways to lessen low compaction risks.

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7.0 EARTHWORK RECOMMENDATIONS

7.1 SITE PREPARATIONS

In general, initial site preparation and primary earthwork operations will include stripping and grubbing of upper organics, areas of light logging, and brush clearing to create level working surfaces, excavating and filling for roads pavements, foundations, and utilities, demolition of existing structures, recompacting (dry weather) or replacing (wet weather) unsuitable soils in areas of the site that are to receive fill, fine-grading to establish final grades, or structural improvements.

All existing utilities in the proposed earthwork construction areas should be identified prior to excavation. Live utility lines beneath proposed structures should be completely removed or filled with grout to reduce potential settlement of new structures. Soft or loose soil encountered in utility line excavations should be removed and replaced with structural fill where it is located within structural areas.

Debris materials generated during demolition of existing improvements or relocation of utilities should be transported off site for disposal. Existing voids and new depressions created during site preparation, and resulting from removal of existing utilities, or other subsurface elements, should be cleaned of loose soil or debris down to firm soil and backfilled with compacted structural fill. Disturbance to a greater depth should be expected if site preparation and earthwork are conducted during a period of wet weather.

7.2 SITE SUBGRADE PREPARATION AND EVALUATION

Upon completion of site preparation activities, exposed subgrades should be proof-rolled with a fully loaded dump truck or similar heavy rubber-tired construction equipment where space allows to identify soft, loose or unsuitable areas. Probing may be used for evaluating smaller areas or where proof-rolling is not practical.

Proof-rolling and probing should be conducted prior to placing fill and should be performed by a representative of CGS who will evaluate the suitability of the subgrade and identify areas of yielding that are indicative of soft or loose soil. We anticipate that there will be areas where soft or otherwise unsuitable soil is identified during subgrade evaluation. Unsuitable soil should be replaced by imported granular material or should be improved by scarifying and compacting the material in accordance with the “Structural Fill and Backfill” section.

As discussed in the Subgrade Protection and Wet Weather Considerations of this report, the fine-grained soil at the surface can be sensitive to small changes in moisture content and will be difficult, or not possible, to compact adequately during wet weather. While tilling and compacting the subgrade is the economical method for subgrade improvement, it will likely only be possible during extended dry periods and following moisture-conditioning of the soil.

During wet weather, or when the exposed subgrade is wet or unsuitable for proof-rolling, the prepared subgrade should be evaluated by observing excavation activity and probing with a steel foundation probe.

Observations, probing, and compaction testing should be performed by a member of our staff. Wet soil that has been disturbed due to site preparation activities or soft or loose zones identified during probing should be removed and replaced with compacted structural fill.

7.3 SUBGRADE PROTECTION AND WET WEATHER CONSIDERATIONS

Upper site soils are highly susceptible to moisture. If wet weather construction practices are necessary based on conditions observed at the time…